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Heterometallic Complexes as Models of Enzymatic Active Sites

Citation

Lionetti, Davide (2016) Heterometallic Complexes as Models of Enzymatic Active Sites. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/Z98G8HMT. http://resolver.caltech.edu/CaltechTHESIS:09282015-080838463

Abstract

This dissertation describes studies on two multinucleating ligand architectures: the first scaffold was designed to support tricopper complexes, while the second platform was developed to support tri- and tetrametallic clusters.

In Chapter 2, the synthesis of yttrium (and lanthanide) complexes supported by a tripodal ligand framework designed to bind three copper centers in close proximity is described. Tricopper complexes were shown to react with dioxygen in a 1:1 [Cu3]/O2 stoichiometry to form intermediates in which the O–O bond was fully cleaved, as characterized via UV-Vis spectroscopy and determination of the reaction stoichiometry. Pre-arrangement of the three Cu centers was pivotal to cooperative O2 activation, as mono-copper complexes reacted differently with dioxgyen. The reactivity of the observed intermediates was studied with various substrates (reductants, O-atom acceptors, H-atom donors, Brønsted acids) to determine their properties. In Chapter 3, the reactivity of the same yttrium-tricopper complex with nitric oxide was explored. Reductive coupling to form a trans-hyponitrite complex (characterized by X-ray crystallography) was observed via cooperative reactivity by an yttrium and a copper center on two distinct tetrametallic units. The hyponitrite complex was observed to release nitrous oxide upon treatment with a Brønsted acid, supporting its viability as an intermediate in nitric oxide reduction to nitrous oxide.

In Chapter 4, a different multinucleating ligand scaffold was employed to synthesize heterometallic triiron clusters containing one oxide and one hydroxide bridges. The effects of the redox-inactive, Lewis acidic heterometals on redox potential was studied by cyclic voltammetry, unveiling a linear correlation between redox potential and heterometal Lewis acidity. Further studies on these complexes showed that the Lewis acidity of the redox-inactive metals also affected the oxygen-atom transfer reactivity of these clusters. Comparisons of this reactivity with manganese systems, collaborative efforts to reassign the structures of related manganese oxo-hydroxo clusters, and synthetic attempts to access related dioxo clusters are also described.

In Appendix A, ongoing efforts to synthesize new clusters supported by the same multinucleating ligand platform are described. Studies of novel approaches towards ligand exchange in tetrametallic clusters and incorporation of new supporting and bridging ligand motifs in trinuclear complexes are presented.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Heterometallic Complexes; Dioxygen Activation; Nitric Oxide Activation; Metal Clusters;
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Chemistry
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Agapie, Theodor
Group:Resnick Sustainability Institute
Thesis Committee:
  • Bercaw, John E. (chair)
  • Gray, Harry B.
  • Dougherty, Dennis A.
  • Agapie, Theodor
Defense Date:3 September 2015
Record Number:CaltechTHESIS:09282015-080838463
Persistent URL:http://resolver.caltech.edu/CaltechTHESIS:09282015-080838463
DOI:10.7907/Z98G8HMT
Related URLs:
URLURL TypeDescription
http://doi.org/10.1039/C2SC21758ADOIArticle adapted for chapter 2
http://doi.org/10.1021/ja4104974DOIArticle adapted for chapter 4
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:9179
Collection:CaltechTHESIS
Deposited By: Davide Lionetti
Deposited On:08 Oct 2015 16:47
Last Modified:26 Aug 2016 15:38

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