In Set 1, DFT calculations were performed on conformations of 1 c -5 c identical to those observed in their respective X-ray crystal structures (i.e., the Cartesian coordinates of the X-ray structures were used directly in DFT calculations of 1 J CC values without geometry optimizations). In Set 2, DFT calculations were performed on 1 c -5 c as described for Set 1 but first optimizing the hydrogen atoms in each X-ray structure before calculating the 1 J CC values.