Three functional Cd(II) coordination polymers constructed by the thiazolothiazole extended viologen ligand

Expanding the pi-conjugated structure of traditional viologens by incorporating thiazole units to the bipyridine skeleton has attracted more and more attention. In this work, a rigid thiazolothiazole extended viologen ligand (TTVP, 2,5-bis (pyridinium-4-yl) thiazolo [5,4-d] thiazole propionate) has been used to constitute three new functional Cd(II) coordination polymers (CPs), {[Cd(TTVP)0.5(HBTC)(H2O)2]center dot 2H2O}n (1), {[Cd(TTVP)0.5(pBDC)0.5(p-HBDC)(H2O)]center dot 3H2O}n (2), {[Cd(TTVP)0.5(m-BDC)]}n (3) by introducing different benzenecarboxylic acids as auxiliary ligands (H3BTC = 1,3,5-benzenetricarboxylic acid; p-H2BDC = 1,4-benzenedicarboxylic acid; m-H2BDC = 1,3-benzenedicarboxylic acid). The crystal structures and photochromic capabilities of 1-3 are studied. Both compounds 1 and 2 own one-dimensional (1D) chain-like structure, while compound 3 owns twodimensional (2D) layered structure. As expected, compounds 1-3 show reversible photochromism due to electron-transfer (ET). In addition, the photo-controlled luminescent properties and the potential application as inkless and erasable printing media are also explored.