Low-wavenumber Raman spectra of L-tyrosine, L-tyrosine hydrochloride, and L-tyrosine hydrobromide crystals at high temperatures

Article abstract of DOI:10.1016/j.jpcs.2019.109129

Crystals of L-tyrosine and semiorganic L-tyrosine hydrochloride and L-tyrosine hydrobromide, known for their nonlinear optical properties, were studied by Raman spectroscopy in the temperature range from 298 to 453 K. Hydrogen bonding at room temperature

Full text of DOI:10.1016/j.jpcs.2019.109129

Journal Pre-proof
Low-wavenumber Raman spectra of l-tyrosine, l-tyrosine hydrochloride, and l-tyrosine
hydrobromide crystals at high temperatures
C.A.A.S. Santos, R.J.C. Lima, P.F. Façanha Filho, A.O. dos Santos, J.A. Lima, Jr.,
P.T.C. Freire
PII:
S0022-3697(18)32523-X
https://doi.org/10.1016/j.jpcs.2019.109129
PCS 109129
DOI:
Reference:
To appear in: Journal of Physics and Chemistry of Solids
Received Date: 20 September 2018
Revised Date: 1 August 2019
Accepted Date: 2 August 2019
Please cite this article as: C.A.A.S. Santos, R.J.C. Lima, P.F.Faç. Filho, A.O.d. Santos, J.A. Lima Jr.,
P.T.C. Freire, Low-wavenumber Raman spectra of l-tyrosine, l-tyrosine hydrochloride, and l-tyrosine
hydrobromide crystals at high temperatures, Journal of Physics and Chemistry of Solids (2019), doi:
https://doi.org/10.1016/j.jpcs.2019.109129.
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1
Low-wavenumber Raman spectra of
L-tyrosine,
L-tyrosine hydrochloride, and
L-tyrosine
hydrobromide crystals at high temperatures
C.A.A.S. Santosa,b*, R.J.C. Limaa, P.F. Façanha Filhoa, A.O. dos Santosa, J.A.
Lima Jr.c, P.T.C. Freirec
aCentro de Ciências Sociais, Saúde e Tecnologia, Universidade Federal do
Maranhão, Imperatriz – MA, 65900-410, Brazil
bCentro de Ciências Humanas Sociais Tecnologias e Letras, Universidade
Estadual da Região Tocantina do Maranhão, Açailândia – MA, 65930-000, Brazil
cDepartamento de Física, Universidade Federal do Ceará, Fortaleza – CE,
60455-760, Brazil
Abstract
Crystals of
L-tyrosine and semiorganic L-tyrosine hydrochloride and L-tyrosine
hydrobromide, known for their nonlinear optical properties, were studied by Raman
spectroscopy in the temperature range from 298 to 453 K. Hydrogen bonding at room
temperature and thermal decomposition are correlated with Raman bands in the low-
wavenumber region at approximately 120 cm-1. The detailed analysis of these bands and
the temperature dependence of their wavenumbers show an interesting correlation
between hydrogen bonds, vibrational properties, and thermal decomposition. In
particular, we note a correlation between the lengths of the N–H•••X bonds and the
wavenumber of a low-wavenumber band and that the introduction of Br and Cl in the
tyrosine hydrochloride and -tyrosine hydrobromide structures does not substantially
modify the O–H•••O bonds when compared with the -tyrosine crystal. Additionally,
L-
L
L
the hydrophobic character of the interactions apparently does not change during heating,
and there is no evidence for the breakdown of the hydrophobic interactions.
Keywords: -Tyrosine; Thermal decomposition; Raman spectroscopy
L

