In Situ Preparation, Structure, Photoluminescence and Theoretical Study of an Unusual Bismuth Complex

A novel bismuth photoluminescent material, (N,N'-dimethyl-2,2'-bipy)2(Bi2Cl10) · 2H2O (1) (bipy = bipyridine), with the N,N'-dimethyl-2,2'-bipy2+ moiety obtained in situ, has been synthesized under solvothermal conditions and characterized by single-crystal X-ray diffraction. Compound 1 is characterized by an isolated structure, consisting of N,N'-dimethyl- 2,2'-bipy2+ cations, Bi2Cl10 4- anions and lattice water molecules. Photoluminescence experiments with solidstate samples discover that compound 1 exhibits a strong emission in the green region. Time-dependent density functional theory (TDDFT) calculation reveals that the essence of the photoluminescence of 1 can be assigned to the combination of the metal-to-ligand charge transfer (MLCT) (from the HOMO of the bismuth ion to the LUMO of the N,N'-dimethyl-2,2'-bipy2+ moiety) and the ligand-to-ligand charge transfer (LLCT) (from the HOMO of the chloride ions to the LUMO of the N,N'-dimethyl-2,2'-bipy2+ moiety).