Potential interaction energy curves of the [Fe(bpy) 3 ] 2+ • • • H 2 O bimolecular system in LS and V min R e V min BLYP HS states were computed individually for an H 2 O in poses A and B. Figure shows the interaction energy results. The first thing we observe when looking at the figure is that all curves produced without accounting for long-range dispersion effects altogether give the largest errors from the DLPNO-CCSD(T) results. Secondly, these errors are more pronounced in pose A than in pose B, indicating that dispersion interactions play a larger role for the pose A geometry. In pose A, the lone pairs on the water oxygen occupy the same regions of space as parts of the π-electron systems from the two pyridine moieties (see figure ), indicating that a significant amount of the interaction must be governed by these interactions. On the other hand, there is only one π-electron system in the vicinity of water in pose B, but the interaction between [Fe(bpy) 3 ] 2+ and H 2 O is stabilized by weak C-H• • • O hydrogen bonding, of which the attractive components are often mostly electrostatic in nature. Consequently, although the Fe-O distance is larger in pose B than that in pose A, the electronic energy of the bimolecular system is lower when the H 2 O is in pose B, making water bind stronger in this pose, regardless of electronic state.