Thermal, spectroscopic, X-ray and theoretical studies of metal complexes (sodium, manganese, copper, nickel, cobalt and zinc) with pyrimidine-5-carboxylic and pyrimidine-2-carboxylic acids

Article abstract of DOI:10.1007/s10973-019-08594-x

The new 3d metal complexes of pyrimidine-2-carboxylic (2PCA) and pyrimidine-5-carboxylic (5PCA) acids were synthesized and characterized using thermal analysis (TG–DSC, TG–FTIR), X-ray, spectroscopic (IR, Raman) methods and theoretical (DFT) studies. In the complexes of pyrimidine-2-carboxylic acid of the general formula M(2PCA)₂·xH₂O (where 2PCA-pyrimidine-2-carboxylate; M = Mn(II), Co(II), Ni(II), Cu(II) and Zn; x = 0 for Mn and Cu; x = 2 for Co, Ni and Zn) coordination of metal ions occurs through nitrogen atom from pyrimidine ring and carboxylate oxygen atom. The complexes of pyrimidine-5-carboxylic acid of the general formula M(5PCA)₂·xH₂O (where 5PCA—pyrimidine-5-carboxylate; M = Mn(II), Co(II), Ni(II), Cu(II) and Zn; x = 6 for Cu and 4 for remaining complexes) were obtained as monomeric isostructural compounds. Coordination of metal centers occurs through two nitrogen atom from different pyrimidine-5-carboxylate ligand and four oxygen atoms from water molecules. The IR and Raman spectra of free acids as well as obtained metal(II) complexes were described in detail. Aromaticity (HOMA, EN, GEO and I₆) of complexes was determined and discussed. The investigated compounds decompose in air in two main stages connected with dehydration and decomposition/burning of anhydrous compounds to the suitable metal oxides. Thermal decomposition in nitrogen leads to the evolution of water, carbon oxides, ammonia and pyrimidine molecules.

Full text of DOI:10.1007/s10973-019-08594-x

Journal of Thermal Analysis and Calorimetry
https://doi.org/10.1007/s10973-019-08594-x(0123456789(). -, vo Vl
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Thermal, spectroscopic, X-ray and theoretical studies of metal
complexes (sodium, manganese, copper, nickel, cobalt and zinc)
with pyrimidine-5-carboxylic and pyrimidine-2-carboxylic acids
1
1 •
2 •
3 •
1 •
1
´
•
´
R. Swisłocka R. Łyszczek S. Wojtulewski M. Samsonowicz W. Lewandowski
G. Swiderski
Received: 14 November 2018 / Accepted: 19 July 2019
Ó The Author(s) 2019
Abstract
The new 3d metal complexes of pyrimidine-2-carboxylic (2PCA) and pyrimidine-5-carboxylic (5PCA) acids were syn-
thesized and characterized using thermal analysis (TG–DSC, TG–FTIR), X-ray, spectroscopic (IR, Raman) methods and
theoretical (DFT) studies. In the complexes of pyrimidine-2-carboxylic acid of the general formula M(2PCA) ÁxH O
2
2
(
where 2PCA-pyrimidine-2-carboxylate; M = Mn(II), Co(II), Ni(II), Cu(II) and Zn; x = 0 for Mn and Cu; x = 2 for Co, Ni
and Zn) coordination of metal ions occurs through nitrogen atom from pyrimidine ring and carboxylate oxygen atom. The
complexes of pyrimidine-5-carboxylic acid of the general formula M(5PCA) ÁxH O (where 5PCA—pyrimidine-5-car-
2
2
boxylate; M = Mn(II), Co(II), Ni(II), Cu(II) and Zn; x = 6 for Cu and 4 for remaining complexes) were obtained as
monomeric isostructural compounds. Coordination of metal centers occurs through two nitrogen atom from different
pyrimidine-5-carboxylate ligand and four oxygen atoms from water molecules. The IR and Raman spectra of free acids as
well as obtained metal(II) complexes were described in detail. Aromaticity (HOMA, EN, GEO and I ) of complexes was
6
determined and discussed. The investigated compounds decompose in air in two main stages connected with dehydration
and decomposition/burning of anhydrous compounds to the suitable metal oxides. Thermal decomposition in nitrogen leads
to the evolution of water, carbon oxides, ammonia and pyrimidine molecules.
Keywords Pyrimidine-2-carboxylic acid Á Pyrimidine-5-carboxylic acid Á 3d metal complexes Á Aromaticity indices Á
Thermal analysis
Introduction
processes or in binding, storage and transport of oxygen
1]. Many years ago, it was noticed that some complex
[
Complexes of transition metals (Co, Mn, Ni, Zn, Cu) play
an important role in the life processes of living organisms.
They are, among others, components of enzymes, proteins
and vitamins; they participate in oxidation–reduction
compounds of transition metals, including copper and zinc,
may react with the superoxide anion radical in a manner
reminiscent of the activity of native superoxide dismutases.
Hence, they were called superoxide dismutase mimetics
SOD [2]. Ligands that are heterocyclic nitrogen bases have
a significant effect on increasing the reactivity of copper(II)
complexes with superoxide anion radicals. Although cop-
per(II) complexes show a weaker antioxidant effect than
the SOD enzyme, they are important as potential super-
oxide dismutase mimetics due to the low molecular weight
´
G. Swiderski
g.swiderski@pb.edu.pl
&
1
Department of Chemistry, Biology and Biotechnology,
Faculty of Civil Engineering and Environmental Engineering,
Bialystok University of Technology, Wiejska 45E,
[
3, 4]. Complexes of transition metals have also been used
1
5-351 Białystok, Poland
as medicines. In many cases, the ligand responsible for the
therapeutic effect of the drug may increase efficacy action
after the complexation by metal. Metal ions in complexes
with antitumor active ligands play the role as modulators of
activity [5]. The metal affects the redox activity of the
2
3
Department of General and Coordination Chemistry, Faculty
of Chemistry, Maria Curie-Skłodowska University, M.C.
Skłodowskiej Sq. 2, 20-031 Lublin, Poland
Institute of Chemistry, University of Bialystok,
Ciolkowskiego 1 K, 15-245 Białystok, Poland
123

´
G. Swiderski et al.
ligand, its mode of action, therapeutic efficacy, solubility,
stability and a number of other properties [6]. Complexa-
tion by the metals effects on the change in the distribution
of electronic charge in the ligand, which translates into a
change in the physicochemical and biological properties of
the chemical compound [7–10]. Studies have shown that
transition metals influence the stability of the electron
system of complexes the aromatic acids [11–14]. This
impact depends not only on the properties of metal, but
also on the way the ligand–metal coordination. In com-
plexes of heteroaromatic acids, the metal may be attached
via a carboxyl anion and heteroatoms of the aromatic ring.
These types of binding are formed inter alia in the pyridine-
in the treatment of HIV, hepatitis B), antimalarial and
anesthetic [34] properties. Some of the pyrimidine
derivatives have been used as plant protection products
[35]. Orotic acid is commonly known as a precursor in
pyrimidine biosynthesis [36]. As a component of the daily
diet is found in milk and other dairy products. In the body,
it is transformed into uridine, which then participates in the
pyrimidine recovery pathway in the kidneys, liver and
erythrocytes [37].
In order to improve the bioavailability of orotic acid, its
combinations with organic cations (e.g., choline, carnitine)
2
?
2?
2?
?
or metal ions (Mg , Zn , Ca , K ) are used. Such
combinations may be used in the therapy of metabolic
syndromes and in bodybuilding [38].
2
-carboxylic, pyrazine-2-carboxylic or pyrimidine-2-car-
boxylic acid complexes [15–18]. The pyrimidine-5-car-
boxylic acid may form complexes by attaching a metal via
a ring nitrogen atom without the participation of a car-
boxylic group [19].
The aim of the work was to obtain complexes of tran-
sition metals 3d with carboxylic acid pyrimidine deriva-
tives. A series of complexes with ligands having different
carboxylic acid positions relative to the nitrogen atoms in
the aromatic ring (pyrimidine-2-carboxylic acid and
pyrimidine-5-carboxylic acid) were synthesized. The
influence of the metal on the electron system of the ligand
and the thermal properties of the obtained complexes
depending on the type of metal–ligand coordination were
evaluated.
In the pyridinecarboxylic acid complexes, various types
of metal–ligand coordination depending on the position of
the nitrogen atom relative to the carboxylic group were
observed [20–28]. In the case of 2-pyridinecarboxylic acid
(
picolinic acid) in which the nitrogen atom is located in
close proximity to the carboxyl group, the metal is coor-
dinated through the carboxyl group and the nitrogen atom
to form a chelate ring [20–22]. In the case of nicotinic acid,
a type of coordination through the carboxylic group was
observed [23–25]. In the case of isonicotinic acid, the
formation of complexes with coordination of metal–nitro-
gen atom and metal–carboxylic group was noticed [26–28].
It was found that the method of coordination affects the
electronic structure of the aromatic system as well as the
thermal properties of the complex [29, 30].
Experimental
Synthesis of complexes
The complexes of manganese(II), cobalt(II), nickel(II),
zinc and copper(II) with pyrimidine-2-carboxylic (2PCA)
acid complexes were prepared as follows: 49.6 mg of acid
was added to the stoichiometric quantity of sodium
Zinc complexes with pyridinecarboxylic acids (nico-
tinic, picolinic, isonicotinic) show different thermal sta-
bility. Studies have shown that the complex with picolinic
acid (coordination O, N) is less thermally stable than
complexes with nicotinic acid and isonicotinic acid
3
-3
hydroxide (4 cm ; 0.1 mol dm ). The suspension was
placed in an ultrasonic bath at 70 °C until the acid dis-
solved. Then, 2 cm of metal(II) chloride solution
3
-
3
(0.1 mol dm ) was added. The solution was shaken on a
shaker for 1 h at room temperature, and the complexes
were allowed to stand. The obtained precipitates/or crystals
were washed with water to rinse the chlorides under the
[
29, 30].
In the present work, complexes of pyrimidinecarboxylic
acids were investigated. Carboxylic acids derived from
diazines (Fig. 1) due to the number of potential chelating
sites can form various coordination structures in relation-
ships with metal ions [18, 19, 31, 32]. The pyrimidine
derivatives are found in living organisms where they play a
fundamental role in many life processes. The most
important naturally occurring pyrimidines are the pyrim-
idine uracil bases, thymine and cytosine, which are the
basic building blocks of nucleosides in deoxyribonucleic
acid (DNA) and ribonucleic acid (RNA).
control of AgNO solution. Analogously, metal(II) pyrim-
3
idine-5-carboxylate complexes were obtained.
Elemental analysis
The elementary analysis was carried out using the CHN
2400 PerkinElmer Analyzer. The water content was
determined from the thermogravimetric curves. Table 1
presents the results of elemental analysis of pyrimidine-2-
carboxylic acid complexes, and Table 2 presents the results
of elemental analysis for pyrimidine-5-carboxylic acid
complexes.
Many of the pyrimidine derivatives show a wide range
of biological activities and are known for their anticancer
(
fluorouracil) [33], antimicrobial, analgesic, antiviral (also
1
23

