Analysis of the structure, thermal, and molecular dynamics of organic–inorganic hybrid [NH 2 (CH 3 ) 2 ] 2 CdBr 4 crystal at phases IV, III, II, and I

Analysis of the structure, thermal, and molecular dynamics of organic–inorganic hybrid [NH 2 (CH 3 ) 2 ] 2 CdBr 4 crystal at phases IV, III, II, and I | 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 Article Analysis of the structure, thermal, and molecular dynamics of organic–inorganic hybrid [NH 2 (CH 3 ) 2 ] 2 CdBr 4 crystal at phases IV, III, II, and I Sun Ha Kim, Young Lak Joo, Ae Ran Lim This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-2849469/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract A comprehensive understanding of the physicochemical properties of organic–inorganic hybrids is essential for their application. Therefore, a single crystal of [NH 2 (CH 3 ) 2 ] 2 CdBr 4 was grown; the crystal structure was monoclinic, and the phase transition temperatures for the four phases IV, III, II, and I were 383 K (T C1 ), 417 K (T C2 ), and 427 K (T C3 ). Furthermore, the chemical shifts caused by the local field around 1 H, 13 C, 14 N, and 113 Cd changed continuously with temperature, especially near T C1 , indicating that the local environment changes with temperature. Owing to the large change in 113 Cd chemical shifts, the coordination geometry of Br around Cd in the CdBr 4 tetrahedra changes near T C1 . Therefore, it is thought that Br plays a significant role in the N‒H···Br hydrogen bond. Finally, the spin-lattice relaxation time T 1ρ , representing the energy transfer around the 1 H and 13 C atoms of the cation, changed significantly with temperature. The activation energies obtained from the T 1ρ results were two times larger at high temperatures than at low temperatures. This study provides an understanding of the fundamental properties of organic–inorganic hybrid compounds to broaden their applications. Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Introduction Organic–inorganic hybrid compounds are of great interest for various applications such as sensors, fuel cells, solar cells, light-emitting transistors, and light-emitting diodes. 1-4 Additionally, organic–inorganic hybrid perovskite materials are applied in ferroelectrics, dielectric switches, and optical switches. 5-11 Recently, CH 3 NH 3 Pb X 3 ( X = Cl, Br, I) has been used for solar cells, but these materials are easily degraded in humid air and are toxic because of the presence of Pb. Therefore, the development of eco-friendly hybrid perovskite solar cells is urgently required. 12-16 As new alternatives, two-dimensional compounds such as [NH 3 (CH 2 ) n NH 3 ] MX 4 ( n = 1, 2, 3, ∙∙∙; M 2+ = divalent transition metal, Mn, Co, Cu, Zn, Cd, or Pb; X = halogen, Cl, Br, or I) 17-28 and [(C n H 2 n +1 NH 3 )] 2 MX 4 are examples of organic–inorganic hybrids that have recently attracted considerable attention. 29-37 Moreover, it is necessary to study the hydrogen bond structure of [NH 2 (CH 3 ) n ] 2 MX 4 , 38-44 which is different than that of [NH 3 (CH 2 ) n NH 3 ] MX 4 with three H atoms bonded to one N. One of these alternatives, dimethylammonium tetrabromocadmate (II), [NH 2 (CH 3 ) 2 ] 2 CdBr 4 , 38, 39 is a member of [NH 2 (CH 3 ) n ] 2 MX 4 , which belongs to the A 2 MX 4 group, where A + is a univalent cation. These crystals undergo several structural phase transitions, which are commonly associated with the ordering of hydrogen bonds and the corresponding changes in the molecular dynamics of [NH 2 (CH 3 ) 2 ] + ions. The individual MX 4 tetrahedral anions in these materials are completely isolated and surrounded by organic [NH 2 (CH 3 ) 2 ] + cations. These substances are expected to function as proton conductors via hydrogen bonding. [NH 2 (CH 3 ) 2 ] 2 CdBr 4 was demonstrated to undergo three structural phase transitions at 380, 413, and 426 K. 39 At 300 K, the [NH 2 (CH 3 ) 2 ] 2 CdBr 4 crystal exhibited a monoclinic structure with a P2 1 /n space group and its lattice constants were a = 8.158 Å, b = 11.632 Å, c = 15.166 Å, β = 94.82°, and Z = 4. 38 The structure consisted of [CdBr 4 ] 2+ anions and nonequivalent [NH 2 (CH 3 ) 2 ](1) and [NH 2 (CH 3 ) 2 ](2) cations. The structure comprised infinite chains of face-sharing CdBr 4 tetrahedra with the [NH 2 (CH 3 ) 2 ] + ions located in the free space between the chains. Notably, the slightly deformed CdBr 4 tetrahedra were linked to organic [NH 2 (CH 3 ) 2 ] cations via N-H∙∙∙Br hydrogen bonds. 38 In this study, single crystals of [NH 2 (CH 3 ) 2 ] 2 CdBr 4 are grown using an aqueous solution method, and their structures and phase transition temperatures (T C ) are characterized using single-crystal X-ray diffraction (XRD), powder XRD, and differential scanning calorimetry (DSC). Additionally, thermogravimetry analysis (TGA) is performed to gain a better understanding of the thermal properties of the samples. To characterize the coordination geometry of the 1 H, 13 C, 14 N, and 113 Cd atoms in the samples, 1 H magic-angle spinning nuclear magnetic resonance (MAS NMR), 13 C MAS NMR, 14 N static NMR, and 113 Cd static NMR chemical shifts are obtained as a function of temperature. Based on the results, the N‒H∙∙∙Br hydrogen bond between the cation and anion is discussed. Moreover, 1 H and 13 C spin-lattice relaxation times T 1 ρ representing the energy transfer around the 1 H and 13 C atoms of the cation are discussed, and their activation energies E a are determined. The results of the single-crystal structure and physicochemical properties are predicted to provide important information on the fundamental mechanism of organic-inorganic hybrid compounds. Methods Crystal growth Single crystals of [NH 2 (CH 3 ) 2 ] 2 CdBr 4 were synthesized using dimethylammonium bromide (Aldrich, 98 %) and CdBr 2 ∙4H 2 O (Aldrich, 98 %) in a ratio of 2:1. The mixture was stirred and heated to obtain a homogeneous solution. Subsequently, the mixture was filtered through a filter paper, and transparent colorless single crystals were grown by gradual evaporation for a few days in a temperature-controlled oven at 300 K. Characterization The structure and lattice parameters of the [NH 2 (CH 3 ) 2 ] 2 CdBr 4 crystal were determined at 300 K using a single-crystal XRD system at the Korea Basic Science Institute (KBSI) Western Seoul Center. Powder XRD patterns were measured at several temperatures at the same facility. The experimental conditions for the two XRD measurements are described in previously reported results. 45 DSC measurements were performed on a DSC instrument (TA Instruments, DSC 25) in the temperature range of 200–573 K at a heating rate of 10 K/min under nitrogen gas flow. The amount of sample used in the DSC experiment was 6.3 mg . Additionally, TGA was performed in the temperature range of 300–873 K at a heating rate of 10 K/min under nitrogen gas flow. The MAS NMR chemical shifts and spin-lattice relaxation time T 1ρ of the [NH 2 (CH 3 ) 2 ] 2 CdBr 4 crystals were measured using a solid-state NMR spectrometer (AVANCE III+, Bruker) at the KBSI Western Seoul Center. The Larmor frequency for the 1 H NMR experiment was 400.13 MHz, and that for the 13 C NMR experiment was 100.61 MHz. MAS NMR measurements of the samples in cylindrical zirconia rotors were performed at a spinning rate of 10 kHz to reduce the spinning sideband. Chemical shifts were referenced to standard materials adamantane and tetramethylsilane (TMS) for 1 H and 13 C, respectively, to accurately measure the chemical shifts of the samples. T 1ρ values were measured using a π/2− τ pulse with a spin-lock pulse of duration τ. Static 14 N NMR chemical shifts were recorded using the one-pulse method at a Larmor frequency of 28.90 MHz, NH 4 NO 3 was used as the standard sample. Furthermore, static 113 Cd NMR chemical shifts were measured at a Larmor frequency of 88.75 MHz, and the chemical shift of CdCl 2 O 8 ·6H 2 O was used as the standard sample. Experimental results Crystal structure Single-crystal XRD results for the [NH 2 (CH 3 ) 2 ] 2 CdBr 4 crystal were obtained at 300 K. The synthesized crystal had a monoclinic system with a P2 1 /n space group, and lattice constants of a = 8.2528 (9) Å, b = 11.7833 (14) Å, c = 15.3589 (18) Å, β = 94.726°, Z = 4. These results are consistent with those previously reported. 38 Fig. 1 shows the thermal ellipsoids and atomic numbering for each atom, and the XRD data for the [NH 2 (CH 3 ) 2 ] 2 CdBr 4 crystal are listed in Table 1 . This compound is characterized by the N‒H∙∙∙Br hydrogen bonds connecting the two types of nonequivalent [NH 2 (CH 3 ) 2 ](1) and [NH 2 (CH 3 ) 2 ](2) cations to the [CdBr 4 ] anion. The average bond length for Cd-Br was 2.5815 Å, and those for nonequivalent N(1)-C and N(2)-C were 1.466 and 1.473 Å, respectively. Table 1 Crystal data and structure refinement for [NH 2 (CH 3 ) 2 ] 2 CdBr 4 at 300 K. Chemical formula C 4 H 16 N 2 CdBr 4 Weight 524.23 Crystal system Monoclinic Space group P2 1 /n T (K) 300 a (Å) 8.2528 (9) b (Å) 11.7833 (14) c (Å) β (°) 15.3589 (18) 94.726 (4) Z 4 V (Å 3 ) 1488.5 Radiation type Mo-Kα Wavelength (Å) 0.71073 Reflections collected 27266 Independent reflections 3667 ( R int = 0.0487) Goodness-of-fit on F 2 1.033 Final R indices [I > 2sigma(I)] R 1 = 0.0313, wR 2 = 0.0593 R indices (all data) R 1 = 0.0499, wR 2 = 0.0648 Phase transition temperatures Figure 2 shows two strong endothermic peaks at 383 and 439 K with enthalpies of 12.93 and 17.14 kJ/mol, respectively. A weak endothermic peak was observed at 427 K with an enthalpy of 3.21 kJ/mol. Additionally, a minor peak with an enthalpy of 79 J/mol was observed at 417 K near the 427 K peak, as shown in the magnified inset in Fig. 2 . Starting at 200 K, these four phases are denoted as phase IV (below 383 K), phase III (between 383 and 417 K), phase II (between 417 and 427 K), and phase I (above 427 K). To determine whether these four endothermic peaks represent the phase transition or melting temperatures, the changes in the single crystal with increasing temperature were observed using an optical polarizing microscope. Up to 430 K, the single crystal remained almost unchanged, but the surface of the single crystal started to melt above 439 