Temperature‐dependent Raman study of taurine single crystal

Abstract

Polarized Raman spectra of an oriented taurine single crystal were studied at temperatures ranging from 7 to 300 K. The results show that several bands present a linewidth increase characteristic of anharmonic effects, and that the band related to the CSH torsional mode splits at low temperatures. An abrupt wavenumber jump of an external mode was associated with a phase transition undergone by the crystal between 250 and 260 K on cooling. A calorimetric investigation over the temperature range 173-308 K confirmed the existence of a first-order phase transition (at 251 K, on cooling), with a temperature hysteresis of 21 K.

Temperature‐dependent Raman study of L‐arginine hydrochloride monohydrate single crystal

“…This is particularly true for the recently studied taurine crystal. 8 However, for the LAHCL crystal the inversion of the band intensity and the behavior of the bands with wavenumbers below 150 cm 1 will be discussed below. Figure 2(b) shows the Raman bands of LAHCL in the spectral region between 1020 and 1245 cm 1 for four selected temperatures.…”

“…However, the Raman scattering experiment, through the observation of changes in the low-wavenumber region (<170 cm 1 ), has been found to be a sensitive probe of phase transitions in amino acid crystals. 8,9,11,15 Figure 4 shows the Raman spectra of LAHCL in the x zz x scattering geometry ( < 135 cm 1 ) taken at four different temperatures. Figure 4(a) shows the Raman spectra between 130 and 170 cm 1 .…”

High temperature Raman spectra of L-leucine crystals

“…On the contrary, taurine crystal is an example where changes in bands associated to internal modes (e.g. torsional vibration of CSH moiety) are effectively related to a structural modification [18]. For Lleucine crystal one observes that at T = 297 K three different bands (up to 150 cm −1 ) are present in the spectrum.…”

Raman spectra of L‐histidine hydrochloride monohydrate crystal

“…For temperatures higher than 300 K, conformational phase transitions are undergone by L-methionine crystal. 17 For temperatures lower than 300 K, structural phase transitions are undergone by L-arginine hydrochloride monohydrate at about 100 K 18 and by taurine crystal at about 250 K. 14 Temperature changes also influence spectroscopic bands related to vibrations of the N-H O complex, as studied for taurine 14 and L-alanine 19 crystals. Figure 4 shows the temperature evolution of the Raman spectra of LHICL for the y(xx)z scattering geometry in the 750-300 cm 1 region.…”

“…In the same temperature range the new peaks L 0 and Q appear. Following the analysis 14,18 common to the behavior of bands at low wavenumbers, we can associate these splittings with a structural phase transition undergone by LHICL.…”