New wide-stability four-ring azo/ester/Schiff base liquid crystals: synthesis, mesomorphic, photophysical, and DFT approaches

Abstract

New four-groups-based azo/ester/Schiff base liquid crystals, ((4-substitutedphenylimino)methyl)phenyl 4-[2-(4-alkoxyhenyl)diazenyl]benzoate, In a-d , were synthesized and analyzed for their mesomorphic stability and optical activity. In these compounds, a terminal alkoxy group of variable chain length from n ¼ 6 to n ¼ 16 carbons is attached to the end of a phenylazo benzoate moiety and the other end of the molecules is connected to a different polar compact substituent X (CH 3 O, CH 3 , H, and Cl). FT-IR, 1 H NMR, mass spectroscopy and elemental analysis were carried out for molecular structure confirmation of the prepared compounds. The mesomorphic properties were confirmed using a combination of differential scanning calorimetry (DSC) and polarized light microscopy (PLM). The photophysical property was studied by UV-vis spectroscopy. All the prepared homologous series exhibited high thermal stability with a wide-temperature mesomorphic range. The thermal and geometrical parameters of the investigated compounds were estimated by density functional theory (DFT). The results revealed that all the compounds were not completely planar with a relatively high twisting moiety at the CH]N part and their twist angles were affected by the electronic nature of the attached X group. Moreover, the calculated quantum chemical parameters as determined by the DFT approach of the investigated compounds were related to the experimentally determined values of the mesophase thermal stability (T c ) and mesophase temperature ranges (DT SmA and DT N ) as well as the type of the mesophase.Scheme 1 Synthesis of (4-substituted phenylimino)methyl)phenyl 4-[2-(4-alkoxyphenyl)diazenyl]benzoate, In a-d .This journal is

Binary Liquid Crystal Mixtures Based on Schiff Base Derivatives with Oriented Lateral Substituents

“…Liquid crystalline materials are classified into three distinct types: polymeric, lyotropic, and thermotropic. Thermotropic liquid crystals have been widely studied and used for their linear and nonlinear optical properties [2,[6][7][8][9][10][11][12][13][14][15][16][17][18]. Usually, this type of liquid crystal is represented as rigid rods, which can interact with one another and form characteristic ordered structures.…”

Induced Phases of New H-bonded Supramolecular Liquid Crystal Complexes; Mesomorphic and Geometrical Estimation

“…Most of the SMHLCs studied are based on the rod-like intermolecular H-bonding [10,[12][13][14][29][30][31] and there is a lot of interest towards the formation of angular supramolecular hydrogen-bonded liquid crystals [9]. On the other hand, the Schiff base and azo moiety are of special interest due to their ability for trans/cis isomerization upon UV light irradiations [7,[32][33][34][35]. In their supramolecular Schiff base/azo -based LCs, via H-bonding interactions, the rigid core is lengthened, and thus induces the mesomorphic behavior that may not occur in the individual components [11,36].…”

Thermal and Photophysical Studies of Binary Mixtures of Liquid Crystal with Different Geometrical Mesogens

“…The development and investigation of new advanced functional thermotropic liquid crystals require the proper selection of a mesogenic core, linking group, and terminal functional substituents. [48] The photochromic phenomena for such spacers (-N=N, -N=CH-, and -COO-) are used to control the mesophase behavior and optical activities of several LCs [42,44,46,47,[49][50][51][52][53][54][55][56][57][58]. The reversible trans-cis isomerization, induced by thermal and ultraviolet irradiation, brings about a molecular ordering in the trans isomer that stabilizes the mesophase structure of the LC, while the disordering of cis isomers will destroy the mesophase formation.…”