Thermal, spectral and magnetic behaviour of 2,3,4-trimethoxybenzoates of Mn(II), Co(II), Ni(II) and Cu(II)

Article abstract of DOI:10.1007/s10973-005-6854-x

Four new complexes of 2,3,4-trimethoxybenzoic acid anion with manganese(II), cobalt(II), nickel(II) and copper(II) cations were synthesized, analysed and characterized by standard chemical and physical methods. 2,3,4-Trimethoxybenzoates of Mn(II), Co(II), Ni(II) and Cu(II) are polycrystalline compounds with colours typical for M(II) ions. The carboxylate group in the anhydrous complexes of Mn(II), Co(II) and Ni(II) is monodentate and in that of Cu(II) monohydrate is bidentate bridging one. The anhydrous complexes of Mn(II), Co(II) and Ni(II) heated in air to 1273 K are stable up to 505-517 K. Next in the range of 505-1205 K they decompose to the following oxides: Mn₃O₄, CoO, NiO. The complex of Cu(II) is stable up to 390 K, and next in the range of 390-443 K it loses one molecule of water. The final product of its decomposition is CuO. The solubility in water at 293 K is of the order of 10^-3 mol dm^-3 for the Mn(II) complex and 10^-4 mol dm^-3 for Co(II), Ni(II) and Cu(II) complexes. The magnetic moment values of Mn²⁺, Co²⁺, Ni²⁺ and Cu²⁺ ions in 2,3,4-trimethoxybenzoates experimentally determined in the range of 77-300 K change from 5.64-6.57 μ_B (for Mn ²⁺), 4.73-5.17 μ_B (for Co²⁺), 3.26-3.35 μ_B (for Ni²⁺) and 0.27-1.42 μ_B (for Cu²⁺). 2,3,4-Trimethoxybenzoates of Mn(II), Co(II) and Ni(II) follow the Curie-Weiss law, whereas that of Cu(II) forms a dimer.

Full text of DOI:10.1007/s10973-005-6854-x

Journal of Thermal Analysis and Calorimetry, Vol. 84 (2006) 2, 377–383
THERMAL, SPECTRAL AND MAGNETIC BEHAVIOUR OF
2,3,4-TRIMETHOXYBENZOATES OF Mn(II), Co(II), Ni(II) AND Cu(II)
WiesÓawa Ferenc1*, Beata Bocian1 and J. SarzyÕski2
1Faculty of Chemistry, Maria Curie-SkÓodowska University, 20-031 Lublin, Poland
2Institute of Physics, Maria Curie-SkÓodowska University, 20-031 Lublin, Poland
Four new complexes of 2,3,4-trimethoxybenzoic acid anion with manganese(II), cobalt(II), nickel(II) and copper(II) cations were
synthesized, analysed and characterized by standard chemical and physical methods. 2,3,4-Trimethoxybenzoates of Mn(II), Co(II),
Ni(II) and Cu(II) are polycrystalline compounds with colours typical for M(II) ions. The carboxylate group in the anhydrous com-
plexes of Mn(II), Co(II) and Ni(II) is monodentate and in that of Cu(II) monohydrate is bidentate bridging one. The anhydrous com-
plexes of Mn(II), Co(II) and Ni(II) heated in air to 1273 K are stable up to 505–517 K. Next in the range of 505–1205 K they decom-
pose to the following oxides: Mn3O4, CoO, NiO. The complex of Cu(II) is stable up to 390 K, and next in the range of 390–443 K it
loses one molecule of water. The final product of its decomposition is CuO. The solubility in water at 293 K is of the order of
10–3 mol dm–3 for the Mn(II) complex and 10–4 mol dm–3 for Co(II), Ni(II) and Cu(II) complexes. The magnetic moment values of
Mn2+, Co2+, Ni2+ and Cu2+ ions in 2,3,4-trimethoxybenzoates experimentally determined in the range of 77–300 K change from
5.64–6.57 mB (for Mn2+), 4.73–5.17 mB (for Co2+), 3.26–3.35 mB (for Ni2+) and 0.27–1.42 mB (for Cu2+). 2,3,4-Trimethoxybenzoates
of Mn(II), Co(II) and Ni(II) follow the Curie–Weiss law, whereas that of Cu(II) forms a dimer.
