Spectroscopic (IR, Raman) and thermogravimetric studies of 3d-metal cinchomeronates and dinicotinates

Article abstract of DOI:10.1007/s10973-016-5818-7

In this work, the thermal and spectroscopic properties of 3d-metal (Co, Cu, Zn, Mn, Ni, Fe) and sodium salts with cinchomeronic acid (3,4-pyridinedicarboxylic acid) (3,4pda) and dinicotinic acid (3,5-pyridinedicarboxylic acid) (3,5pda) were studied. The I

Full text of DOI:10.1007/s10973-016-5818-7

J Therm Anal Calorim
DOI 10.1007/s10973-016-5818-7
Spectroscopic (IR, Raman) and thermogravimetric studies of
3d-metal cinchomeronates and dinicotinates
1
G. Swiderski M. Kalinowska1 I. Rusinek2
´
•
•
•
M. Samsonowicz1 Z. Rza˛czynska W. Lewandowski1
2
•
•
´
Received: 28 November 2015 / Accepted: 4 September 2016
Ó The Author(s) 2016. This article is published with open access at Springerlink.com
Abstract In this work, the thermal and spectroscopic
properties of 3d-metal (Co, Cu, Zn, Mn, Ni, Fe) and
sodium salts with cinchomeronic acid (3,4-pyridinedicar-
boxylic acid) (3,4pda) and dinicotinic acid (3,5-
pyridinedicarboxylic acid) (3,5pda) were studied. The IR
and Raman spectra were registered and analyzed in the
range of 400–4000 cm-1. The thermogravimetric study of
synthesized compounds was done. The degree of hydration
and the products of thermal decomposition were estimated.
Moreover, it was done the comparison between the effect
of 3d-transition metal cations and sodium cation on the
degree of perturbation or stabilization of the electronic
system of pyridine molecule depending on the position of
carboxylic group in the ring.
Introduction
Pyridinecarboxylic acids (picolinic, nicotinic and isonico-
tinic) are biologically important ligands incorporated into
some enzymes, and they are active agents in some drugs as
well [1–18]. In our previous work, we examined the effect
of different metals (alkali [19–21], alkaline earth [22], 3d-
metals [23]) on the electronic system of pyridinecarboxylic
acids. Research shows that alkali and heavy toxic metals
with low ionic potential disturb the aromatic system, while
the 3d-transition metals stabilize the aromatic system
pyridinecarboxylic acids.
This work is a continuation of our investigations on the
metals effect on the electronic structure of pyridinecar-
boxylic acid. The study of metal complexes with nicotinic
acid and cinchomeronic acid has shown that these com-
plexes can have different types of metal–ligand coordina-
tion [24–26]. Whitfield et al. [24] studied the complexes of
cobalt and nickel with 3,5-pyridinedicarboxylic acid. The
complex of cobalt (CoLÁ2H2O) is monodentate binding.
However, in the nickel complex (NiLÁH2O), there are two
types of bonds: monodentate and bidentate chelating.
Łyszczek and Mazur studied the structures and thermal
properties of lanthanide dinicotinates [25]. Studies have
shown that the lanthanides form the types of coordination,
such as monodentate, bidentate bridging and chelating
bidentate. In the structure of calcium dinicotinate, there are
two types of bonds—monodentate and bidentate chelating
Starosta et al. [26]. In the structure of manganese cin-
chomeronate, there are two types of bonds—monodentate
and bidentate bridging Tong et al. [27].
Keywords Nicotinic acid and derivatives Á Cinchomeronic
acid Á Dinicotinic acid Á Metal complexes Á Spectroscopy
(IR Raman)
Electronic supplementary material The online version of this
article (doi:10.1007/s10973-016-5818-7) contains supplementary
material, which is available to authorized users.
´
& G. Swiderski
swider30@gmail.com
& W. Lewandowski
w-lewando@wp.pl
1
The specific objectives of the present study (along with
the purpose of implementing the above-mentioned broader
theme) are to:
Department of Chemistry, Bialystok University of
Technology, Wiejska Street 45E, 15-351 Bialystok, Poland
2
Department of General and Coordination Chemistry, UMCS,
M.C. Sklodowska Sq. 2, 20-031 Lublin, Poland
123

´
G. Swiderski et al.
in the range of 400–4000 cm-1 with a MultiRam (Bruker)
spectrometer. Thermogravimetric analyses were conducted
on the Setsys 16/18 analyzer in dynamic air atmosphere.
Therefore, 6.0–8.0-mg samples were heated in the range of
30–800 °C in the ceramic crucibles using the heating rate
of 10 °C min-1. The TG, DTG and DSC curves were
registered. The elementary analysis was carried out using
the CHN 2400 PerkinElmer Analyzer. The water content
was determined from the thermogravimetric curves.
1. determine the composition studied complexes on the
basis of elemental analysis and thermogravimetric data
2. propose the structure of the compounds on the basis of
FT-IR and Raman spectral data
3. compare the change in electronic charge distribution as
a result of complex formation.
In the present work, the impact of 3d-metals on the
electron system of pyridinedicarboxylic acids (dinicotinic
and cinchomeronic acids) (Fig. 1) was examined and
thermal properties of metal complexes of these acids were
determined.
Results and discussion
Elemental analysis
Experimental
The composition of the synthesized complexes was deter-
mined by elemental analysis. The data are gathered in
Tables 1 and 2. All the complexes prepared in accordance
with the procedure presented in experimental section were
hydrated. It was confirmed by thermal analysis. Complexes
of manganese and zinc as well as sodium salts were white
similarly as the ligands from which they were synthesized.
