Color change of redox-active organometallic dithienylethene complexes by photochemical and redox processes

Photochromic dithienylethene (DTE) derivatives, DTE–MCpL2 {M = Fe, Ru; Cp = η5-cyclopentadienyl; L2 = (CO)2, (CO)PPh3, dppe (dppe = Ph2PCH2CH2PPh2)}, with a directly σ-bonded, redox-active organometallic attachment have been prepared and their response to photo- and electrochemical stimuli has been investigated. It turns out that the color of the organometallic derivatives can be controlled not only by photochromic processes but also by one-electron redox processes. The Ru complexes 1Ru and 2Ru exhibit reversible photochromism in a manner similar to organic DTE derivatives, with ring closing and ring opening triggered by UV and visible-light irradiation, respectively. Their photochromic behavior is critically dependent on both of the central metal and ligands. One-electron oxidation of the Fe complex 3Fe gives the corresponding radical cationic species with a visible absorption.

► We show the preparation of dithienylethene derivatives with a single metal unit.
► The photochromic performance depends on the structure of metal fragment.
► Some complexes exhibit electrochromism based on redox processes of metal fragment.
► Combination of photochemical and redox processes produces three colors.