Mesophase Behavior of Molecules Containing Three Benzene Rings Connected via Imines and Ester Linkages

Ten new compounds based on the methineazo-azomethine (CH=N-N=CH) and ester linking groups were prepared and investigated for their mesophase behavior and optical stability, and liquid crystals of 4-substituted phenyl methineazo-azomethine phenyl 4-alkoxybenzoates, I n , were investigated. An alkoxy group with a length between 8 and 12 carbons is attached to the phenyl eater wing, while the other terminal ring is substituted in its 4-position with one of the polar NO₂, F, Cl, CH₃O, and N(CH₃)₂ groups. The molecular structures of the newly prepared compounds were verified by using ¹H NMR, ¹³C NMR, and elemental analysis. Differential scanning calorimetry and polarized optical microscopy were applied to investigate their mesophase behavior. All members of the prepared homologous series showed excellent thermal mesomorphic stability over wide temperature ranges. The geometrical and thermal properties of the investigated compounds were verified via density functional theory (DFT). The theoretical results revealed that all of the compounds are almost planar. Finally, the experimentally established values of the mesophase data were correlated with the predicted quantum chemical characteristics evaluated by DFT.