High pressure studies on bis (L-histidinate) nickel (II) monohydrate

Abstract Raman spectra of bis( l -histidinate)nickel(II) monohydrate crystal were obtained for pressures up to 9.5 GPa. Our results show the disappearance of some of the Raman modes and the appearance of other modes. These modifications evidence that the sample undergoes phase transitions at around 0.8 and 3.2 GPa. The role played by the Ni ions and hydrogen bonds in the dynamics of the phase transitions is discussed. Under decompression, down to atmospheric pressure, the original Raman spectra are recovered, showing that both phase transitions are fully reversible.