STRUCTURE AND IR-SPECTRA OF THE SOLID COMPLEX OF BIS(BETAINE) TELLURIC ACID

Crystals of bis (betaine) -telluric acid of the formula [(CH3)3NCH2CO2]2.Te(OH)6 are triclinic, space group P1BAR, with a = 7.164(5), b = 8.325(5), c = 10.035(6) angstrom, alpha = 108.58(5), beta = 123.82(4), gamma = 96.02(5)-degrees and Z = 1. The crystal structure, solved by the heavy atom method, has been refined to R = 0.0215 for 3887 non-zero reflections. The betaine molecules are linked to telluric acid molecules by three kinds of O...O hydrogen bonds of length 2.561 (4) angstrom, 2.760 (3) angstrom and 2.800 (3) angstrom, respectively. Both species are joined into infinite chains along the a direction. Powder FT-IR spectra of the title crystal and its deuterated analogue at different temperatures have been taken. The broad band at 3116 cm-1 is assigned to the stretching vibrations of the long hydrogen bonds. The two bands at 2671 and 2443 cm-1 are attributed to the stretching vibration of the short hydrogen bond. The internal vibrations of both the tellurate ions and betaine molecules are discussed. An assignment of the bands arising from these vibrations is proposed.