2
1. Introduction
The nonlinear optical (NLO) characteristics of materials can be applied in various areas
of science and technology. However, to define suitable materials for these applications,
one has to carefully analyze the physical properties of the material, such as thermal
decomposition. With regard to amino acid crystals, correlation was found between
thermal decomposition, lattices modes, and the intramolecular hydrogen bonds in the
molecular structure [1, 2]. In amino acid crystals, several types of chemical bonds are
possible, including hydrophobic interactions, and their chemical structures are a good
example of a flexible system with equilibrium between molecular, ionic, and
zwitterionic forms [3].
L
-Tyrosine (LT) is a proteinogenic amino acid that crystallizes in an
orthorhombic noncentrosymmetric structure (P212121) [4]. Depending on the
crystallization method, LT can form semiorganic compounds such as -tyrosine
hydrochloride (LTHCl) [5] and -tyrosine hydrobromide (LTHBr) [6], both with a
L
L
monoclinic crystal structure (P21) and exhibiting the special characteristic of NLO
properties [7–11]. The LTHCl and LTHBr structures derive from the LT structure
complexed with hydrochloric acid and hydrobromic acid, respectively. In these crystals
the molecules are connected by N–H•••X (XT = O, Cl, or Br) and O–H•••O hydrogen
bonds.
Hydrogen bonds are intermolecular interactions that occur in all amino acid
crystal structures, being fundamental to the crystal stability of the molecules in the
periodic network. On the basis of the unit cell parameters and symmetries, the salts of
LT are isostructural [6]. The structure of LTHCl was determined by neutron diffraction,
where the protons were determined with precision. In LTHCl, the oxygen atoms of the
phenol ring O–H•••O (2.62 Å) form a hydrogen bond with the carboxyl group of the
cation and not with the anion. Also, a very strong hydrogen bond is formed with the
chloride anion O–H•••Cl (3.05 Å) [5]. In LTHBr, the same occurs with the oxygen atom
of the phenol ring O–H•••O (2.65 Å), and a very strong hydrogen bond is formed with
the bromide anion O–H•••Br (3.23 Å) [6].
According to data shown in Table 1, N–H•••X bonds are stronger in LT than in
LTHCl and LTHBr. In the LT crystal, the molecules are connected by N–H•••O and O–
H•••O hydrogen bonds, while in LTHCl and LTHBr, N–H•••Cl and N–H•••Br hydrogen

3
bonds are present. In LTHCl and LTHBr, the hydrogen bonds are much longer than in
LT, and this can be explained in terms of the ionic radius of Cl− (1.81 Å) and Br− (1.96
Å).
Hydrogen bonds provide most of the directional interactions that support amino
acid structures, being fundamental to define the main physical and chemical properties
of this class of materials. For example, many amino acid crystals can exist in more than
one polymorph, depending on the temperature and pressure. Additionally, there are
several examples of phase transitions undergone by amino acid crystals when
temperature or pressure changes, with consequent modification of the hydrogen-bond
networks [12–14]. On one hand, a study performed with dilatometric techniques in
L-
alanine, -threonine, and taurine crystals concluded that there is correlation between
L
thermal expansion (a physical process) and the strength of local hydrogen bonding in
these structures at room temperature [15]. On the other hand, thermal decomposition (a
chemical phenomenon) is not always directly correlated with the strength of hydrogen
bonds [15] because anharmonic effects (phonon dynamics) seem to also be important in
this process. In fact, weakening of the intermolecular interactions occurs during heating
of the materials. This explains why although
L-alanine has strong hydrogen bonds
compared with -threonine and taurine it has a low decomposition temperature [2].
L
However, in other situations, thermal decomposition can be related to the geometry of
the hydrogen bonds: the shorter the hydrogen bonds, the higher the decomposition
temperature, making the material thermally stabler, which was observed in the present
study with LT, LTHCl, and LTHBr.
A study on the temperature dependence of the lattice mode of β-alanine is also
worth noting [1]. The behavior of the lattice modes as observed by Raman spectroscopy
is consistent with intermolecular interactions favoring breaking of the hydrogen bonds
in the decomposition process. Additionally, the calculated bulk expansion coefficient,
obtained by X-ray powder diffraction and thermal analysis, is consistent with
weakening of the intermolecular interactions [1]. The intermolecular N–H•••O angle of
β-alanine was correlated with premature thermal decomposition compared with
L-
alanine, mainly because the N–H•••O angle in the former crystal is more acute, favoring
breaking of the bonds.
Therefore, obtaining precise and accurate information on the effect of high
temperature on hydrogen bonds is very important to understand the physical and
chemical properties of these NLO materials. However, this is a hard experimental task.