Thermal, spectroscopic, X-ray and theoretical studies of metal complexes…
Fig. 1 Structures of
pyrimidinecarboxylic acids
Pyrimidine-2-carboxylic acid
Pyrimidine-4-carboxylic acid
Pyrimidine-5-carboxylic acid
Table 1 Elemental analysis for pyrimidine-2-carboxylates
Compound name
Formula
Content C/%
Content H/%
Content N/%
Yield/%
Color
Calc.
Exp.
Calc.
Exp.
Calc.
Exp.
Manganese pyrimidine-2-carboxylate
Cobalt pyrimidine-2-carboxylate
Nickel pyrimidine-2-carboxylate
Zinc pyrimidine-2-carboxylate
Copper pyrimidine-2-carboxylate
Mn(2PCA)
2
39.89
35.21
35.23
34.55
38.78
39.32
35.42
35.11
34.51
38.63
2.01
2.95
2.96
2.96
1.95
1.99
2.97
2.83
2.81
1.91
18.61
16.42
16.43
16.43
18.09
18.14
16.14
16.18
16.27
18.16
80
Yellow
Orange
Green
White
Blue
Co(2PCA)
2
ÁH
Á2H
Á2H
2
O
75
Ni(2PCA)
2
2
O
70–80
75
Zn(2PCA)
2
2
O
Cu(2PCA)
2
70
2
5 3 2 2
PCA = C H N O
Table 2 Elemental analysis for pyrimidine-5-carboxylates
Compound name
Formula
Content C/%
Content H/%
Content N/%
Yield/%
Color
Calc.
Exp.
Calc.
Exp.
Calc.
Exp.
Manganese pyrimidine-5-carboxylate
Cobalt pyrimidine-5-carboxylate
Nickel pyrimidine-5-carboxylate
Zinc pyrimidine-5-carboxylate
Copper pyrimidine-5-carboxylate
Mn(5PCA)
2
Á4H
Á4H
Á4H
Á4H
Á6H
2
O
32.18
31.84
31.86
31.31
28.75
32.20
31.51
30.84
31.42
28.57
3.78
3.74
3.74
3.68
4.34
3.69
3.68
3.77
3.55
4.25
15.01
14.85
14.86
14.60
13.41
14.55
14.44
14.02
14.34
13.30
80
Yellow
Orange
Green
White
Blue
Co(5PCA)
2
2
O
75–80
80
Ni(5PCA)
Zn(5PCA)
Cu(5PCA)
2
2
O
2
2
O
85
2
2
O
70–80
5
5 3 2 2
PCA = C H N O
Thermal analysis
room temperature up to 700 °C at a heating rate of
-1
20 °C min
in
flowing
nitrogen
atmosphere
3 -1
(25 cm min ).
Thermal analyses of the investigated complexes were car-
ried out by the thermogravimetric (TG) and differential
scanning calorimetry (DSC) methods using the Setsys
FTIR and Raman study
1
6/18 analyzer Setaram). The samples (about 5–8 mg)
were heated in alumina crucibles in the range of
-
The FTIR spectra were recorded with an Alfa (Bruker)
-1
spectrometer within the range of 400–4000 cm . Samples
1
3
0–1000 °C at a heating rate of 10 °C min in flowing air
3
-1
atmosphere (v = 0.75 dm h ). The TG-FTIR coupled
measurements performed on Q5000 (TA) apparatus cou-
pled with the Nicolet 6700 spectrophotometer. The samples
of about 20–30 mg were heated in platinum crucibles from
in the solid state were measured in KBr matrix pellets and
ATR technique. FT-Raman spectra of solid samples were
-
1
recorded in the range of 400–4000 cm with a MultiRam
(Bruker) spectrometer.
123

´
G. Swiderski et al.
Theoretical calculations
SOD activity and HOMO, LUMO energies
To calculate optimized geometrical structures of pyrim-
idinecarboxylic acids and copper(II) complexes, the
quantum–mechanical method was used: density functional
SOD activity for copper(II) complexes was determined
theoretically on the basis of the energy calculations for
geometrically optimized structures. As a theoretical
parameter defining the radical scavenging activity by the
studied complexes, HOMO and LUMO energy values and
EA affinity value were selected:
(
DFT) hybrid method B3LYP with non-local correlation
provided by Lee–Young–Parr expression. All calculations
for acids were carried out in functional base
6
–311??G(d,p) and for acids and copper complexes in
TEE-Cu(I)–TEE-Cu(II), where TE E-Cu(I) is the total
energy of the complex E–Cu(I) and TEE–Cu(II) with the
total energy of the E–Cu(II) complex.
LANL2DZ base. Calculations were performed using the
Gaussian09 package [39]. Experimental spectra were
interpreted in terms of calculated at DFT method in
B3LYP/6-311??G(d,p) level and literature data [40, 41].
Theoretical wavenumbers were scaled according to the
X-ray analysis
formula:
mscaled = 0.98 Á m
for
B3LYP/6-
Suitable crystals were sequentially mounted on a fiber loop
and used for X-ray measurements. X-ray data were col-
lected on the Oxford Diffraction SuperNova DualSource
diffractometer with use of the monochromated CuKa X-ray
source (k = 1.54184). The crystals were kept at 100 K
during data collection. Data reduction and analytical
absorption correction were performed with CrysAlis PRO
[45]. Using Olex2 [46], the structures were solved with the
ShelXS [47] structure solution program using Direct
Methods and refined with the ShelXL [47] refinement
package using Least Squares minimization.
calculated
3
11??G(d,p) level method. Spectral assignments used the
normal oscillation of the pyrimidine ring measured using
B3LYP/6-311??G(d,p).
The aromaticity indices (HOMA, GEO, EN, I ) were
6
calculated for geometric structures (theoretical and calcu-
lated) of pyrimidine-2-carboxylates and pyrimidine-5-car-
boxylates. The HOMA index (harmonic oscillator model of
aromaticity) differs from all other geometry-based ones by
assuming another reference bond length. In this model,
instead of the mean bond length a concept of the optimal
bond length is applied [42, 43]:
The non-hydrogen atoms were refined anisotropically.
The positions of OH hydrogen atoms were found on a
Fourier difference map and refined. Hydrogen atoms of
aromatic ring were introduced in calculated positions with
idealized geometry and constrained using a rigid body
model with isotropic displacement parameters equal to 1.2
of the equivalent displacement parameters of the parent
atoms. Summaries of relevant crystallographic data are
given in Tables 3 and 6 for pyrimidine-2-carboxylate and
pyrimidine-5-carboxylate complexes. The supplementary
crystallographic data for this paper can be obtained free of
charge from The Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data_request/cif.
h
i
À
Á
a X
2
2
HOMA ¼ 1 À a R À Rav
þ
ðRav À RiÞ
opt
n
¼
1 À EN À GEO
within the confines of the HOMA model, it is possible to
obtain two components which describe different contribu-
tion to decrease in aromaticity, i.e., (a) due to bond elon-
gation (the EN component) and (b) due to bond length
alternation (the GEO component). The value of HOMA
index is equal 1 for the entire aromatic system; HOMA = 0
when the structure is non-aromatic and HOMA \ 0 for
anti-aromatic ring.
The value of the Bird’s aromaticity index (I , I )
5
6
describes the equation [44]:
I ¼ 100f1 À ðV=VkÞg
where V is for the five-membered rings 35 and the six-
Results
k
Crystal structure description
membered 33.3, and V is calculated from the equation:
"
#
1
2
n
Isostructural copper(II) and zinc(II) pyrimidine-2-car-
X
where n -average binding order, n-bond order based on
2
V ¼ ð100=navÞ
ðn À n Þ =n
r
av
boxylates M(2PCA) Á2H O crystallize in the monoclinic
2
2
r¼1
P2 /c space group (Table 3). The asymmetric unit is a half
1
of the complex molecule, and the metal cations are located
on a crystallographic inversion center. The cobalt and zinc
metal cations are coordinated identically by two pyrim-
idine-2-carboxylate ligands in the equatorial plane and by
two water molecules in the axial positions. The pyrimidine-
av
bond length: n = (a/R) - b, a and b-parameters depending
on the type of atoms in the bond.
1
23

Thermal, spectroscopic, X-ray and theoretical studies of metal complexes…
Table 3 Crystal data and
Empirical formula
Co(C
5
H
4
N
2 2
O )
2
Á2H
2
O
Zn(C
5
H
4
N
2 2
O )
2
Á2H
2
O
structure refinement of
pyrimidine-2-carboxylates
Formula weight
341.15
Monoclinic
P2 /c
347.59
Monoclinic
P2 /c
Crystal system
Space group
1
1
˚
a/A
5.201(7)
11.713(2)
10.041(7)
90
5.234(1)
11.726(3)
9.793(8)
90
˚
b/A
˚
c/A
a/°
b/°
c/°
96.448(4)
90
97.8387(12)
90
3
˚
Volume/A
607.9(5)
2
595.4(8)
2
Z
-
3
q
calc/g cm
1.864
1.939
3
Crystal size/mm
0.312 9 0.091 9 0.091
0.317 9 0.153 9 0.109
Final R indexes [I C 2r (I)]
Final R indexes [all data]
R
R
1
1
= 0.0308, wR
= 0.0367, wR
2
2
= 0.0794
= 0.0824
R
1
1
= 0.0268, wR
2
2
= 0.0705
= 0.0708
R
= 0.0272, wR
-3
˚
Largest diff. peak/hole/e A
0.25/- 0.56
0.33/- 0.70
CCDC no.
1,577,381
1,857,354
2
-carboxylate ligands are bound to metal cations in a
bidentate N,O-chelate mode, forming five-membered rings
Fig. 2). The bonds of the coordination sphere M–N1, M–
O1 and M–Ow are nearly equal in length (2.066(1)–
Table 4 Selected geometrical parameters of cobalt (II) and zinc
pyrimidine-2-carboxylates complexes
(
A˚ , °
Co
Zn
1.338(2)
N1–C2
1.337(2)
˚
.123(2) A), and the overall coordination sphere around
2
C2–N3
1.324(2)
1.337(3)
1.381(3)
1.380(3)
1.335(3)
1.528(3)
1.275(2)
1.222(3)
2.066(1)
2.114(1)
2.094(1)
1.328(2)
1.341(2)
1.387(2)
1.384(2)
1.337(2)
1.533(2)
1.280(2)
1.228(2)
2.082(2)
2.103(5)
2.123(2)
cobalt and zinc cations can be described as an octahedral.
However, the analysis of the valence angles O–M–Ow and
O–M–N reveal a small distortion of the coordination
spheres, since the N1–Co–O1w and N1–Zn–O1 valence
angles are not a right angles and equal 79.5(5) and 79.9(6)
degrees, respectively (Table 4).
N3–C4
C4–C5
C5–C6
C6–N1
C5–C7
C7–O1
The hydrogen bonds patterns are marked in Fig. 3 as a
dashed line. There are three intermolecular hydrogen bonds
in the crystal structure of Co and Zn pyrimidine-2-car-
C7–O2
M–O1
…
boxylate complexes. Two of them are O–H O type and
…
M–N1
one is O–H N type. Coordinated water molecules acts as a
M–O1w
proton donor, while O1 (coordinated), O2 (uncoordinated)
and N3 (uncoordinated) atoms play a role of the proton
N1–C2–N3
C2–N3–C4
N3–C4–C5
C4–C5–C6
C5–C6–N1
C6–N1–C2
C2–C7–O1
C2–C7–O2
O1–M–O1 W
O1–M–N1
O1 W–M–N1
125.8(2)
125.5(1)
116.2(2)
122.4(2)
117.1(2)
121.1(2)
117.4(2)
115.4(2)
118.5(2)
91.8(6)
116.4(1)
122.4(1)
116.8(1)
121.1(1)
117.7(1)
115.3(1)
118.0(1)
87.3(5)
M: Co, Zn
O1w
C5
C6
C4
N1
N3
C2
91.4(7)
79.9(6)
C7
O1
79.5(5)
87.1(4)
O2
acceptors in hydrogen bonding. It is worth to emphasize
that the hydrogen atom H1WB is a donor in a bifurcated
Fig. 2 The molecular structure of the Co(II) and Zn pyrimidine-2-
carboxylates complexes
(three-centered) hydrogen bond, where O2 and N3 atoms
123

