The investigations of thermal behavior, kinetic analysis, and biological activity of trinuclear complexes prepared ONNO-type Schiff bases with nitrito and nitrato μ-bridges

Article abstract of DOI:10.1007/s10973-016-6004-7

By using bis-N,N′(salicylidene)-1,3-diaminopropane and reduced form of this ligand bis-N,N′(2-hydroxybenzylidene)-1,3-diaminopropane, we prepared eight trinuclear complexes in the core form of Ni^II–Ni^II–Ni^II and Ni^II–Cu^II–Ni^II. Complexes have been characterized with element analysis, IR spectroscopy and NMR spectroscopy methods and also investigated with Thermogravimetry (TG). It was observed that thermal characteristics of the complexes prepared by the reduced form of Schiff base are different from complexes prepared by the Schiff base. According to TG, two thermal reactions between 120 and 180?°C endothermic separation of coordinative dimethylformamide molecules and then around 300?°C exothermic decomposition of molecule were observed for Schiff base-prepared complexes. On the other hand, the complexes resulted from reduced Schiff base reactions were shown decomposed around 250–270?°C by exothermic thermal reaction. Kinetic parameters of decompositions were determined by isothermal and non-isothermal kinetic methods, Coats–Redfern (CR), Ozawa, Ozawa–Flynn–Wall (OFW) and Kissenger–Akahira–Sunose (KAS). Departing from these values, thermodynamic parameters were calculated and the results were interpreted. It was concluded that the complexes prepared with reduced Schiff bases are more strained structures. Biological activities of these complexes were also inspected, and antibacterial and antifungal activities were tested against four different bacterial strains (E. coli, P. aureginosa, S. aureus and E. feacalis) and a fungus species (C. albicans).

Full text of DOI:10.1007/s10973-016-6004-7

J Therm Anal Calorim
DOI 10.1007/s10973-016-6004-7
The investigations of thermal behavior, kinetic analysis,
and biological activity of trinuclear complexes prepared ONNO-
type Schiff bases with nitrito and nitrato l-bridges
1
1
2
3
•
Nurcan Acar
Ingrid Svoboda
•
Orhan Atakol
2
•
S¸ aziye Bet u¨ l Sopacı
•
Demet Cansaran Duman
4
•
¨
Sevi Oz
Received: 3 July 2016 / Accepted: 25 November 2016
Ó Akad e´ miai Kiad o´ , Budapest, Hungary 2016
0
Abstract By using bis-N,N (salicylidene)-1,3-diamino-
0
concluded that the complexes prepared with reduced Schiff
bases are more strained structures. Biological activities of
these complexes were also inspected, and antibacterial and
antifungal activities were tested against four different
bacterial strains (E. coli, P. aureginosa, S. aureus and E.
feacalis) and a fungus species (C. albicans).
propane and reduced form of this ligand bis-N,N (2-hy-
droxybenzylidene)-1,3-diaminopropane, we prepared eight
II
trinuclear complexes in the core form of Ni –Ni –Ni and
II
II
II
II
II
Ni –Cu –Ni . Complexes have been characterized with
element analysis, IR spectroscopy and NMR spectroscopy
methods and also investigated with Thermogravimetry
(
TG). It was observed that thermal characteristics of the
Keywords Reduced Schiff base Á Trinuclear complex Á
Isothermal and non-isothermal kinetic Á Ozawa method Á
OFW Á Coats–Redfern method
complexes prepared by the reduced form of Schiff base are
different from complexes prepared by the Schiff base.
According to TG, two thermal reactions between 120 and
1
80 °C endothermic separation of coordinative dimethyl-
formamide molecules and then around 300 °C exothermic
decomposition of molecule were observed for Schiff base-
prepared complexes. On the other hand, the complexes
resulted from reduced Schiff base reactions were shown
decomposed around 250–270 °C by exothermic thermal
reaction. Kinetic parameters of decompositions were
determined by isothermal and non-isothermal kinetic
methods, Coats–Redfern (CR), Ozawa, Ozawa–Flynn–
Wall (OFW) and Kissenger–Akahira–Sunose (KAS).
Departing from these values, thermodynamic parameters
were calculated and the results were interpreted. It was
Introduction
0
Bis-N,N (salicylidene)-1,3-diaminopropane (LH ) and their
2
derivatives are very inclined ligands to give polynuclear
complexes; since 1990, there are number of homo and
hetero polynuclear complexes prepared with these ligands
and were reported in the literature [1–25]. During the
formation of these polynuclear complexes, acetate
[2–10, 21, 22], chloride [11], azide, formate [15–18],
benzoate [18], nitrite [19] and nitrate [17, 20] anions
constitute l-bridge. The structure of the coordination
sphere of the terminal and central metal ions is different in
trinuclear complexes. Terminal metal ions are located in
¨
Sevi Oz
sevioz@hotmail.com
&
between two nitrogen of LH ligand, two phenolic and one
2
solvent molecule oxygen and anion in the environment
1
2
3
4
(
acetate, format, benzoate, nitrite or nitrate) having a
Department of Chemistry, Faculty of Science, Ankara
University, 06100 Ankara, Turkey
coordination sphere as N O form; however, central metal
2
4
ions formed coordination between four phenolic oxygen
and oxygen of anion in the environment and have O6
coordination sphere [5–10]. Trinuclear complexes can be
prepared by two different ways by using Schiff bases.
First of them is template synthesis method. According to
this method, ligand, metal ions and combining anion are
Department of Chemistry, Faculty of Science and Arts, Ahi
Evran University, 40100 Kır s¸ ehir, Turkey
Biotechnology Institute, Ankara University, 06100 Ankara,
Turkey
Strukturforschung, FB Materialwissenschaft, TU- Darmstadt,
Petersenstrasse 23, 12 64287 Darmstadt, Germany
123

N. Acar et al.
reacted in a proper solvent sample such as DMF, DMSO or
in dioxane media and trinuclear complexes are obtained as
a result, [21–25].
complexes were prepared by template synthesis and
examined by thermogravimetry. In these complexes, nitrite
and nitrate auxiliary anions were used as l-bridge. There
are some examples for trinuclear complexes prepared by
using these anions in the literature, and in these reports,
structures of l-bridges made by nitrite and nitrate anions
were determined [15–18, 20]. While nitrite anion is con-
nected to terminal metal ion over oxygen, it is also con-
nected to central metal ion over nitrogen ion; nitrate anion
is connected to terminal metal ion by oxygen and con-
nected to central metal ion with second oxygen. The
complexes prepared in this study were not obtained as
proper crystals, but a similar structure, which was prepared
to show the coordination of the nitrate ion, is included in
The second method consists of two steps. LH2 and
mononuclear NiL complex could be formed by interacting
nickel salts, and then, trinuclear complex could be syn-
thesized with this mononuclear complex in DMF, DMSO
or dioxane as solvent, [16, 23].
Schiff bases could be easily reduced in amphiprotic
solvents with the help of NaBH [21–23]. In consequence
4
of reducing imine, nitrogen groups could be transformed
into secondary amine groups and phenol–amine ligands are
obtained from phenol–imine-type ligands, Fig. 1.
So far, it is not possible to prepare a mononuclear
H
complex with reduced ligands and a NiL stoichiometry
0
this study. This complex was prepared by bis-N,N (2-hy-
complex was not isolated. For that reason, two-step syn-
thesis of these complexes with reduced Schiff bases is not
possible. By using reduced Schiff bases, trinuclear com-
plexes were obtained by template synthesis, [21–25].
Taking into account iminic nitrogens are converted to
amines, electron density of the nitrogens should increase in
the reduced ligand. Therefore, easier synthesis of
mononuclear Ni(II) complexes was expected. There are
many proper dealings related with the complex formation
using the above Schiff base compound and its reduced
states. Structural analysis of the Schiff base complex
reveals 10°–18° angle between the metal ion-two iminic
nitrogen and two iminic nitrogen—bonded carbon atoms
planes. In the reduced state, this angle is 35°–40° [26, 27].
Ideally, this angle is around 62°. Under these circum-
stances, the reduced Schiff base complex is expected to be
more stable, but a stable mononuclear complex was not
isolated. To explain this, thermogravimetrical analysis was
employed and many reports have been published related
with TG analysis of trinuclear complexes prepared with
Schiff bases [18, 28].
droxyacetophenone)-1,3-propanediamine (LACH2) and
added to this study in order to show l-bridges of nitrate
ion. The total formulas of prepared complexes are shown
below, and structures are shown in Fig. 2.
Complexes prepared by Schiff bases
{
[DMFÁNiLÁCu(NO
[DMFÁNiLÁCu(NO
2
)
2
ÁNiLÁDMF]Á1/2DMF}
ÁNiLÁDMF]ÁDMF}
(I)
{
)
3 2
(II)
(III)
(IV)
(V)
[
DMFÁNiLÁNi(NO
2
)
2
ÁNiLÁDMF]
{
[DMFÁNiLÁNi(NO
[DMFÁNiLACÁCu(NO
3
)
2
ÁNiLÁDMF]Á2DMF}
{
3 2
) ÁNiLACÁDMF]ÁDMF}
Complexes prepared with reduced Schiff bases
H
H
[
[
[
DMFÁNiL ÁCu(NO
2
)
2
ÁNiL ÁDMF]
(VI)
H
H
DMFÁNiL ÁCu(NO
)
3 2
ÁNiL ÁDMF]
(VII)
(VIII)
(IX)
H
H
DMFÁNiL ÁNi(NO
2
)
2
ÁNiL ÁDMF]
H
H
[DMFÁNiL ÁNi(NO
3
)
2
ÁNiL ÁDMF]
To investigate the strain possibility of these two com-
plex groups, we examined them by thermogravimetric
methods. Although complexes in these two groups are in
similar structures, their thermo gravimetric curves were
significantly different from each other. Activation energy
and other thermodynamic parameters were calculated by
isothermal and non-isothermal thermokinetic methods and
compared. Activation energy was expected to be smaller in
strained complexes, for that reason more than one methods
In these researches, it was clearly observed that DMF
molecules connected to terminal groups were separated
from structure as thermally and mass losses gave signifi-
cant results in characterization of complexes. But this mass
loss related to the DMF’s separation was not observed in
reduced Schiff bases. In order to explain this situation, by
using nitrite and nitrate-bridged anions with LH ligand
2
H
four complexes and with L H ligands, four trinuclear
2
0
Fig. 1 Bis-N,N (salicylidene)-
1
H
H
,3-propanediamine ligand’s
reduction reaction
H
H
NaBH
in MeOH
4
N
N
C
C
N
N
C
C
H
H
H
H
OH
HO
OH
HO
H
L H
phenol–amine
2
LH2
phenol–imin
1
23