4
Hydrogen atoms have only one electron, making them very difficult to detect accurately
with X-rays because X-rays are scattered by the electron density. Therefore, a complete
picture of the high-temperature effect in hydrogen bonds cannot be trivially obtained
through only crystallographic experiments. The main strength of Raman spectroscopy is
the ability to provide very rapidly easily analyzable qualitative information and a
powerful diagnosis of this process. In other words, Raman spectroscopy can provide
interesting insights into the effect of high temperature on hydrogen bonds, increasing
our understanding of the effects of temperature on NLO materials.
In this article we report a temperature study of low-wavenumber Raman
scattering from three compounds, LT, LTHCl, and LTHBr, with particular emphasis on
the connection between the hydrogen bonds (representing intermolecular interaction),
the phonon dynamics (physical phenomenon), and thermal decomposition (chemical
phenomenon).
2. Experimental
For the growth of the crystals, a very rigorous solution preparation method (agitation
control, temperature control, and double filtration of the solution) was used to avoid
impurities that could negatively affect the crystalline quality of the materials. Crystals
of LTHCl and LTHBr were prepared by slow spontaneous evaporation of a solution of
LT (97%; Sigma-Aldrich) in hydrochloric acid (37%; Sigma-Aldrich) and hydrobromic
acid (48%; Sigma-Aldrich) in a molar ratio of 1:1 at 313 K, the solution being stirred
for 3 h to achieve total solubilization. To confirm the structure, X-ray diffraction
patterns of crushed powder samples were recorded with a Philips Analytical X-ray
diffractometer (model PW1710) with Cu Kα radiation. The samples were measured in
steps of 0.02° for 2 s for each step, and in an angular 2θ range from 10° to 50°. Rietveld
refinement was performed with the program GSAS [16] and structures provided in [4–
6]. Thermogravimetric and differential thermal analysis measurements were performed
with a DTG-60 instrument (Shimadzu) at a heating rate of 5 °C min-1 in a N2
atmosphere.
Raman spectra were obtained for powdered samples of LT, LTHCl, and LTHBr.
The scattered light was analyzed with a TriVista spectrometer system (Princeton
Instruments) with three stages equipped with a PIXIS 256E CCD camera. The slits were

5
set for 2 cm-1 spectral resolution. The excitation for the Raman experiments consisted of
a He-Ne laser emitting at 632.8 nm with an output power of 75 mW. The high
temperatures for experiments were obtained with a resistive furnace system; the
temperature was monitored by a digital temperature control unit with accuracy of 1.0 K.
The furnace consisted of a cylindrical closed glass capsule with a diameter of 5 mm into
which the samples were placed in powder form. The capsule was surrounded by
resistive furnace connected to a 0–30 V, 0–10 A power supply (Instrutherm FA-1030).
Currents of about 3 A were sufficient to heat the samples to 453 K.
3. Results and discussion
Fig. 1 shows X-ray diffraction patterns for LT, LTHCl, and LTHBr crystals with
Rietveld refinement data and Miller indices. The LT crystal structure at room
temperature is orthorhombic and belongs to the space group P212121, containing four
molecules per unit cell. The unit cell parameters obtained from the refinement are
a = 6.9235(9) Å, b = 21.146(3) Å, and c = 5.8395(3) Å. The LTHCl and LTHBr crystals
crystallize in a monoclinic structure (space group P21), containing two molecules per
unit cell. The LTHCl lattice parameters are a = 11.063(4) Å, b = 9.075(3) Å,
c = 5.010(3) Å, and β = 91.941(3)°, and the LTHBr cell parameters are a = 11.322(4) Å,
b = 9.095(3) Å, c = 5.147(3) Å, and β = 91.211(3)°. The unit cell parameters and space
groups are in good agreement with data previously reported (Rp = 13%, Rwp = 10%, and
S = 3) for the crystals.
Thermogravimetric and differential thermal analysis curves recorded for LT,
LTHCl, and LTHBr crystal powders are shown in Figs. 2 and 3. Thermogravimetric
analysis shows that LT is stabler than both LTHCl and LTHBr; this can be seen through
the endothermic peak in the differential thermal analysis curves, characteristic of the
decomposition process. Some endothermic peaks appear for all three materials, being
recorded as follows: at 556 K for LT (melting point), at 505 K and 509 K for LTHCl
(melting point), and at 513 K for LTHBr (melting point). In LTHCl, the first
endothermic peak corresponds to decomposition of chlorine, and the second
endothermic peak, at 509 K, is related to decomposition of tyrosine. The same does not
occur for LTHBr, with there being only one peak, at 513 K, since bromine decomposes

