Synthesis, Structure, Photoluminescence and Theoretical Study of (MQ)(CdBr4) with MQ2+ Generated In Situ (MQ2+ = N-Me-4,4′-bipyridinium)

A new compound (MQ)(CdBr4) (1; MQ2+ = N-Me-4,4′-bipyridinium), in which the MQ2+ was generated in situ, has been synthesized via hydrothermal reaction. The title compound features an isolated structure, based on discrete MQ2+ moieties and tetrahedral cadmium atoms terminally coordinated by four bromine atoms. The MQ2+ moieties and tetrabromo-cadmium dianions are linked via hydrogen bonds. Photoluminescent investigation reveals that the title compound displays a strong blue-light emission, which is attributed to a ligand-to-ligand charge-transfer (LLCT; from the HOMO of the bromine atoms to the LUMO+1 of the MQ2+ moieties) mechanism probed by molecular orbital (MO) calculations