Other complexes were colorful. The obtained complexes
were poorly soluble in water. Synthesis was carried out
several times to give a reaction yield of 60–80 %. The
reaction yields for the different complexes are given in
Tables 1 and 2.
Sample preparations
3,4-pyridinedicarboxylates (3,4-pdc) and 3,5-pyridinedi-
carboxylates (3,5-pdc) of 3-d metal ions were prepared in
water solution by adding disodium salts of each ligand to
appropriate amount of 3-d metal chlorides at 80 °C with
continuous stirring for 2 h (molar ratio of sodium salts of
ligands to the metal chlorides was 1:1 in case of divalent
metal ions and 1.5:1 in case of trivalent metal). The mix-
tures were left for 24 h at room temperature. The precipi-
tated solids were filtered off and washed with water to
eliminate chloride ions. Disodium salts were obtained as
microcrystals by adding the of sodium hydroxide solution
(0.1 M) to the stoichiometric amount of acid (molar ratio
of ligand to the sodium hydroxide: 1:2). Salts were slowly
evaporated at room temperature. After precipitation, the
salt microcrystals were filtered and washed with a small
amount of deionized water. Purity of the salts and com-
plexes was confirmed by elemental analysis and IR spectra
analysis. Substances were dried at 30 °C under atmo-
spheric pressure.
Thermogravimetric analysis
The complexes of 3,4-pyridinedicarboxylic and 3,5-
pyridinedicarboxylic acids with transition metal ions have
the general formula: M[(C5NH3(COO)2]ÁnH2O where
M = Mn, Co, Ni, Cu, Zn(II) ions, n = 1–3 and Fe2[(C5-
NH3(COO)2]3ÁnH2O where n = 4 or 6. The complexes of
both series are obtained as hydrated, crystalline well-de-
fined compounds. The simultaneous TG/DTG/DSC curves
in dynamic dry air atmosphere of all compounds are shown
in Figs. 2–9. The analytical and thermoanalytical data for
the synthesized compounds are given in Tables 1–4,
respectively (Figs. 2–9). These results indicate the stoi-
chiometry of two series of compounds, which are consis-
tent with their general formulae.
Methods
The FT-IR spectra were recorded with an Alfa (Bruker)
spectrometer within the range of 400–4000 cm-1. The
samples in the solid state were measured in KBr matrix
pellets. FT-Raman spectra of solid samples were recorded
Fig. 1 Structures of studied
ligands
COOH
COOH
COOH
HOOC
COOH
N
N
N
3-pyridinecarboxylic acid 3,4-pyridinedicarboxylic acid 3,5-pyridinedicarboxylic acid
nicotinic acid cinchomeronic acid dinicotinic acid
123

Spectroscopic (IR, Raman) and theffirmogravimetric studies of 3d-metal cinchomeronates and…
Table 1 Elemental analysis, analytical and physical data for 3,4-pyridinedicarboxylates
Compound
Color
Yield/%
Content C/%
Exp.
Content H/%
Content N/%
Content M/%
Calc.
Exp.
Calc.
Exp.
Calc.
Exp.
Calc.
Na2LÁH2O
MnLÁ H2O
Fe2L3Á6H2O
CoLÁ1.5H2O
NiLÁ3H2O
CuLÁH2O
White
White
Brown
Violet
Green
Blue
70–75
70
36.18
35.16
35.10
33.78
32.06
33.95
33.49
36.66
35.29
35.15
33.46
32.33
34.05
33.80
2.14
2.21
2.07
2.28
2.60
1.98
2.13
2.18
2.10
2.09
2.39
2.69
2.03
2.01
6.02
5.69
5.97
5.64
5.48
5.61
5.47
6.11
5.88
6.11
5.58
5.39
5.68
5.63
19.78
22.33
16.50
23.72
22.97
25.44
25.56
20.08
23.08
16.89
23.47
22.59
25.76
26.31
65–70
65–70
60–65
65–70
75–80
ZnLÁH2O
White
Table 2 Elemental analysis, analytical and physical data for 3,5-pyridinedicarboxylates
Compound
Color
Yield/%
Content C/%
Exp.
Content H/%
Content N/%
Content M/%
Calc.
Exp.
Calc.
Exp.
Calc.
Exp.
Calc.
Na2LÁH2O
MnLÁ2H2O
Fe2L3Á4H2O
CoLÁ2H2O
NiLÁ3H2O
CuLÁ0.5H2O
ZnLÁ1.5H2O
White
White
Brown
Pink
70–75
65–70
60–70
70–75
60–65
60–70
75–80
36.44
32.41
33.70
32.71
35.29
33.20
36.44
36.66
32.80
33.88
32.30
35.34
32.62
36.66
1.93
2.61
2.41
2.57
1.29
2.06
1.93
2.18
2.73
2.42
2.69
1.31
2.33
2.18
5.88
5.44
5.44
5.37
6.01
5.48
5.88
6.11
5.47
5.65
5.38
6.12
5.44
6.11
19.32
21.34
20.92
22.62
20.73
26.94
24.43
20.08
21.46
21.73
22.66
21.11
26.74
25.39
Green
Blue
White
(a)
(b)
0
0
DTG
DTG
40
30
20
10
0
40
30
–20
–40
–20
–40
20
10
0
–60
–60
DSC
TG
TG
DSC
373 473
573 673
773
873 973 1073
373 473
573 673
773
873 973 1073
Temperature/K
Temperature/K
Fig. 2 TG/DTG/DSC curves of Mn(3,4-pdc)ÁH2O (a) and Mn(3,5-pdc)(H2O)2 (b)
Generally, the complexes of both series decompose in a
similar way when heated in the two ground stages: the first
stage is dehydration of the complexes with formation of
more or less stable anhydrous compounds, and the second
stage is decomposition of anhydrous compounds connected
with oxidation of organic ligands and formation of metal
oxides as residues.
