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

Photochromic dithienylethene (DTE) derivatives, DTE-MCpL2 {M = Fe, Ru: Cp = eta(5)-cyclopentadienyl; L-2 = (CO)(2), (CO)PPh3, dppe (dppe = Ph2PCH2CH2PPh2)}, with a directly sigma-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 1(Ru) and 2(Ru) 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 3(Fe) gives the corresponding radical cationic species with a visible absorption. (C) 2011 Elsevier Ltd. All rights reserved.