The investigations of thermal behavior, kinetic analysis, and biological activity of trinuclear...
Fig. 2 Structures of the
prepared complexes
CH3
CH3
CH3
H
H
N
C
N
C
O
O
CH3
H
H
H
H
C
N
N
C
C
N
N
C
Ni
Ni
O
O
O
O
O
O
O
O
N
M
N
O
M
O
N
N
O
O
O
O
O
O
O
O
Ni
Ni
N
N
C
N
N
C
C
C
H
H
H
H
H3C
H3C
H3C
H3C
O
O
N
C
N
C
H
H
M=Cu(II) (II)
M=Ni(II) (IV)
M=Cu(II) (I)
M=Ni(II) (III)
CH
3
CH
3
H
C
O
H
C
O
N
N
CH
3
CH
3
H
H
H
H
C
NH
HN
C
H
C
H
NH
HN
C
H
H
Ni
Ni
O
O
O
O
O
O
O
O
O
O
N
M
O
N
M
N
O
N
O
O
O
O
O
O
Ni
Ni
H
C
H
H
C
H
NH
HN
C
NH
HN
C
H
H
H
H
H
3
C
3
H C
O
O
N
C
N
C
H
3
C
H
H
3
C
H
M=Cu(II) (VI)
M=Ni(II) (VIII)
M=Cu(II) (VII)
M=Ni(II) (IX)
123

N. Acar et al.
were used for calculation. Since it is possible to direct
calculation of activation energy from thermo gravimetry
curves employing Ozawa equation with a software, TA60
Version 2.01 of the device that we used, we preferred to
use Ozawa method first [29, 30]. But due to explosive
effects of nitrite and nitrate ions in higher temperatures,
Ozawa method did not give any result for explosive
exothermic reactions. For that reasons, non-isothermal
kinetic methods Ozawa–Flynn–wall [31–35] and Kissen-
ger–Akahira–Sunose [33–37], and as isothermal method
Coast–Redfern [38, 39] were employed manually and
thermokinetic results were obtained.
X-ray crystallography
A single crystal of [DMFÁNiLACÁCu(NO
)
3 2
ÁNiLACÁDMF]
(complex V) was analyzed on an Oxford Diffraction
Xcalibur single-crystal X-ray diffractometer with a sap-
phire
CCD
detector
using
MoKa
radiation
(k = 0.71073 A) operating in x/2h scan mode. The unit-
cell dimensions were determined and refined by using the
angular settings of 25 automatically centered reflections in
2.85° B h B 228.24° range. The data of the complex V
were collected at 100(2) K. The empirical absorption cor-
rections were applied by the semi-empirical method via the
CrysAlis CCD software [40]. The model was obtained from
the results of the cell refinement, and the data reductions
were carried out using the solution software SHELXL97
[41]. The structure of the complex V was determined by
direct methods using the SHELXS-97 software implemented
in the WinGX package [42]. Supplementary material for
structure has been deposited with the Cambridge Crystal-
lographic Data Center as CCDC no: 1481757 (de-
posit@ccdc.cam.ac.uk or http://www.ccdc.cam.ac.uk).
In the scope of this study, we also investigated biolog-
ical activity of these complexes split into two different
groups to compare the influence of different structures to
their bioactivity, in consistent with the literature [38, 39].
Biological activities were determined on seven complexes.
Behaviors of these complexes in DMF solution were
assessed against gram-negative bacteria Echericia coli and
Pseudomonas aurogines and against gram-positive bacteria
Staphilococcus aureus and Entorococcus feacalis and a
fungus Candida albicans. Minimum Inhibitory Concen-
tration (MIC) values were determined for the eight
complexes.
Biological activity of the complexes
Microbial strains
Experimental
In the examined study, microorganisms were selected to
include gram-positive bacteria (Staphylococcus aureus
ATCC 25923 and Enterococcus feacalis RSKK 508),
gram-negative bacteria (Pseudomonas aeruginosa ATCC
9027 and E. Coli ATCC 35218) and yeast (Candida albi-
cans ATCC 10231). All the strains were stored at -20 °C
in tryptic soya broth (TSB; Oxoid, Basingstoke, UK) with
20% glycerol.
Materials and apparatus
Used reactives were of Merck or Fluka brands, and they
were used without further purification. In this study, Shi-
madzu Infinity FTIR spectrometer equipped with three
-
1
reflectional ATR units was used for IR spectra with 4 cm
accuracy. The C, H and N analyses were performed on
Eurovector 3018 C,H,N,S analyzer. Metal analyses were
recorded on GBC Avanta PM Model atomic absorption
spectrometer using FAAS mode. Complex (2–3 mg) was
dissolved in 1 mL HNO3 (63%) with heating, diluted to
The inocula of microorganism strains were prepared
from an overnight culture for bacteria in Muller–Hinton
agar, whereas Sabouraud agar was used for growing the
fungi. The suspensions were adjusted to 0.5 McFarland for
8
the turbidity (1 9 10 colony-forming units [CFU]/mL).
1
00 mL and given to nebulizer of atomic absorption
spectroscopy for metal analysis. The mass spectra of the
ligands were obtained by Shimadzu, 2010 plus with direct
inlet (DI) unit with an electron impact ionizer. DI tem-
perature was varied between 40 and 140 °C, and ionization
was done with electrons with 70 eV energy. The NMR
spectra were recorded on the Bruker Ultrashield 300 MHz
NMR spectrometer. DMSO-d6 solution was the solvent.
The thermogravimetric analyses were performed by Shi-
madzu DTG 60H. In thermogravimetric analyses, temper-
ature was varied between 30 and 600 °C. These analyses
were performed at 5, 10, 15, 20 and 25 °C/min rates and
under N2 atmosphere in Pt pans. Calibration of the
instrument was done with metallic In and Pb.
Antibacterial and antifungal test
The antimicrobial activity of the synthesized chemicals was
assayed for the microdilution method, which determines the
minimum inhibitory concentration (MIC) leading to the
inhibition of bacterial growth. The composites in dispersion
form were diluted 2–128 times with 100 mL of Mueller–
Hinton broth inoculated with the tested bacteria at a con-
5
centration of 1°9 10 CFU/mL. The MIC was read after 24 h
of incubation at 37 °C as the MIC of the tested substance that
inhibited the growth of the bacterial strain. The dispersions
were used in the form in which they had been prepared.
Therefore, control bactericidal tests of solutions were
1
23

