Photoswitched and functionalized oligothiophenes: Synthesis and photochemical and electrochemical properties

The extended dithienylethene compounds 1-3 have been synthesized. They undergo photochromic and electrochemical changes by photoinduced interconversion between open and closed forms of type A and B. In addition, both forms of the N-methylated derivatives 1b and 2b have absorption bands in which excitation results in very large differences in fluorescence between the two forms with very little effect on the opening/closing state, a feature of interest for optical memory data systems. The compounds 2 and 3 contain six and eight conjugated thiophene units in the closed forms, respectively, and thus represent oligothiophenes endowed with a photoactivated switch; they are of special interest in this respect in view of the potential use of switched oligothiophenes in molecular electronic devices.