Two novel photochromic compounds based on a thiazolothiazole extended viologen derivative

In the last few years, more and more attention has been paid to the application of chromic materials, and photo-active viologen groups have been broadly assembled into functional materials with photochromism. However, the limited research conducted to date indicates that the extended viologen photochromic compounds are rarely reported. Herein, a rigid thiazolothiazole extended viologen moiety H2TTVPCl2 (2,5-bis (pyridinium-4-yl) thiazolo [5,4-d] thiazole propionate dichloride) is selected to construct two novel photochromic compounds, namely {[Zn(TTVP)0.5(BTEC)0.5(H2O)2]·2H2O}n (1) and [(H2TTVP)(H4BTEC)0.5]·(H2O)·2Cl (2). 1 has a two-dimensional (2D) layered structure, while 2 has a zero-dimensional (0D) structure. As expected, 1 and 2 display photochromic behavior of electron transfer. Furthermore, the photo-controlled luminescence and potential application as inkless and erasable printing media are also investigated.