Correlations between ab initio and experimental data for isolated 1 : 1 hydrogen-bonded complexes of pyridine and imidazole derivatives with water

Correlations between selected ab initio predicted and experimentally observ ed properties of 1:1 H-bonded complexes of a series of pyridine derivatives with water are investigated. Specifically, relationships are found between the experimentally observed properties of proton affinity, frequency shift , and dipole moments, and the ab initio calculated values of bond distance, interaction energy, frequency shift, LR absorption intensity and charge di fferences obtained from Mulliken population analysis. The examined correlat ions were then compared with data collected for pyridine-H2O and imidazole- H2O complexes. Similarities were found between the correlations in the theo retically determined properties and the correlations in experimentally obse rved parameters. It was also found that well-defined relations could be est ablished between the calculated and observed properties for the pyridine de rivatives, but these could not be reliably extended to the imidazole system s. These similarities demonstrate that the presently available ab initio ca lculations are useful predictors of experimental behavior of H-bonded syste ms but only for chemically closely related molecules. (C) 1999 Elsevier Sci ence B.V. All rights reserved.