Communication pubs.acs.org/crystal
Cite This: Cryst. Growth Des. XXXX, XXX, XXX−XXX
Ring-Opening Polymeric Single-Crystal-to-Single-Crystal Transformation in a Co(II) Compound Wen-Ting Deng,† Ze-Bin Shen,† Li-Jie Su,† Yu-Hui Hua,† Zhi-Xin Chen,† and Jun Tao*,†,‡ †
Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, People’s Republic of China ‡ Key Laboratory of Cluster Science of Ministry of Education, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, People’s Republic of China S Supporting Information *
ABSTRACT: The reaction of the flexible ligand 2,5-bis((pyridin-2-ylmethyl)thio)-1,3,4-thiadiazole (bptz) with cobalt(II) chloride afforded a mononuclear cyclic compound [CoCl2(bptz)]·1/2MeCN (1), which in the solid state quickly transformed through an irreversible ring-opening polymeric process to a one-dimensional compound [CoCl2(bptz)] (2), triggered by the loss of lattice solvent molecules at room temperature. The transformation involved the reconstruction of coordination bonds and drastic changes in the ligand conformation, which thus resulted in vigorous lattice variations. Self-consistent-charge density-functional tight-binding (SCCDFTB) calculations confirmed that this transformation was spontaneous. This result not only means the realization of solidstate single-crystal-to-single-crystal transformation, but also gives a deep insight into the mechanism of bond reconstruction.
T
can move and/or rotate easily.30,31 However, ROP SCSC transformation in the solid state has never been observed. Herein, we report the first example of spontaneous ROP SCSC transformation in the solid state, from 0D-[CoCl2(bptz)]·1/ 2MeCN [1, bptz = 2,5-bis((pyridin-2-ylmethyl)thio)-1,3,4thiadiazole] to its polymorphic structure 1D-[CoCl2(bptz)] (2), which results from the reconstruction of coordination bonds and leads to significant changes in the crystal structures. Compound 1 was synthesized from cobalt(II) chloride and bptz in acetonitrile (Supporting Information). The diffusion of diethyl ether into the acetonitrile solution afforded large block blue crystals of 1. When the crystals (1) were exposed to air at room temperature, the crystals began to crack and then splintered into fragile plates. In addition, crystallographic studies revealed that the new blue plate-like crystals were compound 2. The transformation could complete within several days, as supported by the powder X-ray diffraction data (Figures S1 and S2). Compound 1 crystallized in the monoclinic space group P21/n, and in the asymmetric unit there is a whole complex [CoCl2(bptz)] and one-half MeCN molecule. The Co(II) ion is four-coordinated with two chloride ions and two pyridyl-N atoms from the same ligand bptz, featuring a distorted tetrahedral coordination geometry and closed cyclic complex (Figure 1a). The Co−N distances are 2.021(5) Å and 2.040(5)
he occurrence of polymorphism, i.e., the same structural unit forms two or more crystalline states, has led to the formation of various polymorphic materials, which have applications in gas adsorption,1 sensing,2 catalysis,3 magnetism,4 medicine,5 and so on. Because of the nature of polymorphism, polymorphic materials are the very repositories for studying the structure−property relationships. It is intuitive that polymorphic materials can be obtained not only through in situ crystallization but also through single-crystal-to-singlecrystal (SCSC) transformation. In fact, SCSC transformation can give rise to more interesting structures than polymorphic materials, e.g., to achieve structures with different structural units. To date, SCSC transformations showing 0D-to-2D,6−8 1D-to-2D,9,10 and 2D-to-3D11−13 conversions have been documented. In this respect, SCSC transformations are usually spontaneous or induced by heat,14−16 light,17,18 and guest molecules,19−23 and can be ascribed to the two mechanisms of epitactic/topotactic and reconstruction,24,25 of which the epitactic/topotactic mechanism is responsible for most SCSC transformations that result in less structural changes.26−28 For the second mechanism, the SCSC transformations usually lead to huge changes in the structures so that it is difficult to obtain crystals suitable for single-crystal crystallographic studies. The “ring-opening polymerization (ROP)”29 is a special case for the second mechanism, referring to the SCSC transformation from a finite cyclic structure to an infinite structure. The ROP mechanism can commonly happen in solution or at liquid−solid interface because of where the finite molecules © XXXX American Chemical Society
Received: November 12, 2017 Revised: December 20, 2017 Published: December 28, 2017 A
DOI: 10.1021/acs.cgd.7b01584 Cryst. Growth Des. XXXX, XXX, XXX−XXX
Crystal Growth & Design
Communication
Figure 1. Perspective view of the molecular structures of compounds 1 (a, lattice MeCN is omitted) and 2 (b) and the SCSC transformation process showing bond reconstruction (c, molecules with blue bonds are taken as examples for showing bond reconstruction). Hydrogen atoms are omitted for clarity. Symmetry code: (a) x − 1, y − 1, z − 1.
