Halogenides of β-alanine

Article abstract of DOI:10.1016/j.molstruc.2020.128825

The following halogenides of β-alanine: β-Ala·HF (I), β-Ala·HCl (II), β-Ala·HBr (III), β-Ala·HI (IV), 2β-Ala·HBr (V) and 2β-Ala·HI (VI) have been synthesized and characterized structurally and by vibrational spectroscopy. The salts (I–III) are simple salts A⁺X^? but are not isostructural. The salt (IV) of the type of (A⁺?A⁺)(X^–)₂ comprises a centrosymmetric dimeric dication. The isotypic salts (V), (VI) belong to the type (A⁺?A)X^– with centrosymmetric dimeric cations and strong hydrogen bonds.

Full text of DOI:10.1016/j.molstruc.2020.128825

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Halogenides of β-alanine
A.M. Petrosyan, G. Giester, V.V. Ghazaryan, M. Fleck
PII:
S0022-2860(20)31150-9
DOI:
https://doi.org/10.1016/j.molstruc.2020.128825
MOLSTR 128825
Reference:
To appear in: Journal of Molecular Structure
Received Date: 25 April 2020
Revised Date: 1 July 2020
Accepted Date: 2 July 2020
Please cite this article as: A.M. Petrosyan, G. Giester, V.V. Ghazaryan, M. Fleck, Halogenides of β-
alanine, Journal of Molecular Structure (2020), doi: https://doi.org/10.1016/j.molstruc.2020.128825.
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A.M. Petrosyan, G. Giester, V.V. Ghazaryan, M. Fleck, “Halogenides of
Credit authorship contribution statement
β-alanine”
A.M. Petrosyan: Conceptualization, Writing - original draft, Review & editing.
G. Giester: Investigation, Formal analysis,Writing - review & editing.
M. Fleck: Formal analysis, Visualization, Writing - review & editing.
V.V. Ghazaryan: Investigation, Visualization, Writing - review & editing.

Halogenides of β-alanine
A.M. Petrosyana1, G. Giester b, V.V. Ghazaryan a, M. Fleck b
a Institute of Applied Problems of Physics, NAS of Armenia, 25 Nersessyan Str., 0014 Yerevan, Armenia
b Institute of Mineralogy and Crystallography, University of Vienna, Althanstr. 14, A-1090 Vienna,
Austria
Abstract
The following halogenides of
β
-alanine:
β-Ala·HF (I), β-Ala·HCl (II), β-Ala·HBr (III), β-Ala·HI
(IV), 2 -Ala·HBr (V) and 2
β
β-Ala·HI (VI) have been synthesized and characterized structurally
and by vibrational spectroscopy. The salts (I-III) are simple salts A+X− but are not isostructural.
The salt (IV) of the type of (A+···A+)(X–)2 comprises a centrosymmetric dimeric dication. The
isotypic salts (V), (VI) belong to the type (A+···A)X– with centrosymmetric dimeric cations and
strong hydrogen bonds.
Keywords: salts of β-alanine; crystal structure; dimeric cations; vibrational spectra
1. Introduction
Reactions of amino acids with inorganic and organic acids may lead to the formation of various
types of salts, when a proton transfer takes place from an acid to an amino acid [1]. In addition to
simple compounds with definite cation and anion as well as mixed salts with different cations
and anions there is a certain class with various types of dimeric cations.
The majority of studied halogenides of amino acids are chlorides. However, investigation of
other halogenides is also of interest and they may differ significantly from chlorides. Fluorine,
chlorine, bromine and iodine atoms vary by their electronegativity (by Pauling scale: 3.98, 3.16,
2.96 and 2.66, respectively [2]). Ionic radii of fluoride, chloride, bromide and iodide anions are
also different: i.e. 1.19, 1.67, 1.82 and 2.06, respectively (in Å by Shannon [3]). As can be seen
by both characteristics, the anions chloride and bromide are closest to each other. Therefore,
chlorides and bromides are usually isostructural. Iodides are often not isostructural with
chlorides and bromides, while fluorides as a rule are not isostructural with other halogenides (see
section 13.2 in Ref. [4]).
1
Corresponding author: E-mail addresses: aram.m.petrosyan@gmail.com, apetros@iapp.sci.am (A.M.
Petrosyan)

