Polyiodides of amino acids. L-Proline triiodides

Polyiodides of amino acids. L-Proline triiodides | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Polyiodides of amino acids. L-Proline triiodides Gerald Giester, Vahram V. Ghazaryan, Ashkhen L. Zatikyan, Aram M. Petrosyan This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3869782/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 09 Feb, 2024 Read the published version in Structural Chemistry → Version 1 posted 7 You are reading this latest preprint version Abstract Two new salts of l -proline containing triiodide anions were obtained and investigated: ( l -ProH··· l -Pro)(I 3 ) (I) and [( l -ProH) 3 ( l -Pro)](I 3 ) 3 (II). Both compounds crystallize in the polar monoclinic space group P 2 1 . Crystal structure determinations showed that (I) contains a dimeric cation formed by an O-H···O hydrogen bond with an O···O distance of 2.458(4) Å, while (II) features a peculiar tetrameric cation [ l -ProH···( l -Pro-H- l -Pro)··· l -ProH], where ( l -Pro-H- l -Pro) is a pseudocentrosymmetric dimer with a very short hydrogen bond with an O···O distance of 2.427 Å. Infrared spectra of both crystals were registered and interpreted based on their structures. Electronic band structures were determined by quantum chemical calculations. The CASTEP code was used to calculate the band structures, total and partial density of states (TDOS, PDOS). Bandgaps were also measured by the diffuse reflectance method. Salts of l-proline Polyiodides Crystal structure Dimeric cations Electronic structure Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Introduction The study of polyiodides is of great scientific and practical interest [ 1 , 2 ]. The incorporation of iodine (I 2 ) molecules and triiodide (I 3 − ) anions into the structure of halogenobismuthate salts allows for a significant narrowing of the bandgap [ 3 , 4 ]. Recently, we have begun searching for new amino acid salts with halogenobismuthate anions as potential materials for solar energy conversion [ 5 ]. Amino acid salts containing polyiodide anions and iodine molecules can serve as starting materials and are also interesting in their own right. Previously, two salts of amino acids with a triiodide anion were obtained: ( l -AlaH··· l -Ala)(I 3 ) [ 6 ] and (GlyH)(I 3 ) [ 7 ]. Based on these findings, the search for new amino acid salts containing polyiodide anions and iodine molecules started [ 8 ]. Recently a paper was published on (BetH)(I 3 ) which contains a centrosymmetric dimeric (BetH···BetH) cation of the (A + ···A + ) type [ 9 ]. The present paper describes two salts of l -proline. One of them is an analog of ( l -AlaH··· l -Ala)(I 3 ) [ 6 ]: ( l -ProH··· l -Pro)(I 3 ) ( I ). The corresponding iodide ( l -ProH··· l -Pro)(I) has been previously studied in [ 10 ]. The second one, [( l -ProH) 3 ( l -Pro)](I 3 ) 3 ( II ), has a complicated composition with an unusual structure containing a peculiar tetrameric cation [ l -ProH···( l -Pro-H- l -Pro)··· l -ProH]. Synthesis, crystal growth, single-crystal structure determination, infrared spectra, and bandgaps measured by the diffuse reflectance method and supplemented by quantum chemical calculations, are presented and discussed. Experimental Materials and synthesis As initial reagents we used l -proline (98.5–101.0%, Ph. Eur., USP, PanReac AppliChem ITW reagents), hydriodic acid (54.6% w/w, distilled, Vekton JSC), crystalline iodine (“high purity”, Reakhim), acetonitrile (Ph. Eur., for UHPLC, PanReac AppliChem ITW reagents), and medical ethanol (95%, from a commercial source). Crystals were obtained at room temperature by slow evaporation of the appropriate solutions. Crystals of ( I ) were formed from a mixture containing l -proline, HI and I 2 in a stoichiometric 2:1:1 M-ratio taking 1.000 g of l -proline, 1.59 ml of hydriodic acid, and 2.849 g of iodine, and then adding 2 ml of ethanol. Trying to obtain ( l -ProH)(I 3 ) from a 1:1:1 M-ratio (1.000 g of l -proline, 1.233 ml of hydriodic acid and 2.205 g of iodine) with 2 ml of acetonitrile, the crystals of ( II ) were formed. Subsequently, crystals of ( II ) were also synthesized from a solution with a stoichiometric 4:3:3 M-ratio of components, i.e., taking 1.000 g of l -proline, 0.92 ml of hydriodic acid and 1.653 g of iodine, and adding 2 ml of ethanol. Crystals formed within two weeks. Infrared spectra Attenuated total reflection Fourier-transform infrared spectra (ATR-FTIR) were recorded on an Agilent Cary 630 spectrometer using a germanium (Ge) ATR sampling module (Ge crystal, Happ-Genzel apodization, ATR distortion corrected, 64 scans, 4 cm –1 resolution). Structure determination Appropriate single crystals were manually selected for homogeneous extinction, mounted on MiTeGen loops with silicone grease and used for single crystal X-ray data collections on a Bruker APEX II diffractometer equipped with a CCD area detector, an Incoatec Microfocus Source IµS (30 W, multilayer mirror, Mo-K α ) and an Oxford Cryosystems Cryostream 800 Plus LT device. Data were collected at 200 K up to 65° 2θ full sphere by combining several runs of frames recorded at crystal-detector distances of 40 mm and 2° ( I ) and 1.5° ( II ) scan widths. Further data processing was done with the Bruker APEX4 software suite [ 11 ]. The absorption was corrected by evaluation of multi-scans. The structures were solved by direct methods [ 12 ]. Subsequent difference Fourier syntheses and least-squares refinements yielded the positions of the remaining atoms using the SHELX software [ 13 ] implemented in the ShelXle GUI tool [ 14 ]. Non-hydrogen atoms were refined with independent anisotropic displacement parameters. Structural data are available as Supplementary Material and have been deposited as CIF to the Cambridge Crystallographic Data Base (CCDC Nos. 2281225 ( II ) and 2281226 ( I )). They can be downloaded free of charge from the following site: http://www.ccdc.cam.ac.uk . Table 1 Crystallographic data and details of the structure refinement for ( l -ProH··· l -Pro)(I 3 ) ( I ) and [( l -ProH) 3 ( l -Pro)](I 3 ) 3 ( II ). Crystal (I) (II) Empirical Formula C 10 H 19 I 3 N 2 O 4 C 20 H 39 I 9 N 4 O 8 Formula mass 611.97 1605.65 Crystal system Monoclinic Monoclinic Space group P 2 1 P 2 1 a (Å) 9.6021(7) 14.4830(12) b (Å) 9.2481(7) 7.2365(6) c (Å) 10.2565(8) 18.8372(17) β (°) 100.163(2) 90.681(3) V (Å 3 ) 896.50(12) 1974.1(3) Z 2 2 Crystal size (mm 3 ) 0.300×0.125×0.100 0.200×0.100×0.075 ρ calc .(g cm −3 ) 2.267 2.701 Temperature (K) 200(2) 200(2) 2θ max (°) 66.366 66.462 µ (mm –1 ) 5.240 7.108 F (000) 568 1456 Absorption-correction Multi-scan Multi-scan Index ranges (hkl) ±14, ±14, ±15 ±22, ±11, + 29/-28 Reflections collected 33861 83596 Independent reflections ( R int ) 6857 (0.0317) 15093 (0.0331) Data with F o > 2 σ ( F o ) 5793 12980 Flack parameter [ 15 ] 0.000(10) 0.004(10) Parameters refined/restrained 175/1 379/1 R 1 a / w R 2 b ( I > 2 σ ( I )) 0.0260/0.0492 0.0240/0.0414 R 1 a / w R 2 b (for all F o 2 ) 0.0362/0.0529 0.0336/0.0445 Δρ fin (max/min) [e Å –3 ] 0.73/-0.82 0.92/-0.65 Method of electronic structure calculation The calculations have been carried out using the density functional theory (DFT) based CASTEP (Cambridge Serial Total Energy Package) software, along with the generalized gradient approximation (GGA) using the Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional [ 16 – 18 ]. Optical measurements UV-Vis diffuse reflectance data were collected using an Agilent Cary 60 UV-Vis spectrophotometer equipped with a Remote Diffuse Reflectance Accessory (DRA). The 100% reflectance baseline was collected using a white PTFE reference. Data were recorded at room temperature (spectral range 200–1000 nm, scanning rate 10 nm/s, data interval 1.00 nm) for finely powdered crystalline samples. Results and discussion The salt ( l -ProH··· l -Pro)(I 3 ) ( I ) crystallizes in the monoclinic polar space group P 2 1 (Table 1 ). The asymmetric unit contains one formula unit (Fig. 1 ). Selected bond lengths and the angle in the triiodide anion are listed in Table 2 , while geometric parameters of hydrogen bonds are provided in Table 3 . The packing diagram in the structure of ( I ) is shown in Fig. 2 . The intramolecular bond lengths of protonated l -ProH and zwitterionic l -Pro have typical values and are similar to those of ( l -ProH··· l -Pro)(I) (Table 2 ). The bond lengths and the angle of the I 3 − ion are as expected (see [ 1 , 2 ]). Table 2 Selected bond lengths and the angle of I 3 − ion (in Å and °) for ( l -ProH··· l -Pro)(I 3 ) ( I ) and ( l -ProH··· l -Pro)(I) [ 9 ] for comparison. Bonds A B A [ 9 ] B [ 9 ] C1-O1 1.294(5) 1.279(4) 1.292(2) 1.274(2) C1-O2 1.218(5) 1.226(4) 1.217(2) 1.234(2) C1-C2 1.517(4) 1.526(6) 1.514(3) 1.516(2) C2-C3 1.526(6) 1.547(6) 1.518(3) 1.523(3) C3-C4 1.489(8) 1.511(10) 1.527(3) 1.523(3) C4-C5 1.506(8) 1.471(8) 1.515(3) 1.526(3) C5-N1 1.495(6) 1.484(5) 1.506(5) 1.512(3) N1-C2 1.499(5) 1.497(4) 1.497(3) 1.499(2) I1-I2 2.9213(5) I2-I3 2.8805(5) I1-I2-I3 178.525(14) The dimeric cation ( l -ProH··· l -Pro) in the structure of ( I ) is formed due to a strong hydrogen bond O1A-H1A···O1B with an O···O distance of 2.458(4) Å (Table 3 ). This value is close to that of ( l -ProH··· l -Pro)(I) (2.454(2) Å) [ 10 ]. In ( I ), carbonyl atoms have a trans -arrangement relative to the hydrogen bond in contrast to ( l -ProH··· l -Pro)(I), where they are in a cis -arrangement. The NH 2 + groups of A- and B-moieties form hydrogen bonds with the nearest oxygen atoms, but not with the triiodide anion, while there are five C-H···I type contacts (Table 3 ). Some of them may be considered as weak hydrogen bonds. Notably, the triiodide anions in the structure of ( I ) are not connected to each other by halogen bonds. Table 3 Hydrogen bond parameters (in Å and °) for ( l -ProH··· l -Pro)(I 3 ) ( I ). D-H···A D-H H···A D···A DHA O1A-H1A···O1B 0.93 1.55 2.458(4) 166 N1A-H11A···O1B i 0.91 1.90 2.783(4) 164 N1A-H12A···O2A 0.91 2.24 2.727(4) 113 N1A-H12A···O2B ii 0.91 2.05 2.869(4) 148 N1B-H11B···O1A iii 0.91 1.99 2.865(4) 162 N1B-H12B···O1A 0.91 1.99 2.870(4) 162 N1B-H12B···O2A iv 0.91 2.08 2.865(4) 144 N1B-H12B···O2B 0.91 2.19 2.685(4) 113 C3A-H31A···I2 0.99 3.06 4.035(5) 169 C3A-H32A···I1 v 0.99 2.94 3.867(5) 157 C4B-H42B···I3 vi 0.99 3.07 4.052(5) 170 C5B-H51B···I2 vi 0.99 3.15 3.993(5) 143 C5B-H52B···I2 iv 0.99 3.14 3.975(5) 143 Symmetry code: (i) -x + 2, y-1/2, -z; (ii) x, y-1, z; (iii) -x + 2, y + 1/2, -z + 1; (iv) x, y + 1, z; (v) -x + 1, y + 1/2, -z; (vi) -x + 1, y + 1/2, -z + 1. The salt [( l -ProH) 3 ( l -Pro)](I 3 ) 3 ( II ) also crystallizes in the monoclinic polar P 2 1 space group (Table 1 ). Selected bond lengths and angles are listed in Table 4 , while the geometric parameters of hydrogen bonds are provided in Table 5 . The salt ( II ) with a formal composition of [( l -ProH) 3 ( l -Pro)](I 3 ) 3 has an unusual structure. In Fig. 3 the molecular motif consisting of A-, B-, C-, and D-moieties is shown. The B- and C-moieties form a pseudocentrosymmetric dimer via a very strong hydrogen bond O1C-H1C-O1B with an O···O distance of 2.427 Å (Table 5 ). The bond lengths C1C-O1C (1.274(4) Å) and C1B-O1B (1.270(4) Å) are alike within the error limits and are characteristic for dimers with very short O···O distances. This dimer, in turn, forms hydrogen bonds with cationic A- and D-moieties via O1A-H1A···O2B and O1D-H1D···O2C hydrogen bonds (Table 5 ). Bond lengths C1A-O1A, C1A-O2A and C1D-O1D, C1D-O2D (Table 4 ) are characteristic for carboxylic groups. So, the cationic part in the structure of ( II ) can be presented as a tetramer [ l -ProH···( l -Pro-H- l -Pro)··· l -ProH] 3+ which is balanced by three triiodide anions: (I1-I2-I3) − , (I4-I5-I6) − and (I7-I8-I9) − . The bond lengths and angles of triiodide anions are shown in Table 4 . These three triiodide anions are connected to each other by supramolecular halogen bonds I3···I4 and I6···I7 (Fig. 4 ). Although the average bond lengths (2.9203 Å, 2.9251 Å, 2.9241 Å, respectively) are similar to each other, it is worth noting that for the middle triiodide anion (I4-I5-I6) − surrounded on both sides, the bond lengths (2.9235 Å and 2.9268 Å) are closer than in the other two cases (Table 4 ). Table 4 Selected bond lengths and angles (in Å and °) for [( l -ProH) 3 ( l -Pro)](I 3 ) 3 ( II ). Bonds A B C D C1-O1 1.304(5) 1.270(4) 1.274(4) 1.303(5) C1-O2 1.207(5) 1.231(5) 1.232(5) 1.209(5) C1-C2 1.512(5) 1.524(4) 1.525(4) 1.512(5) C2-C3 1.517(5) 1.540(5) 1.539(6) 1.520(5) C3-C4 1.530(5) 1.540(5) 1.529(5) 1.518(5) C4-C5 1.506(6) 1.516(6) 1.510(6) 1.507(6) C5-N1 1.509(5) 1.484(5) 1.494(5) 1.498(5) N1-C2 1.502(5) 1.504(4) 1.501(5) 1.491(5) I1-I2 2.9757(4) I4-I5 2.9235(4) I2-I3 2.8649(4) I5-I6 2.9268(4) I7-I8 2.8535(4) I3···I4 3.6663(6) I8-I9 2.9948(4) I6···I7 3.6146(6) I1-I2-I3 174.864(13) I2-I3···I4 167.19(1) I4-I5-I6 177.434(14) I3···I4-I5 168.74(1) I7-I8-I9 176.175(13) I5-I6···I7 172.62(1) I6···I7-I8 173.21(1) The NH 2 + groups form five N-H···I type hydrogen bonds with anions and two N-H···O type hydrogen bonds (excluding one intramolecular bond) with the carbonyl oxygen atoms O2A and O2D of neighboring A- and D- l -prolinium cations. Additionally, there are five C-H···I type short contacts that can be considered weak hydrogen bonds. All iodine atoms that form N-H···I and C-H···I contacts are terminal atoms of triiodide anions. Table 5 Hydrogen bond parameters (in Å and °) for [( l -ProH) 3 ( l -Pro)](I 3 ) 3 ( II ). D-H···A D-H H···A D···A DHA O1A-H1A···O2B i 0.70(5) 1.97(5) 2.674(4) 173(7) O1C-H1C···O1B i 1.19 1.35 2.427(3) 146 O1D-H1D···O2C ii 0.70(5) 1.99(5) 2.664(4) 162(6) N1A-H11A···O2A 0.91 2.21 2.692(4) 113 N1A-H12A···I1 0.91 2.82 3.690(3) 147 N1B-H11B···O2A iii 0.91 2.03 2.818(4) 144 N1B-H12B···I4 iii 0.91 2.91 3.690(3) 144 N1C-H11C···O2D iv 0.91 2.06 2.836(4) 142 N1C-H12C···I6 v 0.91 2.93 3.698(3) 143 N1D-H11D···I9 vi 0.91 3.08 3.856(4) 144 N1D-H12D···I9 iii 0.91 2.82 3.638(4) 150 C2A-H2A···I1 1.00 3.11 3.831(4) 130 C3A-H31A···I7 iii 0.99 3.09 3.844(5) 134 C3A-H32A···I7 vi 0.99 3.04 3.873(5) 143 C2D-H2D···I3 1.00 3.12 3.953(4) 141 C3D-H31D···I3 vi 0.99 3.09 3.821(5) 131 Symmetry code: (i) x, y, z + 1; (ii) x, y, z-1; (iii) -x + 1, y-1/2, -z + 1; (iv) -x + 2, y-1/2, -z + 1; (v) -x + 1, y-1/2, -z + 2; (vi) -x + 1, y + 1/2, -z + 1; (vii) x, y + 1, z. The infrared spectra of ( I ) and ( II ) are shown in Fig. 5 . A tentative assignment of peaks is given in Table 6 . In the high-frequency region of ( I ), one can expect absorptions caused by stretching modes of NH 2 + , CH, and CH 2 groups. The stretching mode ν(OH) of the protonated A-moiety is assumed to be in the low-frequency region [ 19 ]. The strong absorption band at 3123 cm − 1 is assigned to ν(NH), while the peaks at 3004, 2975, and 2943 cm − 1 to ν(CH). The peak at 1707 cm − 1 is characteristic for ν(C = O) of a carboxylic group, while the rather strong one at 1577 cm − 1 is assigned to the deformation vibrations of NH 2 + groups. Peaks at 1446, 1419, 1376, 1346, and 1321 cm − 1 are assigned to the deformation vibrations of CH 2 groups. The peak at 1419 cm − 1 may also be caused by ν s (COO − ). Those in the 1200 − 800 cm − 1 range are superimposed with a broad absorption centered ca . 