Blue and blue-green phosphorescent Au(iii) compounds based on a novel C^C chelate ligand framework are reported.

Six phosphorescent (2-phenyl)pyridine (ppy) gold(III) 2,4,6-tris(trifluoromethyl)phenyl (FMes) complexes were synthesized and investigated for their anticancer potential. The compounds demonstrated strong antiproliferative activity, with EC50 values in the low micromolar range, along with significant accumulation in HeLa cancer cells after treatment for only 6 h (up to 119 ng gold per milligram of protein as measured by high-resolution continuum source atomic spectroscopy). Enzyme inhibition studies showed interaction of the gold(III) complexes with thioredoxin reductase (TrxR), a key homeostasis-regulation flavoprotein. TrxR was inhibited with IC50 values in the micromolar range. Furthermore, five of the complexes displayed selectivity toward TrxR against glutathione reductase (GR, a disulfide reductase structurally related to TrxR) by up to >49-fold. Because no major differences in bioactivity were observed across the series, [(ppy)Au(FMes)(PPh3 )OTf] (complex 4) was chosen for further in-depth biological characterization. Complex 4 was also found to interact with guanosine monophosphate in (1) H NMR studies under long incubation times. Interestingly, 4 induced a significant increase in intracellular levels of reactive oxygen species, which led to late apoptotic events and cytocidal effects.

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.

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