Experimental and Computational Study on Photophysical Properties of Mesoionic Chalcogenones

Synthesis of stable class 5 mesoionic benzo[c]tetrazolo[2,3-a]cinnolinium thiolate, dicyanomethylide, and amides

Although class 5 mesoionic compounds show interesting electrical behaviour, they are generally unstable, readily undergoing ring-opening reactions. We designed and synthesized a bridged mesoionic derivative, benzo[c]tetrazolo[2,3-a]cinolinium (BTC), as a stable class 5 mesoionic compound, which was further transformed to the corresponding thiolate, cicyanomethylide, and amide. The intramolecular bridging imparted stability to the BTC thiolates and amides: the BTC thiolates were unsusceptible to ring-opening at high temperatures, and the BTC amides were stable in the absence of electron-withdrawing groups on the amide nitrogen. The properties of the BTC thiolate were compared with those of 2,3-diphenyltetrazolium derivatives based on UV-Vis absorption spectroscopy, single-crystal X-ray diffraction and quantum calculations.

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 ( 1-3 ) displayed considerable quantum yields (QY: up to 43.8%) and could be potentially applied as luminescent materials.