Impact of mechanical bonding on the redox-switching of tetrathiafulvalene in crown ether-ammonium rotaxanes
H.V. Schröder, S. Sobottka, M. Nößler, H. Hupatz, M. Gaedke, B. Sarkar, C.A. Schalley – 2017
Switchable crown ether–ammonium rotaxanes with a redox-active tetrathiafulvalene (TTF) unit implemented in their wheels were synthesised and fully characterised. Reversible operation in two modes is possible, in which the rotaxane's axle is either charged or neutral. Cyclic voltammetry experiments reveal the effects of mechanical bonding on the electrochemical properties of TTF and show the rotaxanes to perform a distinct function in both modes. In the charged mode, redox- switching is dominated by strong electrostatic repulsion in the rotaxane which subsequently leads to a macrocycle translation along the axle. In the non-charged mode, a selective energetic stabilisation of TTF radical cations is observed, which can be attributed to an interplay of weak electrostatic interactions between wheel and axle.