Crystallization and characterization of the compounds Gly·MSO 4·mH2O (M = Mg2+, Mn2+, Fe2+, Co2+, Ni2+, Zn2+; M = 0, 3, 5, 6)

Article abstract of DOI:10.1016/j.molstruc.2012.02.068

The equilibrium crystallization of complex compounds of the type Gly·MSO₄·5H₂O with a structure derived from those of the crystallized double salts MSO₄·xH₂O, where x = 6, 7 was predicted and proven in the systems Gly-MSO ₄-H₂O (M = Mg²⁺, Mn²⁺, Fe ²⁺, Co²⁺, Ni²⁺ and Zn²⁺). It was predicted that stable octahedral complexes [M(H₂O)₆] ²⁺ and trans-[M(H₂O)₄(O-gly)₂] ²⁺, as well as [SO₄]^2- tetrahedra, which were the main building units of the crystallizing Gly·MSO₄· 5H₂O compounds (triclinic crystal system, space group P - 1), were predominating in these solutions. The vibrational spectra and the thermal behavior of the Gly·MSO₄·5H₂O compounds (M = Mg²⁺, Co²⁺, Zn²⁺) are in accord with the refined crystal structures. The cobalt compound displays antiferromagnetic behavior whereas the nickel and manganese compounds are ferromagnetic. In the manganese system where MnSO₄·H₂O (308 K) crystallizes, the only complex compound is the anhydrous Gly·MnSO ₄ with a polymeric type structure (trans-[Mn(SO₄) ₄(O-gly)₂]n2-). A new compound Gly·CoSO ₄·3H₂O was found in the cobalt system under unstable equilibrium conditions. Gly·CoSO₄·3H ₂O was proven to consist of two types of octahedra, trans-[Co(H ₂O)₄(O-gly)₂]²⁺ and trans-[Co(H ₂O)₂(SO₄)₂(O-gly)₂] ^2-, forming a chain structure (monoclinic crystal system, space group P2₁/c).

Full text of DOI:10.1016/j.molstruc.2012.02.068

Journal of Molecular Structure 1018 (2012) 113–121
Contents lists available at SciVerse ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Crystallization and characterization of the compounds GlyꢀMSO4ꢀmH2O (M = Mg2+,
Mn2+, Fe2+, Co2+, Ni2+, Zn2+; m = 0, 3, 5, 6)
a
b
b
b
c
a
S. Tepavitcharova a, , D. Rabadjieva , D. Havlícek , I. Nemec , P. Vojtíšek , J. Plocek , Z. Koleva
⇑
ˇ
ˇ
a Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Acad. G. Bontchev Str., Bl. 11, 1113 Sofia, Bulgaria
b Department of Inorganic Chemistry, Faculty of Science, Charles University in Prague, Albertov 2030, 128 40 Prague 2, Czech Republic
c
ˇ
ˇ
Institute of Inorganic Chemistry of the ASCR, v. v. i., 250 68 Rez u Prahy, Czech Republic
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 6 January 2012
Received in revised form 27 February 2012
Accepted 28 February 2012
Available online 15 March 2012
The equilibrium crystallization of complex compounds of the type GlyꢀMSO4ꢀ5H2O with a structure
derived from those of the crystallized double salts MSO4ꢀxH2O, where x = 6, 7 was predicted and proven
in the systems Gly–MSO4–H2O (M = Mg2+, Mn2+, Fe2+, Co2+, Ni2+ and Zn2+). It was predicted that stable
octahedral complexes [M(H2O)6]2+ and trans-[M(H2O)4(O-gly)2]2+, as well as [SO4]2ꢁ tetrahedra, which
were the main building units of the crystallizing GlyꢀMSO4ꢀ5H2O compounds (triclinic crystal system,
space group P ꢁ 1), were predominating in these solutions. The vibrational spectra and the thermal
behavior of the GlyꢀMSO4ꢀ5H2O compounds (M = Mg2+, Co2+, Zn2+) are in accord with the refined crystal
structures. The cobalt compound displays antiferromagnetic behavior whereas the nickel and manganese
compounds are ferromagnetic.
Keywords:
GlyꢀMSO4ꢀ5H2O
GlyꢀCoSO4ꢀ3H2O
Crystal structure
Vibrational spectra
Thermal behavior
Magnetic behavior
In the manganese system where MnSO4ꢀH2O (308 K) crystallizes, the only complex compound is the
anhydrous GlyꢀMnSO4 with a polymeric type structure ðtrans-½MnðSO4Þ ðO-glyÞ ꢂ2ꢁÞ.
4
2 n
A new compound GlyꢀCoSO4ꢀ3H2O was found in the cobalt system under unstable equilibrium condi-
tions. GlyꢀCoSO4ꢀ3H2O was proven to consist of two types of octahedra, trans-[Co(H2O)4(O-gly)2]2+ and
trans-[Co(H2O)2(SO4)2(O-gly)2]2ꢁ, forming a chain structure (monoclinic crystal system, space group
P21/c).
Ó 2012 Elsevier B.V. All rights reserved.
1. Introduction
Glycine-metal(II) sulfate compounds are also of interest. The
formation of different types of chemical compounds in the systems
The biological activity of some glycine-metal(II) chloride com-
pounds, such as 2GlyꢀZnCl2ꢀ2H2O [1–4] and 2GlyꢀMnCl2ꢀ2H2O [5],
attracts the interest to this group of compounds, as they supply
the organism with amino-acids and trace elements, both of them
very important for different living processes. Some of these com-
pounds are also interesting from a physical point of view as they
possess ferroelectric (triglycine sulfate, TGS [6] and triglycine sele-
nate, TGSe [7], GlyꢀAgNO3 [8], nGlyꢀMX2ꢀ2H2O (M = Mn, Co; X = Cl,
Br; n = 1, 2) [9–11]), pyroelectric, optical (TGS and TGSe), non-lin-
ear optical (3GlyꢀCaCl2 [12], 3GlyꢀZnCl2 [13]), and magnetic
(GlyꢀMnSO4 [14]) properties. The variation in the inorganic ligands
leads to changes in the chemical type, structure and physical prop-
erties of the compounds, but the studies are mainly limited to the
synthesis and structure characterization of the particular com-
pounds. There are no data for studies on elucidating the relation
synthesis conditions – chemical composition – crystal structure –
phase stability – physical behavior.
