The syntheses, absorption spectra, emission spectra, electrochemical behavior, and excited-state lifetimes of a series of phenylethynyl-substituted copper(I) complexes are reported. These results are compared to those of the parent complex, [Cu(dpp)(2)](+) (dpp = 2,9-diphenyl-1,10-phenanthroline), to explore the effects of extended electronic delocalization on the photophysics of luminescent copper(I) bis(phenanthroline) complexes. Visible excitation of these complexes leads to emission from metal-to-ligand charge-transfer excited states. Room-temperature excited state lifetimes range from 91 to 243 ns in dichloromethane. The effects of the phenylethynyl group(s) on the photophysical and electrochemical properties vary with the position of substitution. The most profound effects an observed when the parent complex is substituted at the 4- and 7-positions of the phenanthroline ligand. The positional effects are discussed with respect to the nature of the lowest unoccupied molecular orbitals.