Metal-dependent photosensitivity of three isostructural 1D CPs based on the 1,1′-bis(3-carboxylatobenzyl)-4,4′-bipyridinium moiety

Abstract

To study the effect of metal ions on the photochromic behaviors of CPs, three new isostructural coordination polymers (CPs) based on a neutral viologen moiety, 1,1′-bis(3-carboxylatobenzyl)-4,4′-bipyridinium (bcbpy), have been obtained by choosing 1,2,4,5-benzenetetracarboxylic acid (H₄BTEC) to coordinate with different metal ions, {[M(H₂O)₆][M(BTEC)(H₂O)₄]·(bcbpy)·4H₂O}_n (M = Co (1), Ni (2), Zn (3)), all of which exhibit metal-dependent photochromism and adjustable photosensitivity. Compounds 1 and 2 are only sensitive to UV light, while compound 3 is sensitive to sunlight, UV light and X-ray (Mo). The comparison of the photochromic behaviors of the three CPs indicates that the metal ions play an important role in regulating their photochromic properties.