The Behavior of NH3+ Torsional Vibration in Amino Acids: A Raman Spectroscopic Study

In this work we present the continuation of studies carried out on the changes of geometric parameters of the hydrogen bonds in amino acid crystals subjected to temperature or pressure variations. Changes in geometric parameters of the hydrogen bonds are correlated with the temperature behavior of the Raman wavenumber of NH3+ torsional band. Now four monocrystals, L-valine, L-isoleucine, taurine, and L-arginine hydrochloride monohydrate, are studied. Temperature evolution of the Raman wavenumber of NH3+ torsional band, with positive slope (dν/dT = 0.023 cm−1/K) of L-isoleucine, can be related to the stability of the crystal structure and the hydrogen bonds strengths on heating due to different temperature lattice parameters variation.