Crystal structure and vibrational spectra of betaine hydrogen selenate monohydrate

The crystal structure of betaine hydrogen selenate monohydrate, (C5H12NO2)(+).(HSeO4)(-).(H2O), BHSeH2O, has been determined by X-ray diffraction 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 comprises protonated betaine moieties (betainium cations), hydrogen selenate anions and water molecules which are held together by a number of hydrogen bonds and form infinite chains. Two types of four-membered centrosymmetric rings are distinguished in the chain. The two rings share 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 bands to vibrations of the hydrogen bonds and internal vibrations of the hydrogen selenate anions and the betainium cations are proposed. DSC data are also presented.