Gold(I) Complexes with Bulky Phosphanes: A Dual Approach to Triplet Harvesting and Hydroamination Catalysis

Two families of mononuclear gold(I) complexes featuring Au-chromophore units, with chromophores being carbazole (a), phenanthrene (b), or dibenzofuran (c), were synthesized. The Au(I) atoms are coordinated to two phosphanes, either PMe₂Ar^Xyl2 (Ar^Xyl2 = 2,6-C₆H₃-(2,6-C₆H₃-Me₂)₂) (P1) or the bulkier PCyp₂Ar^Xyl2 (Cyp = cyclopentyl) (P2). The photophysical properties of these complexes were extensively studied, with a particular focus on the effects of phosphane bulkiness and chromophore electron-donating capacity on triplet state quantum yields (Φ_T). Nanosecond-laser flash photolysis measurements were employed to calculate Φ_T. Time-dependent density functional theory (TD-DFT) calculations supported the absorption and emission assignments, providing insights into the electronic state gaps involved in photophysical processes and their relative populations. The parent complex AuClP2 in combination with NaBAr₄^F, as a chloride scavenger, served as an efficient catalyst for the hydroamination of a variety of alkynes and amines, under mild conditions and with low Au loading (0.1-0.2 mol %). Luminescent studies allowed us to check the active catalytic species.