The Application Of C=O…π Interaction And Methyl Cinnamate In Low-molecular-mass Organic Gelators

In recent years there has been immense interest in studying gels derived from low molecular mass gelators. The motivation for this is not only to understand the fundamental aggregate structures in the gels at different length scales, but also to explore their potential for futuristic technological applications. Gels have been made sensitive to external stimuli like light and chemical entities by incorporating a spectroscopically active or a receptor unit as part of the gelator molecule. This makes them suitable for applications such as sensing and actuating. The diversity of gel structural architectures has allowed them to be utilized as templates to prepare novel inorganic superstructures for possible applications in catalysis and separation.Gels derived from LMOGs with rigid functional moieties, forming organogel networks via π-π stacking, are promising for applications in optoelectronic devices, template synthesis, and biomimetic systems. In general, most gelators form long carbon chains or steroidal groups, which balance their solubility and crystallization, but might be unimportant concerning the functionality of the organogel. Therefore, a strategy to design rigid gelators without long carbon chains or steroidal groups would be more economical regarding material quantities required. Until recently, only a few such rigid LMOGs have been reported.The C=O…π interaction and methyl cinnamate group have been previously observed as documented by Addadi and Lahav in 1979. And this non-classical interaction model of C=O…π and methyl cinnamate group have not been exploited as a routine tool in the design and construction of supramolecular structures. Therefore, to utilize this interaction and functional group, which can be used for provide promising points to build supramolecular structures, conceptually extends the molecular design scope to include rigid LMOGs. The thesis consists of two parts as following:Part I Triphenylamine-Based Fluorescent Soft Matter: Interlaced Methyl Cinnamate Groups as the Dominant Interaction Tools for Gel FormationNovel low-molecular-weight organic gelators(LMOGs) with propeller-shaped triphenylamine as a “core” and tiny methyl acrylate groups as “tails” are developed. The sensitive gel-sol transformation can be easily achieved upon heating or cooling accompanied by molecular aggregation or disaggregation. H-H 2D NOESY is employed to prove that the cooperative π-π stacking and C=O…π interactions between the interlaced tiny “tails” and the interaction between the superimposed phenyl and carbonyl groups of adjacent molecules are the dominant interaction forces. At present, tris(4-methyl cinnamate)amine synthesized by a single step, with a gel-formation ability and an aggregation-induced fluorescence emission property.Part II Methyl Cinnamate-derived Fluorescent Rigid OrganogelsA new class of rigid low-molecular-mass organic gelators(LMOGs) was synthesized by McMurry and Heck reactions. The LMOGs lacked alkyl chain and H-bonding units, and produced good gelation ability in selected mixed organic solvents facilitated by cooperative π-π stacking and C=O…π interactions. Sensitive gel-sol transformation by molecular aggregation and disaggregation was easily achieved upon heating and cooling.