Thermal, spectral and magnetic properties of 3,5-dimethoxybenzoates of Co(II), Ni(II) and Cu(II)

Article abstract of DOI:10.1007/s10973-005-0904-2

The complexes of 3,5-dimethoxybenzoates of Co(II), Ni(II) and Cu(II) have been synthesized as hydrated polycrystalline solids and characterized by elemental analysis, IR, FIR and electronic spectroscopy, magnetic studies and X-ray diffraction measurements. They possess colours typical of the M(II) ions: Cu-blue, Ni-green, Co-pink. The carboxylate groups bind as monodentate or a symmetrical, bidentate chelating or bridging ligands. The thermal stabilities were determined in air. When heated they dehydrate to form anhydrous salts which are decomposed to the oxides of respective metals. The magnetic susceptibilities of the complexes were measured over the range 77-300 K and the magnetic moments were calculated. The results reveal the complexes of Ni(II) and Co(II) to be high-spin complexes and that of Cu(II) to form dimer.

Full text of DOI:10.1007/s10973-005-0904-2

Journal of Thermal Analysis and Calorimetry, Vol. 82 (2005) 365–371
THERMAL, SPECTRAL AND MAGNETIC PROPERTIES OF
3,5-DIMETHOXYBENZOATES OF Co(II), Ni(II) AND Cu(II)
WiesÓawa Ferenc*, Agnieszka Walków-Dziewulska and P. Sadowski
Faculty of Chemistry, Maria Curie-SkÓodowska University, 20-031 Lublin, Poland
The complexes of 3,5-dimethoxybenzoates of Co(II), Ni(II) and Cu(II) have been synthesized as hydrated polycrystalline solids and
characterized by elemental analysis, IR, FIR and electronic spectroscopy, magnetic studies and X-ray diffraction measurements.
They possess colours typical of the M(II) ions: Cu-blue, Ni-green, Co-pink. The carboxylate groups bind as monodentate or a sym-
metrical, bidentate chelating or bridging ligands. The thermal stabilities were determined in air. When heated they dehydrate to
form anhydrous salts which are decomposed to the oxides of respective metals. The magnetic susceptibilities of the complexes were
measured over the range 77–300 K and the magnetic moments were calculated. The results reveal the complexes of Ni(II) and
Co(II) to be high-spin complexes and that of Cu(II) to form dimer.
Keywords: 3,5-dimethoxybenzoates, electronic spectra, magnetic properties of Co(II), Ni(II) and Cu(II) 3,5-dimethoxybenzoates,
thermal stability
Introduction
because it gives information about the practical use of
the acid for the separation of the elements by extrac-
tion or ion-exchange chromatographic methods. Mag-
netic properties of analysed complexes were investi-
gated in order to study the kinds of the way of coordi-
nation of the central ions and the nature of the bond-
ing between central ions and ligands. If the magnetic
moment 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 complex, on the electron configuration and hence,
on the nature of the bonding between the metal and
the ligands. On the other hand, when the number of
unpaired electrons in the complexes is known, the
spin only moment can be calculated. The deviation of
the measured magnetic moment from the spin only
permits the drawing of conclusions on the symmetry
of the complex in certain cases. In coordination com-
pounds the number of unpaired electrons on the cen-
tral atom is determined by its oxidation state on the
ligand-field strength. The determination of the num-
ber of unpaired electrons on the central atom estab-
lishes whether the compound investigated is of low or
high spin complex and whether the ligand field is
strong or weak.
According to literature survey the compounds of vari-
ous metal ions with different carboxylic acid anions
have been scarcely studied. However, for instance,
there are papers on the complexes of rare earth ele-
ments with 2,4-, 3,4-dimethoxy-, 4-chloro-2-nitro-
and 4-chloro-3-nitrobenzoic acid anions [1–6].
The compounds of 3,5-dimethoxybenzoic acid
anion with various cations are rather little known. Pa-
pers exist on its complexes with the following cations
as: Cu(II), Ag(I), Zn(II) and Pb(II). The complexes
were obtained as solids or were investigated in solu-
tion [7, 8]. The 3,5-dimethoxybenzoate of Cu(II) was
isolated in the solid-state and its thermal stability was
studied [7] while those of Ag(I), Zn(II) and Pb(II)
were only investigated in solution [8].
