Carbazole‐Containing Carbadecaphyrins: Non‐aromatic Expanded Porphyrins that Undergo Proton‐Triggered Conformational Changes
Weinan Zhou, Mengdi Hao, Tian Lu, Zhiming Duan, Tridib Sarma, Jonathan L. Sessler, Chuanhu Lei
Abstract
Abstract A pair of meso ‐unsubstituted expanded carbaporphyrins containing two carbazole moieties were prepared in high isolated yields (82 and 76 %, respectively). The two macrocycles, namely 3 and 4 , differ with respect to their substitution at the carbazole N‐atoms i. e. by H and i ‐Bu, respectively. As prepared in their free‐base forms, macrocycles 3 and 4 adopt figure‐of‐eight conformations and are best characterized as 40 π‐electron, non‐aromatic species possessing a decaphyrin(1.1.0.0.0.1.1.0.0.0) skeleton. Protonation of 3 with either trifluoroacetic acid (TFA) or perchloric acid (HClO 4 ) produces a parallelogram‐shaped structure. A similar structure is produced when N‐functionalized system 4 is treated with TFA. In contrast, protonation of 4 with HClO 4 leads it to adopt a twisted Möbius strip‐like structure in the solid state, thus allowing access to three distinct conformational states as a function of the conditions.