Three 1D coordination polymers based on bipyridinium carboxylate ligands: Photochromism

Abstract

Abstract With the self-assembly reaction of TM(NO3)2 (TM\u202f=\u202fCd, Cu) and two bipyridinium carboxylate ligands, three one-dimensional (1D) double chain-like coordination polymers (CPs) {[Cd0.5(CEbpy) (H2O)]NO3·H2O}n (1), {[Cu0.5(CEbpy) (H2O)]NO3·H2O}n (2), {[Cu(BCEbpy) (H2O)2]NO3·Br·4H2O}n (3), (CEbpy\u202f=\u202f1-carboxyethyl-4,4′-bipyridine, BCEbpy\u202f=\u202f1,1′-bis(carboxyethyl)-4,4′-bipyridine) have been synthesized and structurally characterized. Compounds 1 and 2 exhibit electron-transfer (ET) photochromism due to the generation of viologen radicals, while the photochromic behavior of compound 3 is a redox process, which is rarely reported in bipyridinium complexes. Furthermore, the photoinduced radicals in 1–3 have long-lived lifetime after irradiation.