K. Additionally, powder XRD experiments were performed with increasing temperature in the measurement range of 5°–65° (2θ), as shown in Fig. 3 . The XRD powder patterns recorded below 380 K (black) differed from those recorded above 390 K (red). This difference is related to the structural phase transition at T C1 (383 K). Furthermore, the XRD patterns recorded above 390 K differed from those recorded at 420 K (blue). Moreover, the XRD pattern recorded at 420 K differed from that obtained at 430 K (olive), exhibiting a distinct change. Finally, the pattern at 450 K was completely different from those at temperatures below 450 K, and no crystallinity was observed, indicating that it is the melting point. The phase transition and melting temperatures determined by the powder XRD and optical polarizing microscope results are consistent with the endothermic peaks obtained from the DSC curves. Therefore, based on the DSC, XRD, and polarizing microscopy results, the phase transition temperatures are T C1 = 383 K, T C2 = 417 K, and T C3 = 427 K, and the melting temperature is T m = 439 K. Thermal property The TGA curve of the [NH 2 (CH 3 ) 2 ] 2 CdBr 4 crystal with increasing temperature is shown in Fig. 4 . The partial decomposition temperature was observed at 547 K, corresponding to a weight loss of 2%. Therefore, this material is thermally stable up to 547 K. The molecular weight of the [NH 2 (CH 3 ) 2 ] 2 CdBr 4 crystal decreased rapidly as the temperature increased owing to partial decomposition. From the total molecular weight of 524.23 mg, the amounts remaining after partial decomposition of HBr and 2HBr were obtained using the TGA data and the following chemical reactions. 46 {[NH(CH 3 ) 2 ] 2 HBr∙CdBr 2 (s) + HBr(g)}/[NH 2 (CH 3 ) 2 ] 2 CdBr 4 = 84.56% (1) {[NH(CH 3 ) 2 ] 2 CdBr 2 (s) + 2HBr(g)}/[NH 2 (CH 3 ) 2 ] 2 CdBr 4 = 69.13% (2) Molecular-weight losses of 25% and 31% were observed after decomposition of HBr and 2HBr, respectively. The initial weight loss (25%) occurred in the temperature range of 550–600 K, and the second decomposition (31%) occurred in the temperature range of 623 K. In contrast, three endothermic peaks were observed at 383, 425, and 438 K in the differential thermal analysis (DTA) curve, which is the differential form of the TGA curve, and are in good agreement with the phase transition and melting temperatures determined by DSC. The large endothermic peak observed near 623 K is in good agreement with the 2HBr decomposition temperature calculated from the total weight of the crystal. Moreover, total weight loss occurred at temperatures above 800 K. 1 H and 13 C MAS NMR chemical shifts The in situ NMR chemical shifts for 1 H in the [NH 2 (CH 3 ) 2 ] 2 CdBr 4 crystal were recorded for phases IV, III, and II, as shown in Fig. 5 . For phase IV, the 1 H NMR signals of NH 2 and CH 3 completely overlapped, and only one signal was obtained. The sidebands in the 1 H spectrum for phase IV are represented by open circles. The 1 H chemical shifts barely changed as the temperature increased, whereas the 1 H signals of NH 2 and CH 3 for phase III began to separate. The 1 H coordination geometry for NH 2 changed near T C1 . These results indicate that the 1 H coordination geometry for CH 3 remains unchanged with increasing temperature, whereas that for NH 2 changes. Conversely, the full width at half maximum of the 1 H NMR signal decreased with increasing temperature, as shown in detail in Fig. 5 . The linewidth of the 1 H NMR signal decreased from approximately 7 to 1 ppm as the temperature increased and showed a distinct decrease at T C2 , similar to the change in 1 H chemical shifts. This trend indicates that the mobility of 1 H becomes very active at high temperatures. Additionally, the in situ 13 C NMR chemical shifts in [NH 2 (CH 3 ) 2 ] 2 CdBr 4 were measured for phases IV, III, and II with increasing temperature, as shown in Fig. 6 . Only one 13 C signal was observed for the two CH 3 groups in the crystal structure; thus, the structural environments for these two CH 3 groups are identical. The 13 C NMR chemical shift obtained at 300 K was observed at 37.84 ppm. The chemical shifts for phases IV and III shifted in the positive direction, and the 13 C chemical shifts discontinuously changed near T C1 , similar to the 1 H NMR results. The linewidths shown in the inset in Fig. 6 were very small compared to the 1 H linewidths, and the linewidths decreased with increasing temperature but remained almost constant at temperatures above 280 K. Static 14 N and 113 Cd NMR chemical shifts The static NMR spectrum for 14 N in NH 2 at the center of the cation in the [NH 2 (CH 3 ) 2 ] 2 CdBr 4 single crystal is shown in Fig. 7 . NMR spectra were obtained in the temperature range of 180–380 K, and the direction of the magnetic field and single crystal were measured in an arbitrary direction. The spin number of 14 N is I = 1, and therefore two resonance signals were expected owing to the quadrupole interaction [47]. Notably, it was very difficult to obtain 14 N NMR spectra owing to the low Larmor frequency. Because the intensity was very weak and the linewidth was broad, it was difficult to obtain the 14 N NMR signals, as shown in Fig. 7 . The [NH 2 (CH 3 ) 2 ] 2 CdBr 4 structure consists of complex [CdBr 4 ] anions, and [NH 2 (CH 3 ) 2 ](1) and [NH 2 (CH 3 ) 2 ](2) cations. The structural properties of N(1) and N(2) in the two [NH 2 (CH 3 ) 2 ] + groups were determined based on the 14 N NMR chemical shifts. The chemical shifts of the 14 N NMR spectra obtained at several temperatures are shown in Fig. 7 . The N(1) chemical shifts represented by red squares decreased with increasing temperature, whereas the N(2) chemical shifts represented by blue circles slightly increased. The pairs for 14 N are indicated by the same symbols, and N(1) and N(2) were arbitrarily named. The linewidth at 300 K was very broad at approximately 80 ppm. However, 14 N signals were not easily detected at temperatures near T C1 . The two groups of 14 N signals demonstrate the presence of two nonequivalent N sites. Additionally, it was confirmed that there were different N(1) and N(2) sites, as shown in the single-crystal XRD results. The continuous change in the N(1) and N(2) chemical shifts with increasing temperature indicates a change in the coordination geometry of the local environment of N. Based on information obtained from 113 Cd chemical shifts, the changes in the structural environment around Cd in the anion CdBr 4 were evaluated. The spin number of 113 Cd is I = 1/2, and therefore only one resonance signal was expected. 47 The static 113 Cd NMR chemical shifts of the three phases are shown in Fig. 8 . The chemical shift of 113 Cd at 300 K was 386.93 ppm, and the linewidth was broad at approximately 30 ppm. 113 Cd NMR spectra measured at 180 and 420 K are shown in the inset in Fig. 8 . The linewidth at 180 K was much wider than that at 420 K, indicating that the mobility of Cd increases with increasing temperature. In contrast to the 1 H and 13 C chemical shifts, the 113 Cd chemical shifts continuously changed toward negative values, and the chemical shifts near T C1 showed discontinuous variation. Based on these results, it is proposed that the change in Br closest to Cd is large. 1 H and 13 C NMR spin-lattice relaxation times To obtain the spin-lattice relaxation time T 1ρ , the intensities of the NMR signals in the 1 H and 13 C NMR spectra were measured with increasing delay times. The decay curves of the change in the signal intensities and delay times are expressed by the following equation: 45, 47, 48 I( t ) = I(0)exp(‒ t /T 1ρ ), (3) where I( t ) is the intensity of the spectrum at time t and I(0) is the intensity of the spectrum at time t = 0. The T 1ρ values for 1 H and 13 C in [NH 2 (CH 3 ) 2 ] 2 CdBr 4 were obtained using Eq. (3), and the results are shown in Figs. 9 and 10 as a function of inverse temperature. The chemical shifts for 1 H in NH 2 and CH 3 were almost independent of temperature, but the T 1ρ values were strongly dependent on temperature. As the temperature increased, T 1ρ rapidly decreased, exhibiting a minimum value of 1.95 ms at 230 K and a second minimum value of 2.74 ms at 310 K. Additionally, T 1ρ was rapidly decreased at temperatures above T C1 and then rapidly increased at temperatures above T C3 . The T 1ρ values of 1 H have two minima at 230 and 310 K, indicating molecular motion according to the Bloembergen–Purcell–Pound (BPP) theory. These T 1ρ minima are attributable to the reorientational motion of 1 H in NH 2 and CH 3 . Therefore, the experimental value of T 1ρ can be expressed by the correlation time τ C for molecular motion, where the τ C value is determined as follows: 45, 47 (1/T 1ρ ) = R{4τ C /[1 + ω 1 2 τ C 2 ] + τ C /[1 + (ω C ‒ ω H ) 2 τ C 2 ] + 3τ C /[1 + ω C 2 τ C 2 ] + 6τ C /[1 + (ω C + ω H ) 2 τ C 2 ] + 6τ C /[1 + ω H 2 τ C 2 ]}, (4) where R is a constant, ω 1 is the spin-lock field, and ω C and ω H are the Larmor frequencies for carbon and protons, respectively. The data were analyzed by assuming that T 1ρ had the lowest value when ω 1 τ C = 1, and the relationship between T 1ρ and the radio frequency power of the spin-lock pulse ω 1 was applicable. Because the T 1ρ curves exhibited minima, the coefficient R in Eq. (4) can be obtained. Based on the obtained value for R, the τ C values were calculated as a function of temperature. The local field fluctuation is owing to the thermal motion of protons and carbon atoms, which are activated by thermal energy. The τ C of motion is generally assumed to have Arrhenius dependence on the activation energy for motion and temperature. 