For nonstandard and achiral
[5]) as well as with (A+···A+)(X–)2 (e.g. (
AlaH···
-Ala)(NO3)) [7]) types with dimeric cations are known, where A and A+ (or AH) are
amino acids in zwitterionic and protonated cationic states, respectively, and X– is an anion.
There is some information also concerning halogenides of -alanine. Ennan et al. [8] studied
reactions of some amino acids including -alanine with hydrofluoric acid. For comparison they
β
-alanine various simple salts of (A+X–) type (e.g. (
-AlaH··· β-
-AlaH)(NO3)2) [6]) and (A+···A)X– (e.g. (
β-AlaH)(H2PO4)
β
β
β
β
β
obtained also respective hydrochlorides. Based on the presence of a strong and broad absorption
band in the 700–2000 cm-1 region in the infrared spectrum of β-alanine∙HF and the absence of
this band in the spectrum of the respective chloride they concluded that β-alanine∙HF contains
the (F-H-F)– group, and also a β-alaninium cation and zwitterionic β-alanine, which are
connected with the anion by hydrogen bonds according to the following scheme:
+
–OOC-CH2-CH2-NH3 ∙(F-H-F)–∙+H3N-CH2-CH2-COOH. In [1] it was supposed that formation
of a dimeric cation according to the scheme: (
structure determination was necessary to confirm or reject these suppositions. Godzisz et al. [9]
obtained crystals of 2
-Ala·HCl and performed a detailed structural and vibrational and 13C
solid-state NMR spectroscopic investigation. According to [9] the 2 -Ala·HCl salt crystallizes in
the centrosymmetric space group C2/c and consists of a ( -AlaH··· -Ala) dimeric cation formed
β β
-Ala+··· -Ala)(F-H-F)– is also possible. However,
β
β
β
β
by a symmetric O···H···O hydrogen bond with an O···O distance equal to 2.4729(17) Å at
298K. In view of this centrosymmetric hydrogen bond the authors determined the crystal
structure of the 2
observed in this temperature range. In [10], among other 20 salts it was reported on existence of
-Ala·HBr crystals without detailed structural and vibrational spectroscopic data because of
β-Ala·HCl salt at 100 K hoping to find a phase transition, but none was
2β
limited scope of the paper.
In the present study we report new results on structures and vibrational spectra of β-Ala·HF (I),
β
-Ala·HCl (II), β-Ala·HBr (III) β-Ala·HI (IV), 2β-Ala·HBr (V) and 2β-Ala·HI (VI) and we
continue the systematic investigation of the role of amino acids in the issue of isostructurality of
their halogenides [11].
2. Experimental
2.1. Sample preparation
As initial reagents we used β-alanine from “Armbiotechnology” Institute (provided by Dr. A.E.
Aghajanyan), hydrofluoric acid (45%, ultrapure grade), hydrochloric (32%, chemically pure
grade) and hydrobromic (40.5%, ultrapure grade) acids from “Reakhim“ Co., and hydriodic acid
(57% w/w, distilled, stabilized with <1.5% hypophosphorous acid, 99.95%) from “Sigma-
Aldrich” Chem. Co. Crystals of titled compounds were obtained from aqueous solution
containing stoichiometric quantities of β-alanine and the respective acid by slow evaporation at
room temperature. A typical amount of β-alanine taken was 1 g and the volumes of the final

solutions were 6 ml approximately. Small polyethylene beakers were used for preparation of
solutions. Only for β-alanine.HBr (III) silica gel was used as an absorber to crystallize
hygroscopic crystals.
2.2. Crystal structure determination and refinement
Small fragments of the title compounds with homogeneous extinction were were manually
selected, mounted on glass capillaries with laboratory grease and used for single crystal X-ray
data collections: sample (V) was measured at room temperature on an Enraf Nonius Kappa CCD
diffractometer (sealed tube, equipped with a graphite monochromator + monocapillary optics
using Mo-Kα radiation) at a crystal-detector distance of 30 mm, 0.5° scan width.
All other compounds were investigated at 200 K on a Bruker APEXII diffractometer equipped
with a CCD area detector, an Incoatec Microfocus Source IµS (30 W, multilayer mirror, Mo-Kα)
and an Oxford Cryosystems Cryostream 800 Plus LT device. Several sets of phi- and omega-
scans with 2° scan width were collected at a crystal-to-detector distance of 40 mm up to 65° 2ϴ
full sphere. The absorption was corrected in all cases by the evaluation of multi-scans. Reflection
data were processed with the Nonius program package DENZO-SMN [12] for (V) or otherwise
within the Bruker APEX3 software suite [13]. The crystal structures were solved by direct
methods and refined by full-matrix least-squares techniques (Shelx-97 [14].
Non-hydrogen atoms were refined with independent anisotropic displacement parameters,
hydrogen atoms with isotropic displacement parameters. All hydrogen atoms were treated as
riding on their parent atoms, i.e. fixing distances and angles but allowing free rotation.
Selected crystal parameters as well as a summary on the data collections and structure
refinements are given in Tables 1 and 7, selected bond lengths and valence and torsion angles in
Tables 2 and 8. Details of the hydrogen bonding systems are compiled in Tables 3-6 and 9-10.
Further crystallographic data have been deposited with the Cambridge Crystallographic Data
Centre and can be obtained free of charge via www.ccdc.cam.ac.uk/conts/retrieving.html (or
from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK;
fax: +44 1223 336033), citing the title of this paper and the CCDC nos. 1967057 (I), 1967058
(II), 1967470 (III), 1967060 (IV), 776234 (V) and 1967059 (VI).
2.3. Vibrational spectra
Attenuated total reflection Fourier-transform infrared spectra (FTIR ATR) were registered by a
Nicolet 5700 spectrometer (ZnSe prism, Happ-Genzel apodization, ATR distortion is corrected,
number of scans 32, resolution 4 cm-1). Part of the IR spectrum in the region 500–400 cm-1 was
taken from FTIR spectra registered with Nujol mull (number of scans 32, resolution 2 cm-1).

