Highly stable tetrathiafulvalene radical dimers in [3]catenanes

Abstract

Two [3]catenane ‘molecular flasks’ have been designed to create stabilized, redox-controlled tetrathiafulvalene (TTF) dimers, enabling their spectrophotometric and structural properties to be probed in detail. The mechanically interlocked framework of the [3]catenanes creates the ideal arrangement and ultrahigh local concentration for the encircled TTF units to form stable dimers associated with their discrete oxidation states. These dimerization events represent an affinity umpolung, wherein the inversion in electronic affinity replaces the traditional TTF-bipyridinium interaction, which is over-ridden by stabilizing mixed-valence (TTF)2•+ and radical-cation (TTF•+)2 states inside the ‘molecular flasks.’ The experimental data, collected in the solid state as well as in solution under ambient conditions, together with supporting quantum mechanical calculations, are consistent with the formation of stabilized paramagnetic mixed-valence dimers, and then diamagnetic radical-cation dimers following subsequent one-electron oxidations of the [3]catenanes. Tetrathiafulvalene (TTF)-based [3]catenanes are shown to display multiple stable redox states dominated by TTF···TTF radical dimer interactions occurring within the cavity of what is essentially a ‘molecular flask’. These stabilizing interactions are found to be the basis of a novel recognition motif that can be employed to drive molecular switching under redox control.

Cite this article

Spruell, J., Coskun, A., Friedman, D. et al. Highly stable tetrathiafulvalene radical dimers in [3]catenanes. Nature Chem 2, 870–879 (2010). https://doi.org/10.1038/nchem.749

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