Light Energy Accumulation from Pyrene Derivative to Tris(bipyridine)ruthenium on Clay Surface

A novel type of energy donor-acceptor system on a clay surface has been prepared. The energy transfer between an energy-donating cationic pyrene derivative (An-Py²⁺) and an energy-accepting tris(bipyridine)ruthenium complex (Ru²⁺) on the clay surface was investigated using absorption, emission, and lifetime measurements. An obvious energy transfer was observed, and one Ru²⁺ molecule quenched the emission from five molecules of An-Py²⁺ with an emission quenching efficiency of 85% on the clay surface. This suggests that the light energies absorbed by five of the An-Py²⁺ molecules were accumulated in the one Ru²⁺ molecule. Near-quantitative emission quenching was observed for stoichiometric amounts of An-Py²⁺ and Ru²⁺. The apparent quenching rate constant is approximately 10¹⁷ L mol^-1 s^-1, and thus the quenching rate constant is 10⁷-10⁸ times higher than the diffusion rate constant in a homogeneous solution.