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 (), quinoline (), 4-fluoroaniline (), P(OMe)3 (), PPh3 ()], bearing different ancillary ligands, synthesized starting from the precursor complex [(ppy)Au(FMes)(OH2)](+)[OTf](-) () 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 (ϕp) 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.

Cyclometalated Gold(III) Complexes: Synthesis, Reactivity, and Physicochemical Properties

“…[78] Ther eaction of lithiated 2,4,6-tris(trifluoromethyl)phenyl (LiFMes) with the Au III -dichloro complex 56 in dry diethyl ether afforded the monoarylated product 76 in 77 %y ield. [79] Photoluminescence emission quantum yields of 30 %(l = 441 nm) in solution and 39 %(l = 622 nm) in the solid state could be recorded, which are comparable to those of the most efficient C^N^C biscyclometalated Au III complexes described in the previous Sections.…”

Anticancer Profile of a Series of Gold(III) (2‐phenyl)pyridine Complexes

“…Complexes 3 – 6 were prepared as previously described 33. 34 Complex 2 ([(ppy)Au(FMes)(TFA)]; ppy=2‐(phenyl)pyridine, FMes=1,3,5‐tris(trifluoromethyl)benzene, TFA=trifluoroacetic acid) was synthesized in a manner similar to a method reported by Zehnder et al 34. Treatment of the previously reported [(ppy)Au(FMes)Cl]34 with a slight excess of silver trifluoroacetate in dichloromethane at room temperature for 21 h gave the desired product 2 in 97 % yield.…”

“…34 Complex 2 ([(ppy)Au(FMes)(TFA)]; ppy=2‐(phenyl)pyridine, FMes=1,3,5‐tris(trifluoromethyl)benzene, TFA=trifluoroacetic acid) was synthesized in a manner similar to a method reported by Zehnder et al 34. Treatment of the previously reported [(ppy)Au(FMes)Cl]34 with a slight excess of silver trifluoroacetate in dichloromethane at room temperature for 21 h gave the desired product 2 in 97 % yield. 1 H NMR studies revealed a diagnostic upfield shift of Δ δ =−0.7 ppm relative to the precursor complex [(ppy)Au(FMes)Cl], for the proton in the α position relative to the nitrogen atom of the cyclometalating ppy ligand to δ =8.82 ppm, upon coordination of the new ligand.…”

“…Because the complexes are luminescent,33, 34 we attempted to visualize 1 – 6 in living cells by confocal microscopy. Microscopy experiments were performed for the various gold(III) derivatives up to a concentration of 50 μ M .…”

“…Complexes 3 – 6 were synthesized according to established procedures 33. 34 All compounds that underwent biological studies had a purity in microanalysis of ≤0.4 % (i.e., >99 % pure).…”