Investigations into the formation of [4] cavitand derived hosts that encapsulate multiple guest molecules

The main goals of the thesis work is to investigate the formation and applications of a class of host-guest molecules known as carceplexes and hemicarceplexes. Carceplexes are large, globe-shaped molecules that permanently entrap smaller guest molecules within their inner confines. Hemicarceplexes are similar to carceplexes, but differ in that hemicarceplexes possess larger pores though which guest egress is possible with sufficient heating. Template effects in the formation carceplexes/hemicarceplexes were examined. One study involves investigations into the role of single-molecule guests as templates in the formation of the "two-bowl" hemicarceplex 25‧guest. A second study investigates the role of single and multiple-molecule guests as templates in the formation of a larger "three-bowl" carceplex 56‧guests. Complexation of various guests that were determined to be suitable templates to transition state models were also examined to help elucidate the driving forces in the formation of 56‧guests. Restricted conformational and orientational mobility of several incarcerated guests, as well as the reversible of complexation of water to 56‧guests are described. The application of carceplex 56‧guests in the generation and stabilization of the simple enol, acetophenone enol (139), as a guest in 56 was also studied. Enol 139 was successfully generated and is remarkably stable as an incarcerated guest in the absence of water, even at high temperatures. Ketonization of the entrapped enol is facilitated by water, and the observed rate of reaction is significantly slower than for the free enol 139 in solution. The mechanism of ketonization of the entrapped enol 139 is also reported. A new "six-bowl" carceplex, which entraps seven DMSO guest molecules (149‧(DMSO)₇) was also synthesized and characterized. Dynamic behavior for both the host shell and its entrapped DMSO guests was observed in organic solutions by ¹H NMR spectroscopy.Science, Faculty ofChemistry, Department ofGraduat

Self-Assembly of Alkylamido Isophthalic Acids toward the Design of a Supergelator: Phase-Selective Gelation and Dye Adsorption

A new series of 5-alkylamido isophthalic acid (ISA) derivatives with varying single and twin alkyl chain lengths were designed and synthesized as potential supramolecular organogelators. 5-alkylamido ISAs with linear or branched alkyl tail-groups of different lengths were effective gelators for low polarity solvents. In particular, among the presented series, a derivative with a branched, 24 carbon atom tail-group behaves as a “supergelator” with up to twenty organic solvents forming gels that are highly stable over time. The gelation behavior was analyzed using Hansen solubility parameters, and the thermal stability and viscoelastic properties of select gels were characterized. Microscopy, spectroscopy, powder X-ray diffraction, and computer modeling studies were consistent with a hierarchical self-assembly process involving the formation of cyclic H-bonded hexamers via the ISA carboxylic acid groups, which stack into elementary fibers stabilized by H-bonding of the amide linker groups and π–π stacking of the aromatic groups. These new nanomaterials exhibited potential for the phase-selective gelation of oil from oil–water mixtures and dye uptake from contaminated water. The work expands upon the design and synthesis of supramolecular self-assembled nanomaterials and their application in water purification/remediation