2,5‐Thienylene‐Strapped Bicyclic and Tricyclic Expanded Porphyrins

• Published in: ChemPlusChem (Weinheim, Germany) Germany), 2019-07, Vol.84 (7), p.810-815
• Main Authors: Abdisa Kerayu, Bulti, Ching, Wei‐Min, dela Cruz, Jay‐ar, Hung, Chen‐Hsiung
• Format: Article
• Language: English
• Subjects: aromaticity; hexaphyrins; macrocycles; porphyrinoids; thiaporphyrins
• ISSN: 2192-6506; 2192-6506
• DOI: 10.1002/cplu.201900013

An [18]thiaporphyrin[36]dithiaoctaphyrin‐[18]thiaporphyrin tricyclic macrocycle, fused through the 2,5‐thienylene bridging moiety, was isolated during the preparation of 2,5‐thienylene‐strapped [26]hexaphyrin containing o‐dichlorophenyl groups as meso substituents. The spectroscopic data of the 2,5‐thienylene‐strapped [26]hexaphyrin verified contributions of aromaticity from ring currents of both the [18]thiaporphyrin and the [26]hexaphyrin. The crystal structure of the tricyclic macrocycle revealed a distorted [36]dithiaoctaphyrin central core with two [18]thiaporphyrin sidewheels oriented nearly perpendicular to the mean‐plane of dithiaoctaphyrin, implying the existence of independent π‐conjugated systems. Both the absorption maximum at 441 nm and the chemical shifts in the 1H NMR spectrum of the tricyclic macrocycle are dominated by diatropic ring currents of two aromatic [18]thiaporphyrin sidewheels. Continuous expansion: The reaction of o‐dichlorophenyl‐substituted tripyrromethane and diformylthiophene resulted in the formation of two thiophene‐strapped expanded porphyrins. While the bicyclic hexaphyrin demonstrates dual aromaticity resulting from both the thiaporphyrin and hexaphyrin rings, the tricyclic molecule fuses a non‐aromatic [36]dithiaoctaphyrin and two aromatic [18]thiaporphyrin side‐wheels.