We report the results of an investigation on the absorption spectra, phosphorescence spectra, phosphorescence lifetimes, and magnetic properties of [Ru(bhq)(CO)2Cl(L)], where bhq- is the C-deprotonated forms of benzo[h]quinoline (bhqH) and L is either PEt3, p-toluidine, or piperidine. The lowest singlet states of the Ru(II) complexes are metal-to-ligand charge-transfer 1dπ* states. Vibrational structures of the phosphorescence spectra observed in the crystalline states at 4.2 K are similar to the structures of the phosphorescence spectra and the magnitude of the free bhqH ligand. Zero-field splittings indicate that the lowest triplet states of all the Ru(II) complexes are mainly characterized as ligand-localized 3ππ* states. However, the phosphorescence lifetimes are significantly shorter for Ru(II) complexes as compared with free bhqH. This result suggests that the lowest triplet state of the Ru(II) complex includes 3dπ* character due to configurational mixing with the bhq-localized 3ππ* state. By inters...