Supramolecular bis(rutheniumphthalocyanine)-perylenediimide ensembles:: Simple complexation as a powerful tool toward long-lived radical ion pair states

A novel supramolecular electron donor-acceptor hybrid (1) has been designed through axial coordination of a perylenebisimide moiety [BPyPDI], bearing two 4-pyridyl substituents at the imido positions, to the ruthenium(II) metal centers of two phthalocyanines [Ru(CO)Pc]. This modular protocol enables access to electron donor-acceptor hybrids with potentially great design flexibility. The new array ( 1) has been characterized by standard spectroscopic methods, and its photophysical behavior has been established by using ultrafast and fast time-resolved techniques. Photoexcitation of either chromophore leads to a product that is essentially identical for both pathways, that is, evolving from the [Ru(CO) Pc] or [BPyPDI] singlet excited state. Features of the photoproduct are new transient maxima at 530 and 725 nm, plus transient minima at 580 nm and 650 nm. Based on the radiolytically generated [BPyPDI.-](i.e., one-electron reduction of [BPyPDI]) and [Ru(CO)Pc-.+] (i.e., one-electron oxidation of [Ru(CO)Pc]) features, which in the 300 and 900 nm range remarkably resemble those noted for photoexcited 1, we attribute the photolytically generated species to the composite spectrum of the [Ru(CO)Pc.+-BPyPDI.--RuCOPc] radical ion pair state. Its lifetime, which is on the order of 115 +/- 5 ns, reveals a significant stabilization and confirms that the strongly exothermic charge recombination dynamics are placed deeply in the inverted region of the Marcus parabola.