The six-membered platinacycle complex, Pt(tBu2bpy)(C6H4OC6H4) (6) (tBu2bpy = 4,4∩-di-tert-butyl-2,2∩-bipyridine) has been prepared from Pt(tBu2bpy)Cl2 and 2,2∩-dilithio-diphenyl ether. Platinacycle 6 and its analogs with X = CH2 (4) and NMe (5) exhibit intense solid-state photoluminescence and nearly identical crystal structures. The photophysical properties of 4每6 in the visible range are dominated by mixed metal每ligand-to-ligand charge transfer (MLL∩CT) transitions involving high-lying filled mixed metal每ligand orbitals (ML), composed primarily of platinacyclic ring-based d- and 羽-orbitals, and a low lying vacant 羽* orbital (L∩) of the tBu2bpy ligand. Lone pair donation from the bridging oxygen atom and especially the NMe group increases the energy of the mixed metal每ligand orbital (ML) without altering the energy of the tBu2bpy 羽* orbital. As a result, the MLL∩CT state energy decreases and the absorption and emission wavelengths are red-shifted. DFT and TD-DFT calculations support the experimental results. Additional calculations on the unknown platinacycles with X = CO (7) and SO2 (8) predict a blue-shift for the MLL∩CT absorption and emission. Two nearly equal energy triplet minima were located on the DFT triplet surface for 4每6. One of these (4T每6T) has a geometry very similar to the ground-state singlet (as represented by 4每6) and is associated with the emissive 3MLL∩CT excited state. The other triplet-state (4T∩每6T∩) has a distorted structure where the platinacycle ring is twisted out of the Pt(tBu2bpy) plane. Thermal access to this distorted triplet may be responsible for the loss of photoluminescence in room temperature solutions of 4每6.