Metal Organo-Polymeric Framework via [2 + 2] Cycloaddition Reaction

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Metal Organo-Polymeric Framework via [2 + 2] Cycloaddition Reaction: Influence of Hydrogen Bonding on Depolymerization Published as part of a Crystal Growth and Design virtual special issue Honoring Prof. William Jones and His Contributions to Organic Solid-State Chemistry In-Hyeok Park,†,# Kenta Sasaki,†,§,# Hong Sheng Quah,† Eunji Lee,‡ Masaaki Ohba,§ Shim Sung Lee,*,‡ and Jagadese J. Vittal*,† Downloaded via WEBSTER UNIV on February 15, 2019 at 00:48:15 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.

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Department of Chemistry, National University of Singapore, 3 Science Drive 3, 117543, Singapore Department of Chemistry and Research Institute of Natural Science, Gyeongsang National University, Jinju 52828, South Korea § Department of Chemistry, Faculty of Science, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan ‡

S Supporting Information *

ABSTRACT: In the doubly interpenetrated metal−organic framework (MOF) structure with cds topology, [Zn2(bpeb)(dhbdc)(fa)2], 1 (where bpeb = trans,trans,trans-1,4-bis[2-(4′pyridyl)ethenyl]benzene, dhbdc = 2,5-dihydroxy-benzene-1,4dicarboxylate, and fa = formate), the adjacent bpeb ligands are aligned in a slip-stacked manner infinitely, and the olefin pairs are aligned in parallel ready to undergo a quantitative photochemical [2 + 2] cycloaddition reaction. The singlecrystal-to-single-crystal (SCSC) photoreaction under UV light yielded a non-interpenetrated [Zn2(poly-bppcb)(dhbdc)(fa)2], 2 (where poly-bppcb = 1,3-(4,4′-bipyridyl)-2-phenylcyclobutane) in which the poly-bppcb polymer comprising cyclobutane rings are nicely integrated into the two-dimensional coordination polymeric sheet formed by [Zn2(dhbdc)(fa)2]. This organic polymer can be depolymerized back to 1 by heating 2 at 250 °C in a hot air oven for 6 h. The cleavage of cyclobutane rings to bpeb ligands has been attributed to the hydrogen bonding of the two hydroxy groups in the dhbdc ligand. In a similar metal organo-polymeric framework with bdc ligand, the poly-bppcb could not be depolymerized. Thus, this study provided some new insights into the reversible cleavage of cyclobutane polymers. These polymeric materials based on cyclobutane may be environmentally benign as these can be depolymerized to yield easily disposable and degradable monomers.

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formate anion19−23 and exhibit very interesting magnetic properties.18−22 In one of the photoreactive nonporous MOFs, the formate ion has been assimilated incidentally by the partial hydrolysis of DMF.12 The photochemical [2 + 2] cycloaddition reaction in this MOF led to the polymerization of the trans,trans,trans-1,4-bis[2-(4′-pyridyl)ethenyl]benzene (bpeb) ligands forming an interesting MOPF. But the cyclobutane polymers formed cannot be depolymerized as in the case of another photoreactive MOF.9 Biradha et al. have shown that hydrogen bonding in these solids have shock

INTRODUCTION For the past two decades, coordination polymers (CPs) or metal−organic frameworks (MOFs) have developed into a very productive research field due to their tunability, structural diversity, designable architectures, and their range of physical and chemical properties.1−3 Recently, covalent-organic frameworks (COFs) have also emerged as interesting organic lightweight materials with similar properties.4−6 Another class of crystalline polymeric materials, called metal organo-polymeric frameworks (MOPFs) which comprises CPs and organic polymers fused together, has started to emerge.7−12 The incorporation of organic polymers based on cyclobutane rings in the organic single crystals has been achieved indirectly by linking the olefin bonds through [2 + 2] cycloaddition reactions as also reported in many organic solids.13−16 Single crystals of a silver(I) complex of an organic polymer ligand were synthesized by Garai and Biradha by this elegant approach.8 Dimethylformamide (DMF) is well-known to hydrolyze under solvothermal/hydrothermal conditions to generate formate anion and dimethyl amine.17,18 In many cases, the resultant MOF structures have been found to incorporate the © XXXX American Chemical Society

absorbing nature to maintain single crystals after the photopolymerization reactions.14−16 Hence, we wanted to study the Received: January 4, 2019 Revised: February 6, 2019