There are also informations about the solid-state
properties of complexes of 3,5-dimethoxybenzoates
of rare earth elements [9] but no about those of
3,5-dimethoxybenzoates of Co(II), Ni(II) and Cu(II).
Therefore it was decided to synthesize them as solids
and to examine some of their properties such as ther-
mal stability in air and nitrogen, solubility in water at
room temperature, IR spectral characteristic and crys-
talline form in order to determine whether they are
crystalline or amorphous compounds. Their magnetic
properties were also studied in the range 77–300 K.
The thermal stability investigations enabled the eval-
uation of the mechanism of the complex decomposi-
tion. The determination of the solubility is valuable
Experimental
The complexes of 3,5-dimethoxybenzoates of Co(II),
Ni(II) and Cu(II) were prepared by the addition of
*
Author for correspondence: wetafer@hermes.umcs.lublin.pl
1388–6150/$20.00
Akadémiai Kiadó, Budapest, Hungary
Springer, Dordrecht, The Netherlands
© 2005 Akadémiai Kiadó, Budapest

FERENC et al.
equivalent quantities of 0.1 M ammonium 3,5-di-
correction of diamagnetism of the constituent atoms
was calculated by using Pascal’s constants [11]. The
magnetism of the samples was found to be field inde-
pendent. Their magnetic moments, µeff, were calcu-
lated and presented in Table 4.
methoxybenzoate (pH≈5) to a 0.1 M hot aqueous solu-
tion containing the nitrates of these ion metals and
crystallizing at 293 K. The solids were filtered off,
washed with hot water and methanol to remove ammo-
nium ions and dried at 303 K to a constant mass. The
contents of carbon and hydrogen in the complexes
were determined by elemental analysis using a
CHN 2400 Perkin-Elmer analyser. The contents of
M
2+ metal ions were established by ASA method with
the use of ASA 880 spectrophotometer (Table 1).
The IR and FIR spectra of complexes were re-
corded over the ranges 4000–400 and 600–100 cm–1,
respectively, using a FTIR 1725X Perkin-Elmer spec-
trometer and a Nicolet MAGNA FIR 760 spectrome-
ter. The samples for the FTIR spectra measurements
were prepared as KBr discs and those for the FIR
spectra with polyethylene of masses from 0.8 to
1.0 mg. Some of the results are presented in Table 2.
The X-ray diffraction patterns were taken on a
HZG-4 (Carl Zeiss-Jena) diffractometer using Ni fil-
tered CuKα radiation. The measurements were made
within the range 2θ=4–80° by means of the Debye–
Scherrer–Hull method. The relationships between I/I0
and 2θ for these complexes are presented in Fig. 1.
The thermal stability and decomposition of the
complexes were determined by Paulik–Paulik–Erdey
Q-1500 D derivatograph with Derill converter, re-
cording TG, DTG and DTA curves (Figs 2–4). The
measurements were made at a heating rate of
10 K min–1 with a full scale. The samples (100 mg)
were heated in platinum crucibles in static air to
1173 K with a sensitivity of TG–100 mg. DTG and
DTA sensitivities were regulated by a Derill com-
puter program. The products of decomposition were
calculated from TG curves and verified by the diffrac-
tion pattern registration. The results are presented in
Table 3. The nature of the solid products of decompo-
sition was established from the TG curves and con-
firmed by IR and X-ray spectra.
Magnetic susceptibilities of polycrystalline sam-
ples of 3,5-dimethoxybenzoates of Co(II), Ni(II) and
Cu(II) were measured by the Gouy method using a
sensitive Cahn RM-2 balance. Measurements were
carried out at a magnetic field strength of 9.9 KOe.