990 cm − 1 which is likely caused by ν(OH) stretching mode (see [ 19 ]). In the high-frequency region of ( II ), one can expect absorptions caused by stretching modes of NH 2 + , CH, CH 2 groups as well as OH groups of carboxyl groups of A- and D- l -prolinium cations. The strong absorption band near 3000 cm − 1 is assigned to ν(NH) of NH 2 + (peak at 3133 cm − 1 ) and ν(OH) (the peak at 3075 cm − 1 ). Expected values of ν(OH) based on the correlation ν(OH) vs . R(O···O) [ 18 ] for hydrogen bonds O1A-H1A···O2B (2.674 Å) and O1D-H1D···O2C (2.664 Å) are close to the observed ones. Weak peaks at 3006, 2982, 2936 cm − 1 are assigned to ν(CH). The strong absorption band at 1715 cm − 1 is characteristic for ν(C = O) of a carboxyl group. We assign it to ν(C = O) of the carboxyl groups of A- and D- l -prolinium cations. The position of weak absorption at 1653 cm − 1 is characteristic for ν as (COO − ). We assign it to the ( l -Pro-H- l -Pro) dimeric cation. The weakness is likely caused by its pseudocentrosymmetric nature. The bands at 1552 and 1448 cm − 1 are also characteristic for proline and originated from δ(NH 2 ) and δ(CH 2 ), respectively. In the lower range there are peaks due to other deformation vibrations of CH 2 and NH 2 groups, as well as ring vibrations. The characteristic feature is also the absorption band at 1242 cm − 1 , which we attribute to the ν(C-OH) of the carboxyl groups of A- and D- l -prolinium cations. More interesting is that these peaks are superimposed on half of the broad band in the 1400 − 500 cm − 1 region. Such a feature in this region is characteristic for ν(OH) of very strong hydrogen bonds in dimeric cations. We assign it to the ν(OH) of the ( l -Pro-H- l -Pro) dimeric cation. For strong hydrogen bonds (R(O···O) = 2.40–2.58 Å) the correlation of ν(OH)(cm − 1 ) vs . R(O···O) (Å) [ 19 ] has approximately linear character: ν(OH) = 12500R-29875. For R(O···O) = 2.427 Å the expected value of ν(OH) is ca . 460 cm − 1 , which corresponds well to the center of the mentioned broad band. Table 6 Wavenumbers (cm − 1 ) and assignment of peaks in the infrared spectra of ( l -ProH··· l -Pro)(I 3 ) ( I ) and [( l -ProH) 3 ( l -Pro)](I 3 ) 3 ( II ). (I) (II) Assignment 3123 3133 ν(NH) 3075 ν(OH) 3004;2975;2943 3006;2982;2936 ν(CH) 2880;2739;2553; 2448 2875;2733 Combi 1707 1715 ν(C = O) 1647 1653 ν as (COO − ) 1577 1552 δ(NH 2 ) 1446;1419 1448 δ(CH 2 ) 1376;1346 1369 ω(CH 2 ) 1321 1330 τ(CH 2 ) 1300 1306 τ(CH) 1279 1282;1266 δ(CH) 1231 1242 ν(C-OH) 1188;1163 1190;1169 ω(NH 2 ) 1081;1050;1024 1088;1044 987; 919;860 987;950;921;900;860 788;765;722 754;737;662 DFT calculations of the electronic structure of ( I, II ) crystals The grid parameters for calculating electronic properties were 3×3×2 ( I ) and 2×3×1 ( II ), k-point set in the Brillouin region for crystals. In a Kohn–Sham computation, the approximate functional used to determine the exchange-correlation energy (𝐸𝑥𝑐) has a significant impact on the accuracy of the final findings. The electronic structure simulations were performed based on the DFT theory by OTFG (On-the-fly generation) ultrasoft pseudopotentials. The relativistic treatment was Koelling-Harmon, energy range – 10 eV, separation compares 0.005 1/Å. Band energy tolerance is within 1.0 x 10 −5 eV per atom. The DOS and PDOS were calculated. The inhomogeneous electron densities in solids and the slow valence electron density fluctuations in space make using the generalized gradient approximation (GGA) in the PBE scheme for computing electronic characteristics an excellent method. We calculated the energy band structures with the directions with high first Brillouin zone equilibrium points, including Z→G→Y→A→B→D→E→C for both ( I ) and ( II ) crystals. A direct transition energy for ( I, II) crystals, which appears between the highest valence band value and the lowest conduction band value of the Brillion region at the symmetry point B, is 2.281 eV ( I ) and 1.641 eV ( II ), and an indirect band gap at Y→G range is 1.631 eV ( II) (Fig. 6 ). For the ( l -ProH··· l -Pro)(I 3 ) ( I ) crystal indirect transition was not observed. As is known, the density of states (DOS) of a system describes the number of states occupied at each energy level in statistical and solid-state physics. Composition of the calculated energy bands can be resolved with the help of partial density of states (PDOS) and total density of states (TDOS) diagrams. Figures 7 and 8 demonstrate the total density of states for the valence and conduction bands. In these figures, the zero tick mark on the energy scales (the top of the valence band) indicates the position of the Fermi level. To obtain a measure of the contribution of different atomic states to the band structure, as well as to their possible hybridizations, a comprehensive analysis of the partial density of states was carried out. From the supercell calculations, the PDOS for the different elements O (2s 2 , 2p 4 ), N (2s 2 , 2p 3 ) and I (5s 2 4d 10 5p 5 ) in the ( l -ProH··· l -Pro)(I 3 ) ( I ) and [( l -ProH) 3 ( l -Pro)](I 3 ) 3 ( II ) crystals are extracted and shown in Figs. 7 and 8 . These diagrams allow us to conclude that the main contribution near the edge of the conduction band for both crystals is made by the I (5p) states, which hybridize with the N (2p) and O (2p) states. In the presence of states I (5p), the band gap for ( I ) is E g = 2.281 eV, and for ( II ) it is E g = 1.631 eV. Salt ( II ) has a complicated composition [( l -ProH) 3 ( l -Pro)](I 3 ) 3 containing a peculiar tetrameric cation [ l -ProH···( l -Pro-H- l -Pro)··· l -ProH]. In addition, the presence of triiodide anions with their supramolecular halogen bonds leads to a decrease in the bandgap compared to the salt ( l -ProH··· l -Pro)(I 3 ) ( I ). Bandgap measurements The type of transition selected based on DFT-calculations and the bandgap were estimated from the UV-Vis diffuse reflectance data (Fig. 9 ) using Tauc expression and Kubelka-Munk function [ 20 – 22 ]. The bandgap for the direct transition ( I ) is 2.04 eV while for the indirect one it is 1.51 eV ( II ). Conclusions Two new crystalline salts were obtained: ( l -ProH··· l -Pro)(I 3 ) ( I ) and [( l -ProH) 3 ( l -Pro)](I 3 ) 3 ( II ). The compound ( l -ProH··· l -Pro)(I 3 ) ( I ) with a ( l -ProH··· l -Pro) dimeric cation exhibits a short hydrogen bond with an O···O distance of 2.458(4) Å, which is close to the 2.454(2) Å observed in the structure of ( l -ProH··· l -Pro)(I) [ 10 ]. The salt [( l -ProH) 3 ( l -Pro)](I 3 ) 3 ( II ) shows an unusual structure with a peculiar tetrameric cation [ l -ProH···( l -Pro-H- l -Pro)··· l -ProH], where ( l -Pro-H- l -Pro) is a pseudocentrosymmetric dimer with a very short hydrogen bond with an O···O distance of 2.427 Å. Three triiodide anions are connected I1-I2-I3···I4-I5-I6···I7-I8-I9 by halogen bonds I3···I4 and I6···I7, being 3.6663 Å and 3.6146 Å, respectively. Infrared spectra of ( I , II ) were registered and interpreted based on their structures. The presence of short hydrogen bonds in dimeric cations is reflected in the spectra. Electronic band structures were determined derived from crystal structures by quantum chemical calculations. The structure of the calculated energy bands was analyzed using partial density of states diagrams. The energies of the direct transition with a bandgap of E g = 2.281 eV for ( I ) and the indirect transition with a bandgap of E g = 1.631 eV for ( II ) have been determined. In addition, the bandgaps were measured from the diffuse reflectance spectra, which were equal to E g = 2.04 eV for ( I ) and E g = 1.51 eV for ( II ). Declarations Funding The work was supported by the Science Committee of RA, in the frame of the research project № 21AG-1D015 . Availability of data and material Further crystallographic data have been deposited with the Cambridge Crystallographic Data Centre and can be obtained free of charge via www.ccdc.cam.ac.uk/conts/retrieving. html (or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax:+44 1223 336,033), citing the title of this paper and the CCDC nos. 2212285–2212293. Code availability CCDC nos. 2281225 and 2281226. Code availability CCDC nos. 2281225 ( II ) and 2281226 ( I )). Conflict of interest The authors declare no competing interests. References Per H, Svensson L, Kloo (2003) Synthesis, structure, and bonding in polyiodide and metal iodide-iodine systems. Chem Rev 103:1649–1684. https://doi.org/10.1021/cr0204101 Matteo, Savastano (2021) Words in supramolecular chemistry: the ineffable advances of polyiodide chemistry. Dalton Trans 50:1142–1165. https//doi.org/10.1039/dodt04091F Shestimerova TA, Yelavik NA, Mironov AV, Kuznetsov AN, Bykov MA, Grigorieva AV, Utochnikova VV, Lepnev LS, Shevelkov AV (2018) From isolated anions to polymer structures through linking with I 2 : Synthesis, structure, and properties of two complex bismuth(III) iodine iodides. Inorg Chem 57:4077–4087. https://doi.org/10.1021/acs.inorgchem.8b00265 Zhang W, Liu X, Li L, Sun Z, Han S, Wu Z, Luo J (2018) Triiodide-induced band-edge reconstruction of a lead-free perovskite-derivative hybrid for strong light absorption. Chem Mater 30:4081–4088. https://doi.org/10.1021/acs.chemmater.8b01200 Giester G, Ghazaryan V, Tonoyan G, Szafrański M, Mkrtchyan A, Halogenobismuthates of amino acids as solar energy converters. Armenian Patent # 751 Y, Petrosyan AM, Giester G, Ghazaryan VV, Tonoyan GS, Zatikyan AL, Szafrański M, Mkrtchyan AH (2022) Growth and characterization of halogenobismuthates of amino acids. Abstracts of Intern. Conf. Crystal Growth and Epitaxy (ICCGE-20), 30 July-4 August 2023, Naples, Italy, Abstract #115. https://coms.events/ICCGE-20 /data/x_abstracts/x_abstract_115.pdf Michel Fleck C, Lengauer L, Bohatý (2008) Ekkehert Tillmanns, Synthesis, crystal structures and thermal behaviour of novel l-alanine halogenide compounds. Acta Chim Slov 55:880–888. https://www.researchgate.net/publication/228529976_Syntheses_Crystal_Structures_and_Thermal_Behaviour_of_Novel_L-Alanine_Halogenide_Compounds Shestimerova TA, Bykov MA, Wei Z, Dikarev EV, Shevelkov AV (2019) Crystal structure and two-level supramolecular organization of glycinium triiodide. Russ Chem Bull Intern Edition 68:1520–1524. https://doi.org/10.1007/s11172-019-2586-0 Giester G, Ghazaryan VV, Tonoyan GS, Zatikyan AL, Petrosyan MS, Petrosyan AM Polyiodides of amino acids. Abstracts of Intern. Conf. Crystal Growth and Epitaxy (ICCGE-20), 30 July-4 August 2023, Naples, Italy, Abstract #748. https://coms.events/ICCGE-20/data/x_abstracts/x_abstract_748.pdf Gerald Giester AL, Zatikyan, Gayane S, Tonoyan VV, Ghazaryan, Marek Szafrański AM, Petrosyan (2024) Polyiodides of amino acids. Betainium triiodide. J Mol Struct 1297:136960. https://doi.org/10.1016/j.molstruc.2023.136960 Petrosyan AM, Giester G, Ghazaryan VV (2021) Fleck, l-Prolinium l-proline halogenides: a comparison of the respective chloride, bromide and iodide salts. J Mol Struct 1243:130851. https://doi.org/10.1016/j.molstruc.2021.130851 Bruker (2022) APEX4 software suite, Bruker AXS Inc, Madison, Wisconsin, USA, Sheldrick GM (2015) SHELXT - Integrated space-group and crystal-structure determination. Acta Crystallogr A71:3–8. https://doi.org/10.1107/S2053273314026370 Sheldrick GM (2015) Crystal structure refinement with SHELXL. Acta Crystallogr C 71:3–8. https://doi.org/10.1107/S2053229614024218 Hübschle CB, Sheldrick GM, Dittrich B (2011) ShelXle : a Qt graphical user interface for SHELXL . J Appl Cryst 44:1281–1284. https://doi.org/10.1107/S0021889811043202 Parsons S, Flack HD, Wagner T (2013) Use of intensity quotients and differences in absolute structure refinement. Acta Crystallogr B69:249–259. https://doi.org/10.1107/S2052519213010014 Clark SJ, Segall MD, Pickard CJ, Hasnip PJ, Probert MJ, Refson K, Payne MC (2005) First principles methods using CASTEP. Z. Kristallogr. 