Levitskiy Oleg A, Bogdanov Alexey V, Klimchuk Ivan A, Magdesieva Tatiana V
Department of Chemistry, Lomonosov Moscow State University, Leninskie Gory 1/3, 119991, Moscow, Russian Federation.
Chempluschem. 2022 Mar;87(3):e202100508. doi: 10.1002/cplu.202100508. Epub 2021 Dec 29.
A series of new pyridyl- or 2-pyridyloxide-containing donor-acceptor diarylnitroxides was obtained and characterized; high stability of the ortho-2-pyridyl-containing diarylnitroxides was determined by kinetic measurements (τ =1733 h in benzene). Comparative voltammetric study of new nitroxides and their analog in which the Py replaces the Ph group revealed both through-bond and through-space stabilization of the NO redox states with the pyridyl/ 2-pyridyloxide moiety, providing reversibility of both oxidation and reduction processes. Adaptive conformational behavior of new pyridyl/pyridyloxide containing nitroxides upon one-electron oxidation and reduction was confirmed by DFT calculations. Stimuli-responsive conformational changes allow switching on/off dispersion and electrostatic interactions within the molecule and increase stability of the redox states. Spectroelectrochemical measurements provided experimental evidence for reversibility of the through-space stabilization of the oxidized state of the nitroxides with the neighboring pyridine lone pair.
合成并表征了一系列含吡啶基或2-吡啶氧基的供体-受体二芳基氮氧化物；通过动力学测量确定了含邻位-2-吡啶基的二芳基氮氧化物具有高稳定性（在苯中τ = 1733 h）。对新氮氧化物及其Py取代Ph基团的类似物进行的比较伏安研究表明，吡啶基/2-吡啶氧基部分对NO氧化还原态具有键内和空间稳定作用，使得氧化和还原过程均具有可逆性。DFT计算证实了含新吡啶基/吡啶氧基的氮氧化物在单电子氧化和还原时的适应性构象行为。刺激响应性构象变化可开启/关闭分子内的色散和静电相互作用，并提高氧化还原态的稳定性。光谱电化学测量为氮氧化物氧化态与相邻吡啶孤对之间的空间稳定作用的可逆性提供了实验证据。