The first stage the endothermic processes of dehydration
occur for the majority of complexes in only one step at low
temperatures with the onset temperatures of water evapo-
ration of the hydrates in the range of 333–343 K. Their
value points to outer-sphere character of water molecules
in the structure of complexes. However, higher temperature
of dehydration at 423–503 K as it takes place in the case of
123

´
G. Swiderski et al.
Table 3 Thermoanalytical results (TG,DTG,DSC) for complexes of 3,4-pyridinedicarboxylates
Complex
Stage
TG
Trange/K
DTG(DSC)
Tmax. peaks/K
Peak nature/
kJ/mol H2O
Mass loss/%
Loss
Final
residue
Calc.
Found
Mn(3,4-pdc)ÁH2O
I
343–473
613–688
453 (448)
648 (673)
endo (39.3)
exo
8.75
8.05
H2O
MnO
II
70.21
69.38
CO2; CO; py
(pyridine rings,
fragmentsof aromatic
rings) [30]
Fe2(3,4-pdc)3Á(H2O)6
I
333–473
573–653
373 (373)
603 (633)
753 (753)
358 (359)
613 (643)
363 (373)
423 (433)
643 (673)
693 (693)
423 (348)
528 (533)
623 (623)
358 (353)
668 (643)
728 (733)
873 (873)
463 (468)
733 (743)
endo (22.7)
exo
15,10
74,80
15,60
77,60
H2O
Fe2O3
II
III
I
CO2; CO; py
CO
exo
Co(3,4-pdc)Á(H2O)1,5
333–473
563–653
343–398
398–453
603–733
endo (27.2)
exo
10.75
70.15
10.76
19.43
73.12
10.43
68.87
9.95
H2O
CoO
NiO
II
I
CO2; CO; py
1H2O
[Ni(3,4-pdc)(H2O)2]ÁH2O
endo (29,3)
endo
II
III
IV
I
20.77
73.35
2H2O
exo
CO2; CO; py
CO2; CO
H2O
exo
Cu(3,4-pdc)ÁH2O
Zn(3,4-pdc)ÁH2O
343–473
513–533
533–633
343–413
573–763
sł.endo (49,7)
exo
7.29
7.00
CuO
ZnO
II
III
I
*40
67.75
7.24
67.77
CO2
exo
CO2; CO; py
H2O
endo (78,5)
exo
7.08
II
III
IV
I
67.30
68.08
CO2; py
CO2; CO
CO2
exo
exo
Na2(3,4-pdc)ÁH2O
423–493
703–783
endo (34,4)
exo
7.85
–
8.69
–
H2O
Na2CO3
II
CO2; CO;py
(a)
(b)
0
0
DTA
DTG
30
20
10
0
30
–20
–40
–60
–20
–40
–60
20
10
0
DSC
TG
DSC
TG
373
473
573
673
773
873
973 1073
373
473
573
673
773
873
973 1073
Temperature/K
Temperature/K
Fig. 3 TG/DTG/DSC curves of Fe2(3,4-pdc)3(H2O)6 (a) and Fe2(3,5-pdc)3(H2O)4 (b)
Mn(3,5-pdc)(H2O)2 complex points to the inner-sphere
water molecules [28–30].
This fact as well as loss of mass allows to determine the
formula of the complex as [Co(3,5-pdc)(H2O)]Á(H2O)
which points to on one microcrystal- and one coordination
water molecule. Two stages of dehydration are more visi-
ble on the TG, DTG and DSC curves of Ni(II) complexes.
For Ni(3,4-pdc)(H2O)3 onsets of dehydration are at 343
and 398 K, for Ni(3,5-pdc)(H2O)3 at 343 and 493 K.
Dehydration at lower temperature (343 K) in both cases is
There are some complexes for which the dehydration is
of double-stage character as for Co(3,5-pdc)(H2O)2;
Ni(3,4-pdc)(H2O)3; and Ni(3,5-pdc)(H2O)3 (Figs. 4b, 5a,
b). For the Co(3,5-pdc)(H2O)2 complex, there are two onset
temperatures of dehydration at 343 and 403 K, two peaks
on the DTG and two endothermic peaks on DSC curves.