´
G. Swiderski et al.
Fig. 3 Crystal structure of the Co(II) and Zn pyrimidine-2-carboxylates complexes. Hydrogen bonds are presented as a dashed lines
of the neighboring ligand molecule are acceptor centers.
Selected geometrical parameters of the hydrogen bonds
together with the symmetry codes (symm. op. 2) are pre-
sented in Table 5.
water molecule, and the symmetry of the structure is sig-
ꢀ
nificantly lower (P1).
However, in all cases the asymmetric unit is a half of the
complex molecule and the metal cations are located on a
crystallographic inversion center. The metal cations are
coordinated identically by two pyrimidine-5-carboxylate
ligands and two water molecules in the equatorial plane
and by two water molecules in the axial positions. The
pyrimidine-5-carboxylate ligands are bound to metal
The complexes of manganese(II), cobalt(II) and zinc
with pyrimidine-5-carboxylic acid of the formula
M(5PCA) Á4H O crystallize in the monoclinic P2 /c space
2
2
1
group (Table 6). The crystal structure of copper complex
M(5PCA) Á6H O contains an additional uncoordinated
2
2
Table 5 Geometrical parameters of the hydrogen bonds of cobalt (II) and zinc pyrimidine-2-carboxylates complexes
˚
d(D–H)/A
˚
d(H–A)/A
˚
d(D–A)/A
D
H
A
D–H–A/°
Symm. op. 2
Co
Zn
O1 W
O1 W
O1 W
O1 W
O1 W
O1 W
H1 WA
H1 WB
H1 WB
H1 WA
H1 WB
H1 WB
O1
O2
N3
O1
O2
N3
0.79(4)
0.72(5)
0.72(5)
0.78(3)
0.74(3)
0.74(3)
1.952
2.601
2.272
1.978
2.597
2.236
2.734(2)
3.229(3)
2.883(2)
2.737(2)
3.250(2)
2.858(2)
169(3)
147(4)
143(4)
164(3)
147(3)
142(3)
1 - x, 1 - y, 1 - z
x, 1/2 - y, - 1/2 ? z
x, 1/2 - y, - 1/2 ? z
- 1 ? x, y, z
1 - x, - 1/2 ? y, 1.5 - z
1 - x, -1/2 ? y, 1.5 - z
1
23

Thermal, spectroscopic, X-ray and theoretical studies of metal complexes…
Table 6 Crystal data and structure refinement of pyrimidine-5-carboxylates
Empirical formula
Mn(C
5
H
4 2 2
N O )
2
Á4H
2
O
Co(C
5 4
H N
2 2
O )
2
Á4H
2
O
Zn(C
5
H
4 2 2
N O )
2
Á4H
2
O
Cu(C
5
H
4 2 2
N O )
2
Á4H
2 2
O,2H O
Formula weight
Crystal system
Space group
373.19
Monoclinic
P2 /c
377.18
Monoclinic
P2 /c
383.62
Monoclinic
P2 /c
417.82
Triclinic
P - 1
1
1
1
˚
a/A
6.520(2)
12.455(3)
8.510(1)
90
6.514(6)
12.456(1)
8.508(3)
90
6.526(8)
12.470(5)
8.525(8)
90
6.189(1)
6.764(6)
9.521(2)
˚
b/A
˚
c/A
a/°
b/°
c/°
105.450(5)
92.93(7)
96.02(2)
380.79(4)
1
98.089(6)
90
98.12(2)
90
98.03(5)
90
3
˚
Volume/A
684.24(2)
2
683.50(3)
2
687.12(4)
2
Z
-
3
q
calc/g cm
1.811
1.833
1.854
1.822
3
Crystal size/mm
0.179 9 0.107 9 0.092 0.305 9 0.163 9 0.122 0.259 9 0.182 9 0.182 0.631 9 0.303 9 0.216
= 0.0364, = 0.0526, = 0.0282, = 0.0340,
= 0.0966 = 0.1358 = 0.0718 = 0.0953
= 0.0382, = 0.0583, = 0.0287, = 0.0387,
= 0.0981 = 0.1451 = 0.0722 = 0.0970
Final R indexes [I C 2r (I)]
Final R indexes [all data]
R
1
R
1
R
1
R
1
wR
2
wR
2
wR
2
wR
2
R
1
R
1
R
1
R
1
wR
2
wR
2
wR
2
wR
2
-3
˚
Largest diff. peak/hole/e A
0.39/- 0.57
0.81/- 1.07
0.32/- 0.78
0.40/- 0.69
CCDC no.
1,577,382
1,577,386
1,577,385
1,577,383
cations in a monodentate mode to the N1 nitrogen atom of
the aromatic ring (Figs. 4 and 5). The analysis of the
valence angles O1w–M–O2w, O1w–M–N1 and O1w–M–
N1 does not indicate a distortion of the coordination
sphere, since all three angles are close to the right angle.
Additionally, the bond lengths: M–N1, M–O1w and M–
O2w are nearly equal. Therefore, the coordination sphere
can be described as an octahedral. However, in the case of
the copper complex, the significant elongation of the Cu–
O2w bonds is observed (Table 7). This is consistent with
The hydrogen bond patterns for aforementioned pyrim-
idine-5-carboxylate complexes are marked in Fig. 6 for
structures containing cobalt, zinc and manganese cations
and in Fig. 7 for the structure of the copper cation sepa-
rately. There are four intermolecular hydrogen bonds in the
crystal packing of the Co, Zn and Mn pyrimidine-5-car-
…
boxylate complexes. Three of them are O–H O type and
…
one is O–H N type. In case of the Mn, Co and Zn com-
plexes, coordinated water molecules act as a proton donor,
while O1 (uncoordinated), O2 (uncoordinated) and N3
(uncoordinated) atoms play a role of the proton acceptors
in hydrogen bonding. However, due to the presence of an
additional water molecule in the crystal structure of the Cu
9
the Jahn–Teller effect (JTE) typical for d electron
configuration.
Fig. 4 The molecular structure
of the Mn(II), Co(II) and Zn
pyrimidine-5-carboxylates
complexes
O2w
N3
M: Mn, Co, Zn
C2
C4
N1
C5
C7
C6
O2
O2w
O1
123

´
G. Swiderski et al.
Fig. 5 The molecular structure
of the Cu(II) pyrimidine-5-
carboxylates complex. The
hydrogen bonds of (x, y,
z) symmetry are presented as a
dashed lines
O3w
O2w
N3
C2
C4
N1
C5
O2
C7
C6
O1w
O1
Table 7 Selected geometrical
parameters of manganese (II),
cobalt (II), zinc and copper (II)
pyrimidine-5-carboxylates
complexes
A˚ , °
Co
Zn
Mn
1.348(3)
Cu
N1–C2
1.344(3)
1.331(3)
1.346(4)
1.388(4)
1.389(3)
1.337(3)
1.511(3)
1.247(3)
1.259(3)
2.185(2)
2.055(1)
2.077(2)
1.343(2)
1.334(2)
1.345(2)
1.389(2)
1.386(2)
1.345(2)
1.513(2)
1.247(2)
1.264(2)
2.194(1)
2.079(5)
2.070(8)
1.338(3)
1.323(3)
1.334(3)
1.380(4)
1.389(3)
1.339(3)
1.509(3)
1.267(3)
1.230(3)
2.036(5)
2.000(8)
2.345(5)
125.8(2)
116.0(2)
123.2(2)
116.6(2)
120.8(2)
117.6(2)
118.2(2)
116.3(2)
88.1(9)
C2–N3
1.333(3)
1.342(3)
1.386(4)
1.387(3)
1.342(3)
1.512(3)
1.246(3)
1.262(3)
2.182(3)
2.076(6)
2.059(9)
N3–C4
C4–C5
C5–C6
C6–N1
C5–C7
C7–O1
C7–O2
M–N1
M–O1w
M–O2w
N1–C2–N3
C2–N3–C4
N3–C4–C5
C4–C5–C6
C5–C6–N1
C6–N1–C2
C5–C7–O1
C5–C7–O2
125.7(2)
125.6(1)
125.6(2)
116.7(2)
122.3(2)
116.3(2)
122.4(2)
116.7(2)
118.7(2)
116.2(2)
88.4(5)
116.6(1)
122.5(1)
116.2(1)
122.2(1)
116.8(1)
118.8(1)
115.9(1)
88.8(4)
116.7(2)
122.6(2)
116.3(2)
122.4(2)
116.5(2)
118.9(2)
116.1(2)
88.5(3)
O1 W–M–O2 W
O1 W–M–N1
O2 W–M–N2
89.2(7)
91.3(2)
91.1(5)
91.8(3)
88.90(8)
90.9(1)
90.8(6)
87.0(6)
pyrimidine-5-carboxylate complex, the hydrogen bonds
pattern differs. Six intermolecular hydrogen bonds of dif-
ferent symmetry codes can be observed here. Similarly to
the structures described above, the water molecules play a
role of the proton donors. However, all hydrogen bonds are
atoms of the uncoordinated water molecules. The uncoor-
dinated water molecule is a donor in a two additional
…
…
hydrogen bonds O3W–H3WA O2 and O3W–H3WB O1,
where O1 and O2 atoms are the oxygen atoms of different
molecules. Selected geometrical parameters of the hydro-
gen bonds together with the symmetry codes (symm. op. 2)
are presented in Table 8.
…
O–H O type only. The coordinated water molecules are
non-covalently bonded to a two O1 atoms of the two dif-
ferent ligand molecules and to a two different O3W oxygen
1
23

Thermal, spectroscopic, X-ray and theoretical studies of metal complexes…
Fig. 6 Crystal structure of the Mn(II), Co(II) and Zn pyrimidine-5-carboxylates complexes. Hydrogen bonds are presented as a dashed lines
Fig. 7 Crystal structure of the Cu(II) pyrimidine-5-carboxylates complex. Hydrogen bonds are presented as a dashed lines
Aromaticity
determined experimentally for the 3d metal complexes
with 5PCA acid. HOMA and I6 indexes for metal com-
plexes have lower values than for ligand. Complexing by
the metals (zinc, cobalt, copper, nickel and manganese)
causes a decrease in the aromaticity of the pyrimidine ring
(Table 9). Due to the lack of geometry data for 2PCA acid,
the effect of 3d metals on the aromatic system of this
The aromaticity indexes (Homa and I (Bird index) based
6
on the length of bonds in the aromatic ring allow to assess
the effect of the metal on the electronic system of the
molecule. The values of the indexes of aromaticity have
been calculated based on the values of the length of bonds
123

