Converging Energy Transfer in Polynuclear Ru(II) Multiterpyridine Complexes: Significant Enhancement of Luminescent Properties.

Ruthenium-based complexes are widely used as photocatalysts, as photosensitizers, or as building blocks for supramolecular assemblies. In the field of solar energy conversion, building light harvesting antenna is of prime interest. Nevertheless, collecting light is mandatory but not sufficient; once collected and transferred, the exciton has to be long-lived enough to be transferred to a catalytic site. If Ru(II) terpyridine complexes are prime building blocks for structural reasons, the short lifetime of their excited state prevents their use as a harvesting center in light antennae. In this paper, we present new polynuclear assemblies, based on Ru(II)-terpyridine units where delocalization of the excited state is combined with an antenna effect. As a consequence, complexes C1-C3 display long-lived excited states compared to [Ru(tpy)], making them promising efficient antenna building blocks to be connected to a final acceptor or a catalytic center.