Dinuclear rare-earth picrate complexes based on a multidentate amide ligand: syntheses, crystal structures, and luminescence properties

Abstract

A new amide-based multidentate ligand, N,N′-1,2-ethanediyl-bis{2-[(N,N-diethylcarbamoyl)methoxy]benzamide} (L) reacts with M(Pic)3 · 6H2O to give rare-earth picrate complexes [M2L2(Pic)4(H2O)2](Pic)2 (M = La (1), Nd (2), Eu (3), Gd (4), Tb (5), Dy (6), Yb (7), Y (8)). X-ray single-crystal diffraction analyses indicate that dinuclear complexes 3 · 2C4H8O2, 6 · 2C4H8O2, and 8 · 2CH3CN are isomorphous. Each metal is nine-coordinate by four oxygen atoms of two ligands, four oxygen atoms of two bidentate picrates, and one water molecule with a distorted monocapped square antiprism. With hydrogen bonds between the free picrate anions and the coordination cations the complexes exhibit 2-D layers. The luminescent properties of 3 [Eu2L2(Pic)4(H2O)2](Pic)2 are described and factors that influence luminescent intensities are also discussed.