Hg[Co(SCN)4] with the magnetic susceptibility [10]
of 1.644⋅10–5 cm3 g–1 was employed as calibrant. The
Fig. 1 Relationships between I/I0 and 2θ for Co(II), Ni(II) and
Cu(II) 3,5-dimethoxybenzoates
Table 1 Elemental analysis of 3,5-dimethoxybenzoates of Co(II), Ni(II) and Cu(II)
C/%
H/%
M/%
Complex L=C9H9O–4
Solubility/mol dm–3
calcd.
found
calcd.
found
calcd.
found
CoL2⋅2H2O
NiL2⋅3H2O
CuL2⋅2H2O
47.27
45.50
46.75
46.73
44.86
47.45
4.81
5.05
4.95
4.60
4.66
4.43
12.89
12.36
14.85
12.59
12.18
14.63
1.5⋅10–3
5.4⋅10–4
2.5⋅10–5
L=C6H3(OCH3)2COO–
366
J. Therm. Anal. Cal., 82, 2005

3,5-DIMETHOXYBENZOATES OF Co(II), Ni(II) AND Cu(II)
Table 2 Frequencies of the absorption bands of COO– vibrations for 3,5-dimethoxybenzoates of Co(II), Ni(II), Cu(II) and so-
dium and that of C=O for non-coordinated 3,5-dimethoxybenzoic acid (cm–1)
Complex L=C9H9O–4
CoL2⋅2H2O
ν(C=O)
νas(COO–)
νs(COO–)
∆ν(COO–)
ν(M–O)
1598
1401
1428
197
170
208
–
1582
1581
1392
1426
190
156
409
228
NiL2⋅3H2O
CuL2⋅2H2O
–
–
1392
1428
189
153
496
278
HL
1684
–
–
–
–
–
–
NaL
1580
1385
195
Table 3 Data of thermal decomposition processes for 3,5-dimethoxybenzoates of Co(II), Ni(II) and Cu(II) in air atmosphere
Mass loss/%
Complex L=C9H9O–4
∆T/K
Product of decomposition in solid-state
calcd.
found
CoL2⋅2H2O
CoL2
376–468
546–924
942–973
1161–1221
334–440
578–835
859–921
325–442
521–848
7.88
87.10
82.43
83.60
11.37
87.78
84.40
7.79
8.0
87.0
82.6
84.1
11.0
85.1
83.6
7.0
CoL2
Co
Co
Co3O4
CoO
NiL2
Ni
Co3O4
NiL2⋅3H2O
NiL2
Ni
NiO
CuL2
CuO
CuL2⋅2H2O
CuL2
74.90
74.2
∆T – temperature range of decomposition processes
The electronic spectra of the complexes of Co(II),
Ni(II) and Cu(II) and their chlorates(VII) used as stan-
dards were recorded using UV-VIS Specord spectrom-
eter. The chlorates(VII) of these elements were used as
standards because they practically do not form com-
plexes. Measurements were made in the diluted
(ca. 0.1 M) aqueous solutions of chlorates(VII) and
3,5-dimethoxybenzoates of Co(II), Ni(II) and Cu(II).
The obtained data are presented in Table 5.
Results and discussion
The complexes of 3,5-dimethoxybenzoates of Co(II),
Ni(II) and Cu(II) were obtained as polycrystalline
products with a metal ion to ligand ratio of 1:2 and the
general formula M(C9H9O4)2⋅nH2O, where M(II)=Co,
Ni, Cu and n=2 for Co(II) and Cu(II) and n=3 for
Ni(II). Their colours are those typical for the appro-
priate divalent ions (Cu-blue, Ni-green, Co-pink). In
these complexes the d→d electron transitions of the
central ions are those of the lowest energy and absorp-
tion occurs at relatively high wavelengths that de-
pends on the nature of the metal ion.
Fig. 2 TG, DTG and DTA curves for Co(II)
3,5-dimethoxybenzoate in air
The 3,5-dimethoxybenzoates of Co(II), Ni(II) and
Cu(II) exhibit similar solid-state IR spectra. The band
at 1684 cm–1 originating from the RCOOH group, pre-
sented in the spectrum of acid, is replaced in the spec-
tra of complexes by two bands at 1598–1581 and
The compounds were characterized by elemental
analysis (Table 1), FTIR and FIR spectra (Table 2).
J. Therm. Anal. Cal., 82, 2005
367

FERENC et al.
