Giant single-crystal-to-single-crystal transformations associated with chiral interconversion induced by elimination of chelating ligands

Abstract

Numerous single crystals that exhibit single-crystal-to-single-crystal (SCSC) transformations have been reported, and some of them show great promise for application to advanced adsorption materials, magnetic switches, and smart actuators. However, the development of single crystals with super-adaptive crystal lattices capable of huge and reversible structural change remains a great challenge. In this study, we report a ZnII complex that undergoes giant SCSC transformation induced by a two-step thermal elimination of ethylene glycol chelating ligands. Although the structural change is exceptionally large (50% volume shrinkage and 36% weight loss), the single-crystal nature of the complex persists because of the multiple strong hydrogen bonds between the constituent molecules. This allows the reversible zero-dimensional to one-dimension and further to three-dimensional structural changes to be fully characterized by single-crystal X-ray diffraction analyses. The elimination of chelating ligands induces a chiral interconversion in the molecules that manifests as a centric-chiral-polar symmetric variation of the single crystal. The study not only presents a unique material, featuring both a periodic crystal lattice and gel-like super-ductility, but also reveals a possible solid-state reaction method for preparing chiral compounds via the elimination of chelating ligands.

Giant thermal expansion associated with a macroscopic polarization change in a single crystal of a Zn(ii) complex

“…[23][24][25][26] Recently, dozens of flexible single crystals with giant thermal expansion, thermal-induced electron transfer, or mechanical deformation have been developed. 23,[26][27][28][29][30][31] If the thermally induced significant structural transformation is involved in the macroscopic polarization change of single crystals, a large pyroelectric response could be expected.…”

Heat triggered molecular restructuring results in triple gel–gel–gel transformations in a Li+-integrated metallogel

“…36 In addition to this, morphological transitions in supramolecular systems are mostly limited up to one step transformations i.e. , fibre–fibre, 37 vesicle–fibre, 38 fibre–crystal, 39 crystal–fibre, 40 crystal–crystal, 41 etc. , but, to the best of our knowledge, heat-assisted distinct two-step fibre–rod–fibre morphological evolution accompanied with macroscopic gel phase evolution is still rare in the literature, if not sporadic.…”

“…[32][33][34][35] But not much attention has been paid to in situ gelator alteration by chemical modification to obtain a metallogel with different colours. 36 In addition to this, morphological transitions in supramolecular systems are mostly limited up to one step transformations i.e., fibre-fibre, 37 vesicle-fibre, 38 fibrecrystal, 39 crystal-fibre, 40 crystal-crystal, 41 etc., but, to the best of our knowledge, heat-assisted distinct two-step fibre-rodfibre morphological evolution accompanied with macroscopic gel phase evolution is still rare in the literature, if not sporadic. It might be due to the fact that it is challenging to tune a wide range of non-covalent interactions under the influence of only one type of energy.…”

Single Crystal to Single Crystal Transformation of CuII Complexes Induced by Dehydrating and Hydrating of Ligands with Chroma Rewritable Behaviors

“…40−42 The last one is the chemical reactions on ligands, which is mainly the addition, elimination, replacement reactions on organic ligands. 43,44 The latter two types of SCSC transitions are more interesting due to changes in both composition and chemical bonding, which often involve changes in the structure and property. However, crystal transformations with changes of both covalent bonds of ligands and coordination bonds are relatively rare.…”

“…The first and most common type is the removing or obtaining lattice solvent molecules in solids, which only involve the change of weak intermolecular interactions, − i.e., hydrogen bonds, etc., in the crystal. The second type is the reorganization of chemical bonds between existing compositions, in which there is no gain or loss of atoms in the crystal but only the bond-type isomerism or the formation or breakage of the bonds (i.e., coordination bonds of metal ions, or isomerism of the ligands). − The third type is the addition, elimination, and substitution reactions of ligands or metal ions, which involve the exchange of species and the breaking and generating of coordination bonds. − The last one is the chemical reactions on ligands, which is mainly the addition, elimination, replacement reactions on organic ligands. , The latter two types of SCSC transitions are more interesting due to changes in both composition and chemical bonding, which often involve changes in the structure and property. However, crystal transformations with changes of both covalent bonds of ligands and coordination bonds are relatively rare …”