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

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 {[Cd-2(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 6(3)-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.

Automated summary

Two new photochromic coordination polymers have been synthesized through the regulation of metal-ligand ratios.