Fourier-transform Raman spectra were registered by a NXR FT-Raman Module of a Nicolet
5700 spectrometer. Number of scans and laser power at the sample were 512 and 0.43 W (I), 512
and 0.18 W (IV), 256 and 0.44 W (V) and 1024 and 0.18 W. (VI).
3. Results and discussion
3.1. β-Alaninium fluoride (I)
The salt (I) crystallizes in the monoclinic system with space group P21/c. The asymmetric unit
contains one formula unit, that is, one -alaninium cation and one fluoride anion (Fig. 1).
β
Fig. 1. Molecular structure of
β
-alaninium fluoride (I).
–
+
So, neither the scheme OOC-CH2-CH2-NH3 ∙(F-H-F)–∙+H3N-CH2-CH2-COOH [8] nor the
scheme (
-Ala+··· -Ala)(F-H-F)– [1] was confirmed. The salt can be described as of A+X–
simple type, that is ( -AlaH)F. Selected bond lengths and angles are presented in Table 2. These
values are usual for the -alaninium cation and agree with respective values of -Ala·HCl (II),
-Ala·HBr (III) and -Ala·HI (IV) (Table 2). The torsion angles O1C1C2C3 and C1C2C3N1
define the arrangements of carboxyl and amino groups (Table 2). The conformation of the
β
β
β
β
β
β
β
β
-
alaninium cation in the structure of (I) is gauche(+). Hydrogen bond parameters in the structure
of (I) are shown in Table 3. The carboxyl group and the fluoride ion form an O1-H1···F1
+
hydrogen bond with an O···F distance equal to 2.4027(9) Å. The NH3 group forms three N-
H···F hydrogen bonds: N1-H11···F1, N1-H12···F1 and N1-H13···F1 (Table 3). There are also
short contacts: C3-H32···F1 (with distances H32···F1 and C3···F1 equal to 2.41 and 3.402(1) Å,
respectively), N1-H12···O2 and N1-H11···O2 (the last one is intramolecular), which may be
considered as weak hydrogen bonds.
The O1-H1···F1 hydrogen bond is not record-breaking short but still rather short for O-H···F
type hydrogen bonds. For comparison, in the structure of glycine hydrogen fluoride [15] there
are four glycinium cations three of which form O-H···F hydrogen bonds with O···F distances

equal to 2.436(1) Å, 2.446(1) Å and 2.476(1) Å, while in the structure of L-leucinium fluoride
monohydrate [16] this O···F distance measures 2.441(1) Å.
Fig. 2. Infrared and Raman spectra of β-alaninium fluoride (I).
Infrared and Raman spectra of (I) are shown in Fig. 2. Knowledge of the crystal structure makes
it possible to interpret the vibrational spectra. The presence of a broad absorption band
superimposed with peaks in the 2000-900 cm-1 interval is due to the stretching mode of the O-H
group of the
β-alaninium cation in an O-H···F strong hydrogen bond. Such a band is absent in
the spectra of (II), (III) and (IV) (see below). So, peaks in high-frequency region are caused by

+
+
stretching modes of NH3 and CH2 groups. The H11 atom of the NH3 group forms weaker
hydrogen bonds. Therefore, the absorption peak at 3191 cm-1 we assigned to stretching vibration
+
of the N1-H11 bond. The H12 atom of the NH3 group forms stronger hydrogen bonds and the
absorption band at 2811 cm-1 is assigned to stretching vibration of the N1-H12 bond. The H13
atom of the NH3 group forms the strongest hydrogen bond N1-H13···F1 and the absorption
+
band at 2712 cm-1 is assigned to stretching vibration of the N1-H13 bond. Their positions are in
good agreement with a ν(NH) vs. d(N···F) correlation [17]. Weak peaks at 3015, 2993, 2962 and
2941 cm-1 are assigned to ν(CH) which is confirmed by respective peaks in the Raman spectrum.
Here 3018, 2992 cm-1 and 2965, 2943 cm-1 are assigned to νas(CH) and νs(CH), respectively.
Peaks at 2560 and 2458 cm-1 we assign to overtone and combination tones. In the range 2000-
400 cm-1 there are some characteristic peaks of the
β-alaninium cation. They are assigned based
on [18]. The presence of an absorption band at 1748 cm-1 testifies the presence of a COOH group
(ν(C=O)). The peaks at 1645, 1602 cm-1 are assigned to asymmetric, an absorption band at 1511
+
cm-1 to symmetric deformation vibrations of the NH3 group; peaks at 1474, 1407, 1354 and
1306 cm-1 to deformation vibrations of CH2 groups, the band at 1250 cm-1 to ν(C-OH), the band
at 1053 cm-1 to ν(C-N) and peaks at 869, 822 cm-1 to ν(C-C).
3.2. β-Alaninium chloride (II)
The salt (II) crystallizes in the orthorhombic system with space group Pbca (Table 1) and
therefore is not isostructural with (I). Although -alaninium fluoride (I) and -alaninium chloride
(II) are not isostructural and have different symmetries, they have some common features. The
asymmetric unit of (II) also contains one formula unit, that is, one -alaninium cation and one
chloride anion (Fig. 3). It too can be described as of A+X– simple type, that is (
-AlaH)Cl.
β
β
β
β
Fig. 3. Asymmetric unit of β-alaninium chloride (II).
The intramolecular bond lengths and angles of (II) and also the conformation (Table 2) are
similar to that of (I). The conformation of the -alaninium cation in the structure of (II) also is
gauche(+). Hydrogen bond parameters in the structure of (II) are listed in Table 4. The carboxyl
β