´
G. Swiderski et al.
Table 8 Geometrical parameters of the hydrogen bonds of manganese(II), cobalt(II), zinc and copper(II) pyrimidine-5-carboxylates complexes
˚
d(D–H)/A
˚
d(H–A)/A
˚
d(D–A)/A
˚
D–H–A/A
D
H
A
Symm. op. 2
Mn
Co
Zn
Cu
O1 W
O1 W
O2 W
O2 W
O1 W
O1 W
O2 W
O2 W
O1 W
O1 W
O2 W
O2 W
O1 W
O1 W
O2 W
O2 W
O3 W
O3 W
H1 WA
H1WB
H2 WA
H2WB
H1 WA
H1WB
H2 WA
H2WB
H1 WA
H1WB
H2 WA
H2WB
H1 WA
H1WB
H2 WA
H2WB
H3 WA
H3WB
N3
0.82(4)
0.92(4)
0.88(4)
0.96(4)
0.76(4)
0.96(5)
0.76(4)
0.84(5)
0.76(3)
0.79(3)
0.81(3)
0.87(3)
0.87
2.046
1.756
1.849
1.679
1.884
1.781
1.921
2.028
2.104
1.89
2.835(3)
2.670(2)
2.720(2)
2.642(2)
2.643(3)
2.725(2)
2.669(3)
2.832(3)
2.8409(18)
2.6720(16)
2.6496(16)
2.7242(16)
2.799(2)
2.837(3)
2.713(2)
2.724(2)
2.699(3)
2.835(3)
163(3)
172(4)
171(4)
177(4)
174(4)
169(6)
167(4)
160(5)
164(3)
172(3)
175(3)
172(3)
135.3
x, 1/2 - y, - 1/2 ? z
- x, - 1/2 ? y, 1/2 - z
- 1 - x, - 1/2 ? y, 1/2 - z
- 1 ? x, y, z
O2
O2
O1
O1
1 - x, - y, - z
O2
x, 1/2 - y, - 1/2 ? z
- 1 ? x, 1/2 - y, 1/2 ? z
- x, - 1/2 ? y, 1/2 - z
x, 1.5 - y, - 1/2 ? z
- x, - 1/2 ? y, 1/2 - z
- 1 ? x, y, z
O2
N3
N3
O2
O1
1.837
1.863
2.114
1.978
1.921
1.852
1.815
2.02
O2
1 - x, - 1/2 ? y, 1/2 - z
1 - x, - y, - z
O1
O3 W
O1
0.87
169.3
1 - x, - y, 1 – z
0.87
150.3
x, y, - 1 ? z
O3 W
O2
0.87
178.2
x, y, z
0.89(4)
0.81(5)
168(3)
176(4)
1 - x, - y, - z
O1
- x, - y, - z
ligand can not be assessed using aromaticity indices. A
comparison of the indexes for the complexes indicates that
the 2PCA cobalt and copper complexes have lower aro-
maticity than the metal complexes of 5PCA, while the zinc
complex shows higher aromaticity. The values of the aro-
matic indexes were also compared for the theoretically
modeled structures in B3LYP/LANL2DZ for pyrimidine-
SOD activity of copper complexes
SOD activity for the tested compounds was determined by
theoretical methods. It is known that Cu, Zn-SOD dismu-
tase and other compounds trap the superoxide anion in the
following reactions:
ÁÀ
E-CuðIIÞ þ O2 ! E-CuðIÞ þ O2
ð1Þ
ð2Þ
2
-carboxylic and pyrimidine-5-carboxylic acids and their
ÁÀ
þ
E-CuðIÞ þ O2 þ 2H ! E-CuðIIÞ þ H O
complexes with copper (Fig. 8). The data indicate that
copper may stabilize or destabilize the pyrimidine aromatic
system depending on the position of the carboxyl group in
the ring. In the case of 2PCA, index values indicated an
increase in aromaticity after complexing with copper,
while in the case of 5PCA, a decrease in the aromaticity
system was observed (Table 10).
2
2
As a theoretical parameter defining the radical scav-
enging activity by the studied complexes, the HOMO and
LUMO energy values and the EA electron affinity value
defined as TEE-Cu(I)–TEE-Cu(II) were selected in which
TE E-Cu(I) is the total energy of the complex E-Cu(I) and
TEE-Cu(II) with the total energy of the E-Cu(II) complex.
Table 9 Aromaticity (HOMA, EN, GEO and I
6
) of pyrimidine-2-carboxylates and pyrimidine-5-carboxylates (experimental structures)
Aromaticity
index
Pyrimidine-5-
carboxylic
Pyrimidine-5-carboxylate Pyrimidine-2-carboxylate
Manganese
complex
Cobalt
complex
Copper
complex
Zinc
complex
Nickel
complex [19]
Cobalt Copper
[18]
Zinc
complex
HOMA
GEO
EN
0.998
0.002
0.001
80.62
0.993
0.004
0.003
80.74
0.995
0.003
0.002
82.64
0.996
0.004
0.001
81.77
0.993
0.003
0.004
79.65
0.994
0.005
0.001
80.70
0.994
0.005
0.002
80.94
0.978
0.019
0.002
83.10
0.997
0.002
0.001
81.23
I
6
1
23

Thermal, spectroscopic, X-ray and theoretical studies of metal complexes…
Fig. 8 The coordination modes
of copper complexes with
pyrimidinecarboxylic acids
calculated in B3LYP/
LANL2DZ
Copper pyrimidine-2-carboxylate
Copper pyrimidine-5-carboxylate
6
Table 10 Aromaticity (HOMA, EN, GEO and I ) of copper pyrimidine-2-carboxylates and copper pyrimidine-5-carboxylates (calculated in
B3LYP/LANL2DZ)
Aromaticity index
Pyrimidine-2-carboxylic acid
Copper complex
Pyrimidine-5-carboxylic acid
Copper complex
HOMA
GEO
EN
0.936
0.002
0.062
80.32
0.940
0.005
0.055
82.15
0.915
0.005
0.079
83.68
0.912
0.010
0.077
77.29
I
6
The lower the EA value, the higher the electron transfer
rate. Electronic affinity (EA) is a good descriptor for
characterizing the superoxide radical scavenging activity
is the energy difference between HOMO and LUMO levels
[50].
The higher the HOMO level energy of the p-reductant
compounds, the more easily they can be oxidized, while the
p-deficits compounds they are easier to reduce the easier
the lower the energy has the LUMO orbital level.
From the HOMO and LUMO energy calculations for the
copper complexes of pyrimidinecarboxylic acids, it appears
that the 2PCA copper complex it is easier to reduce than
the 5PCA complexes. The hardness of the molecule can be
determined based on the HOMO and LUMO energy val-
ues. Absolute hardness is defined as follows: [51]:
[
48, 49].
The compounds with the lowest EA value have the
highest electron transfer capacity, thus giving the highest
SOD activity [49]. Calculations of energy values of
molecules and HOMO and LUMO molecular orbital have
been made for optimized structures of copper complexes
with diazines-derived acids. Geometric optimization was
performed using the B3LYP density functional method
using the LAN2LDZ calculation base.
Figure 9 presents HOMO and LUMO orbitals for copper
complexes with pyrimidinecarboxylic acids calculated in
B3LYP/LANL2DZ. In Table 11, the values of EA affinity
and HOMO and LUMO energy and other parameters
characterizing energy values are presented. For compar-
ison, literature data on the energy of the active center of
Cu, Zn-SOD enzyme were summarized [49]. EA calcula-
tions for copper complexes with diazines-derived acids
have shown that the highest SOD activity is exhibited by
the pyrimidine-5-carboxylic acid complex (it has the low-
g ¼ ðeLUMO À eHOMOÞ=2
The high value of absolute hardness g is a measure of
the thermodynamic stability of the system. The value of
chemical hardness for copper pyrimidine-5-carboxylate is
slightly lower than of copper pyrimidine-2-carboxylate.
IR and Raman spectra
The pyrimidine-2-carboxylic and pyrimidine-5-carboxylic
acids spectra include characteristic bands associated with
the oscillation of the carboxyl group and the vibration of
the C–N bonds of the aromatic ring. The position of these
bands in the spectrum of acid depends on the relative
position of the carboxyl group and the nitrogen atoms in
the aromatic ring. The bands derived from the vibrational
stretching mC=O in the infrared spectrum of pyrimidine-2-
-
1
est EA energy value of - 108,875 kcal mol ), while the
pyrimidine-2-carboxylic acid complex has the lowest
-
1
activity - 100,021 kcal mol . On the basis of the calcu-
lated values of EA energy and comparison with the value
of this energy for the active center of the enzyme dismu-
tase, it can be concluded that copper complexes with
pyrimidine-derived acids behave like superoxide dismutase
mimetics. One of the stability criteria for aromatic systems
-
1
-1
carboxylic acid are located at 1743 cm (1738 cm in
123

´
G. Swiderski et al.
Fig. 9 HOMO and LUMO
orbitals for copper complexes
with pyrimidinecarboxylic acids
calculated in B3LYP/
(
a)
LANL2DZ (a: copper
pyrimidine-2-carboxylate, b:
copper pyrimidine-5-
carboxylate)
ELUMO = – 5.21 eV
ΔEHOMO/LUMO = 0.07 eV
EHOMO = – 5.14 eV
(
b)
ELUMO = – 5.14 eV
ΔEHOMO/LUMO = 0.06 eV
EHOMO = – 5.08 eV
Table 11 Geometrical parameters calculated in B3LYP/LANL2DZ
Copper pyrimidine-2-carboxylate
Copper pyrimidine-5-carboxylate
Dipole moment (D)
TECu(II) (hartree)
TECu(I) (hartree)
0.00003
- 1100.6524
- 1100.8118
- 100.021
- 0.19142
- 0.18883
- 5.21
0.0013
- 1100.5447
- 1100.7182
- 108.875
- 0.18880
- 0.18662
- 5.14
-1
)
EA (kcal mol
HOMO (Hartree)
LUMO (Hartree)
HOMO (eV)
LUMO (eV)
- 5.14
- 5.08
Energy gap
0.07
0.06
Ionization potential. I = - EHOMO
Electron Affinity. A = - ELUMO
5.21
5.14
5.14
5.08
IþA
Electronegativity. v ¼
5.18
5.11
2
IþA
Chemical potential. l ¼ À 2
- 5.18
0.035
- 5.11
0.030
IÀA
Chemical hardness. g ¼
2
1
Chemical softness. S ¼ 2g
14.29
16.67
2
l
383.32
435.20
Electrophilicity index. x ¼ 2g
-
1
-1
the IR spectrum of ATR) and 1719 cm and at 1721 cm
in the Raman spectrum (Table 12).
positions (Table 13). The close vicinity of the nitrogen
atoms of the aromatic ring causes the vibrational numbers
of the pyrimidine-2-carboxylic acid carboxyl group to have
a higher value than in the pyrimidine-5-carboxylic acid
spectrum. In the pyrimidine-5-carboxylic acid spectrum,
the band is located at a lower wavenumber. Similar
dependencies were noted by comparing the spectra of
In the case of pyrimidine-5-carboxylic acid, the band is
-
1
located at 1714 cm
-
in the IR spectrum of KBr,
-1
1
1
704 cm
IR ATR and at 1708 cm
in the Raman
spectrum. In the spectra of both acids, the bands originating
from the vibrations of the carboxylic group have different
1
23

