Raman Spectroscopic Study of Centered OHO Hydrogen Bonding in the Hydrogen Maleate Anion

Raman spectra of potassium salts of the protonated K[C₄H₃O₄] and deuterated K[C₄H₂DO₄] maleate anion in the temperature range 5-300 K are presented. It is shown that at low (5 K) temperature roughly half of the protonated and one third of the deuterated H-bonds in maleate anions is extremely strong, the potential curve of the proton (deuteron) is single-well, in which the particles are located at the bond center, and the symmetry of the anions is C_2v. As the temperature increases, the deuterons begin to shift toward one of the oxygen atoms at T > 30 K, and the proton at T > 100 K. At room temperature, the symmetry of both compounds becomes C_1h.