Monocyclometalated (C N) Gold(III) Metallacycles: Tunable Emission and Singlet Oxygen (¹O₂) Generation Properties

Abstract

The synthesis, characterization and photoluminescent properties of four cyclometalated (C N)‐type gold(III) complexes bearing a bidentate diacetylide ligand, tolan‐2,2’‐diacetylide (tda), are reported. The complexes exhibit highly tunable excited state properties and show photoluminescence (PL) across the entire visible spectrum from sky‐blue (λPL=493 nm) to red (λPL=675 nm) with absolute PL quantum yields (PLQY) of up to 75 % in solution, the highest PLQY found for any monocyclometalated Au(III) complex in solution. As a consequence of the use of the strongly rigidifying diacetylide bidentate ligand, a significant increase in the excited state lifetimes (τ0=16–258 μs) was found in solution and in thin films. The complexes showed remarkable singlet oxygen generation in aerated solution with absolute singlet oxygen quantum yield (ϕ1Δ) values reaching up to 7.5×10−5 and singlet oxygen lifetimes (τ01Δ) in the range of 66–95 μs. Furthermore, the radiative and non‐radiative rates of singlet oxygen were determined using the ϕ1Δ and τ01Δ values and correlations are drawn between the formation of singlet oxygen and its interaction with cyclometalated (C N) gold(III) complexes.