Eight new rod-like liquid crystal molecules composed by a long rigid core of three six-member rings (cyclohexane ring or benzene ring), azo, ester and terminal aldehyde groups have been prepared. These rod-like liquid crystalline molecules were designed to construct new structures to further study photo-isomerization in their mesophases. All the compounds have been characterized based on their basic spectral data, differential scanning calorimeter (DSC) and hot stage polarizing optical microscope (HS-POM). The result showed that all the molecules, even those with the shortest terminal methyl group, have liquid crystalline properties. Their mesophases are nematic within the temperature ranges from 85 to 145°C. They exhibit photo-sensitivities not only in methanol solutions but also in a mesophase when exposed to UV light. The highest occupied orbital (HOMO) and the lowest unoccupied orbital (LUMO) and the differences between the frontier molecular orbitals (Eg) of these compounds were determined by cyclic voltammetry. The effect of even-odd carbon number of the terminal straight alkyl chain on the UV spectral data and the Eg were observed. The difference between the Eg of these compounds are in excellent agreement with the difference of their maximum absorption wavelength in UV spectra.
Financed by the National Centre for Research and Development under grant No. SP/I/1/77065/10 by the strategic scientific research and experimental development program:
SYNAT - “Interdisciplinary System for Interactive Scientific and Scientific-Technical Information”.