The electron transfer (ET) self-exchange rates on a series of complexes of (NH3)5RuII/III L2+/3+ in D2O (where L is a substituted pyridyl ligand) were investigated by dynamic NMR measurements. Significant rate enhancement was observed for the cases of L = 3-phenylpyridine and 4-phenylpridine due to possible π-π stacking between Phpy ligands. These observations matche well with recent stopped-flow work by Mehmood on a similar set of related pseudo-self exchange reactions. Kinetics of the (NH3)5RuII/III (3-trifluoromethylpyridine)2+/3+ self-exchange reactions with addition of various simple/complex salts and hexacyano salts (K4M(CN)6 with M = Fe, Os and Ru) were also studied. The halide ions showed qualitatilvely-similar behavior compared to the stopped-flow work by Sista and the same quantitative decrease in the magnitude of salt effect as reported by Inagaki. The hexacyano salts were found to have a striking effect on the ET rate with a clear trend of Fe > >Os > Ru. This could be explained as a probable “superexchange” type mechanism dominated by the “hole-transfer” pathway based on the trend between the catalytic effect and the redox potential of the particular M(CN)4- ion. Kinetic modeling data also show the strongest catalytic effect of Fe which gives a ketx/ket of 126. Temperature-dependent experiments show that the rate enhancement of hexacyano series is due to a increased enthalpic barrier and less negative entropic barrier.
","abstract_html":"<p>The electron transfer (ET) self-exchange rates on a series of complexes of (NH<sub>3</sub>)<sub>5</sub>Ru<sup>II/III </sup>L<sup>2+/3+</sup> in D<sub>2</sub>O (where L is a substituted pyridyl ligand) were investigated by dynamic NMR measurements. Significant rate enhancement was observed for the cases of L = 3-phenylpyridine and 4-phenylpridine due to possible π-π stacking between Phpy ligands. These observations matche well with recent stopped-flow work by Mehmood on a similar set of related pseudo-self exchange reactions. Kinetics of the (NH<sub>3</sub>)<sub>5</sub>Ru<sup>II/III </sup>(3-trifluoromethylpyridine)<sup>2+/3+</sup> self-exchange reactions with addition of various simple/complex salts and hexacyano salts (K<sub>4</sub>M(CN)<sub>6</sub> with M = Fe, Os and Ru) were also studied. The halide ions showed qualitatilvely-similar behavior compared to the stopped-flow work by Sista and the same quantitative decrease in the magnitude of salt effect as reported by Inagaki. The hexacyano salts were found to have a striking effect on the ET rate with a clear trend of Fe > >Os > Ru. This could be explained as a probable “superexchange” type mechanism dominated by the “hole-transfer” pathway based on the trend between the catalytic effect and the redox potential of the particular M(CN)<sup>4-</sup> ion. Kinetic modeling data also show the strongest catalytic effect of Fe which gives a k<sub>etx</sub>/k<sub>et</sub> of 126. Temperature-dependent experiments show that the rate enhancement of hexacyano series is due to a increased enthalpic barrier and less negative entropic barrier.</p>","abstract_has_math":false,"creators":["Qin, Yishun"],"institution":null,"degree_name":"Master of Science (MS)","degree_level":"Thesis","degree_discipline":"Chemistry","degree_department":null,"school":null,"contributors":["Jeff Curtis","Kim Summerhays","Larry Margerum"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2013,"date_issued":"2013-12-13T08:00:00Z","date_published":"2013-12-13T08:00:00Z","updated_at":"2026-07-24T05:42:43Z","subjects":["superexchange","pyridyl ligand substituent effects","ion pair","Inorganic Chemistry"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://repository.usfca.edu/thes/74","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Jeff Curtis","Kim Summerhays","Larry Margerum"]},{"key":"dc:creator","label":"Author","values":["Qin, Yishun"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.available","label":"Dc Date Available","values":["2013-12-16T08:00:00Z"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Chemistry"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Thesis"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Master