Directionality of Inter- and Intramolecular OHO Hydrogen Bonds: DFT Study Followed by AIM and NBO Analysis

The directionality of inter- and intramolecular OHO hydrogen bonds has been compared. For intramolecular bridges it is determined by an orbital formed in the proton transfer process. For intermolecular bonds, the hydrogen-bonded proton is attached to two lone pairs of the acceptor and the OHO angle is not fixed but can change in a broad range. Depending on the OHO angle, the interaction changes continuously from electrostatic interaction to strong OHO hydrogen bond.