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DOI: 10.1021/acs.cgd.9b00018 Cryst. Growth Des. XXXX, XXX, XXX−XXX

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Figure 1. (a) A view showing the coordination geometry at the Zn(II) atom. (b) A portion of the [Zn(fa)] chain in 1. (c) A brick-like 2D structure formed by [Zn(dhbdc)(fa)2] in 1. (d) A perpendicular view of [Zn(dhbdc)(fa)2] showing the orientations of the bpeb ligands.

Information) with Schlafli symbol {65·8}. The large void produced in this connectivity is filled by 2-fold interpenetration (Figure S2b) with little solvent accessible void. Hence there is no solvent present in this nonporous MOF. It may be noted that the hydroxy group of the dhbdc ligand was neither deprotonated nor bonded to Zn1, and strong intramolecular O−H···O hydrogen bonds between hydroxy groups and one of the oxygen atoms of the carboxylate group were retained (Table S2). Figure 2 shows the relative orientations of the bpeb ligands in the interpenetrated structures. The adjacent bpeb ligands are infinitely arranged closely in a slip-stacked manner. The phenylene rings are closer to the adjacent pyridyl groups (centroid to centroid distance of 3.616(2) Å) showing face-to-

influence of 2,5-dihydroxy-benzene-1,4-dicarboxylate (dhbdc) on photopolymerization and depolymerization of a MOPF instead of the 1,4-bdc ligand. Here we found that the depolymerization could be achieved in the solid state by the presence of strong intramolecular hydrogen bonds. The details of our investigations are described below.

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RESULTS AND DISCUSSION Orange needle single crystals of [Zn2(bpeb)(dhbdc)(fa)2] (1) (where fa = formate ion) were synthesized from Zn(NO3)2· 4H2O, 1,4-benzenedicarboxylic acid (H2dhbdc), and bpeb in a mixture of DMF and water at 100 °C, followed by slow cooling. The formate ligand in the compound 1 is due to the partial hydrolysis of DMF solvent under solvothermal conditions.12 Single crystal X-ray crystallography (SC-XRD) experiments revealed that the asymmetric unit has half of the atoms in the formula unit of 1 (see Table S1 in the Supporting Information). Crystallographic center of inversion is present in the middle of bpeb and dhbdc ligands. Figure 1a shows the coordination environment around Zn(II). The formate ligand forms a onedimensional polymeric chain with Zn(II) carrying bpeb and dhbda at the Zn(II) atom (Figure 1b). If we neglect the weak Zn1−O2 distance of 2.791(2) Å (the sum of van der Waals’ radii of zinc and oxygen, 2.91 Å), then Zn1 has highly distorted tetrahedral coordination geometry with a O3N core similar to the bdc analogue.12 In 1, the Zn(II) atoms are bridged by the formate ligands generating a chain propagating along the [1̅01] direction and further cross-linked by dhbdc ions establishing a brick-wall type [6,3] grid made from [Zn2(dhbdc)(fa)2] (Figure 1c,d). The 3D coordination polymer is produced by the connectivity of the bpeb spacer ligand. The alternate bpeb ligands in the [Zn(fa)2] chain are pointing in the same direction by the tetrahedral geometry of the Zn(II) atom, as shown in Figure 1d. Viewed along the a-axis, all these layers are well aligned, leaving the bpeb ligands to occupy the channels. The resultant connectivity generated the cds topology in 1 (see Figure S1 in the Supporting

Figure 2. A slip-stacked alignment of the neighboring bpeb ligands in 1 showing only the relevant atoms. B