Keywords: complexes of Mn(II), Co(II), Ni(II), Cu(II), IR spectra, magnetic moments, thermal stability, 2,3,4-trimethoxybenzoates
Introduction
tween central ions and ligands. If the effective magnetic
moment meff is known, the number of unpaired electrons
can be calculated. This may also give information on the
oxidation state of the metal ion or the central atom of a
complex, on the electron configuration and, hence, on
the nature of the bonding between the metal and the lig-
ands. On the other hand, when the number of unpaired
electrons in the complexes is known, the spin-only mo-
ment can be calculated. The deviation of the measured
magnetic moment from the spin-only permits the draw-
ing of conclusions on the symmetry of the complex in
certain cases. In coordination compounds the number of
unpaired electrons of the central atom is determined by
its oxidation state on the ligand-field strength. The de-
termination of the number of unpaired electrons of the
central atom allows establishing whether the complex
investigated is of low or high spin and whether the
ligand field is strong or weak.
2,3,4-Trimethoxybenzoic acid having formula
(CH3O)3C6H2CO2H is a white crystalline solid, spar-
ingly soluble in cold water. Its solubility in water in-
creases with the rise of temperature [1]. Recently, we
have synthesized 2,3,4-trimethoxybenzoates of lantha-
nides(III) and yttrium(III) and investigated some of
their physico-chemical properties [2–10]. In order to
study more intensely the properties of 2,3,4-tri-
methoxybenzoates of trivalent and divalent metal ions,
as a continuation of our earlier work, four new com-
plexes of general formula M(C10H11O5)2×nH2O (where
M=Mn, Co, Ni and Cu and n=1 for Cu(II)) have been
prepared and examined.
Physico-chemical properties of these new coordi-
nation compounds were characterized by thermal stabil-
ity in air during heating to 1273 K, IR spectral data,
X-ray powder investigations, solubility in water at room
temperature and magnetic properties. Thermal stability
investigations give information about the mechanism of Experimental
complex decomposition and the endo- or exo-effects
Sample preparation
connected with such processes as: dehydration, melting,
polymorphic changes, crystallization, oxidation or re-
The complexes of the 2,3,4-trimethoxybenzoic acid
duction. The magnetic properties of obtained complexes
of Mn(II), Co(II), Ni(II) and Cu(II) were investigated in
the range of 77–300 K in order to study the kind of coor-
dination of central ions and the nature of bonding be-
anion with cations of Mn(II), Co(II), Ni(II) and Cu(II)
were obtained by the addition of equivalent quantities
of 0.1 M ammonium 2,3,4-trimethoxybenzoate (pH»5)
*
Author for correspendence: wetafer@hermes.umcs.lublin.pl
1388–6150/$20.00
Akadémiai Kiadó, Budapest, Hungary
Springer, Dordrecht, The Netherlands
© 2006 Akadémiai Kiadó, Budapest

FERENC et al.
to a hot solution containing the nitrates(V) of these
was calculated by the use of Pascal’s constants
[11, 12]. Magnetic moments were calculated accord-
ing to Eqs (1) and (2).
metal ions and crystallizing at 293 K. The solids were
filtered off, washed with hot water and ethanol to re-
move ammonium ions and dried at 303 K.
µeff=2.83(cM T)1/2
(1)
(2)
Analytical techniques used
µeff=2.83[cM (T–q)]1/2
where q is the Weiss constant.
The C, H analysis was performed using a CHN
2400 Perkin-Elmer analyser.
The IR spectra of complexes were recorded over
the range 4000–400 cm–1 using M-80 spectrophoto-
meter (Carl-Zeiss, Jena). Samples for IR spectra mea-
surements were prepared as KBr discs.
The X-ray powder diffraction were taken on a
HZG-4 (Carl Zeiss-Jena) diffractometer using Ni fil-
tered CuKa radiation. The measurements were made
within the range 2q=4–80° by means the
Debye–Scherrer–Hull method.
Solubility of Mn(II), Co(II), Ni(II) and Cu(II)
complexes in water was measured at 293 K. Saturated
solutions of the obtained compounds were prepared
under isothermal conditions. The contents of Mn(II),
Co(II), Ni(II) and Cu(II) were determined by using
ASA 880 spectrophotometer (Varian).
Results and discussion
2,3,4-Trimethoxybenzoates of manganese(II), co-
balt(II), nickel(II) and copper(II) were obtained as
polycrystalline solids with a metal ion to ligand ratio
of 1:2 (Table 1) and a general formula M(C10H11O5)2
×nH2O (where M=Mn, Co, Ni, Cu and n=1 for Cu)
Their colours are typical for the corresponding diva-
lent ions (Mn(II)-slightly pink, Co(II)-pink, Ni(II)-
green, Cu(II)-blue).
