NATURE OF CONTINUOUS ABSORPTION IN IR-SPECTRA OF CHARGED COMPLEXES WITH A SYMMETRICAL HYDROGEN-BOND

For the first time absorption spectra of H5O2+, D5O2+, (CH3OH)2H+, H3O2-, D3O2- and (CH3O)2H- ions are extracted from IR spectra of solutions of acids and strong bases and detailed theoretical analysis of these spectra is performed with due regard for the kinematic, dynamic and electro-optical anharmonicities of vibrations. The set of ions chosen for the study provided the possibility to compare the spectra of positively and negatively charged ions, of an ion and its isotopically different analogue and of hydrated and solvated proton forms. A good agreement between the calculated and experimental data, without using any kind of fitting, indicates that the model proposed for description of any-strength hydrogen-bond spectral properties is applicable for spectra calculation of systems containing strong (about 32 kcal mol-1) H bonds. This agreement is also a direct proof (in terms of molecular structure approach) for complexes of the type (A...H...A)+/- to be the simplest stable proton and hydroxyl ion solvates in solutions of acids and strong bases. This study elucidates the origin and mechanisms of the continuous absorption in IR spectra of ions with symmetric hydrogen bonds and shows that the constancy of the O...H...O group properties in all systems containing this group can be a basis for creating a unified catalytic action theory of acids and bases.