Unsymmetrical mesogenic dimers containing azo and azomethine naphthalenes: Synthesis, characterization, mesomorphic properties and DFT studies

Abstract

The synthesis and properties of two new mesogenic homologous series comprising of sixteen unsymmetrical dimers of cyanoazobenzene and azo/azomethine naphthalene are described. Their right structure was confirmed by FT-IR, 1HNMR , 13CNMR , and elemental analysis. On the polarising optical microscope (POM), their thermotropic properties were examined and further confirmed using differential scanning calorimetry (DSC). All sixteen dimers exhibit an enantiotropic nematic phase. The relationship between the nematic-isotropic transition temperature and the structures of dimers was discussed. A view of their photochromic behaviour was gained by UV–visible spectroscopy. The 6–31 g (d, p) basis set is combined with the B3LYP functional, which is used for computational studies of all the dimers. The examination of Electrostatic Potential (ESP) and optical characteristics also yielded important information about the electronic structure.