The investigations of thermal behavior, kinetic analysis, and biological activity of trinuclear...
3
performed containing all the reaction components. Saturated
stock solutions of the extracts were prepared in DMSO.
Double serial dilutions were also prepared in the same sol-
vent. Aliquots of the solutions (1 mL) were mixed with a
fixed amount of molten Muller–Hinton agar at 45 °C to get
the final concentrations. When the agar solidified, the plates
benzaldehyde (0.1 mol, 12.20 g) was dissolved in 120 cm
of warm EtOH; then, 0.05 mol (3.70 g) of 1,3-diamino-
propane was added to this solution and heated up to the
boiling point. After cooling, yellow crystals were filtered
and dried in air. Yield: 90–95%, mp: 58 °C (determined by
TG).
6
were inoculated with 10 lL microbial suspension (1°9 10
CFU/mL). The inoculated plates were incubated for 24 h at
Elemental analysis for C H N O
7 18 2 2
1
35 °C for bacteria and for 48 h for the yeast. Each of the
chemicals (0.312, 2.5, 1.25, 0.625 and 0.312 mg) were added
in the plates. Positive controls for all microorganisms were
prepared using 1 mL DMSO instead of an extract solution.
After incubation, the plates were inspected visually. MIC was
recorded as the lowest concentration at which no visible
growth of the test pathogens was observed. The test was not
considered valid unless the positive controls showed signifi-
cant microbial growth. Standard antibiotic (amoxicillin) were
used to control the sensitivity of the tested bacteria, and
amphotericin B was used as controls against the tested fungi.
Anal. Calcd. %: C 72.32; H 6.43; N 9.92.
Found %: C 71.95; H 6.33; N 10.09.
-
1
Important IR data (cm ): mO–H
3021–3019, mC–H(Aliph): 2929–2862, mC=N: 1629, mC=C(ring)
1608, mC–O(Phenol): 1274–1151, d : 762.
:
2627, mC–H(Ar)
:
:
C–H(Ar)
-1
3
-1
Kmax = 243 nm, e = 7045 dm mol cm in DMSO,
kmax = 242 nm, e = 7865 dm mol cm in MeOH.
3
-1
-1
1
HNMR data in d -DMSO(d, ppm): 13.51 (s) (O–H),
6
8.60 (s) (–CH=), 7.43 (d) (H ), 7.32 (t) (H ), 6.88
Ar Ar
(t) (H ), 3.68 (t) (N–CH –), 2.01 (p) (–CH –), Fig. 3.
Ar 2 2
Preparation of the ligands
1
3
CNMR data in d6 DMSO(d, ppm): 166.6 (–C=N),
61.1, 132.7, 132.1, 119.1, 118.9 116.9 (C ), 58.5 (N–
1
Ar
Preparation of N,N-bis (2-hydroxyphenylidene)-1,3-
propanediamine (LH2)
CH –), 31.9 (–CH –), Fig. 4.
2
2
?
MS m/z: 282 [M] , 161 [HO–C H –CH=N–CH –CH –
6
4
2
2
?
?
This Schiff base was prepared via condensation reaction in
EtOH under hydrothermal conditions using 2-hydroxy-
benzaldehyde and 1,3-diaminopropane. 2-Hydroxy-
CH ] , 148 [HO–C H –CH=N–CH –CH ] (Basepeak),
2 6 4 2 2
?
134 [HO–C H –CH=N–CH ] , 120 [HO–C H –CH=N] ,
?
6
4
2
6 4
?
107 [HO–C H –CH ] , 77 [C H ] , Fig. 5.
?
6
4
2
6
5
13
12
11
10
9
8
7
6
5
4
3
2
1
0
–1 ppm
1
Fig. 3 HNMR spectrum of LH
2
220
200
180
160
140
120
100
80
60
40
20
0
ppm
1
3
Fig. 4 CNMR spectrum of LH
2
123

N. Acar et al.
%
1
48
100
7
5
2
5
0
5
0
2
82
1
07
7
7
1
150
62
4
1
5
197
200
239
250
338
16
3
647
650
0
100
300
350
400
450
500
550
600
2
Fig. 5 MS fragments of LH obtained using DI equipment
13
12
11
10
9
8
7
6
5
4
3
2
1
0
–1 ppm
1
Fig. 6 HNMR spectrum of L H
H
2
3
stirring, 300 cm of ice water was added to it. The final
The phenolic hydrogens are observed at 13.51 ppm, the
iminic hydrogens at 8.60 ppm and aromatic hydrogens at
1
mixture was left to stand for 24 h. After filtration, the white
0
7
.43–6.68 ppm d value in HNMR spectrum. As expected
the aliphatic hydrogens are seen at 3.68 and 2.01 ppm as
precipitate was air-dried. The product bis-N,N (2-hydroxy-
H
benzyl)-1,3-propanediamine (L H ) was recrystallized from
2
triplet and pentet, respectively. On the other hand, in
1
CNMR spectrum are seen 9 different carbon atoms sig-
hot EtOH:H O (2:1, v/v). Yield: 55–60%, mp: 107 °C.
2
3
nals as expected. It is probable that the signal at 166 ppm
observed is the signal of iminic carbon atom. The molec-
Elemental analysis for C H N O
7 22 2 2
1
ular mass of LH Schiff base can be seen from the MS
2
Anal. Calcd. %: C 71.30; H 7.74; N 8.01.
Found %: C 70.86; H 6.69; N 8.37.
spectrum, and the signal at 282 m/z value observed is the
molecular peak of LH2.
-
1
Important IR data (cm ): mN–H
:
3307, mC–H(Ar):
Preparation of N,N-bis (2-hydroxybenzyl)-1,3-
H
propanediamine (L H )
3055–3023, mC–H(Aliph): 2967–2823, mC=C(ring): 1606–595,
mCO(Phenol): 1253–1099, dC–H (Ar): 752.
2
1
H NMR data in d -DMSO(d, ppm): 7.12 (m), 6.67 (m),
0
6
3
.0 g of bis-N,N (salicylidene)-1,3-propanediamine (LH )
2
6
.83 (broad), 3.80 (m), 2.56 (m), 1.15 (m), Fig. 6.
3
was dissolved in 70.0 cm of MeOH by stirring and heat-
1
3
ing. This solution was heated up to 50 °C, and to this
solution, solid NaBH in small portions was added until
C NMR data in d -DMSO (d, ppm): 157.64, 128.43,
6
127.78, 124.61, 118.34, 115.39 (C ), 50.80 (Ar–CH –N),
Ar 2
4
colorless under strong mixing [31–34]. After 10 min of
46.30 (HN–CH ), 28.94 (CH –CH –CH ), Fig. 7.
2
2
2
2
1
23

