Structures, Single-Molecule Magnets, and Fluorescent Properties of Four Dinuclear Lanthanide Complexes Based on 4-Azotriazolyl-3-hydroxy-2-naphthoic Acid

Four isostructural dinuclear lanthanide complexes based on 4-azotriazolyl-3-hydroxy-2-naphthoic acid (H(3)ATNA) and 3-hydroxy-2-naphthoic acid (H(2)NA) ligands, {[Ln(2)(HATNA)(2)(HNA)(2)(H2O)(4)].6DMF} (Ln = Dy (1), Tb (2), Sm (3), Eu (4); DMF = N,N-dimethylformamide) have been prepared and characterized by X-ray diffraction crystallography, dc/ac magnetic characterization, and fluorescent spectrometry. The crystallographic data reveal dinuclear lanthanide cores of complexes 1-4, bridged by phenoxo and mu(1,3) carboxyl groups. Each nine-coordinated Ln(III) ion is located in a slightly distorted monocapped square antiprism. The ligand of H(3)ATNA displays a unique antenna effect in complex 4. Complexes 1-3 display only two ligand-centered fluorescent emissive peaks around 450 and 600 nm, and complex 4 shows four characteristic Eu(III)centered emission bands at 593, 618, 653, and 698 nm under excitation at 348 nm. Complex 1 exhibits single-molecule magnet behavior that is rationalized through ab initio calculations.