Gly–MSO4–H2O, depending on the M2+ ion, has been reported. Sev-
eral compounds have been synthesized, but not systematically
studied. Thus, the compound GlyꢀMgSO4ꢀ5H2O was obtained in
the magnesium system at 25–50 °C [15] or by solvent evaporation
at room temperature [16]. Four manganese compounds were ob-
tained: GlyꢀMnSO4 by crystallization in the manganese system at
30 °C [17] or by solvothermal synthesis [14]; nGlyꢀMnSO4 (n = 2,
4 and 6) – by water evaporation from the mixed solutions, but
the temperature was not indicated [18]. Three nickel compounds
were prepared in the nickel system: GlyꢀNiSO4ꢀ3H2O at 30 °C
[19], GlyꢀNiSO4ꢀ5H2O at 50 °C [20] and GlyꢀNiSO4ꢀ6H2O by slow
solution evaporation at room temperature [21], but the results
are contradictory. In the cobalt system, the synthesis of the com-
pound 2GlyꢀCoSO4 at 25 °C was reported [22], while Fleck and Bo-
´
haty prepared the compound GlyꢀCoSO4ꢀ5H2O by slow solution
evaporation at 22 °C for several weeks [23]. In the zinc system,
the compound 2GlyꢀZnSO4 was crystallized at 25 °C [24] while
´
Fleck and Bohaty prepared the compound GlyꢀZnSO4ꢀ3H2O by slow
solution evaporation at 22 °C for four months [25]. The compound
GlyꢀFeSO4ꢀ5H2O was crystallized from a hot concentrated mixed
solution at an excess of H2SO4 [26]. The crystal structure of the
⇑
Corresponding author. Tel.: +359 2 979 39 26; fax: +359 2 870 50 24.
E-mail address: stepav@svr.igic.bas.bg (S. Tepavitcharova).
0022-2860/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.molstruc.2012.02.068

114
S. Tepavitcharova et al. / Journal of Molecular Structure 1018 (2012) 113–121
latter, as well as the crystal structures of GlyꢀMgSO4ꢀ5H2O [16],
GlyꢀCoSO4ꢀ5H2O [23], GlyꢀNiSO4ꢀ6H2O [21], GlyꢀZnSO4ꢀ3H2O [25]
and the anhydrous GlyꢀMnSO4 [14] are known at room
temperature.
tic conditions, thus assuring a gradual rise in solution supersatura-
tion. Non-equilibrium crystallizing GlyꢀCoSO4ꢀ3H2O was obtained
for 1 day; the equilibrium crystallizing GlyꢀMSO4ꢀ5H2O was ob-
tained for a week.
The literature survey gives no explanation of the mentioned
contradictions; moreover, the crystallization processes including
the solutions stability in the systems Gly–MSO4–H2O are not eluci-
dated. Based on our knowledge, in many inorganic solutions there
is stable and metastable equilibrium. For example, as we have ear-
lier established, although all requirements for reaching a stable
thermodynamic equilibrium in magnesium solutions (the system
MgSO4–MgCl2–H2O), were apparently fulfilled, the crystallization
of higher hydrates as metastable phases was possible and could
not be avoided in each crystallization field of a stable lower hy-
drate of magnesium sulfate [27]. But what about glycine-metal(II)
sulfate solutions?
All experiments were carried out with A.R. reagents.
The composition of the liquid and the corresponding wet solid
phase was determined using titrimetric methods: complexometric
titration for the M2+ ions and neutralization titration in the pres-
ence of formaldehyde for Gly [29]. The accuracy of these analyses
was about 0.1–0.2%. The crystal water content was established
by gravimetric and TG analyses.
2.2. X-ray structure determination
The single crystals were mounted on glass fibers in random ori-
entation using Fluorolube oil. Nonius KappaCCD image plate dif-
fractometer was used for data collection (Table 4) at 150(1) K
(Cryostream Cooler Oxford Cryosystem) using graphite monochro-
mated Mo Ka-radiation (k = 0.71073 Å). The data were analyzed
using the HKL program package [30].
The structures were solved by direct methods and Fourier
method, and refined by full-matrix least-squares techniques
(SIR92 [31], SHELXL97 [32]). Scattering factors for neutral atoms
used were included in the program SHELXL97 [32]. All non-hydro-
gen atoms were refined anisotropically. The hydrogen atoms were
fixed at calculated positions (SHELXL97) [32] in all structures.
Some selected bond distances and angles are listed in Table 5;
structures are depicted on Figs. 2 and 3.
The purpose of this study was to throw light on the crystalliza-
tion processes in the GlyꢁMSO4ꢁH2O systems, where M = Mg2+
,
Mn2+, Fe2+, Co2+, Ni2+ and Zn2+ and to characterize the crystallized
compounds. Firstly, we studied and explained the equilibrium and
non-equilibrium crystallization in these systems. Secondly, we
studied the still unknown crystal structure of GlyꢀZnSO4ꢀ5H2O at li-
quid nitrogen temperature and the crystal structures of GlyꢀMg-
SO4ꢀ5H2O and GlyꢀCoSO4ꢀ5H2O at this temperature. And finally,
from the ‘‘non-equilibrium crystallizing compounds’’ we studied
the crystal structure of GlyꢀCoSO4ꢀ3H2O at 150 K.
2. Experimental
Additional material available from the Cambridge Crystallo-
graphic Data Center comprises the final atomic coordinates for
all atoms, the thermal parameters and a complete listing of bond
distances and angles for all solved structures. These data can be ob-
tained free of charge [33,34] using the deposition numbers CCDC
857073 for GlyꢀCoSO4ꢀ5H2O, CCDC 857074 for GlyꢀCoSO4ꢀ3H2O,
CCDC 857075 for GlyꢀMgSO4ꢀ5H2O and CCDC 857076 for
GlyꢀZnSO4ꢀ5H2O.
2.1. Chemical synthesis and analyses
The GlyꢁMSO4ꢁH2O systems were studied at 298 K for
M2+ = Co2+ or Zn2+ and at 308 K and partially at 263 K for
M = Mn2+ using the method of isothermal decrease of the supersat-
uration [28]. The equilibrium was attained under stirring for 24 h
at 298 K and 398 K, and for 1 week at 263 K.
GlyꢀMgSO4ꢀ5H2O was synthesized from Gly and MgSO4 solu-
tions at a molar ratio 1:1 at 298 K by the same method providing
equilibrium crystallization.
2.3. Vibrational spectra
The infrared spectra of the GlyꢀMSO4ꢀ5H2O (M = Mg2+, Co2+
,
The diffraction-quality single crystals of the compounds were
obtained from aqueous solutions of glycine and the corresponding
MSO4 by the method of slow water evaporation at 298 K under sta-
Zn2+) compounds were recorded by Nujol or fluorolube mull (KBr
and AgCl windows) techniques on a Nicolet 6700 FTIR spectrome-
ter with 2 cmꢁ1 resolution and Happ–Genzel apodization in the
400–4000 cmꢁ1 region.