45, 47 τ C = τ C o exp(‒E a /k B T), (5) where E a and k B are the activation energy of motion and the Boltzmann constant, respectively. The magnitude of E a depends on the molecular dynamics. To determine the molecular dynamics, the logarithmic scale of τ C represented by red circles as a function of 1000/T is shown in Fig. 9 . Based on the slopes of the dotted lines at low and high temperatures for phase IV, E a was found to be 31.78 ± 3.41 and 27.88 ± 2.45 kJ/mol, respectively. Additionally, the E a obtained from the slope of T 1ρ as a function of inverse temperature for phase III was 72.12 ± 0.84 kJ/mol. Therefore, the difference in E a between phases IV and III near T C1 was very large. For 13 C, the T 1ρ values shown in Fig. 10 changed significantly at the phase transition temperature of T C1 . As the temperature increased, T 1ρ exhibited a small minimum value of 18.22 ms at 190 K, a second minimum value of 13.18 ms at 260 K, and a third minimum value of 71.49 ms at 340 K. Moreover, T 1ρ was rapidly shortened at temperatures above T C1 . The T 1ρ values of 13 C exhibited three minima at 190, 260, and 340 K, indicating molecular motion occurs according to the BPP theory. These minimum values of T 1ρ are clearly attributable to the reorientational motion of 13 C in CH 3 . The experimental values of T 1ρ were expressed in terms of the τ C . The logarithmic scale of τ C represented by blue squares as a function of 1000/T is shown in Fig. 10 . Based on the slopes of the dotted line at low and high temperatures for phase IV, E a was found to be 18.22 ± 3.41, 21.07 ± 2.45, and 28.78 kJ/mol, respectively. Additionally, the E a obtained from the slope of T 1ρ as a function of inverse temperature for phase III was 55.66 ± 0.84 kJ/mol. Therefore, the difference in E a between phases IV and III near T C1 was very large, which is similar to the 1 H results. Conclusion The physicochemical properties of the organic–inorganic hybrid [NH 2 (CH 3 ) 2 ] 2 CdBr 4 crystal are discussed. First, the monoclinic structure of this crystal was confirmed by single-crystal XRD, and the three-phase transition temperatures of 383, 417, and 427 K were determined using DSC and powder XRD analyses. This crystal had a good thermal stability of approximately 547 K, and weight loss was observed with increasing temperature owing to thermal decomposition, which resulted in the loss of HBr and 2HBr moieties. Second, the chemical shifts were caused by the local field around the resonating nucleus. Moreover, the 1 H, 13 C, 14 N, and 113 Cd NMR chemical shifts changed continuously with temperature, especially at T C1 , suggesting that the local environment changed with temperature. Owing to the large change in 113 Cd chemical shifts, the coordination geometry of Br around Cd in CdBr 4 tetrahedra changes near T C1 . Therefore, it is proposed that Br plays an important role in the N‒H···Br hydrogen bond. Finally, 1 H T 1ρ and 13 C T 1ρ values, which represent the energy transfer around the 1 H and 13 C atoms of the cation, changed significantly with temperature, indicating that the T 1ρ values for 1 H and 13 C are governed by tumbling motions. The activation energies derived from the results of the NMR T 1ρ experiments for molecular motion were very high at high temperatures. Based on the basic mechanism obtained for the [NH 2 (CH 3 ) 2 ] 2 CdBr 4 crystal, it is expected that the application of this organic–inorganic material is possible. Declarations Data availability The datasets generated and/or analysed during the current study are available in the CCDC 2256555. For ESI and crystallographic data in CIF or other electronic format see https://doi.org/. Acknowledgments This work was supported by the National Research Foundation of Korea (NRF) grant, funded by the Korea government (MSIT) (2023R1A2C2006333). The work was supported by the Basic Science Research program of the National Research Foundation of Korea (NRF), funded by the Ministry of Education, Science and Technology (2016R1A6A1A03012069). Author contributions A.R. Lim. designed the project, XRD experiments, and wrote the manuscript. S.H. 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Nonlinear magnetic-susceptibility of two-dimensional magnets (C n H 2 n +1 NH 3 ) 2 CuCl 4 with n =1, 2 and 3. J. Phys. Soc. Jpn . 65 , 4054 (1996). Mitzi, D. B. Templating and structural engineering in organic–inorganic perovskites. J. Chem. Soc. Dalton Trans . 1 , 1 (2001). Pradeesh, K., Baumberg, J. J., Vijaya Prakash, G. Exciton switching and Peierls transitions in hybrid inorganic-organic self-assembled quantum wells. Appl. Phys. Lett . 95 , 173305 (2009). Cheng, Z., Lin, J. Layered organic–inorganic hybrid perovskites: structure, optical properties, film preparation, patterning and templating engineering. Cryst. Eng. Com . 12 , 2646 (2010). Ahmad, S., Hanmandlu, C., Kanaujia, P. K., Vijaya Prakash, G. Direct deposition strategy for highly ordered inorganic organic perovskite thin films and their optoelectronic applications. Opt. Mater. Express 4 , 1313 (2014). Gonzalez-Carrero, S., Galian, R. E., Perez-Prieto, J. Organometal halide perovskites: bulk low-dimension materials and nanoparticles. Part. Syst. Charact . 32 , 709 (2015). Czapla, Z., Przeslawski, J., Crofton, M., Janczak, J., Czupinski, O., Ingram, A., Kostrzewa, M. Structural phase transition in a perovskite-type NH 3 (CH 2 ) 3 NH 3 CuCl 4 crystal – X-ray and optical studies. Phase Transitions 90 , 637 (2017). Abdel-Adal, S. K., Kocher-Oberlehner, G., Ionov, A., Mozhchil, R. N. Effect of organic chain length on structure, electronic composition, lattice potential energy, and optical properties of 2D hybrid perovskites [(NH 3 )(CH 2 ) n (NH 3 )]CuCl 4 , n = 2–9. Appl. Phys . A 123 , 531 (2017). Lim, A. R. Physicochemical properties of the cation in organic–inorganic perovskite [NH 3 (CH 2 ) 4 (NH 3 )]ZnBr 4 crystals investigated using 1 H and 13 C nuclear magnetic resonance relaxation. J. Solid State Chem. 302 , 122438 (2021). Waskowska, A. Crystal structure of dimethylammonium tetrabromocadmate (II). Zeit. Kristallogr . 209 , 752 (1994) Horiuchi, K., Ishihara, H., Terao, H. Differential scanning calorimetry studies on structural phase transitions and molecular motions in (CH 3 NH 3 ) 2 MBr 4 and [(CH 3 ) 2 NH 2 ] 2 MBr 4 (M = Zn, Cd, and Hg). J. Phys.: Condens. Matter 12 , 4799 (2000). Kim, N. H., Choi, J. H., Lim, A. R. Tumbling motions of NH 2 (CH 3 ) 2 ions in [NH 2 (CH 3 ) 2 ] 2 ZnCl 4 studied using 1 H MAS NMR and 13 C CP/MAS NMR. Solid State Sciences 38 , 103 (2014) Lim, A. R., Paik, Y. Investigating the two inequivalent NH 2 (CH 3 ) 2 ions in [NH 2 (CH 3 ) 2 ] 2 CuCl 4 using magic angle spinning nuclear magnetic resonance. Solid State Sciences 65 , 61 (2017). Mahfoudh, N., Karoui, K., Gargouri, M., BenRhaiem, A. Optical and electrical properties and conduction mechanism of [(CH 3 ) 2 NH 2 ] 2 CoCl 4 . Appl. Organometal Chem . 34 , e5404 (2020). Mahfoudh, N., Karoui, K., Jomni, F., BenRhaiem, A. Structural phase transition, thermal analysis, and spectroscopic studies in an organic–inorganic hybrid crystal: [(CH 3 ) 2 NH 2 ] 2 ZnBr 4 . Appl. Organometal Chem . 34 , e5656 (2020). Mahfoudh, N., Karoui, K., BenRhaiem, A. Optical studies and dielectric response of [DMA] 2 MCl 4 (M = Zn and Co) and [DMA] 2 ZnBr 4 . RSC Advances , 11 , 24526 (2021). Lim, A. R., Cho, J. Growth, structure, phase transition, thermal properties, and structural dynamics of organic-inorganic hybrid [NH 3 (CH 2 ) 5 NH 3 ]ZnCl 4 crystal. Sci. Rep. 12 ,16901 (2022). Lim, A. R., Kim, S. H., Joo, Y. L. Physicochemical properties and structural dynamics of organic– inorganic hybrid [NH 3 (CH 2 ) 3 NH 3 ]ZnX 4 (X = Cl and Br) crystals. Sci. Rep . 11 , 8408 (2021). Abragam, A. The Principles of Nuclear Magnetism (Oxford University Press, 1961). Harris, R. K. Nuclear Magnetic Resonance Spectroscopy (Pitman Pub, 1983). Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted 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. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-2849469","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":195244161,"identity":"68c1cbf8-8408-49f2-8bef-3a554e4ee073","order_by":0,"name":"Sun Ha Kim","email":"","orcid":"","institution":"Korea Basic Science Institute","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Sun","middleName":"Ha","lastName":"Kim","suffix":""},{"id":195244162,"identity":"c0bff3e6-8019-4e2e-9fe7-a383d5034aa7","order_by":1,"name":"Young Lak Joo","email":"","orcid":"","institution":"Cornell University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Young","middleName":"Lak","lastName":"Joo","suffix":""},{"id":195244163,"identity":"e43c68f8-bbd8-48c1-a1a2-9d019c9566cb","order_by":2,"name":"Ae Ran Lim","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAArUlEQVRIiWNgGAWjYFAC5oYDDBVszCAmYwNxWhiBWs6QqoWBsQ3OJALwzz7YeOjmPD52BvbDDxhn7iFCi8S5xIbDuduADuNJM2Dc8IwYa84wQrUw5DAwPjhAhA55sJY5QC38b4jUYgDW0gDUIgG0ZQMxWgxBWnKOsTGzSTwzODiDGC1yZ5gPf86pOZbMz5/88GEPMVqg4FgyG5AkQQMDQ40dKapHwSgYBaNghAEATgA1lU/rPNYAAAAASUVORK5CYII=","orcid":"","institution":"Jeonju University","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Ae","middleName":"Ran","lastName":"Lim","suffix":""}],"badges":[],"createdAt":"2023-04-22 22:59:11","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-2849469/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-2849469/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":36438684,"identity":"34f5ddc3-6c04-4191-80db-a506e02e61dd","added_by":"auto","created_at":"2023-04-28 17:06:22","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":202417,"visible":true,"origin":"","legend":"\u003cp\u003eCrystal structure of [NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e2\u003c/sub\u003eCdBr\u003csub\u003e4\u003c/sub\u003e at 300 K.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-2849469/v1/334f58117c1eaa0944cf0775.png"},{"id":36439256,"identity":"c7530701-8924-44a5-adb1-e6d9ecd25ea8","added_by":"auto","created_at":"2023-04-28 17:22:22","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":142962,"visible":true,"origin":"","legend":"\u003cp\u003eDifferential scanning calorimetry curve of [NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e2\u003c/sub\u003eCdBr\u003csub\u003e4\u003c/sub\u003e measured at a heating rate of 10°C/min.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-2849469/v1/00ba67b5d90885fe7b80f0ce.png"},{"id":36438979,"identity":"0032d58f-ee54-4734-a8d6-451762b151cf","added_by":"auto","created_at":"2023-04-28 17:14:22","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":272347,"visible":true,"origin":"","legend":"\u003cp\u003ePowder X-ray diffraction patterns of [NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e2\u003c/sub\u003eCdBr\u003csub\u003e4\u003c/sub\u003e at phases IV, III, II, and I. XRD pattern of 450 K is for the melting temperature.