Generation of mono-mesophase in allylidene-based homologues with a longer molecular axis

Abstract

In this article, we have synthesized twenty-eight nematogenic homologous derivatives of allylidene base with cinnamates and benzoates linkages. All nematogenic homologous derivatives were characterized by ultraviolet spectroscopy, Infrared and proton magnetic resonance with study of their mesophase properties by the polarized optical microscope (POM) where they were found to be enantiotropically nematogenic. The thermograms of mesophase transition enthalpies and entropies were recorded by differential scanning calorimetry (DSC). The geometries of all molecules were optimized by DFT/B3LYP method using a basis set def2-SVP, the result of these calculated molecule's geometries for all molecules showed to have an electron-rich longer molecular axis, which enables the molecule to form a stronger pi interaction with adjacent molecules and induces the nematogenic mesophase behavior. The effect of an additional diene system on mesophase behavior of a stepped type of molecules was also studied. The role of the number of rings on mesophase behavior as an odd-even effect on mesophase transition temperature as well as the role of the substitution on the terminal ring for the same was considered.