Gly
The Raman spectra of the same polycrystalline samples were re-
corded on a Nicolet 6700 FTIR spectrometer equipped with Nicolet
Nexus FT Raman module (2 cmꢁ1 resolution, Happ-Genzel
100
75
Gly.MnSO4
50
25
Gly.MSO4 .5H2O
2+
(M=Zn2+, Co
)
MSO
4
H2O
CoSO4.7H2O
25
100
50
75
MnSO4.H2O
ZnSO4.7H2O
Fig. 1. Solubility diagrams of the Gly–MSO4–H2O (M = Co2+ (j), Zn2+ (N)at 298 K
and Mn2+ (s) at 308 K) systems (in mass%).
Fig. 2. Crystal structure of GlyꢀZnSO4ꢀ5H2O with the atom numbering scheme and
isotropic displacement ellipsoids.

S. Tepavitcharova et al. / Journal of Molecular Structure 1018 (2012) 113–121
115
Fig. 3. Crystal structure of GlyꢀCoSO4ꢀ3H2O with the atom numbering scheme and isotropic displacement ellipsoids.
apodization, 1064 nm Nd:YVO4 laser excitation, 300–400 mW
power at the sample) in the 100–3700 cmꢁ1 region.
The N,O-deuterated analogues of the GlyꢀMSO4ꢀ5H2O crystals
were prepared by repeated recrystallization of natural compounds
from D2O (99%) in a desiccator over KOH.
crystal. Crystallization, co-crystallization and re-crystallization
simultaneously take place until the system equilibrium is attained.
In the case when MSO4 is the predominating salt in the system
under standard conditions (298 K, atmospheric pressure) equilib-
rium crystallization of stable MSO4.7H2O occurs. MnSO4.7H2O
crystallizes at a lower temperature: 281.6–261.6 K. Under these
standard conditions only metal(II) aqua-complexes and SO24ꢁ ions
that have high thermodynamic activity take part in the crystalliza-
tion process and build up the structure of MSO4.7H2O containing
isolated [M(H2O)6]2+ octahedra, [SO4]2ꢁ tetrahedra and free H2O
molecules situated among them, connected by hydrogen bonds
[35]. The different spatial sticking of the polyhedra determines
whether a monoclinic or an orthorhombic structure appears. One
free H2O molecule is connected with each [M(H2O)6]2+ octahedron
in the orthorhombic structure. In the monoclinic structure two free
H2O molecules are connected with the one type of octahedra,
[M(H2O)6]2+, while the H2O molecules of the other type of octahe-
dra are connected with SO4-groups only. At temperatures above
303–313 K some of these sulfates lose the free H2O molecules
and crystallize as hexahydrates of monoclinic structure. The
crystal structure of MnSO4ꢀH2O consists of mixed octahedra
2.4. Thermal analysis
The GlyꢀMSO4ꢀ5H2O (M = Mg2+, Co2+ and Zn2+) compounds were
investigated by TG and DT analysis in atmospheric air within the
range 293–773 K. The studies were performed with a Paulik-Paulik
Erdey 1500 apparatus (type 3427), at a heating rate of 10 °C minꢁ1
,
sample weight of 180–190 mg and sensitivity of 1/200 mg.
2.5. Magnetic susceptibility
The magnetic susceptibility (
v
) of the compounds GlyꢀMSO4ꢀ5H2O
(M = Mn2+, Co2+ and Ni2+) was studied on powder samples in the
temperature range 288–373 K. The measurements were performed
on a Faraday-type magnetic susceptibility balance with magnetic
field of 7 kOe. The error of the magnetic susceptibility data was
up to 5%. The experimental data were diamagnetically corrected.
2+
Mn(H2O)2(SO4)4 [36].
The increased glycine concentration leads to the formation of
mixed complexes. When the thermodynamic activity of the stable
mixed metal(II) aqua-glycine and metal(II) aqua-glycine-sulfate
complexes is sufficiently high, they can also participate in the crys-
tallization process. The sticking of such mixed polyhedra in the
structure of the crystallizing compounds requires additional space
for the residue of each glycine zwitterion. Mixed polyhedra may
completely or partially replace in the structure of MSO4.7H2O: (i)
one [M(H2O)6]2+ octahedron only (as, e.g. in GlyꢀNiSO4ꢀ6H2O [20]),
and (ii) a [M(H2O)6]2+ octahedron along with the neighboring H2O
molecules, the latter assumption being more probable. The partici-
pation of the mixed polyhedra [M(H2O)5Gly]2+ or [M(H2O)4(Gly)2]2+
is most probable and as a result pentahydrates would crystallize. If
[M(H2O)5Gly]2+ octahedra participate, a compound with a structure
derivative of the orthorhombic MSO4.7H2O is possible. When
[M(H2O)4(Gly)2]2+ octahedra participate, a structure derivative of
the monoclinic MSO4.7H2O would be formed, which is more stable
for steric reasons. The participation of any other less stable mixed
polyhedra, e.g. [M(H2O)2(SO4)2Gly2]2ꢁ, [M(H2O)3(SO4)Gly2]0, will
lead to unstable, non-equilibrium crystallization.
The Curie constant (C), paramagnetic Curie temperature (H) and
effective magnetic moment (leff) were calculated.
3. Results and discussion
3.1. Equilibrium and non-equilibrium crystallization in the
GlyꢁMSO4ꢁH2O systems
Glycine mainly exists as a zwitterion in aqueous solutions. In
electrolyte solutions of the GlyꢁMSO4ꢁH2O systems, where
M = Mg2+, Mn2+, Fe2+, Co2+, Ni2+ and Zn2+, different simple and
mixed metal complexes such as metal(II) aqua-glycine complexes,
metal(II) aqua-glycine-sulfate complexes, metal(II) aqua-sulfate
complexes, metal(II) aqua-complexes, free SO24ꢁ ions, glycine zwit-
terions and M2+ ions are to be expected. The coordination of one or
more glycine molecules around the M2+ ion may occur through an
O or an N atom or through both simultaneously, the first one being
more probable for the systems considered where glycine is a zwit-
terion. Various crystallochemical and kinetic factors determine the
crystallization process. It starts when some of the complexes exist-
ing in the solution are of sufficiently high activity to reach and sur-
pass the solubility product of the crystallizing salt. This means that
important for the crystallization process is the activity of definite
entities in the solution (complexes, molecules or simple ions) that
are able to be incorporated directly or with minor changes in the
On this basis we expected the presence of a broad crystalliza-
tion field of GlyꢀMSO4ꢀ5H2O (1:1:5) compounds in all studied sys-
tems along with the crystallization field of MSO4ꢀxH2O (x = 6,7).
The crystal structure of these compounds would be built up of
[M(H2O)4(Gly)2]2+ and [M(H2O)6]2+ octahedra and [SO4]2ꢁ tetrahe-

116
S. Tepavitcharova et al. / Journal of Molecular Structure 1018 (2012) 113–121
Table 1
Table 3
Solubility in the Gly–CoSO4–H2O system at 298 K.
