Unusual Electron Transfer Rate Effects due to Pyridyl Ring Substituents and Trace Group VIII b Hexacyano Complexes as Added Salts

<p>The rates of pseudo-self-exchange electron transfer reactions between [(NH₃)₅Ru^IIL]²⁺ and [(NH₃)₅Ru^IIIL’]³⁺ at reactant concentrations of 1.0 х 10^-4 M (where L, L’ = substituted pyridines) and the reaction between [(NH₃)₅Ru^IIPy]²⁺ and [(NH₃)₅Ru^III3FPy]²⁺ at different reactant concentrations in the presence of various salts added were studied by using the stopped-flow kinetic spectroscopy. Marcus theory rate <em>vs</em>. driving force plots yielded distinct families of lines depending on whether a 3- or 4- phenylpyridine ligand was present, and reactions of 4-phenylpyridine were in all cases the fastest. Both temperature dependent studies (stopped-flow and dynamic NMR measurements) indicate that the origin of the phenyl substituent effect is in the enthalpic portion of the free-energy of activation. One explanation is that the reorganizational barrier λ might be significantly lower for the 3-Phpy and 4-Phpy complexes, or it could be that energetically-favorable p-p stacking interactions (known to be common in compounds bearing the phenyl rings) may be helping to enhance bimolecular precursor complex formation.</p> <p>Salt effect studies showed that the apparent catalytic activity of the salts muconate, terephthalate and 1,4-DCCH decreased modestly as the reactant ion concentrations were increased. In agreement with prior NMR work (Yinshin,Q.;2011) we found that the superexchange ET catalysis by trace M^II(CN)₆^-4 varied strongly in the order Ru < Os < Fe</p>

Name thesis:degree_name

Master of Science (MS)

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Chemistry

Year dc:date.available

2011

Author dc:creator

• Mehmood, Faisal

Contributors dc:contributor

• Dr. Jeff C. Curtis
• Dr. Larry Margerum
• Dr. William Melaugh

• ET
• Kinetics
• Rate Constant
• Physical Sciences and Mathematics

Repository record dc:identifier

https://repository.usfca.edu/thes/1

OAI identifier oai:identifier

oai:repository.usfca.edu:thes-1000