Tailoring Enhanced Elasticity of Crystalline Coordination Polymers

Abstract

The approach for enhancing the elasticity of crystals with suboptimal elastic performances through a rational design was presented. A hydrogen-bonding link was identified as a critical feature in the structure of the parent material, the Cd(II) coordination polymer [CdI2(I-pz)2] n (I-pz = iodopyrazine), to determine the mechanical output and was modified via cocrystallization. Small organic coformers resembling the initial organic ligand but with readily available hydrogens were selected to improve the identified link, and the extent of strengthening the critical link was in an excellent correlation with the delivered enhancement of elastic flexibility materials.

Exploring the Co-Crystallization Landscape of One-Dimensional Coordination Polymers Using a Molecular Electrostatic Potential-Driven Approach

“…Alternation of 2-D layers of 1 and A in the crystal packing of 1:A . Arrangement of 2-D layers in 1:B , 2:A , and 5:A is analogous to that in 1:A .…”

“…The low-temperature crystal structure of 1:A did not reveal any substantial difference in comparison with the previously reported room-temperature structure (Figure 3). 25 In contrast to 1:A, 1:B at a low temperature presented a new polymorphic form (Form-II; LT). While Form-I (the roomtemperature form, RT) contained all the features observed in 1:A, Form-II displayed a lower symmetry of both polymeric building units and adjusted co-former molecules, which is impacting the overall corrugation of the structure (Figure 4).…”

“…24 Furthermore, it has been shown that the incorporation of small symmetric coformers capable of strengthening a specific supramolecular link successfully enhances the elastic behavior of the parent CP crystal. 25 In this study, we opted for a larger library of both coordination compounds and co-formers to provide a more diverse data set for systematic exploration of both electrostatic and steric influences in the synthesis of targeted CP-based co-crystals (Scheme 1). 25 The selected CPs comprise all nine possible combinations of cadmium(II) halides with halopyrazines (CdX′ 2 , X′ = I, Br, and Cl; X-pz, X = I, Br, and Cl), while the co-former requirements lead us to small, symmetric, single-aromatic-ring molecules presenting "activated" hydrogen atoms for establishing specific hydrogen bonds with the parent (Scheme 1).…”

“…25 In this study, we opted for a larger library of both coordination compounds and co-formers to provide a more diverse data set for systematic exploration of both electrostatic and steric influences in the synthesis of targeted CP-based co-crystals (Scheme 1). 25 The selected CPs comprise all nine possible combinations of cadmium(II) halides with halopyrazines (CdX′ 2 , X′ = I, Br, and Cl; X-pz, X = I, Br, and Cl), while the co-former requirements lead us to small, symmetric, single-aromatic-ring molecules presenting "activated" hydrogen atoms for establishing specific hydrogen bonds with the parent (Scheme 1). The activation of co-former hydrogen atoms was achieved by equipping the co-formers with two electronwithdrawing moieties.…”

Designing Dynamic Crystals with Multiple Flexibilities through a Cocrystal Strategy for Flexible Photo-controlled Switches

“…The elastic response was further quantified by the maximum elastic strain (ε 1 = 2.2%) (Figure S10a), which is comparable to that of most reported elastic crystals. 28,29 Similarly, when external force was applied on the minor crystal face (010), the Co-MBINH crystal could be elastically bent to an arc with the maximum elastic strain (ε 2 = 1.4%) (Figures 3c,d and S10b and Video S2). Therefore, Co-MBINH crystals are 2D elastic crystals.…”