Thermal, spectroscopic, X-ray and theoretical studies of metal complexes…
123

´
G. Swiderski et al.
pyridinecarboxylic acids (picolinic, nicotinic and isonico-
tinic acid) [52]. In the analyzed spectra, differences in the
position of bands associated with the vibration of the aro-
matic system in both acids were observed. Spectral
assignments used the normal oscillation of the pyrimidine
ring (Fig. 10) measured using B3LYP/6-311??G(d,p).
For example, the band denoted no. 5 is located at
-
1
1
576 cm in the pyrimidine-2-carboxylic acid IR spec-
-
1
trum and at 1593 cm in the pyrimidine-5-carboxylic acid
spectrum.
Also bands 7 and 8 are located at higher values of wave
numbers for 5PCA acid than in the 2PCA spectrum
-
1484 cm , 1439 cm
1
-1
-1 -1
and 1442 cm , 1408 cm ,
(
respectively). In the case of other bands, e.g., 12, 13, 17,
there are also significant differences in the position of the
bands for each acid. Some of the bands are observed in the
pyrimidine-2-carboxylic acid spectrum (e.g., band 14), and
they are absent in the pyrimidine-5-carboxylic acid spec-
trum. Some of the bands are observed in the pyrimidine-5-
carboxylic acid spectrum (e.g., 10, 15 bands), but they are
absent in the pyrimidine-2-carboxylic acid spectrum.
The vibrations of the carboxylate anion are present in
the spectra of the pyrimidinecarboxylic acids metal com-
plexes (Figs. 11 and 12). The analysis of position of the
asymmetric and symmetrical stretching bands of the car-
boxylate anion in comparison with position of the bands of
carboxylate anion of the sodium salt allows the determi-
nation of the metal–ligand coordination mode. Table 14
contains the values of wave numbers of the carboxylate
anion vibrations for the 2PCA acid complexes as well as
differences in the values of these vibrations. According to
Nakamoto, this allows the assessment of the metal–ligand
coordination mode [53]. In the case of complexes (Mn, Co,
Cu, Zn) of pyrimidine-2-carboxylic acid, the difference in
wavenumbers of tensile vibrations of asymmetric and
-
asymmetric carboxylate anions (Dm = m COO - m
as
sym
-
COO ) for 3d metal complexes of 2PCA acid is higher
than for sodium salts indicates a monodent mode of metal–
ligand coordination by a carboxyl group, which agrees with
the X-ray diffraction results for single crystals. Additional
metal–ligand binding takes place via the nitrogen atom of
the pyrimidine ring, which is observed in changes in the
infrared spectra (the disappearance of the tensile bands
mCN in the spectra of the complexes).
In the case of the nickel complex, the difference Dm in
the spectrum is smaller than in the sodium salt, which
suggests a bidentate chelation coordination mode. The
mode of metal–ligand coordination by the nitrogen atom
without the participation of a carboxylic group is more
likely due to the characteristic changes in the bands orig-
inating from vibrations of the aromatic system (disap-
pearance of bands in the nickel complex) and the
appearance of an unbound carboxylate anion with aligned
1
23

Thermal, spectroscopic, X-ray and theoretical studies of metal complexes…
123

´
G. Swiderski et al.
electronic charge on the oxygen atoms in the carboxyl
group).
Under the influence of complexing in the acids spectra,
changes in the position of many bands are observed, as well
as the disappearance or appearance of some bands in
complexes with respect to the ligand. Comparative analysis
of the position of bands in the spectra of the acid and its
complexes allows to assess the influence of the metal on
the distribution of the electron charge of the ligand. Our
research so far has shown that alkali metals cause disorder
of the ligand’s aromatic system, while transition metals
stabilize the ligand’s electronic system [54]. If in the IR
and Raman spectra, we observe a decrease in the number,
wavenumber and/or intensities of the bands for metal
complexes in comparison with the appropriate bands in the
spectra of ligands and there is a disorder of the aromatic
system. It is caused by a decrease in the force constants of
the bonds and polarization of the C–C, C–N bonds in the
ring [54]. By comparing the spectra of sodium salts and
pyrimidine-2-carboxylic acid and pyrimidine-5-carboxylic
acid, it was observed that sodium causes disorder in the
aromatic system in each of the ligands. In the sodium
pyrimidine-2-carboxylate spectra, it was observed that for
many bands originating from vibrations of the aromatic
system and the wavenumber (3, 4, 5, 6, 13) are reduced.
Many of the bands present in the ligand spectrum disappear
in the spectrum of sodium salt (8, 12, 14, 17, 18, 20, 22).
Some of the bands do not change (7, 9, 10, 16), and only
for some bands, the wavenumbers increase in the spectrum
of the sodium salt with respect to the ligand (11, 21, 23).
Similar observations have been made for 5PCA acid and its
sodium salt.
In the spectrum of sodium salt, a number of bands
present in the spectrum of acid disappear. These are bands
marked with 4, 5, 7, 8, 9, 11, 12, 17, 18, 21). Some of the
bands are shifted toward the lower values of wave numbers
in the spectrum of sodium salt (13, 22). An increase in the
value of wave numbers for vibration bands (6, 10, 19, 23)
in the spectrum of sodium salt with respect to the spectrum
of the acid was also observed. The analysis showed that the
atom of the lithium destabilizes the pyrimidine-5-car-
boxylic acid electron system to a greater extent than the
pyrimidine-2-carboxylic acid.
The position of heteroatoms relative to the carboxyl
group is important here. Similarly, it was observed in the
case of the influence of alkaline metals on the electronic
system of pyridinecarboxylic acids [55]. Transition metals,
as shown in previous studies, stabilize the ligand electron
system. In the IR and Raman spectra, this is observed in the
form of an increase in wave numbers of bands originating
from vibrations of the aromatic system of complexes with
respect to the ligand. In the spectra of transition metal of
pyrimidine-2-carboxylic acid complexes, an increase in
1
23

Thermal, spectroscopic, X-ray and theoretical studies of metal complexes…
wave numbers of many bands originating from the vibra-
tions of the aromatic system was observed (5, 7, 8, 11, 13,
transition 3d metals have a greater impact on the 2PCA
acid aromatics system than 5PCA acid. In the case of
2PCA, the transition metals attached via the carboxyl group
and the nitrogen atom of the aromatic ring stabilize the
electron system, whereas in the case of pyrimidine-5-car-
boxylic acid complexes, a disorder of the aromatic ligand
system is observed. Direct attachment of the metal to the
aromatic pyrimidine ring causes an increase in the distur-
bance of the aromatic system.
2
0, 21). There are also vibration-derived bands that were
absent in the spectrum of the ligand (e.g., band No. 15). For
some of the bands, decreasing of the wavenumber value in
the complex spectrum with respect to the ligand or disap-
pearance of the bands (6, 9, 12, 16) was observed. This
indicates an increase in the aromaticity of the 2PCA acid
system under the influence of complexation. In the spectra
of pyrimidine-5-carboxylic acid metal complexes, greater
changes were observed with respect to the ligand than in
the spectra of the pyrimidine-5-carboxylic acid complexes.
Decreased values of wave numbers or disappearance of
bands derived from vibrations of the pyrimidine carboxylic
acid ring were observed. These are bands marked with 5, 6,
Thermal analysis
Different methods of thermal analysis (TG–DSC, TG–
FTIR) were used to determine thermal behavior of two
series of metal(II) complexes during heating in air and
nitrogen atmospheres. Thermal analysis methods allow to
demonstrate that the same metal ions with the isomers of
pyrimidinecarboxylic acid give complexes with a different
number of solvent molecules. The pyrimidine-2-carboxy-
late complexes contain in the structure a smaller number of
water molecules compared to the corresponding complexes
with pyrimidine-5-carboxylic acid.
7
, 8, 9, 12, 13, 14. An increase in wavenumbers was
observed only for some bands (10, 11, 15). A comparative
analysis of the spectra of pyrimidine carboxylate com-
plexes and pyrimidinecarboxylic acids has shown that
Thermal decomposition of the investigated complexes in
air atmosphere proceeds in two main stages connected with
dehydration
Tables 15, 16, Figs. 13–17).
Manganese(II) pyrimidine-2-carboxylate (MnL ) as an
and decomposition/burning
processes
1
2
6
3
4
(
1
anhydrous complex exhibits high thermal stability up to
about 250 °C, while manganese(II) pyrimidine-5-car-
boxylate tetrahydrate (MnL Á4H O) is stable to 110 °C
2
2
5
7
8
(Fig. 13). Further heating leads to the one-stage removal of
all four water molecules associated with 18.85% mass loss
in the temperature range 110–140 °C accompanied by a
strong endothermic effect at 122 °C observed on the DSC
curve. The corresponding molar enthalpy of dehydration
-
1
process is equal to 153.5 kJ mol . An anhydrous form of
manganese(II) pyrimidine-5-carboxylate is thermally
stable up to about 350 °C. Further heating of both man-
ganese(II) complexes results in distinct mass losses
observed on the TG curves connected with one-stage
decomposition and combustion of organic ligands. Very
strong exothermic effects appear on the DSC curves.
Manganese(III) oxide is the final decomposition product
formed at about 470–480 °C. During heating up to about
9
10
11
12
13
14
15
19
16
9
40 °C, Mn O transforms into Mn O [56, 57].
2
3
3 4
17
18
20
The first mass losses on the TG curves of cobalt com-
plexes CoL Á2H O and CoL Á4H O are a result of the
1
2
2
2
dehydration process (Fig. 14). The release of water mole-
cules in the CoL Á2H O complex takes place in the tem-
1
2
perature range 150–220 °C. The other complex is less
stable, and loss of solvent molecules is observed at lower
temperature 123–205 °C. The shapes of the DSC curves of
both complexes CoL Á2H O and CoL Á4H O indicate that
2
1
22
23
24
Fig. 10 Normal modes of pyrimidine ring calculated in DFT/B3LYP/
-311??(d,p)
6
1
2
2
2
123

