An important goal in inorganic photochemistry is the development of new artificial photosynthetic assemblies capable of efficiently harvesting solar energy.' In this regard, the excited state properties of cuprous diimine chromophores have received considerable attention? Detailed studies have largely established the geometric and electronic nature of the metal-to-ligand charge-transfer (MLCT) excited states in these c o m p o~n d s .~-~ The luminescent excited states are quenched by a variety of inorganic and organic compounds, but the underlying mechanism-(s) remain speculative. In this communication, we report the first direct spectroscopic observation of energy transfer from cuprous diimine excited states. Specifically, photoexcited Cu-(dpp),(PFs) (dpp is 2,9-diphenyl-l,lO-phenanthroline) and Cu-(dmp)a(P&) (dmp is 2,9-dimethyl-1,lO-phenanthroline) transfer energy to anthracene in dichloromethane solution, eqs 1 and 2. These reactions are important in photocatalysis as anthracene can function as an efficient energy relay between light absorbing donors and electron acceptor^.^ (a) Fox, M. A.; Chanon, M. Photoinduced Electron Transfer; Elsevier: Amsterdam, 1988. (b) Gratzel, M. Heterogeneous Phorochemical Electron Transfer; CRC: Boca Raton, FL, 1989. For a recent review of copper(1) diamine excited states, see: (a) Kalyanasundaram, K. Photochemisrry of Polypyridine and Porphyrin Complexes; Academic Press: London, 1992; Chapter 9. (b) McMillin, D. R.; Kirchhoff, J. R.; Goodwin, K. V. Coord. Chem. Rev. 1985.64, 83. (a) McMillin, D. R.; Buckner, M. T.; Ahn, B. T.