1428–1382 cm–1, which can be ascribed to the asym-
metric and symmetric vibrations of COO– group, re-
spectively [12–15]. The bands attributed to asymmetric
and symmetric C–H stretching modes of the CH3
groups are observed at 2968–2937 and
2840–2839 cm–1, respectively. The bands with the
maxima at 3606–3392 cm–1 in the spectra of 3,5-di-
methoxybenzoates of Co(II), Ni(II) and Cu(II) are
characteristic for ν(OH) vibration [13-15]. Addition-
ally, in the spectra of complexes there are bands at 900
and 700 cm–1 that may confirm the presence of mole-
cules of water of crystallization in the inner sphere of
coordination. The bands of ν(C–C) ring vibrations ap-
pear at 1455–1428, 1308–1288, 993–992 and
678–645 cm–1. The bands corresponding to metal
ion-oxygen stretching appear at 497, 228 and
208 cm–1. Table 2 presents the values of the two band
frequencies of asymmetrical and symmetrical vibra-
tions for carboxylate group of Co(II), Ni(II) and Cu(II)
3,5-dimethoxybenzoates. The separations of the
Fig. 3 TG, DTG and DTA curves of Ni(II)
3,5-dimethoxybenzoate in air
ν
and ν
modes of the complexes,
, are greater, smaller or the same than that of
)
as(OCO –
)
s(OCO –
)
∆ν
(OCO–
the sodium salt (∆ν
=195 cm–1). It indicates the
(OCO–
)
different participations of ionic bonds in the analysed
complexes compared to that of the sodium salt. For the
complexes the shifts of the frequencies of bands of
ν
and ν
are higher or practically the same
s(OCO –
)
as(OCO –
)
and higher, respectively, than those for sodium
3,5-dimethoxybenzoate. Accordingly taking into ac-
count the spectroscopic criteria [13, 15, 16] the
carboxylate ions appear to be bidentate, chelating and
bridging.
In order to estimate the crystalline forms of the
3,5-dimethoxybenzoates the X-ray powder diffrac-
tion measurements were done. The diffractogram
analysis suggests them to be polycrystalline com-
pounds with various degrees of crystallinity [17].
The thermal stability of Co(II), Ni(II) and Cu(II)
3,5-dimethoxybenzoates was studied in air (Table 3,
Figs 2–4). When heated to 1173 K the complex of
Co(II) is gradually decomposed to CoO with the inter-
mediate formations, at first, of CoL2, next Co and fi-
nally Co3O4. The Co is oxidized to Co3O4 (Fig 2). The
found mass loss is equal to 84.1 and calculated value
83.6 %. In the temperature range 1161–1221 K the
Co3O4 is reduced to CoO which is the final product of
decomposition. This process of reduction is con-
nected with the endoeffect while that of oxidation
with exothermic one. The decomposition process of
3,5-dimethoxybenzoate of Co(II) may be presented
by the following scheme:
Fig. 4 TG, DTG and DTA curves for Cu(II)
3,5-dimethoxybenzoate in air
The trihydrate of 3,5-dimethoxybenzoate of
Ni(II) dehydrates in one step in the range 334–440 K
losing three molecules of water and it forms the anhy-
drous complex. The mass loss calculated from TG
curve being equal to 11% corresponds to the loss of
three water molecules (theoretical value is 11.37%).
The anhydrous 3,5-dimethoxybenzoate of Ni(II) in the
temperature range 578–835 K is decomposed to form
Ni that next is oxidized (859–921 K) to NiO which is
the final product of thermal decomposition. The mass
losses calculated from TG curve are equal to 85.0%
which corresponds to the Ni formation (calculated
value is 87.78%) and to 83.6% (theoretical value is
84.40%) in the case of NiO formation. The dehydration
CoL2⋅2H2O→CoL2→Co→Co3O4→CoO
where L=C9H9O–4 .
