Luminescent 2-phenylbenzothiazole cyclometalated Pt II and Ir III complexes with chelating P^O ligands.

Two series of cyclometalated Pt ^II and Ir ^III complexes with general formulas [Pt(pbt){PPh ₂ (R)-κ P , O }] (2a-2c) and [Ir(pbt) ₂ {PPh ₂ (R)-κ P , O }] (3a-3c), where Hpbt is 2-phenylbenzothiazol and PPh ₂ (R) is a diphenylphosphino donor functionalized deprotonated acid (R = o -C ₆ H ₄ CO ₂ a, o -C ₆ H ₄ SO ₃ b, CH ₂ CH ₂ CO ₂ c) are presented. The structures of 1, 2a-2c, 3a and 3b were confirmed by single X-ray diffraction analyses, and the intermolecular interactions in 2a were studied using Hirshfeld surface analysis and non-covalent interaction (NCI) methods on its X-ray structure. Their photophysical properties were investigated by absorption and emission analyses [CH ₂ Cl ₂ , solid (298, 77 K) and doped polystyrene (PS) films], supported by TD-DFT calculations on 1, 2a-2c and 3a. The Pt ^II complexes exhibit bright phosphorescence in the region 525-542 nm, ascribed to a mixed ³ IL/ ³ MLCT excited state with a predominant ³ IL contribution. The Ir ^III derivatives (3a-3c) show orange photoluminescence (535-584 nm, 298 K), blue shifted at 77 K (527-560 nm), originated from the admixture of ³ IL/ ³ MLCT/ ³ LLCT excited states. Interestingly, the photoluminescence quantum yields of the Pt complexes 2a-2c ( ϕ = 46.5-66.5%) in PS films are remarkably higher than those of the corresponding iridium complexes ( ϕ = 17.3-32%) and the precursor 1 ( ϕ = 17%). The calculated ³ MC- ³ IL/ ³ MLCT energy gap for 2a and 3a accounts for the higher quantum yield of the Pt in relation to the Ir complex.