The Study On Intermolecular Interactions Of Hydrazide Derivatives

Self-assembled systems of molecules through hydrogen bond, π-π interaction,etc, such as molecular gel, have evoked people’s interest and attention. It is a kind ofsoft materials with nano structure and can respond to external stimuli such astemperature, electrical pulses, light and chemicals. Studies have shown that the gelproperties are related to molecular structure, stacking geometry and solvent properties.Therefore, understanding the stacking geometry of oxalyl acidN,N’-dibenzoyl-hydrazide derivatives and the function of solvent in the self-assemblyof molecules can provide important information for the preparation of a new gel andits application.1. the stacking geometries and association thermodynamics of oxalyl acidN,N’-dibenzoyl-hydrazide derivativesThe noncovalent stacked associations of the three oxalyl acidN,N’-dibenzoyl-hydrazide derivatives which are effective gelators in some organicsolvents and have different numbers of the terminal alkoxyl chains on the aromaticrings were investigated in chloroform solvent at various temperatures by NMRspectroscopy. The intermolecular interaction is governed by hydrogen bondingbetween the carbonyl oxygen atoms of one molecule and the hydrogen atoms of imineof the partner molecules and п-п interaction between neighbor aromatic moieties,however, the types of hydrogen bonding and configurations of aromatic moieties aredifferent in three derivatives in the temperature studied. The average aggregation number was estimated by1H and DOSY NMR with concentration and the stackinggeometries were built based on both the magnitudes of peak shifts with concentrationand the directions of peak shifts induced by polar solvents. The association constantsobtained by fitting the dilution curves and thermodynamic parameters obtained fromvan’t Hoff analyses revealed different thermodynamic processes of aggregations forthree samples in the temperature region of343-298K.2. The gelation of N, N’-Bis (4-N-Alkylo-Xybenzoyl) Hydrazine (4Dn) in twoaromatic solventsWe found that thermal gel properties of the N, N’-Bis (4-N-Alkylo-Xybenzoyl)Hydrazine (4D16) is correlated with the Kamlet-Taft parameter and gain a detailedunderstanding of solvent role on gelation. Benzene and toluene are similar of aromaticsolvents, but the varieties of physical characteristics of the4D16gels formed fromthese two solvents are large. We studied noncovalent force, association constant, andthermodynamic parameters of4D16aggregation process in these two aromaticsolvents by NMR and explained why gelator4D16in toluene had a lower criticalgelation concentration (CGC). We select4D7which has higher CGCs and itsmicrostructures are similar to4D16in these two solvents to compare differences ofsolvents and find that gelator-solvent interaction can break up toluene oligomers,whereas this interaction does not disrupt benzene oligomers. The motion of gelator isrestricted due to the defect size provided by the vicinity of the methyl groups intoluene oligomers, thus it is favorable for gelator-gelator interaction.