Crystal structure, differential scanning calorimetry and vibrational low temperature investigation of C(NH2)3 x HSeO4

The first X-ray and vibrational spectroscopic analysis of a new molecular complex between guanidinium and selenic acid is reported. The crystal of guanidinium hydrogenselenate at room temperature belongs to P2(1)/n space group of the monoclinic system with Z=4, a=8.330A, b=5.109A, c=14.855A and beta=92.65 degrees . Room temperature powder infrared and Raman spectra for the titled complex (1:1) were measured. The observed IR and Raman spectra are in accordance with this crystallographic structure. The differential scanning calorimetric (DSC) experiment on powder samples indicates on continuous phase transition at ca. 160K. To explain in detail the behavior of the crystal during the phase transition the infrared and Raman powder spectra in low temperature range (10-300K) were measured. The temperature dependencies of bands position and intensities for obtained spectra are analysed.