6
together with tyrosine. Behavior similar to that reported for the LT compounds occurred
in other studies, such as those with LTHCl [9] and LTHBr [8].
The different solid-phase decomposition temperatures can be interpreted in
terms of differences in the strength of the hydrogen bonding at room temperature (Table
1). LT is the stablest crystal, with the highest decomposition temperature, also having
the shortest hydrogen bonds at room temperature. This result is not general (i.e., the
hydrogen bond is not the exclusive cause of the stability of the crystal structure); we
recall that
L-alanine even with strong hydrogen bonds has a low decomposition
temperature because of anharmonic effects [2].
To investigate the connection between vibrational properties and thermal
decomposition in more detail, Raman spectra of LT, LTHCl, and LTHBr were acquired
in the low-wavenumber spectral region, since the low-energy region of the spectrum,
which in most cases is associated with the lattice modes, is very sensitive to changes in
intermolecular interactions. For amino acid crystals, the external modes can be
interpreted as phonons corresponding to either translations or librations [17].
Fig. 4 presents the Raman spectra of LT, LTHCl, and LTHBr in the
wavenumber region below 140 cm-1 at two selected temperatures: 298 K and 423 K.
Some particular bands, with similar wavenumbers, are highlighted by circles in Fig. 4,
and are associated with similar vibrations in all structures. Detailed curve fitting to these
Raman bands using Lorentzian profiles is shown in Fig. 5.
The temperature dependence of the modes with wavenumbers lower than
140 cm-1 is presented in Fig. 6. Bands highlighted by the circles in Fig. 4 are
represented by circles in Fig. 6; the other bands are represented by squares. We fitted all
wavenumber bands with linear functions. The linear equation ν = ν0 +
the temperature dependence in Fig. 6, where ν0 is the extrapolated peak position at 0 K,
and = dν/dT is the first-order temperature coefficient. The best linear fitting is plotted
in Fig. 6 as solid lines. Table 2 presents the dν/dT values for the bands in Fig. 4.
Significant variations of the values were observed for the bands corresponding to
similar vibrations and denoted by a circle. One can observe from Table 2 that the
αT was used to fit
α
α
α
values are higher for LTHCl and LTHBr. For bands denoted by a square, between
20 cm-1 and 80 cm-1, in general, little variation of α values was observed.

