STRUCTURE AND VIBRATIONAL-SPECTRA OF THE BIS(BETAINE)-SELENIC ACID MOLECULAR-CRYSTAL

The crystal structure of bis(betaine)-selenic acid has been determined by X-ray diffraction as orthorhombic, space group Pbca, with a = 11.5 91(2), b = 22.930(5), c = 12.045(2) Angstrom and Z = 8. The crystal co mprises hydrogen selenate ions, HSeO4-, and two distinct betaine molec ules, which are held together into a complex by short hydrogen bonds. One of the betaine molecules is present as the zwitterion form (CH3)(3 )N+-CH2-COO- and the second occurs as the protonated form (CH3)(3)N+-C H2-COOH. Powder FTIR and Raman spectra were measured. An assignment of the observed bands to vibrations of the hydrogen bonds and internal v ibrations of. the hydrogen selenate ion and the betaine molecules is p roposed. (C) 1997 Elsevier Science B.V.