\u0026nbsp;\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-2849469/v1/09ef7762a1b434ce0671b289.png"},{"id":36438683,"identity":"f81a32ab-d552-4690-89d1-3781eaf840f7","added_by":"auto","created_at":"2023-04-28 17:06:22","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":109542,"visible":true,"origin":"","legend":"\u003cp\u003eThermogravimetric analysis and differential thermal analysis curves of [NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e2\u003c/sub\u003eCdBr\u003csub\u003e4\u003c/sub\u003e.\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-2849469/v1/74f23a8a56396925896d188f.png"},{"id":36438687,"identity":"b78e0cfa-daf1-4aa9-ac88-21286b1c94cc","added_by":"auto","created_at":"2023-04-28 17:06:22","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":207047,"visible":true,"origin":"","legend":"\u003cp\u003eIn-situ \u003csup\u003e1\u003c/sup\u003eH MAS NMR chemical shifts of NH\u003csub\u003e2\u003c/sub\u003e and CH\u003csub\u003e3\u003c/sub\u003e in [NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e2\u003c/sub\u003eCdBr\u003csub\u003e4\u003c/sub\u003e at phases IV, III, and II (Inset: Change of line width as a function of temperature).\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-2849469/v1/c941d6ffb545e93fd0495749.png"},{"id":36438977,"identity":"ff9c0ea6-b229-4c3f-8633-50801f2f6e6b","added_by":"auto","created_at":"2023-04-28 17:14:22","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":210827,"visible":true,"origin":"","legend":"\u003cp\u003eIn-situ \u003csup\u003e13\u003c/sup\u003eC MAS NMR chemical shifts in [NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e2\u003c/sub\u003eCdBr\u003csub\u003e4\u003c/sub\u003e at phases IV, III, and II (Inset: Change of line width as a function of temperature).\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-2849469/v1/82e59fb61be26441e493df94.png"},{"id":36439257,"identity":"40a3cb33-5367-4ee3-8cae-80f5de60d2a2","added_by":"auto","created_at":"2023-04-28 17:22:22","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":126651,"visible":true,"origin":"","legend":"\u003cp\u003eStatic \u003csup\u003e14\u003c/sup\u003eN NMR chemical shifts in [NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e2\u003c/sub\u003eCdBr\u003csub\u003e4\u003c/sub\u003e as functions of temperature (Inset: \u003csup\u003e14\u003c/sup\u003eN NMR spectrum at 315 K).\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-2849469/v1/13571524a27539d43e180458.png"},{"id":36438691,"identity":"3c414bdb-bc8c-422e-ac9d-6e166b793444","added_by":"auto","created_at":"2023-04-28 17:06:23","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":159048,"visible":true,"origin":"","legend":"\u003cp\u003eStatic \u003csup\u003e113\u003c/sup\u003eCd NMR chemical shifts in [NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e2\u003c/sub\u003eCdBr\u003csub\u003e4\u003c/sub\u003e at phases IV, III, and II (Inset: \u003csup\u003e113\u003c/sup\u003eCd NMR spectrum at 180 K and 420 K).\u003c/p\u003e","description":"","filename":"floatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-2849469/v1/9b9219fb8321f2c36fae176f.png"},{"id":36438689,"identity":"6369f2d2-8220-4a23-8c41-5ba6341f32c4","added_by":"auto","created_at":"2023-04-28 17:06:22","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":180795,"visible":true,"origin":"","legend":"\u003cp\u003e\u003csup\u003e1\u003c/sup\u003eH NMR spin-lattice relaxation times T\u003csub\u003e1ρ\u003c/sub\u003e in [NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e2\u003c/sub\u003eCdBr\u003csub\u003e4\u003c/sub\u003e at phase IV, III, II, and I (Inset: the slopes of dotted lines are represented the activation energies by the correlation times as a function of inverse temperature).\u003c/p\u003e","description":"","filename":"floatimage9.png","url":"https://assets-eu.researchsquare.com/files/rs-2849469/v1/c10b31ca8bea07dfadc808cc.png"},{"id":36438692,"identity":"70564460-4b8e-4c79-b2a2-caf5181a6283","added_by":"auto","created_at":"2023-04-28 17:06:23","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":148306,"visible":true,"origin":"","legend":"\u003cp\u003e\u003csup\u003e13\u003c/sup\u003eC NMR spin-lattice relaxation times T\u003csub\u003e1ρ\u003c/sub\u003e in [NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e2\u003c/sub\u003eCdBr\u003csub\u003e4\u003c/sub\u003e at phase IV, III, and II (Inset: the slopes of dotted lines are represented the activation energies by the correlation times as a function of inverse temperature).\u003c/p\u003e","description":"","filename":"floatimage10.png","url":"https://assets-eu.researchsquare.com/files/rs-2849469/v1/1a675c64051b76afb3f799a4.png"},{"id":39865657,"identity":"6bd05469-c69a-4d59-8e35-6633a5457204","added_by":"auto","created_at":"2023-07-11 15:14:48","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1918319,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-2849469/v1/ad991406-18b6-4844-8c40-085a9dd55fd1.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Analysis of the structure, thermal, and molecular dynamics of organic–inorganic hybrid [NH 2 (CH 3 ) 2 ] 2 CdBr 4 crystal at phases IV, III, II, and I","fulltext":[{"header":"Introduction","content":"\u003cp\u003eOrganic\u0026ndash;inorganic hybrid compounds are of great interest for various applications such as sensors, fuel cells, solar cells, light-emitting transistors, and light-emitting diodes.\u003csup\u003e1-4\u003c/sup\u003e Additionally, organic\u0026ndash;inorganic hybrid perovskite materials are applied in ferroelectrics, dielectric switches, and optical switches.\u003csup\u003e5-11\u003c/sup\u003e Recently, CH\u003csub\u003e3\u003c/sub\u003eNH\u003csub\u003e3\u003c/sub\u003ePb\u003cem\u003eX\u003c/em\u003e\u003csub\u003e3\u003c/sub\u003e (\u003cem\u003eX\u003c/em\u003e = Cl, Br, I) has been used for solar cells, but these materials are easily degraded in humid air and are toxic because of the presence of Pb. Therefore, the development of eco-friendly hybrid perovskite solar cells is urgently required.\u003csup\u003e12-16\u003c/sup\u003e As new alternatives, two-dimensional compounds such as [NH\u003csub\u003e3\u003c/sub\u003e(CH\u003csub\u003e2\u003c/sub\u003e)\u003cem\u003e\u003csub\u003en\u003c/sub\u003e\u003c/em\u003eNH\u003csub\u003e3\u003c/sub\u003e]\u003cem\u003eMX\u003c/em\u003e\u003csub\u003e4\u003c/sub\u003e (\u003cem\u003en\u003c/em\u003e = 1, 2, 3, ∙∙∙; \u003cem\u003eM\u003c/em\u003e\u003csup\u003e2+\u003c/sup\u003e = divalent transition metal, Mn, Co, Cu, Zn, Cd, or Pb; \u003cem\u003eX\u003c/em\u003e = halogen, Cl, Br, or I)\u003csup\u003e17-28\u003c/sup\u003e and [(C\u003cem\u003e\u003csub\u003en\u003c/sub\u003e\u003c/em\u003eH\u003csub\u003e2\u003cem\u003en\u003c/em\u003e+1\u003c/sub\u003eNH\u003csub\u003e3\u003c/sub\u003e)]\u003csub\u003e2\u003c/sub\u003e\u003cem\u003eMX\u003c/em\u003e\u003csub\u003e4\u003c/sub\u003e are examples of organic\u0026ndash;inorganic hybrids that have recently attracted considerable attention.\u003csup\u003e29-37\u003c/sup\u003e Moreover, it is necessary to study the hydrogen bond structure of [NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003cem\u003e\u003csub\u003en\u003c/sub\u003e\u003c/em\u003e]\u003csub\u003e2\u003c/sub\u003e\u003cem\u003eMX\u003c/em\u003e\u003csub\u003e4\u003c/sub\u003e,\u003csup\u003e38-44\u003c/sup\u003e which is different than that of [NH\u003csub\u003e3\u003c/sub\u003e(CH\u003csub\u003e2\u003c/sub\u003e)\u003cem\u003e\u003csub\u003en\u003c/sub\u003e\u003c/em\u003eNH\u003csub\u003e3\u003c/sub\u003e]\u003cem\u003eMX\u003c/em\u003e\u003csub\u003e4\u003c/sub\u003e with three H atoms bonded to one N.\u003c/p\u003e\n\u003cp\u003eOne of these alternatives, dimethylammonium tetrabromocadmate\u0026nbsp;(II), [NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e2\u003c/sub\u003eCdBr\u003csub\u003e4\u003c/sub\u003e,\u003csup\u003e38, 39\u003c/sup\u003e is a member of [NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003cem\u003e\u003csub\u003en\u003c/sub\u003e\u003c/em\u003e]\u003csub\u003e2\u003c/sub\u003e\u003cem\u003eMX\u003c/em\u003e\u003csub\u003e4\u003c/sub\u003e, which belongs to the \u003cem\u003eA\u003c/em\u003e\u003csub\u003e2\u003c/sub\u003e\u003cem\u003eMX\u003c/em\u003e\u003csub\u003e4\u003c/sub\u003e group,\u0026nbsp;where \u003cem\u003eA\u003c/em\u003e\u003csup\u003e+\u003c/sup\u003e is a univalent cation. These crystals undergo several structural phase transitions, which are commonly associated with the ordering of hydrogen bonds and the corresponding changes in the molecular dynamics of [NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e]\u003csup\u003e+\u003c/sup\u003e ions. The individual \u003cem\u003eMX\u003c/em\u003e\u003csub\u003e4\u003c/sub\u003e tetrahedral anions in these materials are completely isolated and surrounded by organic [NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e]\u003csup\u003e+\u003c/sup\u003e cations. These substances are expected to function as proton conductors via hydrogen bonding.\u003c/p\u003e\n\u003cp\u003e[NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e2\u003c/sub\u003eCdBr\u003csub\u003e4\u003c/sub\u003e was demonstrated to undergo three structural phase transitions at 380, 413, and 426 K.\u003csup\u003e39\u003c/sup\u003e At 300 K, the [NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e2\u003c/sub\u003eCdBr\u003csub\u003e4\u003c/sub\u003e crystal exhibited a monoclinic structure with a \u003cem\u003eP2\u003csub\u003e1\u003c/sub\u003e/n\u003c/em\u003e space group and its lattice constants were \u003cem\u003ea\u003c/em\u003e = 8.158 \u0026Aring;, \u003cem\u003eb\u003c/em\u003e = 11.632 \u0026Aring;, \u003cem\u003ec\u003c/em\u003e = 15.166 \u0026Aring;, \u003cem\u003e\u0026beta;\u003c/em\u003e = 94.82\u0026deg;, and Z = 4.