Binding studies between tetrathiafulvalene derivatives and cyclobis(paraquat-p-phenylene)

The Complexation between a number of different pi -electron donating TTF derivatives and the pi -electron accepting tetracationic cyclophane cyclobis(paraquat-p-phenylene) (CBPQT(4+)) has been studied by H-1 NMR and UV-vis spectroscopy. The results demonstrate that the strength of association between the donors (TTF derivatives) and acceptor (CBPQT(4+))is strongly dependent on the pi -electron donating properties (measured by the first redox potential E-1/2(1)) of the TTF derivatives. However, the first redox potential (E-1/2(1),) is not the only factor of importance. The extended pi -surface of the TTF derivatives also exerts a stabilizing influence upon complexation. The kinetics for the complexation-decomplexation were studied using H-1 NMR spectroscopy and are related to the bulkiness of the TTF derivatives. These effects may serve to improve the: design of interlocked molecular systems, especially (bistable) molecular switches, in which CBPQT(4+) and a derivatized TTF unit are incorporated.