123

Spectroscopic (IR, Raman) and theffirmogravimetric studies of 3d-metal cinchomeronates and…
(a)
(b)
0
0
–20
–40
–60
DTG
DTG
30
20
10
0
30
20
10
0
–20
–40
–60
DSC
TG
DSC
TG
373
473
573
673
773
873
973 1073
373
473
573
673
773
873
973 1073
Temperature/K
Temperature/K
Fig. 4 TG/DTG/DSC curves of Co(3,4-pdc)(H2O)1,5 (a) and [Co(3,5-pdc)(H2O)]ÁH2O (b)
(a)
(b)
0
DTA
0
DTG
30
30
20
10
–20
–40
–60
–20
–40
–60
–80
20
10
0
DSC
TG
TG
0
DSC
373
473
573
673
773
873
973
1073
373
473
573
673
773
873
973
1073
Temperature/K
Temperature/K
Fig. 5 TG/DTG/DSC curves of [Ni(3,5-pdc)(H2O)2]ÁH2O (a) and [Ni(3,5-pdc)(H2O)]Á2H2O (b)
connected with a loss of outer-sphere water, but dehydra-
tion at higher temperatures (398 and 493 K) is connected
with a loss of coordination, inner-sphere water in the
complex structures. Similarly to the Co(II) complex, two
peaks on the DTG and DSC curves as well as calculated
and found loss of mass allow to determine the formulae of
complexes as [Ni(3,4-pdc)(H2O)2] (H2O) and [Ni(3,5-
pdc)(H2O)]Á2H2O.
for 3,4pda ligand about 50–90 K (Tables 3 and 4). It can be
due to more symmetric charge distribution in the complexes
with 3,5-pdca ligand.
The anhydrous compounds of Mn(II), Fe(III), Co(II) and
Ni(II) with 3,4pda and 3,4pda ligands above 600 K
decompose in one step which correspond to the sharp
exothermic peaks at about 700 K which can be also
attributed to oxidation of organic matter and the gaseous
products that evolve during thermal decomposition. In the
case of Ni(3,4-pdc) complex (Fig. 5A), the exothermic
peak splits into two. Processes of decomposition of anhy-
drous Cu(II) complexes of both ligands proceed in two
stages (Fig. 6a, b). In both cases, the first step is connected
with about 40 % mass loss and the second one leads to
CuO formation. The first step is attributed to small, but the
second to large exothermic effects. The large effect is
attributed to the oxidation of carbonaceous residue, formed
in the former step [31].
Analysis of the TG/DTG curves course indicates that after
dehydration the formed anhydrous complexes are not gen-
erally stable and the TG curves show a slight but systematic
loss in mass. The complex of Mn(II) is the most stable in the
series of complexes with 3,4pda ligand (Fig. 2a), while the
complexes of Mn(II) and Zn(II) are the most stable in the
series with 3,5-pda ligand (Figs. 2b and 7b). The complexes
of 3,5-pda ligand seem to be more stable, and the onset
temperatures for the decomposition of the anhydrous com-
pounds, except for Fe(III) and Cu(II), are higher than those
123

´
G. Swiderski et al.
Table 4 Thermoanalytical results (TG,DTG,DSC) for complexes of 3,5-pyridinedicarboxylates
Complex
Stage
TG
Trange/K
DTG(DSC)
Tmax. peaks/K
Peak nature/
kJ/mol H2O
Mass loss/%
Loss
Final
residue
Calc.
Found
Mn(3,5-pdc)Á(H2O)2
I
423–503
663–748
473(483)
703(728)
endo (50.0)
exo
14.06
71.84
15.07
70.81
H2O
MnO
II
CO2; CO; py
(pyridine rings,
fragmentsof aromatic
rings)[30]
Fe2(3,5-pdc)3Á(H2O)4
I
343–423
573–748
343–393
403–463
636–733
343–443
493–543
636–713
323–393
523–573
573–748
343–393
393–493
663–753
393–443
728–798
358(363)
643(653)
363(363)
433(433)
668(693)
423(430)
513(523)
673(713)
343(351)
563(563)
693(693)
368(353)
443(447)
738(743)
423(423)
773(793)
endo(33.2)
exo
10.60
76,48
6.92
10.10
74,85
7.00
H2O
Fe2O3
CoO
II
I
CO2; CO; py
H2O
[Co(3,5-pdc)(H2O)]ÁH2O
endo(32.5)
endo
II
III
I
12.50
70.18
12.94
19.42
73.14
3.79
12.31
70.69
13.00
19.10
73.47
4.02
H2O
exo
CO2; CO; py
2H2O
[Ni(3,5-pdc)(H2O)]Á2H2O
Cu(3,5-pdc)Á(H2O)0,5
Zn(3,5-pdc)Á(H2O)1,5
Na2(3,5-pdc)ÁH2O
endo(24.1)
endo
NiO
II
III
I
1H2O
exo
CO2; CO; py
H2O
endo(21.0)
exo
CuO
II
III
I
* 45
66.73
3.50
64.94
CO2
exo
CO2; CO; py
H2O
endo(18.6)
endo
3.30
ZnO
II
II
I
10.10
68.39
7.86
10.48
68.72
8.03
H2O
exo
CO2; CO; py
H2O
endo (38.8)
exo
Na2CO3
II
53.73
53.19
CO2; CO; py
(a)
(b)
0
DTG
0
DTG
30
20
10
30
20
10
–20
–40
–60
–20
–40
–60
DSC
TG
DSC
TG
0
0
373
473
573
673
773
873
973 1073
373
473
573
673
773
873
973
1073
Temperature/K
Temperature/K
Fig. 6 TG/DTG/DSC curves of Cu(3,4-pdc)ÁH2O (a) and Cu(3,5-pdc)(H2O)0,5 (b)
Thermal decomposition of both Zn(II) complexes pro-
ceeds in a different way. The Zn(3,4-pdc)ÁH2O complex at
573 K undergoes decomposition and oxidation with two
exothermic effects and next oxidation of carbonaceous
residue with the exothermic effect at 873 K. The Zn(3,5-
pdc)ÁH2O complex is more stable, and at the temperature
higher by about 100 K decomposition and oxidation take
place in one step without intermediates products. In all
complexes of both series, the total mass loss above 800 K
corresponds to formation of metal oxides (MO; Fe2O3) as
final residues.
