Chemical, Pulse Radiolysis and Density Functional Studies of a New, Labile 5,6-Indolequinone and Its Semiquinone
作者:Alessandro Pezzella、Orlando Crescenzi、Anna Natangelo、Lucia Panzella、Alessandra Napolitano、Suppiah Navaratnam、Ruth Edge、Edward J. Land、Vincenzo Barone、Marco d'Ischia
DOI:10.1021/jo0615807
日期:2007.3.1
produced by pulse radiolytic oxidation of 1a at pH 7.0. DFT investigations indicated the 6-phenoxyl radical and the N-protonated radical anion as the most stable tautomers for the neutral and anion forms of the semiquinone, respectively. Calculated absorption spectra in water gave bands at 350 (sh) and 500 nm for the neutral form and at 310 and 360 (sh) nm for the anion. Disproportionation of the semiquinone
5,6-吲哚醌及其半醌(5,6-二羟基吲哚氧化转化为真木兰生物聚合物的关键瞬态中间体)的化学和光谱表征是一项最具挑战性的任务。在本文中,我们报告了使用集成化学,脉冲辐射分解和计算方法对新型,相对较长寿命的5,6-吲哚醌及其半醌的表征。在冷的乙酸乙酯或水性缓冲液中,用邻氯苯腈将5,6-二羟基-3-碘吲哚(1a)氧化得到醌:它显示出约400和600 nm的电子吸收带,并用Na 2 S还原为1a。2 O 4,并与邻苯二胺产生少量3-iodo-1 H -pyrrolo [2,3- b ]吩嗪(2)。半醌在380 nm(sh)和520 nm处表现出最大吸收,被检测为通过在pH 7.0下1a的脉冲辐射氧化而产生的初始物种。DFT研究表明,6-苯氧基自由基和N-质子化自由基阴离子分别是半醌的中性和阴离子形式最稳定的互变异构体。计算出的在水中的吸收光谱给出了中性形式的350(sh)和500 nm的谱带,以