Details

Autor(en) / Beteiligte

• Rosokha, Sergiy V
• Kochi, Jay K

Titel

Continuum of Outer- and Inner-Sphere Mechanisms for Organic Electron Transfer. Steric Modulation of the Precursor Complex in Paramagnetic (Ion-Radical) Self-Exchanges

Ist Teil von

• Journal of the American Chemical Society, 2007-03, Vol.129 (12), p.3683-3697

Ort / Verlag

United States: American Chemical Society

Erscheinungsjahr

2007

Link zum Volltext

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Transient 1:1 precursor complexes for intermolecular self-exchange between various organic electron donors (D) and their paramagnetic cation radicals (D +•), as well as between different electron acceptors (A) paired with their anion radicals (A -•), are spectrally (UV−NIR) observed and structurally (X-ray) identified as the cofacial (π-stacked) associates [D, D +•] and [A -•, A], respectively. Mulliken−Hush (two-state) analysis of their diagnostic intervalence bands affords the electronic coupling elements (H DA), which together with the Marcus reorganization energies (λ) from the NIR spectral data are confirmed by molecular-orbital computations. The H DA values are found to be a sensitive function of the bulky substituents surrounding the redox centers. As a result, the steric modulation of the donor/acceptor separation (r DA) leads to distinctive electron-transfer rates between sterically hindered donors/acceptors and their more open (unsubstituted) parents. The latter is discussed in the context of a continuous series of outer- and inner-sphere mechanisms for organic electron-transfer processes in a manner originally formulated by Taube and co-workers for inorganic (coordination) donor/acceptor dyadswith conciliatory attention paid to traditional organic versus inorganic concepts.