Fig. 2. Acid–base control of the position of the macrocycle in rotaxane 1 (iminium catalysis ‘on’; hydrogen bond catalysis ‘off’)/1-H⁺·CF₃CO₂ ^– (iminium catalysis ‘off’; hydrogen bond catalysis ‘on’) and the structure of the corresponding thread 2-H⁺·CF₃CO₂ ^– (both iminium catalysis and hydrogen bond catalysis ‘on’).