7
We now discuss a simple physical model correlating the vibrational modes
observed in the Raman spectra and the hydrogen-bond behavior. The wavenumber
region between 140 cm-1 and 80 cm-1 can be described as modes associated with the
intermolecular N–H•••X bonds, where X = O, Cl, or Br. The temperature dependence of
the band wavenumber denoted by a circle suggests high participation of the N–H•••X
bonds. The α values for X = Cl and X = Br (longer hydrogen-bond distances, Table 1)
vary more strongly than those for X = O (shorter hydrogen-bond distances, Table 1).
Therefore, the “circle” values for these bands are correlated with the lengths of the N–
H•••X bonds in the crystal structures (Table 2). At this point we note that the band at
23 cm-1 has an α value similar to the values for the bands recorded between 140 cm-1
and 80 cm-1, suggesting it also has a contribution from N–H•••X hydrogen bonds.
On the other hand, O–H•••O bonds are the main contributors for the bands in the
region between and 80 cm-1 and 20 cm-1; however, we observed that temperature
changes have a small effect on the wavenumber of these bands. Figure 7 shows the
Raman spectra in the external mode region of LT, LTHCl, and LTHBr in the
temperature range between 298 K and 453 K. This suggests that complexation (i.e., the
introduction of Br and Cl in the LTHCl and LTHBr structures) does not substantially
modify the O–H•••O bonds when compared with the LT crystal. Additionally, it is
worth mentioning that the wavenumber of a mode belonging to LT at approximately
25 cm-1 exhibits a temperature evolution with a steplike form. Such behavior was
previously observed for two bands of DL-alanine associated with torsion of CH3 and
rocking of COO− [18]. The study on DL-alanine indicated that the steplike behavior
should be interpreted as a change of molecular conformation due to changes related to
hydrogen bonds along one specific direction. The investigation performed on the LT
crystal suggests the discontinuous evolution of the wavenumber of some modes
(steplike behavior) originating from hydrogen-bond motion is not only characteristic of
the DL-alanine crystal but can also be a property of many amino acid structures.
However, further studies will be necessary to unravel and to generalize such a finding.
Summarizing the previous paragraphs, the data acquired in this study are
consistent with the hypothesis that there is a correlation between N–H•••X bonds at
room temperature and specific Raman bands recorded between 140 cm-1 and 80 cm-1.
The modes for the LT crystals were previously studied and, in particular, Raman bands
located between 140 cm-1 and 80 cm-1 were associated with torsion of the LT molecule

8
[19–23]. The occurrence of torsional vibrations of the amino acid with low wavenumber
confirms the interpretation that such a region can exhibit both external and internal
modes [24]. This result is consistent with the fact that hydrogen-bonding interactions in
molecular crystals can give rise to several types of phonon dynamics, such as relatively
long-lived optical phonons [25, 26], vibrational solitons [27, 28], and anomalous
thermal conductivities [29].
A previous study affirmed that torsional modes in LTHCl play an important role
in the polymorphism at high pressure. In very recent work, assignment of the modes on
the basis of density functional theory calculations was done for LTHCl, increasing our
understanding of the changes observed in particular Raman-active modes [30].
Torsional bands of the LT crystal exhibiting inversion of the relative intensity and
change of slope dν/dP between 1.0 GPa and 1.5 GPa were understood as corresponding
to conformational changes of the molecules in the unit cell. The present work showed
that the same modes carry fundamental information about the behavior of hydrogen
bonds and the decomposition process occurring in LT and its salts.
Finally, we discuss two additional points. The first one concerns the so-called
hydrophobic interaction. Features of aromatic amino acids serve as a probe to
understand the environment of peptide chains, which plays important roles in
biochemical processes related to some degenerative diseases [31]. Hernández et al. [31]
showed the existence of a doublet, at 850/830 cm-1, that is characteristic of the
hydrophobic/hydrophilic balance of interactions involving the phenol ring. According to
that study, different hydrophobic characters of tyrosine can be inferred from the ratio of
the intensity of the doublet. Although the study of hydrophobic interaction was not the
main objective of our study, we were able to perceive that the relationship between the
two modes remains approximately constant as a function of temperature for the three
powdered samples. This means that the hydrophobic character of interactions apparently
does not change during heating and there is no evidence of breakdown of hydrophobic
interactions in the Raman spectra in our experiments. However, from the ratio of the
intensity of the doublet at 298 K, LTHCl and LTHBr exhibit strong inversion compared
with LT. Thus, the hydrophobic/hydrophilic interaction probably changes with the
insertion of chlorine and bromine in the crystal lattice. A molecular structure
comparison between LT and LTHCl, performed by neutron diffraction, evidenced an

