As such, we first set out to explain the low pKB of 1. In order to do so, we have investigated the thermodynamics of the equilibrium between freebase and protonated macrocycles (Figure ). The presence of electron-poor heterocycle and adjacent amide do not completely account for the reduced basicity of the macrocyclic compound We postulated that the reduction in measured pKB of a functional group involved in a intramolecular interaction can be an indicator of its energetic role in entropic stabilization of conformation and can provide insight into its relevance as a structural pin. In order to address this, we measured the pKB at different temperatures for both 1 as well as the amide containing linear analog (3). From this data one can compose a van't Hoff plot, which provides both the entropy and enthalpy change of the equilibrium. The macrocyclic backbone reduces the entropic term of the free-energy of protonation, whilst at the same time reducing the enthalpic term (Figure ). The change in the entropic factor is, however, greater than the change in the enthalpic one, causing an overall increase in relative ΔG of 1.64 kcal/mol. The reduction in entropy of protonation for macrocycle 1 relative to linear compound 3 suggests that there is a greater increase in available degrees of freedom when 3 is protonated to give 4. This makes sense, as 4 is an unrestricted linear ammonium compound while the ammonium group of 2 is still constrained into a macrocycle scaffold. This result, in correlation with the spectral indicators of increased flexibility illustrated to us that protonation of the amine and the subsequent absence of conformational restriction by the structural pin was associated with a change in conformational entropy. Molecular reorganization of proteins and peptidic molecules upon protonation of sidechains has been previously reported.