Synthesis and photochromic properties of thiophenophan-1-enes containing a polyether bridge

[2.n]Thiophenophan-1-ene derivatives containing a polyether bridge have been synthesized by the coupling reaction of bis(iodomethyl)dithienylethene with polyethylene glycols under high dilution conditions. All prepared [2.n]thiophenophan-1-enes were photochromic, as photocyclization of the open forms took place by UV irradiation to give a yellow solution of the closed form and their ring opening reactions occurred upon visible irradiation. There were significant differences in the quantum yields for the photocyclization reactions and the photo ring-opening reactions due to the difference in their structures since their electric properties are similar. The kinetic parameters of the thermal ring opening reaction of the closed forms of thiophenophan-1-enes were estimated and they were also dependent on their bridges.