STRUCTURAL CORRELATIONS IN PHENOL-AMINE COMPLEXES

Irena Majerz,

Faculty of Chemistry University of Wroc3aw, 14 Joliot-Curie 14, 50-383 Wroc3aw, Poland

The work is devoted to correlations of the crystal structure parameters of the uniform series of the pentachloro- and 2,6-dichloro-4-nirtophenolate complexes with tertiary amines. The choice of DpK_a range of the complexes ensures a change of the proton transfer degree from molecular complexes with the proton localized at the donor to the ionic complexes with the proton shifted to the acceptor atom through the quasisymmetric hydrogen bonded complexes. They are particularly interesting because of significant shortening of the O^...N bond length. It is found that the proton transfer change is related to the C-O bond length. For the series of investigated complexes the bond lengths and angles are correlated with the C-O bond length to show which of them are the most sensitive to the proton transfer degree.

The change of the proton localization in the hydrogen bridge is reflected in the electronic spectrum changes. For the complexes in solution these changes are described by the tautomeric equilibrium model. In order to describe the proton transfer mechanism it was attempted to registrate and interpretate the solid state UV spectra of a few series of the phenols complexes with tertiary amines.

The IR spectra also show the change depending on the proton localization in the hydrogen bridge. It refers to the intensity and localization of the high frequency stretching vibration band and the low frequency continuous absorption. The correlation of both bands with the DpK_a value allows to fix the range of the complexes with quasisymmetrical hydrogen bonds in the solid state as well as in solutions of varying polarity.