Research Vignettes

Overview of the Evolution of Hosts for Paraquats and Diquats in the Gibson Group

In earlier work we showed that in some cases the pseudorotaxane complexes are not ion paired, while the guest salts are ion paired. This complicates analysis, because formally two equilibrium constants must be determined, that for ion pair dissociation and binding of the free cation by the host. The accompanying slides show on the basis of X-ray crystal structures that the nature of the complex is not predictable.

High association constants, K, are required for efficient self-assembly processes. In particular we are interested in self-assembly of supramolecular polymers; to reach true poymeric status a degree of polymerization, n, of 100 is required. A graph of an equation derived from the Carothers' equation shows that for high values of the association constant n = sqrt[(conc)(K)]. In order to increase K values for complexation with paraquats and diquats and provide readily accessible hosts, a series of cryptands have been made, resulting in readily prepared hosts with high binding constants that meet our goals.

Development of Functionalization Reactions for Trimetallic Nitride Templated Endohedral Metallofullerenes.

In a collaborative effort with Prof. Harry Dorn's group we explore the chemistry of these rather new "buckyballs" in order to make them soluble in appropriate media, either aqueous or organic, and provide them with attachment sites for further elaboration or incorporation into dendrimers and polymers. One of our efforts was to utilize the lower reactivity of the TNT EMFs vs. C60 and C70 and other empty-cage congners using polymer beads bearing cyclopentadienyl pendant groups; the empty-cage fullerenes are bound via Diels-Alder cycloaddition to the beads and the less reactive TNT EMFs pass through. Some of the reactions we have developed for the TNT EMFs are the Prato azomethine ylid cycloaddition, free radical additions of active methylene compounds, photochemically activated free radical reactions and diazo cycloadditions.

Ionic Liquids, Their Interactions with Polymers and Polyelectrolytes Containing Ionic Liquid-Like Moieties

In collaboration with Prof. Tim Long and others as part of an Army-supported MURI project, we are examining novel ionic polymers for applications in electroactive devices like actuators. As time goes on we will post some vignettes in this space relating to these efforts.

Reissert Compounds, an Interest that Began in 1962!

Although we have no funding in this area now and thus no students are active, Prof. Gibson continues to work in this area. In the past our group has studied the suitability of these useful compounds in stereoselective syntheses of alkaloids. Specifically, as summarized in the accompanying slide show, we examined incoprporation of chiral auxilliaries in the form of the N-acyl group and studied the stereochemistry of reactions of the Reissert anions with alkyl halides and aldehydes.