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Publication costs assisted by the Petroleum Research FundLuminescence quenching of Ru(b~y),(cN)~ and R~( p h e n )~( C N )~ (bpy = 2,2'-bipyridine and phen = 1,lOphenanthroline) by 19 transition metal complexes is reported. The neutral cyano complexes have properties which permit them to supplement the widely used [Ru(bpy)3I2+ and [R~(phen)~]'+ sensitizers. In addition to their intense, long-lived fluid solution emissions, the cyano complexes are free of ion-pairing problems and the large charge dependence of quenching rates with the tris complexes. The excited state energies of the cyano species can also be tuned significantly by solvent variation. Quenching is predominantly by diffusion. For Co2+, Ni2+, and Cu2+, however, associational quenching by formation of a cyanide bridged species is important. Decay times, excited state energies, Stern-Volmer constants, bimolecular quenching constants, and association constants are reported. Quenching appears to be by energy and electron transfer.

We wish to report on the quenching of the chargetransfer (CT) luminescence of Ru(phen)2(CN)2 (phen = 1,10-phenanthroline) by Cu2+ (H20, ~22°). This system demonstrates what we believe to be the first unequivocal evidence for both static and dynamic quenching of a metal complex exhibiting CT lumines-(12) A. A. Schilt, Amer. Chem. Soc., 82, 3000 (1960).

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