Solubility in the Gly–MnSO4–H2O system at 308 K.
Liquid phase (mass%)
Wet solid phase (mass%)
Solid phase
Liquid phase (mass%)
Gly MnSO4
23.1 0.0
Wet solid phase (mass%)
Solid phase
Gly
CoSO4
Gly
CoSO4
Gly
MnSO4
20.1
20.9
22.5
24.6
24.8
24.6
22.0
18.8
13.3
0.0
6.10
11.5
13.4
13.5
13.5
12.9
13.9
18.2
23.7
32.8
37.1
30.1
27.1
–
–
Gly
Gly
Gly
Eutonic
Eutonic
Eutonic
GlyꢀCoSO4ꢀ5H2O
GlyꢀCoSO4ꢀ5H2O
GlyꢀCoSO4ꢀ5H2O
GlyꢀCoSO4ꢀ5H2O
GlyꢀCoSO4ꢀ5H2O
Eutonic
–
–
Gly
Gly
Gly
Eutonic
70.7
78.6
62.3
45.7
34.2
23.1
22.4
21.8
21.0
21.2
6.38
0.25
–
2.00
3.05
17.9
28.9
38.4
42.2
41.0
42.9
45.5
46.8
50.8
50.6
–
25.4
27.8
30.4
23.8
20.0
11.4
10.0
9.00
7.50
5.20
4.34
3.66
3.21
2.82
2.51
2.03
1.80
3.79
7.30
13.73
7.60
6.34
7.45
8.45
9.22
10.9
13.1
14.6
18.3
21.2
24.8
28.8
36.5
37.2
91.0
92.5
43.1
31.8
28.5
28.0
27.7
25.0
22.8
25.2
24.5
24.2
28.0
25.0
31.6
14.3
0.0
0.89
1.00
38.3
55.0
44.9
53.7
54.3
48.2
44.8
52.6
51.7
53.0
59.9
56.0
63.8
69.2
89.4
GlyꢀMnSO4
GlyꢀMnSO4
GlyꢀMnSO4
GlyꢀMnSO4
GlyꢀMnSO4
GlyꢀMnSO4
GlyꢀMnSO4
GlyꢀMnSO4
GlyꢀMnSO4
GlyꢀMnSO4
GlyꢀMnSO4
GlyꢀMnSO4
Eutonic
6.10
4.80
4.02
1.96
0.0
CoSO4.7H2O
CoSO4.7H2O
MnSO4ꢀH2O
Table 2
Solubility in the Gly–ZnSO4–H2O system at 298 K.
Liquid phase (mass%) Wet solid phase (mass%)
Solid phase
with different water activity. At low water activity the [Co(H2O)6]2+
complexes decrease at the expense of mixed complexes with dif-
ferent stability in these supersaturated solutions. Formation of lo-
cal supersaturation centers at low solution concentration that act
as centers for nucleation of non-equilibrium crystals is typical for
dense solutions where mass transport goes slowly. In our previous
studies we have established equilibrium and non-equilibrium crys-
tallization in other two magnesium sulfate systems as well,
MgSO4–MgCl2–H2O [27] and Na+, Mg2+/Clꢁ, SO42ꢁ=H2O [37], where
formation of stable and metastable solutions also takes place. The
crystallization kinetics was found to be proportional to the super-
saturation [38].
The formation of coordination polyhedra is determined by the
metal–ligand interactions, ligand–ligand repulsions and interac-
tions between neighboring polyhedra. The electronic configuration
of the metal ion, in particular the crystal field stabilization energy
(CFSE) and the Jahn–Teller effect, also influence the positional sym-
metry of the ligands [39]. The equilibrium arrangement of the ions
in the crystal structure is determined by the total energy balance
between the size and charge of the ions, the energy of the me-
tal–ligand bonds and the energy determined by the positional
symmetry of the ligand [35]. Both the coordination behavior of
M2+ ions in the mixed aqueous sulfate–glycine solutions and the
formation of stable complexes are responsible for the salt crystal-
lization. The availability of a sufficient concentration (activity) of
complexes which can be incorporated in the crystal structure dur-
ing the crystal growth process through appropriate sticking, almost
unchanged or with small changes, determines the crystallization of
the respective compound. In the cases of Mg2+(p6), Mn2+(d5 high
spin) and Zn2+(d10) (CFSE = 0) the formation of stable mixed octa-
hedral complexes takes place to a high extent due to the possible
large-range deformations which enable a ready participation in
the crystallization processes. In contrary, the distorted complexes
of Fe2+(d6), Co2+(d7), Ni2+(d8) and Cu2+(d9), due to the CFSE –0
and the Jahn–Teller effect, bear less angular deformations and in
viscous solutions a process of coordination/re-coordination occurs
significantly slower through formation of less stable mixed com-
plexes. The latter seem to be involved in local non-equilibrium
crystallization.
Gly
ZnSO4
Gly
ZnSO4
20.1
20.4
21.1
23.0
24.3
24.9
25.3
25.4
23.0
20.3
18.2
16.0
0.0
4.05
9.67
19.3
25.9
26.9
27.6
27.5
27.9
28.2
29.6
31.0
37.3
39.5
37.4
36.7
–
–
Gly
Gly
Gly
Gly
Gly
Gly
Eutonic
Eutonic
GlyꢀZnSO4ꢀ5H2O
GlyꢀZnSO4ꢀ5H2O
GlyꢀZnSO4ꢀ5H2O
GlyꢀZnSO4ꢀ5H2O
GlyꢀZnSO4ꢀ5H2O
Eutonic
94.8
79.1
76.0
78.0
82.0
49.3
35.2
23.1
23.0
23.0
23.0
22.0
2.86
0.23
–
0.42
2.86
6.10
7.21
6.78
23.4
40.4
46.7
47.0
47.8
49.0
49.2
55.1
53.2
–
9.72
7.90
2.52
0.0
ZnSO4.7H2O
ZnSO4.7H2O
dra. Only in the manganese system with MnSO4ꢀH2O crystalliza-
tion field (at 308 K), the crystallization of GlyꢀMnSO4ꢀ5H2O is
improbable. In this case the formation of the anhydrous compound
GlyꢀMnSO4, with a structure most probably derivative of that of
MSO4ꢀH2O is expected. The compound GlyꢀMnSO4ꢀ5H2O should
crystallize at about 282–285 K.
