Side-Chain Type Metallo-Macrocycles: η5-cyclopentadienylcobalt-η4-cyclobutadiene Incorporated Conjugated Macrocycle

Side-Chain Type Metallo-Macrocycles: η5-cyclopentadienylcobalt-η4-cyclobutadiene Incorporated Conjugated Macrocycle | Authorea try { document.documentElement.classList.add('js'); } catch (e) { } var _gaq = _gaq || []; _gaq.push(['_setAccount', 'G-8VDV14Y67G']); _gaq.push(['_trackPageview']); (function() { var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s); })(); Skip to main content Preprints Collections Wiley Open Research IET Open Research Ecological Society of Japan All Collections About About Authorea FAQs Contact Us Quick Search anywhere Search for preprint articles, keywords, etc. Search Search ADVANCED SEARCH SCROLL This is a preprint and has not been peer reviewed. Data may be preliminary. 15 July 2025 V1 Latest version Share on Side-Chain Type Metallo-Macrocycles: η5-cyclopentadienylcobalt-η4-cyclobutadiene Incorporated Conjugated Macrocycle Authors : Lingyun Zhu , Gang Xu , Jianwei Liang , Jianfeng Yan , Yaofeng Yuan , Zheng Zhou , and Yuanming Li 0000-0003-3180-1305 [email protected] Authors Info & Affiliations https://doi.org/10.22541/au.175256494.44851855/v1 Published Organic Letters Version of record Peer review timeline 169 views 136 downloads Contents Abstract Supplementary Material Information & Authors Metrics & Citations View Options References Figures Tables Media Share Abstract This work reports the synthesis of a 1,3-linked tetra-cyclopentadienylcobalt-cyclobutadiene macrocycle ( [CpCoCb] 4 ) via Pt-templated cyclization. Structural characterization by SC-XRD confirms a C i -symmetric nanohoop (1.5 nm diameter). Unique CH-π interactions drive 1D channel packing. Electrochemical studies reveal multi-redox activity. This work establishes a new paradigm for strained organometallic architectures with potential applications in multi-state molecular electronics and host-guest systems. Cite this paper: Chin. J. Chem. 2024 , 42 , XXX—XXX. DOI: 10.1002/cjoc.202400XXX Side-Chain Type Metallo-Macrocycles: η 5 -cyclopentadienylcobalt- η 4 -cyclobutadiene Incorporated Conjugated Macrocycle Lingyun Zhu, a Gang Xu, a Jianwei Liang, b Jianfeng Yan,* ,a Yaofeng Yuan, a Zheng Zhou,* ,b and Yuanming Li* , a a Key Laboratory of Molecule Synthesis and Function Discovery (Fujian Province University), College of Chemistry, Fuzhou University, Fuzhou, 350108, China b School of Materials Science and Engineering, Tongji University, Shanghai 201804, China Metallo-Macrocycles | Multi-redox | Cobalt | Conjugated Macrocycle | Cyclobutadiene | Nanohoop Comprehensive Summary This work reports the synthesis of a 1,3-linked tetra-cyclopentadienylcobalt-cyclobutadiene macrocycle ([CpCoCb]₄) via Pt-templated cyclization . Structural characterization by SC-XRD confirms a C i -symmetric nanohoop (1.5 nm diameter). Unique CH-π interactions drive 1D channel packing. Electrochemical studies reveal multi-redox activity . This work establishes a new paradigm for strained organometallic architectures with potential applications in multi-state molecular electronics and host-guest systems. Background and Originality Content Organometallic materials, including ferrocene-based and η 5 -cyclopentadienylcobalt- η 4 -cyclobutadiene (CpCoCb, an 18-electron species) based materials, have a wide range of applications in catalysis, 1 biology, 2 single-molecule electronics, 3 polymer science, 4 et al. Although isoelectronic to ferrocene, CpCoCb features a square-planar cyclobutadiene (Cb) ligand that enables two distinct topological linkage modes (1,2- vs 1,3-) (Figure 1a). 5 The linear multi-CpCoCb organic polymer material has been well studied, which has applications in liquid crystals and conducting metallopolymers. 