\u003csup\u003e38\u003c/sup\u003e The structure consisted of [CdBr\u003csub\u003e4\u003c/sub\u003e]\u003csup\u003e2+\u003c/sup\u003e anions\u0026nbsp;and nonequivalent [NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e](1) and [NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e](2) cations. The structure comprised infinite chains of face-sharing CdBr\u003csub\u003e4\u003c/sub\u003e tetrahedra with\u0026nbsp;the [NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e]\u003csup\u003e+\u003c/sup\u003e ions located in the free space between the chains. Notably, the slightly deformed CdBr\u003csub\u003e4\u003c/sub\u003e tetrahedra were linked to organic [NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e] cations via N-H∙∙∙Br hydrogen bonds.\u003csup\u003e38\u003c/sup\u003e\u003c/p\u003e\n\u003cp\u003eIn this study, single crystals of [NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e2\u003c/sub\u003eCdBr\u003csub\u003e4\u003c/sub\u003e are grown using an aqueous solution method, and their structures and phase transition temperatures (T\u003csub\u003eC\u003c/sub\u003e) are characterized using single-crystal X-ray diffraction (XRD), powder XRD, and differential scanning calorimetry (DSC). Additionally, thermogravimetry analysis (TGA) is performed to gain a better understanding of the thermal properties of the samples. To characterize the coordination geometry of the \u003csup\u003e1\u003c/sup\u003eH, \u003csup\u003e13\u003c/sup\u003eC, \u003csup\u003e14\u003c/sup\u003eN, and \u003csup\u003e113\u003c/sup\u003eCd atoms in the samples, \u003csup\u003e1\u003c/sup\u003eH magic-angle spinning nuclear magnetic resonance (MAS NMR), \u003csup\u003e13\u003c/sup\u003eC MAS NMR, \u003csup\u003e14\u003c/sup\u003eN static NMR, and \u003csup\u003e113\u003c/sup\u003eCd static NMR chemical shifts are obtained as a function of temperature. Based on the results, the N‒H∙∙∙Br hydrogen bond between the cation and anion is discussed. Moreover,\u0026nbsp;\u003csup\u003e1\u003c/sup\u003eH and \u003csup\u003e13\u003c/sup\u003eC spin-lattice relaxation times\u0026nbsp;T\u003csub\u003e1\u003c/sub\u003e\u003csub\u003e\u0026rho;\u003c/sub\u003e representing the energy transfer around the \u003csup\u003e1\u003c/sup\u003eH and \u003csup\u003e13\u003c/sup\u003eC atoms of the cation are discussed, and their activation energies E\u003csub\u003ea\u003c/sub\u003e are determined.\u0026nbsp;The results of the single-crystal structure and physicochemical properties are predicted to provide important information on the fundamental mechanism of organic-inorganic hybrid compounds.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e"},{"header":"Methods ","content":"\u003cp\u003e\u003cstrong\u003eCrystal growth\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eSingle crystals of [NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e2\u003c/sub\u003eCdBr\u003csub\u003e4\u003c/sub\u003e were synthesized using dimethylammonium bromide (Aldrich, 98 %) and CdBr\u003csub\u003e2\u003c/sub\u003e∙4H\u003csub\u003e2\u003c/sub\u003eO (Aldrich, 98 %) in a ratio of 2:1. The mixture was stirred and heated to obtain a homogeneous solution. Subsequently, the mixture was filtered through a filter paper, and transparent colorless single crystals were grown by gradual evaporation for a few days in a temperature-controlled oven at 300 K.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003cstrong\u003eCharacterization\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe structure and lattice parameters of\u0026nbsp;the [NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e2\u003c/sub\u003eCdBr\u003csub\u003e4\u003c/sub\u003e crystal were determined at 300 K using a single-crystal XRD system at the Korea Basic Science Institute (KBSI) Western Seoul Center. Powder XRD patterns were measured at several temperatures at the same facility. The experimental conditions for the two XRD measurements are described in previously reported results.\u003csup\u003e45\u003c/sup\u003e\u003c/p\u003e\n\u003cp\u003eDSC measurements\u0026nbsp;were performed on a DSC instrument (TA Instruments, DSC 25) in the temperature range of 200\u0026ndash;573 K at\u0026nbsp;a\u0026nbsp;heating rate of 10 K/min under nitrogen gas flow. The amount of\u0026nbsp;sample used in the DSC experiment was 6.3 \u003cem\u003emg\u003c/em\u003e.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAdditionally, TGA was performed in the temperature range of 300\u0026ndash;873 K at a heating rate of 10 K/min under nitrogen gas flow.\u003c/p\u003e\n\u003cp\u003eThe MAS\u0026nbsp;NMR chemical shifts and spin-lattice relaxation time T\u003csub\u003e1\u0026rho;\u003c/sub\u003e of the [NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e2\u003c/sub\u003eCdBr\u003csub\u003e4\u003c/sub\u003e crystals were measured using a solid-state NMR spectrometer (AVANCE III+, Bruker) at the KBSI Western Seoul Center. The Larmor frequency for the \u003csup\u003e1\u003c/sup\u003eH NMR experiment was 400.13 MHz, and that for the \u003csup\u003e13\u003c/sup\u003eC NMR experiment was 100.61 MHz. MAS NMR measurements of the samples in cylindrical zirconia rotors were performed at a spinning rate of 10 kHz to reduce the spinning sideband. Chemical shifts were referenced to standard materials adamantane and tetramethylsilane (TMS) for \u003csup\u003e1\u003c/sup\u003eH and \u003csup\u003e13\u003c/sup\u003eC, respectively,\u0026nbsp;to\u0026nbsp;accurately measure the chemical shifts of the samples.\u0026nbsp;T\u003csub\u003e1\u0026rho;\u003c/sub\u003e values were measured using a \u0026pi;/2\u0026minus;\u003cem\u003e\u0026tau;\u003c/em\u003e pulse with a spin-lock pulse of duration \u003cem\u003e\u0026tau;.\u003c/em\u003e Static \u003csup\u003e14\u003c/sup\u003eN NMR chemical shifts were recorded using the one-pulse method at a Larmor frequency of 28.90 MHz, NH\u003csub\u003e4\u003c/sub\u003eNO\u003csub\u003e3\u003c/sub\u003e was used as the standard sample. Furthermore, static \u003csup\u003e113\u003c/sup\u003eCd NMR chemical shifts were measured at a Larmor frequency of 88.75 MHz, and the chemical shift of CdCl\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e8\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO was used as the standard sample.\u0026nbsp;\u003c/p\u003e"},{"header":"Experimental results","content":"\n\u003ch3\u003eCrystal structure\u003c/h3\u003e\n\u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eSingle-crystal XRD results for the [NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e2\u003c/sub\u003eCdBr\u003csub\u003e4\u003c/sub\u003e crystal were obtained at 300 K. The synthesized crystal had a monoclinic system with a \u003cem\u003eP2\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/n\u003c/em\u003e space group, and lattice constants of \u003cem\u003ea\u003c/em\u003e\u0026thinsp;=\u0026thinsp;8.2528 (9) \u0026Aring;, \u003cem\u003eb\u003c/em\u003e\u0026thinsp;=\u0026thinsp;11.7833 (14) \u0026Aring;, \u003cem\u003ec\u003c/em\u003e\u0026thinsp;=\u0026thinsp;15.3589 (18) \u0026Aring;, \u003cem\u003eβ\u003c/em\u003e\u0026thinsp;=\u0026thinsp;94.726\u0026deg;, Z\u0026thinsp;=\u0026thinsp;4. These results are consistent with those previously reported.\u003csup\u003e38\u003c/sup\u003e Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e shows the thermal ellipsoids and atomic numbering for each atom, and the XRD data for the [NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e2\u003c/sub\u003eCdBr\u003csub\u003e4\u003c/sub\u003e crystal are listed in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. This compound is characterized by the N‒H∙∙∙Br hydrogen bonds connecting the two types of nonequivalent [NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e](1) and [NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e](2) cations to the [CdBr\u003csub\u003e4\u003c/sub\u003e] anion. The average bond length for Cd-Br was 2.5815 \u0026Aring;, and those for nonequivalent N(1)-C and N(2)-C were 1.466 and 1.473 \u0026Aring;, respectively.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003cp\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\u003eCrystal data and structure refinement for [NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e2\u003c/sub\u003eCdBr\u003csub\u003e4\u003c/sub\u003e at 300 K.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"2\"\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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eChemical formula\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eC\u003csub\u003e4\u003c/sub\u003eH\u003csub\u003e16\u003c/sub\u003eN\u003csub\u003e2\u003c/sub\u003eCdBr\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eWeight\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e524.23\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 \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\u003eP2\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/n\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eT (K)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e300\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\u003e8.2528 (9)\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\u003e11.7833 (14)\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 \u003cp\u003eβ (\u0026deg;)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e15.3589 (18)\u003c/p\u003e \u003cp\u003e94.726 (4)\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\u003e4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eV (\u0026Aring;\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1488.