Figure 2. Photograph showing morphological change from compound 1 to compound 2.
The crystal structure of compound 2 has the triclinic space group P1̅, in which the ligand bptz coordinates to Co(II) ion in the exo-bidentate bridging mode. As shown in Figure 1b, the coordination geometry of Co(II) ion is also tetrahedral, completed by two chloride ions and two pyridyl-N atoms from two bptz ligands. The Co−N distances are 2.034(5) Å and 2.043(5) Å, and the Co−Cl distances are 2.230(2) Å and 2.243(2) Å, respectively, showing slightly longer Co−N distances after SCSC transformation. The dihedral angles between thiadiazole and the two pyridyl rings in compound 2 are 52.7(2)° and 69.3(2)°, and the dihedral angle between the two pyridyl rings is 65.9(2)°, respectively, while the α2 and β2 angles (Figure 1b) are 101.1(3)°/100.5(3)° and 115.4(5)°/ 113.9(5)°, indicating that the tension embedded in compound 1 has been largely released. The Co(II) ions are bridged through bptz ligands to form 1D chain structures, which in the a-axis direction interacts with each other through various weak interactions to form pairs of 1D structures (Figure S5). These interactions mainly consist of Cmethylene−H···Cl (3.772(7) Å) and Cpyridyl−H···Cl (3.597(8) Å and 3.603(7) Å) hydrogen bonds. And in the 1D-chain pair, the intra- and interchain
Å, and the Co−Cl distances are 2.238(2) Å and 2.239(2) Å, respectively, which are typical values for a tetrahedral [CoN2Cl2] moiety.32 In compound 1, the dihedral angles between thiadiazole and two pyridyl rings are 81.2(2)° and 81.5(2)°, and the dihedral angle between the two pyridyl rings is 82.0(2)°, respectively, while the α1 and β1 angles (Figure 1a) are 99.2(3)°/99.0(3)° and 112.3(4)°/111.9(4)°. The nearly right dihedral angles and small α1 and β1 angles may exert strong stretching forces on the Co−N/Cl bonds, and thus these stretching forces can be released under certain circumstance and structural transformation may take place. The adjacent complexes along the a-axis direction interact with each other through the Cmethylene−H···Cl hydrogen bonds (140.5(4)°, 3.641(6) Å), resulting in a pseudo 1D chain with a nearest Co···Co distance of 8.913 Å (Figure S3). The adjacent complexes in the bc plane (Figure S4) stack via C−H···Cl hydrogen bond33 with a distance of 3.602(1) Å and S···Cl interactions (3.501(1) and 3.561(1) Å),34 respectively, forming a 2D supramolecular structure possessing voids that are occupied by lattice disordered acetonitrile molecules (Figure 1c, left). B
DOI: 10.1021/acs.cgd.7b01584 Cryst. Growth Des. XXXX, XXX, XXX−XXX
Crystal Growth & Design
Communication
compare the thermodynamic stability of the two compounds (Figure 3). The calculations on the cyclic and chain structures
nearest Co···Co distances are 13.813 and 6.113 Å, respectively. While in the bc plane, the 1D-chain pairs parallel stack along the c-axis direction through offset π···π interactions (centroid− centroid distance of 3.734 Å) between pyridyl groups of adjacent 1D pairs (Figure 1c, right). The ring-opening polymeric SCSC transformation took place in the solid state when the well-shaped crystals of compound 1 were left in air for several days (Figure 2). The transformation was accompanied by a morphological change from block to cracked plate, which most probably arose from huge lattice changes (Tables S1 and S2). Single crystals suitable for crystallographic studies are available by carefully separating the plate-like samples. By comparing the two structures in the bc planes in detail (Figure 1c), we can briefly illustrate how the cyclic structure of compound 1 transforms to the 1D structure of compound 2. We first believe that the solvent molecules must play a critical role in the formation and crystallization of compound 1, and in the crystal lattice the presence of solvent molecules may help to stabilize the cyclic structure through chemical