of Science (MS)"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["superexchange","pyridyl ligand substituent effects","ion pair","Inorganic Chemistry"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://repository.usfca.edu/thes/74"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["The electron transfer (ET) self-exchange rates on a series of complexes of (NH3)5RuII/III L2+/3+ in D2O (where L is a substituted pyridyl ligand) were investigated by dynamic NMR measurements. Significant rate enhancement was observed for the cases of L = 3-phenylpyridine and 4-phenylpridine due to possible π-π stacking between Phpy ligands. These observations matche well with recent stopped-flow work by Mehmood on a similar set of related pseudo-self exchange reactions. Kinetics of the (NH3)5RuII/III (3-trifluoromethylpyridine)2+/3+ self-exchange reactions with addition of various simple/complex salts and hexacyano salts (K4M(CN)6 with M = Fe, Os and Ru) were also studied. The halide ions showed qualitatilvely-similar behavior compared to the stopped-flow work by Sista and the same quantitative decrease in the magnitude of salt effect as reported by Inagaki. The hexacyano salts were found to have a striking effect on the ET rate with a clear trend of Fe > >Os > Ru. This could be explained as a probable “superexchange” type mechanism dominated by the “hole-transfer” pathway based on the trend between the catalytic effect and the redox potential of the particular M(CN)4- ion. Kinetic modeling data also show the strongest catalytic effect of Fe which gives a ketx/ket of 126. Temperature-dependent experiments show that the rate enhancement of hexacyano series is due to a increased enthalpic barrier and less negative entropic barrier.
"]},{"key":"dc:title","label":"Title","values":["Mechanistic Studies of Bimolecular Electron Transfer Self-Exchange Rates of Ruthenium Ammine Pyridyl Complexes Measured by NMR Line Broadening Techniques"]}]}],"canonical_facts":{"dc:contributor":["Jeff Curtis","Kim Summerhays","Larry Margerum"],"dc:creator":["Qin, Yishun"],"dc:date.available":["2013-12-16T08:00:00Z"],"dc:description.abstract":["The electron transfer (ET) self-exchange rates on a series of complexes of (NH3)5RuII/III L2+/3+ in D2O (where L is a substituted pyridyl ligand) were investigated by dynamic NMR measurements. Significant rate enhancement was observed for the cases of L = 3-phenylpyridine and 4-phenylpridine due to possible π-π stacking between Phpy ligands. These observations matche well with recent stopped-flow work by Mehmood on a similar set of related pseudo-self exchange reactions. Kinetics of the (NH3)5RuII/III (3-trifluoromethylpyridine)2+/3+ self-exchange reactions with addition of various simple/complex salts and hexacyano salts (K4M(CN)6 with M = Fe, Os and Ru) were also studied. The halide ions showed qualitatilvely-similar behavior compared to the stopped-flow work by Sista and the same quantitative decrease in the magnitude of salt effect as reported by Inagaki. The hexacyano salts were found to have a striking effect on the ET rate with a clear trend of Fe > >Os > Ru. This could be explained as a probable “superexchange” type mechanism dominated by the “hole-transfer” pathway based on the trend between the catalytic effect and the redox potential of the particular M(CN)4- ion. Kinetic modeling data also show the strongest catalytic effect of Fe which gives a ketx/ket of 126. Temperature-dependent experiments show that the rate enhancement of hexacyano series is due to a increased enthalpic barrier and less negative entropic barrier.
"],"dc:identifier":["https://repository.usfca.edu/thes/74"],"dc:subject":["superexchange","pyridyl ligand substituent effects","ion pair","Inorganic Chemistry"],"dc:title":["Mechanistic Studies of Bimolecular Electron Transfer Self-Exchange Rates of Ruthenium Ammine Pyridyl Complexes Measured by NMR Line Broadening Techniques"],"thesis:degree_discipline":["Chemistry"],"thesis:degree_level":["Thesis"],"thesis:degree_name":["Master of Science (MS)"]},"updated_at":"2026-07-24T05:42:43Z"}