TY - JOUR
T1 - Scandium ion-promoted photoinduced electron-transfer oxidation of fullerenes and derivatives by p-chloranil and p-benzoquinone
AU - Fukuzumi, S.
AU - Mori, H.
AU - Imahori, H.
AU - Suenobu, T.
AU - Araki, Y.
AU - Ito, O.
AU - Kadish, K. M.
PY - 2001/12/19
Y1 - 2001/12/19
N2 - In the presence of scandium triflate, an efficient photoinduced electron transfer from the triplet excited state of C60 to p-chloranil occurs to produce C60 radical cation which has a diagnostic NIR (near-infrared) absorption band at 980 nm, whereas no photoinduced electron transfer occurs from the triplet excited state of C60 (3C60*) to p-chloranil in the absence of scandium ion in benzonitrile. The electron-transfer rate obeys pseudo-first-order kinetics and the pseudo-first-order rate constant increases linearly with increasing p-chloranil concentration. The observed second-order rate constant of electron transfer (ket) increases linearly with increasing scandium ion concentration. In contrast to the case of the C60/p-chloranil/Sc3+ system, the ket value for electron transfer from 3C60* to p-benzoquinone increases with an increase in Sc3+ concentration ([Sc3+]) to exhibit a first-order dependence on [Sc3+], changing to a second-order dependence at the high concentrations. Such a mixture of first-order and second-order dependence on [Sc3+] is also observed for a Sc3+-promoted electron transfer from CoTPP (TPP2- = tetraphenylporphyrin dianion) to p-benzoquinone. This is ascribed to formation of 1:1 and 1:2 complexes between the generated semiquinone radical anion and Sc3+ at the low and high concentrations of Sc3+, respectively. The transient absorption spectra of the radical cations of various fullerene derivatives were detected by laser flash photolysis of the fullerene/p-chloranil/ Sc3+ systems. The ESR spectra of the fullerene radical cations were also detected in frozen PhCN at 193 K under photoirradiation of the fullerene/p-chloranil/Sc3+ systems. The Sc3+-promoted electron-transfer rate constants were determined for photoinduced electron transfer from the triplet excited states of C60, C70, and their derivatives to p-chloranil and the values are compared with the HOMO (highest occupied molecular orbital) levels of the fullerenes and their derivatives.
AB - In the presence of scandium triflate, an efficient photoinduced electron transfer from the triplet excited state of C60 to p-chloranil occurs to produce C60 radical cation which has a diagnostic NIR (near-infrared) absorption band at 980 nm, whereas no photoinduced electron transfer occurs from the triplet excited state of C60 (3C60*) to p-chloranil in the absence of scandium ion in benzonitrile. The electron-transfer rate obeys pseudo-first-order kinetics and the pseudo-first-order rate constant increases linearly with increasing p-chloranil concentration. The observed second-order rate constant of electron transfer (ket) increases linearly with increasing scandium ion concentration. In contrast to the case of the C60/p-chloranil/Sc3+ system, the ket value for electron transfer from 3C60* to p-benzoquinone increases with an increase in Sc3+ concentration ([Sc3+]) to exhibit a first-order dependence on [Sc3+], changing to a second-order dependence at the high concentrations. Such a mixture of first-order and second-order dependence on [Sc3+] is also observed for a Sc3+-promoted electron transfer from CoTPP (TPP2- = tetraphenylporphyrin dianion) to p-benzoquinone. This is ascribed to formation of 1:1 and 1:2 complexes between the generated semiquinone radical anion and Sc3+ at the low and high concentrations of Sc3+, respectively. The transient absorption spectra of the radical cations of various fullerene derivatives were detected by laser flash photolysis of the fullerene/p-chloranil/ Sc3+ systems. The ESR spectra of the fullerene radical cations were also detected in frozen PhCN at 193 K under photoirradiation of the fullerene/p-chloranil/Sc3+ systems. The Sc3+-promoted electron-transfer rate constants were determined for photoinduced electron transfer from the triplet excited states of C60, C70, and their derivatives to p-chloranil and the values are compared with the HOMO (highest occupied molecular orbital) levels of the fullerenes and their derivatives.
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U2 - 10.1021/ja016335d
DO - 10.1021/ja016335d
M3 - Article
C2 - 11741408
AN - SCOPUS:0035915314
VL - 123
SP - 12458
EP - 12465
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
SN - 0002-7863
IS - 50
ER -