Vakulskaya Tamara I, Larina Lyudmila I, Vashchenko Alexander V
A.E. Favorsky Irkutsk Institute of Chemistry of the Russian Academy of Sciences, Siberian Branch, Favorsky Street 1, Irkutsk, 664033, Russia.
Magn Reson Chem. 2011 Aug;49(8):508-13. doi: 10.1002/mrc.2783. Epub 2011 Jul 12.
Several representatives of natural flavonoids and their synthetic nitro-derivatives have been investigated by polarography and electron paramagnetic resonance (EPR) spectroscopy under electrochemical reduction in acetonitrile, dimethylformamide (DMF), dimethylsulfoxide (DMSO) or 1,2-dimethoxyethane. All the compounds studied are reduced in the first stage by one-electron transfer, apart from flavanone, which accepts two electrons simultaneously. However, the primary radical anions were detected by EPR spectroscopy only for 4'-nitroflavone. It was shown that radical anions of other flavonoids quickly dimerized. The analysis of the temperature dependence of the hyperfine interaction constants and broadening of lines in EPR spectra of 4'-nitroflavone radical anions has shown that the distribution of spin density is due to both the change of polarity of the medium and rotation of the nitrophenyl moiety. The assignment of hyperfine structure constants for the 4'-nitroflavone radical anion was confirmed by density functional theory (DFT) calculations.
通过极谱法和电子顺磁共振（EPR）光谱，在乙腈、二甲基甲酰胺（DMF）、二甲基亚砜（DMSO）或1,2 - 二甲氧基乙烷中进行电化学还原的条件下，对几种天然黄酮类化合物及其合成硝基衍生物进行了研究。除了同时接受两个电子的黄烷酮外，所有研究的化合物在第一阶段都是通过单电子转移进行还原的。然而，仅通过EPR光谱检测到了4'-硝基黄酮的初级自由基阴离子。结果表明，其他黄酮类化合物的自由基阴离子会迅速二聚。对4'-硝基黄酮自由基阴离子的EPR光谱中超精细相互作用常数的温度依赖性和谱线展宽的分析表明，自旋密度的分布是由于介质极性的变化和硝基苯基部分的旋转共同导致的。密度泛函理论（DFT）计算证实了4'-硝基黄酮自由基阴离子超精细结构常数的归属。
