Synthesis, crystal structure and optical property of manganese (II) halides based on pyridine ionic liquids with high quantum yield

Two novel tetrahedral Mn (II) halide single-crystals [(C 7 H 10 N) 2 ][MnCl 4 ] ( 1 ) and [(C 7 H 10 N) 2 ][MnBr 4 ] ( 2 ), based on pyridine ionic liquids, have been successfully prepared. Centimeter-sized single crystal 2 was grown through bottom seed-solution temperature-lowering method, while the 1 was synthesized by solvent slow evaporation. Structure elucidation results indicate that the two crystals crystallize in the different space groups of the same monoclinic system. Significantly, the solid crystal 2 is possessed of superior luminescence properties than 1 at room temperature. Excited by ultraviolet light, the 1 and 2 emit intense green emission bands derived from the Mn (II) 4 T(G) energy level. The fluorescent lifetimes are 384.43 and 187.83 μs, respectively, and quantum yields are 82% and 12%, respectively. Furthermore, under the excitation of X-ray, the 2 exhibits prominent X-ray fluorescence performance.