Monoanionic Phosphorus‐Supported Air Stable Cu(I)8, Ag(I)7, and Ag(I)5 Nanoclusters Exhibiting TADF: A Novel Photocatalyst for Stereoselective Carbene Transfer Reactions

Abstract

AbstractApplications of structurally well‐defined coinage‐metal nanoclusters (NCs) as optoelectronic materials and homogeneous catalysts have been restricted due to their inherent lower stability. Herein, the syntheses, structural characterizations, and photoluminescence properties of three novel air‐stable coinage‐metal(I) NCs‐supported by carbene‐anchored monoanionic phosphorus (cAAC=P−) with molecular formulae [(Cy‐cAACP)4(Cu)4(CuCl)4] (4), [(Cy‐cAACP)4(Ag)4(AgOTf)3] (5), and [(Cy‐cAACP)4(Ag)5]NTf2 (6) (cAAC = cyclic alkyl(amino) carbene; Tf = CF3SO2) exhibiting thermally activated delayed fluorescence (TADF) are reported. Apart from attractive metallophilic interactions [M─M; M ═ Cu, Ag], the enhanced kinetic and thermodynamic stability of 4–6 can be attributed to the excellent π‐accepting ability of cAAC=P− surrounding the metallic cores. cAAC=P− anion is generated either in situ by anion‐induced cleavage of P−Sb/B bonds of corresponding stibanyl/boryl phosphaalkenes in the presence of coinage‐metal(I)‐Cl/OTf/NTf2 salts or by directly introducing alkali‐metal phosphinidenide. The TADF properties of 4–6 are established by smaller energy gaps between the lowest singlet excited state and triplet excited state. In solid‐state, the delayed fluorescence lifetimes of 4–6 are found to be in the microsecond range with absolute photoluminescence quantum yields up to 20%. The redox‐active Cu(I)8 NC 4 is successfully exploited as an efficient photo‐catalyst for the selective carbene transfer reaction at ambient conditions, affording cyclopropanated indoles/styrenes with excellent yields and diastereoselectivity.