Some of the results of IR spectra analysis are pre-
sented in Table 2. The infrared spectrum of 2,3,4-tri-
methoxybenzoic acid shows the following absorption
bands: a strong band of COOH at 1680 cm–1, the bands
assigned to asymmetric and symmetric vibrations of the
OCH3 groups occurring at 2944 and 2840 cm–1, respec-
tively. The bands of ring vibrations appear at 1592,
The thermal stability and decomposition of the
complexes were studied in air using a Setsys 16/18 TG,
DTA instrument. The experiments were carried out un-
der air flow in the temperature range of 297–1273 K.
Samples ranging between 6.76 and 8.44 mg were
heated in Al2O3 crucibles.
Magnetic susceptibilities of polycrystalline sam-
ples of 2,3,4-trimethoxybenzoates of Mn(II), Co(II),
Ni(II) and Cu(II) were investigated in the temperature
range of 76–303 K. The measurements were carried
out using the Gouy method. Mass changes were ob-
tained from Cahn RM-2 electrobalance. The calibrant
employed was Co[Hg(SCN)4] for which the magnetic
susceptibility was assumed to be 1.644×10–5 cm–3 g–1.
Correction for diamagnetism of the constituent atoms
Table 1 Elemental analysis data of Mn(II)-, Co(II)-, Ni(II)- and Cu(II)-2,3,4-trimethoxybenzoates
H/%
C/%
M/%
Complex L=C10H11O5–
calcd.
found
calcd.
found
calcd.
found
MnL2
4.61
4.57
4.57
4.76
4.62
4.56
4.57
4.78
50.28
49.86
49.89
47.63
50.32
49.69
49.50
47.77
11.50
12.24
12.20
12.62
14.34
13.47
12.28
12.78
CoL2
NiL2
CuL2×H2O
Table 2 Wavenumbers (cm–1) of COO– bands in 2,3,4-trimethoxybenzoates of Mn(II), Co(II), Ni(II), Cu(II), in sodium salt of
ligand and the COOH band in 2,3,4-trimethoxybenzoic acid
Complex L=C10H11O5–
n(C=O)
n
n
Dn
COO –
as(COO–
)
s(COO –
1380
1370
)
MnL2
CoL2
–
1620
240
–
–
1628
1620
258
250
NiL2
–
–
1628
1560
–
1370
1400
–
258
160
–
CuL2×H2O
HL
1680
–
NaL
1610
1390
220
378
J. Therm. Anal. Cal., 84, 2006

THERMAL, SPECTRAL AND MAGNETIC BEHAVIOUR OF 2,3,4-TRIMETHOXYBENZOATES
1500–1420, 1176 and 1020 cm–1 and the bands of C–H
deformation vibrations, d(C–H), are observed in the re-
gion 1144–1100 cm–1. The –C–O–C– symmetric vibra-
tion bands, ns(COC), occur at 1020–1035 cm–1. The
bands observed at 940–650 cm–1 are associated with
out-of-plane deformation ring vibrations, j(CC), and
the C–H wagging vibrations, g(C–H). The bands at
830–800 cm–1 have been assigned to the g(C–H) vibra-
tions (in 1,2,3,4 substituted ring) [2–4, 13–25].
crystalline or amorphous compounds, their X-ray
powder diffraction measurements were carried out.
The analysis of the diffractograms suggests that the
obtained complexes are polycrystalline compounds
(Fig. 1). The structures of the compounds of Mn(II),
Co(II), Ni(II) and Cu(II) have not been determined,
because single crystals have not been obtained.
