Pyridine Derivatives Synthesis And Properties Of Supramolecular Gel

Low-molecular-mass organic gelators (LMOGs) have attracted widespreadattention of chemists and biochemists due to their unique supramolecular structuresand potential application in the fabrication of sensors, photochemistry andelectrochemistry. In order to search for new LMOGs, we designed and synthesized Aseries of LMOGs and investigated their gelation abilities, morphologies as well asself-assembly behaviors in gel state according to the gelation ability of gelatorscontaining pyridine group controlled by pH value control. Furthermore, a rationalmechanism of the formation of organogels was proposed on base of our studies. Weobtained some creative results, which were outlined as follows:(1) We synthesised N,N′,N″-tris(4-pyridyl)trimesic amide (4-btapa) bychemical modification using4-aminopyridine to benezene-1,3,5-tricarboxylic acidand investigated the gelation ability in aqueous solvent and pH solution. Indicatingthe induced effect of water in during the formation of gel. The result of Scanningelectron microscope (SEM) shows that the4-btapa can form fibrous self-assemblyaggregates in different aqueous solvent, while4-btapa shows the cotton woolstructure at pH=3.0water-ethanol system, which is different from fibrous aggregate inpH=7.0, Suggesting that the pH can affact the gel self-assembly structure. The resultsof nuclear magnetic resonance and infrared spectroscopy revealed that the molecularhydrogen bonds of N-H···Py and aromatic π-π stacking interactions were formed in gel state and water was a part of the gel. The powder diffraction experiment showedthe type of aggregate in gel and relative ordered arrangement of amide group. Frowthe above observation and analysis of FT-IR,1H-NMR and XRD results, we cansuggest the self-assembly arrangement in gel state of N,N′,N″-tris(4-pyridyl)trimesicamide (4-btapa).(2) The gel of N,N′,N″-tris(4-pyridyl)trimesic amide (4-btapa) is very state inpH=7.0and can be used as drug carriers, so we performed the drug delivery usingsalicylic acid as drugs and studied the effect of salicylic acid on gel. The minimumgelation concentration containing salicylic acid decreases with the increase of theconcentration of salicylic acid, indicating that the salicylic acid can increase thegelation ability; While the gel-solution transition temperature increases, suggestingthat the salicylic acid can improve the thermal stability of gel. The greater ofconcentration of4-btapa, the more closely of three-dimensional structure, the smallerof release rate of salicylic acid at250C, pH=7.4and the concentration of salicylicacid of100mg/L. The acidic media is more effective than that in the alkaline orneutral media at250C, the concentration of4-btapa and salicylic acid of2.0mg/mLand100mg/L, respectively. The higher of the temperature, the greater of the releaserate of salicylic acid at pH=7.4, the concentration of4-btapa and salicylic acid of2.0mg/mL and100mg/L, respectively. The release rate in gel decreases with the increaseof concentration of salicylic acid at250C, pH=7.4and the concentration of4-btapaof2.0mg/mL.(3) We synthesized the azo pyridine using4-aminopyridine and found that thesingle azo pyridine can not form gel in water. But it can form two-componenthydrogelwith m-hydroxybenzoic acid, melamine, and m-methoxy benzoic acid,respectively. The results of Scanning electron microscopy show that the aggregatestructures of gel in water is different. The variable temperature NMR and infraredspectroscopy explore that the molecular hydrogen bonds of N-H···Py and van derWaals form are droving force during the formation of self-assembly gel. The powderXRD experiment demonstrated that the aggregate of gel was a periodic orderedstructure.