Lanthanide mononuclear complexes with a tridentate Schiff base ligand: Structures, spectroscopies and properties

Abstract

A series of six lanthanide mononuclear complexes with a julolidine-quinoline based tridentate Schiff base ligand have been synthesized and structurally characterized. The complexes [NdL2(CH3OH)(NO3)]·CH3OH (1) and [LnL2(NO3)] [Ln = Eu (2), Gd (3), Dy (4), Ho (5), Lu (6)] {HL (C22H21N3O) = ((E)-9-((quinolin-8-ylimino)methyl)-1,2,3,5,6,7-hexahydropyrido[3,2,1-ij]quinolin-8-ol)} all have mononuclear structures with a metal to ligand ratio of 1:2. The Ln(III) ions are nine-fold coordinated by two tridentate Schiff base ligands and a bidentate nitrate anion except for complex 1 in which Nd(III) ion is ten-fold coordinated with an additional MeOH molecule. The coordination of a bidentate nitrate anion makes chirality to the complexes with equal enantiomers presence in the solid state. Lanthanide contraction has been observed with the average Ln–O/Ln–N bond lengths decreasing along the lanthanide series. Vibrational modes (2–5), electronic structures (1–3), thermal stability (2) and magnetic properties (3) have been further investigated and reported.