220(5–6) 567–570. http://www.oldenbourg-link.com/doi/abs/ 10.1524/zkri.220.5.567.65075 Hohenberg P, Kohn W (1964) Inhomogeneous electron gas. Phys Rev 136:B864–B871. https://doi.org/10.1103/PhysRev.136.B864 Perdew JP, Ruzsinszky A, Csonka GI, Vydrov OA, Scuseria GE, Constantin LA, Zhou X, Burke K (2008) Restoring the density-gradient expansion for exchange in solids and surfaces. Phys Rev Lett 100:136406–136409. https://doi.org/10.1103/PhysRevLett.100.136406 Novak A (1979) Vibrational spectroscopy of hydrogen bonded systems, in Infrared and Raman Spectroscopy of Biological Molecules. NATO Advanced Study Institute Series, Vol. 43, pp. 279–303 Dordrecht: Kluwer. https://doi.org/10.1007/978-94-009-9412-6_22 Tauc J, Grigorovici R, Vancu A (1966) Optical properties and electronic structure of amorphous germanium. Phys Status Solidi 15:627–637. https://doi.org/10.1002/pssb.19660150224 Tauc J (1970) Absorption edge and internal electric fields in amorphous semiconductors. Mater Res Bull 5(8):721–729 Davis EA, Mott NF (1970) Conduction in non-crystalline systems V. Conductivity, optical absorption and photoconductivity in amorphous semiconductors. The Philosophical Magazine: A Journal of Theoretical Experimental and Applied Physics 22(issue179):0903–0922. 10.1080/14786437008221061 Supplementary Material Supplementary Material is not available with this version Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 09 Feb, 2024 Read the published version in Structural Chemistry → Version 1 posted Editorial decision: Accepted 02 Feb, 2024 Reviews received at journal 28 Jan, 2024 Reviewers agreed at journal 23 Jan, 2024 Reviewers invited by journal 23 Jan, 2024 Editor assigned by journal 23 Jan, 2024 Submission checks completed at journal 22 Jan, 2024 First submitted to journal 16 Jan, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-3869782","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":268967334,"identity":"da3a908f-c7df-4672-9206-0a355b7f07aa","order_by":0,"name":"Gerald Giester","email":"","orcid":"","institution":"University of Vienna","correspondingAuthor":false,"prefix":"","firstName":"Gerald","middleName":"","lastName":"Giester","suffix":""},{"id":268967335,"identity":"ca07fc6a-44e2-4de7-bf13-c2fd2fb4547f","order_by":1,"name":"Vahram V. Ghazaryan","email":"","orcid":"","institution":"IAPP: Institute of Applied Problems of Physics","correspondingAuthor":false,"prefix":"","firstName":"Vahram","middleName":"V.","lastName":"Ghazaryan","suffix":""},{"id":268967336,"identity":"2f5518d9-097e-422f-a56c-8349b457b2c8","order_by":2,"name":"Ashkhen L. Zatikyan","email":"","orcid":"","institution":"Yerevan State University","correspondingAuthor":false,"prefix":"","firstName":"Ashkhen","middleName":"L.","lastName":"Zatikyan","suffix":""},{"id":268967337,"identity":"1c5db21f-5d6d-4667-8870-6f4e230bddc4","order_by":3,"name":"Aram M. Petrosyan","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABDUlEQVRIiWNgGAWjYEgAfhCRUECMUjYoLdkA0mJAihaDA2ASjzNmH366gTGHIY9fvvfhw59tdnnG51cnfnhgwCDPL3YAqxaJc2lmNxi3MRRLtrEbG/O2JReb3Xi7WQLoMMOZsxOwW3OGAawlccMxNjZpxjbmxG03zm4AaUkwuI1di/wZ9m9gLfuBWiR/ttUnbp5xdvMPfFoMzvBAbWFjY5PgbTucuIG/dxteWwzP8JTdSNwmUSxxLI3ZmOfc8cQZN3i3WSQYSOD0i9wZ9m03Pm6zyeNvPsb48EdZdWJ//9nNN39U2MjzS+PwPggkMEhAZBlBkQNhS+BWDtcFBn+AmP8AQdWjYBSMglEwsgAAjlpeEgo5hbsAAAAASUVORK5CYII=","orcid":"","institution":"IAPP: Institute of Applied Problems of Physics","correspondingAuthor":true,"prefix":"","firstName":"Aram","middleName":"M.","lastName":"Petrosyan","suffix":""}],"badges":[],"createdAt":"2024-01-16 12:35:12","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-3869782/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-3869782/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s11224-024-02291-8","type":"published","date":"2024-02-09T15:00:41+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":50183123,"identity":"f85cf931-e82d-4eb4-8aa4-ee05a5a24231","added_by":"auto","created_at":"2024-01-25 19:07:22","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":722015,"visible":true,"origin":"","legend":"\u003cp\u003eMolecular structure of (l-ProH···l-Pro)(I\u003csub\u003e3\u003c/sub\u003e) (\u003cstrong\u003eI\u003c/strong\u003e).\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-3869782/v1/058300c7a11a555e6190b72e.png"},{"id":50183121,"identity":"edc4cf2f-a013-4abb-a2d6-9c561cdf898c","added_by":"auto","created_at":"2024-01-25 19:07:22","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1317795,"visible":true,"origin":"","legend":"\u003cp\u003ePacking diagram in the structure of (l-ProH···l-Pro)(I\u003csub\u003e3\u003c/sub\u003e) (\u003cstrong\u003eI\u003c/strong\u003e).\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-3869782/v1/723a746971e5f7c806a6d7f7.png"},{"id":50183122,"identity":"8cd23439-774c-4ab5-84f9-681d6fc830b8","added_by":"auto","created_at":"2024-01-25 19:07:22","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":1504184,"visible":true,"origin":"","legend":"\u003cp\u003eMolecular structure of [(l-ProH)\u003csub\u003e3\u003c/sub\u003e(l-Pro)](I\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e (\u003cstrong\u003eII\u003c/strong\u003e).\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-3869782/v1/2b5c6f4ad5616d723c797376.png"},{"id":50183125,"identity":"6bc0e473-2462-4be1-95ec-6efb5aae984a","added_by":"auto","created_at":"2024-01-25 19:07:23","extension":"jpeg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":421817,"visible":true,"origin":"","legend":"\u003cp\u003ePacking diagram in the structure of [(l-ProH)\u003csub\u003e3\u003c/sub\u003e(l-Pro)](I\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e (\u003cstrong\u003eII\u003c/strong\u003e).\u003c/p\u003e","description":"","filename":"floatimage4.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-3869782/v1/7f5b804b22cdcaccbf9b7a87.jpeg"},{"id":50183320,"identity":"2f4b80f6-eeed-4dfa-b61a-8b51e83cde92","added_by":"auto","created_at":"2024-01-25 19:15:23","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":508206,"visible":true,"origin":"","legend":"\u003cp\u003eInfrared spectra of (l-ProH···l-Pro)(I\u003csub\u003e3\u003c/sub\u003e) (\u003cstrong\u003eI\u003c/strong\u003e) and of [(l-ProH)\u003csub\u003e3\u003c/sub\u003e(l-Pro)](I\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e (\u003cstrong\u003eII\u003c/strong\u003e).\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-3869782/v1/14fe3dc21e4f9d86ef006c2c.png"},{"id":50183128,"identity":"dfa62d52-4682-4d97-a77e-e9654b5c2bcd","added_by":"auto","created_at":"2024-01-25 19:07:23","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":159317,"visible":true,"origin":"","legend":"\u003cp\u003eElectronic band structure of (\u003cstrong\u003eI, II\u003c/strong\u003e) crystals along the high symmetry directions in the Brillouin zones using GGA-PBE.\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-3869782/v1/5d1a8ff8a2699c8e47065943.png"},{"id":50183321,"identity":"9f0d111b-4796-4532-8c9c-097c09212548","added_by":"auto","created_at":"2024-01-25 19:15:23","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":211636,"visible":true,"origin":"","legend":"\u003cp\u003eTotal and partial density of states for N, O and I atoms in the (l-ProH···l-Pro)(I\u003csub\u003e3\u003c/sub\u003e) (\u003cstrong\u003eI\u003c/strong\u003e) crystal.\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-3869782/v1/4e3131afa9708fe9dbf1e3a2.png"},{"id":50183124,"identity":"23f31e76-ad90-4b41-9136-61c763f2cb39","added_by":"auto","created_at":"2024-01-25 19:07:22","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":214601,"visible":true,"origin":"","legend":"\u003cp\u003eTotal and partial density of states for N, O, and I atoms in the [(l-ProH)\u003csub\u003e3\u003c/sub\u003e(l-Pro)](I\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e (\u003cstrong\u003eII\u003c/strong\u003e) crystal.\u003c/p\u003e","description":"","filename":"floatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-3869782/v1/cbeed7c747c3e5a064e4bf7e.png"},{"id":50183126,"identity":"7f3d3f45-e6dd-4d26-afaf-21ae515db7b7","added_by":"auto","created_at":"2024-01-25 19:07:23","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":2719859,"visible":true,"origin":"","legend":"\u003cp\u003eCrystals and powders of (\u003cstrong\u003eI\u003c/strong\u003e) and (\u003cstrong\u003eII\u003c/strong\u003e). Diffuse reflectance spectra and Tauc plots for direct (\u003cstrong\u003eI\u003c/strong\u003e) and indirect (\u003cstrong\u003eII\u003c/strong\u003e) transitions.\u003c/p\u003e","description":"","filename":"floatimage9.png","url":"https://assets-eu.researchsquare.com/files/rs-3869782/v1/ddc5a5e26e35a93e2efd2643.png"},{"id":51005477,"identity":"6bd5d5e1-5b6f-490e-ac6b-8366de84f884","added_by":"auto","created_at":"2024-02-12 15:08:15","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2046341,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3869782/v1/5594748f-e861-48d2-8bfd-80d70c5626d8.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Polyiodides of amino acids. L-Proline triiodides","fulltext":[{"header":"Introduction","content":"\u003cp\u003eThe study of polyiodides is of great scientific and practical interest [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. The incorporation of iodine (I\u003csub\u003e2\u003c/sub\u003e) molecules and triiodide (I\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e) anions into the structure of halogenobismuthate salts allows for a significant narrowing of the bandgap [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Recently, we have begun searching for new amino acid salts with halogenobismuthate anions as potential materials for solar energy conversion [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Amino acid salts containing polyiodide anions and iodine molecules can serve as starting materials and are also interesting in their own right. Previously, two salts of amino acids with a triiodide anion were obtained: (\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-AlaH\u0026middot;\u0026middot;\u0026middot;\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Ala)(I\u003csub\u003e3\u003c/sub\u003e) [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e] and (GlyH)(I\u003csub\u003e3\u003c/sub\u003e) [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Based on these findings, the search for new amino acid salts containing polyiodide anions and iodine molecules started [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Recently a paper was published on (BetH)(I\u003csub\u003e3\u003c/sub\u003e) which contains a centrosymmetric dimeric (BetH\u0026middot;\u0026middot;\u0026middot;BetH) cation of the (A\u003csup\u003e+\u003c/sup\u003e\u0026middot;\u0026middot;\u0026middot;A\u003csup\u003e+\u003c/sup\u003e) type [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe present paper describes two salts of \u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-proline. One of them is an analog of (\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-AlaH\u0026middot;\u0026middot;\u0026middot;\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Ala)(I\u003csub\u003e3\u003c/sub\u003e) [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]: (\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-ProH\u0026middot;\u0026middot;\u0026middot;\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro)(I\u003csub\u003e3\u003c/sub\u003e) (\u003cb\u003eI\u003c/b\u003e). The corresponding iodide (\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-ProH\u0026middot;\u0026middot;\u0026middot;\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro)(I) has been previously studied in [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. The second one, [(\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-ProH)\u003csub\u003e3\u003c/sub\u003e(\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro)](I\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e (\u003cb\u003eII\u003c/b\u003e), has a complicated composition with an unusual structure containing a peculiar tetrameric cation [\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-ProH\u0026middot;\u0026middot;\u0026middot;(\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro-H-\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro)\u0026middot;\u0026middot;\u0026middot;\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-ProH]. Synthesis, crystal growth, single-crystal structure determination, infrared spectra, and bandgaps measured by the diffuse reflectance method and supplemented by quantum chemical calculations, are presented and discussed.