A kinetic study of the one electron oxidation of substituted ferrocenes (FcX: X = H, COPh, COMe, CO(2)Et, CONH(2), CH(2)OH, Et, and Me(2)) by a series of N-oxyl radicals (succinimide-N-oxyl radical (SINO), maleimide-N-oxyl radical (MINO), 3-quinazolin-4-one-N-oxyl radical (QONO) and 3-benzotriazin-4-one-N-oxyl radical (BONO)), has been carried out in CH(3)CN. N-oxyl radicals were produced by hydrogen abstraction from the corresponding N-hydroxy derivatives by the cumyloxyl radical. With all systems, the rate constants exhibited a satisfactory fit to the Marcus equation allowing us to determine self-exchange reorganization energy values (lambda(NO)center dot(/NO)-) which have been compared with those previously determined for the PINO/PINO(-) and BTNO/BTNO(-) couples. Even small modification of the structure of the N-oxyl radicals lead to significant variation of the lambda(NO)center dot(/NO)- values. The lambda(NO)center dot(/NO)- values increase in the order BONO < BTNO < QONO < PINO < SINO < MINO which do not parallel the order of the oxidation potentials. The higher lambda(NO)center dot(/NO)- values found for the MINO and SINO radicals might be in accordance with a lower degree of spin delocalization in the radicals MINO and SINO and charge delocalization in the anions MINO(-) and SINO(-) due to the absence of an aromatic ring in their structure.

One-electron oxidation of ferrocenes by short-lived N-oxyl radicals. The role of structural effects on the intrinsic electron transfer reactivities / Baciocchi, Enrico; Massimo, Bietti; D'Alfonso, Claudio; Lanzalunga, Osvaldo; Lapi, Andrea; Michela, Salamone. - In: ORGANIC & BIOMOLECULAR CHEMISTRY. - ISSN 1477-0520. - STAMPA. - 9:11(2011), pp. 4085-4090. [10.1039/c0ob01257b]

One-electron oxidation of ferrocenes by short-lived N-oxyl radicals. The role of structural effects on the intrinsic electron transfer reactivities

BACIOCCHI, Enrico;D'ALFONSO, CLAUDIO;LANZALUNGA, Osvaldo;LAPI, Andrea;
2011

Abstract

A kinetic study of the one electron oxidation of substituted ferrocenes (FcX: X = H, COPh, COMe, CO(2)Et, CONH(2), CH(2)OH, Et, and Me(2)) by a series of N-oxyl radicals (succinimide-N-oxyl radical (SINO), maleimide-N-oxyl radical (MINO), 3-quinazolin-4-one-N-oxyl radical (QONO) and 3-benzotriazin-4-one-N-oxyl radical (BONO)), has been carried out in CH(3)CN. N-oxyl radicals were produced by hydrogen abstraction from the corresponding N-hydroxy derivatives by the cumyloxyl radical. With all systems, the rate constants exhibited a satisfactory fit to the Marcus equation allowing us to determine self-exchange reorganization energy values (lambda(NO)center dot(/NO)-) which have been compared with those previously determined for the PINO/PINO(-) and BTNO/BTNO(-) couples. Even small modification of the structure of the N-oxyl radicals lead to significant variation of the lambda(NO)center dot(/NO)- values. The lambda(NO)center dot(/NO)- values increase in the order BONO < BTNO < QONO < PINO < SINO < MINO which do not parallel the order of the oxidation potentials. The higher lambda(NO)center dot(/NO)- values found for the MINO and SINO radicals might be in accordance with a lower degree of spin delocalization in the radicals MINO and SINO and charge delocalization in the anions MINO(-) and SINO(-) due to the absence of an aromatic ring in their structure.
2011
01 Pubblicazione su rivista::01a Articolo in rivista
One-electron oxidation of ferrocenes by short-lived N-oxyl radicals. The role of structural effects on the intrinsic electron transfer reactivities / Baciocchi, Enrico; Massimo, Bietti; D'Alfonso, Claudio; Lanzalunga, Osvaldo; Lapi, Andrea; Michela, Salamone. - In: ORGANIC & BIOMOLECULAR CHEMISTRY. - ISSN 1477-0520. - STAMPA. - 9:11(2011), pp. 4085-4090. [10.1039/c0ob01257b]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/380713
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