To identify the local conformer of the isolated molecule from the observed crystal structures in the conformational landscape, geometric comparisons with the sets of conformers were performed. The difference in energy between the lowest energy generated conformer (the global energy minimum conformer), E GM , and the energy of the local conformer corresponding to the crystalline molecular geometry, E opt,mol local , is referred to as the conformational energy, ∆E con f (see Fig. and Eq. 2):