The results of our studies on the discussed systems confirmed
the correctness of the predicted compounds in the case of equilib-
rium crystallization. Our data on the cobalt (Fig 1 and Table 1) and
zinc (Fig 1 and Table 2) systems at 298 K, as well as on the manga-
nese system at 263 K (Fig. 1 and Table 3) evidenced the equilibrium
crystallization of the compounds GlyꢀMSO4ꢀ5H2O (M = Mn2+, Co2+
and Zn2+). In the manganese system we proved the crystallization
of an anhydrous compound, GlyꢀMnSO4, at 308 K. This preparation
procedure is easier than that reported by Weng et al. [14]. The data
of Balkunova et al. [15] on the magnesium system at 323 K con-
firmed our prediction about MSO4.6H2O.
During slow solvent evaporation in the cobalt system we estab-
lished an initial quick non-equilibrium crystallization of good dif-
fraction-quality single crystals of the compound GlyꢀCoSO4ꢀ3H2O
and solved its structure. This compound is not thermodynamically
stable in the solution and owing to simultaneous processes of crys-
tallization, co-crystallization and re-crystallization, quick transfor-
mation and equilibrium crystallization of GlyꢀCoSO4ꢀ5H2O was
observed. The differences in the crystallization kinetics of these
two cobalt compounds we explained by the different associations
between Co2+, SO42ꢁ ions, glycine and H2O molecules in solutions
There are contradictory data in the literature about the crystal-
lization in the GlyꢁNiSO4ꢁH2O system. Moldobaev et al. [19] re-
ported the preparation of the compound GlyꢀNiSO4ꢀ3H2O at 303 K
which we believe took place under non-equilibrium conditions.
Contradictory, Alymkulova et al. [20] have reported the crystalliza-

S. Tepavitcharova et al. / Journal of Molecular Structure 1018 (2012) 113–121
117
Table 4
Experimental data for the single-crystal X-ray diffraction studies of the compounds at 150(1) K.
GlyꢀMgSO4ꢀ5H2O
GlyꢀCoSO4ꢀ5H2O
GlyꢀZnSO4ꢀ5H2O
GlyꢀCoSO4ꢀ3H2O
Formula (sum.)
M (g molꢁ1
C4H30N2O22S2Mg2
571.06
C4H30N2O22S2Co2
640.30
C4H30N2O22S2Zn2
653.22
C2H11NO9SCo
284.11
)
Cryst. dim.(mm)
Shape
Color
Space group
a (Å)
b (Å)
0.3 ꢃ 0.5 ꢃ 05
0.4 ꢃ 0.4 ꢃ 0.5
0.2 ꢃ 0.4 ꢃ 0.5
Irregular
Colorless
P ꢁ 1 (No. 2)
5.9620(1)
6.7810(2)
13.1930(4)
85.111(1)
83.240(2)
82.971(2)
524.32(2)
1
0.3 ꢃ 0.3 ꢃ 0.6
Prism
Prism
Prism
Colorless
P ꢁ 1 (No. 2)
5.9780(2)
6.7420(2)
13.3140(4)
85.365(2)
83.008(2)
83.062(2)
527.52(3)
1
Red
Red
P ꢁ 1 (No. 2)
5.9660(2)
6.7390(2)
13.2690(3)
85.256(2)
83.352(2)
83.316(1)
524.99(3)
1
P21/c (No. 14)
9.0070(2)
10.5240(3)
10.2750(3)
90
112.595(16)
90
899.21(4)
4
c (Å)
a
(°)
b (°)
c
(°)
U (Å3)
Z
Dc (g.cmꢁ3
l
)
1.798
0.419
2.025
1.886
2.069
2.594
2.099
2.173
(mmꢁ1
)
F (000)
300
330
293
580
h (°) of data coll.
Index ranges
No. of refls measured
3.0–27.6
ꢁ7, 7; ꢁ8, 8; ꢁ17, 17
4513
3.10–27.55
ꢁ7, 7; ꢁ8, 8; ꢁ17, 17
9977
1.6–27.5
ꢁ7, 7; ꢁ8, 8; ꢁ17, 17
9189
2.9–27.5
ꢁ11, 11; ꢁ13, 13;ꢁ13, 13
10,219
R
r
0.0108
0.0112
0.0107
0.0101
No. of refls. obs. [I P 2
No. of ind. refls.
Rint
r
(I)]
2213
2419
0.012
2308
2402
0.043
2229
2389
0.029
1814
2409
0.029
Data, restrs., params.
A; B
2419/0/146
0.0299, 0.3411
1.078
0.0252, 0.0717
0.001
2402/0/146
0.0244, 0.3868
1.120
0.0230, 0.0612
0.000
2389/0/149
0.0170, 05311
1.074
0.0215, 0.0535
0.000
2409/0/128
0.0357, 0.9549
1.015
0.0257, 0.0755
0.000
Goodness-of-fit on F2I
Final R, R0 [I > 2
r
(I)]
Max. shift/e.s.d.
Largest differ. peak and hole (e/Å3)
0.333; ꢁ0.458
0.377; ꢁ0.712
0.592; ꢁ0.447
0.59; ꢁ0.57
tion of GlyꢀNiSO4ꢀ5H2O at 323 K under obviously equilibrium
conditions. Peterkova et al. [21] described the compound
GlyꢀNiSO4ꢀ6H2O obtained under standard conditions by slow evap-
oration of the solution, equilibrium crystallization being obviously
not achieved.
GlyꢀNiSO4ꢀ6H2O (monoclinic, space group P21/c) is not isostructural
with the compounds mentioned above. This structure consists of
different coordination octahedra ([Ni(H2O)5(O-gly)]2+, symmetry
roughly C4v), as well as of non-coordinated [SO4]2ꢁ tetrahedra.
The octahedra are relatively regular (
D = 0.012(4) Å) [21].
´
Fleck and Bohaty [25] have reported the non-centrosymmetric
The bond distances in the type 1-polyhedra in the isostructural
compounds are in the range 2.044–2.103 Å for Mg, 2.047–2.129 Å
for Co and 2.065–2.133 Å for Zn. The irregularity of the type 1-octahe-
compound GlyꢀZnSO4ꢀ3H2O, also obtained by the method of slow
solution evaporation for few months.
dra increases in the order Mg (D = 0.059(2) Å) < Zn (D = 0.068(3) Å) <
Co ( = 0.082(2) Å). The bond distances Me–OH2 in the type 2-octa-
D
3.2. Crystal structures
hedra nearly fall within the ranges mentioned above, except for the
Zn-complex (difference 0.03 Å). The coordination bonds M–O-gly
are rather longer: 2.125(1) Å, 2.141(1) Å, 2.178(1) Å for Mg, Co, Zn,
respectively (see Table 5).
Finally, three water molecules were found to be situated closer
to the metal ion than the remaining two water molecules in all
compounds GlyꢀMSO4ꢀ5H2O (M = Mg2+, Co2+ and Zn2+), which is
in accordance with the thermal behavior of the GlyꢀMSO4ꢀ5H2O
compounds.
