Abstract
A new set of laterally OCH3-substituted photoactive liquid crystalline analogues, 4-hexyloxy phenyl- imino-4ʹ-(3-methoxyphenyl)-4ʹ’-alkoxybenzoates, were synthesized and investigated for their mesomorphic behavior. The prepared set constitutes five analogues that differ from each other by the terminally attached compact polar group. Characterization of the synthesized derivatives is conducted using differential scanning calorimetry (DSC), polarized optical microscopy (POM), and UV-spectroscopy. Molecular structures were elucidated by elemental analyses, FT-IR and NMR spectroscopy. DSC and POM investigations indicated that all the prepared derivatives are monomorphic possessing the nematic (N) phase, except for the unsubstituted derivative that is nonmesomorphic. On the other side, the photophysical study and the optical spectra measurements confirm the photoactivity of the present compounds under UV/visible irradiation. The measured optical spectra showed impressive enhancement in the optical absorption and reduction in the optical bandgap from 3.63 to 3.0 eV depending on the terminal group. From the study of the DC electric properties, the lowest resistance, 106.5 GΩ at scan rate 0.1 V/s, was observed for the I6d film with Cl terminal, which decreased to 49.5 GΩ by increasing the scan rate to 0.5 V/s. Moreover, the electrical conductance is decreased from 9.39 pS to 1.35 pS at scan rate 0.1 V/s by changing the terminal group from Cl to F. The enhanced optical absorption and the reduced energy gap make the optimized samples suitable material for solar energy applications.
Highlights
Nowadays, liquid crystalline (LC) compounds prove to have several applications as optical materials—areas of technological applications such as displays, light-emitting diodes based on organic derivatives, anisotropic networks, and semi- and photoconductors materials [1,2,3]
Schiff base and hydrazone derivatives are well known as valuable intermediates in synthesis of many organic compounds that exhibit many applications [39,40,41,42,43,44,45,46]
Molecular structures of products I6a–e were elucidated via their spectroscopic data αFT IR, 1 H-NMR and 13 C-NMR, see Supplementary Data) and elemental analyses
Summary
Liquid crystalline (LC) compounds prove to have several applications as optical materials—areas of technological applications such as displays, light-emitting diodes based on organic derivatives, anisotropic networks, and semi- and photoconductors materials [1,2,3]. Based on Schiff base/ester central linkages, sets of terminal substituted derivatives were synthesized and investigated for their mesomorphic properties; in addition, the effect of the terminal long and compact group polarities on the mesophase were studied [9,10,11,12,13,14,15,16]. Further aim of the study is to investigate the mesophase and photo-physical behaviors as well as the effect of the change of the polar terminal substituents on the mesomorphic properties of synthesized compounds.
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