Circularly Polarized Phosphorescence of Helically Chiral Dinulcear Pd(II) Diacetylide Complexes with Oxazolinyl-Type Tridentate Cyclometalated Ligands

The synthesis of stable helically chiral dinuclear Pd(II) diacetylide complexes exhibiting intramolecular Pd···Pd interactions in both fluid and solid states is reported, utilizing foldable bis(arylacetylide) as electron-donating ligands. A systematic investigation of the substitution effect of chiral oxazolinyl-type C^N^N moieties and foldable bis(arylacetylide) ligands, with and without alkoxy linker groups, on the molecular configuration and circularly polarized luminescence (CPL) properties of the chiral dinuclear Pd(II) complexes has been conducted. The emission peak maximum was found to be tunable from 650 to 715 nm, and CPL dissymmetry factors (|glum|) up to 3.0 × 10-3 have been obtained. The metal-metal-to-ligand charge transfer (MMLCT) nature of the phosphorescence was assigned through analysis of the photophysical properties and TDDFT calculations. Additionally, circularly polarized organic light-emitting diode (OLED) devices employing the helically chiral Pd(II) complexes as phosphorescent emitters have been successfully fabricated, achieving a maximum |gEL| value of approximately 3.0 × 10-3.