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Reversible covalent and noncovalent interactions in solution, porous and polymeric based media

Michael David Greaves, University of Massachusetts Amherst


To replicate functionality and isolation provided by enzyme active sites, flavin was covalently incorporated into a silicate sol-gel. The isolation provided by the sol-gel cybotactic region replicates the sequestered nature of an enzyme active site. To establish specific hydrogen bond mediated recognition of the flavin within the sol-gel matrix, flavin incorporated gels were co-functionalized with a diacyl diaminopyridine based receptor. Host-guest interactions were established via quenching of the flavin fluorophore by the receptor. To continue this active site model, an aromatic unit was incorporated into flavin sol-gels. π-stacking interactions serve to modulate flavin cofactor reactivities within the active site. To quantify the individual effect of π-stacking on the flavin nucleus, fluorescence spectroscopy was used as a spectroscopic probe. Solvochromic flavin responds to changes in solvent polarity in its microenvironment and this is registered with either a hypsochromic (blue, lowering of polarity) or bathochromic (red, increase in polarity) shift of the second absorption (π, π*) in its UV/vis spectrum. Red or blue shifts correspond to the ability of solvent molecules to re-orientate themselves around the excited isoalloxazine nucleus, maximizing solvation interactions. Surface structure and performance of sol-gels and “MCM” type materials are closely linked. Current spectroscopic probes have proved limited and so the solvochromic and amphiphilic properties of flavin were utilized as a noninvasive probe of silica based materials. Quinones are found in a wide variety of biological processes often involving an accompanying proton transfer mechanism, culminating in the formation of the reduced QH2 species. Thiourea based receptors can form a hydrogen bond mediated chelate complex with the radical anion of ubiquinone. Proton transfer to the ubiquinone radical anion via this specific form of recognition was probed. Cyclic voltammetry (CV) and simultaneous electrochemistry electron paramagnetic resonance (SEEPR) studies were used to investigate this process. One way in which the characteristic properties Buckminsterfullerenes (C60) can be further investigated is via immobilization of C 60 onto a physical support. The ability of C60 to undergo thermoreversible Diels-Alder type cycloaddition reactions was exploited in order to immobilize the fullerene on a diene-functionalized polymeric support.

Subject Area

Organic chemistry|Chemistry|Chemistry|Polymers

Recommended Citation

Greaves, Michael David, "Reversible covalent and noncovalent interactions in solution, porous and polymeric based media" (1999). Doctoral Dissertations Available from Proquest. AAI9920605.