Structure, fluorescence, solvent recognition and magnetic study of multi-functional carboxylic acid ligand hexacoordinate Eu, Tb and Dy complexes

Abstract

In order to better study the properties of rare earth complexes in terms of fluorescence, magnetism, and fluorescent probes, in this work, 5-(2-carboxyphenoxy)isophthalic acid (H₃ocpia) and rare metal ions Eu³⁺, Tb³⁺, Dy³⁺ were used to synthetic metal complexes by solvothermal reaction. Then three complexes Eu(ocpia) (1), Tb(ocpia) (2) and Dy(ocpia) (3) were synthesized, their structural formulas are as follows: EuC₁₅H₇O_7, TbC₁₅H₇O₇ and DyC₁₅H₇O₇. Data on the structure acquired via an X - ray single - crystal diffractometer indicates that complexes 1, 2, and 3 possess the same spatial structures. They are two-dimensional planar structures with undulating ripples. Moreover, solid - state fluorescence tests were carried out on complexes H₃ocpia, 1, and 2, and magnetic property tests were done on complexes 2 and 3. Fluorescence recognition studies were conducted on complexes 1 and 2 in dispersed systems. The solid-state fluorescence results show that complexes 1 and 2 have excellent fluorescence properties, with higher fluorescence intensity than the ligand. The CIE chromaticity coordinates of complexes 1 and 2 are (0.59, 0.34) and (0.33, 0.62), respectively, and exhibit bright characteristic lights of europium and terbium under fluorescent lamps. Magnetic susceptibility measurements reveal that compounds 2 and 3 exhibit antiferromagnetic coupling behavior between adjacent metal centers. Fluorescence recognition studies have shown that complexes 1 and 2 exhibit good recognition of acetone in dispersed systems, the detection thresholds were determined to be 0.063 vol.% for complex 1 and 0.136 vol.% for complex 2.