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, [<b>IrSS</b>]⁻) undergoes very fast air oxidation to form a monosulfinate complex [<b>IrSSO</b>_<b>2</b>]⁻, which can be further dioxygenated by O₂ or H₂O₂ to give a disulfinate complex [<b>IrSO</b>_<b>2</b><b>SO</b>_<b>2</b>]⁻, 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 [<b>IrSS</b>]⁻ (λ_max = 665 nm) to [<b>IrSSO</b>_<b>2</b>]⁻ (λ_max = 556 nm) and to [<b>IrSO</b>_<b>2</b><b>SO</b>_<b>2</b>]⁻ (λ_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 [<b>IrSS</b>]⁻ and [<b>IrSSO</b>_<b>2</b>]⁻ are mainly ligand (3p orbital of S)-to-ligand (π* orbitals of ppy)-charge-transfer transition, whereas the lowest energy electronic transition in [<b>IrSO</b>_<b>2</b><b>SO</b>_<b>2</b>]⁻ is predominantly metal-to-ligand-charge transfer in nature