´
G. Swiderski et al.
Fig. 11 IR spectra of
pyrimidine-2-carboxylates in
the range from 500 to
2
-
1
βOH
000 cm (from above:
pyrimidine-2-carboxylic acid,
sodium complex, manganese(II)
complex, cobalt(II) complex,
nickel(II) complex, copper(II)
complex and zinc complex)
νC=O
νCNar
νCCar
βOH
βsymCOO–
νCNar
νCCar
νasCOO–
νsymCOO–
βasCOO–
βsymCOO–
νasCOO–
νsymCOO–
νCNar
νCCar
βasCOO–
βsymCOO–
νsymCOO–
νasCOO–
νCNar
νCCar
βsymCOO–
νasCOO–
νsymCOO–
νCNar
νCCar
βasCOO–
νCNar
βsymCOO–
νsymCOO–
νasCOO–
νCCar
βsymCOO–
νCNar
νCCar
νsymCOO–
νasCOO–
βCH,νCN,νCN
γCH, βring
2
000
1500
1000
500
Wavenumbers/cm–1
removal of water molecules occurs in overlapping stages
with the overall molar dehydration enthalpy values of
carboxylate dihydrate, the removal of both water molecules
occurs in the temperature range 164–258 °C. The first mass
loss connected with the dehydration process is 11.58%
(calc. 10.57%). As can be deduced from the shape of the
DSC curve, this process probably proceeds in two stages
(temperatures of the endothermic peaks are 201 °C and
-
1
-1
and 177.9 kJ mol , respectively. The
7
8.0 kJ mol
anhydrous complexes CoL and CoL are stable in the
1
2
narrow temperature ranges 220–307 and 205–260 °C,
respectively. At a higher temperature, two mass losses
appear on the TG curves as a result of the decomposition
and burning of the anhydrous form of complexes. These
stages are accompanied by very strong exothermic effects.
As the final solid product of thermal decomposition, Co O
-
1
229 °C) with the overall enthalpy of 83.6 kJ mol
.
Nickel(II) pyrimidine-5-carboxylate tetrahydrate loses all
water molecules in one stage in the temperature range
132–208 °C with the corresponding molar dehydration
3
4
-
1
is formed. Further heating of such compound leads to the
transformation into the CoO at about 940 °C [58, 59].
The nickel complexes NiL Á2H O and NiL Á4H O
enthalpy value of 192.3 kJ mol (the maximum of the
endothermic peak at 200 °C). Anhydrous compounds are
stable in narrow temperature ranges and heating leads to
the two-stage decomposition connected with burning of the
organic ligand. Very strong exothermic effects can be
1
2
2
2
exhibit thermal stability up to 164 and 132 °C, respectively
(
Fig. 15). During heating of nickel(II) pyrimidine-2-
1
23

Thermal, spectroscopic, X-ray and theoretical studies of metal complexes…
Fig. 12 IR spectra of
pyrimidine-5-carboxylates in
the range from 500 to
2
-
1
000 cm (from above:
νCNar
βOH
pyrimidine-5-carboxylic acid,
sodium complex, manganese(II)
complex, cobalt(II) complex,
nickel(II) complex, copper(II)
complex and zinc complex)
νCCar
νC=O
νCNar
νCCar
βsymCOO–
βasCOO–
νCNar
νCCar
νasCOO–
νsymCOO–
βsymCOO–
βasCOO–
νasCOO–
νsymCOO–
βsymCOO–
βasCOO–
νasCOO–
νsymCOO–
βsymCOO–
βasCOO–
νasCOO–
νsymCOO–
βsymCOO–
νCNar
νCCar
βasCOO–
νasCOO–
νsymCOO–
βsymCOO–
βasCOO–
νasCOO–
νsymCOO–
βCH,νCN,νCN
1000
γCH, βring
2000
1500
500
Wavenumbers/cm–1
Table 14 Spectral parameters (vibrations stretching the carboxylate anion) from the IR spectra of pyrimidine-2-carboxylates and proposed type
of coordination the metal to carboxylic group of the ligand
-
-
a
Compound
m
asym (COO )
m
sym (COO )
Wavenumber/cm
Dm
Wavenumber/cm
Proposed coordination
-
1
-1
-1
Wavenumber/cm
Sodium salt
1639
1626
1668
1637
1653
1664
-
1379
1311
1357
1391
1351
1358
260
315
311
246
302
306
Manganese complex
Cobalt complex
Nickel complex
Copper complex
Zinc complex
Monodentate
Monodentate
Bidentate chelation
Monodentate
Monodentate
a
-
Dm = masym(COO ) - msym(COO )
123

´
G. Swiderski et al.
observed on the DSC curves. Nickel(II) oxide is formed at
about 480 °C as the final solid product of thermal
decomposition nickel complexes [60].
relatively wide temperature ranges: 190–370 °C and
152–316 °C. Similarly to the above-described compounds,
further heating leads to the two-stage decomposition
resulting from degradation and burning of anhydrous form
of complex. Zinc oxide is formed as a final solid product of
complexes decomposition [58, 60].
The copper(II) compound with pyrimidine-2-carboxylic
acid as a anhydrous complex displays great thermal sta-
bility. Two-stage decomposition occurs in the temperature
range of 260–390 °C. As the final solid product of
decomposition, copper(II) oxide is formed. Copper(II)
pyrimidine-5-carboxylate hexahydrate is stable to 80 °C.
During further heating, the dehydration process occurs in
two hardly separated stages. Mass losses of 24.30% and 2%
observed on the TG curve are associated with the removal
of 5.5 and 0.5 water molecules. The first stage of dehy-
dration is accompanied by a very strong endothermic effect
with the molar enthalpy of dehydration equal to
TG–FTIR analysis
Volatile products of thermal decomposition of the CoL1-
2H O and CoL Á4H O complexes were investigated by the
2
2
2
coupled TG–FTIR method as representatives of two series
of investigated complexes. The infrared spectra of gaseous
products released during complexes heating in nitrogen
atmosphere are given in Fig. 18. The CoL Á2H O complex
1
2
-
1
2
9
1
2
00.7 kJ mol
(temperature of the peak maximum is
is stable in the nitrogen temperature to 178 °C. Next, in the
temperature range 180–240 °C, water molecules are
evolved. The FTIR spectra exhibit characteristic bands in
5.6 °C). The other endothermic effect was recorded at
50 °C. The dehydrated form of complex is stable to
45 °C. Next, the two-step decomposition takes place in
-
1
the
wavenumber
-
ranges
4000–3400 cm
and
1
the range 286–384 °C (Fig. 16). Also, CuO is formed as
stable solid residue [58, 61].
1800–1200 cm
corresponding to the stretching and
deformation vibrations of water molecules [57]. As shown
in Fig. 18, the dehydrated form of the complex is stable up
to 330 °C. At higher temperature, carbon dioxide mole-
cules are released. The FTIR spectra show very diagnostic
The zinc complexes ZnL Á2H O and ZnL Á4H O are
1
2
2
2
thermally stable up to 110 and 98 °C, respectively
(
Fig. 17). At higher temperature, mass losses on the TG
-
1
curves are observed due to the dehydration process. As can
be concluded from the TG and DSC curves of the ZnL1-
characteristic bands in the region 2359–2310 cm and
-
1
that at 669 cm derived from the stretching and defor-
mation vibrations of carbon dioxide (Fig. 18). Above
450 °C besides the bands from the carbon dioxide mole-
cules, also a double band with the maxima at 2182 and
2
H O complex, release of water molecules takes place in
2
two hardly distinguishable stages. The mass loss of 10.97%
is observed in the temperature range 110–190 °C. The
dehydration process proceeds with the two overlapping
endothermic effects with the maxima at 144 °C and 156 °C
-
1
2094 cm is observed due to evolved carbon monoxide
[62]. Moreover, along with carbon oxides weak bands
derived from the ammonia and pyrimidine molecules are
observed. These gases give the most intense bands at
440–500 °C. Identification of pyrimidine molecules can be
-
1
and total molar dehydration enthalpy of 83.6 kJ mol . In
the other zinc complex, four water molecules are released
in one stage in the narrow temperature range 110–140 °C.
This process is accompanied by a very strong endothermic
-
1
made based on the bands in the region 3100–3000 cm
effect
74.8 kJ mol . The dehydration process resulted in the
formation of anhydrous compounds which are stable in the
with
the
molar
dehydration
enthalpy
which can be assigned to the stretching vibrations of CH
-1
-
1
1
groups. The bands recorded at 1569, 1540 cm and those
1
-
at 1436, 1339 cm
can be ascribed to the stretching
Table 15 Results of thermal decomposition of Ni(II), Co(II), Cu(II), Zn(II) and Mn(II) complexes with pyrimidine-2-carboxylic acid in air
-
1
Complex
DT
1
/°C
DH/kJ mol (Tpeak/°C)
Mass loss/%
DT
2
/°C
Mass loss/%
Residue
Found
Calc.
Found
Calc.
Co(2PCA)
2
Á2H
Á2H
Á2H
2
O
150–220
164–258
110–190
–
78.0 (183, 198)
12.39
11.58
10.97
–
10.55
10.57
10.36
–
307–480*
320–480
370–530
250–489**
260–390
78.60
78.72
77.67
74.15
74.57
77.07
78.08
76.56
73.78
74.30
3 4
Co O
Ni(2PCA)
2
2
O
83.6 (201, 229) (201, 229)
83.6 (144, 156)
NiO
ZnO
Zn(2PCA)
2
2
O
Mn(2PCA)
2
Mn
2
O
3
Cu(2PCA)
2
–
–
–
CuO
2
PCA—C
5
H
3
N
2
O
2
(pyrimidine-2-carboxylate); DT
1
—temperature range of dehydration; DT
2
—temperature range of degradation of anhydrous
oxide
complex to suitable oxide; *—further transformation of Co
into Mn oxide is observed
3
O
4
oxide into CoO oxide is observed; **—further transformation of Mn O
2 3
3 4
O
1
23

Thermal, spectroscopic, X-ray and theoretical studies of metal complexes…
Table 16 Results of thermal decomposition of Ni(II), Co(II), Cu(II), Zn(II) and Mn(II) complexes with pyrimidine-5-carboxylic acid in air
-
1
Complex
1
DT /°C
(DH/kJ mol (Tpeak/°C)
Mass loss/%
2
DT /°C
Mass loss/%
Residue
Found
Calc.
Found
Calc.
Co(5PCA)
2
Á4H
Á4H
Á4H
Á4H
Á6H
2
O
123–205
132–208
98–152
177.9 (183)
192.3 (200)
174.8 (133)
153.5 (122)
200.7 (95.6)
19.95
20.30
19.23
19.85
26.13
19.10
19.11
18.78
260–449*
300–480
316–572
350–470**
245–384
79.73
79.96
82.09
80.75
82.95
78.71
80.17
78.76
78.84
80.94
3 4
Co O
Ni(5PCA)
2
2
O
NiO
ZnO
Zn(5PCA)
2
2
O
Mn(5PCA)
2
2
O
110–140
80–167
19,29
25.86
Mn
2
O
3
Cu(5PCA)
2
2
O
CuO
5
PCA—C
5
H
N O
3 2 2
1 2
(pyrimidine-5-carboxylate); DT —temperature range of dehydration; DT —temperature range of degradation of anhydrous
complex to suitable oxide; *—further transformation of Co
into Mn oxide is observed
3
O
4
2 3
oxide into CoO oxide is observed; **—further transformation of Mn O oxide
3 4
O
(
a)
(b)
40
30
TG
40
0
0
EXO
35
EXO
TG
3
2
2
1
0
5
0
5
–
20
– 20
– 40
– 60
20
–
–
40
60
10
0
DSC
10
5
DSC
– 10
– 20
–
80
0
– 80
–
5
1
00 200 300 400 500 600 700 800 900 1000
100 200 300 400 500 600 700 800 900 1000
Temperature/°C
Temperature/°C
Fig. 13 TG and DSC curves of manganese(II) complexes with: a pyrimidine-2-carboxylic acid; b pyrimidine-5-carboxylic acid
(
a)
0
(
b)
4
0
TG
3
5
0
EXO
35
EXO
30
25
3
0
TG
–
20
–
20
40
60
80
2
5
2
0
20
15
10
–
–
40
60
–
–
–
15
1
5
0
–
0
5
0
DSC
DSC
–
80
5
–
5
1
00 200 300 400 500 600 700 800 900 1000
1
00 200 300 400 500 600 700 800 900 1000
Temperature/°C
Temperature/°C
Fig. 14 TG and DSC curves of cobalt(II) complexes with: a pyrimidine-2-carboxylic acid; b pyrimidine-5-carboxylic acid
vibrations of aromatic ring m(CC) and m(NC) and defor-
mation vibrations of CH moieties [63]. Ammonia mole-
cules were detected among the gaseous products of
complex thermal decomposition due to the presence of
At higher temperature, only carbon oxides and traces of
water are evolved.
Cobalt(II) pyrimidine-5-carboxylate tetrahydrate is
stable in the inert atmosphere to 127 °C. Next, the dehy-
dration process occurs with water molecules evolution in
-
1
very diagnostic double peak bands at 967 and 933 cm
.
123

