Deterioration of the Symmetry of Strong Hydrogen Bond between ClO_4~- and HclO_4 under the Influence of the Bu_4N~+ Cation in a Solvated Contact Ion Pair as Probed by IR and Raman Spectroscopy

摘要

Liquid and glassy solutions of the complexes Bu_4NClO_4 centre dot HClO_4 and Bu_4NClO_4 centre dot DClO_4 in dichloroethane, chloroform, carbon tetrachloride, and benzene (concentration 27-75 percent) were studied by IR and Raman spectroscopy. Broad structured absorption bands due to strong hydrogen bonds and narrow bands due to ClO bonds were found. In the liquid phase, the peak frequencies #nu#(OH) and #nu#(OD) are 2450+-50 and 1890+- 20 cm~(-1), respectively; upon glass transition, they decrease, on the average, by 100 cm~(-1). The bands of the triply degenerate vibrations of the perchlorate ion are split due to H-bonding between ClO_4~- and the hydrogen of HClO_4 or the deuterium of DClO_4. The pattern of splitting attests to a monodentate coordination of the perchlorate ion by the H and D atoms. No noticeable indications of a change in the symmetry of the perchlorato group and HClO_4 or DClO_4 molecules are detected in the IR or Raman spectra of liquid solutions. With allowance made for the structural nonequivalence of the monodentate perchlorato groups belonging to the perchlorate ion and to the acid molecule, a nonsymmetrical H-bond (O-H…O or O-D…O) was identified. The nonsymmetrical perchlorato complex serves as a component of contact ion pairs Bu_4N~+(O_3ClO centre dot HOClO_3)~- and Bu_4N~+(O_3ClO centre dot DOClO_3)~-. The low symmetry of the complex is due to the presence of the easily polarizable H-bond and to the polarizing influence of Bu_4N~+.