group forms an O1-H1···Cl1 hydrogen bond with an O···Cl distance equal to 3.007(2) Å. The
+
NH3 group forms three N-H···Cl hydrogen bonds: N1-H11···Cl1, N1-H12···Cl1 and N1-
H13···Cl1 (Table 4). Due to similar conformation of the β-alaninium cation here also an
intramolecular contact N1-H13···O2 is present. There are three short C-H···Cl contacts: C2-
H21···Cl1 (with H21···Cl1 and C2···Cl1 2.84 and 3.768(2) Å, respectively), C3-H31···Cl1(with
H31···Cl1 and C3···Cl1 2.93 and 3.449(2) Å, respectively) and C3-H32···Cl1 (with H32···Cl1
and C3···Cl1 2.71 and 3.699(2) Å, respectively), which can be considered as weak hydrogen
bonds. In the structures of chlorides of amino acids, the O···Cl distances in O-H···Cl hydrogen
bonds are ca. 3.0 Å. Shorter hydrogen bonds were observed in the structures of two forms of
betainium chloride: 2.955(2) Å [19] and 2.946(3) Å [20]. Therefore, in the structure of (II) the
O1-H1···Cl1 hydrogen bond should be considered as common in contrast to (I), where the
respective O1-H1···F1 hydrogen bond is significantly shorter than usual O-H···F hydrogen
bonds.
The infrared and Raman spectra of (II) are shown in Fig. 4. In this case, broad absorption bands
in the region 2000-400 cm-1 are absent. So, in the high-frequency region in addition to stretching
vibrations of N-H and C-H bonds also a vibration of the O-H group is expected. In the spectrum
of (II)
2920 cm-1 according to correlation [17]. The absorption peak at 3165 cm-1 and Raman-line at
3170 cm-1 we assign to a weaker hydrogen bonded N-H group. The
(CH) vibrations of CH2
groups are better seen in the Raman spectrum at 3018, 2989, 2950, 2930 cm-1. Other expected
peaks of
-alaninium cation are observed in the region 1800-500 cm-1.
ν(OH) for O-H···Cl hydrogen bond with O···Cl distance equal to 3.0 Å is expected at ca.
ν
β

Fig. 4. Infrared and Raman spectra of β-alaninium chloride (II).
3.3.β-Alaninium bromide (III)
Crystals of β-alaninium bromide (III) are more hygroscopic compared to those of β-alaninium
chloride (II). The salt (III) crystallizes in the monoclinic system with space group P21/c (Table
1) and therefore it is not isostructural with (II). The space group is the same for (III) and (I),
however, already comparison of unit cell parameters shows that both are not isostructural. The
asymmetric unit of (III) also contains one formula unit, that is, one
β
-alaninium cation and one
-AlaH)Br.
bromide anion (Fig. 5). It can be described as the A+X– simple type, too, that is, (
β

Fig. 5. Asymmetric unit of β-alaninium bromide (III).
The intramolecular bond lengths and angles of (III) and the conformation (Table 2) are like
those of (I) and (II). The conformation of the
gauche(+).
β-alaninium cation in the structure of (III) also is
Hydrogen bond parameters in the structure of (III) are shown in Table 5. The carboxyl group
forms an O1-H1···Br1 hydrogen bond with the bromide ion with an O···Br distance equal to
+
3.2119(14) Å. The NH3 group forms two N-H···Br hydrogen bonds: N1-H11···Br1 (-x+2, -y+1,
-z+1) and N1-H12···Br1 (-x+1, -y+1, -z+1) and one N1-H13···O2 (-x+2, -y+1, -z+1) hydrogen
bond (Table 5). The atom H11 has an additional contact N1-H11···Br1 (-x+1, -y+1, -z+1) on the
level of strong van der Waals interaction. Due to similar conformation of the β-alaninium cation
here also an intramolecular contact N1-H13···O2 is present. In the structure there is a short C3-
H32···Brl contact (with H32···Br1 and C3···Br1 2.98 and 3.660(2) Å respectively), which can
be considered as a weak hydrogen bond.

