Zissimou Georgia A, Bartos Paulina, Pietrzak Anna, Kaszyński Piotr
Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, 90-363 Łódź, Poland.
Faculty of Chemistry, University of Łódź, 91-403 Łódź, Poland.
J Org Chem. 2022 Apr 1;87(7):4829-4837. doi: 10.1021/acs.joc.2c00178. Epub 2022 Mar 15.
Photocyclization of 8-aryloxybenzo[][1,2,4]triazines leads to the formation of π-expanded flat Blatter radicals for three phenanthryloxy and pyren-1-yloxy derivatives, whereas no photoreaction is observed for the perylen-3-yloxy precursor. Two of the new radicals are nonplanar, out of which one is unstable to isolation. The radical with the fused pyrene ring constitutes the largest thus far paramagnetic polycyclic π-system containing seven fused rings with 27 sp-hybridized atoms and 29 π-delocalized electrons. The investigation of the reaction conditions demonstrated the higher efficiency of photoformation of the parent radical in polar solvents, which suggests a polar transition state and the S photoreactive state. The effect of π expansion on the electronic structure was investigated with spectroscopic (UV-vis, electron paramagnetic resonance) and electrochemical methods augmented with density functional theory computational studies. The molecular structure of one of the radicals was determined with a single-crystal X-ray diffraction method.
8-芳氧基苯并[][1,2,4]三嗪的光环化反应，对于三种菲氧基和芘-1-氧基衍生物会生成π扩展的平面布拉特自由基，而对于苝-3-氧基前体则未观察到光反应。其中两个新自由基是非平面的，其中一个不稳定，无法分离。带有稠合芘环的自由基构成了迄今为止最大的顺磁多环π体系，包含七个稠合环，有27个sp杂化原子和29个π离域电子。对反应条件的研究表明，在极性溶剂中母体自由基的光生成效率更高，这表明存在极性过渡态和S光反应态。通过光谱法（紫外可见光谱、电子顺磁共振）和电化学方法，并结合密度泛函理论计算研究，研究了π扩展对电子结构的影响。其中一个自由基的分子结构通过单晶X射线衍射法确定。