Additionally the simultaneous TG/DTG/DSC curves in
dynamic dry air atmosphere of free 3,4-pyridinedicar-
boxylic and 3,5-pyridinedicarboxylic acids are presented in
Fig. 8a, b. In both cases, these curves show total mass loss
due to heating but in one step for 3,4- and in two steps for
3,5-pyridinedicarboxylic acid. The beginning of mass loss
for 3,4-pdc acid starts at 473 K, and the maximum of mass
123

Spectroscopic (IR, Raman) and theffirmogravimetric studies of 3d-metal cinchomeronates and…
(a)
(b)
0
–20
–40
–60
0
–20
–40
–60
DTG
DTG
30
10
20
10
5
DSC
0
DSC
TG
0
TG
373
473
573
673
773
873
973
1073
373
473
573
673
773
873
973
1073
Temperature/K
Temperature/K
Fig. 7 TG/DTG/DSC curves of Zn(3,4-pdc)ÁH2O (a) and Zn(3,5-pdc)(H2O)1,5 (b)
(a)
(b)
DTG
DSC
0
0
DTG
DSC
0
–40
–80
–40
–80
–4
–8
TG
TG
373
473
573
673
773
873
973
373
473
573
673
773
873
973
Temperature/K
Temperature/K
Fig. 8 TG/DTG/DSC curves of 3,4-pdc (a) and 3,5-pdc (b)
loss is observed at 558 K with the simultaneous large
endothermic effect with the maximum at 563 K. At 573 K
the process is over. The endothermic peak at 563 K on the
DSC curve is attributed to the melting of acid and partial
evaporation as well as decarboxylation and decomposition
[31, 32]. The 3,5pda is more stable, and the beginning of
mass loss is observed at 523 K with the maximum at 608 K
and the endothermic effect at 623 K. At 633 K the car-
bonaceous residue is formed and the exothermic peak at
753 K is attributed to its oxidation.
temperature mass (8.0/7.9 %) at 423–493 K corresponds to
the dehydration with a loss of one molecule of water
resulting in the endothermic peak. Anhydrous compound is
stable to about 693 K. In this range of temperatures, the
salts Na2(3,4-pdc)ÁH2O and Na2(3,5-pdc)ÁH2O exhibit the
same way of decomposition but the anhydrous salt
Na2(3,5-pdc) is a bit more stable (up to 723 K). Further
heating causes gradual decomposition and oxidation of
anhydrous salts but in different ways. The anhydrous salt
Na2(3,4-pdc) decomposes in two steps with the mass loss at
range of 733 K and about 873 K. The exothermic process
with three peaks at 760; 765; and 773 K is attributed to
oxidation of the organic matter and gaseous products
evolved during the thermal decomposition and oxidation.
In the case of Na2(3,5-pdc), the thermal decomposition
occurs at 773 K in one step. The total mass loss (53.73/
Disodium 3,4- and 3,5-pirydinedicarboxylates were
necessary as the models for spectroscopic examination of
complexes. They were obtained both as monohydrate
microcrystalline compounds, but their thermal properties
differ significantly. The thermal analysis of Na2(3,4-
pdc)ÁH2O exhibits three mass loss steps. The lower
123

´
G. Swiderski et al.
(a)
(b)
0
DSC
DTA
0
40
DTG
10
0
–20
–40
–20
–40
20
–10
TG
DSC
0
TG
373
473
573
673
773
873
973
373
473
573
673
773
873
973
1073
Temperature/K
Temperature/K
Fig. 9 TG/DTG/DSC curves of Na2(3,4-pdc)ÁH2O (a) and Na2(3,5-pdc)ÁH2O (b)
Table 5 Spectral parameters from the IR and Raman spectra of 3,4- and 3,5-pyridinedicarboxylates
Compound
mas (COO-)
msym (COO-)
Dm
bsym
bas
Db
Proposed type of coordination
(COO-) (COO-)
3,4-pyridinedicarboxylates
Na2LÁH2O
IR
Raman 1606 s, 1581 m
IR 1571 vs
Raman 1575 m
1602 vs, 1585 vs 1411 vs, 1381 s 191, 204 834 s
433 s
401
409
1424 s, 1382 m 182, 199 840 m
431 vw
469 m
456 w
483 s
MnLÁH2O
1406 vs
1411 vs
165
164
840 m
844 m
381 Bidentate chelation
388
Fe2L3Á3H2O IR
CoLÁ1.5H2O IR
NiLÁ2H2O
CuLÁH2O
ZnLÁH2O
1576 vs, 1558 vs 1401 vs
1607 vs, 1585 vs 1405 vs
175, 157 834 m
202, 180 840 w
351 Bidentate chelation
363 Bidentate chelation
386 Bidentate chelation
338 Bidentate bridging and monodentate
356 Monodentate
477 w
456 m
499 w
482 w
487 w
IR
IR
IR
1585 vs
1405 vs
180
836 m
1620 vs, 1585 vs 1386 vs
1610 vs, 1598 vs 1392 vs
234, 199 837 w
228, 206 838 w
208, 187 840 s
Raman 1609 s, 1588 m
1401 s
357
3,5-pyridinedicarboxylates
Na2LÁH2O
MnLÁ2H2O
IR
Raman 1665 m
IR
Raman 1604 m
1644 vs
1377 vs
267
289
824 w
825 m
425 m
414 w
440 m
427 w
472 m
446 w
457 w
469 m
448 m
–
399
1376 vw
411
1614 vs, 1603 vs 1398 vs
216, 205 848 m
404 Bidentate chelation
425
1393 w
1384 vs
1401 s, 1379 s
1377 vs
1377 vs
1395 vs
–
211
224
852 m
803 w
Fe2L3Á4H2O IR
1608 vs
1615 vs
1623 vs
1634 vs
1624 vs
321 Bidentate chelation
380 Bidentate chelation
362 Bidentate chelation
354 Bidentate chelation
389 Bidentate chelation
–
CoLÁ2H2O
NiLÁ3H2O
IR
214, 236 826 w
IR
246
257
229
–
819 w
823 m
837 s
CuLÁ0.5H2O IR
ZnLÁ1.5H2O IR
Raman 1613 w
840 vs
53.19 %) suggests the formation of sodium carbonate
(Fig. 9b; Table 4).
