ELECTRON-SPIN-RESONANCE AND H-1-NMR STUDIES OF A NEW CLASS OF NITROXYL, NITRONYLNITROXYL AND IMINONITROXYL RADICALS
ELECTRON-SPIN-RESONANCE AND H-1-NMR STUDIES OF A NEW CLASS OF NITROXYL, NITRONYLNITROXYL AND IMINONITROXYL RADICALS
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DOI：
10.1002/mrc.1260240304
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发表时间：
1986-03-01
影响因子：
2
通讯作者：
VOLODARSKY, LB
中科院分区：
文献类型：
--
作者：
KHRAMTSOV, VV;WEINER, LM;VOLODARSKY, LB
提出了在亲核试剂的存在下，用o2或pbo2氧化4H -咪唑二氮氧化物，合成硝基硝基氧基（NNR）、亚硝基硝基氧基（INR）和硝基自由基（NR）的新方法。这种方法可以制备用已知方法无法合成的自由基。用ESR和1h NMR对这些自由基进行了研究。测量并赋值了NNR的超精细相互作用常数（在某些情况下使用了含有15n的自由基）。研究了NNR中官能团（OH, NH2）的质子化和去质子化对其ESR谱的影响，并通过ESR测量了这些自由基的pk值。发现了两种异构体INR的ESR谱的差异，并通过1h NMR确定了这些自由基的结构。研究了3 -咪唑啉3 -氧化物硝基自由基中自旋密度离域的变化，发现当α -位置的甲氧基数量增加到n - o片段时，自旋密度被“推出”到这些自由基的外围片段。ESR检测到在α -位置的一个大体积取代基的σ -键周围阻碍了n - o片段的旋转。这种受阻旋转的活化能为ΔE= 30±1.7 kJ mol−1。
A new synthesis of nitronylnitroxyl (NNR), iminonitroxyl (INR) and nitroxyl radicals (NR) is suggested, involving oxidation of 4H‐imidazol di‐N‐oxides with O2or PbO2in the presence of nucleophilic reagents. This method allowed the preparation of radicals which could not be synthesized by known procedures. These radicals were studied by ESR and1H NMR spectroscopy. The hyperfine interaction constants of the NNR were measured and assigned (in some cases radicals containing15N were used). The influence of protonation and deprotonation of functional groups (OH, NH2) in the NNR on their ESR spectra was investigated and the pKvalues of these radicals were measured by ESR.Differences between the ESR spectra of two isomeric INR were found, and the structures of these radicals were established by1H NMR. Changes in spin density delocalization in 3‐imidazoline 3‐oxide nitroxyl radicals were studied, and the spin density was found to be ‘pushed out’ to the peripheral fragments of these radicals on increasing the number of methoxy groups in the α‐position to the N—O.fragment. Hindered rotation around the σ‐bond of a bulky substituent in the α‐position to the N—O.fragment was detected by ESR. The activation energy of this hindered rotation was ΔE= 30±1.7 kJ mol−1.