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The effects of hydrostatic pressure on the metal to ligand charge-transfer (MLCT) excited-state emission lifetimes for the copper® complexes Cu(dmp)2+ and Cu(dpp)2+ (dmp = 2,9-dimethyl-1,10-phenanthroline, dpp = 2,9-diphenyl-1,10-phenanthroline) have been determined in CH2C12 solution. In the absence of added quenchers, volumes of activation * for the nonradiative decay pathway have been determined to be -3.4 and -1.6 cm3/mol, respectively. For the previously reported quenching of [Cu(dmp)2+] * by the cosolvents CH3CN and CH3OH, * values of-6.2 and -5.4 cm3 5/mol were measured. These data are consistent with the proposal that an associative mechanism plays a role in the nonradiative deactivation of the MLCT excited state of the less sterically crowded (dmp)2 complex.

The time-resolved emission spectra of the tetranuclear clusters Cu414(py-X)4 (X = H, 3-CI, 4-Ph, 4-PhCH2, or 4-But) at 296 K in toluene each display separate, uncoupled emissions from two states, a short-lived (0.13-0.56 p) metal-to-ligand charge transfer in the range 473-537 nm and a much more intense and longer lived (10-13 p) metal cluster centred (MCC) emission in the range 678-698 nm; for X = 4-Ph the MCC emission exhibits an unusual, temperature dependent rise-time.

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