Fig. 6. Infrared spectrum of
β-alaninium bromide (III).
Infrared spectrum of (III) is shown in Fig. 6. Raman spectrum of (III) was not registered because
of its hygroscopic nature, even registration of its IR spectrum was difficult.
The peak at 3412 cm-1 in the spectrum of (III) is caused by absorption of hygroscopic water. The
strong absorption band with peaks at 3215, 3148, 3023, 2954, 2928 cm-1 is caused by
ν
(NH),
+
ν
(OH) and
ν
(CH) vibrations of NH3 , COOH and CH2 groups. A slight shift of the absorption
band is due to the lower electronegativity of bromine compared with chlorine. Characteristic and
expected peaks of the
-alaninium cation are observed in the region 1800-500 cm-1.
β
The crystals (I, II, III) not being isostructural, nevertheless, form the same A+X− simple type and
the remarkable difference between their infrared spectra is caused by strong O-H···F and usual
O-H···Cl, O-H···Br hydrogen bonds.
3.4.
β-Alaninium iodide (IV)
The salt (IV) crystallizes in the monoclinic system with space group P21/n (Table 1). The
asymmetric unit of (IV) also contains one formula unit, that is, one β-alaninium cation and one
iodide anion.

Selected intramolecular bond lengths as well as valence and torsion angles of (IV) are provided
in Table 2. However, the structure of (IV) differs from the structures of (I, II, III). Hydrogen
bond parameters in the structure of (IV) are shown in Table 6. In this case the carboxyl group of
the
cations combine to a centrosymmetric
the O···O distance of O1-H1···O2 hydrogen bond is equal to 2.6540(16) Å.
β
-alaninium cation does not form hydrogen bond with an anion. Instead, two
β-alaninium
β
-alaninium··· -alaninium dimeric cation (Fig. 7), where
β
Fig. 7. Dimeric
β
-alaninium…β-alaninium cation in the structure of β-alaninium iodide (IV).
The conformation of the
β
-alaninium cation in this case is gauche(-). There is an intermolecular
N1-H13···O2 contact, too, which can be considered as weak hydrogen bond. The iodide anion
forms two N-H···I type hydrogen bonds: N1-H12···I1 (x, y, z) and weak N1-H11···I1 (-x+1/2,
y-1/2, -z+1/2). So, the salt
differs significantly from the crystals (I, II, III). Most of known salts with (A+···A+) type cation
are salts of -alanine [1]. In [21] four types of
-Ala+··· -Ala+ dimeric cations (A, B, C, D) were
distinguished. Two of them are centrosymmetric and other two are noncentrosymmetric. The
first A-type is characterized by a centrosymmetric arrangement of two -alaninium cations in
gauche conformation. The B-type looks like the A-type, but there is no inversion center. This
type is represented by ( -AlaH··· -AlaH)(NO3)2) [6]. The C-type is characterized by
centrosymmetric trans-oriented -alaninium cations, and in the D-type two amino ends of both
gauche-oriented -alaninium cations are facing in the same direction and therefore this type also
β
-Ala·HI (IV) is one more salt of the (A+···A+)(X–)2 type and thus
β
β
β
β
β
β
β
β
is noncentrosymmetric. Consequently, the dimeric cation in the crystal (IV) belongs to the A-
type.

Fig. 8. Infrared and Raman spectra of
β-alaninium iodide (IV).
Vibrational spectra of (IV) are shown in Fig. 8. For
ν
(OH) the position at ca. 3000 cm-1 is
expected for the O-H···O hydrogen bond with an O···O distance of 2.654 Å according to the
correlation between
ν
(OH) and O···O distance [22]. So, the absorption band centered at 2990
+
cm-1 is caused by
ν
(NH),
ν
(OH) and
ν
(CH) vibrations of NH3 , COOH and CH2 groups. The
absorption peak at 3150 cm-1 and a Raman-line at 3148 cm-1 are caused by
ν
(NH) of the NH3
+
group in the weaker hydrogen bond N1-H13···O2. The
ν
(CH) vibrations of CH2 groups are
better seen in the Raman spectrum at 3034, 2991, 2947, 2923 cm-1. Other expected peaks of
alaninium cation are observed in the region 1800-500 cm-1.
β-

3.5. β-Alaninium β-alanine bromide (V) and β-alaninium β-alanine iodide (VI)
β
-Alaninium
β-alanine bromide (V) and β-Alaninium β-alanine iodide (VI) are isotypic with β-
alaninium -alanine chloride [9], they crystallize in space group C2/c with four formula units in
β
the unit cell (Table 7). The asymmetric unit contains half of a formula unit, both the center of the
dimeric cation and the halogenide anion are on special positions (an inversion center or a twofold
axis, respectively). In Fig. 9 the centrosymmetric dimeric cation and the bromide anion are
shown.
Fig. 9. Molecular structure of β-Alaninium β-alanine bromide (V). Both bromide anion and the
center of the dimeric cation are on special positions.
In Table 8 selected bond lengths and angles in the structures of (V) and (VI) are listed.
Evidently, these values are quite similar for both crystals. The conformation of β-alaninium
cations in the structures of (V) and (VI) also is gauche(+). Hydrogen bonds parameters in the
structures of (V) and (VI) are shown in Tables 9 and 10. Additionally there are short contacts
C3-H32···Br1 in (V) and C3-H31···I1, C3-H32···I1 in (VI) with distances H32···Br1 (2.94 Å),
C3···Br1 (3.903 Å), H31···I1 (3.14 Å), C3···I1 (4.101 Å), H32···I1 (3.15 Å), C3···I1 (3.881 Å),
which can be considered as weak hydrogen bonds. In the model proposed for β-alaninium β-
alanine chloride [9] the proton lies on the inversion center, while in our model for (V) and (VI)
H1 was favored on a general, half-occupied position, symmetrically related by the center of
inversion. Neutron diffraction analysis of the proton position would be necessary to determine
which of these models is more reliable. The O···O distances in centrosymmetric dimeric cations
of (V) and (VI) are equal to 2.4723(17) and 2.461(2) Å, respectively, which are well comparable
with 2.4729(17) Å in β-alaninium β-alanine chloride [9].

