UV and X-ray dual photochromic properties of three CPs based on a new viologen ligand

Abstract

A new viologen ligand 1-(1-cyclohexylmethane)-4,4′-bipyridinium bromide (CMbpyBr) in the presence of benzenecarboxylates and metal ions affords three coordination polymers [Zn(CMbpy)(HBTC)Br]n (1), [Cd(CMbpy)(m-BTC)(H2O)]n (2) and {[Cd(CMbpy)(m-BDC)(H2O)2][Cd(m-BDC)(m-HBDC)(H2O)]}n (3) (H3BTC = 1,3,5-benzenetricarboxylic acid, m-H3BTC = 1,2,4-benzenetricarboxylic acid, m-H2BDC = 1,3-benzenedicarboxylic acid). Compounds 1 and 3 both have 1D structures, while compound 2 is 3D structure. More importantly, three compounds exhibit excellent photochromic behaviors in response to UV and X-ray dual light due to the formation of viologen radicals. However, the decolorization of the photochromic products for the three compounds is very different. The reason for their different photochromic behaviors has been explored.