We report the formation of dinuclear complexes from, and photochemical oxidation of, (CH3)3-Pt­(IV)­(N^N) (N^N = 1,2-diimine derivatives) complexes of thiophenolate ligands to the analogous sulfinates (CH3)3Pt­(N^N)­(SO2Ph) and structural, spectroscopic, and theoretical studies of the latter revealing tunable photophysics depending upon the 1,2-diimine ligands. Electron-rich thiolate and conjugated 1,2-diimines encourage formation of thiolate-bridged dinuclear complexes; smaller 1,2-diimines or electron-poor thiolates favor mononuclear complexes. Photooxidation of the thiolate ligand yields hitherto unreported Pt­(IV)-SO2R complexes, promoted by electron-deficient thiolates such as 4-nitrothiophenol, which exclusively forms the sulfinate complex. Such complexes exhibit expected absorptions due to π-π* ligand transitions of the 1,2-diimines mixed with spin-allowed singlet MLCT (d-π*) at relatively high energy (270–290 nm), as well as unexpected broad, lower energy absorptions between 360 and 490 nm. DFT data indicate that these low energy absorption bands result from excitation of Pt–S and Pt–C σ-bonding electrons to π* orbitals on sulfinate and 1,2-diimine, the latter of which gives rise to emission in the visible range.

a 2,6-Bis(2-quinolyl)-4(1H)-pyridone 1, a novel quinoline analogue of the well-known ligand 2-terpyridone, shows unusual fluorescence with a large Stokes shift and low energy emission. Pyridine-pyridone tautomerism is investigated by NMR and theoretical methods and indicates that the low energy emission is from the pyridine form. 1 reacts with Ag(I) salts to give a double helical Ag 2 N 6 core showing a BLUE shift in fluorescence with respect to the free ligand, which has been characterised experimentally and theoretically as involving an unusual mixed MLCT/ILCT excited state and emission from a singlet state.