368
J. Therm. Anal. Cal., 82, 2005

3,5-DIMETHOXYBENZOATES OF Co(II), Ni(II) AND Cu(II)
Table 4 Values of µeff for 3,5-dimethoxybenzoates of Co(II), Ni(II) and Cu(II)
CoL2⋅2H2O
χM⋅106
NiL2⋅3H2O
χM⋅106
CuL2⋅2H2O
χM⋅106
T/K
µeff/BM
T/K
µeff/BM
T/K
µeff/BM
77
101
104
109
113
119
123
128
133
138
143
148
153
158
163
173
183
193
203
214
221
227
236
245
251
260
271
281
297
30294
26273
25405
24308
23349
22480
21932
21430
20881
20104
19647
19328
19053
18505
18003
17089
15992
15306
14666
13936
13159
12794
12565
12337
11925
11651
11194
10966
10555
4.33
4.63
4.62
4.60
4.61
4.65
4.67
4.71
4.74
4.74
4.77
4.81
4.86
4.86
4.87
4.89
4.87
4.90
4.92
4.92
4.86
4.86
4.91
4.96
4.94
4.97
4.97
5.01
5.06
103
114
121
131
143
157
168
178
188
198
207
217
228
238
248
258
269
277
287
298
15000
13196
11772
11060
10063
9398
8591
7879
7357
6693
6313
6076
5981
5648
5506
5316
5126
1841
4746
4462
3.54
3.50
3.41
3.44
3.43
3.48
3.44
3.40
3.38
3.37
3.29
3.31
3.37
3.35
3.37
3.38
3.40
3.35
3.38
3.35
77
91
462
508
0.67
0.75
0.81
0.87
0.92
0.98
1.09
1.16
1.20
1.25
1.28
1.33
1.39
1.43
1.48
1.51
1.57
1.61
1.64
1.68
1.72
1.75
1.76
1.78
1.79
1.76
1.76
1.75
101
109
117
125
136
143
147
152
155
161
170
176
182
189
198
208
217
228
237
245
255
262
272
280
287
298
554
600
646
693
831
924
970
1016
1062
1108
1155
1201
1247
1247
1293
1293
1293
1339
1293
1247
1247
1247
1201
1108
1108
1016
L=C9H9O–4
and reduction processes are connected with an endo-
thermic effects seen in DTA curve while the combus-
tion of the organic ligand and the oxidation of Ni to
NiO with the exothermic ones (Fig. 3). The decompo-
sition process of 3,5-dimethoxybenzoate of Ni(II) may
proceed in the following way:
the TG curve. The molecules of crystallization water
in the analysed complexes may be in the inner coordi-
nation spheres of complexes. When heated the hy-
drated complexes form anhydrous compounds and
then in the central ion spheres the methoxy- or chang-
ing their dentates carboxylate groups may occur in or-
der to fill their inner coordination spheres.
NiL2⋅3H2O→NiL2→Ni→NiO
During heating to 1173 K the dihydrate of Cu(II)
3,5-dimethoxybenzoate dehydrates in one step
(Fig. 4). In the temperature range 325–442 K it losses
two water molecules and forms anhydrous complex.
The loss of mass calculated from TG curve is equal to
7.0% (the theoretical value is 7.79%). The anhydrous
complex in the range 521–848 K is decomposed to
CuO. The loss of mass calculated from TG curve is
where L=C9H9O–4 .
Considering the temperature at which the dehy-
dration process of the complex takes place and the
way by which it proceeds it is possible to assume that
the water molecules are also in the outer sphere of
complex coordination [18–21]. The peaks seen on the
DTG curve correspond to the loss of masses seen in
J. Therm. Anal. Cal., 82, 2005
369

FERENC et al.
Table 5 Values of the maximum of absorption bands for Co(II), Ni(II) and Cu(II) ions in the solution of chlorate(VII) samples
and 3,5-dimethoxybenzoates
Maximum of absorption bands of M 2+ ions in
Complex of
Range of measurements
1/λ⋅103/cm–1
∆1/λ⋅103/cm–1
the solutions of
3,5-dimethoxybenzoates
sample
19.57
chlorate(VII)
Co(II)
Ni(II)
Cu(II)
25–15
19.32
0.25
15.3–12.3
28–22
13.92
25.54
13.75
25.03
0.17
0.51
14.5–11.5
13.93
12.14
1.79
equal to 74.2% (theoretical value is 74.9%). The ther-
mal decomposition of 3,5-dimethoxybenzoate of
Cu(II) may proceed according to the scheme:
hedral triplet ground state with molecules of water
and probably with bidentate chelating or bridging
carboxylate groups coordinated to it. This was con-
firmed by the IR spectral analysis (Table 2). The
CuL2⋅2H2O→CuL2→CuO
ground state configuration of the nickel(II) ion in a
regular octahedral field is A2g (t26g e2 ) and it will be
3
where L=C9H9O–4 .
g
paramagnetic with two unpaired electrons. The con-
tribution to the magnetic susceptibility is given by a
spin-only term, second order spin-orbital coupling
and the temperature independent paramagnetism.
