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Published July 30, 2014 | Supplemental Material
Journal Article Open

Solid-State Characterization and Photoinduced Intramolecular Electron Transfer in a Nanoconfined Octacationic Homo[2]Catenane


An octacationic homo[2]catenane comprised of two mechanically interlocked cyclobis(paraquat-p-phenylene) rings has been obtained from the oxidation of the septacationic monoradical with nitrosonium hexafluoroantimonate. The nanoconfinement of normally repulsive bipyridinium units results in the enforced π-overlap of eight positively charged pyridinium rings in a volume of <1.25 nm^3. In the solid state, the torsional angles around the C–C bonds between the four pairs of pyridinium rings range between 16 and 30°, while the π–π stacking distances between the bipyridinium units are extended for the inside pair and contracted for the pairs on the outside—a consequence of Coulombic repulsion between the inner bipyridinium subunits. In solution, irradiation of the [2]catenane at 275 nm results in electron transfer from one of the paraphenylene rings to the inner bipyridinium dimer, leading to the generation of a temporary mixed-valence state within the rigid and robust homo[2]catenane.

Additional Information

© 2014 American Chemical Society. Received: May 21, 2014; Published: July 10, 2014. This material is based on work supported by the National Science Foundation (NSF) under CHE-1308107. This research is part of the Joint Center of Excellence in Integrated Nano-Systems (JCIN) at King Abdul-Aziz City for Science and Technology (KACST) and Northwestern University (Project 34-947). The authors would like to thank both KACST and Northwestern University (NU) for their continued support of this research. J.C.B. was supported by a National Defense Science and Engineering Graduate Fellowship from the Department of Defense and gratefully acknowledges support from a Ryan Fellowship awarded under the auspices of the NU International Institute of Nanotechnology (IIN). This work was supported by the Chemical Sciences, Geosciences, and Biosciences Division, Office of Basic Energy Sciences, DOE under grant no. DE-FG02-99ER14999 (M.R.W.). Femtosecond spectroscopy (R.M.Y.) was available as part of the ANSER Center, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under award no. DE-SC0001059. W.G.L. and W.A.G. thank NSF (CMMI-1120890 and EFRI-1332411) for financial support and to ONR-DURIP and NSF-CSEM for computing resources.

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