\u003c/p\u003e"},{"header":"Experimental","content":"\u003cp\u003eMaterials and synthesis\u003c/p\u003e \u003cp\u003eAs initial reagents we used \u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-proline (98.5\u0026ndash;101.0%, Ph. Eur., USP, PanReac AppliChem ITW reagents), hydriodic acid (54.6% w/w, distilled, Vekton JSC), crystalline iodine (\u0026ldquo;high purity\u0026rdquo;, Reakhim), acetonitrile (Ph. Eur., for UHPLC, PanReac AppliChem ITW reagents), and medical ethanol (95%, from a commercial source). Crystals were obtained at room temperature by slow evaporation of the appropriate solutions. Crystals of (\u003cb\u003eI\u003c/b\u003e) were formed from a mixture containing \u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-proline, HI and I\u003csub\u003e\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003e2\u003c/span\u003e\u003c/sub\u003e in a stoichiometric 2:1:1 M-ratio taking 1.000 g of \u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-proline, 1.59 ml of hydriodic acid, and 2.849 g of iodine, and then adding 2 ml of ethanol. Trying to obtain (\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-ProH)(I\u003csub\u003e3\u003c/sub\u003e) from a 1:1:1 M-ratio (1.000 g of \u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-proline, 1.233 ml of hydriodic acid and 2.205 g of iodine) with 2 ml of acetonitrile, the crystals of (\u003cb\u003eII\u003c/b\u003e) were formed. Subsequently, crystals of (\u003cb\u003eII\u003c/b\u003e) were also synthesized from a solution with a stoichiometric 4:3:3 M-ratio of components, i.e., taking 1.000 g of \u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-proline, 0.92 ml of hydriodic acid and 1.653 g of iodine, and adding 2 ml of ethanol. Crystals formed within two weeks.\u003c/p\u003e \u003cp\u003eInfrared spectra\u003c/p\u003e \u003cp\u003eAttenuated total reflection Fourier-transform infrared spectra (ATR-FTIR) were recorded on an Agilent Cary 630 spectrometer using a germanium (Ge) ATR sampling module (Ge crystal, Happ-Genzel apodization, ATR distortion corrected, 64 scans, 4 cm\u003csup\u003e\u0026ndash;1\u003c/sup\u003e resolution).\u003c/p\u003e \u003cp\u003eStructure determination\u003c/p\u003e \u003cp\u003eAppropriate single crystals were manually selected for homogeneous extinction, mounted on \u003cem\u003eMiTeGen\u003c/em\u003e loops with silicone grease and used for single crystal X-ray data collections on a Bruker APEX II diffractometer equipped with a CCD area detector, an Incoatec Microfocus Source I\u0026micro;S (30 W, multilayer mirror, Mo-K\u003csub\u003eα\u003c/sub\u003e) and an Oxford Cryosystems Cryostream 800 Plus LT device. Data were collected at 200 K up to 65\u0026deg; 2θ full sphere by combining several runs of frames recorded at crystal-detector distances of 40 mm and 2\u0026deg; (\u003cb\u003eI\u003c/b\u003e) and 1.5\u0026deg; (\u003cb\u003eII\u003c/b\u003e) scan widths. Further data processing was done with the Bruker APEX4 software suite [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. The absorption was corrected by evaluation of multi-scans. The structures were solved by direct methods [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Subsequent difference Fourier syntheses and least-squares refinements yielded the positions of the remaining atoms using the SHELX software [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e] implemented in the ShelXle GUI tool [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. Non-hydrogen atoms were refined with independent anisotropic displacement parameters.\u003c/p\u003e \u003cp\u003eStructural data are available as Supplementary Material and have been deposited as CIF to the Cambridge Crystallographic Data Base (CCDC Nos. 2281225 (\u003cb\u003eII\u003c/b\u003e) and 2281226 (\u003cb\u003eI\u003c/b\u003e)). They can be downloaded free of charge from the following site: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://www.ccdc.cam.ac.uk\u003c/span\u003e\u003cspan address=\"http://www.ccdc.cam.ac.uk\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eCrystallographic data and details of the structure refinement for (\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-ProH\u0026middot;\u0026middot;\u0026middot;\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro)(I\u003csub\u003e3\u003c/sub\u003e) (\u003cb\u003eI\u003c/b\u003e) and [(\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-ProH)\u003csub\u003e3\u003c/sub\u003e(\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro)](I\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e (\u003cb\u003eII\u003c/b\u003e).\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCrystal\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e(I)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e(II)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEmpirical Formula\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eC\u003csub\u003e10\u003c/sub\u003eH\u003csub\u003e19\u003c/sub\u003eI\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eC\u003csub\u003e20\u003c/sub\u003eH\u003csub\u003e39\u003c/sub\u003eI\u003csub\u003e9\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003eO\u003csub\u003e8\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFormula mass\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e611.97\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1605.65\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCrystal system\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMonoclinic\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMonoclinic\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSpace group\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e2\u003csub\u003e1\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e2\u003csub\u003e1\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003ea\u003c/em\u003e (\u0026Aring;)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e9.6021(7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e14.4830(12)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eb\u003c/em\u003e (\u0026Aring;)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e9.2481(7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7.2365(6)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003ec\u003c/em\u003e (\u0026Aring;)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10.2565(8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e18.8372(17)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eβ\u003c/em\u003e (\u0026deg;)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e100.163(2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e90.681(3)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eV\u003c/em\u003e (\u0026Aring;\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e896.50(12)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1974.1(3)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eZ\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCrystal size (mm\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.300\u0026times;0.125\u0026times;0.100\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.200\u0026times;0.100\u0026times;0.075\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eρ\u003c/em\u003e\u003csub\u003ecalc\u003c/sub\u003e.(g cm\u003csup\u003e\u0026minus;3\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.267\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2.701\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTemperature (K)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e200(2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e200(2)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003e2θ\u003c/em\u003e\u003csub\u003e\u003cem\u003emax\u003c/em\u003e\u003c/sub\u003e (\u0026deg;)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e66.366\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e66.462\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003e\u0026micro;\u003c/em\u003e (mm\u003csup\u003e\u0026ndash;1\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5.240\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7.108\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eF\u003c/em\u003e(000)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e568\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1456\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAbsorption-correction\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMulti-scan\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMulti-scan\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIndex ranges (hkl)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u0026plusmn;14, \u0026plusmn;14, \u0026plusmn;15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u0026plusmn;22, \u0026plusmn;11, +\u0026thinsp;29/-28\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eReflections collected\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e33861\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e83596\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIndependent reflections (\u003cem\u003eR\u003c/em\u003e\u003csub\u003eint\u003c/sub\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6857 (0.0317)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e15093 (0.0331)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eData with \u003cem\u003eF\u003c/em\u003e\u003csub\u003eo\u003c/sub\u003e\u0026gt; 2\u003cem\u003eσ\u003c/em\u003e (\u003cem\u003eF\u003c/em\u003e\u003csub\u003eo\u003c/sub\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5793\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e12980\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFlack parameter [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.000(10)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.004(10)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eParameters refined/restrained\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e175/1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e379/1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eR\u003c/em\u003e\u003csub\u003e1\u003c/sub\u003e\u003csup\u003ea\u003c/sup\u003e/ w\u003cem\u003eR\u003c/em\u003e\u003csub\u003e2\u003c/sub\u003e\u003csup\u003eb\u003c/sup\u003e (\u003cem\u003eI\u003c/em\u003e\u0026thinsp;\u0026gt;\u0026thinsp;2\u003cem\u003eσ\u003c/em\u003e(\u003cem\u003eI\u003c/em\u003e))\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.0260/0.0492\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.0240/0.0414\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eR\u003c/em\u003e\u003csub\u003e1\u003c/sub\u003e\u003csup\u003ea\u003c/sup\u003e/ w\u003cem\u003eR\u003c/em\u003e\u003csub\u003e2\u003c/sub\u003e\u003csup\u003eb\u003c/sup\u003e (for all \u003cem\u003eF\u003c/em\u003e\u003csub\u003eo\u003c/sub\u003e\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.0362/0.0529\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.0336/0.0445\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eΔρ\u003csub\u003efin\u003c/sub\u003e (max/min) [e \u0026Aring;\u003csup\u003e\u0026ndash;3\u003c/sup\u003e]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.73/-0.82\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.92/-0.65\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eMethod of electronic structure calculation\u003c/p\u003e \u003cp\u003eThe calculations have been carried out using the density functional theory (DFT) based CASTEP (Cambridge Serial Total Energy Package) software, along with the generalized gradient approximation (GGA) using the Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional [\u003cspan additionalcitationids=\"CR17\" citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eOptical measurements\u003c/p\u003e \u003cp\u003eUV-Vis diffuse reflectance data were collected using an Agilent Cary 60 UV-Vis spectrophotometer equipped with a Remote Diffuse Reflectance Accessory (DRA). The 100% reflectance baseline was collected using a white PTFE reference. Data were recorded at room temperature (spectral range 200\u0026ndash;1000 nm, scanning rate 10 nm/s, data interval 1.00 nm) for finely powdered crystalline samples.\u003c/p\u003e"},{"header":"Results and discussion","content":"\u003cp\u003eThe salt (\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-ProH\u0026middot;\u0026middot;\u0026middot;\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro)(I\u003csub\u003e3\u003c/sub\u003e) (\u003cb\u003eI\u003c/b\u003e) crystallizes in the monoclinic polar space group \u003cem\u003eP\u003c/em\u003e2\u003csub\u003e1\u003c/sub\u003e (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The asymmetric unit contains one formula unit (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Selected bond lengths and the angle in the triiodide anion are listed in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, while geometric parameters of hydrogen bonds are provided in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. The packing diagram in the structure of (\u003cb\u003eI\u003c/b\u003e) is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. The intramolecular bond lengths of protonated \u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-ProH and zwitterionic \u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro have typical values and are similar to those of (\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-ProH\u0026middot;\u0026middot;\u0026middot;\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro)(I) (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The bond lengths and the angle of the I\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e ion are as expected (see [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eSelected bond lengths and the angle of I\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e ion (in \u0026Aring; and \u0026deg;) for (\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-ProH\u0026middot;\u0026middot;\u0026middot;\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro)(I\u003csub\u003e3\u003c/sub\u003e) (\u003cb\u003eI\u003c/b\u003e) and (\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-ProH\u0026middot;\u0026middot;\u0026middot;\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro)(I) [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e] for comparison.