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRadiation type\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMo-Kα\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eWavelength (\u0026Aring;)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.71073\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\u003e27266\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIndependent reflections\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3667 (\u003cem\u003eR\u003c/em\u003e\u003csub\u003eint\u003c/sub\u003e = 0.0487)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGoodness-of-fit on \u003cem\u003eF\u003c/em\u003e\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.033\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFinal \u003cem\u003eR\u003c/em\u003e indices [I\u0026thinsp;\u0026gt;\u0026thinsp;2sigma(I)]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003eR\u003c/em\u003e\u003csub\u003e1\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;0.0313, \u003cem\u003ewR\u003c/em\u003e\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;0.0593\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eR\u003c/em\u003e indices (all data)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003eR\u003c/em\u003e\u003csub\u003e1\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;0.0499, \u003cem\u003ewR\u003c/em\u003e\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;0.0648\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cdiv id=\"Sec2\" class=\"Section2\"\u003e \u003ch2\u003ePhase transition temperatures\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e shows two strong endothermic peaks at 383 and 439 K with enthalpies of 12.93 and 17.14 kJ/mol, respectively. A weak endothermic peak was observed at 427 K with an enthalpy of 3.21 kJ/mol. Additionally, a minor peak with an enthalpy of 79 J/mol was observed at 417 K near the 427 K peak, as shown in the magnified inset in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. Starting at 200 K, these four phases are denoted as phase IV (below 383 K), phase III (between 383 and 417 K), phase II (between 417 and 427 K), and phase I (above 427 K).\u003c/p\u003e \u003cp\u003eTo determine whether these four endothermic peaks represent the phase transition or melting temperatures, the changes in the single crystal with increasing temperature were observed using an optical polarizing microscope. Up to 430 K, the single crystal remained almost unchanged, but the surface of the single crystal started to melt above 439 K.\u003c/p\u003e \u003cp\u003eAdditionally, powder XRD experiments were performed with increasing temperature in the measurement range of 5\u0026deg;\u0026ndash;65\u0026deg; (2θ), as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. The XRD powder patterns recorded below 380 K (black) differed from those recorded above 390 K (red). This difference is related to the structural phase transition at T\u003csub\u003eC1\u003c/sub\u003e (383 K). Furthermore, the XRD patterns recorded above 390 K differed from those recorded at 420 K (blue). Moreover, the XRD pattern recorded at 420 K differed from that obtained at 430 K (olive), exhibiting a distinct change. Finally, the pattern at 450 K was completely different from those at temperatures below 450 K, and no crystallinity was observed, indicating that it is the melting point.\u003c/p\u003e \u003cp\u003eThe phase transition and melting temperatures determined by the powder XRD and optical polarizing microscope results are consistent with the endothermic peaks obtained from the DSC curves. Therefore,\u003c/p\u003e \u003cp\u003ebased on the DSC, XRD, and polarizing microscopy results, the phase transition temperatures are T\u003csub\u003eC1\u003c/sub\u003e = 383 K, T\u003csub\u003eC2\u003c/sub\u003e = 417 K, and T\u003csub\u003eC3\u003c/sub\u003e = 427 K, and the melting temperature is T\u003csub\u003em\u003c/sub\u003e = 439 K.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eThermal property\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eThe TGA curve of the [NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e2\u003c/sub\u003eCdBr\u003csub\u003e4\u003c/sub\u003e crystal with increasing temperature is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e. The partial decomposition temperature was observed at 547 K, corresponding to a weight loss of 2%. Therefore, this material is thermally stable up to 547 K. The molecular weight of the [NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e2\u003c/sub\u003eCdBr\u003csub\u003e4\u003c/sub\u003e crystal decreased rapidly as the temperature increased owing to partial decomposition. From the total molecular weight of 524.23 mg, the amounts remaining after partial decomposition of HBr and 2HBr were obtained using the TGA data and the following chemical reactions.\u003csup\u003e46\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e{[NH(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e2\u003c/sub\u003eHBr∙CdBr\u003csub\u003e2\u003c/sub\u003e (s)\u0026thinsp;+\u0026thinsp;HBr(g)}/[NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e2\u003c/sub\u003eCdBr\u003csub\u003e4\u003c/sub\u003e = 84.56% (1)\u003c/p\u003e \u003cp\u003e{[NH(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e2\u003c/sub\u003eCdBr\u003csub\u003e2\u003c/sub\u003e (s)\u0026thinsp;+\u0026thinsp;2HBr(g)}/[NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e2\u003c/sub\u003eCdBr\u003csub\u003e4\u003c/sub\u003e = 69.13% (2)\u003c/p\u003e \u003cp\u003eMolecular-weight losses of 25% and 31% were observed after decomposition of HBr and 2HBr, respectively. The initial weight loss (25%) occurred in the temperature range of 550\u0026ndash;600 K, and the second decomposition (31%) occurred in the temperature range of 623 K.\u003c/p\u003e \u003cp\u003eIn contrast, three endothermic peaks were observed at 383, 425, and 438 K in the differential thermal analysis (DTA) curve, which is the differential form of the TGA curve, and are in good agreement with the phase transition and melting temperatures determined by DSC. The large endothermic peak observed near 623 K is in good agreement with the 2HBr decomposition temperature calculated from the total weight of the crystal. Moreover, total weight loss occurred at temperatures above 800 K.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003e \u003csup\u003e \u003cb\u003e1\u003c/b\u003e \u003c/sup\u003e \u003cb\u003eH and\u003c/b\u003e \u003csup\u003e \u003cb\u003e13\u003c/b\u003e \u003c/sup\u003e \u003cb\u003eC MAS NMR chemical shifts\u003c/b\u003e \u003c/p\u003e \u003cp\u003eThe in situ NMR chemical shifts for \u003csup\u003e1\u003c/sup\u003eH in the [NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e2\u003c/sub\u003eCdBr\u003csub\u003e4\u003c/sub\u003e crystal were recorded for phases IV, III, and II, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e. For phase IV, the \u003csup\u003e1\u003c/sup\u003eH NMR signals of NH\u003csub\u003e2\u003c/sub\u003e and CH\u003csub\u003e3\u003c/sub\u003e completely overlapped, and only one signal was obtained. The sidebands in the \u003csup\u003e1\u003c/sup\u003eH spectrum for phase IV are represented by open circles. The \u003csup\u003e1\u003c/sup\u003eH chemical shifts barely changed as the temperature increased, whereas the \u003csup\u003e1\u003c/sup\u003eH signals of NH\u003csub\u003e2\u003c/sub\u003e and CH\u003csub\u003e3\u003c/sub\u003e for phase III began to separate. The \u003csup\u003e1\u003c/sup\u003eH coordination geometry for NH\u003csub\u003e2\u003c/sub\u003e changed near T\u003csub\u003eC1\u003c/sub\u003e. These results indicate that the \u003csup\u003e1\u003c/sup\u003eH coordination geometry for CH\u003csub\u003e3\u003c/sub\u003e remains unchanged with increasing temperature, whereas that for NH\u003csub\u003e2\u003c/sub\u003e changes.\u003c/p\u003e \u003cp\u003eConversely, the full width at half maximum of the \u003csup\u003e1\u003c/sup\u003eH NMR signal decreased with increasing temperature, as shown in detail in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e. The linewidth of the \u003csup\u003e1\u003c/sup\u003eH NMR signal decreased from approximately 7 to 1 ppm as the temperature increased and showed a distinct decrease at T\u003csub\u003eC2\u003c/sub\u003e, similar to the change in \u003csup\u003e1\u003c/sup\u003eH chemical shifts. This trend indicates that the mobility of \u003csup\u003e1\u003c/sup\u003eH becomes very active at high temperatures.\u003c/p\u003e \u003cp\u003eAdditionally, the in situ \u003csup\u003e13\u003c/sup\u003eC NMR chemical shifts in [NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e2\u003c/sub\u003eCdBr\u003csub\u003e4\u003c/sub\u003e were measured for phases IV, III, and II with increasing temperature, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e. Only one \u003csup\u003e13\u003c/sup\u003eC signal was observed for the two CH\u003csub\u003e3\u003c/sub\u003e groups in the crystal structure; thus, the structural environments for these two CH\u003csub\u003e3\u003c/sub\u003e groups are identical. The \u003csup\u003e13\u003c/sup\u003eC NMR chemical shift obtained at 300 K was observed at 37.84 ppm. The chemical shifts for phases\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eIV and III shifted in the positive direction, and the \u003csup\u003e13\u003c/sup\u003eC chemical shifts discontinuously changed near T\u003csub\u003eC1\u003c/sub\u003e, similar to the \u003csup\u003e1\u003c/sup\u003eH NMR results. The linewidths shown in the inset in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e were very small compared to the \u003csup\u003e1\u003c/sup\u003eH linewidths, and the linewidths decreased with increasing temperature but remained almost constant at temperatures above 280 K.