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

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 Zn-II 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. Crystalline materials that undergo large structural changes in response to external stimuli remain rare. Here the authors report a Zinc(II) complex that undergoes a two-step reversible single-crystal-to-single-crystal transformation via thermal removal of ethylene glycol chelating ligands; this results in large volume changes.

Automated summary

This study reports a Zn-II complex that undergoes a giant single-crystal-to-single-crystal transformation induced by thermal elimination of ethylene glycol chelating ligands. The enormous structural change is characterized by single-crystal X-ray diffraction analyses, showcasing a unique material with both periodic crystal lattice and gel-like super-ductility. This research also suggests a potential solid-state reaction method for preparing chiral compounds by eliminating chelating ligands.