Synthesis, Characterization and Photophysical Properties of Mesoionic N-Heterocyclic Imines.

N-heterocyclic imines are widely used in transition-metal chemistry, main-group chemistry as well as catalysis, due to their enhanced basicity and nucleophilicity which benefit from their ylidic form. As their analogs, mesoionic N-heterocyclic imines, which feature more highly ylidic form, is still in its infancy though excellent works also achieved. Here we reported the synthesis, characterization and photophysical properties of mesoionic N-heterocyclic imines. TD-DFT are employed to get deeper insight into the mechanism of the photophysical behaviors. The unsubstituted mesoionic N-heterocyclic imines (4-6) displayed considerable quantum yields (QY: up to 43.8%) and could be potentially applied as luminescent materials.