pressure (Figure 1c, left). Then, the loss of lattice solvent molecules in the solid state releases such chemical pressure and leaves void spaces, so the cyclic structure becomes less stable and one of the Co−N bonds can be broken in order to release the tension in the cyclic structure, and then the pyridyl ring is able to rotate and move to the void space. The movement of pyridyl rings may simultaneously bring about lattice changes and movements of remaining [CoCl2(py)] moieties, which de novo bind to the free pyridyl rings to form 1D chains (Figure 1c, right). We can find that the conformation of ligand bptz changes greatly along with the SCSC transformation, and the average changed values of α and β bond angles are 1.7° and 2.5°, respectively. While the dihedral angles of thiadiazole−pyridine and pyridine− pyridine pairs vary from 81.2°/81.5° and 82.0° to 52.7°/69.3° and 65.9°, respectively, these variations are apparently larger than those of α and β bond angles and may be the driving force to reconstruct Co−N bonds. For comparison, we tried to synthesize a six-coordinated cyclic compound using the same ligand and studied whether it could transform to a chain structure. However, using a different anion such as nitrate could only result in the formation of chain structure with six-coordinated Co(II) geometry (compound 3, Figures S6 and S7), which did not show SCSC transformation. These results suggest that compound 1 can transform to compound 2 partly because four-coordinated Co(II) geometry is less stable than a sixcoordinated one. For a better understanding of the mechanism of SCSC transformation, thermogravimetric analysis (TGA) was performed to determine the loss of solvent molecules (Figure S8). The TGA curve exhibited the first weight loss (4.36%) of compound 1 that was completed below 200 °C, corresponding to the removal of cocrystallized acetonitrile (calculated weight loss: 4.25%), whereas compound 2 was stable up to 260 °C, indicating no solvent molecules in the lattice. Abrupt weight losses of compounds 1−2 both appeared at 260 °C, which were attributed to the decomposition of structures and the losses of ligands. The SCSC transformation involves the rotation of pyridyl rings in order to release tension in the cyclic structure, i.e., the coordination modes of pyridyl rings changing from “cis” to “anti” (Figure 1a,b). The self-consistent-charge density-functional tight-binding (SCC-DFTB) method was employed to
Figure 3. Calculated energy levels of the cyclic structure and the chain structure.
reveal that the cyclic structure is 349.19 kJ mol−1 higher than the chain structure, which indicates that compound 2 is more stable than compound 1, and the SCSC transformation is energetically spontaneous. In conclusion, we have reported the first example of solidstate SCSC transformation through a spontaneous ringopening polymeric process in the solid state, which occurs accompanying by bond reconstruction that is based on a flexible ligand being able to release strong tension embedded within the cyclic structure and driven by the loss of lattice solvent molecules. The spontaneous transformation has been confirmed by theoretical calculations. This kind of SCSC in the solid state may open a new avenue to realize structural transformation that is normally unachievable.
■
ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.cgd.7b01584. Experimental details, tables of bond lengths and angles, additional figures including IR spectra and PXRD patterns, DFT calculation (PDF) Accession Codes
CCDC 1555759−1555760 and 1812189 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/ cif, or by emailing
[email protected], or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
■
AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected];
[email protected]. ORCID
Jun Tao: 0000-0003-0610-4305 Notes
The authors declare no competing financial interest.