Fig. 10. Infrared and Raman spectra of
β-alaninium β-alanine bromide (V).
Vibrational spectra of (V) and (VI) are shown in Figs. 10 and 11, respectively. They are very
similar and with that of
β
-alaninium
β
-alanine chloride [9]. In the high-frequency region only
+
stretching vibrations (NH) and
ν
ν
(CH) of NH3 and CH2 groups are expected. Stretching
vibrations
caused by
ν
ν
(CH) are better seen in the Raman spectra, which are superimposed with bands
(NH). According to the correlation between the stretching vibration of O-H bonds
ν
(OH) (in cm-1) and the R(O···O) distance (in Å) [22] strong O-H···O hydrogen bonds in the
region 2.44–2.58 Å are characterized by a linear dependence, which is possible to reflect as
(OH)=11250R-26876 [23]. For crystals (V) and (VI) with O···O distances equal to 2.4723(17)
Å (at 296 K) and 2.461(2) Å (at 200 K) the expected value for (OH) of (V) is 940
20 cm-1 and
810
20 cm-1 for (VI). These values are in good agreement with absorption bands observed in
Figs 16, 17 in the region 1500-400 cm-1 centered at ca. 850 cm-1.
ν
ν
±
±

Fig. 11. Infrared and Raman spectra of β-alaninium β-alanine iodide (VI).
Conclusions
The salts
alaninium iodide (IV) are not isostructural. The salts (I-III) are formed by simple type A+X− ,
where the carboxyl group forms a hydrogen bond with the respective anion. The salt (IV) is one
β-alaninium fluoride (I), β-alaninium chloride (II), β-alaninium bromide (III) and β-
more salt with a centrosymmetric
β
-alaninium···
β
-alaninium dimeric dication:
O
H
O
H3N
CH2 CH2
C
C
CH2 CH2
NH3
2I
O
H
O

with an O···O hydrogen bond distance equal to 2.6540(16) Å.
The isotypic salts -alaninium -alanine bromide (V) and -alaninium β-alanine iodide (VI)
β
β
β
comprise centrosymmetric dimeric cations with strong hydrogen bonds with O···O distances
equal to 2.4723(17) Å and 2.461(2) Å, respectively. The presence of strong hydrogen bonds in
the structures of (I), (V) and (VI) is reflected in the infrared spectra.
Acknowledgment
This work was supported by the RA MES Committee of Science, in the frames of the research
project № 18T-1D033.
References
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β
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(2012).

Table 1. Crystal data and details of the refinement for
β
-alaninium fluoride (I),
β
-alaninium
chloride (II),
β
-alaninium bromide (III) and
(I)
β-alaninium iodide (IV)
(II)
C3H8ClNO2
125.55
(III)
C3H8BrNO2
170.01
(IV)
C3H8INO2
217.00
Formula
Mr
C3H8FNO2
109.10
Crystal system
Space group
a (Å)
b (Å)
c (Å)
Monoclinic
P21/c
8.268(2)
8.635(2)
6.759(1)
96.46(3)
479.5(2), 4
0.3×0.3×0.1
1.511
0.146
Orthorhombic Monoclinic
Monoclinic
P21/n
Pbca
P21/c
9.730(2)
7.412(2)
16.453(3)
5.6711(4)
12.6980(8)
8.9117(5)
102.093(3)
627.50(7), 4
6.735(1)
7.354(2)
13.327(3)
96.86(3)
655.3(2), 4
0.4×0.25×0.15
2.199
β
(°)
V(Å3), Z
1186.7(4), 8
Crystal size (mm3)
0.3×0.2×0.075 0.5×0.2×0.1
Dcalc(gcm-3)
1.405
0.541
528
1.800
6.454
336
(Mo Kα) (cm-1)
4.794
408
µ
F(000)
232
T(K)
hkl range
Reflections measured
Reflections unique
200(2)
±12, ±13, ±10
16435
1830
200(2)
200(2)
200(2)
±10, ±11, ±20
21759
±14, ±11, ±25 ±8, ±19, ±13
36900
2258
21217
2399
2507
1627
2040
2029
2169
Data with (Fo > 2
σ
(Fo))
Rint
0.0457
68
0.0362
75
0.0545
70
0.0283
69
Parameters refined
0.0342
0.0485
0.1062
0.018/1.268
0.0233
0.0504
0.0161
0.0479
R(F)* (for Fo > 2
σ
(Fo))
wR(F2)* (all reflections) 0.1017
Weighting parameters a,b 0.048/0.122
0.0066/0.3553 0.018/0.453
0.450/-0.481 0.840/-0.569
Δρfin (max/min) [e Å–3]
0.494/-0.249
0.373/-0.443
2
4 1/2
2
*
R1 = Σ Fo  - Fc  / Σ Fo, wR2 = [Σ w(Fo - Fc2)2 / Σ wFo ] ,w = 1/[σ2(Fo )+(a × P)2+ b × P],
2
P = (Fo +2Fc2)/3

