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Intramolecular electron transfer in an iridium d [supercript 8]-d [superscript 8] donor-acceptor system


Fox, Lucius Seiberling (1989) Intramolecular electron transfer in an iridium d [supercript 8]-d [superscript 8] donor-acceptor system. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/hapm-b986.


NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. A series of donor-acceptor complexes, [...] 2,4,6-trimethylpyridinium, 4-methylpyridinium, pyridinium, and 4-phenylpyridinium; [...], have been synthesized for studying the rate of photoinduced electron transfer from the metal localized [...] excited states of [...] chromophores. The pyridinium electron acceptors are covalently attached to the iridium metal centers (donor) via a three atom hydrocarbon linker bound to the terminal phosphine ligands. The x-ray crystallographic structure of [...] reveals a metal-metal distance of 3.219(1) [...] and a solid state donor-acceptor separation of 5.34(1) [...]. Additional donor-acceptor separations and orientations are available to the compounds in fluid solution through rotations about the Ir-P and linker group C-O, C- N, and C-C bonds. Steady state emission spectra show that the fluoresence and phosphoresence quantum yields in these compounds are substantially reduced relative to a appropriate model complex. To date the excited state reactivity of [...] metal dimers has been exclusively attributed to their [...] states. These findings represent the first evidence for reactivity from a shorter lived [...] state. Picosecond and nanosecond laser flash-photolysis techniques were employed to measure the rates of photoinduced electron transfer and charge recombination in these systems. Values of [...], obtained from these studies, vary between [...] and [...] as a function of reaction exoergicity [...]. Clear evidence for the inverted behavior predicted by classical and semiclassical electron transfer models is seen at high driving force. Rate constants for reactions involving the [...] and [...] excited states, as well as the rates of charge recombination are characterized by very similar values of [...] and [...]. Our data are adequately modeled by the classical theory of electron transfer proposed by Marcus [...] or by a semiclassical model for [...] where nuclear tunneling involves a low frequency metal-ligand mode [...]. These findings are explored with regard to utilizing the donor-acceptor complexes as molecular photochemical energy storage systems.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:chemistry
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Chemistry
Awards:The Herbert Newby McCoy Award, 1989
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Gray, Harry B.
Thesis Committee:
  • Unknown, Unknown
Defense Date:31 January 1989
Record Number:CaltechETD:etd-06072007-081509
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:2499
Deposited By: Imported from ETD-db
Deposited On:14 Jun 2007
Last Modified:16 Apr 2021 22:17

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