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003cdiv id=\"Sec4\" class=\"Section3\"\u003e \u003ch2\u003eStatic \u003csup\u003e14\u003c/sup\u003eN and \u003csup\u003e113\u003c/sup\u003eCd NMR chemical shifts\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eThe static NMR spectrum for \u003csup\u003e14\u003c/sup\u003eN in NH\u003csub\u003e2\u003c/sub\u003e at the center of the cation in the [NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e2\u003c/sub\u003eCdBr\u003csub\u003e4\u003c/sub\u003e single crystal is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e. NMR spectra were obtained in the temperature range of 180\u0026ndash;380 K, and the direction of the magnetic field and single crystal were measured in an arbitrary direction. The spin number of \u003csup\u003e14\u003c/sup\u003eN is I\u0026thinsp;=\u0026thinsp;1, and therefore two resonance signals were expected owing to the quadrupole interaction [47]. Notably, it was very difficult to obtain \u003csup\u003e14\u003c/sup\u003eN NMR spectra owing to the low Larmor frequency. Because the intensity was very weak and the linewidth was broad, it was difficult to obtain the \u003csup\u003e14\u003c/sup\u003eN NMR signals, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e. The [NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e2\u003c/sub\u003eCdBr\u003csub\u003e4\u003c/sub\u003e structure consists of complex [CdBr\u003csub\u003e4\u003c/sub\u003e] anions, and [NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e](1) and [NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e](2) cations. The structural properties of N(1) and N(2) in the two [NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e]\u003csup\u003e+\u003c/sup\u003e groups were determined based on the \u003csup\u003e14\u003c/sup\u003eN NMR chemical shifts. The chemical shifts of the \u003csup\u003e14\u003c/sup\u003eN NMR spectra obtained at several temperatures are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e. The N(1) chemical shifts represented by red squares decreased with increasing temperature, whereas the N(2) chemical shifts represented by blue circles slightly increased. The pairs for \u003csup\u003e14\u003c/sup\u003eN are indicated by the same symbols, and N(1) and N(2) were arbitrarily named. The linewidth at 300 K was very broad at approximately 80 ppm. However, \u003csup\u003e14\u003c/sup\u003eN signals were not easily detected at temperatures near T\u003csub\u003eC1\u003c/sub\u003e. The two groups of \u003csup\u003e14\u003c/sup\u003eN signals demonstrate the presence of two nonequivalent N sites. Additionally, it was confirmed that there were different N(1) and N(2) sites, as shown in the single-crystal XRD results. The continuous change in the N(1) and N(2) chemical shifts with increasing temperature indicates a change in the coordination geometry of the local environment of N.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eBased on information obtained from \u003csup\u003e113\u003c/sup\u003eCd chemical shifts, the changes in the structural environment around Cd in the anion CdBr\u003csub\u003e4\u003c/sub\u003e were evaluated. The spin number of \u003csup\u003e113\u003c/sup\u003eCd is I\u0026thinsp;=\u0026thinsp;1/2, and therefore only one resonance signal was expected.\u003csup\u003e47\u003c/sup\u003e The static \u003csup\u003e113\u003c/sup\u003eCd NMR chemical shifts of the three phases are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e. The chemical shift of \u003csup\u003e113\u003c/sup\u003eCd at 300 K was 386.93 ppm, and the linewidth was broad at approximately 30 ppm. \u003csup\u003e113\u003c/sup\u003eCd NMR spectra measured at 180 and 420 K are shown in the inset in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e. The linewidth at 180 K was much wider than that at 420 K, indicating that the mobility of Cd increases with increasing temperature. In contrast to the \u003csup\u003e1\u003c/sup\u003eH and \u003csup\u003e13\u003c/sup\u003eC chemical shifts, the \u003csup\u003e113\u003c/sup\u003eCd chemical shifts continuously changed toward negative values, and the chemical shifts near T\u003csub\u003eC1\u003c/sub\u003e showed discontinuous variation. Based on these results, it is proposed that the change in Br closest to Cd is large.\u003c/p\u003e \u003cp\u003e \u003csup\u003e \u003cb\u003e1\u003c/b\u003e \u003c/sup\u003e \u003cb\u003eH and\u003c/b\u003e \u003csup\u003e \u003cb\u003e13\u003c/b\u003e \u003c/sup\u003e \u003cb\u003eC NMR spin-lattice relaxation times\u003c/b\u003e \u003c/p\u003e \u003cp\u003eTo obtain the spin-lattice relaxation time T\u003csub\u003e1ρ\u003c/sub\u003e, the intensities of the NMR signals in the \u003csup\u003e1\u003c/sup\u003eH and \u003csup\u003e13\u003c/sup\u003eC NMR spectra were measured with increasing delay times. The decay curves of the change in the signal intensities and delay times are expressed by the following equation:\u003csup\u003e45, 47, 48\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eI(\u003cem\u003et\u003c/em\u003e)\u0026thinsp;=\u0026thinsp;I(0)exp(‒\u003cem\u003et\u003c/em\u003e/T\u003csub\u003e1ρ\u003c/sub\u003e), (3)\u003c/p\u003e \u003cp\u003ewhere I(\u003cem\u003et\u003c/em\u003e) is the intensity of the spectrum at time \u003cem\u003et\u003c/em\u003e and I(0) is the intensity of the spectrum at time \u003cem\u003et\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0. The T\u003csub\u003e1ρ\u003c/sub\u003e values for \u003csup\u003e1\u003c/sup\u003eH and \u003csup\u003e13\u003c/sup\u003eC in [NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e2\u003c/sub\u003eCdBr\u003csub\u003e4\u003c/sub\u003e were obtained using Eq.\u0026nbsp;(3), and the results are shown in Figs.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e and \u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e as a function of inverse temperature. The chemical shifts for \u003csup\u003e1\u003c/sup\u003eH in NH\u003csub\u003e2\u003c/sub\u003e and CH\u003csub\u003e3\u003c/sub\u003e were almost independent of temperature, but the T\u003csub\u003e1ρ\u003c/sub\u003e values were strongly dependent on temperature. As the temperature increased, T\u003csub\u003e1ρ\u003c/sub\u003e rapidly decreased, exhibiting a minimum value of 1.95 \u003cem\u003ems\u003c/em\u003e at 230 K and a\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003esecond minimum value of 2.74 \u003cem\u003ems\u003c/em\u003e at 310 K. Additionally, T\u003csub\u003e1ρ\u003c/sub\u003e was rapidly decreased at temperatures above T\u003csub\u003eC1\u003c/sub\u003e and then rapidly increased at temperatures above T\u003csub\u003eC3\u003c/sub\u003e. The T\u003csub\u003e1ρ\u003c/sub\u003e values of \u003csup\u003e1\u003c/sup\u003eH have two minima at 230 and 310 K, indicating molecular motion according to the Bloembergen\u0026ndash;Purcell\u0026ndash;Pound (BPP) theory. These T\u003csub\u003e1ρ\u003c/sub\u003e minima are attributable to the reorientational motion of \u003csup\u003e1\u003c/sup\u003eH in NH\u003csub\u003e2\u003c/sub\u003e and CH\u003csub\u003e3\u003c/sub\u003e. Therefore, the experimental value of T\u003csub\u003e1ρ\u003c/sub\u003e can be expressed by the correlation time τ\u003csub\u003eC\u003c/sub\u003e for molecular motion, where the τ\u003csub\u003eC\u003c/sub\u003e value is determined as follows:\u003csup\u003e45, 47\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1/T\u003csub\u003e1ρ\u003c/sub\u003e)\u0026thinsp;=\u0026thinsp;R{4τ\u003csub\u003eC\u003c/sub\u003e/[1\u0026thinsp;+\u0026thinsp;ω\u003csub\u003e1\u003c/sub\u003e\u003csup\u003e2\u003c/sup\u003eτ\u003csub\u003eC\u003c/sub\u003e\u003csup\u003e2\u003c/sup\u003e] + τ\u003csub\u003eC\u003c/sub\u003e/[1 + (ω\u003csub\u003eC\u003c/sub\u003e ‒ ω\u003csub\u003eH\u003c/sub\u003e)\u003csup\u003e2\u003c/sup\u003e τ\u003csub\u003eC\u003c/sub\u003e\u003csup\u003e2\u003c/sup\u003e]\u0026thinsp;+\u0026thinsp;3τ\u003csub\u003eC\u003c/sub\u003e/[1\u0026thinsp;+\u0026thinsp;ω\u003csub\u003eC\u003c/sub\u003e\u003csup\u003e2\u003c/sup\u003eτ\u003csub\u003eC\u003c/sub\u003e\u003csup\u003e2\u003c/sup\u003e]\u0026thinsp;+\u0026thinsp;6τ\u003csub\u003eC\u003c/sub\u003e/[1 + (ω\u003csub\u003eC\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;ω\u003csub\u003eH\u003c/sub\u003e)\u003csup\u003e2\u003c/sup\u003e τ\u003csub\u003eC\u003c/sub\u003e\u003csup\u003e2\u003c/sup\u003e]\u003c/p\u003e \u003cp\u003e+\u0026thinsp;6τ\u003csub\u003eC\u003c/sub\u003e/[1\u0026thinsp;+\u0026thinsp;ω\u003csub\u003eH\u003c/sub\u003e\u003csup\u003e2\u003c/sup\u003eτ\u003csub\u003eC\u003c/sub\u003e\u003csup\u003e2\u003c/sup\u003e]}, (4)\u003c/p\u003e \u003cp\u003ewhere R is a constant, ω\u003csub\u003e1\u003c/sub\u003e is the spin-lock field, and ω\u003csub\u003eC\u003c/sub\u003e and ω\u003csub\u003eH\u003c/sub\u003e are the Larmor frequencies for carbon and protons, respectively. The data were analyzed by assuming that T\u003csub\u003e1ρ\u003c/sub\u003e had the lowest value when ω\u003csub\u003e1\u003c/sub\u003eτ\u003csub\u003eC\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;1, and the relationship between T\u003csub\u003e1ρ\u003c/sub\u003e and the radio frequency power of the spin-lock pulse ω\u003csub\u003e1\u003c/sub\u003e was applicable.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eBecause the T\u003csub\u003e1ρ\u003c/sub\u003e curves exhibited minima, the coefficient R in Eq.\u0026nbsp;(4) can be obtained. Based on the obtained value for R, the τ\u003csub\u003eC\u003c/sub\u003e values were calculated as a function of temperature. The local field fluctuation is owing to the thermal motion of protons and carbon atoms, which are activated by thermal energy. The τ\u003csub\u003eC\u003c/sub\u003e of motion is generally assumed to have Arrhenius dependence on the activation energy for motion and temperature.\u003csup\u003e45, 47\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eτ\u003csub\u003eC\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;τ\u003csub\u003eC\u003c/sub\u003e\u003csup\u003eo\u003c/sup\u003eexp(‒E\u003csub\u003ea\u003c/sub\u003e/k\u003csub\u003eB\u003c/sub\u003eT), (5)\u003c/p\u003e \u003cp\u003ewhere E\u003csub\u003ea\u003c/sub\u003e and k\u003csub\u003eB\u003c/sub\u003e are the activation energy of motion and the Boltzmann constant, respectively. The magnitude of E\u003csub\u003ea\u003c/sub\u003e depends on the molecular dynamics. To determine the molecular dynamics, the logarithmic scale of τ\u003csub\u003eC\u003c/sub\u003e represented by red circles as a function of 1000/T is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e. Based on the slopes of the dotted lines at low and high temperatures for phase IV, E\u003csub\u003ea\u003c/sub\u003e was found to be 31.78\u0026thinsp;\u0026plusmn;\u0026thinsp;3.41 and 27.88\u0026thinsp;\u0026plusmn;\u0026thinsp;2.45 kJ/mol, respectively. Additionally, the E\u003csub\u003ea\u003c/sub\u003e obtained from the slope of T\u003csub\u003e1ρ\u003c/sub\u003e as a function of inverse temperature for phase III was 72.12\u0026thinsp;\u0026plusmn;\u0026thinsp;0.84 kJ/mol. Therefore, the difference in E\u003csub\u003ea\u003c/sub\u003e between phases IV and III near T\u003csub\u003eC1\u003c/sub\u003e was very large.