Different metal–ligand ratios regulated two Cd(II)-containing viologen-derived photochromic coordination polymers

Abstract

Through meticulous tuning of the metal-ligand ratios, two new coordination polymers (CPs) based on N-(3-carboxypyridin-5-yl)-4,4′-bipyridinium (cpbpy) and 2,5-thiophenedicarboxylic acid (H2L) mixed ligands, namely, {[Cd(cpbpy)(L)(H2O)2](H2O)3}n (1) and {[Cd2(cpbpy)(L)2(H2O)4](H2O)4}n (2) have been successfully synthesized. The single-crystal X-ray diffraction analysis reveal compounds 1 and 2 both crystallize in triclinic P-1 space group, while compound 1 is a 1D chain structure and compound 2 displays a 2D layered structure with 3-connected 63-hcb topology. 1 and 2 exhibit photochromism and undergo distinct color changes from light yellow to green due to the formation of radicals. This work provides a simple method via regulation of metal–ligand ratios to synthesize new photochromic CPs.