On the Correlation between the Blue Shift of Hydrogen Bonding and the Proton Donor-Proton Acceptor Distance

It is demonstrated that in all types of hydrogen bonds (X—H…Y) there is a balance between the long-range attractive orbital interactions and short-range Pauli/nucleus repulsions. When the proton acceptor approaches the proton donor from distance, the hydrogen bonding energy becomes more negative at relatively large distance, goes through a minimum, and then starts to become less negative when the short-range repulsive forces come into effect.Meanwhile, the X--H bond length increases at relatively large distances, goes through a maximum and starts to shorten when the short-range repulsive forces come into effect. Whether the hydrogen bond is red or blue shifted is dictated by the energy minimum position. If at the energy minimum position the X—H bond length is shorter than that for the free monomer, the hydrogen bond is blue shifted and vice versa. Further studies demonstrate that the recent report about the correlation of C—H bond lengths with proton donor-acceptor distance in F3C—H…OH2 and F3C—H…Cl^- is not fully correct because the authors conducted an inappropriate comparison. Furthermore, it is shown for the first time that the Pauli/nucleus repulsion theory is applicable to the blue-shifted hydrogen bonds in the X—H…π complexes and the blue-shifted lithium bonds in the X—Li…Y complexes.

On the Correlation between the Blue Shift of Hydrogen Bonding and the Proton Donor-Proton Acceptor Distance

It is demonstrated that in all types of hydrogen bonds (X? H···Y) there is a balance between the long‐range attractive orbital interactions and short‐range Pauli/nucleus repulsions. When the proton acceptor approaches the proton donor from distance, the hydrogen bonding energy becomes more negative at relatively large distance, goes through a minimum. and then starts to become less negative when the short‐range repulsive forces come into effect Meanwhile, the X? H bond length increases at relatively large distances, goes through a maximum and starts to shorten when the short‐range repulsive forces come into effect. Whether the hydrogen bond is red or blue shifted is dictated by the energy minimum position. If at the energy minimum position the X? H bond length is shorter than that for the free monomer, the hydrogen bond is blue shifted and vice versa. Further studies demonstrate that the recent report about the correlation of C? H bond lengths with proton donor‐acceptor distance in F₃C? H···OH₂ and F₃C? H···Cl is not fully correct because the authors conducted an inappropriate comparison. Furthermore, it is shown for the first time that the Pauli/nucleus repulsion theory is applicable to the blue‐shifted hydrogen bonds in the X? H···π complexes and the blue‐shifted lithium bonds in the X? Li···Y complexes.