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

The Complexation between a number of different pi -electron donating TTF de rivatives and the pi -electron accepting tetracationic cyclophane cyclobis( paraquat-p-phenylene) (CBPQT(4+)) has been studied by H-1 NMR and UV-vis sp ectroscopy. The results demonstrate that the strength of association betwee n the donors (TTF derivatives) and acceptor (CBPQT(4+))is strongly dependen t on the pi -electron donating properties (measured by the first redox pote ntial 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 complexatio n. The kinetics for the complexation-decomplexation were studied using H-1 NMR spectroscopy and are related to the bulkiness of the TTF derivatives. T hese effects may serve to improve the: design of interlocked molecular syst ems, especially (bistable) molecular switches, in which CBPQT(4+) and a der ivatized TTF unit are incorporated.