The observed lower basicity of 4c compared with 4b was tentatively rationalised by considering that the protonated bipyridinium is expected to be stabilised by H-bonding to the triazole unit. This effect is likely to be reduced by the increased co-conformational flexibility of 4c, as has been observed in crown ether-ammonium-based rotaxanes. The origin of the lower basicity of 4a appears to run counter to this argument but direct conjugation of the triazole unit with the aromatic ring of the stopper unit can be expected to reduce its basicity and so reduce the favourability of this stabilising interaction. Thus, the lower activity of 4a and 4c compared with 4b appears to be due to the initial step of the reaction, deprotonation of 7 to give carboxylate salt 8, being less favourable in the former cases. Similarly, the lack of activity of 5 under all conditions examined was attributed to the low basicity of the isolated triazole unit.