■
ACKNOWLEDGMENTS We gratefully acknowledge the financial support from the National Natural Science Foundation of China (Grants 21325103 and 21671161) and the National Key Basic Research Program of China (Grant 2014CB845601). We C
DOI: 10.1021/acs.cgd.7b01584 Cryst. Growth Des. XXXX, XXX, XXX−XXX
Crystal Growth & Design
Communication
Framework into a Porous Metal-Organic Framework via a Solid-State Reaction. Inorg. Chem. 2017, 56, 12337−12347. (16) Yan, Z. H.; Li, X. Yu.; Liu, L. W.; Yu, S. Q.; Wang, X. P.; Sun, D. Single-Crystal to Single-Crystal Phase Transition and Segmented Thermochromic Luminescence in a Dynamic 3D Interpenetrated AgI Coordination Network. Inorg. Chem. 2016, 55, 1096−1101. (17) Chatterjee, P. B.; Audhya, A.; Bhattacharya, S.; Abtab, S. M. T.; Bhattacharya, K.; Chaudhury, M. Single Crystal-to-Single Crystal Irreversible Transformation from a Discrete Vanadium(V)-Alcoholate to an Aldehydic-Vanadium(IV) Oligomer. J. Am. Chem. Soc. 2010, 132, 15842−15845. (18) Kitagawa, D.; Kawasaki, K.; Tanaka, R.; Kobatake, S. Mechanical Behavior of Molecular Crystals Induced by Combination of Photochromic Reaction and Reversible Single-Crystal-to-SingleCrystal Phase Transition. Chem. Mater. 2017, 29, 7524−7532. (19) Costa, J. S.; Rodriguez-Jiménez, S. R.; Craig, G. A.; Barth, B.; Beavers, C. M.; Teat, S. J.; Aromí, G. Three-Way Crystal-to-Crystal Reversible Transformation and Controlled Spin Switching by a Nonporous Molecular Material. J. Am. Chem. Soc. 2014, 136, 3869− 3874. (20) Das, A.; Klinke, F. J.; Demeshko, S.; Meyer, S.; Dechert, S.; Meyer, F. Reversible Solvatomagnetic Effect in Novel Tetranuclear Cubane Type Ni4 Complexes and Magneto structural Correlations for the [Ni4(μ3O)4] Core. Inorg. Chem. 2012, 51, 8141−8149. (21) Chaudhary, A.; Mohammad, A.; Mobin, S. M. Recent Advances in Single-Crystal-to-Single-Crystal Transformation at the Discrete Molecular Level. Cryst. Growth Des. 2017, 17, 2893−2910. (22) He, Y. C.; Yang, J.; Liu, Y. Y.; Ma, J. F. Series of SolventInduced Single-Crystal to Single-Crystal Transformations with Different Sizes of Solvent Molecules. Inorg. Chem. 2014, 53, 7527− 7533. (23) Song, X. Z.; Song, S. Y.; Zhao, S. N.; Hao, Z. M.; Zhu, M.; Meng, X.; Wu, L. L.; Zhang, H. J. Single-Crystal-to-Single-Crystal Transformation of a Europium(III) Metal-Organic Framework Producing a Multi-Responsive Luminescent Sensor. Adv. Funct. Mater. 2014, 24, 4034−4041. (24) Khatua, S.; Goswami, S.; Biswas, S.; Tomar, K.; Jena, H. S.; Konar, S. Stable Multiresponsive Luminescent MOF for Colorimetric Detection of Small Molecules in Selective and Reversible Manner. Chem. Mater. 