The electronic spectra of 3,5-dimethoxy-
benzoates of Co(II), Ni(II) and Cu(II) and their chlo-
rates(VII) as standards were recorded in the UV and
VIS ranges from 200 to 900 nm in order to observe
only the changes in the positions of the recorded ab-
sorption bands. The data obtained for the absorption
bands in the spectra recorded for these complexes and
the standards in the ranges 25000–15000 cm–1 for
Co(II), 14500–11500 cm–1 for Cu(II) and
28000–22000 and 15300–12300 cm–1 for Ni(II) are
presented in Table 5. The values of frequencies selec-
tively presented show the maxima of the bands of
3,5-dimethoxybenzoates of Co(II), Ni(II) and Cu(II)
and their standards. The absorption bands characteris-
tic for Co2+, Ni2+ and Cu2+ ions in the aqueous solu-
tions of 3,5-dimethoxybenzoates change to the
shorter waves yielding the hypsochromic shift which
depends on the character and stability of metal
ion-ligand bond to be connected with the kind of
ligand, hydration degree of central ions and with the
kind of solvents. It also depends on the character of
interaction between central ion and the group of at-
oms in its surroundings. The oxygen atoms of COO–
groups, of water molecules and of the –OCH3 sub-
stituents may variously influence the d orbitals of
central ions because the COO– ions and –OCH3
groups have different values of inductive and
mesomeric effects. Therefore the values of excitation
energy are changed causing the movements of ab-
sorption bands. With the rise of the complex stabili-
ties the maxima of absorption bands characteristic for
the vibrations caused by metal ions are moved to the
shorter waves of higher frequencies. When the com-
plex has the greater stability, the stronger bonding be-
The final products of decompositions of Co(II),
Ni(II) and Cu(II) 3,5-dimethoxybenzoates were iden-
tified roentgenographically.
The solubilities of 3,5-dimethoxybenzoates of
Co(II), Ni(II) and Cu(II) were measured (Table 1).
They are in the orders of 10–5–10–3 mol dm–3. The
Co(II) 3,5-dimethoxybenzoate is the most soluble salt
while that of Cu(II) the least soluble one.
The magnetic susceptibility of 3,5-di-
methoxybenzoates of Co(II), Ni(II) and Cu(II) was
measured over the range 77–300 K (Table 4). The val-
ues of the magnetic susceptibilities for the complexes
of Co(II) and Ni(II) obey the Curie–Weiss law while
those for Cu(II) 3,5-dimethoxybenzoate do not ac-
complish it because they increase with the rise of tem-
perature. At lower temperature range for dimers only
the lowest levels are occupied. That may be followed
on the example of the course of χCu=f (T) for the cop-
per(II) dimers, with states S=1 and S=0. Electron pop-
ulation in both levels is combined with the Boltzmann
contribution law and is temperature dependent. At the
higher temperatures and for the relatively high ex-
change parameters ⎢J ⎢(J<0) both states are occupied
(triplet state is dominating) and the magnetic moment
has the values close to the pure spin (1.73 BM) but
usually lower. With temperature lowering the popula-
tion of the triplet decreases and within the lowest tem-
perature ranges only the singlet state is occupied
(S=0) and µ=0 (BM).
In the case of 3,5-dimethoxybenzoates of Co(II)
and Ni(II) the values of magnetic moments are lower
than those close to the pure spins only [22]. These
values indicate that the complexes have the octahe-
dral symmetry.
