Spectroscopic Studies On The Structure And Properties Of Hydrogen-Bonded Supramolecular Systems

Hydrogen-bonding is a vital weak interaction between molecules in theprocess of molecular reorganization and the system of self-assembly, and itplays an important role in the fields of materials and biology. In manysupramolecular liquid crystal materials based on hydrogen-bonding, usually,the precursor itself has no character of Liquid Crystal. The special propertiesare formed from the process of self-assembly or self-organization. Both thesupramolecular assemblies of azopyridine/acid and a series of novelhydrazide based azobenzene derivatives display the strong relationship offunction and structure: in the first one, the supramolecular systems have thedifferent types of hydrogen-bonding with different strength whenconstructed by very similar precursor; in the second systems, differentmacroscopic properties have been induced by the length of alkyl chains inprecursor. Where are these different functions come from on earth? Whatkinds of hydrogen-bonding modes have been formed in the assemblies, andinduced the supramolecular assemblies having different functionalproperties. These problems need to be solved in the present study.Based on the above problems, our studies will be focused in thefollowing fields.1. Two-dimensionalcorrelation IR spectroscopic studies of hydrogen-bonded supramolecular assemblies between azaaromaticmolecules with dicarboxylic acidInfrared (IR) spectra have been measured for a supramolecularassembly based on intermolecular hydrogen bonding between sebacic acid(SEA) molecule as a proton donor and azopyridine (AZP) molecules as aproton acceptor ([SEA·AZP]) over a temperature range from 29 ℃to 155℃to explore the involved hydrogen-bonding species and heat-inducedstructural variations. The temperature-dependent IR spectra have shown thatthe intermolecular hydrogen bonding are stable enough in thesupramolecular assembly but it become slightly decoupled whentemperature is higher than its clearing point. 2D correlation spectra in1780-1660 cm-1 regions have provided information about the structuralvariations of intermolecular hydrogen bonding concerning with C=O group.While, 2D correlation spectra in 880-820 cm-1 regions have revealedhydrogen bonding changes concerning with proton in the adjacent positionof pyridyl ring. Three different hydrogen-bonded species in thesupramolecular assembly have been clarified by the 2D correlation analysis.The specific order of the temperature-induced structural changes in theinvolved intermolecular hydrogen-bonded species in supramolecularassembly has also been elucidated in the present study.2. Two-dimensional correlation IR spectroscopic studies of a series ofhydrazide based on azobenzene derivativesClassification of hydrogen bonding species in a series of novelhydrazidemodifiedp-methoxyazobenzenederivatives,4-{n-[4-(4-methoxy-phenylazo)-phenoxy]-alkoxy}-benzoic acid hydrazide(p-Dn,n=3,6,10)areperformedinthepresentstudy.Temperature-dependent Infrared (IR) spectra of p-Dn have been measuredto investigate the thermal stability of the weak intermolecular interactionssuch as hydrogen bonding among hydrazide moieties, π-πstacking amongaromatic groups, and hydrophobic interaction between alkyl chains. In orderto reveal the hydrogen bonding formed between -NH-, -NH2 and -CONH-groups efficiently, Two-dimensional (2D) correlation spectra have beenconstructed in the thermal sensitive spectral regions of (a) 3500-3100 cm-1and (b) 1700-1450 cm-1, separately, and it have also been constructedbetween these two spectral regions.3. Molecular modeling studies on a series of hydrazide based onazobenzene derivatives...