DOI: 10.1021/acs.cgd.9b00018 Cryst. Growth Des. XXXX, XXX, XXX−XXX

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Figure 3. (a) A ball-and-stick diagram showing the coordination environment of Zn1 in 2. (b) A selected portion of the structure of 2 is shown to highlight the formation of the poly-bppcb chain. The H atoms are omitted for clarity. (c) A view of the non-interpenetrated 3D structure of 2. No H atoms are shown. (d) The topological representation of the framework of 2. The poly-bppcb chain is shown in pink and gray represents [Zn(dhbdc)(fa)2] sheets. The non-interpenetrated net has jjv2 topology.12,25−27

face π−π interactions. This arrangement makes only a pair of CC bonds to be aligned in parallel between any two bpeb ligands, and the distance between the centers of CC bonds is 3.559(2) Å, which satisfies Schmidt’s photochemical criteria for [2 + 2] cycloaddition reaction.24 Hence, it is anticipated that the [2 + 2] cycloaddition reaction of 1 under UV light will furnish a cyclobutane ring based organic polymer that integrates with the [Zn2(dhbdc)(fa)2] layers forming an interesting MOPF structure. When the orange single crystals of 1 were irradiated under UV light for 2 h, beige cracked crystals of [Zn2(poly-bppcb)(dhbdc)(fa)2], (2) (where poly-bppcb = 1,3-(4,4′-bipyridyl)-2phenylcyclobutane) resulted (Table S1). However, a suitable single crystal for the SC-XRD intensity data could be found. Further characterization of 2 by routine solution 1H NMR spectroscopy was not possible due to its insolubility even in strong acids. This indicates indirectly that the expected organic polymer has formed. This behavior is very similar to that reported recently.9−12 However, the single crystals of 1 are soluble in DMSO-d6 with a drop of HNO3 assisting to distinguish 1 from 2 (Figure S3a). The SC-XRD of 2 confirmed the quantitative [2 + 2] cycloaddition reaction by structural transformation has occurred (Figure 3). Furthermore, the space group P21/n has been retained, and 2 is essentially isomorphous to 1. Further, there is a very small increase in the volume of the unit cell (1339.4(1) Å3 in 1 to 1366.3(2) Å3 in 2). The overall structural description of the [Zn2(dhbdc)(fa)2] layer is the same as 1. The coordination geometry of Zn(II) in 2 has changed to a highly distorted square-pyramidal coordination geometry due to the Zn1−O2 bond (with a distance of 2.16(2) Å as compared to 2.791(3) Å in

1) with both oxygen atoms of the carboxylate ligand of dhbdc chelating the Zn1 atom (Figure 3a).12 It may also be noted that the intramolecular O−H···O hydrogen bonds between hydroxy groups and one of the oxygen atoms of the carboxylate group were retained (Table S3). Due to the formation of the polymer ligand, poly-bppcb, the original 2-fold interpenetrated net in 1 is fused into a single framework in 2 (Figure 3c,d). The organic ligand, poly-bppcb is connecting the Zn(II) atoms inside the channels formed by the [Zn(dhbdc)(fa)2] brick-wall layers along the a-axis. This SCSC photopolymerization of the bpeb ligands by [2 + 2] cycloaddition reaction is responsible for the structural transformation of a doubly interpenetrated nonporous MOF with cds topology to a non-interpenetrating network (Figure S4) having jjv2 topology described before with point symbol {62.83.10}{65.8}2 and vertex symbol [6.62.6.62.6.84] [62.62.85.85.86.1018] as shown in Figure 3d.12,25−27 When the compound 2 was heated at 250 °C in hot air oven for 6 h, the orange powder turned to a beige powder (1′) indicating the formation of 1. Since the heated product 1′ is soluble in DMSO-d6 with a drop of HNO3, its 1H NMR spectral data have been obtained and compared with that of 1 (Figure S3b). Apart from the solubility in the DMSO−HNO3 mixture and color changes of the solids, photoluminescence spectra and PXRD patterns were also recorded to distinguish 1 from 2 (Figures S5−S9). The reversibility of the photopolymerization/ thermal-depolymerization was also confirmed from experimental densities of the solids (Table S4). The polymerization and depolymerization reactions between 1 and 2 are depicted in Figure 4. C

DOI: 10.1021/acs.cgd.9b00018 Cryst. Growth Des. XXXX, XXX, XXX−XXX

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more experimental examples are needed, and computational work is in order to establish the actual role of hydrogen bonding to confirm these findings.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.cgd.9b00018. Experimental section, X-ray crystallographic analysis, PXRD, TGA, NMR, UV−vis, PL, crystal images, and structural figures (PDF)

Figure 4. A schematic diagram showing the reversible solid-state structural transformation involving polymerization and depolymerization of organic ligand based on cyclobutane rings.

