Hydrogen-bonding interactions in fully deuterated α-glycine at high pressures

Abstract

Recent spectroscopic investigations of various amino acids report intriguing high-pressure and low-temperature behavior of NH₃⁺ groups and their influence on various hydrogen bonds in the system. In particular, the variation of the intensity of NH₃⁺ torsional mode at different temperatures and pressures has received much attention. We report here the first in situ Raman investigations of fully deuterated -glycine up to -20 GPa. The discontinuous changes in COO^- and ND₃⁺ modes across -3 GPa indicate subtle structural rearrangements in fully deuterated α-glycine. The decrease in the intensity of ND₃⁺ torsional mode is found to be similar to that of undeuterated α-glycine. The pressure-induced stiffening of ND and CD₂ stretching modes are discussed in the context of changes in the hydrogen-bonding interactions.