A series of luminescent isocyanorhenium(I) complexes with chelating acyclic diaminocarbene ligands (NAC) has been synthesized and characterized. Two of these carbene complexes have also been structurally characterized by X-ray crystallography. These complexes show blue-to-red phosphorescence, with the emission maxima not only considerably varied with a change in the number of ancillary isocyanide ligands but also extremely sensitive to the electronic and steric nature of the substituents on the acyclic diaminocarbene ligand. A detailed study with the support of density functional theory calculations revealed that the lowest energy absorption and phosphorescence of these complexes in a degassed CH2Cl2 solution are derived from the predominantly metal-to-ligand charge-transfer [d pi(Re) -> pi*((NC)-C-Lambda)] excited state. The unprecedented anion-binding and CO2-capturing properties of the acyclic diaminocarbene have also been described.