Syntheses, Characterization, and X-ray Crystal Structure of Binuclear Lanthanide Complexes Assembled with Schiff Base and Acetate

Herein we reported the binuclear complexes of the 1-(pyridin-2-yl)-2-(pyridin-2-ylmethylene)hydrazine ligand (HL) [Ln2(HL)2(CH3COO)6].n(H2O) (Ln = Y, Pr, Gd and Er). The binuclear complexes are characterized by IR and physical measurement. Spectroscopic evidence indicated that the Schiff base HL behave an N3 coordination tridentate ligand. The complexes are formulated as [{Ln(1-(pyridin-2-ylmethylidene-kN)-2-(pyridin-2-yl-kN)hydrazine-kN1)(h2-OOCH3)2}{h1:h2:m2-OOCH3}2{Ln(1-(pyridin-2-ylmethylidene-kN)-2-(pyridin-2-yl-kN)hydrazine-kN1))(h2-OOCH3)2}].n(H2O). The structure of the praseodymium complex was elucidated by X-ray diffraction analysis. Suitable crystals were grown by slow evaporation of methanol solution. The asymmetric unit of the compound contains two neutral ligand molecules, two Pr3+ ions, four acetate anions acting in h2-OOCH3 mode, two acetate anions acting in h1:h2:m2-OOCH3 mode, and three uncoordinated water molecules. The praseodymium atom is ten coordinated and the coordination sphere is best described as a distorted bicapped square antiprism. The PrIII···PrIII distance is 4.2777(6) Å and the bridging angle Pr—O—Pr and O—Pr—O are respectively 115.8(3)° and 64.2(3)°. The structure is consolidated by intra and intermolecular hydrogen bond.