Accession Codes

CCDC 1844235−1844236 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.

Biradha et al. have shown that the presence hydrogen bonding helps in absorbing shock during the drastic structural changes to preserve SCSC reactions.8,14−16 It may be noted that the two hydroxy groups of the dhbdc ligand in 1 are strongly intramolecularly hydrogen bonded to one of the oxygen atoms of the carboxylate ligands (Figure 1a). These hydrogen bonds are retained after the SCSC reaction (Figure 3a). Probably these hydrogen bonds are responsible for the reversible cleavage of the cyclobutane on heating. This has also been observed when 2amino-benzene-1,4-dicarboxylate was used.28 The hydrogen bonds do play a role in the solid state structural transformation as has been frequently documented in the literature.29−31 It is interesting to note that the introduction of a hydrogen bonding functionality in the backbone of the dicarboxylate not only retains the overall structure, photoreactivity of the MOF, and SCSC polymerization, but also assists the depolymerization reaction, i.e., cleavage of cyclobutane rings to bpeb monomers. Solid state photoluminescence spectra were recorded for 1 and 2 and compared with that of the bpeb ligand. The free ligand is weakly emissive in the yellow region, λmax = 558 nm when excited at λex = 360 nm. Compound 1 shows a strong green emission with a λmax at 507 nm, while 2 has a weaker emission which is blue-shifted to a stronger blue emission at λmax = 429 nm, which might be due to the loss of extended conjugation on polymerization (Figures S9 and S10). Two-photon emission spectra as an optical property were also recorded for 1 and 2. Compounds 1 and 2 show a weak yellow emission at λmax = 538 nm (Figures S11 and S12).

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AUTHOR INFORMATION

Corresponding Authors

*E-mail for S.S.L.: [email protected]. *E-mail for J.J.V.: [email protected]. ORCID

In-Hyeok Park: 0000-0003-1371-6641 Kenta Sasaki: 0000-0003-3160-3165 Hong Sheng Quah: 0000-0001-5041-7857 Eunji Lee: 0000-0002-3031-943X Masaaki Ohba: 0000-0001-9268-3512 Shim Sung Lee: 0000-0002-4638-5466 Jagadese J. Vittal: 0000-0001-8302-0733 Author Contributions #

I.P. and K.S. contributed equally to this work.

Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported by the Ministry of Education, Singapore (National University of Singapore Tier 1 Grant No. R-143-000-A12-114) and National Research Foundation of Korea (NRF) (2016R1A2A2A05918799 and 2017R1A4A1014595), South Korea. I.H.P. acknowledges the Overseas Postdoctoral Fellowship of Foresting Next-Generation Research Program through the NRF (2017R1A6A3A03006579).

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CONCLUSION In this work, the influence of hydrogen bonding on the photoreactivity of 1 with cds topology has been investigated. In this photoreactive nonporous MOF containing two different carboxylate spacer ligands, the formate ion was introduced inadvertently by the use of DMF in the solvothermal reaction. The presence of a slip-stacked arrangement of adjacent bpeb ligands in 1 promoted the alignment of one pair of CC bonds to satisfy the Schmidt’s photochemical criteria for a [2 + 2] cycloaddition reaction which led to the polymerization to produce a MOPF containing cyclobutane polymer, poly-bppcb fused with the 2D CP [Zn2(dhbdc)(fa)2]. Such a crystalline polymer is unlikely to be synthesized otherwise. Interestingly, the presence of a 2,5-dihydroxy group in dhbdc promotes the reversible cleavage of these butane rings back to bpeb by heating. Such depolymerization may help to recycle materials based on cyclobutane polymers, as the monomers are relatively easy to dispose of in an environmentally benign manner. One of the dreams of crystal engineers is to fine-tune the physical and chemical properties of crystalline materials.32,33 In any case,

