Rod shaped oxovanadium(IV) Schiff base complexes: Synthesis, mesomorphism and influence of flexible alkoxy chain lengths

• A series of oxovanadium(IV) complexes of bidentate [N,O] donor Schiff-base ligands have been synthesized.
• The ligands and complexes are all thermally stable exhibiting smectic mesomorphism.
• The ligands show SmC and an unidentified SmX phase reminiscent of soft crystal.
• Oxovanadium complexes mostly showed SmA phase.
• Interestingly, the complexes with C10 and C12 alkoxy chain length exhibited additionally SmC phase also.

A series of oxovanadium(IV) complexes of bidentate [N,O] donor Schiff-base ligands of the type [VO(L)2], [L = N-(4-n-alkoxysalicylaldimine)-4′-octadecyloxyaniline, n = 8, 10, 12, 14, 16 and 18] have been synthesized. The compounds were characterized by elemental analyses, Fourier transform infrared spectroscopy (FTIR), 1H, 13C nuclear magnetic resonance (NMR), ultraviolet–visible spectroscopy (UV–Vis), and fast atom bombardment (FAB) mass spectrometry. The mesomorphic behavior of the compounds was studied by polarized optical microscopy (POM) and differential scanning calorimetry (DSC). The ligands and complexes are all thermally stable exhibiting smectic mesomorphism. The ligands 8-OR to16-OR show SmC phase at ∼113–118 °C and an unidentified SmX phase reminiscent of soft crystal at ∼77–91 °C whereas the complexes all showed SmA phases. Interestingly the complexes with C10 and C12 alkoxy chain length exhibited additionally SmC phases also. The melting points of the ligands linearly increases whereas mesophase to isotropic transition temperature decreases as a function of increasing carbon chain length of alkoxy arm while no trend was apparently noticeable for the complexes.

A series of oxovanadium(IV) complexes of bidentate [N,O] donor rod shaped Schiff base ligands containing flexible alkoxy arms on either side of the aromatic rings have been successfully synthesized. Of particular interest is that the ligands showed striated textures (SmX) reminiscent of soft crystal not observed in the case of complexes. The complexes with carbon chain length (C10, C12) interestingly showed SmC mesophase in addition to SmA phase.Figure optionsDownload as PowerPoint slide