Synthesis of Heterocyclic Pyridine-Based Chalcones with Dimeric Structure

Three new heterocyclic chalcones containing pyridine moiety were synthesized and their chemical structures were determined via IR, 1H NMR and 13C NMR spectroscopy. General name of these compounds are α,ω-bis{3-(pyridin-3-yl)-1-(phenyl-4-oxy)prop-2-en-1-one}alkanes. The chalcones are dimers having a symmetrical structure and they can be differed by the alkyl spacer length (CnH2n, where n = 8, 10 or 12). Differential scanning calorimetry (DSC) technique was employed to study their phase transition behaviors. DSC thermograms displayed direct isotropization and recrystallization during heating and cooling processes, respectively. The crystal phase turned into isotropic phase without exhibiting any mesophase. Influence of structure-liquid crystalline property relationships of the symmetrical dimers was examined in order to explain the reasons for the non-liquid crystalline properties in the current chalcones.