Synthesis, characterization and mesomorphic properties of new pyridine derivatives

Abstract

Luminescent liquid crystals (LC) are fascinating materials and have received significant, scientific and technological interest due to their wide range of applications. Among various LC materials, heterocyclic mesogens gain much interest. This is attributed to the ability of heterocycles to impart lateral and/or longitudinal dipoles combined with their favorable molecular shape. Also, their presence helps for exhibiting good photophysical properties. At present, there is a considerable attention among the researchers to develop new heterocyclic systems showing both liquid crystalline and luminescent properties. In this context, it was contemplated to design, synthesize and to investigate the liquid crystalline as well as optical properties of new pyridine derivatives. Based on the literature survey, new pyridine derivatives (LC1-48) were designed as possible liquid crystalline materials. They were later successfully synthesized following the appropriate synthetic routes. Further, their synthetic methods as well as purification techniques were established and their yields were optimized. Further, their structures were confirmed by various spectral techniques such as FTIR, 1H NMR, 13CNMR spectral, single crystal followed by elemental analyses. Finally, the target compounds were characterized for their mesogenic, optical and optoelectronic properties. The liquid crystalline study on new pyridine derivatives indicated that the compounds LC1, LC14 and LC20-25 were shown to exhibit nematic phase at high temperature and LC2-13, LC15-19, LC26-32 and LC34-48 were shown to display columnar phase at ambient or higher temperature. Similarly, their optical study revealed that the compounds showed a strong absorption band in the range of 330-370 nm in solution state and a strong blue emission band in the range of 390-480 nm both in solution as well as in film state. The optoelectronic study of LC38 evidenced its suitability in device applications. To sum up, suitably substituted new pyridine derivatives appeared as active templates for future development of new liquid crystalline materials.