The influence of molecular flexibility on the mesogenic behavior of a new homologous series based on azo-azomethine: Synthesis, characterization, photoisomerization and DFT study

Through condensation of 2-hydroxy-4-n-alkoxybenzaldehyde (n = 2 to 8, 10, 12, 14, 16, 18) with (E)-4-((2,4-dimethylphenyl)diazenyl) benzene-1,3-diamine, new homologous series of rod shaped calamite liquid crystals based on azo-azomethine have been prepared. All synthesized compounds were characterized by FT-IR, H-1 NMR, and C-13 NMR spectroscopy. Use Differential Scanning Calorimeter (DSC) and Polarizing Optical Microscope (POM) to check the liquid crystal properties of all synthetic compounds. In the homologous series, all the compounds are mesogenic; some of them are in the nematic phase; some of them appear in the smectic A phase, and some appear in the nematic and smectic A phases. UV-vis pectroscopy was used to study the photoisomerization in chloroform. DFT (Density functional theory) level calculations and complete geometric optimization of all synthetic compounds are performed using B3LYP/6-31+G (d, p) basis sets. (C) 2021 Elsevier B.V. All rights reserved.