A Radically Configurable Six-State Compound

Creators: Barnes, Jonathan C.; Fahrenbach, Albert C.; Cao, Dennis; Dyar, Scott M.; Frasconi, Marco; Giesener, Marc A.; Benítez, Diego; Tkatchouk, Ekaterina; Chernyashevskyy, Oleksandr; Shin, Weon Ho; Li, Hao; Sampath, Srinivasan; Stern, Charlotte L.; Sarjeant, Amy A.; Hartlieb, Karel J.; Liu, Zhichang; Carmieli, Raanan; Botros, Youssry Y.; Choi, Jang Wook; Slawin, Alexandra M. Z.; Ketterson, John B.; Wasielewski, Michael R.; Goddard, William A., III; Stoddart, J. Fraser

Abstract

Most organic radicals possess short lifetimes and quickly undergo dimerization or oxidation. Here, we report on the synthesis by radical templation of a class of air- and water-stable organic radicals, trapped within a homo[2]catenane composed of two rigid and fixed cyclobis (paraquat-p-phenylene) rings. The highly energetic octacationic homo[2]catenane, which is capable of accepting up to eight electrons, can be configured reversibly, both chemically and electrochemically, between each one of six experimentally accessible redox states (0, 2+, 4+, 6+, 7+, and 8+) from within the total of nine states evaluated by quantum mechanical methods. All six of the observable redox states have been identified by electrochemical techniques, three (4+, 6+, and 7+) have been characterized by x-ray crystallography, four (4+, 6+, 7+, and 8+) by electron paramagnetic resonance spectroscopy, one (7+) by superconducting quantum interference device magnetometry, and one (8+) by nuclear magnetic resonance spectroscopy.

Additional Information

© 2013 American Association for the Advancement of Science. Received 6 August 2012; accepted 5 November 2012. The data reported in this paper are tabulated in the supplementary materials, and the crystallographic parameters of each single crystal were deposited into the Cambridge Crystallographic Data Centre, where they are freely available under reference numbers 855030, 855031, 855032, and 889233. We thank S. Shafaie for his expertise and assistance with high-resolution mass spectrometry, and the Integrated Molecular Structure Education and Research Center at Northwestern University for providing access to equipment for the relevant experiments. Molecular crystal images were produced using the UCSF Chimera package from the Resource for Biocomputing, Visualization, and Informatics at the University of California, San Francisco. The authors acknowledge our joint collaborators Turki S. Al-Saud and M. B. Alfageeh from the King Abdulaziz City of Science and Technology in Saudi Arabia. J.F.S. is supported by the Non-Equilibrium Energy Research Center, which is an Energy Frontier Research Center (EFRC) funded by the U.S. Department of Energy, Office of Basic Energy Sciences (DOE-BES) under award DESC0000989. R.C. is supported by the Argonne-Northwestern Solar Energy Research Center, which is an EFRC funded by DOE-BES under award DE-SC0001059. M.R.W. and S.M.D. are supported by the U.S. National Science Foundation under grant CHE-1012378. J.C.B. was supported by a National Defense Science and Engineering Graduate Fellowship from the U.S. Department of Defense (DOD) and gratefully acknowledges support from the Ryan Fellowship (as does D.C.) awarded under the auspices of the Northwestern University International Institute for Nanotechnology, as well as the DOD award W911NF-10-1-0510 and the DOE-BES under award DE-SC0005462. A.C.F. and D.C. are supported by a Graduate Research Fellowship from the National Science Foundation. M.A.G. was supported by a Summer Undergraduate Research Fellowship from the American Chemical Society. J.F.S., D.B., E.T., and W.A.G. are funded through the Focus Center Research Program Center on Functional Engineered Nano Architectonics. J.F.S. and A.M.Z.S. were supported under the auspices of an international collaboration supported in the United States by the NSF under grant CHE-0924620 and in the United Kingdom by the Engineering and Physical Sciences Research Council under grant EP/H003517/1. J.C.B., A.C.F., D.C., W.A.G., and J.F.S. are also supported by the World Class University program (R-31-2008-000-10055-0) funded by the Ministry of Education, Science and Technology, Republic of Korea.

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