In order to verify the compositions of the com-
plexes, to determine the temperature ranges of their
thermal stability and decomposition during heating in
air, to estimate the intermediate and final products of
their decomposition and to evaluate the type of pro-
cesses that occur during heating, the thermal stability
of 2,3,4-trimethoxybenzoates of Mn(II), Co(II), Ni(II)
In the IR spectra of 2,3,4-trimethoxybenzoates of
Mn(II), Co(II), Ni(II) and Cu(II) the band at 1680 cm–1
disappears, which indicates that COOH group is not
present in the analysed complexes. In their spectra there
are two bands arising from asymmetric and symmetric
vibrations of the COO– group occurring at 1628–1560
and 1400–1370 cm–1, respectively. The bands assigned
to asymmetric and symmetric vibrations of the OCH3
groups, nas(CH3) and ns(CH3), are observed at the
2944–2936 and 2840 cm–1, respectively. The bands of
n(C=C) ring vibrations appear at 1600, 1568,
1500–1404, 1290, 1100 cm–1. The symmetric vibration
of –C–O–C– group bands, ns(COC), occur at
1032–1028 cm–1. The bands observed at 940–650 cm–1
are associated to out-of-plane deformation ring vibra-
tion, j(CC), and out-of-plane C–H bond vibrations,
g(C–H). The bands at 800 cm–1 have been assigned to
the g(C–H) vibrations (in 1,2,3,4 substituted ring). The
weak band at 420 cm–1 results from n(M–O) stretching
vibration [2–4, 13–25]. Table 2 presents the maximum
at frequencies for absorption bands of asymmetric and
symmetric vibrations of the COO– group for 2,3,4-tri-
methoxybenzoates of manganese(II), cobalt(II),
nickel(II), copper(II) and sodium. The magnitudes of the
separation, Dn
, between the frequency values of
COO –
n
and n
in complexes of Mn(II), Co(II),
s(COO –
)
as(COO –
)
Ni(II) are higher (Dn
=258–240 cm–1) and in the
COO –
complex of Cu(II) are lower (Dn
=160 cm–1) than in
COO –
the sodium 2,3,4-trimethoxybenzoate (Dn
=
COO –
220 cm–1). For 2,3,4-trimethoxybenzoates of Mn(II),
Co(II) and Ni(II) the shifts of the frequencies of n
as(COO –
)
and n
are higher and lower, respectively, than
)
s(COO –
those for sodium 2,3,4-trimethoxybenzoate. Accord-
ingly, the carboxylate ion in the analysed coordination
compounds appears to be monodentate group. On the
other hand, for the Cu(II) complex the shifts of the fre-
quencies of n
and n
are lower and higher,
s(COO –
)
as(COO –
)
respectively, than those for the sodium salt. Therefore
the carboxylate ion in this compound appears to be a
bidentate, bridging group [25, 26].
In order to evaluate, if the 2,3,4-trimethoxy-
benzoates of Mn(II), Co(II), Ni(II) and Cu(II) are
Fig. 1 Relationships between I/I0 and 2q for 2,3,4- trimethoxy-
benzoates of Mn(II), Co(II), Ni(II) and Cu(II)
J. Therm. Anal. Cal., 84, 2006
379

FERENC et al.
corresponds to the loss of 1 molecule of crystalliza-
tion water (theoretical value is 3.6%). The dehydra-
tion process is connected with an endothermic effect
seen on DTA curve. In the temperature range of
443–813 K the anhydrous 2,3,4-trimethoxybenzoate
of Cu(II) is being further decomposed to CuO.
The obtained results indicate that the thermal de-
composition of 2,3,4-trimethoxybenzoates of Mn(II),
Co(II), Ni(II) and Cu(II) in air proceeds in the follow-
ing steps:
505–989 K
Mn(C10H11O5)2 ¾¾¾¾® Mn3O4
517–1168 K 1168–1205K
Co(C10H11O5)2 ¾¾¾¾® Co3O4 ¾¾¾¾® CoO
Fig. 2 TG and DTA curves of 2,3,4-trimethoxybenzoate of Co(II)
507–906K
Ni(C10H11O5)2 ¾¾¾¾® NiO
and Cu(II) was studied in the temperature range of
293–1273 K. Some results are presented in Table 3
and Fig. 2. The results reveal that the complexes of
Mn(II), Co(II) and Ni(II) are anhydrous compounds,
while that of Cu(II) is monohydrate. These results
were also confirmed by the elemental analysis
(Table 1) and the IR spectra. The anhydrous 2,3,4-tri-
methoxybenzoates of Mn(II), Co(II) and Ni(II) heated
in air to 1273 K are stable up to 505–517 K. Having
various stability, they decompose in the temperature
range of 505–1205 K. The mass losses calculated
from TG curves are equal to 80.1, 80.4 and 83.6%, re-
spectively (the theoretical values are 84.0, 84.4 and
83.4%). The differences between calculated and theo-
retical values result from the apparatus errors. The
combustion of the organic ligands is accompanied by
strong exo-effect which can be seen in the DTA
