Hydrothermal Synthesis, Crystal Structures, and Fluorescence Properties of Ni(II)-Ln(III) Complexes (Ln = Sm, Pr, Eu)

Three novel 3d-4f heterometal complexes [Ln(NiL)(3)(Btca)(NO3)] center dot xH(2)O (Ln = Sm(III) (I), Pr(III) (II), Eu(III) (III) (H2L = 2,3-dioxo-5,6,14,15-dibenzo-1,4,8,12-tetraazacyclo-pentadeca-7,13-dien, H(2)Btca = benzotriazole-5-carboxylic acid) were solvothermally synthesized and characterized by singlecrystal X-ray diffraction (CIF files CCDC nos. 1555557 (I), 1555555 (II), 1555556 (III)). They crystallized in the monoclinic space group P2(1)/n for I (x = 1.5) and C2/c for (II) and (III) (x = 1), respectively. In these complexes, the central Ln(III) and external nickel ions are bridged by macrocyclic oxamide groups. The metal center of Ln(III) resides in a distorted bicapped square antiprism surrounding with six oxygen atoms of three oxamide groups, two oxygen atoms of Btca(2-) ion and two oxygen atoms of NO3 (-). Furthermore, there are C-H center dot center dot center dot O and/or C-H center dot center dot center dot N hydrogen bond interactions among nitrate, benzotriazole-5-carboxylate, macrocyclic oxamide and water to form three-dimensional superamolecular architecture. The fluorescence properties of the compounds I and II are also discussed.