Degree Granting Department
Li-June Ming, Ph.D.
Catechol oxidase, Heterogeneous catalysis, Hydroxylation, Metallopolymers, Reactive oxygen species, Tyrosinase
The goal of this study is to utilize polymers as macromolecular ligands for the construction of catalysts by formation of coordination complexes with transition metals with the main focus on complexes of Cu(II) and Fe(III) and further determine (a) their catalytic efficiency (b) mechanism of action (c) similarities to enzymatic systems and synthetic metal complexes. The reactions of interest are (1) hydrolytic cleavage of a series of phosphoesters(2) oxidation of catechol type of substrates (3) hydroxylation of phenolic substrates and chlorinated phenols (4) activation of molecular oxygen and/ or hydrogen peroxide (5)oxidative cleavage of DNA plasmid.
The major premise of the study is that by mimicking the macromolecular nature and some structural features of enzymes, polymers can in principle, catalyze chemical transformations with similar efficiencies and specificities and can offer alternatives to peptide based catalysts or simple metal complexes with the advantage of a wider range of building blocks, increased stability and the potential of reusability. The crosslinked resins used contained the functional groups iminodiacetate (chelex resin), diethylenetriamine and tris(2-aminomethylamine) and were based on styrene-divinylbenzene backbone. The catalytic proficiencies of the Fe(III) and the Cu(II) complexes of chelex resin and diethylenetriamine approached 100 and 1000 respectively towards the model phosphodiester BNPP at pH 8.0 and 25Â°C.
Moreover, the Fe(III) complexes of linear copolymers with repeating unit of three vinylpyridines to one acrylamide (P1) showed selectivity towards phosphodiester hydrolysis over monoesters and phosphonate esters and exhibited catalytic proficiencies approaching 50,000 towards BNPP hydrolysis. Further exploration of the catalytic capabilities of copolymer P1 revealed that Cu(II) complexes of this macromolecular ligand are potentially capable of assembling to active dicopper intermediates found in the catalytic pathways of copper oxygenases like tyrosinase and catechol oxidase and thus were able to accelerate catechol oxidation to ortho-quinones with rate accelerations approaching 10,000 and hydroxylate phenols with rate accelerations close to one million.
The results suggest that these Cu(II)-polymer systems can potentially be used as model systems to further understand metal centered reactive oxygen species (ROS) generated in vivo and can be very promising remediation agents for the dechlorination of persistant chlorine containing pollutants.
Scholar Commons Citation
Lykourinou, Vasiliki, "Copper and iron complexes of linear and crosslinked polymers as catalysts for phosphoester hydrolysis and oxidative transformation of phenolic and catecholic substrates" (2006). Graduate Theses and Dissertations.