Mononuclear Gold(I) bis-N-heterocyclic carbene: Synthesis and photophysical study

In the current study, 1-butyl-3-propylbenzimidazolium bromide salt (1) was used as a carbene precursor to facilitate the formation of complex [NHC-Ag(I)-NHC]PF6 (2) (NHC = N-heterocyclic carbene) via in-situ deprotonation method with Ag2O. Furthermore, the formation of complex [NHC-Au(I)-NHC]PF6 (3) was achieved through a transmetalation approach of 2 with Au(SMe2)Cl. The formation of all compounds was proved by elemental analyses, FTIR, H-1- and C-13 NMR. The successful complexation of NHC ligand with Ag(I) and Au(I) ions were suggested by the disappearance of H2' carbene proton peak which previously present in the spectrum of 1 at 9.784 ppm. In addition, the shift of C2' carbene carbon peak from 142 ppm in the spectrum of 1 to the area of 187-190 ppm in the spectra of 2 and 3 supports the formation of these metal-NHC complexes. Crystal analysis of 3 shows that the complex consists of one Au(I) ion in a linear geometry that coordinates to two NHC ligands with the presence of one PF6- cation in the lattice stabilizes the entire structure. In solid-state photophysical study of 3, upon excitation at 340 nm, complex 3 displays an intense photoluminescence with a strong emission maxima, lambda(em) = 500 nm at room temperature. (c) 2020 Elsevier B.V. All rights reserved.