Theoretical estimation of mesogenic characteristics of 4-methyl (2′-hydroxy,4′-n-hexadecyloxy) azobenzene – a nematic liquid crystal

Abstract

The compound 4-methyl (2′-hydroxy,4′-n-hexadecyloxy) azobenzene was synthesized by Prajapati and co-workers (Mol. Cryst. Liq. Cryst. 369 (2001), pp. 37–46). Subsequent experiments (D. Pal, [PhD thesis], University of Lucknow, Lucknow, India, 2007) confirmed that the compound exists in nematic phase for a small range of temperature (72°C–80°C). In the present work, optimization of molecular geometry has been carried out by employing the Gaussian 03 suit of programs without any constraint using density functional B3LYP along with 6-31G** basis set and checked for imaginary frequencies. A detailed investigation on intermolecular interaction energy at various interacting configurations has been carried out. In order to study the mesogenic characteristics of the molecule, an attempt has been made to estimate the variation of order parameter with respect to the change in temperature as well as degrees of freedom. These studies will be helpful to understanding the mesogenic character of any molecule prior to synthesis and promises future application in molecular engineering.

Keywords:

• nematic
• intermolecular interaction
• order parameter
• Gaussian 03

Acknowledgments

Pankaj Kumar Gaurav is thankful to UGC, New Delhi, for granting research fellowship under Rajeev Gandhi National Fellowship. The authors are thankful to Dr Devesh Kumar, associate professor, B.B. Ambedkar Central University, Lucknow, for helping in computations. Computational facilities provided under DST-FIST grant no. SR/FST/PSI-087/204 to the Department of Physics, D.D.U. Gorakhpur University are also gratefully acknowledged.