Tetrathiafulvalene Radical Cation Dimerization in a Bistable Tripodal [4]Rotaxane
✍ Scribed by Ivan Aprahamian; John-Carl Olsen; Ali Trabolsi; J. Fraser Stoddart
- Publisher
- John Wiley and Sons
- Year
- 2008
- Tongue
- English
- Weight
- 592 KB
- Volume
- 14
- Category
- Article
- ISSN
- 0947-6539
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✦ Synopsis
Abstract
The template‐directed synthesis of a bistable tripodal [4]rotaxane, which has cyclobis(paraquat‐p‐phenylene) (CBPQT^4+^) as the π‐electron‐deficient rings, and tetrathiafulvalene (TTF) and 1,5‐dioxynaphthalene units as the pairs of π‐electron‐rich recognition sites located on all three legs of the tripodal dumbbell, is described. The chemical and electrochemical oxidation of the [4]rotaxane and its tripodal dumbbell have allowed us to unravel an unprecedented TTF^.+^ radical cation dimerization. In fact, two types of TTF dimers, namely, the radical cation dimer [TTF^.+^]~2~ and the mixed‐valence one [(TTF)~2~]^.+^, have been observed at room temperature for the tripodal dumbbell, whereas, in the case of the [4]rotaxane, only the radical cation dimer [TTF^.+^]~2~ is formed. This anomaly can be explained if it is accepted that most of the neutral TTF units in the [4]rotaxane are encircled by CBPQT^4+^ rings, which renders the formation of the mixed‐valence dimer [(TTF)~2~]^.+^ highly unfavorable.