complexes occurred. It was caused by changes in the
electronic charge distribution in ligand and complex
molecules. In the (Fig. S1 and S2) spectra of 3d-metal
complexes the bands assigned to the stretching vibrations
of the carboxylate anion occurred, whereas the bands
derived from the C=O and C–O disappeared (these bands
were present in the spectra of ligand) (Table 5). In the
spectra of 3,4-pyridinedicarboxylates the strong bands
IR and Raman spectra
After metal complexation by 3,4-pyridinedicarboxylic and
3,5-pyridinedicarboxylic acids, some characteristic chan-
ges in the IR and Raman spectra of ligand and metal
123

Spectroscopic (IR, Raman) and theffirmogravimetric studies of 3d-metal cinchomeronates and…
assigned to the asymmetric stretches masCOO- were in the
range 1620–1571 cm-1 (IR) and 1609–1575 cm-1 (Ra-
man), whereas symmetric stretches (msymCOO-) in the
range: 1406–1392 cm-1 (IR) and 1411–1401 cm-1 (Ra-
man). In the spectra of 3,5-pyridinedicarboxylates mas-
COO- occurred within 1634–1603 cm-1 (IR) and
1624–1605 cm-1 (Raman) as well as symmetric stretches
(msymCOO-) in the range 1401–1377 cm-1 (IR) and at
1393 cm-1 (Raman). In the spectra of 3,4-pyridinedicar-
boxylates bands derived from the deforming in-plane
vibrations of the carboxylate anion (bsymCOO-) were in
the range 840–834 cm-1 (IR) and 844–840 cm-1 (Raman),
whereas basCOO-: 499–469 cm-1 (IR) and 487–456 cm-1
(Raman). In the spectra of 3,5-pyridinedicarboxylate
was caused by the possibility of different type of metal
coordination in one metal complex (Table 5) (Fig. 10). On
the basis of the Dm(COO-), it was concluded that in the
copper 3,4-pyridinedicarboxylate two type of copper ion
coordination occurred, i.e., bidentate bridging and mon-
odentate. In the Mn, Fe, Ni and Co 3,4-pyridinedicar-
boxylates and Mn, Fe, Co, Ni, Cu and Zn 3,5-
pyridinedicarboxylates, the metal ion was coordinated by
the bidentate chelation type of bonding. In the case of Zn
3,4-pyridinedicarboxylate, the monodentate type of coor-
dination existed.
The effect of metal ions on the electronic system of
ligands was studied on the basis of the differences between
location of bands assigned to the aromatic ring vibrations
in the IR and Raman spectra of ligands and their metal
complexes. The decrease in the wave numbers of these
bands or decrease in their intensities or their disappearance
shows destabilization of the aromatic system of ligand by
metal ion. In the spectra of 3,5-pyridinedicarboxylate
(Table 6), most bands assigned to the ring vibrations were
located at higher wave numbers comparing with the
appropriate band in ligand (i.e., in the case of 19b, 12, 17b
in the IR and Raman spectra; deforming in-plane vibrations
of bCH). In the spectra of metal complexes, some bands
occurred (they were absent in the spectra of ligand), i.e., 8b
(IR) and 8b, 3 and 19b (Raman). Some bands were shifted
b
symCOO- were present within 848-803 cm-1 (IR) and
852-840 cm1 (Raman) as well as basCOO-: 472–440 cm-1
(IR) and 427 cm-1 (Raman). On the basis of the differ-
ences between the wave numbers of the asymmetric and
symmetric stretching vibrations of the carboxylate anion
COO-, some assumption on the type of metal–ligand
coordination might be stated [33, 34]. Especially the
parameter Dm = masCOO-–msymCOO- might be useful
[33]. In the spectra of 3,4- and 3,5-pyridinedicarboxylates,
more than one band assigned to the stretching vibrations of
the carboxylate anion were present. In some cases, these
bands differed in the values of their wave numbers which
Fig. 10 Proposed types of
metal–ligand coordination:
a 3,5-pyridinedicarboxylic acid
with manganese, iron, cobalt,
nickel, copper, zinc (bidentate
chelation); b 3,4-
pyridinedicarboxylic acid with
manganese, iron, cobalt, nickel
(bidentate chelation); c 3,4-
pyridinedicarboxylic acid with
zinc (monodentate); d 3,4-
pyridinedicarboxylic acid with
copper (bidentate bridging and
monodentate)
123

