The minimum energy structures of rotaxanes 4a and 4b (Figure ) were both found to be arranged such that a π-π stacking interaction was maintained between the bipyridine and NDI units, and a C-H•••N interaction was present between the bipyridine unit and the triazole C-H, as observed in the solid-state structure of 4a (Figure ). Protonated 4aH + and 4bH + structures (Figure ) were found to maintain the NDI-pyridine stacking interaction but, in this case, the protonated bipyridine unit engages in an H-bond with the triazole unit. This prediction is corroborated by a SCXRD structure of 4aH + (Figure ) obtained during catalysis screening experiments (see ESI section S3.2 for details); the predicted π-π stacking interactions and N-H•••N H-bond are both observed in the solid state. In keeping with our experimental observations, the pKa difference between 4a and 4b was computed to be 1.47 units in THF and 1.35 units in CHCl3 (ESI section 7.3). This was attributed to a stronger N•••H bond formed in protonated 4b, with a shorter distance and better directionality, combined with the lower basicity of the triazole unit when it is directly bonded to phenyl (ESI section S7.3).