Photoinduced electron transfer in panchromatic zinc phthalocyanine–azobenzene dyad

A new unsymmetrical azobenzene–phthalocyanine dyad was designed and synthesized. Besides impressive panchromatic absorptivity both in solution and adsorbed on solid-state anatase TiO2 substrate, efficient photoinduced electron transfer from azobenzene π* orbital to phthalocyanine S1 orbital was elucidated for the first time by fluorescence spectroscopy and cyclic voltammetry. Such an interesting phenomenon as a dominant intra-molecular electronic communication process is attributed to the inefficiency of local deactivation pathway through orbital overlap forbidden π* → n transition. This may imply efficient collection of panchromatic photoelectrons by delicate molecular design and is expected to boost fields related to solar energy utilization.