Synthesis, crystal structure, and luminescence properties of [TbGd(NAA)6(phen)2] and [Tb2(NNA)6(phen)2] · 2C3H7NO

Abstract

Lanthanide(III) heteronuclear and binuclear complexes [TbGd(NAA)6(phen)2] (1) and [Tb2(NAA)6(phen)2] · 2C3H7NO (2) (NAA = 1-naphthylacetic acid, phen = 1,10-phenanthroline) were prepared and their crystal structures were determined. In 1 and 2, each lanthanide is nine-coordinate by two bidentate-bridging and two tridentate chelating-bridging carboxylate groups, one bidentate chelating carboxylate and one phen molecule in a distorted monocapped square antiprism. The solid-state luminescence behavior and the antibacterial activities were studied. Complexes 1 and 2 exhibited characteristic emission of Tb(III) ion 5D4 → 7FJ (J = 6–0) under UV radiation at room temperature. A main excitation peak (359 nm) of 2 appears under red emission of 615 nm. By contrast, all emission peak intensities of 1 were enhanced by addition of gadolinium(III), and the 545 nm band is much stronger than the 615 nm band, attributed to, under perturbation of the ligand field, the probability of 5D4 → 7F3 transition of Tb(III) was greatly enhanced in 2. Because of perturbation of the ligand field by addition of gadolinium(III), the probability of 5D4 → 7F5 transition of Tb(III) was greatly enhanced in 1 and green fluorescence was observed. The antibacterial activity showed that the two complexes were active against Escherichia coli, Staphylococcus aureus and Bacillus subtilis.