6 Compared to the linear conjugated system, the radial π conjugated system generally has better solubility, precise geometric configuration, and a rigid cavity for host-guest interaction. 7 Previous attempts to synthesize 1,2-linked CpCoCb macrocycles, which were synthesized via Hay coupling or Sonogashira reaction, suffered from low yields and challenging isomer separation due to the coordination orientation of CpCo units (Figure 1a). 8 Herein, we reported a 1,3-linked tera-CpCoCb-conjugated macrocycle ( [CpCoCb] 4 ) via Pt-templated macrocyclization with medium yield. Only one configuration was obtained for this macrocycle due to the higher symmetry of the 1,3-position Cb compared to the 1,2-position Cb. Distinct from the all-benzene architecture of [12]cycloparaphenylene ( [12]CPP ) and the ferrocenyl pentagonal units in tetraferrocene macrocycle ( [Fc] 4 ), [CpCoCb] 4 represents the demonstration of a nanohoop constructed from four-membered rings. The distinct anti-aromatic character of Cb units quenched by η 4 -Co coordination. Figure 1. Tetra-CpCoCb conjugated macrocycle. Results and Discussion The synthetic route of [CpCoCb] 4 was illustrated in Scheme 1. First, intermediate 2 was obtained by (4-bromophenylethynyl)trimethylsilane ( 1 ) with lithiation and borylation in 90% yield. The reaction of 2 with CpCo(CO) 2 yields a mixture of the two isomeric compounds, 3a and 3b , in a 2:1 ratio, with a combined yield of 81%. 9 For comparison, the acyclic fragment [CpCoCb] was synthesized in a similar method. Then, [CpCoCb] 4 was obtained in 42% yield through the Pt-mediated coupling strategy developed by Bauerle, 10 Yamago, 11 and Isobe et al. 12 The structure of [CpCoCb] 4 was characterized using NMR spectroscopy and SCXRD. The 1 H NMR spectrum of [CpCoCb] 4 showed a proton ratio of 4:4:5 in the aromatic region, indicating a high-symmetry structure. The hydrogen atoms in Cp exhibited a downfield shift of 0.22 ppm, resulting from the movement away from the shielding region of two adjacent phenylenes compared to [CpCoCb] (Figure 2). Scheme 1 The synthetic routes of [CpCoCb] 4 . Reaction conditions: (i) n -BuLi (1.2 equiv.), i ProBpin (1.5 equiv.), THF, -78 °C; (ii) CpCo(CO) 2 (0.5 equiv.), decane, 180 °C, 4 h; (iii) a) Pt(cod)Cl 2 (1.0 equiv.), CsF (6.0 equiv.) DCE, reflux, 48 h; b) PPh 3 (10.0 equiv.), toluene, 110 °C, 48 h. Figure 2. Partial 1 H NMR spectra of [CpCoCb] and [CpCoCb] 4 in CDCl 3. The precise geometrical structure of [CpCoCb] 4 was unambiguously confirmed by SCXRD analysis as shown in Figure 3. The crystal was obtained by diffusion of methanol into a dichloromethane solution of [CpCoCb] 4 . [CpCoCb] 4 crystallized in triclinic P \(\overline{1}\) space group. The size of the cavity is 15.43 Å x 14.94 Å. It exhibits a C i molecular symmetry, consistent with the high-symmetry structure in NMR. In the packing model, [CpCoCb] 4 molecules interact with each other through CH···π interactions ( d C-π = 4.70 Å). Additionally, the packing structure of [CpCoCb] 4 exhibits a 1D channel along the a -axis, highlighting its potential as a gas storage material. The average bond lengths of Cb, Cp, and two benzenes in [CpCoCb] 4 are 1.467, 1.403, 1.378, and 1.382 Å, respectively. That is shorter than the average bond lengths in acyclic fragment compound [CpCoCb] , which are 1.475, 1.411, 1.393, and 1.390 Å, respectively (Table 1). It’s worth noting that the Cb remains planar after cyclization, and the bending occurs on the benzene units in [CpCoCb] 4 . The average displacement of phenyl in [CpCoCb] 4 was 6.9° larger than [12]CPP. Compared with [Fc] 4 (AABB type) 13 and [12]CPP, 14 the diameter of [CpCoCb] 4 was comparable to that of [Fc] 4 but smaller than that of [12]CPP due to the smaller size of Cb than benzene. The