Influence of substituents on thermal and electronic properties of 4-((<i>E</i>)-phenyldiazenyl)-2-((<i>E</i>)-((4-(alkyloxy)phenyl)imino)methyl)phenol derivatives

The study explores the synthesis, mesogenic behavior and computational analysis of 24, 4-((<i>E</i>)-phenyldiazenyl)-2-((<i>E</i>)-((4-(alkyloxy)phenyl)imino)methyl)phenol derivatives (<b>9a–h</b>, <b>10a–h</b>, and <b>11a–h</b>). Mesogenic properties were examined using polarizing optical microscopy. Smectic phases were observed in phenyldiazenyl derivatives, while tolyldiazenyl and nitrophenyldiazenyl derivatives exhibited nematic phases with varying transition temperatures. Notably, nitrophenyldiazenyl compounds had higher transition temperatures due to strong intermolecular interactions. DFT studies revealed insights into molecular structures, HOMO–LUMO energy gaps, and electrostatic potentials, with 4-nitrophenyldiazenyl derivatives showing the smallest energy gaps and highest dipole moments. These findings highlight substituent effects on thermal properties and reactivity, aiding advanced liquid crystal design.