Synthesis and Spectral Studies of Some Homo Dinuclear Lanthanide(III) Complexes of a Mesogenic Schiff Base

Abstract

A mesogenic Schiff base, N,N’-di(4-decyloxysalicylidene)-1’,8’-diamino-3’,6’-dioxaoctane (H₂L) and a series of homo dinuclear lanthanide(III) complexes of the type [Ln₂(LH₂)₃(NO₃)₄](NO₃)₂, (Ln = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, and Ho) were synthesized and characterized by elemental analysis, mass spectrometry, FTIR, and NMR spectral techniques. The IR and NMR spectral evidences imply bonding of a neutral bidentate H₂L species through two phenolate oxygen atoms in its zwitterionic form to Ln^III, rendering the overall geometry of the complexes as a seven-coordinate polyhedron – possibly distorted mono-capped octahedron. Differential scanning calorimetry (DSC) and polarizing optical microscopic (POM) studies reveal mesogenic properties (smectic-X, smectic-A and nematic mesophases) in the ligand over a wide range of temperature but none mesomorphism in the Ln^III complexes synthesized under this study. Luminescence studies exhibit emissions of H₂L and Tb^III complex.