Luminescent monocyclometalated cationic gold(iii) complexes: synthesis, photophysical characterization and catalytic investigations

Abstract

Stable, luminescent, and cationic monocyclometalated gold(III) monoaryl complexes of the type [(ppy)Au(FMes)(L)]⁺[OTf]⁻ [L = 4-phenylpyridine (3), quinoline (4), 4-fluoroaniline (5), P(OMe)₃ (6), PPh₃ (7)], bearing different ancillary ligands, synthesized starting from the precursor complex [(ppy)Au(FMes)(OH₂)]⁺[OTf]⁻ (2) are reported. The preliminary assignment of the structure of the complexes by various nuclear magnetic resonance spectroscopy techniques and elemental analysis has been further corroborated by single-crystal X-ray diffraction studies. The complexes exhibit room temperature phosphorescence in solution, in neat solids and in doped PMMA films. Detailed photophysical investigations of the complexes in solution, in neat solids and in PMMA films revealed the successful tuning of the emission quantum yield (ϕ_p) based on the electronic properties of the ancillary ligands. The catalytic photo-oxidation of benzylic amines to their corresponding imines using molecular oxygen as the oxidant was successfully achieved in the presence of the luminescent Au(III) complexes. It is also established that the photocatalytic performance was strongly governed by the electronic properties of the ancillary ligands on the photosensitizer as well as by the steric bulk of the substrates.