Department of Chemistry, Kangwon National University, Chuncheon, 24341, Korea.
Department of Chemistry, The University of Texas at Austin, Austin, TX, 78712-1224, USA.
Chemistry. 2019 Mar 7;25(14):3525-3531. doi: 10.1002/chem.201900022. Epub 2019 Feb 13.
Peripherally substituted antiaromatic naphthorosarins have been synthesized for the first time. The synthesis was accomplished by acid-catalyzed condensation of naphthobipyrrole building blocks with aromatic aldehydes. The naphthobipyrrole building blocks were synthesized by simple oxidative coupling of the corresponding pyrrole substituted aromatics. Solid-state structural analyses of the synthesized naphthorosarins revealed that the presence of meso-2,6-dichlorophenyl- and 5,6-difluoro-substitution substantially alter the geometry and properties of the naphthorosarins. The substituents affect the redox potentials as well and, in turn, the proton-coupled electron-transfer processes leading to the formation of one- and two-electron reduced forms of the corresponding naphthorosarins. One particular naphthorosarin that bears both peripheral fluorine and meso-2,6-dichlorophenyl substituents forms a stable 25 π-electron species upon treating with TFA that was characterized by single-crystal X-ray diffraction analysis. The current study underscores how structural modifications can be used to fine-tune the electronic features of naphthorosarins, including stabilization of odd electron species.
首次合成了具有取代基的芳环稠合萘并吖啶啉。该合成是通过酸催化缩合萘并双吡咯砌块与芳香醛来完成的。萘并双吡咯砌块是通过相应的吡咯取代芳烃的简单氧化偶联合成的。合成的萘并吖啶啉的固态结构分析表明，间位-2,6-二氯苯基和 5,6-二氟取代基的存在极大地改变了萘并吖啶啉的几何形状和性质。取代基也会影响氧化还原电位，从而影响质子耦合电子转移过程，导致相应的萘并吖啶啉形成一电子和二电子还原形式。一个特别的萘并吖啶啉，它同时具有外围氟和间位-2,6-二氯苯基取代基，在与 TFA 处理后形成一个稳定的 25π 电子物种，这通过单晶 X 射线衍射分析得到了证实。本研究强调了结构修饰如何用于微调萘并吖啶啉的电子特性，包括稳定奇数电子物种。
