Toward a Charged Homo[2]catenane Employing Diazaperopyrenium Homophilic Recognition

• Published in: Journal of the American Chemical Society 2018-05, Vol.140 (21), p.6540-6544
• Main Authors: Gong, Xirui, Zhou, Jiawang, Hartlieb, Karel J, Miller, Claire, Li, Peng, Farha, Omar K, Hupp, Joseph T, Young, Ryan M, Wasielewski, Michael R, Stoddart, J. Fraser
• Format: Article
• Language: English
• Subjects: Chemistry
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.8b03407

An octacationic diazaperopyrenium (DAPP2+)-based homo­[2]­catenane (DAPPHC 8+ ), wherein no fewer than eight positive charges are associated within a mechanically interlocked molecule, has been produced in 30% yield under ambient conditions as a result of favorable homophilic interactions, reflecting a delicate balance between strong π–π interactions and the destabilizing penalty arising from Coulombic repulsions between DAPP2+ units. This DAPPHC 8+ catenane is composed of two identical mechanically interlocked tetracationic cyclophanes, namely DAPPBox4+, each of which contains one DAPP2+ unit and one extended viologen (ExBIPY2+) unit, linked together by two p-xylylene bridges. The solid-state structure of the homo­[2]­catenane demonstrates how homophilic interactions play an important role in the formation of DAPPHC 8+, in which the mean ring planes of the two DAPPBox4+ cyclophanes are oriented at about 60° with respect to each other, with a centroid-to-centroid separation of 3.7 Å between the mean planes of the outer ExBIPY2+ and inner DAPP2+ units, and 3.6 Å between the mean planes of the two inner DAPP2+ units. We show that irradiation of the DAPPHC 8+ catenane at 330 nm in acetonitrile solution results in simultaneous energy and electron transfer. The latter occurs from the inner DAPP2+ dimer to the outer ExBIPY2+ unit, leading to the generation of a temporary charge-separated state within a rigid and robust homo­[2]­catenane. Compared to DAPPBox 4+ , both forward- and back-electron transfer in DAPPHC 8+ occur with faster rates, owing to the closer proximity between the electron donor and acceptor in the homo­[2]­catenane than in the separated cyclophane.