Indian Institute of Science Education and Research, Thiruvananthapuram, Kerala, 695016, India.
Inorganic & Physical Chemistry Division, CSIR-Indian Institute of Chemical Technology (IICT), Tarnaka, Hyderabad, 500007, Telangana, India.
Chemistry. 2019 Feb 21;25(11):2859-2867. doi: 10.1002/chem.201805861. Epub 2019 Jan 29.
The Lewis acid catalyzed self-condensation of hybrid diheterole (furan-pyrrole and thiophene-pyrrole) precursors has afforded novel Hückel antiaromatic 24π hexaphyrin(1.0.1.0.1.0) and 32π octaphyrin(1.0.1.0.1.0.1.0) structures without β-annulated bridges. Single-crystal X-ray diffraction analysis of the hybrid porphyrinoids (S N -ox and O N -ox) revealed a nearly planar conformation and the H NMR spectra suggest the presence of paratropic ring currents. These antiaromatic macrocycles show characteristic optical features and underwent reversible two-electron reduction to Hückel aromatic 26π- and 34π-electron species, respectively, as is evident from the results of spectroscopic and theoretical studies (nucleus-independent chemical shift (NICS) and anisotropy of the current-induced density (ACID) calculations). The incorporation of hybrid diheteroles alternately into expanded porphyrin skeletons provides a novel approach to the fine-tuning of the electronic structures of planar antiaromatic macrocycles.
路易斯酸催化的杂二杂（呋喃-吡咯和噻吩-吡咯）前体的自缩合反应提供了新型的 Hückel 反芳香 24π 六吡咯啉（1.0.1.0.1.0）和 32π 八吡咯啉（1.0.1.0.1.0.1.0）结构，没有β-稠合桥。杂卟啉（S N -ox 和 O N -ox）的单晶 X 射线衍射分析显示出近乎平面的构象，并且 1 H NMR 光谱表明存在反磁环流。这些反芳香大环显示出特征的光学性质，并经历了可逆的两电子还原，分别形成 Hückel 芳香 26π-和 34π-电子物种，这可以从光谱和理论研究（核独立化学位移（NICS）和电流感应密度各向异性（ACID）计算）的结果中明显看出。将杂二杂体交替地引入扩展卟啉骨架中，为平面反芳香大环的电子结构的精细调节提供了一种新方法。
