Lanthanide complexes with disulfide ligand generated in situ: Syntheses, crystal structures and fluorescent properties

摘要

Five new lanthanide complexes [Ln_2(DTDN)_4(phen) _4]·7H_2O·2H_3O~+ (Ln = Nd (1), Sm (2), Eu (3), Tb (4), Dy (5), H_2DTDN = 2,2′- dithiodinicotinic acid, phen = 1,10-phenanthroline) have been solvothermally synthesized and characterized by single-crystal X-ray diffraction, elemental analyses, IR spectra, and TG analyses. By in situ oxidation of 2-mercaptonanicotinic acid (2-H_2MN), the expected ligand H _2DTDN was generated. All crystals are isostructural and crystallize in monoclinic system with space group C_2/c. The metal center is eight-coordinated completely by four carboxylic oxygen atoms from four different DTDN~(2-) ligands, and four nitrogen atoms from two phen molecules with a distorted square-antiprismatic geometry. The structures can be considered as two-dimensional (2D) structures and further linked by hydrogen bonds into the final trinodal 4-connected network. Photoluminescence studies revealed that complexes 2-5 exhibit strong fluorescent emission bands in the solid state at room temperature.