Eight homodinuclear lanthanide complexes prepared from a quinoline based ligand: structural diversity and single-molecule magnetism behaviour

Eight dinuclear lanthanide complexes of compositions [Pr 2 L 2 (NO 3 ) 4 (H 2 O)]·EtOH ( 1 ), [Nd 2 L 2 (NO 3 ) 4 (CH 3 CN)]·CH 3 CN ( 2 ), [Sm 2 L 2 (NO 3 ) 4 (CH 3 CN)]·CH 3 CN ( 3 ), [Eu 2 L 2 (NO 3 ) 4 (H 2 O)] ( 4 ), [Tb 2 L 2 (NO 3 ) 4 ] ( 5 ), [Dy 2 L 2 (NO 3 ) 4 ] ( 6 ), [Ho 2 L 2 (NO 3 ) 4 ] ( 7 ) and [Er 2 L 2 (NO 3 ) 4 ] ( 8 ) (HL = 2-{[(2-hydroxy-3-methoxybenzyl)imino]methyl}quinoline-2-formaldehyde) have been synthesized by reactions of Ln(NO 3 ) 3 ·6H 2 O with a tetradentate quinoline-based Schiff base ligand (HL) in MeCN/EtOH/NEt 3 solution. The structures of 1–8 are characterized by X-ray single crystal diffraction analysis. They exhibit four distinct structures. In complex 1 , two Pr III atoms are triply bridged by three oxygen atoms, including an unusual water bridge. Complexes 2 and 3 are isostructural, in which two metal centres are nine- and ten-coordinated, respectively. There are two characteristic Eu III ions in 4 , which are eight- and ten-coordinated, respectively. In the isomorphous compounds 5–8 , the two Ln III atoms in the centrosymmetric molecules are doubly bridged by phenolate oxygen atoms and both metal ions possess nine-coordinate environments. Dc magnetic susceptibility studies in the 2–300 K range were performed for compounds 6 and 7 . Antiferromagnetic interactions were determined for these two complexes. Complex 6 shows slow magnetic relaxation behaviour with an energy barrier ( U eff / K B ) of 14.3 K.