Synthesis and Spectroscopy of Anionic Cyclometalated Iridium(III)-Dithiolate and -Sulfinates—Effect of Sulfur Dioxygenation on Electronic Structure and Luminescence

Abstract

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 O2 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](-) (λ(max) = 665 nm) to [IrSSO2](-) (λ(max) = 556 nm) and to [IrSO2SO2](-) (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 [IrSS](-) and [IrSSO2](-) are mainly ligand (3p orbital of S)-to-ligand (π* orbitals of ppy)-charge-transfer transition, whereas the lowest energy electronic transition in [IrSO2SO2](-) is predominantly metal-to-ligand-charge transfer in nature.

Ir(2-Phenylpyridine)2(benzene-1,2-dithiolate) Anion as a Diastereoselective Metalloligand and Nucleophile: Stereoelectronic Effect, Spectroscopy, and Computational Study of the Methylated and Aurated Complexes and their Oxygenation Products

“…The latter forms slightly puckered IrS 2 C 2 rings with IrS 2 −S 2 C 2 dihedral angle of 6.41°−27.64°, resulting from pyramidalization of the S atoms caused by the additions. 12 The OS bond lengths and stretching frequencies (1019 and 1149 cm −1 ) and OSO angle of the coordinated sulfinate in Figure S14 and Table S1) shows a puckered IrS 2 C 2 ring with IrS 2 −S 2 C 2 dihedral angle of 19.31°.…”

“…Our previous DFT calculations showed that the optimized structure of [IrSS] − has C 2 symmetry (Figure 1). 12 The lowest unoccupied molecular orbital (LUMO) is a π* orbital of the ppy ligands, and the b 2 -symmetry highest occupied molecular orbital (HOMO) is an antibonding π* orbital arising from the interactions of the filled 3p y orbitals of the two thiolate S atoms (56.8%) with the filled 5d yz orbital of the Ir 3+ ion (11.95%) ( Figure 4) and is perpendicular to the C 2 axis. Viewing along the y-axis shows that for the Λ isomer, the lobes of the 3p y components (the lone pairs of the S atoms) in the HOMO on the re faces of both S atoms are blocked by the ortho-H atoms of the pyridyl rings, whereas the lone pairs on the si faces are fully exposed (Figure 3).…”

“…Konno et al reported the formation of a novel chiral octanuclear [Au 2 {[Pd{Co(aet) 3 } 2 ]} 2 ] 6+ (aet = 2-aminoethanethiolate) from coordination of the thiolate S atoms of [Pd{Co(aet) 3 } 2 ] 2+ to Au(I) ions (Scheme 5). 6 They have shown that their reaction is diastereoselective, producing only the (Δ) 4 (R) 12 and (Λ) 4 (S) 12 isomers.…”

“…The thiolate−sulfinate complex [IrSSO 2 ] − (Scheme 2) reported in our previous study has a similar HOMO (3p of S (50.20%) and dπ of Ir (18.33%)). 12 The LUMO and LUMO+1 are predominantly π* orbitals of the ppy ligand. Methylation or auration of the thiolate S removes the high-lying 3p lone pair, leading to completely different HOMOs in 1b, 1c, 2a, 2b, 3, and 4, which are mainly composed of the 5d orbitals of Ir and ppy π orbitals.…”

“…Single-point and time-dependent (TD) DFT calculations were performed at the same functional, and basis sets with acetonitrile solvent effect described by polarizable continuum (2) (14) 79.47 (15) Ir(1)−S(2)−C(28) 105.05 (14) 105.97 (15) . 12 Darensbourg et al showed that methylation of a Ni(II)-dithiolate complex made it less reactive toward oxygenation. 26 Similarly, we found that 1a is much more air-stable than [IrSS] − as it takes more than three weeks for air to oxidize a 1 × [IrSS] − can act as a metalloligand in complexing Ph 3 PAu + to form the trimetallic complex 4.…”