A series of cis-dicyanoosmium(II) complexes [Os(PPh3)(2)(CN)(2)((NN)-N-boolean AND)] ((NN)-N-boolean AND = Ph(2)phen (2a), bpy (2b), phen (2c), Ph(2)bpy (2d), (t)BU(2)bpy (2e)) and [Os(DMSO)(2)(CN)(2)((NN)-N-boolean AND)] (3a-3e, (NN)-N-boolean AND = Br(2)phen (3f), Clphen (3g)), were synthesized and their spectroscopic. and photophysical properties were examined, and [Os(PMe3)(2)(CN)(2)(phen)] (4) with axial PMe3 ligands was similarly prepared. The molecular structures of 2a, 2c, [2c center dot Zn(NO3)(2)](infinity), 2d, 2e, 3b, 3d, 3e, and 4 were determined by X-ray crystallographic analyses. The two CN ligands are cis to each other with mean Os-C bond distance of 2.0 angstrom. The two PR3 (R = Ph, Me) or DMSO ligands are trans to each other with P/S-Os-P/S angles of similar to 177 degrees. The UV-vis absorption spectra of 2a-2e display an intense absorption band at 268-315 nm (is an element of = similar to (1.54-4.82) x 10(4) M-1 cm(-1)) that are attributed to pi(->)pi*((NN)-N-boolean AND) and/or pi(->)pi*(PPh3) transitions. The moderately intense absorption bands with lambda(max) at 387-460 nm (is an element of = similar to (2.4-11.3) x 10(3) M-1 cm(-1)) are attributed to a (MLCT)-M-1 transition. A weak, broad absorption at 487-600 nm (is an element of= similar to 390-1900 M-1 cm(-1)) is assigned to a (MLCT)-M-3 transition. Excitation of 2a-2e in dichloromethane at 420 nm gives an emission with peak maximum at 654-703 nm and lifetime of 0.1 6-0.67,us. The emission energies, lifetimes, and quantum yields show solvatochromic responses, and Plots of v(max), tau,and Phi, respectively, versus E-T (solvent polarity parameter) show linear correlations, indicating that the emission is sensitive to the local environment. The broad structureless solid-state emission of 2a-2e at 298 (lambda(max) 622-707 nm) and 77 (lambda(max) 602-675 nm) K are assigned to (MLCT)-M-3 excited states. The 77 K MeOH/EtOH (1:4) glassy solutions of 2a-2e also exhibit (MLCT)-M-3 emissions with lambda(max) = 560-585 nm. The 1MLCT absorption and IMLCT emission of 3a-3g occur at lambda(max) = 332-390 nm and 553-644 nm, respectively. In the presence of Zn(NO3)(2), both the (MLCT)-M-1 absorption and (MLCT)-M-3 emission of 2c in acetonitrile blue-shift from 397 to 341 nm and 651 to 531 nm, respectively. The enhancement of emission intensity (I/I-o) of 2e at 531 nm reached a maximum of similar to 810 upon the addition of two equivs of Zn(NO3)(2). The crystallographic and spectroscopic evidence suggests that 2c undergoes binding of Zn2+ ions via the cyano moieties.