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

Dyeing for a lower LUMO: Mesoionic carbenes derived from azoimidazolium dyes (Azo‐MICs) are exceptionally good σ‐donors. Furthermore, they have very low‐lying LUMO levels, allowing for ligand‐centered one‐electron reductions.

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.

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