Photochromism, photo-modulated luminescence and vapochromism in a Zn-MOF with the novel thiazolothiazole extended viologen ligand

Thiazolo[5,4- d ]thiazole extended viologen (2,5-bis(pyridinium-4-yl)thiazolo[5,4- d ]thiazole, Py 2 TTz) has recently been identified as a very efficient fluorophore, in contrast with the relatively weak fluorescence of the traditional viologens. Herein, we developed a novel thiazolothiazole extended viologen derivative (denoted as 3-L ) by incorporating carboxybenzyl into Py 2 TTz. On this basis, a Zn-based metal-organic framework (Zn-MOF) {[Zn(3-L) 0.5 (TPDC)(H 2 O)]·H 2 O} n (denoted as Zn-L ) has been synthesized derived from 3-L under solvothermal conditions. Both 3-L and Zn-L show excellent photochromism and ammonia vapochromism, probably due to the formation of viologen radicals induced by electron transfer under UV and NH 3 stimuli. Besides, both compounds exhibit reversible modulation of fluorescence during the coloration-decoloration process. Based on photochromism, inkless erasable printing can prepare the desired erasable pattern by UV irradiation.