Structure-Dependent Photophysical Properties of Singlet and Triplet Metal-to-Ligand Charge Transfer States in Copper(I) Bis(diimine) Compounds

The photophysical properties of singlet and triplet metal-to-ligand charge transfer (MLCT) states of [Cu(I)(diimine)2]+, where diimine is 2,9-dimethyl -1,10-phenanthroline (dmphen), 2,9-dibutyl-1,10-phenanthroline (dbphen), or 6,6ʹ-dimethyl-2,2ʹ-bipyridine (dmbpy), were studied. On 400 nm laser excitation of [Cu(dmphen)2]+ in CH2Cl2 solution, prompt 1MLCT fluorescence with a quantum yield of (2.8 (plus-minus) 0.8) ×10^-5 was observed using a picosecond time-correlated single photon counting technique.