Theoretical and experimental studies of the barrier to amine rotation in creatinine: Influence of solvation models and explicit solvation

The barrier to rotation about the C-N(H2) bond in creatinine in aqueous environments has been studied experimentally, by means of NMR spectroscopy, and theoretically, employing a number of models based upon explicit solvation and continuum descriptions. The measured barrier to rotation (13kcal mol-1) is obtained only if an explicit solvent is included in calculations on a supermolecule model; the use of a continuum model alone predicts a barrier (9 kcal mol-1), considerably smaller than the experimental value.