Novel tris-buffer based Schiff base bearing long flexible alkoxy arm and its lanthanide complexes: Mesomorphism and photoluminescence

Abstract

A new liquid crystalline salicylaldimine Schiff base having pendant hydroxymethyl (CH2OH) groups and a series of lanthanide(III) complexes of the type, [Ln(LH)3(NO3)3] {Ln = La, Pr, Sm, Gd, Tb; LH=(E)-2-((1, 3-dihydroxy-2-(hydroxyl methyl) propan- 2-ylimino)methyl)-5-(hexadecyloxy) phenol} have been synthesised. The compounds were characterised by FT-IR, 1H NMR, 13C NMR, UV–Vis, and FAB-mass spectroscopy. Thermal behaviour of these compounds was studied using polarising optical microscopy (POM) and differential scanning calorimetry. The phase confirmation and molecular organization in the mesophase was ascertained by variable temperature powder X-ray diffraction (XRD) study. The ligand and the complexes both showed highly viscous smecticA and columnar mesophase, respectively. A bilayer self organization of the ligand molecules with interdigitation of the alkyl chains in the mesophase is proposed. Molecular organizations of the complexes in the mesophase involve arrangement of all the aliphatic chain pointing in same direction leading to lamellar columnar phase. The ligand showed an intense blue emission at 452 nm while the gadolinium(III) complex exhibited an intense emission at 458 nm (λex = 310 nm). The samarium(III) complex is a bright orange light emitter over a wide range upon UV irradiation.