Self-complexing tetrathiafulvalene-based donor-acceptor macrocycles

Two "self-complexing" macrocycles (22ab and 23ab] based on a methylthio-sub stituted derivative of the electron donor tetrathiafulvalene (TTF) and a cy clic bipyridinium acceptor have been prepared.([1]) When "decomplexed" by f ractional crystallization, the rigid compound 22b was not able to undergo " recomplexation" to any significant degree, whereas for the more flexible 23 b, an equilibrium between "complexed" (23a) and "uncomplexed" (23b) compoun ds was slowly re-established in solution according to UV/Vis measurements. 23ab was thus seen to behave as a "thermoswitch", although with a rather sl ow response. Any complexation between the two separated components, i.e. th e cyclic acceptor 3 and the tetrakis(methylthio)-tetrathiafulvalene 6, was not observed by H-1-NMR spectroscopy. However. 3 was able to bind unsubstit uted TTF (5) in its cavity, albeit with a small association constant of onl y 60 M-1. Taking advantage of the tetravalency of TTF, we also report the s ynthesis of a "self-complexing" pyromellitic diimide/TTF macrocycle (33ab). Whereas 22ab and 23ab were prepared employing the concept of template-assi sted synthesis,([2]) the synthesis of 33ab did not rely on this technique.