9
additional hydrogen bond (from LTHCl) associated with the phenol ring through the C–
H bond [5].
The second point concerns the possibility to understand the donor/acceptor
character of hydrogens bonds through the Raman spectroscopic data. When a hydrogen
bond is formed, the O–H stretching vibration is redshifted (i.e., the frequency of the
mode is observed at a lower value) [32–34]. Additionally, these previous studies
showed that the redshifts induced in the donor molecules are larger than those in the
acceptors because of the decreased bond strength of the donor O–H bonds. In the
present study on the three LT compounds, it was not possible to obtain Raman spectra
in the spectral region where O–H stretching occurs. Also, we were not able to correlate
the donor/acceptor character of the hydrogen bond with the low-wavenumber bands,
which should be attempted because of this interesting aspect of the bond. As a
consequence, although a discussion of the thermal decomposition temperature of LT
compounds and its connection with the length of N–H•••X bonds at room temperature
was possible, no information regarding donor/acceptor character was clearly obtained.
4. Conclusions
The present study furnished some information to discover a connection between the
decomposition process and the hydrogen bonds in the crystal structure of LT and its
salts. The decomposition process in LT, LTHCl, and LTHBr seems to be dominated by
the N–H•••X (X = O, Cl, or Br) bonds, while the O–H•••O bonds seem to have small
participation in this process. The thermal decomposition temperatures of LT, LTHCl,
and LTHBr are directly connected to the length of the N–H•••X bonds at room
temperature. The behavior of the vibrational modes associated with torsion of the LT
molecule is consistent with a weakening of these connections favoring breaking of the
hydrogen bonds in the decomposition process.
Because the vibrational modes associated with librational motion are important
in the analysis of the decomposition processes, a detailed study of the lattice dynamics
of materials of this kind—doped and pure amino acids—can be very useful for the
development of a model of the low-frequency dynamics and the thermal decomposition
of certain NLO materials.

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Acknowledgments
The authors acknowledge financial support from CNPq, CAPES, and FAPEMA.

11
References
[1] J.C.F. Sousa, R.J.C. Lima, P.F. Façanha Filho, A.O. Dos Santos, P.T.C. Freire, Vib.
Spectrosc. 89 (2017) 69–74.
[2] A.L.O. Cavaignac, R.J.C. Lima, P.F. Façanha-Filho, A.J.D. Moreno, P.T.C. Freire,
Physica B 484 (2016) 22–26.
[3] G. Dovbeshko, L. Berezhinsky, J. Mol. Struct. 450 (1998) 121–128.
[4] A. Mostad, H.M. Nissen, C. Romming, Acta Chem. Scand. 26 (1972) 3819.
[5] M.N. Frey, T.F. Koetzle, M.S. Lehmann, W.C. Hamilton, J. Chem. Phys. 58 (1973)
2547–2556.
[6] R. Srinivasan, Curr. Sci. 27 (1958) 46–48.
[7] P. Anandan, T. Saravanan, S. Vasudevan, R.M. Kumar, R. Jayavel, J. Cryst. Growth
312 (2010) 837–841.
[8] B.N. Moolya, S.M. Dharmaprakash, J. Cryst. Growth 290 (2006) 498–503.
[9] P. Anandan, S. Vetrivel, S. Karthikeyan, R. Jayavel, G. Ravi, Optoelectron. Adv.
Mater. 6 (2012) 1128–1133.
[10] P. Anandan, S. Vetrivel, R. Jayavel, C. Vedhi, G. Ravi, G. Bhagavannarayana, J.
Phys. Chem. Solids 73 (2012) 1296–1301.
[11] S. Natarajan, G. Shanmugam, S.A.M.B. Dhas, Cryst. Res. Technol. 43 (2008) 561–
564.
[12] J.O. Carvalho, G.M. Moura, A.O. dos Santos, R.J.C. Lima, P.T.C. Freire, P.F.
Façanha-Filho, Spectrochim. Acta Part A Mol. Biomol. Spectrosc. 161 (2016) 109–114.
[13] G.M. Moura, J.O. Carvalho, M.C.D. Silva, P.F. Façanha-Filho, A.O. dos Santos.
Mater. Chem. Phys. 165 (2015) 150–155.
[14] R.A. Soares, R.J.C. Lima, P.F. Façanha Filho, P.T.C. Freire, J.A. Lima Jr., J.G. da
Silva Filho, Physica B 521 (2017) 317–322.