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBonds\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eA\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eB\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eA [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eB [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC1-O1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.294(5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.279(4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.292(2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.274(2)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC1-O2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.218(5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.226(4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.217(2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.234(2)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC1-C2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.517(4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.526(6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.514(3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.516(2)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC2-C3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.526(6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.547(6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.518(3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.523(3)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC3-C4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.489(8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.511(10)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.527(3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.523(3)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC4-C5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.506(8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.471(8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.515(3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.526(3)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC5-N1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.495(6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.484(5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.506(5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.512(3)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eN1-C2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.499(5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.497(4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.497(3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.499(2)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eI1-I2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2.9213(5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eI2-I3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2.8805(5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eI1-I2-I3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e178.525(14)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe dimeric cation (\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-ProH\u0026middot;\u0026middot;\u0026middot;\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro) in the structure of (\u003cb\u003eI\u003c/b\u003e) is formed due to a strong hydrogen bond O1A-H1A\u0026middot;\u0026middot;\u0026middot;O1B with an O\u0026middot;\u0026middot;\u0026middot;O distance of 2.458(4) \u0026Aring; (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). This value is close to that of (\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-ProH\u0026middot;\u0026middot;\u0026middot;\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro)(I) (2.454(2) \u0026Aring;) [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. In (\u003cb\u003eI\u003c/b\u003e), carbonyl atoms have a \u003cem\u003etrans\u003c/em\u003e-arrangement relative to the hydrogen bond in contrast to (\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-ProH\u0026middot;\u0026middot;\u0026middot;\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro)(I), where they are in a \u003cem\u003ecis\u003c/em\u003e-arrangement. The NH\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e groups of A- and B-moieties form hydrogen bonds with the nearest oxygen atoms, but not with the triiodide anion, while there are five C-H\u0026middot;\u0026middot;\u0026middot;I type contacts (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). Some of them may be considered as weak hydrogen bonds. Notably, the triiodide anions in the structure of (\u003cb\u003eI\u003c/b\u003e) are not connected to each other by halogen bonds.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eHydrogen bond parameters (in \u0026Aring; and \u0026deg;) for (\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-ProH\u0026middot;\u0026middot;\u0026middot;\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro)(I\u003csub\u003e3\u003c/sub\u003e) (\u003cb\u003eI\u003c/b\u003e).\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eD-H\u0026middot;\u0026middot;\u0026middot;A\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eD-H\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eH\u0026middot;\u0026middot;\u0026middot;A\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eD\u0026middot;\u0026middot;\u0026middot;A\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eDHA\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eO1A-H1A\u0026middot;\u0026middot;\u0026middot;O1B\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.93\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.458(4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e166\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eN1A-H11A\u0026middot;\u0026middot;\u0026middot;O1B \u003csup\u003ei\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.91\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.90\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.783(4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e164\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eN1A-H12A\u0026middot;\u0026middot;\u0026middot;O2A\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.91\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2.24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.727(4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e113\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eN1A-H12A\u0026middot;\u0026middot;\u0026middot;O2B \u003csup\u003eii\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.91\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.869(4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e148\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eN1B-H11B\u0026middot;\u0026middot;\u0026middot;O1A \u003csup\u003eiii\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.91\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.99\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.865(4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e162\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eN1B-H12B\u0026middot;\u0026middot;\u0026middot;O1A\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.91\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.99\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.870(4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e162\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eN1B-H12B\u0026middot;\u0026middot;\u0026middot;O2A \u003csup\u003eiv\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.91\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2.08\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.865(4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e144\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eN1B-H12B\u0026middot;\u0026middot;\u0026middot;O2B\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.91\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2.19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.685(4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e113\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC3A-H31A\u0026middot;\u0026middot;\u0026middot;I2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.99\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3.06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e4.035(5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e169\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC3A-H32A\u0026middot;\u0026middot;\u0026middot;I1 \u003csup\u003ev\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.99\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2.94\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3.867(5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e157\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC4B-H42B\u0026middot;\u0026middot;\u0026middot;I3 \u003csup\u003evi\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.99\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3.07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e4.052(5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e170\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC5B-H51B\u0026middot;\u0026middot;\u0026middot;I2 \u003csup\u003evi\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.99\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3.15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3.993(5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e143\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC5B-H52B\u0026middot;\u0026middot;\u0026middot;I2 \u003csup\u003eiv\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.99\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3.14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3.975(5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e143\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003eSymmetry code: (i) -x\u0026thinsp;+\u0026thinsp;2, y-1/2, -z; (ii) x, y-1, z; (iii) -x\u0026thinsp;+\u0026thinsp;2, y\u0026thinsp;+\u0026thinsp;1/2, -z\u0026thinsp;+\u0026thinsp;1; (iv) x, y\u0026thinsp;+\u0026thinsp;1, z;\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e(v) -x\u0026thinsp;+\u0026thinsp;1, y\u0026thinsp;+\u0026thinsp;1/2, -z; (vi) -x\u0026thinsp;+\u0026thinsp;1, y\u0026thinsp;+\u0026thinsp;1/2, -z\u0026thinsp;+\u0026thinsp;1.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe salt [(\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-ProH)\u003csub\u003e3\u003c/sub\u003e(\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro)](I\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e (\u003cb\u003eII\u003c/b\u003e) also crystallizes in the monoclinic polar \u003cem\u003eP\u003c/em\u003e2\u003csub\u003e1\u003c/sub\u003e space group (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Selected bond lengths and angles are listed in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, while the geometric parameters of hydrogen bonds are provided in Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e. The salt (\u003cb\u003eII\u003c/b\u003e) with a formal composition of [(\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-ProH)\u003csub\u003e3\u003c/sub\u003e(\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro)](I\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e has an unusual structure. In Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e the molecular motif consisting of A-, B-, C-, and D-moieties is shown. The B- and C-moieties form a pseudocentrosymmetric dimer \u003cem\u003evia\u003c/em\u003e a very strong hydrogen bond O1C-H1C-O1B with an O\u0026middot;\u0026middot;\u0026middot;O distance of 2.427 \u0026Aring; (Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). The bond lengths C1C-O1C (1.274(4) \u0026Aring;) and C1B-O1B (1.270(4) \u0026Aring;) are alike within the error limits and are characteristic for dimers with very short O\u0026middot;\u0026middot;\u0026middot;O distances. This dimer, in turn, forms hydrogen bonds with cationic A- and D-moieties \u003cem\u003evia\u003c/em\u003e O1A-H1A\u0026middot;\u0026middot;\u0026middot;O2B and O1D-H1D\u0026middot;\u0026middot;\u0026middot;O2C hydrogen bonds (Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eBond lengths C1A-O1A, C1A-O2A and C1D-O1D, C1D-O2D (Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e) are characteristic for carboxylic groups. So, the cationic part in the structure of (\u003cb\u003eII\u003c/b\u003e) can be presented as a tetramer [\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-ProH\u0026middot;\u0026middot;\u0026middot;(\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro-H-\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro)\u0026middot;\u0026middot;\u0026middot;\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-ProH]\u003csup\u003e3+\u003c/sup\u003e which is balanced by three triiodide anions: (I1-I2-I3)\u003csup\u003e\u0026minus;\u003c/sup\u003e, (I4-I5-I6)\u003csup\u003e\u0026minus;\u003c/sup\u003e and (I7-I8-I9)\u003csup\u003e\u0026minus;\u003c/sup\u003e. The bond lengths and angles of triiodide anions are shown in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e. These three triiodide anions are connected to each other by supramolecular halogen bonds I3\u0026middot;\u0026middot;\u0026middot;I4 and I6\u0026middot;\u0026middot;\u0026middot;I7 (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). Although the average bond lengths (2.9203 \u0026Aring;, 2.9251 \u0026Aring;, 2.9241 \u0026Aring;, respectively) are similar to each other, it is worth noting that for the middle triiodide anion (I4-I5-I6)\u003csup\u003e\u0026minus;\u003c/sup\u003e surrounded on both sides, the bond lengths (2.9235 \u0026Aring; and 2.9268 \u0026Aring;) are closer than in the other two cases (Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eSelected bond lengths and angles (in \u0026Aring; and \u0026deg;) for [(\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-ProH)\u003csub\u003e3\u003c/sub\u003e(\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro)](I\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e (\u003cb\u003eII\u003c/b\u003e).