´
G. Swiderski et al.
Table 6 Wave numbers and intensity of selected wave numbers from the IR and Raman spectra of 3,5-pyridinedicarboxylic acid and its metal
complexes
3,5pda
IR
3,5-pyridinedicarboxylate
Versanyi
Sodium
IR
Manganese
IR Raman
Iron
IR
Cobalt Nickel
Copper Zinc
Raman
Raman
IR
IR
IR
IR
Raman
1603 m 1609 m 1605 s 1584 m 1603 vs 1604 s
1576 s 1575 m 1556 vs 1567 s
1466 w 1463 m 1445 s 1446 m 1456 s 1463 s
–
–
–
–
–
–
–
1613 s mCCar 8a
1586 s mCCar 8b
–
–
1558 s 1559 vs 1558 s
1531 m
1474 w
–
–
–
–
mCCar 19a
1420 w
1304 s
–
–
1416 vs 1415 s
1285 m 1284 vw 1299 m 1301 vw 1293 m 1299 m 1290 w 1285 s 1293 m 1293 w bCHar
1245 w 1248 w 1266 m 1245 m 1249 w bCHar 9a
1435 s
–
1437 s 1440 m 1433 m 1445 m 1450 s 1453 s mCCar 19b
3
1266 m 1266 w 1239 w 1251 vw 1238 m 1247 vw
1219 s 1208 w 1189 w 1211 w
1168 vs 1150 vw 1151 m 1151 w 1150 m 1149 w
1124 m 1106 vw 1122 w 1124 m 1149 vw
–
–
–
1204 w 1207 w 1205 vw 1194 m 1205 m
–
–
–
–
mCNar
bCHar
bCHar
–
–
–
1150 w 1157 w 1158 m 1156 m
1127 w 1134 w 1140 m 1133 m
1110 m 1095 w 1099 m 1089 w
1065 s 1035 vs 1031 m 1037 s
–
1083 vw
–
–
1096 m
–
bCHar 18b
1031 m 1033 vs 1030 w 1034 w 1032 w 1031 m 1032 m 1033 vs bCHar 18a
942 m
912 m
854 w
–
946 w
919 w
869 w
801 m
–
962 w
925 m
824 m
–
965 vw 973 w
931 vw 935 m
988 vw
–
–
–
977 w
977 m
938 w
985 m
bCHar 12
936 vw 929 w
938 w
826 w
–
935 vw 942 w
938 vw bCHar 17b
825 m
–
848 m
852 m
805 w
774 w
684 w
–
815 w
–
837 w
–
843 vw 837 m
840 s
cCHar
–
–
–
807 m
780 w
cCHar 10a
cCHar
783 m
697 s
642 w
545 m
773 s
687 m
–
776 w
699 m
664 w
572 vw
769 s
765 m
693 m
–
769 m
695 w
–
770 m
668 m
–
755 m
770 s
687 m
668 m
545 m
682 w
647 w
530 w
695 m
677 m
703 vw aCCC 6a
–
–
–
–
–
–
aCCC 6b
aCCC
564 m
510 w
535 m
528 vw 531 2
band intensity: s strong, m medium, w weak, vw very weak, sh shoulder; type of vibrations: m stretching, b bending in-plane, bring ring bending
in-plane, c bending out-of-plane, a ring bending, u ring deformation, sym symmetric, as asymmetric
toward lower wave numbers comparing with ligand (18b,
18a, mCN and cCH in IR spectra). In the spectra of sodium
3,5-pyridinedicarboxylate, more bands disappeared com-
pared with other metal complexes. In the spectrum of
sodium salt, the wave numbers of some bands decreased in
their values compared with the spectrum of 3,5-
pyridinedicarboxylic acid, whereas in the spectra of 3d-
metal complexes wave numbers of some bands increased in
comparison with the spectrum of ligand.
electronic system of ligands (similarly as it was stated in
the case of 3d-metal complexes of pyridinemonocarboxylic
acid, i.e., picolinic acid) [22]. 3d-Metals strongly affected
the electronic system of 3,4-pyridinedicarboxylic acid than
3,5-pyridinedicarboxylic acid (on the basis of the changes
in the location and intensity of the aromatic ring vibrations
in the spectra of ligands and complexes). The carboxylic
groups in the 3,5-pyridinedicarboxylic acid are symmetri-
cally located taking into account the location of the nitro-
gen atom in the aromatic ring. This causes a symmetric
distribution of the electronic charge in the molecule of 3,5-
pyridinedicarboxylic acid. In the case of 3,4-pyridinedi-
carboxylic acid, the carboxylic groups are unsymmetrically
located which translates into unsymmetrically distributed
electronic charge in 3,4-pyridinedicarboxylic acid mole-
cule. The differences in the location of the carboxylic
groups and the electronic charge distribution in
pyridinedicarboxylic acids cause that 3d-transition metal
ions in different way affect the molecular structure of
studied ligands. This causes different physico-chemical and
thermal properties of studied metal complexes. The similar
conclusion was described in the papers devoted to the salts
In the spectra of 3,4-pyridinedicarboxylates (Table 7),
bands no. 8b, 19a, 3, mCN, bCH, 12, cCH, 6a (IR) as well
as 8b, 19a, 3, 12, 17b, mCN and 6a (Raman) were located at
higher wave numbers comparing with the appropriate ones
in the spectrum of 3,4-pyridinedicarboxylic acid. Whereas
bands no. 9a, 18b and cCH (IR) and 19a, 8a (Raman) were
shifted toward lower wave numbers comparing with ligand.