2015, 27, 5349−5360. (25) Krishnan, B. P.; Sureshan, K. M. A Spontaneous Single-Crystalto-Single-Crystal Polymorphic Transition Involving Major Packing Changes. J. Am. Chem. Soc. 2015, 137, 1692−1696. (26) Mobin, S. M.; Srivastava, A. K.; Mathur, P.; Lahiri, G. K. VaporDiffusion-Mediated Single Crystal-to-Single Crystal Transformation of a Discrete Dimeric Copper(II). Inorg. Chem. 2009, 48, 4652−4654. (27) Wang, C. M.; Chang, T. Y.; Lee, L. W.; Lin, H. M.; Lu, K. L.; Lii, K. H. The First Zinc Phosphite with Remarkable Structural and Functional Transformations. Chem. Commun. 2015, 51, 7824−7826. (28) Ye, J. W.; Lin, J. M.; Mo, Z. W.; He, C. T.; Zhou, H. L.; Zhang, J. P.; Chen, X. M. Mixed-Lanthanide Porous Coordination Polymers Showing Range Tunable Ratiometric Luminescence for O2 Sensing. Inorg. Chem. 2017, 56, 4238−4243. (29) James, S. L. Ring-Opening Polymerization of Coordination Rings and Cages. Macromol. Symp. 2004, 209, 119−131. (30) Vittal, J. J. Supramolecular Structural Transformations Involving Coordination Polymers In the Solid State. Coord. Chem. Rev. 2007, 251, 1781−1795. (31) Jiang, J. J.; He, J. R.; Lu, X. Q.; Wang, D. W.; Li, G. B.; Su, C. Y. Structural Disorder and Transformation In Crystal Growth: Direct Observation of Ring-Opening Isomerization in a Metal-Organic Solid Solution. IUCrJ 2014, 1, 318−327. (32) Xi, Y. R.; Wei, W.; Xu, Y. Q.; Huang, X. Q.; Zhang, F. Z.; Hu, C. W. Coordination Polymers Based on Substituted Terpyridine Ligands: Synthesis, Structural Diversity, and Highly Efficient and Selective Catalytic Oxidation of Benzylic C-H Bonds. Cryst. Growth Des. 2015, 15, 2695−2702.
thank Professor Ye Wang at Xiamen University for his technical support.
■
REFERENCES
(1) Du, M.; Li, C. P.; Chen, M.; Ge, Z. W.; Wang, X.; Wang, L.; Liu, C. S. Divergent Kinetic and Thermodynamic Hydration of a Porous Cu(II) Coordination Polymer with Exclusive CO 2 Sorption Selectivity. J. Am. Chem. Soc. 2014, 136, 10906−10909. (2) Bao, S. S.; Li, N. Z.; Taylor, J. M.; Shen, Y.; Kitagawa, H.; Zheng, L. M. Co-Ca Phosphonate Showing Humidity-Sensitive Single Crystal to Single Crystal Structural Transformation and Tunable Proton Conduction Properties. Chem. Mater. 2015, 27, 8116−8125. (3) Wang, Y.; Meng, S. S.; Lin, P. X.; Xiao, Y. W.; Ma, Q. Q.; Xie, Q.; Chen, Y. Y.; Zhao, X. J.; Chen, J. Solvent-Induced Single CrystalSingle Crystal Transformation of an Interpenetrated Three-Dimensional Copper Triazole Catalytic Framework. Inorg. Chem. 2016, 55, 4069−4071. (4) Cheng, X. N.; Zhang, W. X.; Chen, X. M. Single Crystal-toSingle Crystal Transformation from Ferromagnetic Discrete Molecules to a Spin-Canting Antiferromagnetic Layer. J. Am. Chem. Soc. 2007, 129, 15738−15739. (5) Marques, M. P. M.; Valero, R.; Parker, S. F.; Tomkinson, J.; Batista de Carvalho, L. A. E. Polymorphism in Cisplatin Anticancer Drug. J. Phys. Chem. B 2013, 117, 6421−6429. (6) Park, I. H.; Medishetty, R.; Kim, J. Y.; Lee, S. S.; Vittal, J. J. Distortional Supramolecular Isomers of Polyrotaxane Coordination Polymers: Photoreactivity and Sensing of Nitro Compounds. Angew. Chem., Int. Ed. 