Azo-MICs: Redox-Active Mesoionic Carbene Ligands Derived from Azoimidazolium Dyes

F Mark Chadwick; Basile F E Curchod; Rosario Scopelliti; Farzaneh Fadaei Tirani; Euro Solari; Kay Severin

doi:10.1002/anie.201813780

Azo-MICs: Redox-Active Mesoionic Carbene Ligands Derived from Azoimidazolium Dyes

Angew Chem Int Ed Engl. 2019 Feb 4;58(6):1764-1767. doi: 10.1002/anie.201813780. Epub 2019 Jan 14.

Authors

F Mark Chadwick¹, Basile F E Curchod², Rosario Scopelliti¹, Farzaneh Fadaei Tirani¹, Euro Solari¹, Kay Severin¹

Affiliations

¹ Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015, Lausanne, Switzerland.
² Department of Chemistry, Durham University, South Road, Durham, DH1 3LE, UK.

PMID: 30561125
DOI: 10.1002/anie.201813780

Abstract

Azoimidazolium dyes were used as precursors for mesoionic carbene ligands (Azo-MICs). The properties of these ligands were examined by synthesizing Rh^I , Au^I , and Pd^II complexes. Experimental (NMR, IR) and theoretical investigations show that Azo-MICs are potent σ-donor ligands. Yet, they feature a small singlet-triplet gap and very low-lying LUMO levels. The unique electronic properties of Azo-MICs allow for reversible one-electron reductions of the metal complexes, as evidenced by cyclic voltammetry.

Keywords: N-heterocyclic carbenes; azoimidazolium dyes; gold; mesoionic carbenes; rhodium.