Table 2. Selected bond lengths (Å), valence and torsion angles (°) in
β
-alaninium fluoride (I),
β-
alaninium chloride (II),
(I)
β
-alaninium bromide (III) and
(II)
β-alaninium iodide (IV).
(III)
(IV)
C1-O1
C1-O2
C1-C2
C2-C3
1.3098(10)
1.2214(10)
1.5081(11)
1.5129(11)
1.4858(11)
124.72(7)
122.48(7)
112.81(7)
113.75(7)
112.17(7)
-179.90(7)
63.21(9)
1.325(2)
1.211(2)
1.501(2)
1.510(3)
1.321(2)
1.2052(19)
1.503(2)
1.515(2)
1.487(2)
123.72(14)
123.51(15)
112.77(14)
112.61(13)
111.09(13)
-171.26(15)
59.24(18)
1.3099(18)
1.2237(16)
1.4978(19)
1.508(2)
C3-N1
1.489(2)
1.490(2)
O2-C1-O1
O2-C1-C2
O1-C1-C2
C1-C2-C3
N1-C3-C2
O1-C1-C2-C3
C1-C2-C3-N1
124.01(16)
124.76(16)
111.22(15)
114.38(15)
111.99(14)
174.9(1)
124.13(13)
121.58(13)
114.29(12)
112.67(12)
112.07(12)
-173.4(1)
-64.6(2)
66.5(2)
Table 3. Hydrogen bonds parameters for β-alaninium fluoride (I) (in Å and °).
D-H···A
D-H
0.993(19)
0.91
0.91
0.91
H···A
1.415(19)
2.21
2.35
2.12
D···A
<DHA
172.5(19)
139
122
140
O1-H1···F1
N1-H11···F1i
N1-H11···O2
N1-H12···F1ii
N1-H12···O2 iii
N1-H13···F1iv
2.4027(9)
2.9605(10)
2.9420(11)
2.8737(10)
2.845(11)
2.7007(11)
0.91
0.91
2.29
1.80
119
169
Symmetry code: (i) -x, y+1/2, -z+1/2; (ii) x, y+1, z; (iii) -x, y+1/2, -z+1/2; (iv) x, -y+3/2, z+1/2;
Table 4. Hydrogen bonds parameters for β-alaninium chloride (II) (in Å and °).
D-H···A
D-H
0.79(3)
0.91
0.91
0.91
0.91
0.91
H···A
2.22(3)
2.27
2.41
2.51
D···A
<DHA
172(3)
165
124
139
O1-H1···Cl1i
N1-H11···Cl1ii
N1-H12···O2
N1-H12···Cl1
N1-H13···O2iii
N1-H13···Cl1iv
3.007(2)
3.157(2)
3.013(2)
3.248(2)
3.135(2)
3.232(2)
2.55
2.555
122
132
Symmetry code: (i) x-1/2, -y+1/2, -z+1; (ii) –x+1, -y, -z+1; (iii) –x+1, -y+1, -z+1; (iv) x+1/2, -
y+1/2, -z+1.
Table 5. Hydrogen bonds parameters for β-alaninium bromide (III) (in Å and °).
D-H···A
D-H
0.78(3)
0.91
H···A
2.43(3)
2.56
D···A
3.2119(14)
3.3469(13)
<DHA
173(3)
145
O1-H1···Br1
N1-H11···Br1i

N1-H11···Br1ii
N1-H12···Br1iii
N1-H13···O2i
N1-H13···O2
0.91
0.91
0.91
0.91
2.98
2.46
2.10
2.34
3.368(1)
108
156
149
121
3.3072(14)
2.9177(17)
2.910()
Symmetry code: (i) –x+2, -y+1, -z+1; (ii) -x+1, -y+1, -z+1; (iii) -x+1, -y+1, -z+1.
Table 6. Hydrogen bonds parameters for β-alaninium iodide (IV) (in Å and °).
D-H···A
D-H
0.77(3)
0.89
0.89
0.89
H···A
1.88(3)
2.95
2.72
2.25
D···A
<DHA
178(3)
137
153
126
O1-H1···O2i
N1-H11···I1ii
N1-H12···I1
N1-H13···O2
2.6540(16)
3.6540(14)
3.5368(18)
2.8648(17)
Symmetry code: (i) –x+2, -y+1, -z+1; (ii) -x+1/2, y-1/2, -z+1/2.