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REFERENCES

(1) Li, H.; Eddaoudi, M.; O’Keeffe, M.; Yaghi, O. M. Design and synthesis of an exceptionally stable and highly porous metal-organic framework. Nature 1999, 402, 276−279. (2) Chui, S. S. Y.; Lo, S. M. F.; Charmant, J. P. H.; Orpen, A. G.; Williams, I. D. A Chemically Functionalizable Nanoporous Material [Cu3(TMA)2(H2O)3]n. Science 1999, 283, 1148−1150. (3) Kitagawa, S.; Kitaura, R.; Noro, S. i. Functional Porous Coordination Polymers. Angew. Chem., Int. Ed. 2004, 43, 2334−2375. (4) Côté, A. P.; Benin, A. I.; Ockwig, N. W.; Keeffe, M.; Matzger, A. J.; Yaghi, O. M. Porous, Crystalline, Covalent Organic Frameworks. Science 2005, 310, 1166−1170. (5) Colson, J. W.; Woll, A. R.; Mukherjee, A.; Levendorf, M. P.; Spitler, E. L.; Shields, V. B.; Spencer, M. G.; Park, J.; Dichtel, W. R. Oriented 2D Covalent Organic Framework Thin Films on Single-Layer Graphene. Science 2011, 332, 228−231.

D

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(6) Kandambeth, S.; Mallick, A.; Lukose, B.; Mane, M. V.; Heine, T.; Banerjee, R. Construction of Crystalline 2D Covalent Organic Frameworks with Remarkable Chemical (Acid/Base) Stability via a Combined Reversible and Irreversible Route. J. Am. Chem. Soc. 2012, 134, 19524−19527. (7) Medishetty, R.; Park, I.-H.; Lee, S. S.; Vittal, J. J. Solid-state polymerisation via [2 + 2] cycloaddition reaction involving coordination polymers. Chem. Commun. 2016, 52, 3989−4001. (8) Garai, M.; Biradha, K. Coordination polymers of organic polymers synthesized via photopolymerization of single crystals: two-dimensional hydrogen bonding layers with amazing shock absorbing nature. Chem. Commun. 2014, 50, 3568−3570. (9) Park, I.-H.; Chanthapally, A.; Zhang, Z.; Lee, S. S.; Zaworotko, M. J.; Vittal, J. J. Metal−Organic Organopolymeric Hybrid Framework by Reversible [2 + 2] Cycloaddition Reaction. Angew. Chem., Int. Ed. 2014, 53, 414−419. (10) Park, I.-H.; Medishetty, R.; Lee, H. H.; Mulijanto, C. E.; Quah, H. S.; Lee, S.S.; Vittal, J.J. Formation of a Syndiotactic Organic Polymer Inside a MOF by a [2 + 2] Photo-Polymerization Reaction. Angew. Chem., Int. Ed. 2015, 54, 7313−7317. (11) Park, I.-H.; Medishetty, R.; Lee, S. S.; Vittal, J. J. Solid-state polymerization in a polyrotaxane coordination polymer via a [2 + 2] cycloaddition reaction. Chem. Commun. 2014, 50, 6585−6588. (12) Park, I.-H.; Chanthapally, A.; Lee, H.-H.; Quah, H. S.; Lee, S. S.; Vittal, J. J. Solid-state conversion of a MOF to a metal-organo polymeric framework (MOPF) via [2 + 2] cycloaddition reaction. Chem. Commun. 2014, 50, 3665−3667. (13) Hasegawa, M. Photopolymerization of diolefin crystals. Chem. Rev. 1983, 83, 507−518. (14) Garai, M.; Santra, R.; Biradha, K. Tunable Plastic Films of a Crystalline Polymer by Single-Crystal-to-Single-Crystal Photopolymerization of a Diene: Self-Templating and Shock-Absorbing TwoDimensional Hydrogen-Bonding Layers. Angew. Chem., Int. Ed. 2013, 52, 5548−5551. (15) Mandal, R.; Garai, M.; Biradha, K. Hydrogen-bonded Two-fold Interpenetrated Diamondoid Networks for Solid-State [2 + 2] Polymerizations of Criss-crossed Olefins: Molecular Connections vs Supramolecular Connections. Cryst. Growth Des. 2017, 17, 5061−5064. (16) Garai, M.; Biradha, K. Exploration and exploitation of homologous series of bis(acrylamido)alkanes containing pyridyl and phenyl groups: [beta]-sheet versus two-dimensional layers in solid-state photochemical [2 + 2] reactions. IUCrJ 2015, 2, 523−533. (17) Jean, J. Dimethylformamide: purification, tests for purity and physical properties. Pure Appl. Chem. 1977, 49, 885−892. (18) Wang, X.-Y.; Gan, L.; Zhang, S.-W.; Gao, S. Perovskite-like Metal Formates with Weak Ferromagnetism and as Precursors to Amorphous Materials. Inorg. Chem. 2004, 43, 4615−4625. (19) Jain, P.; Dalal, N. S.; Toby, B. H.; Kroto, H. W.; Cheetham, A. K. Order−Disorder Antiferroelectric Phase Transition in a Hybrid Inorganic−Organic Framework with the Perovskite Architecture. J. Am. Chem. Soc. 2008, 130, 10450−10451. (20) Jain, P.; Ramachandran, V.; Clark, R. J.; Zhou, H. D.; Toby, B. H.; Dalal, N. S.; Kroto, H. W.; Cheetham, A. K. Multiferroic Behavior Associated with an Order−Disorder Hydrogen Bonding Transition in Metal−Organic Frameworks (MOFs) with the Perovskite ABX3 Architecture. J. Am. Chem. Soc. 2009, 131, 13625−13627. (21) Weng, D.-F.; Wang, Z.-M.; Gao, S. Framework-structured weak ferromagnets. Chem. Soc. Rev. 2011, 40, 3157−3181. (22) Xu, G.-C.; Ma, X.-M.; Zhang, L.; Wang, Z.-M.; Gao, S. Disorder− Order Ferroelectric Transition in the Metal Formate Framework of [NH4][Zn(HCOO)3]. J. Am. Chem. Soc. 2010, 132, 9588−9590. (23) Wang, X.-Y.; Wang, Z.-M.; Gao, S. Constructing magnetic molecular solids by employing three-atom ligands as bridges. Chem. Commun. 2008, 281−294. (24) Schmidt, G. M. J. Photodimerization in the solid state. Pure Appl. Chem. 1971, 27, 647. (25) Alexandrov, E. V.; Blatov, V. A.; Kochetkov, A. V.; Proserpio, D. M. Underlying nets in three-periodic coordination polymers: topology,

