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Iridium corroles : synthesis, properties, and electronic structure

Citation

Palmer, Joshua Henry (2011) Iridium corroles : synthesis, properties, and electronic structure. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechTHESIS:02152011-145456588

Abstract

The synthesis, properties, and electronic structures of a family of iridium corrole complexes are discussed in detail. These compounds represent the first well-characterized examples of third-row metals being inserted successfully into the small corrole binding pocket; they possess a planar macrocycle, which neither saddles nor ruffles upon bromination, and are bound at the axial positions by either two amine ligands or one phosphine. Unlike their well-studied cobalt and rhodium analogues, whose redox activity is restricted primarily to the corrole ring, iridium corroles can be oxidized to produce an electron paramagnetic resonance spectrum that has extremely anisotropic g tensor components, implying mixing of the 5d orbitals into the oxidized ground state and opening the door to possible higher-valent iridium complexes. Detailed experimental and computational studies are presented showing that this oxidized ground state is actually mostly corrole-based, as has been found in the past for numerous other supposedly high-valent corrole compounds, but the percentage of iridium character varies from 10 to 18% and tracks with the electron-donating ability of the ligand. Additionally, the unique (among corrole complexes) near-IR phosphorescence of Ir(III) corroles is presented and discussed. Iridium(III) corroles phosphoresce with lifetimes ranging from hundreds of nanoseconds to a few microseconds at room temperature, with slightly longer lifetimes at low temperature. Unfortunately, the quantum yields of phosphorescence are low, 1% or less, and this appears to be due to an exceptionally slow set of radiative rates for the corroles. An examination of the reactivity of ammine-ligated Ir(III) corroles is also described. These compounds can be oxidized in the presence of an ammonia source to form novel six-coordinate iridium(III) azaporphyrins in an unprecedented chemical transformation. The characterization and properties of these iridium azaporphyrin complexes are detailed as well, with a focus on nuclear magnetic resonance characterization techniques and a discussion of the red phosphorescence of the azaporphyrins.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:corrole; porphyrinoid; iridium; porphyrin; iridium corrole; epr; dft; spin-orbit coupling; electronic structure; azaporphyrin; monoazaporphyrin
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Chemistry
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Gray, Harry B.
Thesis Committee:
  • Bercaw, John E. (chair)
  • Peters, Jonas C.
  • Stoltz, Brian M.
  • Gray, Harry B.
Defense Date:11 February 2011
Author Email:joshuap (AT) caltech.edu
Funders:
Funding AgencyGrant Number
NSF Center for Chemical InnovationCHE-0802907
NSF Center for Chemical InnovationCHE-0947829
US-Israel BSFUNSPECIFIED
BPUNSPECIFIED
CCSER (Gordon and Betty Moore Foundation)UNSPECIFIED
Arnold and Mabel Beckman FoundationUNSPECIFIED
Overseas Research Fellowship Scheme U. of Hong KongUNSPECIFIED
Record Number:CaltechTHESIS:02152011-145456588
Persistent URL:http://resolver.caltech.edu/CaltechTHESIS:02152011-145456588
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:6243
Collection:CaltechTHESIS
Deposited By: Joshua Palmer
Deposited On:29 Mar 2011 16:32
Last Modified:25 Apr 2013 17:29

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