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 homocatenane composed of two rigid and fixed cyclobis (paraquat-p- phenylene) rings. The highly energetic octacationic homocatenane, 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.
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