taxonomy and prediction from a computer-aided analysis of the Cambridge Structural Database. CrystEngComm 2011, 13, 3947−3958. (26) Blatov, V. A. Nanocluster analysis of intermetallic structures with the program package TOPOS. Struct. Chem. 2012, 23, 955−963. (27) Blatov, V. A.; Shevchenko, A. P.; Proserpio, D. M. Applied Topological Analysis of Crystal Structures with the Program Package ToposPro. Cryst. Growth Des. 2014, 14, 3576−3586. (28) Li, F. F.; Zhang, L.; Gong, L. L.; Yan, C. S.; Gao, H. Y.; Luo, F. Reversible photo/thermoswitchable dual-color fluorescence through single-crystal-to-single-crystal transformation. Dalton Trans. 2017, 46, 338−341. (29) Ranford, J. D.; Vittal, J. J.; Wu, D. Topochemical Conversion of a Hydrogen-Bonded Three-Dimensional Network into a Covalently Bonded Framework. Angew. Chem., Int. Ed. 1998, 37, 1114−1116. (30) Ranford, J. D.; Vittal, J. J.; Wu, D.; Yang, X. Thermal Conversion of a Helical Coil into a Three-Dimensional Chiral Framework. Angew. Chem., Int. Ed. 1999, 38, 3498−3501. (31) Yang, X.; Wu, D.; Ranford, J. D.; Vittal, J. J. Influence of the CO···π Interaction on the Thermal Dehydration Behavior of [Cu2(sgly)2(H2O)]·1H2O. Cryst. Growth Des. 2005, 5, 41−43. (32) Desiraju, G. R. Crystal Engineering: From Molecule to Crystal. J. Am. Chem. Soc. 2013, 135, 9952−9967. (33) Cooper, A. I. Molecular Organic Crystals: From Barely Porous to Really Porous. Angew. Chem., Int. Ed. 2012, 51, 7892−7894.

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DOI: 10.1021/acs.cgd.9b00018 Cryst. Growth Des. XXXX, XXX, XXX−XXX