2014, 53, 5591−5595. (7) Cheng, P. C.; Yeh, C. W.; Hsu, W.; Chen, T. R.; Wang, H. W.; Chen, J. D.; Wang, J. C. Ag(I) Complexes Containing Flexible N, N′Di(3-pyridyl)adipoamide Ligands: Syntheses, Structures, Ligand Conformations, and Crystal-to-Crystal Transformations. Cryst. Growth Des. 2012, 12, 943−953. (8) Huang, Z.; White, P. S.; Brookhart, M. Ligand Exchanges and Selective Catalytic Hydrogenation in Molecular Single Crystals. Nature 2010, 465, 598−601. (9) Coronado, E.; Giménez-Marqués, M.; Espallargas, G. M. Combination of Magnetic Susceptibility and Electron Paramagnetic Resonance to Monitor the 1D to 2D Solid State Transformation in Flexible Metal-Organic Frameworks of Co(II) and Zn(II) with 1,4Bis(triazol-1-ylmethyl)benzene. Inorg. Chem. 2012, 51, 4403−4410. (10) Chhetri, P. M.; Yang, X. K.; Chen, J. D. Solvent-Mediated Reversible Structural Transformation of Mercury Iodide Coordination Polymers: Role of Halide Anions. Cryst. Growth Des. 2017, 17, 4801− 4809. (11) Huang, C.; Wu, J.; Song, C. J.; Ding, R.; Qiao, Y.; Hou, H. W.; Chang, J. B.; Fan, Y. T. Reversible Conversion of Valence-Tautomeric Copper Metal-Organic Frameworks Dependent Single-Crystal-toSingle-Crystal Oxidation/Reduction: a Redox-Switchable Catalyst for C-H Bonds Activation Reaction. Chem. Commun. 2015, 51, 10353− 10356. (12) Sharma, V.; Pal, S.; Saha, P.; Bharadwaj, P. K.; De, D. A 2D Coordination Network That Detects Nitro Explosives in Water, Catalyzes Baylis-Hillman Reactions, and Undergoes Unusual 2D→3D Single-Crystal to Single-Crystal Transformation. Inorg. Chem. 2017, 56, 8847−8855. (13) Wang, C. P.; Chen, W. M.; Qi, H.; Li, X. Y.; Rajnak, C.; Feng, Z. Y.; Kurmoo, M.; Boča, R.; Jia, C. J.; Tung, C. H.; Sun, D. SolventControlled Phase Transition of a CoII-Organic Framework: From Achiral to Chiral and Two to Three Dimensions. Chem. - Eur. J. 2017, 23, 7990−7996. (14) Zhang, Y. J.; Liu, T.; Kanegawa, S.; Sato, O. Reversible SingleCrystal-to-Single-Crystal Transformation from Achiral Antiferromagnetic Hexanuclear to a Chiral Ferrimagnetic Double Zigzag Chain. J. Am. Chem. Soc. 2009, 131, 7942−7943. (15) Spirkl, S.; Grzywa, M.; Reschke, S.; Fischer, J. K. H.; Sippel, P.; Demeshko, S.; Krug von Nidda, H. A.; Volkmer, D. Single-Crystal to Single-Crystal Transformation of a Nonporous Fe(II) Metal-Organic D
DOI: 10.1021/acs.cgd.7b01584 Cryst. Growth Des. XXXX, XXX, XXX−XXX
Crystal Growth & Design
Communication
(33) Bryantsev, V. S.; Hay, B. P. Are C-H Groups Significant Hydrogen Bonding Sites in Anion Receptors? Benzene Complexes with Cl−, NO3−, and ClO4−. J. Am. Chem. Soc. 2005, 127, 8282−8283. (34) Bondi, A. Van der Waals Volumes and Radii. J. Phys. Chem. 1964, 68, 441−451 The van der Waals radii of Cl and S are chosen as 1.75 and 1.80 Å, respectively..
E
DOI: 10.1021/acs.cgd.7b01584 Cryst. Growth Des. XXXX, XXX, XXX−XXX
