Spectral information on [Pt-II(CN)(2)Rh-I((t)BuNC)(2)(mu-dppm)(2)] [PF6], Pt-2(II)(CN)(4)(mu-dppm)(2), [(AuPtII)-Pt-I(CN)(2)(mu-dppm)(2)][PF6], [(AuRhI)-Rh-I((t)BuNC)(2)(mu-dppm)(2)][PF6](2), and [(AuIrCl)-Ir-I-Cl-I(CO)(mu-dppm)(2)][PF6] [dppm = bis(diphenylphosphino)methane] is reported. Absorption and excitation spectra at room temperature, relative band polarizations at 77 K, temperature-dependent decay times (77-4 K), and changes in phosphorescence decay rates at 4 K as a function of an applied magnetic field are interpreted in terms of an isolated nd(z2) --> n’p(z) promotion leading to a singlet (fluorescing) state and triplet (phosphorescing) manifold, the latter split into two levels (10-90 cm(-1)) via spin-orbit coupling. The lower level is forbidden, the upper is quasi-degenerate and (x,y) allowed. These data, complemented by those from other analogous complexes, are related to an electronic model that allows assignments of the symmetries of the singlet state and the triplet sublevels in D-4h for homonuclear species with four identical bridging ligands, D-2h for homonuclear bi-bridged species with symmetrical nonbridging ligands, and C-2v for heteronuclear mu-dppm bi-bridged complexes of diverse symmetries. The HOMO of the excited configuration is identified with a unique metal in the heteronuclear species. A correlation exists between the magnitudes of the triplet sublevel splittings and the dependence of the rate of decay of the lowest spin level of the manifold on magnetic field strength.