Extended viologen compounds with photochromism, photoresponsive luminescence and ultrahigh quenching efficiency

Abstract

A new type of extended viologen, N,N′-2,5-bis(3-pyridinium)thiazolo[5,4-d]thiazole dipropionate, (m-H₂TTzPA)(HSO₃)₂ (1), was synthesized, and two new coordination polymers, {[Cd(m-TTzPA)Br₂]·H₂O}_n (2) and {[Zn(m-TTzPA)Br₂]·H₂O}_n (3), were prepared based on the m-TTzPA ligand. Compounds 1–3 exhibit photochromic behaviors, which were proved using single-crystal X-ray diffraction, UV-vis spectroscopy and EPR characterizations. Furthermore, all the compounds have obvious fluorescence quenching behaviors upon irradiation using a xenon lamp, where compound 1 exhibits a significant quenching efficiency of 95.84%.