Abstract
New four isomeric chair architectures of 1:1 H-bonded supramolecular complexes were prepared through intermolecular interactions between 4-(2-(pyridin-4-yl)diazenyl-(2-(or 3-)chlorophenyl) 4-alkoxybenzoates and 4-n-alkoxybenzoic acids. The H-bond formation of all complexes was confirmed by differential scanning calorimetry (DSC) and Fourier-transform infrared spectroscopy (FTIR). Mesomorphic characterization was carried by DSC and polarized optical microscopy (POM). It was found that, all prepared laterally choro substituted supramolecular complexes were nematogenic exhibited pure nematic phase and low melting temperature. The thermal stability of the nematic mesophase observed depends upon the location and spatial orientation of the lateral Cl- atom in as well as the length of terminal chains. A comparison between the new investigated 1:1 mixtures and previously reported laterally CH3 as well as the laterally neat complexes revealed that, the position/orientation and polarity of incorporated lateral group into the azopyridine component enhance the entropy changes and affect on the type and stability of the mesophase. The density functional theory (DFT) theoretical calculations were discussed to predict the molecular conformation for the formed complexes as well as their thermal parameters. The results of the computational calculations revealed that the H-bonded complexes were in a chair form molecular geometry. Moreover, the results explained the effect the position and orientation of the lateral group as well as the alkoxy chain length on the type and the stability of the nematic mesophase. In addition, their impacts on the estimated thermal parameters of H-bonded complex and how these play an important role in influencing thermal and optical properties.
Highlights
Supramolecular liquid crystals (SMLCs) have an exponentially attraction in attention of scientific researches[1,2,3,4,5]
The H-bonding between the nitrogen of azopyridines and the carboxylic group of alkoxybenzoic acid of the supramolecular complexes An/Im and An/IIm replaces the bis H-bonds of the dimeric form of the alkoxybenzoic acid
Four new isomeric series of 1:1 SMHB complexes in chair-shaped liquid crystalline were constructed based on laterally Cl azopyridine derivatives and 4-alkoxybenzoic acids
Summary
Supramolecular liquid crystals (SMLCs) have an exponentially attraction in attention of scientific researches[1,2,3,4,5]. Azopyridines have been used in the formation of nano fiber supramolecular self-assembling and hydrogen/halogen-bonding LCs with photo induced transition phenomena.[25,26,27,28,29]Designing of photosensitive SMLCs through intermolecular interactions using the suitable H-bond donors and acceptors are concerns of our area of interest. [30,31,32,33,34,35,36]Anisotropic structures are produced from the overall molecular shape of architectures and the combination of rigid (aromatic) and flexible segments (alkyl chains) Those changes in the characteristics of the LCs may be impact the mesomorphism as well as the properties essential for technical uses. Density functional theory (DFT) becomes effective popular method for its excellent performance and consistent with the experimental results. [18, 40, 47, 48]
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