Solvent-control of photoinduced electron transfer via hydrogen bonding in a molecular triad made of a dinuclear chromophore subunit

We have prepared a molecular triad containing a triphenylamine as the electron donor D subunit, an anthraquinone derivative as the acceptor A group, and a dinuclear Ru(II) species (P-P) based on terpyridine-like ligands as light-harvesting subunit, so that a linearly arranged D-(P-P)-A molecular triad is obtained. In acetonitrile solution containing 1% (in volume) of methanol, photoinduced oxidative electron transfer occurs in 380 ps, with formation of the D-(P-P)+-A− charge-separated (CS) state. However, although formation of the fully-developed D+-(P-P)-A− state is favored by about 0.23 eV, such species is not formed since charge recombination within D-(P-P)+-A− appears to be faster.