\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBonds\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eA\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eB\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eC\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eD\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC1-O1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.304(5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.270(4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.274(4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.303(5)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC1-O2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.207(5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.231(5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.232(5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.209(5)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC1-C2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.512(5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.524(4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.525(4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.512(5)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC2-C3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.517(5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.540(5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.539(6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.520(5)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC3-C4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.530(5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.540(5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.529(5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.518(5)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC4-C5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.506(6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.516(6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.510(6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.507(6)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC5-N1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.509(5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.484(5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.494(5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.498(5)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eN1-C2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.502(5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.504(4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.501(5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.491(5)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eI1-I2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2.9757(4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eI4-I5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.9235(4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eI2-I3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2.8649(4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eI5-I6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.9268(4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eI7-I8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2.8535(4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eI3\u0026middot;\u0026middot;\u0026middot;I4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3.6663(6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eI8-I9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2.9948(4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eI6\u0026middot;\u0026middot;\u0026middot;I7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3.6146(6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eI1-I2-I3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e174.864(13)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eI2-I3\u0026middot;\u0026middot;\u0026middot;I4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e167.19(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eI4-I5-I6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e177.434(14)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eI3\u0026middot;\u0026middot;\u0026middot;I4-I5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e168.74(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eI7-I8-I9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e176.175(13)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eI5-I6\u0026middot;\u0026middot;\u0026middot;I7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e172.62(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eI6\u0026middot;\u0026middot;\u0026middot;I7-I8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e173.21(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe NH\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e groups form five N-H\u0026middot;\u0026middot;\u0026middot;I type hydrogen bonds with anions and two N-H\u0026middot;\u0026middot;\u0026middot;O type hydrogen bonds (excluding one intramolecular bond) with the carbonyl oxygen atoms O2A and O2D of neighboring A- and D- \u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-prolinium cations. Additionally, there are five C-H\u0026middot;\u0026middot;\u0026middot;I type short contacts that can be considered weak hydrogen bonds. All iodine atoms that form N-H\u0026middot;\u0026middot;\u0026middot;I and C-H\u0026middot;\u0026middot;\u0026middot;I contacts are terminal atoms of triiodide anions.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab5\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eHydrogen bond parameters (in \u0026Aring; and \u0026deg;) for [(\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-ProH)\u003csub\u003e3\u003c/sub\u003e(\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro)](I\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e (\u003cb\u003eII\u003c/b\u003e).\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eD-H\u0026middot;\u0026middot;\u0026middot;A\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eD-H\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eH\u0026middot;\u0026middot;\u0026middot;A\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eD\u0026middot;\u0026middot;\u0026middot;A\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eDHA\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eO1A-H1A\u0026middot;\u0026middot;\u0026middot;O2B \u003csup\u003ei\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.70(5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.97(5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.674(4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e173(7)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eO1C-H1C\u0026middot;\u0026middot;\u0026middot;O1B \u003csup\u003ei\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.427(3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e146\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eO1D-H1D\u0026middot;\u0026middot;\u0026middot;O2C \u003csup\u003eii\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.70(5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.99(5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.664(4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e162(6)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eN1A-H11A\u0026middot;\u0026middot;\u0026middot;O2A\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.91\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2.21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.692(4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e113\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eN1A-H12A\u0026middot;\u0026middot;\u0026middot;I1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.91\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2.82\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3.690(3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e147\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eN1B-H11B\u0026middot;\u0026middot;\u0026middot;O2A \u003csup\u003eiii\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.91\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2.03\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.818(4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e144\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eN1B-H12B\u0026middot;\u0026middot;\u0026middot;I4 \u003csup\u003eiii\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.91\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2.91\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3.690(3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e144\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eN1C-H11C\u0026middot;\u0026middot;\u0026middot;O2D \u003csup\u003eiv\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.91\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2.06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.836(4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e142\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eN1C-H12C\u0026middot;\u0026middot;\u0026middot;I6 \u003csup\u003ev\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.91\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2.93\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3.698(3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e143\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eN1D-H11D\u0026middot;\u0026middot;\u0026middot;I9 \u003csup\u003evi\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.91\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3.08\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3.856(4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e144\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eN1D-H12D\u0026middot;\u0026middot;\u0026middot;I9 \u003csup\u003eiii\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.91\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2.82\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3.638(4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e150\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC2A-H2A\u0026middot;\u0026middot;\u0026middot;I1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3.11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3.831(4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e130\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC3A-H31A\u0026middot;\u0026middot;\u0026middot;I7 \u003csup\u003eiii\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.99\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3.09\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3.844(5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e134\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC3A-H32A\u0026middot;\u0026middot;\u0026middot;I7 \u003csup\u003evi\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.99\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3.04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3.873(5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e143\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC2D-H2D\u0026middot;\u0026middot;\u0026middot;I3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3.12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3.953(4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e141\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC3D-H31D\u0026middot;\u0026middot;\u0026middot;I3 \u003csup\u003evi\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.99\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3.09\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3.821(5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e131\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003eSymmetry code: (i) x, y, z\u0026thinsp;+\u0026thinsp;1; (ii) x, y, z-1; (iii) -x\u0026thinsp;+\u0026thinsp;1, y-1/2, -z\u0026thinsp;+\u0026thinsp;1; (iv) -x\u0026thinsp;+\u0026thinsp;2, y-1/2, -z\u0026thinsp;+\u0026thinsp;1;\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e(v) -x\u0026thinsp;+\u0026thinsp;1, y-1/2, -z\u0026thinsp;+\u0026thinsp;2; (vi) -x\u0026thinsp;+\u0026thinsp;1, y\u0026thinsp;+\u0026thinsp;1/2, -z\u0026thinsp;+\u0026thinsp;1; (vii) x, y\u0026thinsp;+\u0026thinsp;1, z.