Photochromic properties of tetrakis(2-methylthien-3-yl)ethene and its tetrakis(methylthio) derivative

The photoreaction of tetrakis(2-methylthien-3-yl)ethene (1a) and its tetrakis(methylthio) derivative 1b was investigated in the context of a potentially new chromic system responsive to both photoexcitation and electron transfer. UV irradiation of 1 at low conversion leads to production of its cyclic isomer 2 while 2 returns to 1 upon vis irradiation, representative of facile photochromic behavior. In contrast, UV irradiation at high conversion transforms 1b to rearranged product 3b via the intermediacy of 2b.