´
G. Swiderski et al.
(
a)
(b)
4
0
40
0
0
EXO
TG
EXO
3
2
0
0
TG
30
–
–
20
– 20
20
40
60
80
–
40
1
0
–
0
10
0
–
–
– 60
DSC
DSC
–
80
10
– 10
1
00 200 300 400 500 600 700 800 900 1000
100
200 300 400 500 600 700 800 900 1000
Temperature/°C
Temperature/°C
Fig. 15 TG and DSC curves of nickel(II) complexes with: a pyrimidine-2-carboxylic acid; b pyrimidine-5-carboxylic acid
(
a)
0
(
b)
TG
25
0
15
10
5
EXO
EXO
2
0
–
–
–
–
20
40
60
80
TG
–
–
–
–
20
40
60
80
1
5
DSC
1
5
0
0
– 5
DSC
0
–
100
– 10
1
00
200
300
400
500
600
700
100 200 300 400
500 600 700 800 900 1000
Temperature/°C
Temperature/°C
Fig. 16 TG and DSC curves of copper(II) complexes with: a pyrimidine-2-carboxylic acid; b pyrimidine-5-carboxylic acid
(
a)
(
b)
15
0
0
20
40
EXO
TG
3
0
10
–
–
1
2
TG
–
–
20
5
0
DSC
–
–
–
3
4
5
1
0
– 60
DSC
0
–
–
5
–
80
–
6
– 10
10
1
00 200 300 400 500 600 700 800 900 1000
100 200
300 400 500
600 700 800 900 1000
Temperature/°C
Temperature/°C
Fig. 17 TG and DSC curves of zinc(II) complexes with: a pyrimidine-2-carboxylic acid; b pyrimidine-5-carboxylic acid
the range 130–210 °C. The FTIR spectra exhibit diagnostic
bands derived from the stretching and deformation vibra-
tions of water (Fig. 18). The anhydrous compound is
stable to 310 °C. Further heating leads to the degradation
of the pyrimidine-5-carboxylate ligand with the evolution
of carbon dioxide, ammonia and pyrimidine molecules at
1
23

Thermal, spectroscopic, X-ray and theoretical studies of metal complexes…
(a)
(b)
0.40
0
0
.30
0.50
.20
0.10
0
.00
30.0
5.0
–
0.00
4000
500
4
000
3
0.0
2
3
500
3
25.0
20.0
5.0
3
000
20.0
15.0
0.0
3
000
2
2
500
500
1
2000
2000
1
1
0.0
1500
1500
5.0
5.0
1000
1000
Fig. 18 FTIR spectra of gaseous products evolved during the decomposition of: a Co(2PCA)
2
Á2.5H
2
O; b Co(5PCA)
2
Á4H
2
O
the same time. Compared with the previously described
thermal decomposition of cobalt(II) pyrimidine-2-car-
boxylate, the bands derived from the pyrimidine molecules
are more intense. In the wavenumber region
relation to positions of the heteroatoms in the aromatic
rings of acids. In the case of metal complexes with
pyrimidine-2-carboxylic acid, the metal ions are linked
to the ligand via the monodentate carboxylate group
and the nitrogen atom of the aromatic ring. In the case
of metal complexes with pyrimidine-5-carboxylic acid,
the metal ions are only attached to the ligand via the
nitrogen atom. These conclusions were confirmed by
single-crystal X-ray diffraction method as well as
spectroscopic (IR, Raman) investigations.
-
1
3
100–3000 cm , there can be distinguished three peaks at
-
086, 3055 and 3040 cm from the stretching vibrations
1
3
of CH. In the lower wavenumber region, there are observed
several double bands with the maxima at: 1574,
-
1
-1
-1
507 cm ; 1436, 1387 cm ; 1230, 1209 cm and 1151,
1
1
-
140 cm assigned to the stretching and different modes
1
of deformation vibrations of CC, CN and CH moieties [63].
2. Water molecules in hydrated form of complexes play
role of monodentate ligands. Only in copper(II)
pyrimidine-5-carboxylate, two additional water mole-
cules are in inner coordination sphere.
Carbon monoxide is evolved above 600 °C.
Conclusions
3. The analysis of spectroscopic data (IR, Raman) and
theoretical calculations (aromaticity indexes) showed
that transition 3d metals cause changes in the elec-
tronic charge distribution of the ligands. This effect is
the greatest for the pyrimidine-5-carboxylates in where
the metal ions are coordinated directly to the aromatic
ring (by nitrogen atom). The metals can stabilize the
electron system of pyrimidine-2-carboxylate ligand,
while in the case of pyrimidine-5-carboxylate ligand
decrease in aromaticity is observed.
Two series of novel metal(II) complexes with pyrimidine-
2
-carboxylic and pyrimidine-5-carboxylic acid were
obtained and characterized. The work allowed to assess the
influence of selected metals on the electronic structure and
antioxidant properties of the pyrimidinecarboxylic acids.
The influence of metals on the above properties was
evaluated depending on the location of the carboxyl group
relative to the heteroatoms in the aromatic ring. As a result
of synthesis, some complexes were obtained in a crystalline
form, which allowed for precise determination of the
structure using X-ray diffraction. In addition, theoretical
calculations of some structures were made, which allowed
for a broader interpretation of the obtained results. Two
ligands (pyrimidine-2-carboxylic acid and pyrimidine-5-
carboxylic acid) were selected for the experimental tests.
Taking into account obtained results several conclusions
can be drawn:
4. Theoretical calculations (the SOD activity) have shown
that the copper complex of pyrimidine-2-carboxylic
acid has lower antioxidant activity than the copper
complexes of pyrimidine-5-carboxylic acids.
5. The metal coordination mode also affects the thermal
stability of the studied complexes. Thermal analysis
has shown that the metal complexes with pyrimidine-2-
carboxylic acid (with the exception of the manganese
complex) exhibit a higher thermal stability compared
to the metal pyrimidine-5-carboxylates. The final
products of thermal degradation in the air atmosphere
of studied complexes are suitable metal oxides. The
1
.
The metal–ligand coordination mode in complexes
depends on the position of the carboxylic group in
123

´
G. Swiderski et al.
1 13
FT-IR, FT-Raman, H and C NMR and thermogravimetric
studies. Spectrochim Acta, Part A. 2013;103:264–71.
´
2. Swiderski G, Kalinowska M, Rusinek I, Samsonowicz M,
research shows that complexes of transition metals
with pyrimidine carboxylic acids are more thermally
stable when the metal is coordinated through the
carboxyl group and the nitrogen atom of the pyrimidine
ring than complexes in which the metal is coordinated
only through the nitrogen atom of the pyrimidine ring.
Investigated metal complexes decompose in nitrogen
atmosphere with releasing of water, carbon oxides,
ammonia and pyrimidine molecules.
1
Rz a˛ czy n´ ska Z, Lewandowski W. Spectroscopic (IR, Raman) and
thermogravimetric studies of 3d-metal cinchomeronates and
dinicotinates. J Therm Anal Calorim. 2016;126(3):1521–32.
´
1
3. Kalinowska M, Borawska M, Swisłocka R, Piekut J, Lewan-
1
13
dowski W. Spectroscopic (IR, Raman, UV, H and C NMR)
and microbiological studies of Fe(III), Ni(II), Cu(II), Zn(II) and
6
.
Ag(I) picolinates. J Mol Struct. 2007;834:419–25.
´
14. Kalinowska M, Swisłocka R, Lewandowski W. Zn(II), Cd(II) and
13
1
Hg(I) complexes of cinnamic acid: FT-IR, FT-Raman, H and
NMR studies. J Mol Struct. 2011;993(1–3):404–9.
C
´
´
Acknowledgements The studies have been carried out in the frame-
15. Swiderski G, Lewandowska H, Swisłocka R, Wojtulewski S,
Siergiejczyk L, Wilczewska A. Thermal, spectroscopic (IR,
Raman, NMR) and theoretical (DFT) studies of alkali metal
complexes with pyrazinecarboxylate and 2,3-pyrazinedicarboxy-
late ligands. J Therm Anal Calorim. 2016;126(1):205–24.
´
work of the Project No. S/WBiIS/3/2017 and financed from the funds
for science Ministry of Science and Higher Education.
Open Access This article is distributed under the terms of the Creative
Commons Attribution 4.0 International License (http://creative
commons.org/licenses/by/4.0/), which permits unrestricted use, dis-
tribution, 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.
´
16. Swiderski G, Kalinowska M, Malejko J, Lewandowski W.
Spectroscopic (IR, Raman, UV and fluorescence) study on lan-
thanide complexes of picolinic acid. Vib Spectrosc.
2016;87:81–7.
17. Xu DJ, Zhang BY, Yang Q, Nie JJ. Diaqua-bis(pyrimidine-2-
carboxylic acid- j2 N, O)cobalt(II) dichloride. Acta Crystallogr
Sect E. 2008;64:m77.
1
8. Zhang BY, Yang Q, Nie JJ. Bis(pyrimidine-2-carboxyl-ato-j2 N,
O)copper(II). Acta Crystallogr Sect E. 2008;64:m7.
References
1
9. Aekeroy CB, Desper J, Levin B, Valdez-Martines J. Robust
building blocks for inorganic crystal engineering. Inorg Chim
Acta. 2006;359:1255–62.
0. Orjiekwe CL, Fabiyi FA, Edward DA. Synthesis and character-
ization of new picolinate metal complexes. Synth React Inorg,
Met-Org, Nano-Met Chem. 2005;35(9):695–702.
1. Okabe N, Koizumi M. Diaquabis (2-pyridinecarboxylato-N, O)
manganese(II). Acta Crystallogr Sect C. 1998;54(3):288–90.
2. Nie FM, Fang T, Wang SY, Ge HY. Synthesis and structures of
pyridinecarboxylate-containing zinc(II) complexes in dien and
tren system. Inorg Chim Acta. 2011;365(1):325–32.
3. Waizumi K, Takuno M, Fukushima N, Masuda H. Structures of
pyridine carboxylate complexes of cobalt(II) and copper(II).
J Coord Chem. 1998;44:269–79.
1
. Holm RH, Kennepohl P, Solomon EI. Structural and functional
aspects of metal sites in biology. Chem Rev.
2
1
996;96(7):2239–314.
2
3
. Salvemini D, Riley DP, Cuzzocrea S. SOD mimetics are coming
of age. Nat Rev Drug Discov. 2002;1(5):367–74.
. Siddiqi ZA, Khalid M, Kumar S, Shahid M, Noor S. Antimi-
crobial and SOD activities of novel transition metal complexes of
pyridine-2,6-dicarboxylic acid containing 4-picoline as auxiliary
ligand. Eur J Med Chem. 2010;45(1):264–9.
2
2
4
. Siddiqi ZA, Shahid M, Khalid M, Kumar S. Antimicrobial and
SOD activities of novel transition metal ternary complexes of
iminodiacetic acid containing a-diimine as auxiliary ligand. Eur J
Med Chem. 2009;44(6):2517–22.
2
2
2
4. Batten SR, Harris AR. trans-Tetraaquabis(pyridine-3-carboxy-
late-jN)nickel(II). Acta Crystallogr Sect E. 2001;57:9–11.
5. Prasanna S, Bijini BR, Babu KR, Eapen SM, Deepa M, Nair
CMK. Growth and characterisation of a novel polymer of man-
5
6
. Dabrowiak JC. Metals in medicine. Hoboken: Wiley; 2017.
. Gielen M, Tiekink ER, editors. Metallotherapeutic drugs and
metal-based diagnostic agents: the use of metals in medicine.
Hoboken: Wiley; 2005.
ganese(II) nicotinate single crystal.
011;333(1):36–9.
6. Hauptmann R, Kondo M, Kitagawa S. Crystal structure of bis(4-
aminobenzoato)aquacadmium dihydrate, [Cd(H NC COO) (-
O)] O. Z Kristallogr NCS. 2000;215:169–72.
J
Cryst Growth.
´
7
8
. Kalinowska M, Swiderski G, Matejczyk M, Lewandowski W.
Spectroscopic, thermogravimetric and biological studies of Na(I),
Ni(II) and Zn(II) complexes of quercetin. J Therm Anal Calorim.
2016;126(1):141–8.
. Kalinowska M, Piekut J, Bruss A, Follet C, Sienkiewicz-Gromiuk
2
2
2
2
H
6 4
2
H
2
n
Á2nH
2
7. Chapman ME, Ayyappan P, Foxman BM, Yee GT, Lin W.
Synthesis, X-ray structures, and magnetic properties of copper(II)
pyridinecarboxylate coordination networks. Cryst Growth Des.
´
J, Swisłocka R, Lewandowski W. Spectroscopic (FT-IR, FT-
1
13
Raman, H, C NMR, UV/Vis), thermogravimetric and antimi-
crobial studies of Ca(II), Mn(II), Cu(II), Zn(II) and Cd(II) com-
plexes of ferulic acid. Spectrochim Acta, Part A.
2
001;1(2):159–63.
8. Lu TB, Luck RL. Interpenetrating nets in cis–bis (pyridine-4-
carboxylate) nickel(II). Acta Crystallogr Sect C.
002;58(3):152–4.
9. Vargov a´ Z, Zele o` a´ k V, C ´ı saøov a´ I, Gy o¨ ryov a´ K. Correlation of
thermal and spectral properties of zinc(II) complexes of
pyridinecarboxylic acids with their crystal structures. Ther-
mochim Acta. 2004;423(1):149–57.
2
2
2
014;122:631–8.
9
. Samsonowicz M, Kami n´ ska I, Kalinowska M, Lewandowski W.
Alkali metal salts of rutin–synthesis, spectroscopic (FT-IR, FT-
Raman, UV–Vis), antioxidant and antimicrobial studies. Spec-
2
trochim Acta, Part A. 2015;151:926–38.
´
1
0. Koczo n´ P, Piekut J, Borawska M, Swisłocka R, Lewandowski W.
The relationship between chemical structure and antimicrobial
activity of selected nicotinates, p-iodobenzoates, picolinates and
isonicotinates. Spectrochim Acta, Part A. 2005;61(8):1917–22.
1. Kalinowska M, Laderiere B, Champagne P, Kowczyk-Sadowy
M, Lewandowski W. Mn(II), Cu(II) and Cd(II) p-coumarates:
3
0. Allan JR, Geddes WC, Hindle CS, Orr AE. Thermal analysis
studies on pyridine carboxylic acid complexes of zinc(II). Ther-
mochim Acta. 1989;153:249–56.
1
1
23