curve. 2,3,4-Trimethoxybenzoates of Mn(II) and
Ni(II) decompose directly to the oxides: Mn3O4 and
NiO, while the complex of Co(II) (Fig. 2) to CoO with
intermediate formation of Co3O4. The process of
Co3O4 reduction to CoO is connected with endo-ef-
fect to be seen in DTA curve [27–29]. The oxides of
respective metals are the final products of the com-
plex decompositions. The monohydrate of Cu(II)
2,3,4-trimethoxybenzoate is stable up to 390 K. Next,
in the temperature range of 390–443 K being dehy-
drated it forms an anhydrous compound. The mass
loss calculated from TG curve being equal to 3.5%
390–443K
Cu(C10H11O5)2×H2O ¾¾¾¾® Cu(C10H11O5)2
443–813K
¾¾¾¾® CuO
The solubility of 2,3,4-trimethoxybenzoates of Mn(II),
Co(II), Ni(II) and Cu(II) in water at 293 K was mea-
sured (Table 3). Its values amount to: 2.8×10–3 mol dm–3
(for Mn(II) complex), 7.2×10–4 mol dm–3 (for Co(II)
complex), 7.5×10–4 mol dm–3 (for Ni(II) complex) and
2.2×10–4 mol dm–3 (for Cu(II) complex). The manga-
nese(II) 2,3,4-trimethoxybenzoate is the most soluble
salt while that of copper(II) is the least soluble one.
The magnetic susceptibility of the 2,3,4-tri-
methoxybenzoates of Mn(II), Co(II), Ni(II) and Cu(II)
was measured in the temperature range of 76–300 K
(Table 4). The anhydrous 2,3,4-trimethoxybenzoates
of Mn(II), Co(II) and Ni(II) follow the Curie-Weiss
law, since the values of the magnetic susceptibility de-
crease with increasing temperature. The paramagnetic
dependences of magnetic susceptibility values of the
complexes as a function of temperatures are presented
in Table 4 and those only for Co(II) 2,3,4-trimethoxy-
benzoate in Fig. 3. The effective magnetic moment val-
ues experimentally determined for 2,3,4-trimethoxy-
benzoates of Mn(II) and Ni(II) change from 5.64 (at
76 K) to 6.57 mB (at 303 K) and from 3.26 to 3.35 mB
for those of two appropriate complexes, respectively.
The experimental data reveal that the magnetic mo-
Table 3 Decomposition data for 2,3,4-trimethoxybenzoates of Mn(II), Co(II), Ni(II) and Cu(II) in air atmosphere and their sol-
ubility in water at 293 K
Mass loss/%
Mass loss/%
Complex L=C10H11O5–
Solubility/mol dm–3
DT1/K
Tmax/K
DT2/K
n
calcd. found
calcd. found
MnL2
–
–
–
–
–
–
–
–
–
–
1
505–989
517–1205
507–906
443–813
84.0
84.4
83.4
84.2
80.9
80.4
83.6
84.0
2.8×10–3
7.2×10–4
7.5×10–4
2.2×10–4
CoL2
–
–
NiL2
–
–
–
CuL2×H2O
390–443
413
3.6
3.5
DT1 – temperature range of dehydration process; Tmax – temperature of the maximum of the endothermic effect in the DTA curve;
n – number of crystallization water molecules being lost in one endothermic step; DT2 – temperature range of complex decomposition
380
J. Therm. Anal. Cal., 84, 2006

THERMAL, SPECTRAL AND MAGNETIC BEHAVIOUR OF 2,3,4-TRIMETHOXYBENZOATES
ments of Ni2+ and Mn2+ ions in the complexes are con-
nected with spin-only moments. Their theoretical val-
ues at room temperature are equal to 5.92 mB for the
Mn2+ ion (d 5) and 2.83 mB for the Ni2+ ion (d 8), respec-
tively. In the case of 2,3,4-trimethoxybenzoate of
Co(II) the effective magnetic moments of cobalt ion
determined in the range of 76–300 K are equal to
4.73–5.17 mB (Table 4, Fig. 3). The magnetic moment
measured for the Co2+ ion is equal to 5.17 mB (at room
temperature). This value differs from that of the
spin-only moment which amounts to 3.88 mB. The rela-
tively large difference between measured and calcu-
lated values results from a spin-orbital coupling
[30, 31]. Figure 4 presents the c –M1 values with rising
temperature for Co(II) 2,3,4-trimethoxybenzoate. The
experimental data suggest that the Mn2+, Co2+ and Ni2+
ions in the analysed complexes are in the high-spin
state forming octahedral coordination and in weak
field of ligands. The magnetic susceptibility of Cu2+
ions in 2,3,4-trimethoxybenzoate complex (Table 4)
displays a minimum at 76 K (Fig. 5) and it increases
reaching maximum at room temperature. Such depend-
ence is a typical behaviour of copper dimers. The room
temperature magnetic moment per Cu (meff=1.42 mB) is
similar to those observed for other dinuclear Cu(II)
compounds [32–35] and is lower than the d 9 spin-only
magnetic moment, meff=1.73 mB. This observation is
consistent with antiferromagnetic exchange between
Fig. 3 Dependence of magnetic susceptibility values vs.
