Syntheses And Properties Of Two Series Of Dichlorobenzoate-based Lanthanide Complexes

In this paper,eight types of lanthanide are used as the central metals,and1,10-phenanthroline?phen?is used as the auxiliary ligand.Sixteen lanthanide organic complexes were synthesized with 2,5-dichlorobenzoic acid?2,5-HDCB?and 4-hydroxy-3,5-dichlorobenzoic acid?H₂L?under solution diffusion and hydrothermal conditions,respectively.They were characterized by X-ray single-crystal diffraction,IR,X-ray powder diffraction,and thermogravimetric analysis,and the partial complexes were studied for photoluminescence and magnetic properties.1.The ethanol solution of 2,5-dichlorobenzoic acid?2,5-HDCB?and1,10-phenanthroline?phen?were slowly dropped into an aqueous solution of lanthanide chloride and allowed to stand at room temperature for two weeks.Complexes Ln₂[?2,5-DCB?₃?phen??H₂O?]₂·2H₂O[Ln=Nd?1?,Sm?2?,Eu?3?,Gd?4?,Tb?5?,Dy?6?]and Ln₂[?2,5-DCB?₃?phen??H₂O?]₂·4H₂O[Er?7?,Yb?8?]show a dinuclear zero-dimensional structure formed by four 2,5-DCB anions bridging two Ln^III ions.Adjacent zero-dimensional structures are connected by a hydrogen bond interaction into a one-dimensional chain.Adjacent one-dimensional chains are extended to a two-dimensional layer by?-?interactions.The photoluminescent properties of complexes 1–3,5,6 and 8 were investigated and the characteristic luminescence of lanthanide ions sensitized by2,5-DCB was shown.Magnetic studies have shown that complexes 4,6 and 7exhibit weak ferromagnetic interactions between lanthanide ions in the low temperature range,and complex 6 also shows slow magnetic relaxation behavior at zero DC magnetic field.2.By mixing lanthanide chloride,4-hydroxy-3,5-dichlorobenzoic acid?H₂L?and 1,10-phenanthroline?phen?in 23 mL Teflonlined autoclave,a series of complexes Ln?L??HL??phen?[Ln=Nd?9?,Sm?10?,Eu?11?,Gd?12?,Tb?13?,Dy?14?,Er?15?,Yb?16?]were obtained under hydrothermal conditions.Complexes 9-16 show a two-dimensional network structure constructed by rigid ligand H₂L connecting dinuclear units.The photoluminescence properties of the complexes 10,11,13 and 14 were investigated.In addition,the magnetic properties of the complex 14 have also been studied,which exhibit ferromagnetic interactions in the Dy₂ dimer in the high temperature range and have a high effective energy barrier(U_eff) value.