The building units of the structure are kept together by a net-
work of hydrogen bonds. The shortest hydrogen bonds of the type
Oꢀ ꢀ ꢀO are between a water molecule and glycine (2.646 Å), a bit
longer H-bonds of the same type are between water molecules
and sulfates (2.701–2.816 Å). Relatively strong hydrogen bonds of
the Nꢀ ꢀ ꢀO type were found between two glycine molecules
(2.858–2.886 Å) and between glycine and sulfate (2.887 Å).
3.2.1. GlyꢀMSO4ꢀ5H2O compounds
The compounds GlyꢀMSO4ꢀ5H2O (M = Mg2+, Mn2+, Co2+ and
Zn2+) were found to be isostructural (see Table 4a); they crystallize
in a triclinic crystal system, space group P ꢁ 1. Their crystal struc-
ture is built up of two different discrete octahedra; type 1
([M(H2O)6]2+
,
symmetry roughly Oh) and type
2
(trans-
[M(H2O)4(O-gly)2]2+, symmetry roughly D4h), (Fig. 2). The two gly-
cine zwitterions are monodentately trans-coordinated to the M2+
ion by the oxygen atom. On the other hand, previously reported
Table 4a
Cell parameters a, b, c (in Å; first row),
a
, b, c
(in °; second row), cell volume (U in Å3)
for the studied crystal structures.
Compound
U
a;
a
b; b
c; c
GlyꢀMgSO4ꢀ5H2O
527.5
5.9780(2)
85.365(2)
5.9660(2)
85.256(2)
5.9620(1)
85.111(1)
6.011(2)
85.44(3)
9.0070(2)
90
6.7420(2)
83.008(2)
6.7390(2)
83.352(2)
6.7810(2)
83.240(2)
6.828(2)
13.3140(4)
83.062(2)
13.2690(3)
83.316(1)
13.1930(4)
82.971(2)
13.484(4)
83.19(3)
GlyꢀCoSO4ꢀ5H2O
GlyꢀZnSO4ꢀ5H2O
GlyꢀMnSO4ꢀ5H2Oa
GlyꢀCoSO4ꢀ3H2O
525.0
524.3
544.4
899.2
3.2.2. GlyꢀMSO4ꢀ3H2O compounds
The compound GlyꢀCoSO4ꢀ3H2O crystallizes in a monoclinic
crystal system, space group P21/c (Table 4). The crystal structure
is built up of two types of connected mixed octahedra, type 2
(trans-[Co(H2O)4(O-gly)2]2+, symmetry roughly D4h) and type 3
(all trans-[Co(H2O)2(SO4)2(O-gly)2]2ꢁ, symmetry roughly C2v) form-
ing infinite chains (Fig. 3). The connecting glycine zwitterions are
monodentately coordinated to every two Co2+ ions by the two
83.13(3)
10.5240(3)
112.595(2)
10.2750(3)
90
a
From powder data at 292 K.

118
S. Tepavitcharova et al. / Journal of Molecular Structure 1018 (2012) 113–121
oxygen atoms from their carboxyl groups, as was previously
observed in the structures of GlyꢀZnCl2 [40] and GlyꢀZnSO4ꢀ3H2O
[25]. In contrary to the structure of GlyꢀCoSO4ꢀ3H2O, the chain
structure of the previously reported compound GlyꢀZnSO4ꢀ3H2O
[25] is built up of only one type of connected mixed octahedra
fac-[Zn(H2O)3(SO4)(O-gly)2]o. The geometry of these polyhedra is
quite different, containing two Zn–O-gly bonds in cis- position
forming the chain mentioned above. The positions of the water
molecules are more regular (
D = 0.019(3) Å) than in the compound
GlyꢀCoSO4ꢀ3H2O discussed here.
The bond distances M–OH2 in the type 2-octahedra fall within
the range mentioned above for the Co-compound. The coordina-
tion bond M–O-gly is rather shorter, 2.089(1) Å, than was observed
in GlyꢀCoSO4ꢀ5H2O (see Table 5).
The bond distances M–OH2 in the type 3-octahedra also fall
within the range for type 2-octahedra; the bond M–O-gly is as that
in the second coordination octahedron in this structure. The bridg-
ing carboxylate ion is therefore highly symmetrical. The bond
distance Co-OSO3 is 2.079(2) Å (compared with 2.051(2) Å in
GlyꢀZnSO4ꢀ3H2O [25]).
Fig. 5. FTIR spectra (compiled from Nujol and fluorolube mulls) of the compounds
GlyꢀMSO4ꢀ5H2O (M = Mg2+, Co2+ and Zn2+).
on recent papers [42,43] concerning vibrational spectra of glycine
and our paper [40] focused on the glycine complexes of ZnCl2.
The dense network of hydrogen bonds plays an important role
in this structure as well. The shortest H-bonds of Oꢀ ꢀ ꢀO type are be-
tween water molecules and sulfate anions (2.695–2.878 Å) and one
‘‘intramolecular’’ hydrogen bond (between particles in one chain)
is between water and glycine (2.705 Å). ‘‘Intermolecular’’ interac-
tions (between particles in different chains) water–glycine and
water–water are much longer (3.021 and 3.029 Å). Quite strong
‘‘intramolecular’’ H-bonds of the Nꢀ ꢀ ꢀO type were found between
glycine and sulfate (2.766 Å); ‘‘intermolecular’’ H-bonds of the
same type are a bit longer (2.805–2.948 Å).
+
The assignment of deformation vibrations of the NH3 group was
confirmed by recording and analysis of spectra of N,O-deuterated
analogues. Presented assignment of the bands of stretching and
out-of-plane bending vibrations of the N–H and O–H groups in-
volved in the hydrogen bonds is based on the correlation curves
[44,45] concerning the vibrational bands positions and the appro-
priate hydrogen bond lengths. Vibrational manifestations (i.e.
stretching M–O vibrations) connected with formation of octahe-
dral Co2+, Mg2+ and Zn2+ complexes were assigned according to pa-
pers [46–49] dealing with related coordination compounds.
Recorded vibrational spectra of GlyꢀMSO4ꢀ5H2O (M = Mg2+, Co2+
and Zn2+) are fully in accord with their refined crystal structures –
i.e. isostructural sulfates of octahedral Me2+ complexes with
monodentate glycine and aqua ligands. The minor differences were
observed in the IR spectra of the compounds in the region of O–H
and N–H stretching vibrations, which are associated with slightly
different hydrogen bonding schemes, and in the region of Me–O
stretching vibrations.
