Regulation of charge delocalization in a heteronuclear Fe2Ru system by a stepwise photochromic process

Abstract

Heteronuclear complexes FeCp2-DTE-C≡C-Ru(dppe) 2Cl (1o ; dppe = 1,2-bis(diphenylphosphino)ethane, Cp= cyclopentadienyl, DTE = dithienylethene) and FeCp2-DTE-C≡C-Ru(dppe)2-C≡C-DTE-FeCp2 (2oo), with redox-active ferrocenyl and ruthenium centers separated by a photochromic DTE moiety, were prepared to achieve photoswitchable charge delocalization and Fe•••Ru electronic communication. Upon UV-light irradiation of 2oo, the Fe•••Ru heterometallic electronic interaction is increasingly facilitated with stepwise photocyclization, 2oo→2co→2cc ; this is ascribed to the gradual increase in π-conjugated systems. The near-infrared absorptions in mixed-valence species [2oo]+ /[2co]+ /[2cc]+ are gradually intensified following the conversion of [2oo]+ ![2co]+ ![2cc] + , which demonstrates that the extent of charge delocalization shows progressive enhancement with stepwise photocyclization. As revealed by electrochemical, spectroscopic, and theoretical studies, complex 2 exhibits nine switchable states through stepwise photochromic and reversible redox processes.