Structure and Dynamics of Bis(triphenylphosphine)-3,6-di-tert-butyl-o-semiquinone Radical Anion Complexes of Ag+ and Cu+

Rakhimov, R.R.; Hawkins, T.N.; Hwang, J.S.; Prokof\textquotesingleev, A.I.; Aleksandrov, A.I.

Авторы: Rakhimov Rakhim R., Hawkins Tamika N., Hwang Jimmy S., Prokof\textquotesingleev Alexander I., Aleksandrov Aleksey I.
Журнал: The Journal of Physical Chemistry A: Molecules, Clusters, and Aerosols
Том: 107
Номер: 33
Год издания: 2003
Издательство: American Chemical Society
Местоположение издательства: United States
Первая страница: 6345
Последняя страница: 6350
DOI: 10.1021/jp030315b
Аннотация: Complexes of Ag+ and Cu+ with 3,6-di-tert-butyl-o-semiquinone radical anion (SQ•-) and two triphenylphosphine (PPh3) ligands have been investigated by electron paramagnetic resonance (EPR) in organic solvents.High-temperature EPR spectra of the Ag+ and Cu+ complexes contain lines of hyperfine splittings due totwo equivalent 1H nuclei in the 4,5-positions of the aromatic ring of the SQ•- ligand, two equivalent 31Pnuclei from the two PPh3 ligands, and 107,109Ag and 63,65Cu nuclear isotopes, respectively. On the basis of thetemperature dependence of the 31P hyperfine interaction constant a(31P), the structure of the Ag+ complex atlow temperature was determined to be planar, while at higher temperatures the increase in the values ofa(31P) shows that phosphorus atoms of the two PPh3 ligands move out of the π-plane of the SQ•- ligand.EPR spectra of the Ag+ complex with variable temperature exhibit alternating line width effect in hyperfinesplitting due to the two aromatic protons in the SQ•- ligand. At low temperatures these two protons becomenonequivalent. This effect reveals a dynamic charge redistribution within Ag+ and two oxygen atoms of theSQ•- ligand. In the Cu+ complex, we have found a temperature-independent symmetric charge distributionwithin two oxygen atoms of the radical anion and Cu+, but different positions of the two PPh3 ligands at lowtemperatures. EPR spectra of the Cu+ complex at variable temperature reveal the dynamic exchange in thepositions of PPh3 ligands. The rates of this process are on the order of solvent reorientation frequencies,while intramolecular electron exchange rates in the Ag+ complex are about 2 orders of magnitude lower. Therate of the electron exchange reaction dramatically decreases in viscous mineral oil, which shows that theintramolecular charge redistribution reaction is controlled by nonpolar solvent dynamics.
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Structure and Dynamics of Bis(triphenylphosphine)-3,6-di-tert-butyl-o-semiquinone Radical Anion Complexes of Ag+ and Cu+статья

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