Induced Nematic Phase of New Synthesized Laterally Fluorinated Azo/Ester Derivatives.

Fowzia S Alamro,Hoda A Ahmed,Mohamed A El-Atawy,Salma A Al-Zahrani,Alaa Z Omar

doi:10.3390/molecules26154546

Abstract

A new series of laterally fluorinated mesomorphic compounds, namely 2-fluoro-4-((4-(alkyloxy)phenyl)diazenyl)phenyl 4-substitutedbenzoate (Inx) were prepared and evaluated for their mesophase behavior. The synthesized series constitutes five members that possess different terminally attached polar groups (X). Their molecular structures were confirmed by elemental analyses and both FT-IR and NMR spectroscopy. Examination of the prepared derivatives was conducted via experimental and theoretical tools. Mesomorphic investigations were carried by polarized optical microscopy (POM) and differential scanning calorimetry (DSC). DSC and POM measurements indicated that except for the un-substituted analogue, all other derivatives were purely nematogenic, possessing their nematic (N) mesophase enantiotropically. This is to say that insertions of terminal polar substituents on their mesogenic structures induced the N phase. In addition, the location of lateral and terminal polar moieties played a considerable role in achieving good thermal N stability. Computational calculations were investigated to determine the deduced optimized molecular structures. Theoretical data indicated that both size and polarity of the terminal substituent (X) have essential impact on the thermal parameters and optical properties of possible geometries.

Highlights

The thermal stability of azobenzenes and the possibility for their molecular-mobility in response to light and heat make them suitable for many photonic applications [1–6]
All the compounds of the homologous series are enantiotropic, exhibiting mesophase thermal stability and mesomorphic temperature range depending on their terminal group X, except for the un-substituted derivatives (I8c and I16c) which show non-mesomorphic behaviors
By increasing the length of the terminal chain to n = 16 (I16d), the N phase stability was slightly reduced to 220.2 ◦C and the nematogenic temperature range became 103.3 ◦C

Summary

Introduction

The thermal stability of azobenzenes and the possibility for their molecular-mobility in response to light and heat make them suitable for many photonic applications [1–6]. In the case of the unsubstituted homologues All the compounds of the homologous series are enantiotropic, exhibiting mesophase thermal stability and mesomorphic temperature range depending on their terminal group X, except for the un-substituted derivatives (I8c and I16c) which show non-mesomorphic behaviors.

Results

Conclusion