Dual Emissive and Long-lived Copper(I) Mesoionic Carbene Luminophores

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)NR2 (NR2 = carbazolide, diphenylamide). Careful tuning of the electronic and structural properties of both ligands enables modulation of the emission wavelengths from 400 to 520 nm. We observe that the emission mechanism is highly dependent on the nature of the ligands and exhibits a dichotomy in behavior. Complexes bearing diphenylamide ligands CuMesMICNaphNPh2 and CuMesMIC3,5-CF3PhNPh2 and complexes containing a combination of carbazolide and electron-rich MIC ligands such as CuMesMICNaphCz and Cu3,5-MePhMICNaph Cz emit from locally excited (LE) states, while complexes bearing electron-rich carbazolide and electron-poor MIC ligands emit from charge transfer (CT) states. A rational design of the ligands enabled us to exert exquisite control over the nature of the absorption and emission mechanisms of these emissive linear CuI complexes.