Relation between the bond lengths in an O-H…O bridge

The data in the literature on the bond lengths of O-H…O bridges formed in organic and inorganic crystals have been analyzed. The results of generalizations of these data on the basis of the generally accepted relation exp(−(r1 − r0/b) + exp(−(r2 − r0/b) = 1 are considered. The factors limiting its application are revealed and its limiting accuracy is estimated. A more universal expression relating the lengths of the same bonds is proposed: exp(−((r1 − r0)/b)h) + exp(−((r2 − r0)/b)h) = 1. On the basis of the generalization of all known neutron diffraction data on bridges with angles exceeding 165°, the coefficients in this relation are determined to be r0 = 0.950 ± 0.005, b = 0.33018 Å, and h = 5/3.