structure of [Fc] 4 was further confirmed by SCXRD analysis, as shown in Figures 3e and 3f. It also crystallized in the triclinic P \(\overline{1}\) space group and exhibited a C i molecular symmetry, consistent with the smallest molecular strain energy. And the packing model was inverse zigzag packing. The molecular strain energy for [CpCoCb] 4 calculated using homodesmotic reactions 14a, 15 at B3LYP/6-31G(d), SDD level was 44.50 kcal/mol (Figure 4c, Figure S4). Figure 3. (a,b) main and side view of X-ray crystal structures of [CpCoCb] 4 , molecular dimensions (black); (c) the packing diagram of [CpCoCb] 4 viewed along the a -axis; (d) CH-π interactions between two adjacent molecules, d C-π was marked; (e) X-ray crystal structures of [Fc] 4 ; (f) packing diagram of [Fc] 4 viewed along the a -axis, coloured by symmetry equivalence. Hydrogen atoms are omitted for clarity. The photophysical properties of [CpCoCb] 4 and [CpCoCb] were measured with UV-Vis absorption (Figure 4). [CpCoCb] 4 exhibits bathochromic shift absorption at 370 nm (ε = 6.54 × 10 4 M –1 cm –1 ) compared with [CpCoCb] due to the larger conjugate system, which corresponds to the HOMO→LUMO transition. The absorption peak at 320 nm (9.98 × 10 4 M –1 cm –1 ) could be attributed to the HOMO-1→LUMO+1 and HOMO→LUMO+2 transition according to the time-dependent density functional theory (TD-DFT) calculation. The highest occupied molecular orbital (HOMO) delocalized along the entire backbone and the lowest unoccupied molecular orbital (LUMO) predominantly delocalized on the biphenyl moieties, indicating the formation of a π-conjugate system. Due to the photoinduced electron transfer (PET) effect, both [CpCoCb] 4 and [CpCoCb] had no fluorescent signal. Figure 4 (a) UV-Vis absorption of [CpCoCb] , [CpCoCb] 4 in DCM, concentration: 1.0 × 10 −5 M. (b) Qualitative energy diagram and frontier molecular orbitals of [CpCoCb] 4 , calculated at the B3LYP/6-31(G), SDD level of theory. (c) Molecular strain energy for [CpCoCb] 4 calculated and visualized using StrainViz. The electrochemical properties of [CpCoCb] 4 and [CpCoCb] were studied by cyclic voltammetry (CV) (Figure 5). The first oxidation potential of [CpCoCb] 4 ( E pa = 0.81 V) was lower than [CpCoCb] ( E pa = 0.88 V), which is consistent with the higher HOMO energy in the macrocycle (Figure S3). Due to the multi-metal core, three oxidation peaks ( E pa = 0.81, 0.92 and 1.09 V, respectively) were observed in the CV curve of [CpCoCb] 4 , which means it has potential applications in multi-stimulus-responsive materials. However, irreversible redox behaviour was observed after cyclization. Table 1. The calculated strain, displacement angle, diameter and average bond length of Ph, Cb, or Cp rings. [CpCoCb] - 0 - 1.391 1.475 1.411 [CpCoCb] 4 44 a 6.9 1.5 1.380 1.467 1.403 [Fc] 4 26 b 3.8 1.5 1.376 - 1.419 [12]CPP 48 c 6.2 d 1.7 c 1.401 - - a : calculated at B3LYP/6-31G(d), SDD; b : Ref 13, AABB type; c : Ref 14a, d : Ref 14b Figure 5. CV curves of [CpCoCb] , [CpCoCb] 4 in DCM, concentration: 1.0 × 10 −4 M. Conclusions In this study, we successfully synthesized a tetra-CpCoCb-based macrocycle ( [CpCoCb] 4 ) via a platinum-mediated approach. The structure was characterized using NMR spectroscopy and SCXRD, confirming its macrocycle with an approximate diameter of 1.5 nm. The multi-metal macrocycle displayed multiple redox properties, which had potential applications in organic electronic materials and expanded the topological structure of the organometallic macrocycle. Experimental Materials, measurements, and detailed experiments are presented in the Supporting Information. Deposition numbers CCDC: 2463988 (for [CpCoCb] 4 ), 2463989 (for [CpCoCb] ) and 2413513 (for [Fc] 4 ) are the supplementary crystallographic