Infrared Spectroscopic Study of Liquid Crystalline N-[4-(4-n-alkoxybenzoyloxy)-2-hydroxybenzylidene]-3-cyanoanilines

Abstract

A homologous series of N-[4-(4-n-alkoxybenzoyloxy)-2-hydroxybenzylidene]-3-cyanoanilines [AHC(n; n = 1–8, 10, 12)] was synthesized. AHC(4–8, 10) exhibit a monotropic nematic phase. The temperature dependence of infrared (IR) spectra of AHC(4–8) has been observed in the spectral range of 2300–600cm⁻¹. On cooling, the intensity of the IR band at 2230cm⁻¹ remained unchanged through the phase-transition of isotropic-nematic and increased gradually toward room temperature (solid phase). This band can be assigned to the C ≡ N stretching vibrational mode. The wavenumber of the band increased slightly (about 1 cm⁻¹) during the temperature from isotropic to solid. In mela-CN substituted AHC, it is suggested that the CN group may not play a dominant role in the intermolecular interaction.

Key Words:

• Nematic
• salicylidene aniline derivative
• 3-cyano anilines
• infrared spectroscopy
• molecular conformation