Synthesis, molecular structures and phase transition studies on benzothiazole-cored Schiff bases with their Cu(II) and Pd(II) complexes: Crystal structure of (E)-6-methoxy-2-(4-octyloxy-2-hydroxybenzylideneamino)benzothiazole

Two new homologous series of Cu(II) and Pd(II) complexes with benzothiazole-cored Schiff bases have been synthesised with the aim to study the mesomorphic and thermal properties of ligands upon formation of metal complexes. The molecular structure of title compounds were elucidated with the employment of FT-IR, 1D and 2D FT-NMR spectroscopic techniques. Mesomorphic and thermal behaviour of title compounds have been investigated by differential scanning calorimetry and polarising optical microscope. All the ligands are nematogenic but the corresponding Cu(II) and Pd(II) complexes crystallised in ordinary solid. The conformation of 6-methoxy-2-(4-octyloxy-2-hydroxy-benzylideneamino)benzothiazole was determined by single crystal X-ray diffraction analysis of which the title compound favours more stable (E)-6-methoxy-2-(4-octyloxy-2-hydroxybenzylideneamino)benzothiazole. Crystal structure of the title compound also revealed that the bond length of CN (1.303 Å) in the benzothiazole rings very close to that in the exocyclic CN linkage (1.298 Å).