A Multifunctional Coordination Polymer Constructed by Viologen Derivatives: Photochromism, Chemochromism, and MnO Sensing.

A multifunctional Cd-based coordination polymer based on a viologen derivative and a secondary carboxylic ligand, namely, {[Cd(bcbp)(pta) (HO)]·2HO} (, HbcbpCl = 1,1'-bis(4-carboxyphenyl)-(4,4'-bipyridinium) dichloride, Hpta = -phthalic acid), has been solvothermally synthesized and structurally characterized. Compound is a 3D framework built on {Cd(pta) (HO)} net with square channels which intalls bcbp ligands at the diagonal position of the two adjacent square channels. Notably, compound exhibits a reversible photochromic transformation between yellowish gray and dark green under xenon light irradiation, which should be attributed to the formation of free viologen radicals. Furthermore, compound also displays a chemochromic phenomenon from yellowish gray to dark green after exposure to ammonia and hydrazine, which could be ascribed to the generation of viologen radicals and charge-transfer complexes triggered by nucleophilic attack of electron-rich ammonia and hydrazine molecules to the electron-deficient viologen moiety in the bcbp ligand. Moreover, compound is capable of quickly and selectively detecting MnO with a high quenching coefficient and a low limit of detection via a luminescent quenching process caused by the competitive absorption of excitation energy.