A triad based on an iridium(III) bisterpyridine complex leading to a charge-separated state with a 120-μs lifetime at room temperature

A triad D-Ir-A, where Ir is an Ir^III bisterpyridine complex connected through an amidophenyl spacer to D, a triphenylamine electron donor, and to A, a naphthalene bisimide electron acceptor, has been synthesized and electrochemically investigated. The photoinduced processes in the triad, which is more than 4-nm long, have been characterized by steady-state and time-resolved optical spectroscopy by comparison with the model dyads D-Ir, Ir-A, and the reference monomers D, Ir, and A. A sequential electron transfer occurs upon excitation of the D and Ir units, leading to the charge-separated state D⁺-Ir-A in 100% yield and subsequently to D⁺-Ir- A^- in about 10% yield. The final charge-separated state has a lifetime at room temperature of 120 μs in air-free acetonitrile and of 100 μs in air-equilibrated solvent. Excitation of the A units does not yield intramolecular reactivity, but the resulting triplet-excited state localized on the acceptor, D-Ir-³A, displays intermolecular reactivity.