Thermal, spectroscopic, X-ray and theoretical studies of metal complexes…
3
3
3
3
3
1. Artetxe B, San Felices L, Reinoso S, Martin-Caballero J,
Gutierrez-Zorrilla JM. Diaqua-trans-bis(pyridazine-3-carboxy-
lato-j2N2, O)cobalt(II). Acta Crystallogr Sect E. 2013;69:420–1.
2. Starosta W, Leciejewicz J. trans-Tetraaquabis(pyridazine-4-car-
boxylato-jO) magnesium(II) dihydrate. Acta Crystallogr Sect E.
49. Ji HF, Zhang HY. A new strategy to combat Alzheimer’s disease.
Combining radical-scavenging potential with metal-protein-at-
tenuating ability in one molecule. Bioorg Med Chem Lett.
2005;15(1):21–4.
50. Minot C. Graphite as an aromatic system. J Phys Chem.
1987;91:6380–5.
2
011;67:m316.
3. Longley DB, Harkin DP, Johnston PG. 5-Fluorouracil: mecha-
nisms of action and clinical strategies. Nat Rev Cancer.
51. Zhou Z, Parr RG, Garst JF. Absolute hardness as a measure of
aromaticity. Tetrahedron Lett. 1988;29:4843–6.
2
003;3(5):330–8.
52. Koczo n´ P, Dobrowolski JC, Lewandowski W, Mazurek AP.
Experimental and theoretical IR and Raman spectra of picolinic,
nicotinic and isonicotinic acids. J Mol Struct. 2003;655(1):89–95.
53. Nakamoto K, McCarthy PJ. Spectroscopy and structure of metal
chelate compounds. New York: Wiley; 1968.
54. Lewandowski W, Kalinowska M, Lewandowska H. The influence
of metals on the electronic system of biologically important
ligands. Spectroscopic study of benzoates, salicylates, nicotinates
and isoorotates. J Inorg Biochem. 2005;99(7):1407–23.
4. Yerragunta V, Patil P, Anusha V, Kumaraswamy T, Suman D,
Samhitha T. Pyrimidine and its biological activity: a review.
Pharma Tutor. 2013;1(2):39–44.
5. Kleschick WA, Costales MJ, Dunbar JE, Meikle RW, Monte WT,
Pearson NR, Sinder SW, Vinogradoff AP. New herbicidal
derivatives of 1,2,4-triazolo [1,5-a] pyrimidine. Pesticide Sci.
1
990;29(3):341–55.
3
3
3
6. Smith LH, Baker FA. Pyrimidine metabolism in man. I. The
biosynthesis of orotic acid. J Clin Invest. 1959;38(5):798–809.
7. Hallanger LE, Laakso JW, Schultze MO. Orotic acid in milk.
J Biol Chem. 1953;202:83–9.
8. L o¨ ffler M, Carrey EA, Zameitat E. Orotate (orotic acid): an
essential and versatile molecule. Nucleos Nucleot Nucl Acid.
´
´
55. Lewandowski W, Swiderski G, Swislocka R, Wojtulewski S,
Koczo n´ P. Spectroscopic (Raman, FT-IR and NMR) and theo-
retical study of alkali metal picolinates. J Phys Org Chem.
2005;18(9):918–28.
56. Mrozek R, Rz a˛ czy n´ ska Z, Sikorska-Iwan M, Jaroniec M,
Głowiak T. A new complex of manganese(II) with L-a-alanine:
structure, spectroscopy and thermal study. Polyhedron.
1999;18:2321–6.
57. Sikorska-Iwan M, Mrozek-Łyszczek R. Application of coupled
TG-FTIR system in studies of thermal stability of manganese(II)
2
016;35(10–12):566–77.
3
9. Frisch M, Trucks GW, Schlegel HB, Scuseria GE, Robb MA,
Cheeseman JR, Scalmani G, Barone V, Mennucci B, Petersson
GA. Gaussian 09, revision A. 02. Wallingford: Gaussian, Inc.;
2
009.
4
4
0. Breda S, Reva ID, Lapinski L, Nowak MJ, Fausto R. Infrared
spectra of pyrazine, pyrimidine and pyridazine in solid argon.
J Mol Struct. 2006;786(2–3):193–206.
1. Destexhe A, Smets J, Adamowicz L, Maes G. Matrix isolation
FT-IR studies and ab initio calculations of hydrogen-bonded
complexes of molecules modeling cytosine or isocytosine tau-
complexes with amino acids.
2004;78:487–500.
58. Mrozek-Łyszczek R. Thermal investigations of cefadroxil com-
plexeswith transition metals coupled TG-DSC and TG-FTIR
techniques. J Therm Anal Calorim. 2004;78:473–86.
J Therm Anal Calorim.
59. Łyszczek R, Głuchowska H, Sienkiewicz-Gromiuk J, Mazur L,
Tarasiuk B. Coordination polymers of Na(I), Mg(II) and Co(II)
tomers. 1. Pyridine and pyrimidine complexes with H
matrixes. J Phys Chem. 1994;98(5):1506–14.
2
O in Ar
0
ions based on biphenyl-4,4 -diacetic acid: synthesis, crystal
structures and thermal properties. Polyhedron. 2015;99:132–40.
60. Bartyzel A. Effect of molar ratios of reagents and solvent on the
4
2. Krygowski TM, Cyra n´ ski M. Separation of the energetic and
geometric contributions to the aromaticity of p-electron carbo-
cyclics. Tetrahedron. 1996;52(5):1713–22.
complexation process of nickel(II) ions by the N
base. Polyhedron. 2017;134:30–40.
2 3
O -donor Schiff
4
3. Krygowski TM, Cyra n´ ski M. Separation of the energetic and
geometric contributions to the aromaticity. Part IV. A general
61. Bartyzel A. Synthesis, thermal study and some properties of
-donor Schiff base and its Mn(III), Co(II), Ni(II), Cu(II) and
model for
1996;52:10255–64.
thep-electron
systems.
Tetrahedron.
2 4
N O
Zn(II) complexes. J Therm Anal Calorim. 2017;127:2133–47.
62. Łyszczek R, Bartyzel A, Głuchowska H, Mazur L, Sztanke M,
Sztanke K. Thermal investigations of biologically important
fused azaisocytosine-containing congeners and the crystal struc-
ture of one representative. J Anal Appl Pyrol. 2018;135:141–51.
63. Breda S, Reva ID, Lapinski L, Nowak MJ, Fausto R. Infrared
spectra of pyrazine, pyrimidine and pyridazine in solid argon.
J Mol Struct. 2006;786:193–206.
4
4
4
4. Bird C. A new aromaticity index and its application to five-
membered ring heterocycles. Tetrahedron. 1985;41:1409–14.
5. Diffraction RO, Rigaku Oxford Diffraction. CrysAlisPro software
system, version 1.171.38.46. Oxford: Rigaku Corporation; 2017.
6. Dolomanov OV, Bourhis LJ, Gildea RJ, Howard JAK, Posch-
mann H. OLEX2: a complete structure solution, refinement and
analysis program. J Appl Cryst. 2009;42(2):339–41.
4
4
7. Sheldrick GM. A short history of SHELX. Acta Crystallogr Sect
A. 2008;64:112–22.
8. Oliveira G, Martin JML, Proft F, Geerlings P. Electron affinities
of the first- and second-row atoms: benchmark ab initio and
density-functional calculations. Phys Rev A. 1999;60:1034–45.
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