Oxidative quenching within photosensitizer-acceptor dyads based on bis(bidentate) phosphine-connected osmium(II) bipyridyl light absorbers and reactive metal sites

► Two novel heterodimetallic complexes representing photosensitizer-acceptor dyads have been synthesized. ► Their photophysical properties are compared with a corresponding new monometallic species, indicating oxidative quenching. ► The related intramolecular electron transfer within these dyads occurs despite the presence of saturated cyclobutane rings. ► The observed electron transfer is necessary in order to achieve photochemical water splitting.