AbstractThe optical and redox properties of a methyl pyridinium appended 1,2‐dithienylethene photochromic derivative have been thoroughly investigated. A complex multi‐step photo/redox mechanism is proposed for the closed isomer on the ground of spectro‐electrochemical and theoretical data. The generated compounds are not stable over the time because of chemical reactions associated to the redox processes and a new dithienylethene derivative incorporating a seven‐membered ring has been isolated and characterized.