Selective one-electron and two-electron reduction of C60 with NADH and NAD dimer analogues via photoinduced electron transfer
Selective one-electron and two-electron reduction of C60 with NADH and NAD dimer analogues via photoinduced electron transfer
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DOI：
10.1021/ja9813459
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发表时间：
1998-08-19
影响因子：
15
通讯作者：
Ito, O
中科院分区：
文献类型：
--
作者：
Fukuzumi, S;Suenobu, T;Ito, O
C-60选择性单电子还原为C-60（.-）通过光诱导电子从NADH类似物1-苄基-1，4-二氢烟酰胺（BNAH）和二聚体类似物[（BNA）（2）]转移到C-60的三重态激发态，得到了C-60（.-）在（BNA）（2）的情况下，超过1; Φ（无穷大）= 1.3。在这种情况下，从（BNA）（2）到三重激发态（C-3（60）*）的初始电子转移之后，在所得（BNA）（2）（.+）中快速C-C键断裂。给BNA（.）和BNA（+）之间的电子转移以及BNA（.）到C-60产生BNA（+）和C-60（.-）当（BNA）（2）作为双电子供体产生2当量的C-60（.-）当BNAH被4-叔丁基化BNAH（t-BuBNAH）替代时，与C-60的光化学反应不产生C-60（.-）而是选择性地对叔丁基化阴离子（t-BuC 60-）进行反应。在这种情况下，从t-BuBNAH到C-3（60）* 的初始电子转移也伴随着t-BuBNAH（.+）中的快速C-C键断裂。给t-Bu-.，它与C-60（.-）在电子转移中产生，产生t-BuC 60-。在可见光照射下，用另一种NADH类似物10-甲基-9，10-二氢吖啶（AcrH（2）），在含三氟乙酸的脱气苯甲腈溶液中，C-60选择性地双电子还原为1，2-二氢[60]富勒烯（1，2-C60 H2）。对量子产率、氘同位素动力学效应和AcrH（2）对C-60三重态-三重态吸收猝灭的研究表明，光化学还原是通过光诱导电子从10-甲基-9，10-二氢吖啶转移到C-60三重态激发态，然后再从AcrH（2）（.+）转移质子进行的。到C-60（.-）和来自去质子化的吖啶基自由基（AcrH（.））C60H。在三氟乙酸的存在下反应，得到最终产物10-甲基吖啶鎓离子（AcrH（+））和1，2-C60 H2。在激光闪光光解中，成功地探测到了在光诱导电子转移中形成的自由基离子对的瞬态光谱。本文根据NADH和二聚体类似物的氧化还原和酸碱性质的差异，讨论了C-60选择性单电子还原和双电子还原的机理差异。
The selective one-electron reduction of C-60 to C-60(.-) is attained through photoinduced electron transfer from an NADH analogue, 1-benzyl-1,4-dihydronicotinamide (BNAH), and the dimer analogue [(BNA)(2)] to the triplet excited stare of C-60 The limiting quantum yield for formation of C-60(.-) in the case of (BNA)(2) exceeds unity; Phi(infinity) = 1.3. Ln this case, the initial electron transfer from (BNA)(2) to the triplet excited state (C-3(60)*) is followed by fast C-C bond cleavage in the resulting (BNA)(2)(.+) to give BNA(.) and BNA(+) and the second electron transfer from BNA(.) to C-60 yields BNA(+) and C-60(.-) when (BNA)(2) acts as a two-electron donor to produce 2 equiv of C-60(.-) When BNAH is replaced by 4-tert-butylated BNAH (t-BuBNAH), the photochemical reaction with C-60 yields not C-60(.-) but instead the tert-butylated anion (t-BuC60-) selectively. In this case, the initial electron transfer from t-BuBNAH to C-3(60)* is also followed by fast C-C bond cleavage in t-BuBNAH(.+) to give t-Bu-., which is coupled with C-60(.-) produced in the electron transfer to yield t-BuC60-. The selective two-electron reduction of C-60 to 1,2-dihydro[60]fullerene (1,2-C60H2) is also attained with the use of another NADH analogue 10-methyl-9,10-dihydroacridine (AcrH(2)), under visible light irradiation in deaerated benzonitrile solution containing trifluoroacetic acid. The studies on the quantum yields, the kinetic deuterium isotope effects, and the quenching of the triplet-triplet absorption of C-60 by AcrH(2) have revealed that the photochemical reduction proceeds via photoinduced electron transfer from 10-methyl-9,10-dihydroacridine to the triplet excited state of C-60, which is followed by proton transfer from AcrH(2)(.+) to C-60(.-) and a second electron transfer from the deprotonated acridinyl radical (AcrH(.)) to C60H. in the presence of trifluoroacetic acid to yield the final products 10-methylacridinium ion (AcrH(+)) and 1,2-C60H2. The transient spectra of the radical ion pair formed in the photoinduced electron transfer have been detected successfully in laser flash photolysis of each NADH analogue-C-60 system. The mechanistic difference between the selective one- and two-electron reductions of C-60 is discussed On the basis of the difference in the redox and acid-base propel-ties of NADH and the dimer analogues.