A new phosphorescent heteroleptic cuprous complex with a neutral 2-methylquinolin-8-ol ligand: synthesis, structure characterization, properties and TD-DFT calculations

Luminescent Cu^I complexes have emerged as promising substitutes for phosphorescent emitters based on Ir, Pt and Os due to their abundance and low cost. The title heteroleptic cuprous complex, [9,9-dimethyl-4,5-bis(diphenylphosphanyl)-9H-xanthene-κ²P,P](2-methylquinolin-8-ol-κ²N,O)copper(I) hexafluorophosphate, [Cu(C₁₀H₉NO)(C₃₉H₃₂OP₂)]PF₆, conventionally abbreviated as [Cu(Xantphos)(8-HOXQ)]PF₆, where Xantphos is the chelating diphosphine ligand 9,9-dimethyl-4,5-bis(diphenylphosphanyl)-9H-xanthene and 8-HOXQ is the N,O-chelating ligand 2-methylquinolin-8-ol that remains protonated at the hydroxy O atom, is described. In this complex, the asymmetric unit consists of a hexafluorophosphate anion and a whole mononuclear cation, where the Cu^I atom is coordinated by two P atoms from the Xantphos ligand and by the N and O atoms from the 8-HOXQ ligand, giving rise to a tetrahedral CuP₂NO coordination geometry. The electronic absorption and photoluminescence properties of this complex have been studied on as-synthesized samples, whose purity had been determined by powder X-ray diffraction. In the detailed TD-DFT (time-dependent density functional theory) studies, the yellow emission appears to be derived from the inter-ligand charge transfer and metal-to-ligand charge transfer (M+L')→LCT excited state (LCT is ligand charge transfer).