Visible-light-induced chlorine photoelimination from acridinium-phosphine gold(iii) complexes

With the objective of developing transition metal complexes that undergo visible-light-induced halogen photoelimination, we have synthesized trivalent gold trichloride complexes featuring an acridinium unit. Photoexcitation of the acridinium chromophore with visible light allows for facile photoreduction to the corresponding Au^I complexes, highlighting the photolability imparted by the acridinium moiety onto the Au^III centre. The photolysis is remarkably clean, including in the solid state where the photodechlorination is essentially trap-free. Transient absorption spectroscopic studies reveal that the photochemistry is derived from a pathway whereby the S₁ excited state of the acridinium undergoes energy transfer to the Au^III center to prompt the photogeneration of Cl radicals.