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe infrared spectra of (\u003cb\u003eI\u003c/b\u003e) and (\u003cb\u003eII\u003c/b\u003e) are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e. A tentative assignment of peaks is given in Table\u0026nbsp;\u003cspan refid=\"Tab6\" class=\"InternalRef\"\u003e6\u003c/span\u003e.\u003c/p\u003e \u003cp\u003eIn the high-frequency region of (\u003cb\u003eI\u003c/b\u003e), one can expect absorptions caused by stretching modes of NH\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e, CH, and CH\u003csub\u003e2\u003c/sub\u003e groups. The stretching mode ν(OH) of the protonated A-moiety is assumed to be in the low-frequency region [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. The strong absorption band at 3123 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is assigned to ν(NH), while the peaks at 3004, 2975, and 2943 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e to ν(CH). The peak at 1707 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is characteristic for ν(C\u0026thinsp;=\u0026thinsp;O) of a carboxylic group, while the rather strong one at 1577 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is assigned to the deformation vibrations of NH\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e groups. Peaks at 1446, 1419, 1376, 1346, and 1321 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e are assigned to the deformation vibrations of CH\u003csub\u003e2\u003c/sub\u003e groups. The peak at 1419 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e may also be caused by ν\u003csub\u003es\u003c/sub\u003e(COO\u003csup\u003e\u0026minus;\u003c/sup\u003e). Those in the 1200\u0026thinsp;\u0026minus;\u0026thinsp;800 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e range are superimposed with a broad absorption centered \u003cem\u003eca\u003c/em\u003e. 990 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e which is likely caused by ν(OH) stretching mode (see [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn the high-frequency region of (\u003cb\u003eII\u003c/b\u003e), one can expect absorptions caused by stretching modes of NH\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e, CH, CH\u003csub\u003e2\u003c/sub\u003e groups as well as OH groups of carboxyl groups of A- and D- \u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-prolinium cations. The strong absorption band near 3000 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is assigned to ν(NH) of NH\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e (peak at 3133 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) and ν(OH) (the peak at 3075 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e). Expected values of ν(OH) based on the correlation ν(OH) \u003cem\u003evs\u003c/em\u003e. R(O\u0026middot;\u0026middot;\u0026middot;O) [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e] for hydrogen bonds O1A-H1A\u0026middot;\u0026middot;\u0026middot;O2B (2.674 \u0026Aring;) and O1D-H1D\u0026middot;\u0026middot;\u0026middot;O2C (2.664 \u0026Aring;) are close to the observed ones. Weak peaks at 3006, 2982, 2936 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e are assigned to ν(CH). The strong absorption band at 1715 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is characteristic for ν(C\u0026thinsp;=\u0026thinsp;O) of a carboxyl group. We assign it to ν(C\u0026thinsp;=\u0026thinsp;O) of the carboxyl groups of A- and D- \u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-prolinium cations. The position of weak absorption at 1653 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is characteristic for ν\u003csub\u003eas\u003c/sub\u003e(COO\u003csup\u003e\u0026minus;\u003c/sup\u003e). We assign it to the (\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro-H-\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro) dimeric cation. The weakness is likely caused by its pseudocentrosymmetric nature. The bands at 1552 and 1448 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e are also characteristic for proline and originated from δ(NH\u003csub\u003e2\u003c/sub\u003e) and δ(CH\u003csub\u003e2\u003c/sub\u003e), respectively. In the lower range there are peaks due to other deformation vibrations of CH\u003csub\u003e2\u003c/sub\u003e and NH\u003csub\u003e2\u003c/sub\u003e groups, as well as ring vibrations. The characteristic feature is also the absorption band at 1242 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, which we attribute to the ν(C-OH) of the carboxyl groups of A- and D- \u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-prolinium cations. More interesting is that these peaks are superimposed on half of the broad band in the 1400\u0026thinsp;\u0026minus;\u0026thinsp;500 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e region. Such a feature in this region is characteristic for ν(OH) of very strong hydrogen bonds in dimeric cations. We assign it to the ν(OH) of the (\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro-H-\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro) dimeric cation. For strong hydrogen bonds (R(O\u0026middot;\u0026middot;\u0026middot;O)\u0026thinsp;=\u0026thinsp;2.40\u0026ndash;2.58 \u0026Aring;) the correlation of ν(OH)(cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) \u003cem\u003evs\u003c/em\u003e. R(O\u0026middot;\u0026middot;\u0026middot;O) (\u0026Aring;) [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e] has approximately linear character: ν(OH)\u0026thinsp;=\u0026thinsp;12500R-29875. For R(O\u0026middot;\u0026middot;\u0026middot;O)\u0026thinsp;=\u0026thinsp;2.427 \u0026Aring; the expected value of ν(OH) is \u003cem\u003eca\u003c/em\u003e. 460 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, which corresponds well to the center of the mentioned broad band.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab6\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 6\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eWavenumbers (cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) and assignment of peaks in the infrared spectra of (\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-ProH\u0026middot;\u0026middot;\u0026middot;\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro)(I\u003csub\u003e3\u003c/sub\u003e) (\u003cb\u003eI\u003c/b\u003e) and [(\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-ProH)\u003csub\u003e3\u003c/sub\u003e(\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro)](I\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e (\u003cb\u003eII\u003c/b\u003e).\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003e(I)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e(II)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eAssignment\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3123\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3133\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eν(NH)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3075\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eν(OH)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3004;2975;2943\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3006;2982;2936\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eν(CH)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2880;2739;2553; 2448\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2875;2733\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eCombi\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1707\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1715\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eν(C\u0026thinsp;=\u0026thinsp;O)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1647\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1653\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eν\u003csub\u003eas\u003c/sub\u003e(COO\u003csup\u003e\u0026minus;\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1577\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1552\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eδ(NH\u003csub\u003e2\u003c/sub\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1446;1419\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1448\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eδ(CH\u003csub\u003e2\u003c/sub\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1376;1346\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1369\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eω(CH\u003csub\u003e2\u003c/sub\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1321\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1330\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eτ(CH\u003csub\u003e2\u003c/sub\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1300\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1306\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eτ(CH)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1279\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1282;1266\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eδ(CH)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1231\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1242\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eν(C-OH)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1188;1163\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1190;1169\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eω(NH\u003csub\u003e2\u003c/sub\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1081;1050;1024\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1088;1044\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e987; 919;860\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e987;950;921;900;860\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e788;765;722\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e754;737;662\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eDFT calculations of the electronic structure of (\u003cb\u003eI, II\u003c/b\u003e) crystals\u003c/p\u003e \u003cp\u003eThe grid parameters for calculating electronic properties were 3\u0026times;3\u0026times;2 (\u003cb\u003eI\u003c/b\u003e) and 2\u0026times;3\u0026times;1 (\u003cb\u003eII\u003c/b\u003e), k-point set in the Brillouin region for crystals. In a Kohn\u0026ndash;Sham computation, the approximate functional used to determine the exchange-correlation energy (\u0026#119864;\u0026#119909;\u0026#119888;) has a significant impact on the accuracy of the final findings. The electronic structure simulations were performed based on the DFT theory by OTFG (On-the-fly generation) ultrasoft pseudopotentials. The relativistic treatment was Koelling-Harmon, energy range \u0026ndash; 10 eV, separation compares 0.005 1/\u0026Aring;. Band energy tolerance is within 1.0 x 10\u003csup\u003e\u0026minus;5\u003c/sup\u003e eV per atom. The DOS and PDOS were calculated.\u003c/p\u003e \u003cp\u003eThe inhomogeneous electron densities in solids and the slow valence electron density fluctuations in space make using the generalized gradient approximation (GGA) in the PBE scheme for computing electronic characteristics an excellent method.\u003c/p\u003e \u003cp\u003eWe calculated the energy band structures with the directions with high first Brillouin zone equilibrium points, including Z\u0026rarr;G\u0026rarr;Y\u0026rarr;A\u0026rarr;B\u0026rarr;D\u0026rarr;E\u0026rarr;C for both (\u003cb\u003eI\u003c/b\u003e) and (\u003cb\u003eII\u003c/b\u003e) crystals. A direct transition energy for (\u003cb\u003eI, II)\u003c/b\u003e crystals, which appears between the highest valence band value and the lowest conduction band value of the Brillion region at the symmetry point B, is 2.281 eV (\u003cb\u003eI\u003c/b\u003e) and 1.641 eV (\u003cb\u003eII\u003c/b\u003e), and an indirect band gap at Y\u0026rarr;G range is 1.631 eV (\u003cb\u003eII)\u003c/b\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). For the (\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-ProH\u0026middot;\u0026middot;\u0026middot;\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro)(I\u003csub\u003e3\u003c/sub\u003e) (\u003cb\u003eI\u003c/b\u003e) crystal indirect transition was not observed.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAs is known, the density of states (DOS) of a system describes the number of states occupied at each energy level in statistical and solid-state physics. Composition of the calculated energy bands can be resolved with the help of partial density of states (PDOS) and total density of states (TDOS) diagrams.