CRYSTAL-STRUCTURE AND VIBRATIONAL-SPECTRA OF BETAINE HYDROGEN SELENATE MONOHYDRATE

The crystal structure of betaine hydrogen selenate monohydrate, (C5H12 NO2)(+).(HSeO4)(-).(H2O), BHSeH2O, has been determined by X-ray diffra ction as monoclinic, space group P2(1)/c with a = 6.674(6), b = 11.912 (9), c = 14.156(14) Angstrom, beta = 100.61(4)degrees and Z = 4. It co mprises protonated betaine moieties (betainium cations), hydrogen sele nate anions and water molecules which are held together by a number of hydrogen bonds and form infinite chains. Two types of four-membered c entrosymmetric rings are distinguished in the chain. The two rings sha re a common side. Powder FT-IR and FT-Raman spectra were measured for the title crystal, the dehydrated crystal (betaine hydrogen selenate, BHSe) and their deuterated analogues. Assignments of the observed band s to vibrations of the hydrogen bonds and internal vibrations of the h ydrogen selenate anions and the betainium cations are proposed. DSC da ta are also presented.