Decomposition of the FES into enthalpic (∆H) and entropic contributions (-T∆S) shows interestingly that the FES landscape (characterized by three minima almost equivalent in ∆G) is the result of a subtle interplay among the two terms (Fig. ). We observe that both enthalpy and entropy tend to favor lateral macrocycle configurations (∆H and -T∆S minima are found at |d| ≳ 0.4 nm). However, there is a clear mismatch between the position of the two red ∆H and blue -T∆S minima: configurations where the macrocycle is localized Also in this case, our analysis on 2 provides detailed insights into the complex interplay between the various factors controlling the motion of the macrocycle (e.g., solvent effects, conformational entropy, intermolecular interactions, . . . ) that are often difficult to elucidate and typically precluded to the experiments. In particular, our analyses show how the fast dynamics of this formamidinium [2]Rotaxane resembles what can be defined as a "Brownian flop-flop" between resonant configurations in a mechanically-interlocked molecule rather than the typical "rigid-like" diffusion process expected in a molecular shuttle.