\u003c/p\u003e \u003cp\u003eFigures\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e and \u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e demonstrate the total density of states for the valence and conduction bands. In these figures, the zero tick mark on the energy scales (the top of the valence band) indicates the position of the Fermi level. To obtain a measure of the contribution of different atomic states to the band structure, as well as to their possible hybridizations, a comprehensive analysis of the partial density of states was carried out.\u003c/p\u003e \u003cp\u003eFrom the supercell calculations, the PDOS for the different elements O (2s\u003csup\u003e2\u003c/sup\u003e, 2p\u003csup\u003e4\u003c/sup\u003e), N (2s\u003csup\u003e2\u003c/sup\u003e, 2p\u003csup\u003e3\u003c/sup\u003e) and I (5s\u003csup\u003e2\u003c/sup\u003e 4d\u003csup\u003e10\u003c/sup\u003e 5p\u003csup\u003e5\u003c/sup\u003e) in the (\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-ProH\u0026middot;\u0026middot;\u0026middot;\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro)(I\u003csub\u003e3\u003c/sub\u003e) (\u003cb\u003eI\u003c/b\u003e) and [(\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-ProH)\u003csub\u003e3\u003c/sub\u003e(\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro)](I\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e (\u003cb\u003eII\u003c/b\u003e) crystals are extracted and shown in Figs.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e and \u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e. These diagrams allow us to conclude that the main contribution near the edge of the conduction band for both crystals is made by the I (5p) states, which hybridize with the N (2p) and O (2p) states. In the presence of states I (5p), the band gap for (\u003cb\u003eI\u003c/b\u003e) is E\u003csub\u003eg\u003c/sub\u003e = 2.281 eV, and for (\u003cb\u003eII\u003c/b\u003e) it is E\u003csub\u003eg\u003c/sub\u003e = 1.631 eV.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eSalt (\u003cb\u003eII\u003c/b\u003e) has a complicated composition [(\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-ProH)\u003csub\u003e3\u003c/sub\u003e(\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro)](I\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e containing a peculiar tetrameric cation [\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-ProH\u0026middot;\u0026middot;\u0026middot;(\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro-H- \u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro)\u0026middot;\u0026middot;\u0026middot;\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-ProH]. In addition, the presence of triiodide anions with their supramolecular halogen bonds leads to a decrease in the bandgap compared to the salt (\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-ProH\u0026middot;\u0026middot;\u0026middot;\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro)(I\u003csub\u003e3\u003c/sub\u003e) (\u003cb\u003eI\u003c/b\u003e).\u003c/p\u003e \u003cp\u003eBandgap measurements\u003c/p\u003e \u003cp\u003eThe type of transition selected based on DFT-calculations and the bandgap were estimated from the UV-Vis diffuse reflectance data (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e) using Tauc expression and Kubelka-Munk function [\u003cspan additionalcitationids=\"CR21\" citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. The bandgap for the direct transition (\u003cb\u003eI\u003c/b\u003e) is 2.04 eV while for the indirect one it is 1.51 eV (\u003cb\u003eII\u003c/b\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eTwo new crystalline salts were obtained: (\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-ProH\u0026middot;\u0026middot;\u0026middot;\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro)(I\u003csub\u003e3\u003c/sub\u003e) (\u003cb\u003eI\u003c/b\u003e) and [(\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-ProH)\u003csub\u003e3\u003c/sub\u003e(\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro)](I\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e (\u003cb\u003eII\u003c/b\u003e).\u003c/p\u003e \u003cp\u003eThe compound (\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-ProH\u0026middot;\u0026middot;\u0026middot;\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro)(I\u003csub\u003e3\u003c/sub\u003e) (\u003cb\u003eI\u003c/b\u003e) with a (\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-ProH\u0026middot;\u0026middot;\u0026middot;\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro) dimeric cation exhibits a short hydrogen bond with an O\u0026middot;\u0026middot;\u0026middot;O distance of 2.458(4) \u0026Aring;, which is close to the 2.454(2) \u0026Aring; observed in the structure of (\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-ProH\u0026middot;\u0026middot;\u0026middot;\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro)(I) [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. The salt [(\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-ProH)\u003csub\u003e3\u003c/sub\u003e(\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro)](I\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e (\u003cb\u003eII\u003c/b\u003e) shows an unusual structure with a peculiar tetrameric cation [\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-ProH\u0026middot;\u0026middot;\u0026middot;(\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro-H-\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro)\u0026middot;\u0026middot;\u0026middot;\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-ProH], where (\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro-H-\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro) is a pseudocentrosymmetric dimer with a very short hydrogen bond with an O\u0026middot;\u0026middot;\u0026middot;O distance of 2.427 \u0026Aring;. Three triiodide anions are connected I1-I2-I3\u0026middot;\u0026middot;\u0026middot;I4-I5-I6\u0026middot;\u0026middot;\u0026middot;I7-I8-I9 by halogen bonds I3\u0026middot;\u0026middot;\u0026middot;I4 and I6\u0026middot;\u0026middot;\u0026middot;I7, being 3.6663 \u0026Aring; and 3.6146 \u0026Aring;, respectively.\u003c/p\u003e \u003cp\u003eInfrared spectra of (\u003cb\u003eI\u003c/b\u003e, \u003cb\u003eII\u003c/b\u003e) were registered and interpreted based on their structures. The presence of short hydrogen bonds in dimeric cations is reflected in the spectra.\u003c/p\u003e \u003cp\u003eElectronic band structures were determined derived from crystal structures by quantum chemical calculations. The structure of the calculated energy bands was analyzed using partial density of states diagrams. The energies of the direct transition with a bandgap of E\u003csub\u003eg\u003c/sub\u003e = 2.281 eV for (\u003cb\u003eI\u003c/b\u003e) and the indirect transition with a bandgap of E\u003csub\u003eg\u003c/sub\u003e = 1.631 eV for (\u003cb\u003eII\u003c/b\u003e) have been determined. In addition, the bandgaps were measured from the diffuse reflectance spectra, which were equal to E\u003csub\u003eg\u003c/sub\u003e = 2.04 eV for (\u003cb\u003eI\u003c/b\u003e) and E\u003csub\u003eg\u003c/sub\u003e = 1.51 eV for (\u003cb\u003eII\u003c/b\u003e).\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe work was supported by the Science Committee of RA, in the frame of the research project\u003c/p\u003e\n\u003cp\u003e№ \u003cem\u003e\u003cu\u003e21AG-1D015\u003c/u\u003e.\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and material\u003c/strong\u003e Further crystallographic data have been deposited with the Cambridge Crystallographic Data Centre and can be obtained free of charge via www.ccdc.cam.ac.uk/conts/retrieving. html (or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax:+44 1223 336,033), citing the title of this paper and the CCDC nos. 2212285\u0026ndash;2212293. Code availability CCDC nos. 2281225 and 2281226.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCode availability\u003c/strong\u003e CCDC nos. 2281225 (\u003cstrong\u003eII\u003c/strong\u003e) and 2281226 (\u003cstrong\u003eI\u003c/strong\u003e)).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of interest\u003c/strong\u003e The authors declare no competing interests.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003ePer H, Svensson L, Kloo (2003) Synthesis, structure, and bonding in polyiodide and metal iodide-iodine systems. 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The Philosophical Magazine: A Journal of Theoretical Experimental and Applied Physics 22(issue179):0903\u0026ndash;0922. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1080/14786437008221061\u003c/span\u003e\u003cspan address=\"10.1080/14786437008221061\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"},{"header":"Supplementary Material","content":"\u003cp\u003eSupplementary Material is not available with this version\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"structural-chemistry","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"stuc","sideBox":"Learn more about [Structural Chemistry](https://www.springer.com/journal/11224)","snPcode":"11224","submissionUrl":"https://submission.nature.com/new-submission/11224/3","title":"Structural Chemistry","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Salts of l-proline, Polyiodides, Crystal structure, Dimeric cations, Electronic structure","lastPublishedDoi":"10.21203/rs.3.rs-3869782/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3869782/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eTwo new salts of \u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-proline containing triiodide anions were obtained and investigated: (\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-ProH\u0026middot;\u0026middot;\u0026middot;\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro)(I\u003csub\u003e3\u003c/sub\u003e) (I) and [(\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-ProH)\u003csub\u003e3\u003c/sub\u003e(\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro)](I\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e (II). Both compounds crystallize in the polar monoclinic space group \u003cem\u003eP\u003c/em\u003e2\u003csub\u003e1\u003c/sub\u003e. Crystal structure determinations showed that (I) contains a dimeric cation formed by an O-H\u0026middot;\u0026middot;\u0026middot;O hydrogen bond with an O\u0026middot;\u0026middot;\u0026middot;O distance of 2.458(4) \u0026Aring;, while (II) features a peculiar tetrameric cation [\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-ProH\u0026middot;\u0026middot;\u0026middot;(\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro-H-\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro)\u0026middot;\u0026middot;\u0026middot;\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-ProH], where (\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro-H-\u003cspan type=\"SmallCaps\" class=\"SmallCaps\" name=\"Emphasis\"\u003el\u003c/span\u003e-Pro) is a pseudocentrosymmetric dimer with a very short hydrogen bond with an O\u0026middot;\u0026middot;\u0026middot;O distance of 2.427 \u0026Aring;. Infrared spectra of both crystals were registered and interpreted based on their structures. Electronic band structures were determined by quantum chemical calculations. The CASTEP code was used to calculate the band structures, total and partial density of states (TDOS, PDOS). Bandgaps were also measured by the diffuse reflectance method.\u003c/p\u003e","manuscriptTitle":"Polyiodides of amino acids. L-Proline triiodides","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-01-25 19:07:18","doi":"10.21203/rs.3.rs-3869782/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Accepted","date":"2024-02-02T08:10:23+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-01-28T15:17:37+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"50fe95a6-4989-4605-880f-0e893c8c3119","date":"2024-01-23T18:26:22+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-01-23T07:45:32+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-01-23T07:41:17+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-01-23T03:36:01+00:00","index":"","fulltext":""},{"type":"submitted","content":"Structural Chemistry","date":"2024-01-16T12:30:14+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"structural-chemistry","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"stuc","sideBox":"Learn more about [Structural Chemistry](https://www.springer.com/journal/11224)","snPcode":"11224","submissionUrl":"https://submission.nature.com/new-submission/11224/3","title":"Structural Chemistry","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"181045b0-6a5e-453b-ac8d-70b238685c90","owner":[],"postedDate":"January 25th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2024-02-12T15:02:15+00:00","versionOfRecord":{"articleIdentity":"rs-3869782","link":"https://doi.org/10.1007/s11224-024-02291-8","journal":{"identity":"structural-chemistry","isVorOnly":false,"title":"Structural Chemistry"},"publishedOn":"2024-02-09 15:00:41","publishedOnDateReadable":"February 9th, 2024"},"versionCreatedAt":"2024-01-25 19:07:18","video":"","vorDoi":"10.1007/s11224-024-02291-8","vorDoiUrl":"https://doi.org/10.1007/s11224-024-02291-8","workflowStages":[]},"version":"v1","identity":"rs-3869782","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3869782","identity":"rs-3869782","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}