Rare Earth Metal Complexes of a Mesogenic Schiff-Base, N,N′-di-(4-decyloxysalicylidene)-1′, 4′-diaminobutane: Synthesis and Characterization

Abstract

A mesogenic Schiff-base, N,N′-di-(4-decyloxysalicylidene)-1′,4′-diaminobutane, (H₂L) that exhibits smectic-B and nematic mesophases, was synthesized and its structure studied by elemental analysis, mass spectrometry, NMR & IR techniques. H₂L, upon condensation with hydrated lanthanide(III) nitrates yields Ln^III complexes of the composition [Ln₂(LH₂)₃(NO₃)₄](NO₃)₂, where Ln^III = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, and Ho. The Pr^III complex shows smectic-A and nematic phases. The IR and NMR spectral data imply a bidentate bonding of H₂L in zwitterionic form (as LH₂) to the Ln^III ions through two phenolate oxygen atoms, rendering the overall geometry of the complexes possibly to distorted mono-capped octahedra.

Keywords:

• Ln^III complexes
• mesogenic schiff-base
• mono-capped octahedron
• NMR and IR spectra
• zwitterionic coordination

Acknowledgments

The authors wish to acknowledge the recording of FAB Mass spectra at the Central Drug Research Institute, Lucknow, India. The financial assistance received from the CSIR, New Delhi (vide Sanction letter No. 01(2321)/09/EMR-II) and the fellowship awarded to Mr. P. R. Shakya by the University Grants Commission, Kathmandu, Nepal, are gratefully acknowledged.