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Amidinoquinoxaline N-oxides: spin trapping of O- and C-centered radicals
Organic & Biomolecular Chemistry ( IF 3.2 ) Pub Date : 2017-08-23 00:00:00 , DOI: 10.1039/c7ob01387f
Nadia Gruber 1, 2, 3, 4, 5 , Liliana R. Orelli 5, 6, 7, 8, 9 , Roberto Cipolletti 1, 2, 3, 4 , Pierluigi Stipa 1, 2, 3, 4
Affiliation  

Amidinoquinoxaline N-oxides represent a novel family of heterocyclic spin traps. In this work, their ability to trap O- and C-centered radicals was tested using selected derivatives with different structural modifications. All the studied nitrones were able to trap radicals forming persistent spin adducts, also in the case of OH and OOH radicals which are of wide biological interest as examples of ROS. The stability of the adducts was mainly attributed to the wide delocalization of the unpaired electron over the whole quinoxaline moiety. The nitroxide spectral parameters (hfccs and g-factors) were analyzed and the results were supported by DFT calculations. The N-19 hfccs and g-factors were characteristic of each aminoxyl and could aid in the identification of the trapped radical. The enhanced stability of the OH adducts under the employed reaction conditions could be ascribed to their possible stabilization by IHBs with two different acceptors: the N–O˙ moiety or the amidine functionality. DFT calculations indicate that the preferred IHB is strongly conditioned by the amidine ring size. While five membered homologues show a clear preference for the IHB with the N–O˙ group, in six membered derivatives this stabilizing interaction is preferentially established with the amidine nitrogen as an IHB acceptor.

中文翻译:

mid喹喔啉N-氧化物:O和C中心自由基的自旋俘获

mid喹喔啉N-氧化物代表杂环自旋捕集阱的新家族。在这项工作中,使用选定的具有不同结构修饰的衍生物测试了它们捕获O-和C-中心自由基的能力。所有研究过的硝酮都能够捕获形成持久性自旋加合物的自由基,同样在具有广泛生物学意义的OH和OOH自由基的情况下,例如ROS。加合物的稳定性主要归因于未配对电子在整个喹喔啉部分上的广泛离域。分析了氮氧化物光谱参数(hfccs和g因子),结果得到DFT计算的支持。N-19 hfcc和g因子是每个氨氧基的特征,可以帮助识别被困的自由基。在所采用的反应条件下,OH加合物稳定性的提高可能归因于具有两个不同受体的IHBs可能的稳定作用:N–O˙部分或am官能团。DFT计算表明,优选的IHB受到idine环大小的强烈调节。虽然五元同系物显示出对带有N–O˙基团的IHB的明显偏好,但在六元衍生物中,这种稳定的相互作用优先建立在以nitrogen氮作为IHB受体的情况下。
更新日期:2017-09-20
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