Synthesis, Characterization and study Mesomorphic properties of a new Imidazole and Benzoimidazole derivatives

Abstract

In this thesis, four series of novel heterocyclic imidazole and benzoimidazole based liquid crystals are successfully synthesized and characterized. The synthesis of these liquid crystalline compounds involved alkylation 1a-1i, esterification reactions 2a-2i and Schiff-base reactions. The first series of novel derivatives imidazole dimers 8a-8i,9a-9i, and 10a-10i have been synthesized by incorporated reaction of imidazole ring with 4-((4-(((4- (bromoalkyloxy)benzylidene)amino)methyl)benyl)imino)methyl)phenyl-4(alky loxy)benzoate 5a-5i,6a-6i, and 7a-7i (compounds 5a-5i,6a-6i, and 7a-7i was synthesized by the reaction between 4-(((4(aminomethyl)benzyl)imino)methyl) phenyl(alkyloxy)benzoate 3a-3i and 4-(4-bromobutoxy) benzaldehyde 4a-4c) and terminal chains in odd or even parity. In the second series, a series of new derivatives of imidazole dimers 24a-24i, 25a-25i, and 26a-26i, have been synthesized from the reactions of derivatives imidazole with 4-(4-(4-(((4-(4-bromobutoxy)phenyl)imino)methyl)phenoxy)buto xy)phenyl4-(alkyloxy) benzoate 21a-21i,22a-22i,and 23a-23i (compounds 21a 21i,22a-22i, and 23 a-23i) was synthesized by the reaction between compounds 4- (4-(4-(((4-(4-bromobutoxy)phenyl)imino)methyl)phenoxy)butoxy)phenyl4-(alky yloxy)benzoate 18a-18i ,19a-19i, and 20a- 20i with 4-((n-(4-formyl-phenoxy) alkyl)oxy)phenyl 4-(alkyloxy) benzoate 15a-15i,16a16i, and 17a-17i. The third and fourth series[11a-11i,12a-12i, 13a-13i], [27a-27,28a-28i, and 29a 29i] incorporated benzoimidazole ring which where synthesized by compounds [5a 5i,6a-6i, and 7a-7i], [21a-21i,22a-22i, and 23a-23i] respectively, with derivatives benzoimidazole, terminal chains in odd or even parity. CHN Microanalysis, FT-IR, 1H-NMR and 13CNMR spectroscopic methods were used to elucidate the structures of these compounds. The liquid crystal properties are studied by conducted several methods such as DSC and POM, the transition temperatures of the synthesized compounds and respective enthalpy values are determined by differential scanning calorimetry (DSC) whilst a polarized optical microscope (POM) is used for texture observation. Shown their anisotropy properties III Scheme I: compounds synthesis steps for first series obtained N phase in some compounds. The compounds 8c, 9a, 10f, 13c, 26c, 27f, and 29b shown anisotropic properties of LC and N phase. The schemes below show the steps of compounds synthesis in all series.