Ligand‐Dependent Locally Excited and Charge‐Transfer Emission in Linear Copper(I) Mesoionic Carbene Luminophores

ABSTRACT We describe the synthesis of a family of photoemissive linear Cu(I) complexes bearing mesoionic carbenes (MIC) and amido ligands of the general formula Cu(MIC)NR 2 (NR 2 = carbazolide, diphenylamide). Careful tuning of the electronic and structural properties of both ligands enables modulation of the emission wavelengths from 400 to 520 nm and determines whether emission occurs mainly from locally excited or charge‐transfer states. Complexes containing naphthyl substituents in the MIC fragment generally show structured locally excited emissions, which is consistent with the presence of a low‐lying triplet state localized on the naphthyl fragment. In contrast, complexes without the naphthyl group generally display broader emission with a larger charge transfer contribution. The Cu complex supported by Naph 2 Mes NPh 2 represents a unique case, displaying both a high‐energy fluorescence and a lower‐energy vibronically structured phosphorescence band. These results show that tuning the ligand‐centered triplet state enabled us to exert exquisite control over the nature of the absorption and emission mechanisms of these emissive linear Cu(I) complexes.