Azulene-substituted aromatic amines. synthesis and amphoteric redox behavior of N,N-Di(6-azulenyl)-p-toluidine and N,N,N′,N′-tetra(6-azulenyl)-p-phenylenediamine and their derivatives
Azulene-substituted aromatic amines. synthesis and amphoteric redox behavior of N,N-Di(6-azulenyl)-p-toluidine and N,N,N′,N′-tetra(6-azulenyl)-p-phenylenediamine and their derivatives
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DOI：
10.1021/jo048489s
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发表时间：
2005-03-18
影响因子：
3.6
通讯作者：
Tajiri, A
中科院分区：
文献类型：
--
作者：
Ito, S;Kubo, T;Tajiri, A
以钯为催化剂，通过氨基偶氮化反应合成了N，N-二(6-偶氮基)对甲基苯胺(1a)和N，N，N‘，N’-四(6-偶氮基)对苯二胺(2a)及其衍生物及其在6-偶氮基(1b和2b)上分别带有1，3-二(乙氧基甲酰基)取代基的衍生物。用循环伏安法对各化合物的氧化还原行为进行了表征。由于6-天青基之间的共振稳定作用，这些化合物可以很容易地还原成稳定的阴离子自由基和二阴离子双自由基，并根据胺基的不同表现出电化学氧化。对阴离子自由基和由胺1b和二胺2b电化学还原生成的二阴离子二自由基的ESR测量表明，这些自由基的未成对电子在包括中心氮原子在内的整个天青环上离域。对电化学还原过程中的胺1a、b和二胺2a、b进行的UV-Vis光谱分析表明，中性物种的吸收带逐渐减少，新的吸收峰分别在625、605、640和610 nm处增加，并分别在502、562、478和545 nm处形成明确的等色点。ESR和UV-Vis光谱的联合研究表明，产生新的吸收峰的物种是热力学稳定性较高的芳香胺和二胺的阴离子自由基和双阴离子自由基的生成。
N,N-Di(6-azulenyl)-p-toluidine (1a) and N,N,N',N'-tetra(6-azulenyl)-p-phenylenediamine (2a) and their derivatives with 1,3-bis(ethoxycarbonyl) substituents on each 6-azulenyl group (1b and 2b) were prepared by Pd-catalyzed amine azulenylation and characterized as a study into new aromatic amines for multistage amphoteric redox materials. The redox behavior of each compound was characterized by cyclic voltammetry. These compounds undergo facile reduction to stable anion radicals and dianion diradicals owing to the resonance stabilization between the 6-azulenyl groups and exhibit electrochemical oxidation depending on the amine subunits. The ESR measurement of anion radicals and a dianion diradical generated by the electrochemical reduction of amine 1b and diamine 2b revealed that the unpaired electron of these radicals delocalizes over the entire azulene ring including the central nitrogen atoms. UV-vis spectral analysis of amines 1a,b and diamines 2a,b, taken during the electrochemical reduction, exhibited a gradual decrease of the absorption bands of the neutral species along with an increase of the new absorption maxima at 625, 605, 640, and 610 nm, respectively, with the development of well-defined isosbestic points at 502, 562, 478, and 545 nm, respectively. As indicated by a combined ESR and UV-vis spectral study, the species giving rise to the new absorption maxima are concluded to be the generation of anion radicals and dianion diradicals of aromatic amines and diamines with high thermodynamic stability.