Luminescent 2-phenylbenzothiazole cyclometalated PtII and IrIII complexes with chelating P∧O ligands

Two series of cyclometalated Pt-II and Ir-III complexes with general formulas [Pt(pbt){PPh2(R)-kappa P,O}] (2a-2c) and [Ir(pbt)(2){PPh2(R)-kappa P,O}] (3a-3c), where Hpbt is 2-phenylbenzothiazol and PPh2(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 [CH2Cl2, 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 (IL)-I-3/(MLCT)-M-3 excited state with a predominant (IL)-I-3 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 (IL)-I-3/(MLCT)-M-3/(LLCT)-L-3 excited states. Interestingly, the photoluminescence quantum yields of the Pt complexes 2a-2c (phi = 46.5-66.5%) in PS films are remarkably higher than those of the corresponding iridium complexes (phi = 17.3-32%) and the precursor 1 (phi = 17%). The calculated (MC)-M-3-(IL)-I-3/(MLCT)-M-3 energy gap for 2a and 3a accounts for the higher quantum yield of the Pt in relation to the Ir complex.

Automated summary

This study presents the synthesis, structural characterization, and photophysical properties of cyclometalated Pt-II and Ir-III complexes with different functionalized phosphine ligands. The Pt complexes exhibit higher photoluminescence quantum yields in PS films compared to the Ir complexes and the precursor. The higher quantum yield of Pt complexes can be explained by the calculated energy gap between the metal-centered triplet and the ligand-centered triplet/metal-to-ligand charge transfer states.