The investigations of thermal behavior, kinetic analysis, and biological activity of trinuclear...
220
200
180
160
140
120
100
80
60
40
20
0
ppm
1
3
H
Fig. 7 CNMR spectrum of L H
2
%
107
100
136
7
5
0
5
5
2
148
150
179
180
77
4
4
57
286
3
38
95
213
241
250
265
305
300
352
350
376
0
5
0
100
200
H
Fig. 8 MS fragments of L H
2
obtained using DI equipment
MS (m/z): 286 (molecular peak), 179 [HO–C H –CH –
6
0.05 mol (3.70 g) of 1,3-diaminopropane was added to this
solution and heated up to the boiling point. After cooling,
yellow crystals were filtered and dried in air. Yield:
94–96%, mp: 123.6 °C (determined by TG).
4
2
?
NH–CH –CH –CH –NH] , 163 [HO–C H –CH –NH–
2
2
2
6
4
2
?
CH –CH –CH ] , 150 [HO–C H –CH –NH–CH –CH ] ,
?
2
2
2
6
4
2
2
2
?
1
36 [HO–C H –CH –NH–CH ] , 122 [HO–C H –CH –
6 4 2 2 6 4 2
?
NH] , 107 [HO–C H –CH ] (base peak), 90 [C H –
?
6
4
2
6 4
?
CH ] , 77 [C H ] , Fig. 8.
?
2
6 5
Elemental analysis
As shown in Fig. 6, a broad signal is observed between
aromatic hydrogens signals. This signal is probably from
amine hydrogens. But this signal was not observed in the
diluted solution, whereas the signal of the phenolic
hydrogens was seen at 13.2 ppm d value in diluted solu-
tion. Due to the hydrogen bond formation, the signal of
amine hydrogens is observed as a broad peak. Nine dif-
Expected % C: 73.52, H: 7.14, N: 9.02; Found % C: 73.09,
H: 6.35, N: 8.82.
-
1
Important IR data (cm ): mC–H(Ar)
:
3036–3017,
mC–H(Aliph): 2922–2944–2866, mC=N: 1610, mC=C(ring): 1600,
mC–O(Phenol): 1232–1159, dC–H(Ar): 754.
13
1
ferent C atoms signals are observed from the CNMR
spectrum. As the iminic double bond is transformed into a
single bond, a signal at 166 ppm around is not observed,
despite that to a new signal around 50 ppm. Weak
molecular peak of the reduced Schiff base is observed at
HNMR data in d -CH COCH : 13.68 (s), 8.71 (s), 7.45
6
3
3
(dd), 7.34 (td), 6.91 (t), 3.52 (t), 2.06 (p).
1
3
CNMR data in d-CHCl3: m/z: 310 (MP), 193, 179, 164,
150, 136, 121 (BP), 107, 91.
2
86 m/z value from the mass spectrum.
Preparation of the complexes
Preparation of N,N-bis (2-hydroxyacetophenilidene)-1,3-
propanediamine (LACH2)
As given above, trinuclear complexes can be synthesized
by two different methods. The first method is known as
template method. In this method, all reagents are reacted in
the same solvent, Scheme 1.
This Schiff base was obtained from 2-hydroxyacetophe-
none and 1,3-diaminopropane in EtOH under hydrothermal
The second method occurs in two steps: firstly, a
mononuclear complex is obtained; then, trinuclear complex
is synthesized in the second step, Scheme 2.
conditions using. 2-Hydroxyacetophenone (0.1 mol,
3
3.60 g) was dissolved in 150 cm of warm EtOH; then,
1
123

N. Acar et al.
3048–3029,
-
1
in DMF
Important IR data (cm ): mC–H(Ar):
2
2
LH
2
+ 3NiX
2
2
DMF·NiL·NiX ·NiL·DMF
mC–H(Aliph): 2924–2873, mC=O(DMF): 1658, mC=N: 1627,
mC=C(ring): 1596, mN=O: 1309, dCH2: 1473, mC–O(Phenol)
197–1153, dC–H(Ar): 759.
–
4HCl
in DMF
:
1
LH
DMF·NiL
H
·NiX ·NiL ·DMF
H
H
2
+ 3NiX
2
2
–
2 HCl
Complex II, {[DMFÁNiLÁCu(NO ) ÁNiLÁDMF]ÁDMF}
3
2
(
C H N O Ni Cu)
43 53 9 13 2
–
–
–, NO –
X = CH
3
COO , HCOO , NO
2
3
Scheme 1 Direct trinuclear complex formation with Schiff bases or
reduced Schiff bases using template synthesis
Element analysis: Expected % C: 47.61, H: 4.92, N:
1
4
1.61, % Ni: 10.82, % Cu: % 5.85; Found % C: 47.11, H:
.59, N: 10.33, Ni: 10.23, Cu: 6.07 (This molecule is
Preparation of the Schiff base complexes (complex
I–IV)
included 1 molecule DMF as solvate).
-
1
Important IR data (cm ): mC–H(Ar)
:
3038–3026,
mC–H(Aliph): 2922–2845, mC=O(DMF): 1670, mC=N: 1631,
mC=C(ring): 1595, mN=O:1417–1440, dCH2: 1473, mC–O(Phenol)
These complexes are synthesized according to Scheme 2 in
two steps, previously was prepared mononuclear NiL
:
0
1296–1253, dC–H(Ar): 756.
complex from bis-N,N (salicylidene)-1,3-propanediamine
and NiCl Á6H O, secondly were prepared trinuclear com-
2
2
Complex III, [DMFÁNiLÁNi(NO ) ÁNiLÁDMF]
2 2
plexes I–IV using this NiL complex.
(
C H N O Ni )
40 46 8 10 3
Preparation of mononuclear NiL complex
NiL mononuclear complex was prepared as described
Element analysis: Expected % C: 49.28, H: 4.76, N:
1.49, % Ni: 18.06; Found % C: 48.51, H: 4.43, N: 10.85,
Ni: 17.44.
1
according to the literature [43]. A quantity of 0.05 mol
0
(
14.1 g) bis-N,N (salicylidene)-1,3-propanediamine was
-1
Important IR data (cm ): mC–H(Ar)
:
3040–3023,
dissolved in 150 mL hot EtOH, and 10 mL concentrated
ammonia was added to this solution. Then, a solution of
mC–H(Aliph): 2924–2839, mC=O(DMF): 1672, mC=N: 1628,
mC=C(ring): 1595, mN=O: 1309, dCH2: 1473, mC–O(Phenol): 1195,
dC–H(Ar): 758.
0
.05 mol (11.80 g) NiCl Á6H O in 50 mL hot water was
2
2
added to this mixture. After setting, the solution was set
aside for 2 h and light green precipitated was filtered and
dried in a oven at 140 °C for 3–4 h.
Complex IV, {[DMFÁNiLÁNi(NO ) ÁNiLÁDMF](DMF) }
3
2
2
(C H N O Ni )
46 60 10 12 3
Preparation of complexes I–IV
Elemental analysis: Expected % C: 49.28, H: 5.39, N:
2.48, % Ni: 15.70; Found % C: 48.69, H: 4.91, N: 11.87,
1
A quantity of 0.002 mol (0.680 g) of the complex NiL was
dissolved in 50 mL DMF by heating until 110 °C. For com-
plex I 0.001 mol (0.170 g) CuCl Á2H O and 0.002 mol
Ni: 151.22, Cu: 6.31 (This molecule is included 2 mole-
cules DMF as solvate).
2
2
-
1
Important IR data (cm ): mC–H(Ar)
:
3044–3027,
(
0.140 g) NaNO , for complex II 0.001 mol (2.41 g)
2
mC–H(Aliph): 2922–2862, mC=O(DMF): 1671, mC=N: 1629,
mC=C(ring): 1595, mN=O: 1400, dCH2: 1473, mC–O(Phenol)
Cu(NO ) Á3H O, for complex III 0.001 mol (0.236 g) NiCl
3
2
2
2-
:
2
H O and 0.002 mol (0.140 g) NaNO and for complex IV
2 2
1
193–1074, dC–H(Ar): 754.
0
.001 mol (0.291 g) Ni(NO ) Á6H O were dissolved in 30 mL
3
2
2
water–MeOH mixture (v/v: %50–%50) using heating and
mixed with the above solution. The resulting mixture was set
aside for 3–4 days in air. After this period, the precipitated
crystals products were filtered and dried in air. The analytical
results of the complexes synthesized are given below.
Preparation of the complex V
This complex was prepared by template method. A quan-
0
tity of 0.002 mol (0.640 g) bis-N,N (2-hydroxyacetophe-
nilidene)-1,3-propanediamine was dissolved in 40 mL
DMF by heating. To this solution was added 1.0 mL Et N
3
Complex I, [DMFÁNiLÁCu(NO ) ÁNiLÁDMF]
2
2
and a solution of 0.002 mol (0.472 g) NiCl Á6H O in
(
C H N O Ni Cu)
46
2
2
4
0
8
10
2
20 mL hot MeOH then finally was added to the mixture a
solution of 0.001 mol (2.41 g) Cu(NO ) Á3H O in 10 mL
Element analysis: Expected % C: 49.04, H: 4.73, N:
3 2
2
hot MeOH. The resulting mixture was set aside for 4 days,
and the precipitated crystals were filtered and dried in air.
1
4
1.43, % Ni: 11.98, % Cu: % 6.49; Found % C: 48.76, H:
.36, N: 10.95, Ni: 11.29, Cu: 6.31.
1
23

