Intercalation of tetrathiafulvalene between the two plates of a copper(I)-complexed [4]rotaxane

The ability of a cyclic copper(I)-complexed [4]rotaxane to act as a receptor towards organic electron donors has been studied. In particular, tetrathiafulvalene (TTF), which is a flat and electron-rich molecule, forms a relatively stable complex with the rotaxane host. 1H NMR spectroscopic measurements strongly suggest that the coordination mode involves intercalation of the TTF motif between the two electron-poor plates of the [4]rotaxane. By contrast, extended TTF (exTTF), which possesses π-donating ability similar to that of TTF but which is a significantly bulkier molecule due to a concave structure, was not able to form any detectable complex. This observation tends to indicate that the recognition site of the [4]rotaxane receptor is rigid and can not adapt to thick substrates