\u003c/p\u003e \u003cp\u003eFor \u003csup\u003e13\u003c/sup\u003eC, the T\u003csub\u003e1ρ\u003c/sub\u003e values shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e changed significantly at the phase transition temperature of T\u003csub\u003eC1\u003c/sub\u003e. As the temperature increased, T\u003csub\u003e1ρ\u003c/sub\u003e exhibited a small minimum value of 18.22 \u003cem\u003ems\u003c/em\u003e at 190 K, a second minimum value of 13.18 \u003cem\u003ems\u003c/em\u003e at 260 K, and a third minimum value of 71.49 \u003cem\u003ems\u003c/em\u003e at 340 K. Moreover, T\u003csub\u003e1ρ\u003c/sub\u003e was rapidly shortened at temperatures above T\u003csub\u003eC1\u003c/sub\u003e. The T\u003csub\u003e1ρ\u003c/sub\u003e values of \u003csup\u003e13\u003c/sup\u003eC exhibited three minima at 190, 260, and 340 K, indicating molecular motion occurs according to the BPP theory. These minimum values of T\u003csub\u003e1ρ\u003c/sub\u003e are clearly attributable to the reorientational motion of \u003csup\u003e13\u003c/sup\u003eC in CH\u003csub\u003e3\u003c/sub\u003e. The experimental values of T\u003csub\u003e1ρ\u003c/sub\u003e were expressed in terms of the τ\u003csub\u003eC\u003c/sub\u003e. The logarithmic scale of τ\u003csub\u003eC\u003c/sub\u003e represented by blue squares as a function of 1000/T is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e. Based on the slopes of the dotted line at low and high temperatures for phase IV, E\u003csub\u003ea\u003c/sub\u003e was found to be 18.22\u0026thinsp;\u0026plusmn;\u0026thinsp;3.41, 21.07\u0026thinsp;\u0026plusmn;\u0026thinsp;2.45, and 28.78 kJ/mol, respectively. Additionally, the E\u003csub\u003ea\u003c/sub\u003e obtained from the slope of T\u003csub\u003e1ρ\u003c/sub\u003e as a function of inverse temperature for phase III was 55.66\u0026thinsp;\u0026plusmn;\u0026thinsp;0.84 kJ/mol. Therefore, the difference in E\u003csub\u003ea\u003c/sub\u003e between phases IV and III near T\u003csub\u003eC1\u003c/sub\u003e was very large, which is similar to the \u003csup\u003e1\u003c/sup\u003eH results.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"Conclusion","content":"\u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eThe physicochemical properties of the organic\u0026ndash;inorganic hybrid [NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e2\u003c/sub\u003eCdBr\u003csub\u003e4\u003c/sub\u003e crystal are discussed. First, the monoclinic structure of this crystal was confirmed by single-crystal XRD, and the three-phase transition temperatures of 383, 417, and 427 K were determined using DSC and powder XRD analyses. This crystal had a good thermal stability of approximately 547 K, and weight loss was observed with increasing temperature owing to thermal decomposition, which resulted in the loss of HBr and 2HBr moieties. Second, the chemical shifts were caused by the local field around the resonating nucleus. Moreover, the \u003csup\u003e1\u003c/sup\u003eH, \u003csup\u003e13\u003c/sup\u003eC, \u003csup\u003e14\u003c/sup\u003eN, and \u003csup\u003e113\u003c/sup\u003eCd NMR chemical shifts changed continuously with temperature, especially at T\u003csub\u003eC1\u003c/sub\u003e, suggesting that the local environment changed with temperature. Owing to the large change in \u003csup\u003e113\u003c/sup\u003eCd chemical shifts, the coordination geometry of Br around Cd in CdBr\u003csub\u003e4\u003c/sub\u003e tetrahedra changes near T\u003csub\u003eC1\u003c/sub\u003e. Therefore, it is proposed that Br plays an important role in the N‒H\u0026middot;\u0026middot;\u0026middot;Br hydrogen bond. Finally, \u003csup\u003e1\u003c/sup\u003eH T\u003csub\u003e1ρ\u003c/sub\u003e and \u003csup\u003e13\u003c/sup\u003eC T\u003csub\u003e1ρ\u003c/sub\u003e values, which represent the energy transfer around the \u003csup\u003e1\u003c/sup\u003eH and \u003csup\u003e13\u003c/sup\u003eC atoms of the cation, changed significantly with temperature, indicating that the T\u003csub\u003e1ρ\u003c/sub\u003e values for \u003csup\u003e1\u003c/sup\u003eH and \u003csup\u003e13\u003c/sup\u003eC are governed by tumbling motions. The activation energies derived from the results of the NMR T\u003csub\u003e1ρ\u003c/sub\u003e experiments for molecular motion were very high at high temperatures. Based on the basic mechanism obtained for the [NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e2\u003c/sub\u003eCdBr\u003csub\u003e4\u003c/sub\u003e crystal, it is expected that the application of this organic\u0026ndash;inorganic material is possible.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe datasets generated and/or analysed during the current study are available in the CCDC 2256555. For ESI and crystallographic data in CIF or other electronic format see https://doi.org/.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThis work was supported by the National Research Foundation of Korea (NRF) grant, funded by the Korea government (MSIT) (2023R1A2C2006333). The work was supported by the Basic Science Research program of the National Research Foundation of Korea (NRF), funded by the Ministry of Education, Science and Technology (2016R1A6A1A03012069).\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003cstrong\u003eAuthor contributions\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA.R. Lim. designed the project, XRD experiments, and wrote the manuscript. S.H. Kim performed NMR, and Y.L. Joo commented the manuscript.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;Competing of interests\u003c/p\u003e\n\u003cp\u003eThe\u0026nbsp;authors declare no\u0026nbsp;competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eAdditional Information\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eCorrespondence and requests for materials should be addressed to A. R. Lim.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eMathlouthi, M., Valkonen, A., Rzaigui, M., Smirani, W. 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Structural phase transition, thermal analysis, and spectroscopic studies in an organic\u0026ndash;inorganic hybrid crystal: [(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003eNH\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e2\u003c/sub\u003eZnBr\u003csub\u003e4\u003c/sub\u003e. \u003cem\u003eAppl. Organometal Chem\u003c/em\u003e. \u003cstrong\u003e34\u003c/strong\u003e, e5656 (2020).\u003c/li\u003e\n\u003cli\u003eMahfoudh, N., Karoui, K., BenRhaiem, A. Optical studies and dielectric response of [DMA]\u003csub\u003e2\u003c/sub\u003eMCl\u003csub\u003e4\u003c/sub\u003e (M = Zn and Co) and [DMA]\u003csub\u003e2\u003c/sub\u003eZnBr\u003csub\u003e4\u003c/sub\u003e. \u003cem\u003eRSC Advances\u003c/em\u003e, \u003cstrong\u003e11\u003c/strong\u003e, 24526 (2021).\u003c/li\u003e\n\u003cli\u003eLim, A. R., Cho, J. Growth, structure, phase transition, thermal properties, and structural dynamics of organic-inorganic hybrid [NH\u003csub\u003e3\u003c/sub\u003e(CH\u003csub\u003e2\u003c/sub\u003e)\u003csub\u003e5\u003c/sub\u003eNH\u003csub\u003e3\u003c/sub\u003e]ZnCl\u003csub\u003e4\u003c/sub\u003e crystal. \u003cem\u003eSci. Rep.\u003c/em\u003e\u003cstrong\u003e12\u003c/strong\u003e,16901 (2022).\u003c/li\u003e\n\u003cli\u003eLim, A. R., Kim, S. H., Joo, Y. L. Physicochemical properties and structural dynamics of organic\u0026ndash; inorganic hybrid [NH\u003csub\u003e3\u003c/sub\u003e(CH\u003csub\u003e2\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003eNH\u003csub\u003e3\u003c/sub\u003e]ZnX\u003csub\u003e4\u003c/sub\u003e (X = Cl and Br) crystals. \u003cem\u003eSci. Rep\u003c/em\u003e. \u003cstrong\u003e11\u003c/strong\u003e, 8408 (2021). \u003c/li\u003e\n\u003cli\u003eAbragam, A. \u003cem\u003eThe Principles of Nuclear Magnetism\u003c/em\u003e (Oxford University Press, 1961).\u003c/li\u003e\n\u003cli\u003eHarris, R. K. \u003cem\u003eNuclear Magnetic Resonance Spectroscopy\u003c/em\u003e (Pitman Pub, 1983).\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-2849469/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-2849469/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eA comprehensive understanding of the physicochemical properties of organic–inorganic hybrids is essential for their application. Therefore, a single crystal of [NH\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e2\u003c/sub\u003eCdBr\u003csub\u003e4\u003c/sub\u003e was grown; the crystal structure was monoclinic, and the phase transition temperatures for the four phases IV, III, II, and I were 383 K (T\u003csub\u003eC1\u003c/sub\u003e), 417 K (T\u003csub\u003eC2\u003c/sub\u003e), and 427 K (T\u003csub\u003eC3\u003c/sub\u003e). Furthermore, the chemical shifts caused by the local field around \u003csup\u003e1\u003c/sup\u003eH, \u003csup\u003e13\u003c/sup\u003eC, \u003csup\u003e14\u003c/sup\u003eN, and \u003csup\u003e113\u003c/sup\u003eCd changed continuously with temperature, especially near T\u003csub\u003eC1\u003c/sub\u003e, indicating that the local environment changes with temperature. Owing to the large change in \u003csup\u003e113\u003c/sup\u003eCd chemical shifts, the coordination geometry of Br around Cd in the CdBr\u003csub\u003e4\u003c/sub\u003e tetrahedra changes near T\u003csub\u003eC1\u003c/sub\u003e. Therefore, it is thought that Br plays a significant role in the N‒H···Br hydrogen bond. Finally, the spin-lattice relaxation time T\u003csub\u003e1ρ\u003c/sub\u003e, representing the energy transfer around the \u003csup\u003e1\u003c/sup\u003eH and \u003csup\u003e13\u003c/sup\u003eC atoms of the cation, changed significantly with temperature. The activation energies obtained from the T\u003csub\u003e1ρ\u003c/sub\u003e results were two times larger at high temperatures than at low temperatures. This study provides an understanding of the fundamental properties of organic–inorganic hybrid compounds to broaden their applications.\u003c/p\u003e","manuscriptTitle":"Analysis of the structure, thermal, and molecular dynamics of organic–inorganic hybrid [NH 2 (CH 3 ) 2 ] 2 CdBr 4 crystal at phases IV, III, II, and I","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2023-04-28 17:06:18","doi":"10.21203/rs.3.rs-2849469/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"e71869ce-b683-46f5-bd7b-3abf1c9975f5","owner":[],"postedDate":"April 28th, 2023","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2023-07-11T15:14:40+00:00","versionOfRecord":[],"versionCreatedAt":"2023-04-28 17:06:18","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-2849469","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-2849469","identity":"rs-2849469","version":["v1"]},"buildId":"7rjqhiLT3MXkJMwkYKINL","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}