The investigations of thermal behavior, kinetic analysis, and biological activity of trinuclear...
Scheme 2 Preparing trinuclear
complex with Schiff bases and
mononuclear complexes
in MeOH or EtOH
2HCl
LH
2
+ NiX
2
NiL
step 1
–
in DMF
DMF·NiL·NiX
2
·NiL·DMF
2
NiL + NiX
2
step 2
–
2HCl
–
–
–, NO
–
X = CH
3
COO , HCOO , NO
2
3
H
H
{
[DMFÁNiLACÁCu(NO ) ÁNiLACÁDMF](DMF)},
Complex VII, [DMFÁNiL ÁCu(NO ) ÁNiL ÁDMF],
3 2
3
2
(
C H N O Ni Cu)
2
(C H N O Ni Cu)
2
47
61
9
13
40 54
8
12
Elemental analysis: Expected % C: 49.49, H: 5.39, N:
1.05, % Ni: 10.27, Cu: 5.57; Found % C: 47.98, H: 4.75,
N: 10.63, Ni: 9.62, Cu: 5.74.
Elemental analysis: Expected % C: 47.12, H: 5.34, N:
10.98, Ni: 11.48, Cu: 6.27; Found % C: 46.59, H: 5.13, N:
10.66, Ni: 11.07, Cu: 6.92.
1
-
1
-1
Important IR data (cm ): mN–H: 3167–3140, mC–H(Ar):
3043–3021, mC–H(Aliph): 2918–2868, mC=O(DMF): 1658,
Important IR data (cm ): mC–H(Ar)
mC–H(Aliph) 2931–2839, mC=O(DMF) 1672, mC=N:1630,
mC=C(ring): 1595, mN=O: 1438–1328, dCH2: 1473, mC–O(Phenol)
244–1134, dC–H(Ar): 750.
:
3055–3020,
:
:
:
mC=C(ring): 1598, mN=O: 1425–1396, dCH2: 1483, mC–O(Phenol)
:
1
1274–1257, dC–H(Ar): 750.
H
H
Preparation of the complexes with reduced Schiff base,
complex VI–IX
Complex VIII, [DMFÁNiL ÁNi(NO ) ÁNiL ÁDMF],
2
2
(C H N O Ni )
10
4
0
54
8
3
These complexes were synthesized by template method
according to the Scheme 1 and the literature [18, 24, 26, 44].
A quantity of 0.002 mol (0.572 g) the reduced Schiff base
Elemental analysis: Expected % C: 48.89, H: 5.54, N:
11.34, Ni: 11.39; Found % C: 48.53, H: 4.98, N: 11.18, Ni:
10.34.
0
bis-N,N (2-hydroxybenzyl)-1,3-propanediamine was dis-
-
1
Important IR data (cm ): mN–H: 3186–3144, mC–H(Ar)
3
:
solved in 40 mL DMF under heating and mixed. 1.0 mL
047–3033, mC–H(Aliph): 2938–2861, mC=O(DMF): 1655,
mC=C(ring): 1593, mN=O: 1413–1384, dCH2: 1481, mC–O(Phenol)
312–1280, dC–H(Ar): 756.
Et N and a solution of 0.002 mol (0.472 g) NiCl Á6H O in
3
2
2
:
2
0 mL hot MeOH were added to this solution. Then, for
1
complex VI 0.001 mol (0.170 g) CuCl Á2H O and
2
2
0
.002 mol (0.140 g) NaNO , for complex VII 0.001 mol
2
H
H
Complex XI, [DMFÁNiL ÁCu(NO ) ÁNiL ÁDMF],
3
2
(
(
2.41 g) Cu(NO ) Á3H O, for complex VIII 0.001 mol
3
2
2
(C H N O Ni )
40 54 8 12 3
0.236 g) NiCl Á2H O and 0.002 mol (0.140 g) NaNO and
2
2
2
for complex IX 0.001 mol (0.291 g) Ni(NO ) Á6H O were
3
2
2
Elemental analysis: Expected % C: 47.35, H: 5.36, N:
dissolved in 30 mL water–MeOH mixture (v/v: %50–%50)
using heating and mixed with the above mixture. The
resulting mixture was set aside for 4–5 days, and after this
period, the crystal products were filtered and dried in air.
The analytical results of these complexes are given below.
1
1
1.04, Ni: 17.35; Found % C: 46.87, H: 4.88, N: 10.57, Ni:
6.09.
-
1
Important IR data (cm ): mN–H
3036–3017, mC–H(Aliph): 2922–2858, mC=O(DMF): 1652,
:
3246, mC–H(Ar):
mC=C(ring): 1593, mN=O: 1419–1385, dCH2: 1481, mC–O(Phenol)
1313–1275, dC–H(Ar): 756.
:
H
H
Complex VI, [DMFÁNiL ÁCu(NO ) ÁNiL ÁDMF],
2
2
(
C H N O Ni Cu)
40 54 8 10 2
Elemental analysis: Expected % C: 48.64, H: 5.51, N:
1.34, % Ni: 11.85, Cu: 6.43; Found % C: 47.99, H: 5.08,
N: 10.97, Ni: 11.41, Cu: 5.96.
Results and discussion
1
As mentioned in introduction part, complexes including
nitrite and nitrate ions were reported in the literature as l-
bridge [15–18, 20]. Molecular models were determined by
X-ray diffraction in literature studies. Nitrate ion links Ni
(II) ions and central metal ions with two oxygen, while
-
1
Important IR data (cm ): mN–H: 3169–3143, mC–H(Ar)
041–3021, mC–H(Aliph): 2924–2858, mC=O(DMF): 1659,
mC=C(ring):1595, mN=O:1425, dCH2 1483, mC–O(Phenol)
284–1259, dC–H(Ar): 748.
:
3
:
:
1
123

N. Acar et al.
nitrite ion is linked to terminal Ni(II) ions with one oxygen
links to central metal ion via nitrogen atom. As mentioned
above, complex V was synthesized by using a different
Schiff base. Purpose of preparing this complex is to show
the condition of nitrate bridge once again in parallel to the
literature. For complex V, pluton drawing obtained by
X-ray diffraction works is given in Fig. 9. Crystallographic
data and experimental data of complex V, and important
angles and lengths around coordination sphere are given in
Tables 1 and 2, respectively.
Schiff bases, two thermal reactions are observed, and the
ones contained in DMF as solvate, three thermal reactions
are observed. On the other hand, complexes prepared by
reduced Schiff bases, only one thermal reaction was
observed. The first mass loss seen on the curves depicted in
red and green colors corresponds to one- and two-molecule
DMF existing as solvate. Second mass losses in Fig. 10 are
not clearly seen in the nitrite including complexes; how-
ever, it can be stated that these mass losses correspond to
two coordinative DMF existing in trinuclear complex.
Similar case can be seen on DTA curves. First endothermic
reactions observed in Fig. 11 belong to DMF molecules
existing as solvate, second endothermic signals belong to
separation of coordinative DMF molecules and last two
signals belongs to three thermal reactions of nitrite and
nitrate containing complexes. However, in Fig. 13, it is
seen that one thermal reaction is exothermic in four
complexes prepared with reduced Schiff base. Thermoan-
alytical data obtained from these curves are given in
Table 3.
As shown in Fig. 9, terminal ion Ni(II) exists between
two phenolic oxygen, two iminic nitrogen and one DMF
molecule oxygen and one nitrate oxygen O N donor
4
2
atoms, while central Cu(II) ion exists among four phenolic
oxygen and two nitrate oxygen in O coordination sphere.
6
As it can be seen, there are two different l-bridges as
phonologic oxygen and nitrates-constituted l-bridges.
Complexes prepared by LH2 vs L H are in similar
H
2
structure. Complexes I–V and other complex groups VI–IX
were examined by TG, and significant differences were
observed between TG curves. In Fig. 10, TG curves of I–
IV-numbered complexes are seen in a body, and DTA
curves of these materials are shown in Fig. 11 together. TG
curves of VI–IX-numbered complexes are shown in
Fig. 12, and DTA curves of these complexes are shown in
Fig. 13.
As shown in Figs. 10, 11 and Table 3 in Schiff base
complexes, the ones containing nitrite, DMF molecules are
separated from structure at 180–200 °C. In this case, there
is only NiL, and nitrite or nitrate salts are remained in the
environment. It is known that mixture of nitrite and nitrate
ions in organic material behaves as energetic material in
higher temperatures [45]. In this case, residual nitrite or
nitrate rapidly oxidizes a part of NiL mononuclear complex
As shown in Figs. 10 and 12, TG curves of both groups
are different from each other. In complexes prepared by
0
6
C24
C23
C25
0
25
C15
N5
N4
C19
C13
C17
0
4
02
C11
0
5
N2
01
NN i1
C18
C10
C9
C1
0
3
C2
C8
N1
C7
C20
C6
C5
C3
N3
C22
C4
C21
Fig. 9 {[DMFÁNiLACÁCu(NO
3
)
2
ÁNiLACÁDMF]ÁDMF} pluton drawing of complex V. One molecule exists as DMF solvate in crystal structure
1
23