Bands no. 19b and 6b (IR) as well as 19b and cCH (Ra-
man) were present in the spectra of acids and disappeared
in the spectra of complexes.
Comparing the IR and Raman spectra of 3,4- and 3,5-
pyridinedicarboxylic acids and their 3d-metal complexes, it
could be concluded that 3d-transitional metal stabilized the
123

Spectroscopic (IR, Raman) and theffirmogravimetric studies of 3d-metal cinchomeronates and…
Table 7 Wave numbers and intensity of selected wave numbers from the IR and Raman spectra of 3,4-pyridinedicarboxylic acid and its metal
complexes
3,4pda
IR
3,4-pyridinedicarboxylate
Versanyi
Sodium
IR
Manganese
Iron
Cobalt Nickel Copper Zinc
Raman
Raman
IR
Raman IR
IR
IR
IR
IR
Raman
1607 vs 1613 m
–
–
1606 w
1581 w
–
–
–
1608 s
1575 m
1548 m
–
–
–
–
–
–
–
–
–
–
–
–
1609 s mCCar 8a
1588 m mCCar
–
–
1521 m 1534 m 1546 m 1548 w
1558 s 1554 s mCCar 8b
1472 m 1492 m 1481 s
1488 w
1424 s
1382 w
1491 m 1492 s 1488 s 1493 m 1490 s 1491 m 1491 m 1494 s mCCar 19a
1456 m 1453 vw
1399 s
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
mCCar 19b
mCHar 14
–
1276 w 1285 m 1273 w
1260 w 1251 s 1241 w
1177 w 1170 vs 1197 w
1287 vw 1285 w 1285 w 1283 w 1286 w 1286 w 1283 w 1286 w 1287 w bCHar
1239 vw 1229 w 1222 w 1231 m 1235 w 1234 w 1237 m bCHar 9a
1197 m 1200 w 1203 w 1191 w 1195 w 1194 w 1192 m 1195 w 1201 w mCNar
1170 w 1171 w 1170 m 1167 m 1167 w 1167 w 1166 m 1167 w 1168 m bCHar
1120 m 1126 vw 1127 vw 1124 w 1125 w 1122 m 1123 w 1124 w 1120 m 1124 w 1127 w bCHar
1064 vs 1052 m 1054 w 1058 w 1058 m 1059 m 1064 w 1068 w 1069 m 1072 w 1071 m bCHar 18b
3
–
–
1157 m
–
–
1160 w
1078 s
973 m
–
975 w
929 vw
836 vw
819 m
774 vw
732 vw
672 m
–
977 w
930 vw
853 m
–
–
981 vw 979 vw
955 vw 950 vw
–
993 w
952 w
840 w
–
–
–
–
988 w
950 w
838 w
–
990 vw bCHar 12
944 vw bCHar 17b
–
–
947 w
844 s
–
867 vw
826 m
784 vw
709 vw
684 w
–
862 w
–
844 m
–
853 m
–
836 m 837 m
840 s
cCHar
–
–
–
–
cCHar 10a
cCHar
779 m
731 m
677 w
660 s
587 m
786 m
708 m
678 m
646 m
572 w
790 m
708 m
678 s
–
790 vw 772 m
707 vw 707 m
782 w
714 m
681 m
–
782 m 779 m
718 m 722 m
683 m 685 m
785 w
722 w
684 m
650 vw
606 w
734 vw aCCC
684 w
–
677 s
–
686 m
–
aCCC 6a
aCCC 6b
–
–
585 vw
572 vw
595 m
599 vw 582 m
610 w
615 m 609 w
612 vw aCCC
band intensity: s strong, m medium, w weak, vw very weak, sh shoulder; type of vibrations: m stretching, b bending in-plane, bring ring bending
in-plane, c bending out-of-plane, a ring bending, u ring deformation, sym symmetric, as asymmetric
and metal complexes of 2, 3- and 4-pyridinecarboxylic
acids [19, 20].
pyridinedicarboxylic acids cause that 3d-transition metal
ions in different way affect the molecular structure of
studied ligands. This causes different physico-chemical and
thermal properties of studied metal complexes.
Conclusions
Acknowledgements This work was financially supported by Bia-
lystok University of Technology in the frame of funding for statutory
The thermal decomposition of the two series of hydrated
complexes of Mn(II), Fe(III), Co(II), Ni(II), Cu(II) and
Zn(II) with 3,4- and 3,5-pyridinedicarboxylic acids is a
multistage process. At first the complexes lose all water
molecules in one or two steps which are connected with
endothermic effects. After dehydration, in the next stages,
the anhydrous complexes decompose exothermally which
can be also attributed to oxidation of organic matter and the
gaseous products evolved during thermal decomposition.
Finally, metal oxides are formed. Larger thermal stability is
observed for anhydrous complexes of 3,5-pda ligand which
can be a result of more symmetric structure and charge
distribution of this ligand contrary to the thermal stability
of 3,4-pda series. The differences in the location of the
carboxylic groups and the electronic charge distribution in
´
research (No. S/WBiIS/1/2012).
Open Access This article is distributed under the terms of the
Creative Commons Attribution 4.0 International License (http://crea
tivecommons.org/licenses/by/4.0/), which permits unrestricted use,
distribution, and reproduction in any medium, provided you give
appropriate credit to the original author(s) and the source, provide a
link to the Creative Commons license, and indicate if changes were
made.
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