The presence of three different ligands around the Co2+ ions as
well as the common corners of the octahedra destabilize the struc-
ture (third Pauling rule [41]). In comparison with GlyꢀCoSO4ꢀ5H2O,
GlyꢀCoSO4ꢀ3H2O has to be less stable and we obtained it only under
´
non-equilibrium conditions. By the same reason Fleck and Bohaty
[25] have obtained the less stable GlyꢀZnSO4ꢀ3H2O instead of the
stable GlyꢀZnSO4ꢀ5H2O.
3.3. Vibrational spectra
The existence of glycine molecules in the form of monodentately
coordinated zwitterions is reflected particularly in the presence of
the bands of antisymmetric and symmetric stretching
The FTIR and FT Raman spectra of GlyꢀMSO4ꢀ5H2O (M = Mg2+
,
Co2+, Zn2+) recorded at room temperature are depicted in Figs. 4
and 5. Owing to the intense fluorescence of the GlyꢀCoSO4ꢀ5H2O
crystals at 1064 nm (excitation laser used for the FT Raman mea-
surement) only FTIR spectra of this compound were recorded and
discussed. The assignment of the observed bands (Table 6) is based
COO- (1640–1370 cmꢁ1 region) and deformational NH3 (1700–
+
1470 cmꢁ1 region) vibrations. The assignment of these very impor-
tant bands was confirmed by the study of N,O-deuterated
analogues.
The observed vibrational manifestation of sulfate anions was
compared to the results of the performed correlation analysis
(see Table 7). The number of recorded internal bands of anions is
anyway more consistent with the lowering of Td sulfate symmetry
to C3v symmetry rather than with crystallographic Ci factor group
symmetry.
3.4. Thermal behavior of the GlyꢀMSO4ꢀ5H2O
The data from the thermal analyses of the compounds
GlyꢀMSO4ꢀ5H2O (M = Mg2+, Co2+, Zn2+) at 293–773 K are shown
in Table 8. In contrary to Balkunova et al. [15], a two-stage
dehydration and subsequent decomposition to MSO4 in different
temperature ranges was established for all compounds. Our
results are in agreement with the structural data (Table 5), which
point to the presence of two longer and three shorter Me–Ow
interatomic distances in the octahedra [M(H2O)6]2+ and trans-
Fig. 4. FT Raman spectra of the compounds GlyꢀMSO4ꢀ5H2O (M = Mg2+, Zn2+).
[Me(H2O)4(O-gly)2]2+
.

S. Tepavitcharova et al. / Journal of Molecular Structure 1018 (2012) 113–121
119
Table 5
Selected bond lengths (Å) in studied compounds.
Mg1
Co1
Zn1
Mg2
Co2
Zn2
For isostructural compounds GlyꢀMSO4ꢀ5H2O
M1–O11
M1–O12
M1–O1
2.0358(10)
2.0768(10)
2.1252(9)
2.0358(10)
2.0768(10)
2.1252(9)
2.0370(12)
2.1241(11)
2.1409(12)
2.0370(12)
2.1241(11)
2.1409(12)
2.0320(13)
2.0975(12)
2.1775(12)
2.0320(13)
2.0975(12)
2.1775(12)
M2–O21
M2–O22
M2–O23
M2–O21b
M2–O22b
M2–O23b
2.0443(10)
2.0520(10)
2.1029(10)
2.0443(10)
2.0520(10)
2.1029(10)
2.0473(12)
2.0914(11)
2.1285(12)
2.0473(12)
2.0914(11)
2.1285(12)
2.0649(14)
2.0702(12)
2.1332(13)
2.0649(14)
2.0702(12)
2.1332(13)
M1–O11a
M1–O12a
M1–O1a
Co1
Co2
For compound GlyꢀCoSO4ꢀ3H2O
Co–O11
Co–O12
Co–O1
2.0879(15)
Co–O1S
Co–O2
Co–O21
Co–O1Sd
Co–O2d
Co–O21d
2.0786(15)
2.0941(14)
2.0676(15)
2.0786(15)
2.0941(14)
2.0676(15)
2.0891(14)
2.0893(14)
2.0879(15)
2.0891(14)
2.0893(14)
Co–O11c
Co–O12c
Co–O1c
a
b
c
1 ꢁ x, 2 ꢁ y, ꢁz.
1 ꢁ x, 1 ꢁ y, 1–z.
ꢁx, ꢁy, ꢁz.
d
ꢁx, 1 ꢁ y, ꢁx.
Table 6
FTIR and FT Raman spectra of GlyꢀMSO4ꢀ5H2O (M = Mg2+, Co2+ and Zn2+).
GlyꢀMgSO4ꢀ5H2O
GlyꢀCoSO4ꢀ5H2O
GlyꢀZnSO4ꢀ5H2O
Assignment
IR
RA
IR
IR
RA
180w
210m
238m
Lattice mode
210m
247m
390w
456s
429w
447w
469w
529m
q
CCN
456s
455w
454w
531m
m2SO4
?
q
m
m
x
m
528m
532m
551m
531m
COOꢁ
Co–O
Mg–O,
COOꢁ
Zn–O,
COO-
572m
602m
x
COOꢁ
COOꢁ
576sh
605m
639m
575sh
603m
585sh
603s
631m
646m
x
601s
625m
648m
x
m4 SO4
O–H(ꢀ ꢀ ꢀO),
647m
672m
705mb
791w
889w
913w
984w
639m
c
c N–H(ꢀ ꢀ ꢀO)
703mb
807w
889w
912w
983w
700mb
790sh
888w
913w
983w
892s
907w
985vs
892s
909w
985vs
ms CCN
q CH2
m1 SO4
mas CCN
m3 SO4
1021w
1078m
1100m
1142w
1306m
1329m
1 396m
1436m
I489w
1600wb
1633wb
1022w
1080m
1101m
1141w
1308w
1329m
1392m
1434m
1487w
1592w
1615wb
1072s
1100s
1075s
1101s
1074s
1100s
q
NHþ3
1306w
1334m
1397m
1437w
1493m
1593m
1632m
1670sh
1705w
2320wb
2400wb
2965sh
1307w
1334m
1389m
1433w
1491m
1590m
1624m
1307w
I334m
1393m
1434w
1492m
1589m
1623m
x
s
CH2
CH2
mas COOꢁ
d CH2
dsNHþ3
das NHþ3
m3 COOꢁ
das.NHþ3
1695w
2320wb
1692w
2320wb
2400wb
2955mb
?
?
2955mb
m
m
N–H(ꢀ ꢀ ꢀO)
2998m
3037w
3255wb
2997m
3038w
3230wb
sCH2
mas CH2
O–H(ꢀ ꢀ ꢀO), m N–H(ꢀ ꢀ ꢀO)
3070sh
3250sb
3330sb
3230sb
3290sh
3240sb
3290sh
m
The cobalt compound is the most stable one. The splitting of the
peak during the second stage of dehydration of the zinc compound
is probably caused by evaporation accompanying the dehydration
at about 373 K.

