Theoretical and experimental studies on optically tunable hydrogen bonded liquid crystal complex derived from mesogenic and non-mesogenic aromatic compound

Abstract

A novel hydrogen bonded liquid crystal (HBLC) complex is synthesized from non-mesogenic benzylmalonic acid (BMA) and mesogenic 4-nonyloxybenzoic acid (9OBA). Structural properties and optimized vibrational frequencies of BMA + 9OBA have been studied by FT-IR spectrum. The weak intermolecular interaction between the molecules is proved by NBO and Mulliken charge distribution analysis. The optical and thermal properties are investigated by POM, DSC, UV-Visible and PL techniques. The present HBLC complex exhibits schlieren textures of nematic, broken focal conic texture of smectic C and multicolored mosaic texture of smectic G phases respectively which is not observed in the pure mesogen (9OBA). The HBLC complex geometry is optimized by DFT method at the level of B3LYP basis set 6311G (d, p). The electronic properties of HBLC complex such as, NBO, HOMO-LUMO, ESP and Mulliken charge distribution are also studied. A noteworthy observation is brought out by identifying the presence of photoluminescence in nematic phase due to the variation in intermolecular interaction of the mesophase. The utility of the same complex is discussed. The phase width, thermal stability factor, tilt angle, phase transition temperature and its enthalpy values are reported.

Keywords:

• DFT
• DSC
• FT-IR
• HBLC complex
• HOMO-LUMO
• POM

Acknowledgements

One of the authors (V N Vijayakumar) acknowledge the financial support rendered by the Department of Science and Technology (No.SERB/F/7454/2013-2014 dated 21.02.2014), New Delhi and Department of Atomic Energy (No: 34/14/14/2016-BRNS/34039 dated 22/04/2016) Board of Research in Nuclear Science (DAE-BRNS), TNSCST/YSFS/VR/01/2016-2017/1094/Dtd:12.04.2017 and infrastructural support provided by Bannari Amman Institute of Technology, Sathyamangalam.