Complexes of some rare earth metal ions of the mesogenic Schiff-base, N,N′-di-(4′-octyloxybenzoatesalicylidene)-l″,8″-diamino-3″,6″-dioxaoctane: Synthesis and spectral studies

A mesogenic Schiff-base, N,N′-di-(4′-octyloxybenzoatesalicylidene)-l″,8″-diamino-3″,6″-dioxaoctane; H2dobsdd (H2L3), that nematogenic mesophase was synthesized and its structure studied by elemental analysis and FAB mass, NMR and IR spectra. The Schiff-base, H2L3, upon condensation with hydrated lanthanide(III) nitrates, yields LnIII complexes of the general composition [Ln2(L3H2)3(NO3)4](NO3)2, where Ln = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy and Ho. The IR and NMR spectral data imply a bi-dentate of the Schiff-base through two phenolate oxygens in its zwitterionic form (as L3H2) to the LnIII ions, rendering the overall geometry of the complexes to seven-coordinated polyhedron — possibly distorted mono-capped octahedron. Among the metal complexes, only that of LaIII and GdIII are found to be mesogenic.