data for this paper. These data are provided free of charge by the joint Cambridge Crystallographic Data Centre. Supporting Information The supporting information for this article is available on the WWW under https://doi.org/10.1002/cjoc.202400xxx. Acknowledgement This work was supported by the National Natural Science Foundation of China (No. 22373019). We thank Mr. Xinyu Chen for DFT calculation. We thank Mr. Taosong Wang for the TOC. References 1. a) L. Dai, T. Tu, S. You, W. Deng and X. Hou, Asymmetric Catalysis with Chiral Ferrocene Ligands, Acc. Chem. Res. , 2003, 36 , 659-667.2. B. S. Ludwig, J. D. G. Correia and F. E. Kühn, Ferrocene derivatives as anti-infective agents, Coord. Chem. Rev. , 2019, 396 , 22-48.3. a) M. Akita and Y. Tanaka, Carbon-rich organometallics: Application to molecular electronics, Coord. Chem. Rev. , 2022, 461 , 214501; b) M. Camarasa-Gómez, D. Hernangómez-Pérez, M. S. Inkpen, G. Lovat, E. D. Fung, X. Roy, L. Venkataraman and F. Evers, Mechanically Tunable Quantum Interference in Ferrocene-Based Single-Molecule Junctions, Nano Lett , 2020, 20 , 6381-6386.4. a) X. Wang, G. Guerin, H. Wang, Y. Wang, I. Manners and M. A. Winnik, Cylindrical Block Copolymer Micelles and Co-Micelles of Controlled Length and Architecture, Science , 2007, 317 , 644-647; b) L. Ma, Y. Liu, Y. Liu, S. Jiang, P. Li, Y. Hao, P. Shao, A. Yin, X. Feng and B. Wang, Ferrocene‐Linkage‐Facilitated Charge Separation in Conjugated Microporous Polymers, Angew. Chem. Int. Ed. , 2019, 58 , 4221-4226; c) L. Zhao, X. Liu, L. Zhang, G. Qiu, D. Astruc and H. Gu, Metallomacromolecules containing cobalt sandwich complexes: Synthesis and functional materials properties, Coord. Chem. Rev. , 2017, 337 , 34-79.5. D. Kumar, M. Deb, J. Singh, N. Singh, K. Keshav and A. J. Elias, Chemistry of the highly stable hindered cobalt sandwich compound (η5-Cp)Co(η4-C4Ph4) and its derivatives, Coord. Chem. Rev. , 2016, 306 , 115-170.6. a) P. D. Byrne, D. Lee, P. Müller and T. M. Swager, Polymerization of thiophene containing cyclobutadiene Co cyclopentadiene complexes, Synth. Met. , 2006, 156 , 784-791; b) M. Altmann and U. H. F. Bunz, Synthesis and characterization of a poly[(para‐cyclobutadienylenecyclopentadienylcobalt)butadiynylene], a butadiynecyclobutadiene copolymer, Macromol. Rapid Commun. , 1994, 15 , 785-789; c) M. Altmann, V. Enkelmann, G. Lieser and U. H. F. Bunz, Synthesis of novel polymers containing cyclobutadiene thiophene and alkyne units: polymeric organometallic mesogens**, Adv. Mater. , 1995, 7 , 726-728; d) I. L. Rozhanskii, I. Tomita and T. Endo, Synthesis of Liquid-Crystalline Polyesters with (η4-Cyclobutadiene)cobalt Moieties in the Main Chain, Macromolecules , 1997, 30 , 1222-1224.7. a) S. Yamago, E. Kayahara and T. Iwamoto, Organoplatinum-Mediated Synthesis of Cyclic π-Conjugated Molecules: Towards a New Era of Three-Dimensional Aromatic Compounds, Chem. Rec. , 2014, 14 , 84-100; b) Y. Li, H. Kono, T. Maekawa, Y. Segawa, A. Yagi and K. Itami, Chemical Synthesis of Carbon Nanorings and Nanobelts, Acc. Mater. Res. , 2021, 2 , 681-691; c) M. Hermann, D. Wassy and B. Esser, Conjugated Nanohoops Incorporating Donor, Acceptor, Hetero- or Polycyclic Aromatics, Angew. Chem. Int. Ed. , 2021, 60 , 15743-15766; d) S. Zhong, L. Zhu, S. Wu, Y. Li and M. Lin, Photoactive donor-acceptor conjugated macrocycles: New opportunities for supramolecular chemistry, Chin. Chem. Lett. , 2023, 34 , 108124.8. a) U. H. F. Bunz, G. Roidl, M. Altmann, V. Enkelmann and K. D. Shimizu, Synthesis and Structural Characterization of Novel Organometallic Dehydroannulenes with Fused CpCo-Cyclobutadiene and Ferrocene Units Including a Cyclic Fullerenyne Segment, J. Am. Chem. Soc. , 1999, 121 , 10719-10726; b) U. H. F. Bunz, G. Roidl and R. D. Adams, A