12
[15] R.J.C. Lima, E.C. Santos-Junior, A.J.D. Moreno, P.F. Façanha-Filho, P.T.C. Freire,
M.I. Yoshida, J. Therm. Anal. Calorim. 111 (2013) 627–631.
[16] A.C. Larson, R.B. Von Dreele, GSAS. Report LAUR 86-48, Los Alamos National
Laboratory, New Mexico, 2004.
[17] R.A. Crowell, E.L. Chronister, Phys. Rev. B 48 (1993) 172.
[18] J.A. Lima Jr., P.T.C. Freire, F.E.A. Melo, J.M. Filho, G.P. De Sousa, R.J.C. Lima,
P.F. Façanha Filho, H.N. Bordalo, J. Raman Spectrosc. 41 (2010) 808–813.
[19] S. Natarajan, G. Shanmugam, S.A.M.B. Dhas, Cryst. Res. Technol. 43 (2007) 561–
564.
[20] P. Ilayabarathi, J.Chandrasekaran, P. Maadeswaran, Optik 124 (2013) 1125–1127.
[21] M.N. Frey, T.F. Koetzle, M.S. Lehmann, W.C. Hamilton, J. Chem. Phys. 58 (1973)
2547–2556.
[22] D.W. Smits, E.H. Wiebenga, Acta Crystallogr. 6 (1953) 531–539.
[23] B.N. Moolya, S.M. Dharmaprakash, Moolya, B. Narayana, S.M. Dharmaprakash,
Int. J. Phys. 79 (2005) 1423–1425.
[24] T.J. Kosic, R.E. Cline Jr., D.D. Dlott, J. Chem. Phys. 81 (1984) 4932–4949.
[25] T.J. Kosic, R.E. Cline Jr., D.D. Dlott, Chem. Phys. Lett. 103 (1983) 109.
[26] T.J. Kosic, R.E. Cline Jr., D.D. Dlott, J. Chem. Phys. 81(1984) 4932.
[27] A.C. Scott, I.J. Bigio, C.T. Johnson, Phys. Rev. B 39 (1989) 883.
[28] G. Careri, U. Buintempo, F. Galluzzi, A.C. Scott, E. Gratton, E. Shyamsunder,
Phys. Rev. B 30 (1984) 4689.
[29] R.S. Kwok, P. Maxton, A. Migliori, Solid State Commun. 74 (1990) 1193.
[30] C.A.A.S.S. dos Santos, J.O. Carvalho, J.G. da Silva Filho, J.L. Rodrigues, R.J.C.
Lima, G.S. Pinheiro, P.T.C. Freire, P.F. Façanha Filho, Physica B 531 (2018) 35–44.
[31] B. Hernández, Y-M. Coïc, F. Pflüger, S.G. Kruglik, M. Ghomi, J. Raman
Spectrosc. 47 (2016) 210–220.

