Gold(I)–Alkynyl Complexes with an N‐Donor Heterocyclic Ligand: Synthesis and Photophysical Properties

Abstract

A series of AuI–alkynyl complexes, containing an N‐donor ligand (2‐phenylpyrido[2,1‐a]pyrrolo[3,2‐c]isoquinoline) coordinated through the pyrrole nitrogen atom, were synthesized and characterized using X‐ray crystallography and NMR spectroscopy. The obtained compounds are luminescent in solution and in the solid state, and the emission intensity depends on the nature of the alkynyl ligand to give values of quantum yield equal to 8.0 and 6.5 % for complexes 3 and 4, respectively, in dichloromethane solution at room temperature. The observed emission is ligand‐centred fluorescence that is atypical for complexes of this type, which usually display phosphorescence determined by strong spin‐orbit coupling with the heavy‐metal ion. DFT calculations of the electronic structure of the complexes showed that the contribution of the gold orbitals to the states responsible for emission is nearly negligible and results in a low intersystem crossing rate and suppression of phosphorescence in the complexes studied.