Toward a General Theory of Hydrogen Bonding: The Short, Strong Hydrogen Bond [HOH···OH]-

The method of localized charge distributions is used to analyze the difference in hydrogen bond strength between HOH···OH 2 and [HOH···OH] - in terms of the competition between the electronic kinetic energy and potential energy. The main source of the difference is the relatively larger decrease in the intermolecular energy for the latter complex, due to the net charge and a more polar accepting lone pair. The decrease is interpreted semiquantitatively by using bond and lone pair dipoles. The shortening of the OO distance and the lengthening of the donating O−H bond are both shown to occur as a result of the stronger attraction. Implications for other short strong hydrogen bonds are discussed.