The investigations of thermal behavior, kinetic analysis, and biological activity of trinuclear...
Table 1 Crystallographic and experimental data of complex V
Table 2 Selected bond length and angle values around of coordina-
tion sphere
-
1
Formula weight/g mol
47 61 9 2
C H N O13Ni Cu
˚
Bond length/A
Bond angles/°
T/K
100 (2)
N1 Ni1 2.087(5)
N2 Ni1 2.095(5)
N4 O4 1.251(8)
N4 O5 1.273(7)
N4 O25 1.505(10)
O1 Ni1 2.039(4)
O1 Cu1 2.069(4)
O2 Ni1 2.030(4)
O2 Cu1 2.052(4)
O3 Ni1 2.192(5)
O4 Ni1 2.016(4)
O5 N4 1.273(7) 3
O5 Cu1 2.095(4)
Cu1 O2 2.052(4)
Cu1 O1 2.069(4)
Cu1 O5 2.095(4)
O4 Ni1 O2 91.69(18)
O4 Ni1 O1 90.47(17)
O2 Ni1 O1 82.94(16)
O4 Ni1 N1 93.6(2)
Crystal size/mm
Crystal system
Space group
0.64 9 0.42 9 0.14
Monoclinic
1
P2 /c
˚
a/A
11.9957 (6)
15.2470 (7)
15.5784 (9)
90.00
˚
b/A
O2 Ni1 N1 172.48(18)
O1 Ni1 N1 91.63(18)
O4 Ni1 N2 94.3(2)
˚
c/A
Alpha
Beta
O2 Ni1 N2 90.68(19)
O1 Ni1 N2 172.1(2)
N1 Ni1 N2 94.3(2)
96.615 (7)
90.00
Gamma
3
˚
V/A
2830.3 (3)
2
O4 Ni1 O3 175.44(17)
O2 Ni1 O3 92.55(18)
O1 Ni1 O3 91.71(17)
N1 Ni1 O3 82.4(2)
Z
-
3
Calc. density/g cm
-
1.425
1
l/mm
F (000)
1.102
1270
N2 Ni1 O3 84.0(2)
Tmin–Tmax
0.5391–0.8611
2.95–28.24
-14 B hB13, -18 B kB19,
O2 Cu1 O2 180.0(2)
O2 Cu1 O1 81.67(16)
O2 Cu1 O1 98.33(16)
O2 Cu1 O1 98.33(16)
O2 Cu1 O1 81.67(16)
O1 Cu1 O1 180.0(2)
O2 Cu1 O5 93.21(17)
O2 Cu1 O5 86.79(17)
O1 Cu1 O5 93.91(16)
O1 Cu1 O5 86.09(16)
O2 Cu1 O5 86.79(17)
O2 Cu1 O5 93.21(17)
O1 Cu1 O5 86.09(16)
O1 Cu1 O5 93.91(16)
O5 Cu1 O5 180.0(3)
h Range/°
Index ranges
-19 B lB19
Reflections collected
Reflections unique
R1, wR2 (2 o´ )
5949
4249
0.1092, 0.3248
0.1313, 0.3448
5949/379
1.341
R1, wR2 (all)
Data/parameters
2
GOOF of F
Largest difference peak hole/ -1.337, 3.410
˚
e A
-3
CCDC No
1,481,757
and a reaction similar to explosion reaction is observed.
This explosion reaction is observed in nitrate complexes
(
complex II and IV) around 330 °C and is observed around
80 °C in nitrite complexes (complex I and III). This sit-
2
support this suggestion. In complexes prepared by Schiff
bases, DMF molecules are separated from structure in a
certain temperature range around 150–160 °C suggesting
that trinuclear complex is decomposed probably, and here,
the residual is NiL and nitrate salt. NiL could be prepared
as mononuclear complex and could be obtained as
uation arises due to possible nitrate and nitrite is coordi-
nated from different atoms. While complexes with nitrite
are coordinated on oxygen and nitrogen, nitrate complexes
are coordinated on two oxygen atoms. Same situation is
seen on reduced Schiff base complexes. Complexes
including nitrite (complex VI and VIII) give explosion
reaction around 230 °C, and complexes including nitrate
give explosion reaction around 260 °C. Mass loss observed
in reduced complexes is a little bit higher than Schiff base
complexes. Above-mentioned thermoanalytical data indi-
H
stable form. In reduced Schiff bases because NiL is not
stable structure, trinuclear complex can stand up to 250 °C
and decompose in this temperature with explosion reaction,
in this situation mass loss is a little bit higher comparing to
H
Schiff base complexes. Due to NiL is an unsta-
H
cate that mononuclear NiL complex is stable at some
H
reduced Schiff base complexes. One NiL complex could
ble mononuclear complex, trinuclear complex should be
more tensed and unstable compared to Schiff base com-
plexes. Thermokinetic calculations were done with this
consideration. Thermokinetic calculations were performed
according to Ozawa [29, 30], Ozawa–Flynn–Wall (OFW)
[31–35] and Kissenger–Akahira–Sunose (KAS) [33–37]
H
not be prepared between L H and Ni (II) ion. In spite of
2
H
this when L H was used, trinuclear complex was easily
2
H
prepared by template method. This situation shows L H2
ligand complexes are stable at trinuclear state. TG results
123

N. Acar et al.
1
00
100
80
60
40
20
0
8
6
4
2
0
0
0
0
0
0
100
200
300
400
500
600
700
Temperature/°C
0
100 200 300 400 500 600 700
Temperature/°C
Fig. 10 TG curves of complexes I–V. Black [DMFÁNiLÁCu(NO
NiLÁDMF] (I), Red {[DMFÁNiLÁCu(NO ÁNiLÁDMF]DMF} (II),
Blue [DMFÁNiLÁNi(NO ÁNiLÁDMF] (III), Green {[DMFÁNiLÁ
Ni(NO Á
ÁNiLÁDMF]2DMF} (IV), Pink [DMFÁNiLACÁCu(NO
NiLACÁDMF]. (Color figure online)
2
)
2
Á
H
3
)
2
Fig. 12 TG curves of complexes VI–IX. Black [DMFÁNiL Á
H
H
H
2
)
2
Cu(NO ) ÁNiL ÁDMF] (VI), Red [DMFÁNiL ÁCu(NO ) ÁNiL ÁDMF]
2
2
3 2
H
H
3
)
2
)
3 2
2 2
(VII), Blue [DMFÁNiL ÁNi(NO ) ÁNiL ÁDMF] (VIII), Green
H
H
[DMFÁNiL ÁNi(NO ) ÁNiL ÁDMF] (IX). (Color figure online)
3
2
100
100
50
50
0
0
0
100
200
300
400
500
600
0
100
200
300
400
500
600
Temperature/°C
Temperature/°C
H
Fig. 13 DTA curves of complexes VI–IX. Black [DMFÁNiL Á
Fig. 11 DTA curves of complexes I–V. Black [DMFÁNiLÁCu(NO
NiLÁDMF] (I), Red {[DMFÁNiLÁCu(NO ÁNiLÁDMF]DMF} (II),
Blue [DMFÁNiLÁNi(NO ÁNiLÁDMF] (III), Green {[DMFÁNiLÁ
Ni(NO
ÁNiLÁDMF]2DMF} (IV), Pink {[DMFÁNiLACÁCu(NO
NiLACÁDMF]DMF}. (Color figure online)
2
)
2
Á
H
H
H
Cu(NO
2
)
2
ÁNiL ÁDMF] (VI), Red [DMFÁNiL ÁCu(NO
3 2
)
ÁNiL ÁDMF]
3 2
)
H
H
(
[
VII), Blue [DMFÁNiL ÁNi(NO
2
)
2
ÁNiL ÁDMF] (VIII), Green
2 2
)
H
H
DMFÁNiL ÁNi(NO
3 2
)
ÁNiL ÁDMF] (IX). (Color figure online)
3
)
2
3
)
2
Á
KAS:
ꢀ
ꢁ
ꢀ
ꢁ
ꢁ
ꢀ
ꢀ
ꢁ
equations; isothermal calculations were done according to
Coats–Redfern (CR) equations from non-isothermal methods.
Equations used in these calculations are given as follows:
b
T2
AEa
Ea
In
¼ In
À
À
RgðaÞ
RT
Ozawa:
Coats–Redfern:
ꢀ
ꢁ
ꢀ
ꢁ
ꢀ
ꢁ
ꢀ
ꢁ
AEa
Ea
gðaÞ
AR
Ea
log b ¼ log
À 2:315 À 0:4567
In
¼ In
2
RgðaÞ
RT
T
bEa
RT
OFW:
-
1
where b is a heating speed as °C min , R universal gas
constant, E thermal disintegration activation energy, A
ꢀ
0
ꢁ
ꢀ
ꢁ
a
:0048AEa
RgðaÞ
Ea
Arrhenius pre-exponential factor, T temperature in K, g(a)
fractional completed fraction of thermal fracture reaction.
Inb ¼ In
À 1:0516
RT
1
23