Table 7. Crystal data and details of the refinements for (
β
-alaninium…β-alanine) bromide (V)
and ( -alaninium… -alanine) iodide (VI). Some data of (
β
β
β
-alaninium…
β
-alanine) chloride [9]
are provided for comparison.
(V)
C6H15BrN2O4
259.11
(VI)
C6H15IN2O4
306.10
2β-Ala.HCl [9]
C6H15ClN2O4
214.65
Formula
Mr
Crystal system
Space group
a (Å)
b (Å)
c (Å)
Monoclinic
C2/c
Monoclinic
C2/c
Monoclinic
C2/c
19.938(4)
5.1990(10)
10.719(2)
118.03(3)
980.8(3), 4
20.3113(4)
5.2250(1)
10.8983(2)
117.971(1)
1021.49(3), 4
0.43×0.4×0.3
1.685
20.9592(7)
5.2698(2)
11.0343(3)
117.0470(10)
1085.46(6), 4
0.30×0.20×0.075
1.873
β
(°)
V(Å3), Z
Crystal size (mm3)
Dcalc(gcm-3)
1.454
3.77
(Mo Kα) (cm-1)
4.013
2.940
µ
F(000)
456
528
600
T(K)
293(2)
296(2)
200(2)
hkl range
Reflections measured
Reflections unique
-25/26, -5/6, -13/14
2829
1143
-30/29, ±7, ±16
7692
1860
±32, ±8, ±16
18435
2073
1758
2003
Data with (Fo > 2
σ
(Fo))
Rint
0.0376
90
0.0286
0.0769
0.0582
93
0.0241
0.0694
0.0196
61
0.0144
0.0457
Parameters refined
R(F)* (for Fo > 2
σ
(Fo))
wR(F2)* (all reflections)
Weighting parameters a, b 0.0380/0.5316
0.0451/0.0451
0.0281/0.6842
0.83/-0.39
Δρfin (max/min) [e Å–3]
0.21/-0.23
0.64/-0.58
2
4 1/2
2
*
R1 = Σ Fo  - Fc  / Σ Fo, wR2 = [Σ w(Fo - Fc2)2 / Σ wFo ] ,w = 1/[σ2(Fo )+(a × P)2+ b × P],
2
P = (Fo +2Fc2)/3

Table 8. Selected bond lengths (Å) and angles (°) in (
β
-alaninium…β-alanine) bromide (V) at
296 K and (
β
-alaninium…β-alanine) iodide (VI) at 200 K.
(V)
(VI)
C1-O1
C1-O2
C1-C2
C2-C3
1.3070(13)
1.2238(14)
1.5148(14)
1.5112(15)
1.4884(16)
123.54(9)
122.03(9)
114.42(9)
113.42(9)
111.9(1)
1.3095(13)
1.2280(13)
1.5131(15)
1.5145(16)
1.4922(16)
123.20(10)
122.25(10)
114.54(9)
113.08(9)
111.73(9)
171.44(10)
63.57(13)
C3-N1
O2-C1-O1
O2-C1-C2
O1-C1-C2
C1-C2-C3
N1-C3-C2
O1-C1-C2-C3
C1-C2-C3-N1
170.4(1)
63.00(13)
Table 9. Hydrogen bonds parameters for (β-alaninium…β-alanine) bromide (V) (in Å and °) at
296 K.
D-H···A
D-H
H···A
D···A
<DHA
163(4)
131(2)
136(2)
158(2)
177(2)
O1-H1···O1i
N1-H11···O2
N1-H11···O1ii
N1-H12···Br1iii
N1-H13···O1iv
0.865(18)
0.85(2)
0.85(2)
0.87(2)
0.90(2)
1.632(18)
2.23(2)
2.46(3)
2.47(2)
1.96(2)
2.4723(17)
2.8535(13)
3.125(2)
3.2930(11)
2.8588(15)
Symmetry code: (i) -x+1/2, -y+1/2, -z+1; (ii) -x+1/2, y+1/2, -z+1/2; (iii) -x, -y+1, -z;
(iv) x, -y, z-1/2.
Table 10. Hydrogen bonds parameters for (β-alaninium…β-alanine) iodide (VI) (in Å and °) at
200 K.
D-H···A
D-H
0.84
0.91
0.91
0.91
0.91
H···A
D···A
<DHA
164
128
136
150
O1-H1···O1i
N1-H11···O2
N1-H11···O1ii
N1-H12···I1iii
N1-H13···O1iv
1.64
2.21
2.37
2.70
1.93
2.4613(18)
2.8634(14)
3.0932(15)
3.5116(10)
2.8356(14)
176
Symmetry code: (i) -x+1/2, -y+1/2, -z+1; (ii) -x+1/2, y+1/2, -z+1/2; (iii) -x, -y+1, -z;
(iv) x, -y, z-1/2.

# Crystals of β-alaninium fluoride, chloride, bromide and iodide are not isostructural
# β-alaninium iodide is a new salt with centrosymmetric (A+…A+) type dication
# 2β-Ala.HBr and 2β-Ala.HI are salts with (A+…A) type dimeric cation

A.M. Petrosyan, G. Giester, V.V. Ghazaryan, M. Fleck, “Halogenides of
Declaration of competing interest
β-alanine”
The authors declare that they have no known competing
financial interests or personal relationships that could have
appeared to influence the work reported in this paper.