temperature for 2,3,4-trimethoxybenzoate of Co(II)
Table 4 Values of meff for 2,3,4-trimethoxybenzoates of Mn(II), Co(II), Ni(II) and Cu(II)
MnL2
CoL2
NiL2
CuL2×H2O
C=3.8×10–3/K cm3 g–1
q=55/K
C=4.4×10–3/K cm3 g–1
q=61/K
C=2.28×10–3/K cm3 g–1
q=75/K
C=4.74×10–3/K cm3 g–1
q= –18.9/K
T/K
ccMorr×106 meff (mB)
T/K
ccMorr×106 meff (mB)
T/K
ccMorr×106 meff (mB)
T/K
ccMorr×106 meff (mB)
76
123
133
143
153
163
173
183
193
203
213
223
233
243
253
263
273
283
293
303
52092
36109
33909
31062
29703
28279
27049
25367
25820
23879
23231
20967
20902
19802
19672
19478
18896
18442
17990
17602
5.64
5.98
6.02
5.98
6.05
6.09
6.14
6.12
6.34
6.25
6.32
6.14
6.27
6.23
6.34
6.43
6.45
6.49
6.53
6.57
76
123
133
143
153
163
173
183
193
203
213
223
233
243
253
263
273
283
293
303
36560
23919
22103
20664
19302
18091
17485
16577
15744
15593
14912
14155
13701
13057
12754
12300
11922
11619
11241
10862
4.73
4.87
4.87
4.89
4.98
4.88
4.95
4.95
4.96
5.06
5.07
5.06
5.09
5.07
5.12
5.12
5.14
5.17
5.17
5.17
77
122
132
143
153
164
173
183
193
199
208
221
237
247
256
263
273
283
303
17280
11360
10527
9517
9036
8289
7763
7324
7194
6754
6359
6052
5527
5263
5043
5000
4956
4824
4117
3.26
3.25
3.38
3.33
3.34
3.32
3.32
3.29
3.32
3.33
3.31
3.33
3.30
3.29
3.28
3.31
3.35
3.36
3.35
76
123
133
143
153
163
173
183
193
203
213
223
233
243
253
263
273
283
293
303
158
226
318
348
409
470
501
531
562
592
605
623
635
641
623
635
647
666
641
653
0.27
0.63
0.73
0.78
0.85
0.92
0.97
1.02
1.07
1.12
1.15
1.20
1.23
1.26
1.27
1.31
1.34
1.38
1.39
1.42
L=C10H11O–5
J. Therm. Anal. Cal., 84, 2006
381

FERENC et al.
Conclusions
On the basis of the obtained results it appears that
2,3,4-trimethoxybenzoates of Mn(II), Co(II), Ni(II)
are anhydrous compounds while that of Cu(II) is hy-
drate. The final products of their decomposition are
following oxides: Mn3O4, CoO, NiO and CuO, re-
spectively. The solubility of the coordination com-
pounds of Mn(II), Co(II), Ni(II) and Cu(II) is of the
order of 10–3–10–4 mol dm–3. The complexes of Mn2+,
Co2+ and Ni2+ with of 2,3,4-trimethoxybenzoate acid
anion obey the Curie–Weiss law, since the values of
their magnetic susceptibility decrease with rising tem-
perature. 2,3,4-Trimethoxybenzoate of copper(II)
whose effective magnetic moment value is equal to
1.42 mB (at the room temperature) forms a dimer.
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Received: January 25, 2005
Accepted: March 21, 2005
OnlineFirst: January 11, 2006
DOI: 10.1007/s10973-005-6854-x
J. Therm. Anal. Cal., 84, 2006
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