Coumarin Derivatives And Their Supramolecular Interactions

Liquid crystal materials are one kind of soft materials, and important in our information age. Generally, the studies in liquid crystal materials include:development and application of liquid crystal for LCD, and preparation and properties of functional liquid crystal based on hydrogen bonding or supermolecular interaction. For functional liquid crystal materials, heterocyclic liquid crystals have attracted more and more attentions because the incorporation of heteroatoms (N, O and S, commonly introduced) can result in considerable changes in the corresponding mesophases due to their much larger polarity than carbon. Many kinds of heterocyclic liquid crystals, such as pydine-based, pyrimidine-based. pyrazine-based and oxadiazole-based liquid crystals, have been reported. In particular, coumarin derivatives were also studied as mesogenic units based on their strong dipole moments. Herein, two kinds of coumarin derivatives, bezopyrano[2,3-c] pyrazol-3-one and coumarin-3-acylhydrazine. were designed. The corresponding thirteen novel heterocyclic liquid crystals,7-alkoxybezopyrano[2.3-c] pyrazol-3-one and 7-alkoxy coumarin-3-acylhydrazine, were prepared, where a one pot synthesis method under microwave was developed. The self-assembly of the obtained compounds was investigated.The research includes the following parts:1. Eight novel fused polyheterocyclic aromatic compounds ALBPP-n, were designed and prepared with overall yields of 13-23%. ALBPP-n was synthesized through three-step reactions, namely Knoevenagel condensation, nucleophilic substitution followed by the hydrazinolysis cyclocondensation, and was purified with column chromatography with HPLC purities more than 99%. The structures were confirmed by FTIR,'H-NMR,13C-NMR and 2D 1H-13C cosy spectra. Their phase transition behavior was investigated by differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). All of these compounds showed enantiotropic mesophases with temperature domains of 12-60℃and 22-69℃on heating and cooling processes for carbon number of alkoxy chain from 2 to 10. The melting temperature points of ALBPP-n decreased smoothly with ascending the homologues. The nematic-isotropic liquid or the SmA-isotropic liquid transitions temperature points exhibited the same decreasing tendency, as well as a clear odd-even effect with the increase of the carbon numbers (n). Moreover, the dimmer formed by the intermolecular hydrogen bonding interaction elongated and constructed a new mesogenic unit to achieve and stabilize the liquid crystal phase. 2. Five novel ALCAH-n compounds were designed and prepared with HPLC purities more than 98% and overall yields of 15-33%.7-Alkoxy coumarin-3-acylhydrazine (ALCAH-n) was prepared by hydrazinolysis reaction between ethyl 7-alkoxycoumarin-3-carboxylate and hydrazine hydrate in absolute ethanol, where ethyl 7-alkoxycoumarin-3-carboxylate was prepared by a nucleophilic substitution reaction between bromoalkanes and 7-hydroxycoumarin-3-carboxylate obtained from Knoevenagel condensation reaction of 2,4-dihydroxybenzaldehyde with diethyl malonate. The structures were confirmed by FTIR and 1H-NMR spectra. Their phase transition behavior was investigated by DSC and POM. All of these compounds showed enantiotropic mesophases composed of multi-smectic phase transition except ALCAH-18. The melting and clearing temperature points of ALCAH-n increased smoothly with ascending the homologues. Furthermore, ALCAH-n was able to self-assemble into ordered aggregates in a number of organic liquids and finally gelatinize the liquids, where the gelation ability of ALCAH-n increased with ascending the homologues. The hydrogen bonding was considered as the main driving forces for the formation of self-assembly for ALCAH-n.3. A simplified one-pot microwave synthesis of bezopyrano[2.3-c] pyrazol-3-one derivative was developed based on the selected probe object of ALBPP-2. where three steps, including Knoevenagel condensation, nucleophilic substitution and hydrazinolysis cyclocondensation, were continuously performed under microwave irradiation without separation and purification till the last step except feeding in each step. The present procedure was performed within 50 min with overall yield of 13%. Although a slightly lower yield was obtained for the one-pot synthesis than that of the common method, it was useful for the simplified synthesis of the derivatives.