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. Photo luminescent investigation reveals that the title compound displays a strong blue-light emission, which is attributed to a ligand-to-ligand charge-transfer; from the HOMO of the bromine atoms to the LUMO+1 of the MQ2+ moieties) mechanism probed by molecular orbital calculations