Wydział Chemii , Uniwersytet Wrocławski , ul. F. Joliot-Curie 14 , 50-383 Wrocław , Poland.
PORT-Polski Ośrodek Rozwoju Technologii , ul. Stabłowicka 147 , 54-066 Wrocław , Poland.
J Am Chem Soc. 2020 Feb 19;142(7):3626-3635. doi: 10.1021/jacs.9b13942. Epub 2020 Feb 7.
A 139-π-electron nanographenoid radical was obtained by expanding the periphery of a naphthalimide-azacoronene hybrid with a methine bridge. The radical was isolated in the form of its σ-dimer, which was shown to possess a conformationally restricted two-layer structure both in the solid state and in solution. The dimer is cleaved into its parent radicals when exposed to ultraviolet or visible radiation in toluene solutions but is resistant to thermally induced dissociation. Under inert conditions, the radicals recombine quantitatively into the σ-dimer with observable kinetics, but they are oxidized into a ketone derivative in the presence of atmospheric oxygen. Combined structural, spectroscopic, and theoretical evidence shows that the σ-dimer contains a weak C(sp)-C(sp) bond, but is stabilized against thermal dissociation by a very strong dispersive interaction between the overlapping π surfaces.
一个 139-π 电子纳米石墨烯自由基通过扩展一个带有亚甲桥的萘酰亚胺-氮杂冠烯杂化分子的外围而得到。自由基以其 σ-二聚体的形式被分离出来，在固态和溶液中都显示出具有构象受限的双层结构。二聚体在甲苯溶液中暴露于紫外或可见光辐射时会分解成其母体自由基，但对热诱导的离解具有抗性。在惰性条件下，自由基在可观察的动力学下定量地重新组合成 σ-二聚体，但在大气氧存在下，它们会被氧化成酮衍生物。综合结构、光谱和理论证据表明，σ-二聚体含有一个较弱的 C(sp)-C(sp)键，但通过重叠 π 面之间非常强的分散相互作用而稳定，防止了热离解。
