Spontaneous resolution of a coordination polymer containing stereogenic five-coordinate Zn(ii) centers and achiral ligands with axially chiral conformation

Abstract

A pair of chiral coordination polymers, [Zn(HPyIDC)]_n (1a and 1b, H₃PyIDC = 2-(pyridin-3-yl)-1H-imidazole-4,5-dicarboxylate), were assembled from an achiral precursor, H₃PyIDC and Zn(II) ions via spontaneous resolution under solvothermal conditions. Crystal structure analysis showed that they are chiral three-dimensional (3D) coordination polymers based on the interconnection of six types of one-dimensional (1D) helical chains. They exhibit an intrinsic chiral (10,3)-a network. The chirality comes from both the stereogenic five-coordinate Zn(II) ions and the axially chiral ligands. Solid-state circular dichroism (CD) spectra measurements confirmed the occurrence of spontaneous resolution of [Zn(HPyIDC)]_n and demonstrated that the resulting crystal of [Zn(HPyIDC)]_n is a racemic mixture. Compound 1 showed strong fluorescence emission at room temperature.