Sequential Electron-Transfer and Proton-Transfer Pathways in Hydride-Transfer Reactions from Dihydronicotinamide Adenine Dinucleotide Analogues to Non-heme Oxoiron(IV) Complexes and p-Chloranil. Detection of Radical Cations of NADH Analogues in Acid-Promoted Hydride-Transfer Reactions
Sequential Electron-Transfer and Proton-Transfer Pathways in Hydride-Transfer Reactions from Dihydronicotinamide Adenine Dinucleotide Analogues to Non-heme Oxoiron(IV) Complexes and p-Chloranil. Detection of Radical Cations of NADH Analogues in Acid-Promoted Hydride-Transfer Reactions
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DOI：
10.1021/ja804969k
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发表时间：
2008-11-12
影响因子：
15
通讯作者：
Nam, Wonwoo
中科院分区：
文献类型：
--
作者：
Fukuzumi, Shunichi;Kotani, Hiroaki;Nam, Wonwoo
从二氢烟酰胺腺嘌呤二核苷酸(NADH)类似物，如10-甲基-9，10-二氢吖啶(AcrH(2))及其衍生物1-苄基-1，4-二氢烟酰胺(BNAH)及其氚化合物，氢化物转移到非血红素铁(IV)配合物，如[(L)Fe(IV)(O)](2+)(L=N4Py，Bn-TPEN，和TMC)，在乙腈中生成相应的NAD+类似物和非血红素铁(II)配合物。氢化物从NADH类似物转移到对氯苯醚(Cl(4)q)，生成相应的NAD(+)类似物和对苯二酚阴离子(Cl(4)QH(-))。观察到的氢化物从NADH类似物到非血红素氧铁(IV)络合物的二级转移速率常数(logk(H))的对数与从同一系列NADH类似物到Cl(4)Q的氢化物转移的对数线性相关，包括相似的动力学氘同位素效应。NADH类似物向非血红素氧铁(IV)络合物的氢化物转移的对数k(H)值也与NADH类似物的自由基阳离子去质子化的对数k(H)值呈线性相关。这种线性关系表明，NADH类似物对非血红素氧铁(IV)络合物和Cl(4)Q的氢化物转移反应是通过从NADH类似物到氧铁(IV)络合物的电子转移，然后从NADH类似物的自由基阳离子的限速去质子化和随后从去质子化的自由基到Fe(III)络合物的快速电子转移来产生相应的NAD(+)类似物和Fe(II)络合物。高氯酸的存在加速了NADH类似物的电子转移途径，并用电子自旋共振光谱和UV-Vis光谱检测到NADH类似物在酸促进的氢化物转移反应中产生的自由基阳离子。这一结果提供了第一个直接证据，证明从NADH类似物到非血红素氧铁(IV)络合物的氢化物转移是通过电子转移途径进行的。
Hydride transfer from dihydronicotinamide adenine dinucleotide (NADH) analogues, such as 10-methyl-9,10-dihydroacridine (AcrH(2)) and its derivatives, 1-benzyl-1,4-dihydronicotinamide (BNAH), and their deuterated compounds, to non-heme oxoiron(IV) complexes such as [(L)Fe(IV)(O)](2+) (L = N4Py, Bn-TPEN, and TMC) occurs to yield the corresponding NAD+ analogues and non-heme iron(II) complexes in acetonitrile. Hydride transfer from the NADH analogues to p-chloranil (Cl(4)Q) also occurs to produce the corresponding NAD(+) analogues and the hydroquinone anion (Cl(4)QH(-)). The logarithms of the observed second-order rate constants (log k(H)) of hydride transfer from NADH analogues to non-heme oxoiron(IV) complexes are linearly correlated with those of hydride transfer from the same series of NADH analogues to Cl(4)Q, including similar kinetic deuterium isotope effects. The log k(H) values of hydride transfer from NADH analogues to non-heme oxoiron(IV) complexes are also linearly correlated with those of deprotonation of the radical cations of NADH analogues. Such linear correlations indicate that overall hydride-transfer reactions of NADH analogues to both non-heme oxoiron(IV) complexes and Cl(4)Q occur via electron transfer from NADH analogues to the oxoiron(IV) complexes, followed by rate-limiting deprotonation from the radical cations of NADH analogues and subsequent rapid electron transfer from the deprotonated radicals to the Fe(III) complexes to yield the corresponding NAD(+) analogues and the Fe(II) complexes. The electron-transfer pathway was accelerated by the presence of perchloric acid, and the resulting radical cations of NADH analogues were detected by electron spin resonance spectroscopy and UV-vis spectrophotometry in the acid-promoted hydride-transfer reactions from NADH analogues to non-heme oxoiron(IV) complexes. This result provides the first direct evidence that a hydride transfer from NADH analogues to non-heme oxoiron(IV) complexes proceeds via an electron-transfer pathway.