The investigations of thermal behavior, kinetic analysis, and biological activity of trinuclear...
These equations were generated considering reaction order
n = 1 and realized as mentioned above.
Asolid ! Bsolid þ Cgas
-
1
For Coats–Redfern equation, b = 10 °C min
and
g(a) value were calculated between 0.1 and 0.9 and cal-
culations were made by graphic assistance. In application
of non-isothermal methods, b value changed in the range
-
1
of 5, 10, 15, 20, 25 °C min and graphical results were
obtained. On software of TG device, there is extra software
for Ozawa method; for that reason, Ozawa results were
calculated from software of device (TA Workstation,
TA60 kinetic analysis Program, version 2.01, Shimadzu
Corp.). But software gave error signal for nitrite and nitrate
ion explosions.
FOW and KAS methods were performed by manipu-
lation. But since temperature change showed anomaly for
explosion reactions of nitrite and nitrate ions, g(a) calcu-
lation was able to be done by taking the values between
0.05–0.18 and 0.85–0.95. Results calculated according to
four methods are given in Tables 6 and 7. As shown in
Fig. 10 and Table 3 for complexes prepared from Schiff
bases (I–IV), there are two thermal reactions: First reaction
is the separation of coordinative DMF molecules and
second reaction is the explosion reaction of nitrite and
nitrate. These values were calculated for both reactions.
From the above equation, E and A values could be cal-
a
culated. Thermodynamic parameters in thermal reaction
could be calculated by using these values.
ꢀ
ꢁ
Ah
kT
DS ¼ 2:303 log
R
DH ¼ E À RT
a
DG ¼ DH À TDS
Separation of coordinative DMF molecules reaction
only exists for I–IV-numbered complexes as it is shown in
Fig. 10 as well. The results found by the above equations
for the DMF thermal separation reaction are given in
Table 4. According to the method, E and A values were
a
calculated different for this DMF separation reaction. By
the way, three Arrhenius pre-exponential constant value
(A) is significantly different compared to others; A value
calculated with OFW method for complex I, A value cal-
culated with KAS method for complex II and A value
calculated with CR equation for complex IV are also found
significantly different; other values are in comparable sizes.
As shown in Table 4, Ozawa software gave no results
for complex II, IV and VII. Only two of results, complex I
-
1
and Complex VI (respectively, 123 and 113.35 kJ mol
,
1
.76.10 min ), obtained from Coast–Redfern equation
1
-1
1
could be comparable with other results for E and A values.
a
Other values calculated by Coats–Redfern equation are
123

N. Acar et al.
significantly higher; Ea and A values were calculated
higher, and as a result, other thermodynamic parameters
are calculated different. In explosion reaction of nitrate and
nitrite ions, Ozawa method and OFW methods gave quite
similar results. Only if E values are compared, OFW and
a
Ozawa obtained from KAS method is similar, but A value
calculated with KAS is as small as not comparable.
Values specified in Table 5 are the rates which were
calculated for explosion reaction of nitrite and nitrate ions
with an organic substance. Ozawa software did not give
any result for three complexes. These are complexes con-
taining nitrate. As it is known nitrate and nitrite ions are
oxidizing ions, they oxidize organic substance with organic
substance rapidly and cause rapid explosive reaction. First
explosive substance black powder contains nitrate salt,
coal dust and elemental dust sulfur in [45]. Nitrate includes
more oxygen atom, and for that reason, mass loss and
liberated energy in nitrated complexes are more in explo-
sion reaction and this situation is shown in Figs. 10, 11 and
Table 3. Gas product amount is expected to be excessive in
nitrate complex explosion reactions, since it is a rapid
reaction during the diffusion of these gas products, tem-
perature distribution around pan is contrary to expectation.
Temperature increases in a short time during explosion.
But gas product amount is high, and during the diffusion of
gas molecules around pan, temperature is decreased again
which is a result of heat transfer of these gas molecules.
This situation creates an anomaly in TG curve. Figure 14
shows TG curve of {[DMFÁNiLÁNi(NO ) ÁNiLÁDMF]Á
3
2
2DMF}, complex IV, and Fig. 15 shows DTA curve in
detail. Here, there can be seen three reactions, first reaction
is a mass loss belonging to DMF’s which exist as solvate
separation; it has been occured between 73 and 122 °C.
Second thermal reaction belongs to coordinative DMF’s
loss and occured between 168 and 202 °C. Third thermal
reaction is explosion reaction. This explosion reaction was
occured between 325 and 342 °C. Mass loss at the
beginning of explosion reaction shows a negative slope as
expected. But as long as the reaction forwards, slope goes
through positive side because temperature does not
increase but decreases in contrary, because the gases
generated during the explosion and move away quickly and
this generated gases carry out the reaction heat from Pt
pan. For this reason, the temperature decreases during
explosion reaction. In DTA curve, extraordinary cycle is
observed instead a Gaussian-type signal. This situation is
clearly shown in Figs. 14 and 15. Two thermal reactions
were proceeded as expected. The mass loss increased with
temperature increases and expected TG curves were cal-
culated, but it is seen that mass loss and temperature
decreased in third thermal reaction. In parallel to this,
signals of first two thermal reactions are normal
endothermic signals in Fig. 15, but there is an anomaly in
1
23

The investigations of thermal behavior, kinetic analysis, and biological activity of trinuclear...
25
20
1
1
5
0
5
0
0
100
200
300
400
500
600
Temperature/°C
Fig. 14 TG curve of the complex IV ({[DMFÁNiLÁNi(NO
DMF]Á2DMF})
3
)
2
ÁNiLÁ
3
2
2
1
1
50
50
00
50
00
50
0
–50
0
100
200
300
400
500
600
Temperature/°C
Fig. 15 DTA curve of the complex IV ({[DMFÁNiLÁNi(NO
DMF]Á2DMF})
3
)
2
ÁNiLÁ
third thermal reaction signal. In this situation, according to
Ozawa, OFW or KAS method, graphics drawn between
g(a)’s proper values (0.2–0.8), the lines deviate from lin-
earity. For that reason, Ozawa software is failed. In spite of
this in graphics which were drawn according to another
methods, g(a) values were calculated by taking relatively
closer to limit values.
Our general remarks were summarized in results given
in Tables 4 and 5
1.
As mentioned before, coordinative DMF loss was
occurred as expected manner and observed as
endothermic reaction. Results which were found
according to four different methods for this thermal
reaction are comparable values to each other. There
are differences between the results calculated by these
methods, but this is a common situation for these semi-
experimental methods in the literature [32, 35]. Only
123

