Five novel supramolecular assemblies constructed from the thiazolothiazole extended viologen moiety

Abstract

Lately, an increasing number of research groups have been inspired by the construction and optical capabilities of 2,5-bis (4-pyridine)-thiazolo [5,4-d] thiazole. Herein, five novel supramolecular assemblies based on the extended viologen moiety (TTVP, 2,5-bis (pyridinium-4-yl) thiazolo [5,4-d] thiazole propionate) and different benzenecarboxylic acids (1,4-H₂NDC = 1,4-naphthalenedicarboxylic acid; H₂TPDC = thiophene-2,5-dicarboxylic acid; H₄BTEC = 1,2,4,5-benzenetricarboxylic acid; m-H₃BTC = 1,2,4-benzenetricarboxylic acid; p-H₂BDC = 1,4-benzenedicarboxylic acid) are composited by a self-assembly reaction, namely (H₂TTVP)_0.5(1,4-HNDC)·2H₂O (1), (TTVP)(H₂TPDC)·6H₂O (2), (H₂TTVP)_0.5(H₂BTEC)_0.5·H₂O·DMF (3), (H₂TTVP)_0.5(m-H₂BTC) (4), (TTVP)_0.5(p-H₂BDC)_0.5·H₂O (5). The electron-deficient extended viologen moiety and the electron-donating benzenecarboxylate moieties are hydrogen-bonded to build the D–A system. Although five supramolecular assemblies comprise the same TTVP moiety, only 2–5 exhibit reversible photochromic behavior on account of the formation of extended viologen radicals via electron transfer (ET). Meanwhile, the photo-controlled fluorescence and the inkless and erasable printing capabilities are discussed.