Synthesis And Spectroscopy Of Anionic Cyclometalated Iridium(Iii)-Dithiolate And -Sulfinates-Effect Of Sulfur Dioxygenation On Electronic Structure And Luminescence

A new anionic heteroleptic Ir(III)-dithiolate complex Ir(ppy)2(benzene-1,2-dithiolate) (ppy = 2-phenylpyridine, [IrSS]-) undergoes very fast air oxidation to form a monosulfinate complex [IrSSO2]-, which can be further dioxygenated by O-2 or H2O2 to give a disulfinate complex [IrSO2SO2]-, which has been characterized by X-ray crystallography. The dioxygenation is accompanied by changes in the electronic structures of the complexes, leading to blue shift of emission from [IrSS]- (lambda(max) = 665 nm) to [IrSSO2]- (lambda(max) = 556 nm) and to [IrSO2SO2]- (lambda(max) = 460 nm). The molecular and electronic structures of the complexes are probed by DFT calculations. Time-dependent DFT (TD-DFT) calculations show the lowest energy spin-allowed electronic transitions for [IrSS]- and [IrSSO2]- are mainly ligand (3p orbital of S)-to-ligand (pi orbitals of ppy)-charge-transfer transition, whereas the lowest energy electronic transition in [IrSO2SO2]-isedominantly metal-to-ligand-charge transfer in nature.