The experimental data reveal that the magnetic
moments of 3,5-dimethoxybenzoate of Ni(II) are con-
nected with a spin-only moment. This indicates that in
the solid-state the nickel(II) cation exists in the octa-
370
J. Therm. Anal. Cal., 82, 2005

3,5-DIMETHOXYBENZOATES OF Co(II), Ni(II) AND Cu(II)
3 W. Ferenc and A. Walków-Dziewulska, J. Therm. Anal. Cal.,
tween central ion and ligand bonding is. The observed
63 (2001) 309.
hypsochromic replacements of absorption bands in
the electronic spectra, in the comparison with their
positions in the corresponding spectra of standards,
are indicative of the greater stability of central
ion-ligand bonding in the analysed complexes. On the
basis of this displacement it is not possible to deter-
mine the covalency of bonding because this replace-
ment depends on the coordination number of central
ion, its ion radius and oxidation degree. From the ob-
tained results it follows that the values of movements
of absorption bands of Co(II), Ni(II) and Cu(II) are
changed with the increase of atomic number of ele-
ment, similarly as the values of stability constants of
these elements in the Irving–Williams sequence [23].
The smallest value of change of absorption band
was observed for 3,5-dimethoxybenzoate of Ni(II) in
the range 15300–12300 cm–1. It is indicative of the
small stability of metal ion-ligand bonding in the solu-
tion and of its strong hydration degree. The composi-
tion of coordination sphere for central ion is similar to
that of high-spin aquation for those elements for which
it is equal to 6 and with octahedral coordination.
4 W. Ferenc and A. Walków-Dziewulska, J. Therm. Anal. Cal.,
70 (2002) 949.
5 W. Ferenc and A. Walków-Dziewulska, J. Therm. Anal. Cal.,
71 (2003) 375.
6 W. Ferenc and A. Walków-Dziewulska, J. Therm. Anal. Cal.,
74 (2003) 511.
7 S. Erre, L. Micera and G. Cariati, Polyhedron, 6 (1987) 1869.
8 Beilsteins Handbuch der Organischen Chemie, Bd. X,
Springer Verlag, Berlin 1932.
9 W. Ferenc, A. Walków-Dziewulska and J. Chruíciel,
J. Serb. Chem. Soc., 68 (2003) 751.
10 B. N. Figgs and R. S. Nyholm, J. Chem. Soc., (1958) 4190.
11 E. König, Magnetic Properties of Coordination and Organo-
metallic Transition Metal Compounds, Berlin 1966.
12 L. Bellamy, The Infrared Spectra of Complex Molecules,
Chapman and Hull, London 1975.
13 K. Nakamoto, Infrared and Raman Spectra of Inorganic
and Coordination Compounds, Wiley, Toronto 1997.
14 A. Cross and A. R. Jones, An Introduction to Practical
Infrared Spectroscopy, Butterworths, London 1969.
15 R. C. Mehrotra and R. Bohra, Metal Carboxylates,
Academic Press, London 1983.
16 B. S. Manhas and A. K. Trikha, J. Indian Chem. Soc.,
59 (1982) 315.
The colours of 3,5-dimethoxybenzoates of Co(II),
Ni(II) and Cu(II) are typical for M2+ of those element
ions (pink for Co2+, green for Ni2+ and blue for Cu2+). It
is indicative of the coordination of these element ions
with the oxygen atoms and the octahedral coordination
with the high spin character of the complex.
17 E. ˜·giewka and Z. Bojarski, Roentgenostructural
Analysis, PWN, Warsaw 1988.
18 A. V. Nikolaev, V. A. Logvinenko and L. J. Myachina,
Thermal Analysis, Vol. 2, Academic Press, New York 1989.
19 B. Singh, B. V. Agarwala, P. L. Mourya and A. K. Dey,
J. Indian Chem. Soc., 59 (1992) 1130.
20 F. Paulik, Special Trends in Thermal Analysis, Wiley,
Chichester 1995.
21 K. Burger, Coordination Chemistry; Experimental Methods,
Akadémiai Kiadó, Budapest 1973.
Acknowledgements
22 J. MroziÕski, Mater. Sci., Vol. XIV (1988) 3.
23 A. Bartecki, Electronic Spectroscopy of Inorganic and
Complex Compounds, PWN, Warsaw 1971.
This work is financially supported by grant (N 4T09A 157 22)
from the Polish Committee of Scientific Research.
Received: February 19, 2005
In revised form: July 15, 2005
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