Induced Wide Nematic Phase by Seven-Ring Supramolecular H-Bonded Systems: Experimental and Computational Evaluation

Abstract

New seven-ring systems of dipyridine derivative liquid crystalline 2:1 supramolecular H-bonded complexes were formed between 4-n-alkoxyphenylazo benzoic acids and 4-(2-(pyridin-4-yl)diazenyl)phenyl nicotinate. Mesomorphic behaviors of the prepared complexes were investigated using a combination of differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). Fermi bands attributed to the presence of intermolecular H-bond interactions were confirmed by FT–IR spectroscopy. All prepared complexes possessed an enantiotropic nematic phase with a broad temperature nematogenic range. Phases were confirmed by miscibility with a standard nematic (N) compound. A comparison was constructed to investigate the influence of the incorporation of the azophenyl moiety on the mesomeric behavior of corresponding five-membered complexes. It was found that the present complexes observed induced a wide nematic phase with relatively higher temperature ranges than the five aromatic systems. Density functional theory (DFT) suggested the nonlinear geometry of the formed complex. The results of the DFT explained the nematic mesophase formation. Moreover, the π–π stacking of the aromatic moiety in the phenylazo acid plays an effective role in the mesomorphic thermal stability. The energy difference between the frontier molecular orbitals, HOMO (highest occupied) and LUMO (lowest occupied), and the molecular electrostatic potential (MEP) of the prepared complexes were estimated by DFT calculations. The results were used to illustrate the observed nematic phase for all H-bonded supramolecular complexes. Finally, photophysical studies were discussed which were carried out by UV spectroscopy connected to a hot stage.

Recent Progress in Azopyridine-Containing Supramolecular Assembly: From Photoresponsive Liquid Crystals to Light-Driven Devices

“…Several H-bond liquid crystals exhibit rapid photoresponses and the broad-range blue phase, showing potential applications in organic optoelectronics as sensors or optical gates. Very recently, several new types of AzPy-containing supramolecular liquid crystals with different geometries were reported, e.g., rod-like shape [33,45,46], chair/V-shape [47,48], and taper-shape [49] as well as bent-shape [49,50]. It was suggested that the chairshaped conformers were more stable than the V-shaped isomeric complexes [47].…”

Pyridine-Based Three-Ring Bent-Shape Supramolecular Hydrogen Bond-Induced Liquid Crystalline Complexes: Preparation and Density Functional Theory Investigation

“…Recently, we employed theoretical calculations to correlate experimental ones regarding liquid crystalline materials [62][63][64][65][66][67][68][69][70][71][72][73]. Thus, DFT calculations were conducted for the basis set, B3LYP 6-311g (d, p), for all the supramolecular analogous series of the complexes that were prepared with p-octyloxy benzoic acid ((I-V)C8).…”

New Rod-Like H-Bonded Assembly Systems: Mesomorphic and Geometrical Aspects

“…Recently, many researchers [5,31,[44][45][46][47][48][49][50][51][52][53][54] have reported the mesophase characteristics of new supramolecular H-bonded complexes (SMHBCs) between acids and pyridines as base one [55,56]. In order to better understand the structural effect relationship of SMHBC-based azopyridines, two groups of H-bonded complexes (1:2) based on pyridine as the H-acceptor were investigated [55,57,58]. In another study, the 1:1 SMHBCs prepared between the nitrogen atom of the azomethine derivative and 4-alkoxybenzoic acids [59] has been reported and characterized.…”