13
[32] T. Scharge, C. Emmeluth, T. Haber, M. A. Suhm, J. Mol. Struct. 786 (2006) 86–
95.
[33] T. Scharge, C. Cezard, P. Zielke, A. Schutz, C. Emmeluth, M.A. Suhm, Phys.
Chem. Chem. Phys. 9 (2007) 4472–4490.
[34] M. Heger, T. Schargez, M.A. Suhm, Phys. Chem. Chem. Phys. 15 (2013) 16065–
16073.
Fig. 1. X-ray diffraction patterns with Rietveld refinement data for
L-tyrosine (LT),
L-
tyrosine hydrochloride (LTHCl), and
temperature.
L-tyrosine hydrobromide (LTHBr) at room
Fig. 2. Thermogravimetric curves for
L-tyrosine (LT), L-tyrosine hydrochloride
(LTHCl), and -tyrosine hydrobromide (LTHBr) powder from 293 K to 673 K.
L
Fig. 3. Differential thermal analysis (DTA) for
L-tyrosine (LT),
L-tyrosine
hydrochloride (LTHCl), and
600 K.
L-tyrosine hydrobromide (LTHBr) powder from 350 K to
Fig. 4. Raman spectra of polycrystalline
L-tyrosine (LT), L-tyrosine hydrochloride
(LTHCl), and -tyrosine hydrobromide (LTHBr) at 298 K and 423 K in the region of
L
the lattice modes.
Fig. 5. Raman bands associated with torsion of the
L-tyrosine (LT) molecule
(adjustment with Lorentz curve). LTHBr,
hydrochloride.
L-tyrosine hydrobromide; LTHCl, L-tyrosine
Fig. 6. Temperature dependence of the lattice mode wavenumber (linear fitting) for (a)
-tyrosine, (b) -tyrosine hydrochloride, and (c) -tyrosine hydrobromide.
L
L
L
Fig. 7. Raman spectra of polycrystalline
(LTHCl), and -tyrosine hydrobromide (LTHBr) for all temperatures in the region of
the lattice modes.
L-tyrosine (LT), L-tyrosine hydrochloride
L

Table 1. Distances and angles in the hydrogens bonds in
hydrochloride, and -tyrosine hydrobromide.
L-tyrosine, L-tyrosine
L
A–H···B–C
-Tyrosine
A···B (Å)
H ···B (Å)
< A–H ···B (º)
L
N–H2···O1–C4
N–H4···O3–C9
N–H3···O3–C9
2.88
2.83
2.88
2.67
2.120
1.789
1.853
1.689
129.8
169.8
172.7
173.8
O1–H1···O2–C9
-Tyrosine hydrochloride
L
N–H1···Cl
N–H5···Cl
N–H9···Cl
O3–H2 ···Cl
3.25
2.378
2.471
2.505
2.078
1.609
2.420
144.5
161.8
137.4
165.6
170.7
108.0
3.45
3.33
3.05
2.62
2.90
O2–H6···O3–C8
N–H5···O1–C1
L-Tyrosine hydrobromide
N–H1···Br
N–H5···Br
N–H9···Br
O3–H2···Br
3.46
2.436
2.493
2.531
2.120
1.628
2.464
144.2
161.4
136.9
165.6
170.6
108.1
3.50
3.46
3.23
2.65
2.94
O2–H6···O3–C8
N–H5···O1–C1

Table 2. Variation of the wavenumber as a function of temperature, dν/dT, for L-
tyrosine (LT),
(LTHBr).
L-tyrosine hydrochloride (LTHCl), and L-tyrosine hydrobromide
Mode
LT
LTHCl
LTHBr
dν/dT (cm-1 K-
ν (298
dν/dT (cm-1 K-
ν (298
dν/dT (cm-1 K-1)
ν (298
1
1
K)
)
K)
K)
)
23
27
-0.015
-0.002
-0.012
-0.002
-0.02
23
30
40
-0.03
-0.01
-0.01
23
29
-0.04
-0.02
-0.01
-0.02
-0.02
-0.03
-0.05
-0.04
35
34
55
52
76
61
-0.01
-0.03
-0.06
-0.07
-0.02
58
96
-0.02
105
117
120
125
107
113
125
112
128
-0.03
-0.03

1
Highlights
•
•
•
•
A high-temperature Raman scattering study was performed on
tyrosine hydrochloride, and -tyrosine hydrobromide crystals.
L-tyrosine, L-
L
There is correlation between hydrogen bonds, the phonon dynamics, and thermal
decomposition.
Hydrogen bonding and thermal decomposition are correlated with Raman bands
in the low-wavenumber range.
The behavior of the phonons is important in the analysis of decomposition
processes.