novel weakly diatropic dehydroannulene containing the cyclobutadiene(cyclopentadienyl)cobalt unit. An organometallic dehydroannulene that obeys Hückel’s rule, J. Organomet. Chem. , 2000, 600 , 56-62.9. G. Bertrand, L. Tortech, D. Fichou, M. Malacria, C. Aubert and V. Gandon, An Improved Protocol for the Synthesis of [(η4-C4R4)Co(η5-C5H5)] Complexes, Organometallics , 2012, 31 , 126-132.10. a) G. Fuhrmann, T. Debaerdemaeker and P. Bäuerle, C–C bond formation through oxidatively induced elimination of platinum complexes—A novel approach towards conjugated macrocycles, Chem. Commun. , 2003, 948-949; b) F. Zhang, G. Götz, H. D. F. Winkler, C. A. Schalley and P. Bäuerle, Giant Cyclo[n]thiophenes with Extended π Conjugation, Angew. Chem. Int. Ed. , 2009, 48 , 6632-6635.11. S. Yamago, Y. Watanabe and T. Iwamoto, Synthesis of [8]cycloparaphenylene from a square-shaped tetranuclear platinum complex, Angew. Chem. Int. Ed. , 2010, 49 , 757-759.12. a) S. Hitosugi, W. Nakanishi, T. Yamasaki and H. Isobe, Bottom-up synthesis of finite models of helical (n,m)-single-wall carbon nanotubes, Nat. Commun. , 2011, 2 , 492; b) H. Zhao, Y.-C. Ma, L. Cao, S. Huang, J.-P. Zhang and X. Yan, Synthesis and Photophysical Properties of Chalcophenes-Embedded Cycloparaphenylenes, J. Org. Chem. , 2019, 84 , 5230-5235.13. B. Lan, J. Xu, L. Zhu, X. Chen, H. Kono, P. Wang, X. Zuo, J. Yan, A. Yagi, Y. Zheng, S. Chen, Y. Yuan, K. Itami and Y. Li, Side-Chain Type Ferrocene Macrocycles, Precis. Chem. , 2024, 2 , 143-150.14. a) Y. Segawa, H. Omachi and K. Itami, Theoretical Studies on the Structures and Strain Energies of Cycloparaphenylenes, Org. Lett. , 2010, 12 , 2262-2265; b) E. R. Darzi and R. Jasti, The dynamic, size-dependent properties of [5]–[12]cycloparaphenylenes, Chem. Soc. Rev. , 2015, 44 , 6401-6410.15. C. E. Colwell, T. W. Price, T. Stauch and R. Jasti, Strain visualization for strained macrocycles, Chem. Sci. , 2020, 11 , 3923-3930. Manuscript received: XXXX, 2024 Manuscript revised: XXXX, 2024 Manuscript accepted: XXXX, 2024 Version of record online: XXXX, 2024 Supplementary Material File (image11.wmf) Download 79.84 KB File (image4.emf) Download 281.06 KB Information & Authors Information Version history V1 Version 1 15 July 2025 Peer review timeline Published Organic Letters Version of Record 22 Sep 2025 Published Copyright This work is licensed under a Non Exclusive No Reuse License. Keywords conjugated macrocycle cpcocb cyclobutadiene metallo-macrocycles multi-redox nanohoop Authors Affiliations Lingyun Zhu Fuzhou University College of Chemistry View all articles by this author Gang Xu Fuzhou University College of Chemistry View all articles by this author Jianwei Liang Tongji University School of Materials Science and Engineering View all articles by this author Jianfeng Yan Fuzhou University College of Chemistry View all articles by this author Yaofeng Yuan Fuzhou University College of Chemistry View all articles by this author Zheng Zhou Tongji University School of Materials Science and Engineering View all articles by this author Yuanming Li 0000-0003-3180-1305 [email protected] Fuzhou University College of Chemistry View all articles by this author Metrics & Citations Metrics Article Usage 169 views 136 downloads .FvxKWukQNSOunydq8rnd { width: 100px; } Citations Download citation Lingyun Zhu, Gang Xu, Jianwei Liang, et al. Side-Chain Type Metallo-Macrocycles: η5-cyclopentadienylcobalt-η4-cyclobutadiene Incorporated Conjugated Macrocycle. Authorea . 15 July 2025. DOI: https://doi.org/10.22541/au.175256494.44851855/v1 If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download. For more information or tips please see 'Downloading to a citation manager' in the Help menu . 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