Crystal structures and visible-light excited photoluminescence of N-methyl-4,4′-bipyridinium chloride and its Zn(II) and Cd(II) complexes

A new approach has been used to synthesize MQ+ ligand (MQ+ = N-methyl-4,4′-bipyridinium) by the reaction of 4,4′-bipyridine and chloroacetic acid, and the structure of (MQ)Cl·H2O (1) was first determined. Three new complexes containing MQ+, (MQ)CdI3 (2), (MQ)ZnI3 (3), and [(MQ)ZnCl1.53I1.47]2(MQ)ZnCl1.68I1.32 (4), were successfully obtained via a solution or hydrothermal method by reaction of MI2 (M = Cd, Zn) with , and each of which exhibits an isolated structure, with each metal atom coordinated by one MQ+ ligand and three terminal halogen atoms. Compounds – all display photoluminescence in the visible region under visible-light excitation, and the origins of the emissions have been assigned to ILCT for and the combination of ILCT and LLCT for –.