[2]Rotaxanes 4 were prepared using an active template 23 Cu-mediated alkyne-azide cycloaddition (AT-CuAAC) 24 reaction. (Scheme 1). Our expectation was that the bipyridine-triazole cavity produced in the AT-CuAAC approach would act as a Brønsted base, and that the short alkyl linker between the NDI unit and triazole would facilitate π-π stacking of the bipyridine and NDI units. Rotaxane 6, which lacks the NDI unit, was synthesized using a similar strategy for comparison (see ESI). Rotaxanes 4, axle 5 and rotaxane 6 were fully characterized by NMR and MS (see ESI). Comparison of the 1 H NMR spectra of rotaxanes 4 revealed that although the triazole proton Hi resonance appears at high ppm in all cases, as presumably due to C-H•••N H-bonding between the triazole and bipyridine unit 24b,c,26 (Figure ), it appears at progressively lower chemical shift in the series 4a-4c (10.2, 9.4 and 9.1 ppm respectively, Figure ). This effect was tentatively assigned to increased co-conformational freedom as the axle length is increased. Single crystal X-ray diffraction (SCXRD) analysis of 4a confirmed its interlocked nature and the proposed C-H•••N interaction between the bipyridine Ns and Hi alongside other weak interactions, and reveals the anticipated π-π stacking interaction between the macrocycle bipyridine and axle NDI (Figure ). The performance of rotaxanes 4 as anion-π catalysts was assessed through their performance in the Michael addition of malonic acid half-thioester 7 to -nitrostyrene (11) (Table , entries 2-4), a key benchmarking reaction in anion- catalysis. 9d Under Brønsted base catalysis, the major product of this reaction is thioester 10, the product of deprotonation and subsequent decarboxylation of 7, whereas in the presence of an anion- catalyst planar enolate 9 is stabilized in the equilibrium, allowing the addition/decarboxylation product 12 to form preferentially. Broadly speaking, the key parameters that determine catalyst performance are thus Brønsted basicity (determines position of the equilibrium between 7 and 8 and thus significantly affects rate) and the ability of the catalyst to stabilise 9 and the subsequent transition state leading to 12 (determines selectivity). Reactions mediated by NEt3 (entry 1), macrocycle 1 (entry 5), an equimolar combination axle 5 and macrocycle 1 (entry 6), axle 5 alone and rotaxane 6 were also assessed for comparison. The key conclusions of this study are i) 4b is an effective anion- catalyst (entry 3), delivering 12 selectively in THF at 30 °C (12 / 10 = 4.4) and with enhanced activity (16 h vs 60 h for >95% conversion) and selectivity (11.9) in CDCl3, which was improved further at lower temperature (46.2); ii) rotaxanes 4a and 4c (entries 2 and 4 respectively) display reduced activity and slightly reduced selectivity compared with 4b in CDCl3 and no activity over 16 h in THF; iii) non-interlocked macrocycle 1 (in CDCl3, entry 5) and rotaxane 6 (in THF or CDCl3, entry 8), both of which lack an NDI unit, are active catalysts, albeit less selective than rotaxanes 4; iv) 4b and 6 display similar catalytic activity; v) NDI axle 5 is not a competent catalyst and combining 1 and 5 results in the same outcome as 1 alone.