Efficient NIR electrochemiluminescent dyes based on ruthenium() complexes containing an N-heterocyclic carbene ligand

Three new ruthenium( ii ) complexes containing an N-heterocyclic carbene (NHC) ligand (RuNHC) have been successfully synthesized and proved to be efficient near-infrared (NIR) ECL (electrogenerated chemiluminescence) luminophores. In addition to the advantages of the lower-charge main motif (+1), the much lower oxidation potentials, and the longer metal to ligand charge transfer (MLCT) absorption bands, most importantly, these RuNHC complexes show higher, or at least comparable, ECL efficiency compared with Ru(bpy) 3 2+ under the same experimental conditions; this demonstrates their great potential for applications in the NIR ECL imaging field in the future. Ruthenium( ii ) complexes containing an N-heteroleptic carbene ligand have been revealed as highly efficient NIR electrochemiluminescent dyes for the first time.