Construction of three high-dimensional supramolecular networks from temperature-driven conformational isomers

Abstract

Under different temperatures, the reaction mixture of the multidentate organic ligand usy-L⁴ and Zn(NO₃)₂ + NaN₃ crystallized to give three conformational isomers, namely Zn(usy-L⁴)(η¹-N₃)₂ (α-1, β-2 and γ-3) (usy-L⁴ = N,N-dimethyl-2-(pyridin-2-ylmethylimino)ethanamine). Single-crystal X-ray diffraction analyses reveal that the conformational isomerism of three compounds 1–3 stems from the different orientations of two azide groups with η¹-terminal nitrogen atom coordinating to central zinc ion in reference to the basal chelating plane of ligand usy-L⁴, and further resulting in different supramolecular networks with two-dimensional 4⁴ rhombic-grid for α-1, a three-dimensional 3⁶·4¹⁸·5³·6 compressed-NbO framework for β-2, and a three-dimensional “dense” 4²⁴·6⁴ topology for γ-3. Meanwhile, three isomers may be also irreversibly converted from 1 to 2, to 3 through SC-to-SC transformation driven by temperature.