120
S. Tepavitcharova et al. / Journal of Molecular Structure 1018 (2012) 113–121
Table 7
Correlation analysis of internal modes of SO24ꢁ anions in studied GlyꢀMSO4ꢀ5H2O (M = Mg2+, Co2+ and Zn2+) crystals.
Free ion SO24ꢁ
Free ion modes
Degrees of freedom
Site symmetry
Factor group
Vibrational modes
Td
Cl
Ci
m1
m2
m3
m4
2
2
2
2
A1
E
F2
F2
Ag(Ra)
Au(IR)
m1,
m1,
2
m2,
m2,
3
m3,
m3,
3
3
m4
m4
2
3
Table 8
DTA and TG data for the GlyꢀMSO4ꢀ5H2O (M = Mg2+, Co2+, Zn2+) compounds.
Compound
Phase transition
Data from DTA and TG
Tmax (K)
D
T
Dm, %
calc.
Exp.
GlyꢀZnSO4ꢀ5H2O
GlyꢀCoSO4ꢀ5H2O
GlyꢀMgSO4ꢀ5H2O
GlyꢀZnSO4ꢀ5H2O ? GlyꢀZnSO4 + 5H2O"
Step I ? ꢁ2H2O
348
383, 393
543
313–358
358–413
523–638
11.02
16.5
22.98
10
17.78
22.78
Step II ? ꢁ3H2O
GlyꢀZnSO4 ? Gly" + ZnSO4
GlyꢀCoSO4ꢀ5H2O ? GlyꢀCoSO4 + 5H2O"
Step I ? ꢁ2H2O
373
453
603
343–393
393–473
473–623
11.2
16.9
23.44
11.67
16.11
22.78
Step II ? ꢁ3H2O
GlyꢀCoSO4 ? Gly" + CoSO4
GlyꢀMgSO4ꢀ5H2O ? GlyꢀMgSO4 + 5H2O"
Step I ? ꢁ2H2O
363
453
623, 743
323–363
363–473
473–763
12.6
18.9
26.29
14.74
16.84
27.37
Step II ? ꢁ3H2O
GlyꢀMgSO4 ? Gly" + MgSO4
240
220
200
180
160
140
120
100
80
Table 9
Curie constant (C), paramagnetic Curie temperature
moment (
(
H
)
and effective magnetic
l
eff) of the GlyꢀMSO4ꢀ5H2O (M = Mn2+, Co2+, Ni2+) compounds.
GlyꢀMnSO4ꢀ5H2O
GlyꢀCoSO4ꢀ5H2O
GlyꢀNiSO4ꢀ5H2O
1.4
3.35
34, 35
Gly.NiSO4.5H2O
Gly.CoSO4.5H2O
Gly.MnSO4.5H2O
C/cm3 (K molꢁ1
)
2.97
4.87
3.14
5.01
leff/
l
B
H
(K)
94.43
ꢁ21.81
Curie–Weiss behavior in the sequence 1/
(S = 3) < 1/ Ni (S = 2) (Fig. 6).
The paramagnetic Curie temperatures calculated for the studied
complexes (Table 9) pointed to exchange interactions between
the metal ions. The negative paramagnetic Curie temperature
v Mn (S = 5) < 1/v Co
v
H
= ꢁ21.81 K for the compound GlyꢀCoSO4ꢀ5H2O suggests antiferro-
magnetic interactions between the Co2+ ions whereas the positive
Curie temperatures (
60
280 290 300 310 320 330 340 350 360 370
Temperature / K
H
= 34.35 K for GlyꢀNiSO4ꢀ5H2O and 94.43 K
for GlyꢀMnSO4ꢀ5H2O) correspond to ferromagnetic interactions
Fig. 6. Magnetic susceptibility of GlyꢀMSO4ꢀ5H2O (M = Mn2+, Co2+ and Ni2+) vs.
between the metal ions [50].
temperature.
The determined values of the effective magnetic moment of all
compounds (Table 9) suggest a high-spin state of the metal ions in
octahedral coordination ([M(H2O)6]2+ and trans-[M(H2O)4(O-
gly)2]2+).
The thermal behavior of the zinc compound after complete
dehydration significantly differs from that of the other two com-
pounds. Only in this case a stable anhydrous GlyꢀZnSO4 compound
is formed and a plateau is exhibited by the TG curve at 413–523 K
4. Conclusion
(see
DT in Table 8). Unstable anhydrous compounds are formed by
the other two compounds. Their decomposition as well as that of
the free glycine occurs at 473–623 K. In the case of the zinc com-
pound, GlyꢀZnSO4, simultaneous decomposition to anhydrous zinc
sulfate and glycine takes place within the range 523–633 K. After
subsequent heating up to about 773 K, the decomposition products
of glycine are oxidized.
Equilibrium and non-equilibrium crystallization of complex
compounds was found to occur in the systems Gly–MSO4–H2O
(M = Mg2+, Mn2+, Co2+, Ni2+ and Zn2+) under different conditions.
Both the coordination behavior of M2+ ions in the mixed aqueous
glycine-metal(II) sulfate solutions and the formation of stable com-
plexes are responsible for salt crystallization. In the case of equilib-
rium crystallization the only compound GlyꢀMSO4ꢀ5H2O (triclinic
crystal system, space group P ꢁ 1) was predicted and proven in
these systems along with the crystallization of MSO4ꢀxH2O (x = 6,
7). In the manganese system at 308 K (MnSO4ꢀH2O) the only com-
plex compound is GlyꢀMnSO4.
3.5. Magnetic behavior of the GlyꢀMSO4ꢀ5H2O compounds
The magnetic susceptibility measurements of the compounds
GlyꢀMSO4ꢀ5H2O (M = Mn2+
,
Co2+ and Ni2+
)
indicated their

S. Tepavitcharova et al. / Journal of Molecular Structure 1018 (2012) 113–121
121
Gos. Univ. Kirg. Resp. Pravlenie VChO im. D.I. Mendeleeva, University of
Kirgizia, Frunze, 1970, pp. 120 (in Russian).
Non-equilibrium crystallization of GlyꢀCoSO4ꢀ3H2O (monoclinic
crystal system, space group P21/c) was also observed in the cobalt
system. The reported existence of GlyꢀNiSO4ꢀmH2O (m = 3, 6) and
GlyꢀZnSO4ꢀ3H2O was explained by the occurrence of non-equilib-
rium crystallization.
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Acknowledgements
The study is a part of a long term Research Plan of the Ministry
of Education of the Czech Republic No MSM0021620857 and Czech
Science Foundation (Grant No. 203/09(0878). The Bulgarian team
acknowledges the financial support by the National Science Fund
of Bulgaria (National Centre for New Materials UNION, Contract
No DCVP-02/2/2009).
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