Tri-l-valine selenate — study of vibrational spectra and structural phase transition

The addition compound of l-valine and selenic acid was prepared and characterized as tri-l-valine selenate. FTIR and FT Raman spectra of natural and deuterated compounds were measured and interpreted. The results obtained lead to the conclusion that crystal structure is formed by selenate anions, l-valinium cations and l-valine zwitterions (in the ratio of 1:2:1) interconnected by a system of hydrogen bonds. FTIR spectra were studied down to a temperature of 90K. DSC measurements of natural and deuterated compounds were carried out in the temperature range 95–333K. Mechanism of the first-order type low temperature structural phase transition found at 138K is discussed.