N. Acar et al.
Table 6 Calculated thermodynamic parameters for DMF removal reaction (first thermal reaction)
Complex Methods
Ozawa
Coats–Redfern
OFW
KAS
*
DH/
kJ mol
DS/
J K
DG/
kJ mol
DH/
kJ mol
DS/
J K
DG/
kJ mol
DH /
kJ mol
DS/
J K
DG/
kJ mol
DH/
kJ mol
DS/
J K
DG/
kJ mol
-
1
-1
-1
-1
-1
-1
-1
-1
-1
-1
-1
-1
I
155.26
101.35
169.92
109.16
-16.57 163.93
-41.60 127.67
-11.53 175.95
-89.41 155.92
130.01
163.44
137.14
151.71
26.90 116.75
99.04 101.74
46.47 112.84
254.79
78.45
266.67 123.32
-75.43 125.44
-11.26 118.82
-70.16 115.35
245.82
76.01
98.78 197.12
-238.29 224.46
-173.97 204.36
-75.05 150.25
II
III
IV
112.93
78.66
113.38
111.00
134.04
85.60
Table 7 Calculated thermodynamic parameters for explosion reactions of nitrite or nitrate ions (second thermal reaction)
Complex Methods
Ozawa
Coats–Redfern
OFW
KAS
DH/
kJ mol
DS/
J K
DG/
kJ mol
DH/
kJ mol
DH/
kJ mol
DS/
J K
DG/
kJ mol
DH/
kJ mol
DH/
kJ mol
DS/
J K
DG/
kJ mol
DH/
kJ mol
-
1
-1
-1
-1
-1
-1
-1
-1
-1
-1
-1
-1
I
137.62
126.63
124.91
-25.26 152.59
-79.92 173.42
37.13 104.00
118.56
478.44
279.42
228.15
108.67
510.67
364.77
514.91
-32.90
546.18
254.54
115.81
-34.91
615.66
441.31
708.68
138.07 131.89
154.55 154.50
128.47 138.66
159.47 107.44
129.37 114.03
145.58 120.63
103.07 120.58
94.66 126.64
18.47
-30.17
-21.28
-73.11
28.82
122.86
169.07
149.19
142.82
98.69
114.75 -203.33 214.18
161.20 -141.13 240.66
104.76 -223.71 215.49
103.81 -240.21 220.07
111.14 -177.16 205.39
118.19 -191.43 225.96
111.45 -202.08 229.06
123.61 -192.77 243.44
II
III
IV
VI
VII
VIII
IX
-44.17
-36.14
-6.54
145.49
141.61
130.78
119.52
141.12
-72.98 161.33
1.89 139.99
Arrhenius pre-exponential factor values that were
calculated by KAS method are different from others.
Due to loss of DMF was observed on Schiff base
complexes (complexes I–IV), it is not possible to
compare these results with reduced Schiff base results.
Explosion reaction caused by nitrate and nitrite ions
was seen at all eight complexes too. As mentioned
before, due to explosion is severe in complexes containing
nitrate and TG curves showed anomaly, calculations were
performed only at higher g(a) values. As shown in
Table 5 according to Coats–Redfern equation, calculated
values are higher than others, Arrhenius pre-exponential
constant values are at unacceptable sizes. Ozawa and
calculated by thermokinetic methods is expected to be
lower. Study was carried out in order to support this
suggestion. But due to explosion reactions did not give
expected TG curve, robust comparison results were not
calculated. However, E values which were calculated with
a
2
.
Ozawa, OFW and KAS method supports this suggestion.
Average E values in Schiff base complex explosion
a
reactions were, respectively, according to Ozawa method
-
1
134.59, OFW method 137.18 ± 19.57 kJ mol and KAS
-
1
method 135.16 ± 23.84 kJ mol ; however, these values
in reduced Schiff base complexes were calculated, respec-
-
1
tively, Ozawa method 126.94 kJ mol , OFW method
-
1
125.15 ± 5.11 kJ mol
and KAS method 120.89 ±
-1
OFW results are overlapped; in E , results obtained by
a
6.22 kJ mol . Standard deviations are higher, and E
a
KAS method are comparable sizes with these values, but
Arrhenius pre-exponential constant values that were
calculated by KAS are not acceptable again. Purpose of
this study was to determine the strains of two different
species by comparison. Because while NiL has been able
to synthesized and isolated, it was not possible to isolate
values which were calculated in reduced Schiff
base complexes are lower as expected. But it is not
possible to calculate this on explosion reactions clearly
with these methods because TG curve shows anomaly.
Tables 6 and 7 show the calculated thermodynamic
parameters using the E and A values.
a
H
NiL and still trinuclear complexes of both mononuclear
H
complexes have been able to prepare. If NiL had a
It was also considered that these complexes exhibit
antimicrobial activity. To investigate the difference in
biological activities for two different complex types, we
strain, this instability should have been in trinuclear
complexes. In this situation, Ea value which was
1
23

The investigations of thermal behavior, kinetic analysis, and biological activity of trinuclear...
Fig. 16 Biological activity of
the complexes prepared, C1,
complex I; C2, complex II; C3,
complex III; C4, complex IV; C5,
complex VI; C6, complex VII
and C8, complex IX
E. coli
1.5
1
5
mg
2.5 mg
.25 mg
0.5
1
0
C1
C2
C3
C4
C5
C6
C8
0.625 mg
0.312 mg
Compounds (C)
P. aureginosa
1
0
.5
1
5
mg
.5 mg
.25 mg
0.625 mg
.312 mg
2
.5
0
1
C1
C2
C3
C4
C5
C6
C8
Compounds (C)
0
S. aureus
1
0
.5
1
5
2
mg
.5 mg
.5
0
1
.25 mg
0
.625 mg
.312 mg
C1
C2
C3
C4
C5
C6
C8
0
Compounds (C)
E. feacalis
2
5
mg
1
0
2
.5 mg
1
0
.25 mg
C1
C2
C3
C4
C5
C6
C8
.625 mg
Compounds (C)
1
.5
5
2
mg
1
.5 mg
0.5
1
.25 mg
0.625 mg
.312 mg
0
C1
C2
C3
C4
C5
C6
C8
Compounds (C)
0
performed antibacterial and antifungal activity experi-
ments. As mentioned above, inhibitory effects of these
complexes analyzed against two gram-negative bacteria
antifungal effects of both group of complexes. Thermoki-
netic results show that there is a small difference between
two groups of complexes. But reaction that was examined
with kinetic analysis is an explosion reaction. No doubt TG
curve in explosion reactions was not good enough.
Therefore, not observing a big difference in biological
activity should be expected. If this study could be repeated
with anions other than nitrate and nitrite anions, result
would show clear comparison with respect to antimicrobial
activity.
(
E. coli and P. aureginosa), two gram-positive bacteria (S.
aureus and E. feacalis) and one fungus (C. albicans).
Results belonging to eight complexes against above-men-
tioned microorganisms are given in Fig. 16.
As shown in Fig. 16, there has been inhibitory effects
observed against bacterial species and a fungus yet there is
no significant difference between antibacterial and
123

N. Acar et al.
1
1
1
4. Biswas S, Ghosh A. Use of Cu(II)-di-Schiff bases as metalloli-
gands in the formation of complexes with Cu(II), Ni(II) and
Zn(II) perchlorate. Polyhedron. 2013;65:322–31.
Conclusion
Totally eight trinuclear complexes were prepared from two
different groups where nitrate and nitrite ions exist as l-
bridge and thermokinetic parameters were determined by
four different methods isothermally and non-isothermally.
Obtained data compared and stability among groups was
researched. Small difference was determined between
activation energies, but this difference was not calculated
at biological activities. As a result, it was concluded that
trinuclear complexes in some cases are more stable than
mononuclear units.
¨
0
5. Arıcı C, Ulk u¨ D, Atakol O. Bis{(N,N -dimethylformamide) (l-
formato)[l-bis(salicylidene)-1,3-propanediaminato)] nickel(II)}-
cobalt(II). Anal Sci. 2002;18:959–60.
6. Ercan F, Ate s¸ BM, Durmu s¸ S, Atakol O. Structural analysis of
bis{(B,N’-dimethylformamide)(l-formato)[l-bis(salicylidene)-
1
,3-propanediaminato]nickel(II)}copper(II) and zinc(II) mono-
hydrate hetero-trinuclear complexes. Cryst Res Tecnol.
004;39:470–6.
2
1
7. Chen YN, Ge YY, Zhou W, Fang L, Gu ZG, Ma GM, Li WS. The
first Mn–Zn heterometallic dinuclear compound based on Schiff
0
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1
8. Akay A, Arıcı C, Atakol O, Fuess H, Svoboda I. Synthesis,
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