Synthesis and characterisation of new tripodal lanthanide complexes and investigation of their optical and magnetic properties

Abstract

This paper presents the synthesis of a tripodal ligand (H₃L) via the Schiff base condensation of N,N-diethylsalicylaldehyde and tris(2-aminoethyl)amine. The neutral complexes of type [EuL], [GdL] and [DyL] were synthesized and characterized by FT-IR, SEM-EDS, PXRD, single crystal X-ray diffraction, CHN analysis and high resolution ESI-MS. X-ray crystallographic studies demonstrated that the heptadentate ligand incorporating a cavity pre-organized by hydrogen bonding binds the Ln(III) ions to yield a face capped octahedral coordination geometry with three-fold symmetry. Photoluminescence studies show a typical Ln(III) absorption character for the three complexes, with [EuL] demonstrating considerably stronger lanthanide-based luminescence peaks, and a Eu(III) centered luminescence lifetime of 0.144 ± 0.01 ms. Temperature/field-dependent DC and temperature/frequency-dependent AC magnetic measurements carried out for the Dy(III) complex indicated obvious magnetic anisotropy and suggested slow relaxation behaviour with considerable quantum tunnelling of the magnetization contribution.