Shift It to the Red: The Synthesis of Dicarbonyl Re(I) Complexes with Two Different Diimine Ligands and Near-Infrared Luminescence

In this contribution, we present an efficient synthetic method for obtaining Re(I) mixed-ligand bis-diimine dicarbonyl complexes of general formula [Re(NN1)(NNi)(CO)2]OTf (NN1 = neocuproine), starting from bis-acetonitrile rhenium(I) precursor [Re(NN1)(CO)2(NCMe)2]OTf. This method allows introduction of different diimine ligands, which contain fused moieties and electron-withdrawing functional groups. All complexes obtained demonstrate deep red to near-infrared (NIR) emission both in solution and in the solid state, achieving 845 nm. The 3MLCT character of the emissive excited state was confirmed by TD-DFT calculations of the electronic structures for the complexes considered.