Coinage metal complexes of N‐heterocyclic carbene bearing nitrile functionalization: Synthesis and photophysical properties

Abstract

A new series of N‐heterocyclic carbene (NHC) ligand precursors ( 1 and 2 ) with their [Ag(I)(NHC) 2 ]PF 6 complexes ( 3 and 4 ) and [ClAu(I)(NHC)] complexes ( 5 and 6 ) are reported. Complexes 5 and 6 were synthesized via transmetalation reaction using either 3 or 4 and AuCl(SMe 2 ) as reactants, respectively. All the synthesized compounds were fully characterized using elemental analyses and Fourier transform infrared, 1 H NMR and 13 C NMR spectroscopies. In the crystal structures of 3 , 5 and 6 , the Ag(I) and Au(I) ions are in a linear geometry. The entire structure of 3 is stabilized by significant π–π interactions, while the structures of 5 and 6 are stabilized with the presence of aurophilic interactions between the adjacent Au(I) ions as well as CH–π or π–π interactions. From photoluminescence studies, complexes 5 and 6 show dual‐emission characteristics. The higher‐energy fluorescence originates from 1 XLCT mixed with 1 MLCT, while the lower‐energy phosphorescence is ascribed to 3 XLCT and 3 MLCT with small contribution of 3 ILCT, as evidenced by density functional theory (DFT) and time‐dependent DFT calculations of the modelled molecules.