UVM Theses and Dissertations
Format:
Print
Author:
Morris, James Chadwick
Dept./Program:
Chemistry
Year:
2007
Degree:
PhD
Abstract:
The synthesis of oxidatively robust Iigand for the use in oxidation catalyst is a growing field as chemists seek more turnovers and "green" techniques for their synthetic schemes. Here we present a discussion of the novel cyclic amides for the use as oxidatively robust Iigands. We are using cyclic triamides with amido type Iigands to increase the electron density of non-toxic transition metals, that can stabilize higher valence states on the metal center. The discussion includes the use of the oxmalone and benzoxazinone moities for synthesis of tripeptides, and the first crystalIographicaly proven structures of all a trans cyclic tripeptide.
The solid state structures of our cyclic peptides are discussed in relationship to the formation of extended hydrogen bonded networks. The distortion from planarity of the amide bond is discussed with in the context of allowing the intermolecular hydrogen bonding, and how amide non-planarity may affect the bonding to metal centers. Taking the view that any compound with avalable electrons can act as a Iigand; we discuss the use of paramagnetic metal centers bound to non-metalIoproteins as paramagnetic nuclear magnetic resonance (NMR) probes Proteins that do not normally have metal centers can be viewed as a large multidentate Iigand. This view and the historical use of isomorphous replacements lead us to believe that small paramagnetic ions can be used as site specific NMR probes. Unlike traditional paramagnetic probes, Gd(lII), our systems are able to bind in the active site of the proteins. This unusual property has allowed us to perturb the proton NMR resonances near the active site. This can allow us to assign the residues in the active site, and help in the prediction of the solution state structure of the protein.
Siderophores are very similar in shape to synthetic Iigands. Here we discuss the use of pyridinedithiocarboxylid acid (PDTC), a secondary siderophores isolated from Pseudomonas stuzeri, as a Iigand for the reductive dechlorination of carbon tetrachloride. The CuPDTC systems are able to reductively dechlorinate carbon tetrachloride forming C0₂. A mechanistic study of the this system suggests that the first step in this mechanism is most likely a inner sphereoneelectron oxidative addition to form copper(lII). Evidence in support of this mechanism is presented.
The solid state structures of our cyclic peptides are discussed in relationship to the formation of extended hydrogen bonded networks. The distortion from planarity of the amide bond is discussed with in the context of allowing the intermolecular hydrogen bonding, and how amide non-planarity may affect the bonding to metal centers. Taking the view that any compound with avalable electrons can act as a Iigand; we discuss the use of paramagnetic metal centers bound to non-metalIoproteins as paramagnetic nuclear magnetic resonance (NMR) probes Proteins that do not normally have metal centers can be viewed as a large multidentate Iigand. This view and the historical use of isomorphous replacements lead us to believe that small paramagnetic ions can be used as site specific NMR probes. Unlike traditional paramagnetic probes, Gd(lII), our systems are able to bind in the active site of the proteins. This unusual property has allowed us to perturb the proton NMR resonances near the active site. This can allow us to assign the residues in the active site, and help in the prediction of the solution state structure of the protein.
Siderophores are very similar in shape to synthetic Iigands. Here we discuss the use of pyridinedithiocarboxylid acid (PDTC), a secondary siderophores isolated from Pseudomonas stuzeri, as a Iigand for the reductive dechlorination of carbon tetrachloride. The CuPDTC systems are able to reductively dechlorinate carbon tetrachloride forming C0₂. A mechanistic study of the this system suggests that the first step in this mechanism is most likely a inner sphereoneelectron oxidative addition to form copper(lII). Evidence in support of this mechanism is presented.