Photophysical and ab Initio Studies of Mononuclear Copper(I) Complexes.

Described are the photophysical properties of the mononuclear copper(I) complexes CuL4+ (L = pyridine (py), 4-methylpyridine, 4-phenylpyridine, or acetonitrile), Cu(lut)3+ (lut = 2,6-lutidine), and Cu(lut)2+. Each of these compounds as their solid PF6- salts display a relatively long-lived (>1 μs), visible range emission at both ambient temperature and at 77 K but not in fluid solutions. Also reported are the results for ab initio calculations at the restricted Hartree−Fock self-consistent field level to probe the natures of lower energy excited states of the hypothetical species CuLn+ (L = NH3, CH3CN, or py; n = 1−4). These results point to an assignment of the lowest energy, luminactive excited states as being largely metal centered, d → s in character for each of the above complexes with the possible exception of the CuL4+ species where L is py or a substituted analogue. In the case of Cu(py)4+ the ab initio calculations indicate a metal-to-ligand charge transfer to be the lowest energy Franck−Condon s...