Thermal behaviors and decomposition kinetics of a Ni(II) complex with 2-pyridinecarboxylic acid

Article abstract of DOI:10.1080/15533170802683230

A Ni(II) complex with 2-pyridinecarboxylic acid, [Ni (C6H4NO2)2(H2O)2] 2H2O, has been synthesized and its thermal decomposition in N2 atmosphere has been investigated by TG-DTG and DSC. The results show that the thermal decomposition process of this compl

Full text of DOI:10.1080/15533170802683230

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Thermal Behaviors and Decomposition Kinetics of a
Ni(II) Complex with 2-Pyridinecarboxylic Acid
a
b
b
b
Xiao-Qing Shen , Zhong-Jun Li , Ya-Li Niu & Hai-Bin Qiao
a
College of Materials Science and Engineering , Zhengzhou University , Zhengzhou,
China
b
Department of Chemistry , Zhengzhou University , Zhengzhou, China
Published online: 09 Mar 2011.
To cite this article: Xiao-Qing Shen , Zhong-Jun Li , Ya-Li Niu & Hai-Bin Qiao (2009) Thermal Behaviors and Decomposition
Kinetics of a Ni(II) Complex with 2-Pyridinecarboxylic Acid, Synthesis and Reactivity in Inorganic, Metal-Organic, and
Nano-Metal Chemistry, 39:1, 55-59
To link to this article: http://dx.doi.org/10.1080/15533170802683230
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Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 39:55–59, 2009
Copyright © Taylor & Francis Group, LLC
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533170802683230
Thermal Behaviors and Decomposition Kinetics of a Ni(II)
Complex with 2-Pyridinecarboxylic Acid
1
2
2
2
Xiao-Qing Shen, Zhong-Jun Li, Ya-Li Niu, and Hai-Bin Qiao
1
College of Materials Science and Engineering, Zhengzhou University, Zhengzhou, China
Department of Chemistry, Zhengzhou University, Zhengzhou, China
2
by 2-pyridinecarboxylic acid. The kinetic parameters of thermal
Ni(II) complex with 2-pyridinecarboxylic acid, [Ni decomposition have been calculated by means of non-isothermal
NO (H O) O, has been synthesized and its thermal method and the reaction model has been derived by means of
decomposition in N
A
(
C
6
H
4
2
)
2
2
2
]·2H
2
2
atmosphere has been investigated by TG-DTG
multivariate non-linear regression.
and DSC. The results show that the thermal decomposition process
of this complex can be divided into two transitions: one is assigned
to water loss (involving crystal lattice water and coordinated wa-
ter) and another to the main decomposition of destroying Ni−N
bonds, Ni−O bonds and pyridine ring. Thermal decomposition ki-
netic analysis indicates that both the transitions are double-step
following reactions with different singular reaction types. The ki-
EXPERIMENTAL
Preparation of [Ni(C6H4NO2)2(H2O)2]·2H2O (Complex 1)
An aqueous solution of 0.024 g (0.01 mmol) NiCl2·6H2O was
netic parameters of thermal decomposition have been obtained by added with continuous stirring to 20 ml of CH3OH containing
means of model-free method together with multivariate non-linear 0.021 g (0.2 mmol) of 2-pyridinecarboxylic acid. The resulting
regression.
solution was heated under stirring to reflux for 1 h and then
cooled to room temperature. After five days, bright blue crystals
of title complex suitable for X-ray diffraction were obtained
by being filtrated, washed with cooled water and dried under
Keywords 2-pyridinecarboxylic acid, decomposition, kinetics,
thermal behavior
vacuum. IR (KBr): 3448, 1576, 1595, 1545, 1460, 1377, 1362,
−
1
7
00 cm .
INTRODUCTION
In recent years many reports keep an eye on the synthesis, an-
tibiotic activities, catalytic activities and structural elucidation
of various organo derivatives of pyridine due to their impor-
tance in biological system and their applications in anti-tumor
Instrumentation
Single crystal structure was determined by a Rigaku-Raxis-
IVX-ray diffractometer using graphite-monochromated Mo Kα
radiation (λ = 0.71073 A˚ ) at 293(2)K.
[
1−3]
agents of chemotherapy.
In particular, as a species of super
Thermal decomposition experiments were carried out using
Netzsch TG 209 and DSC 204 instruments in nitrogen atmo-
ligand, pyridines can coordinate many metal ions to form com-
plexes through nitrogen atoms. Some of these complexes are
−1
sphere with flow rates of 20 and 70 mL min , respectively.
provided with various structure characteristics and have spe-
◦
◦
cial applications in medicine and catalysis fields.[4] Because of
The heating rate for thermal decomposition employed was 10 C
−
1
min , and the rates for kinetic analysis were 5, 10, 15 and 20 C
their activity, substituted pyridines such as 2-pyridinecarboxylic
acid, which is formed by the introduction of carboxyl, have been
widely studied in the fields of synthesis, structure identification
−1
min , respectively. IR spectra were recorded on a Nicolet IR-
4
cm
70 spectrometer using KBr pellets in the range of 4000–400
−1
[
5,6]
.
and chelating property studies.
However, the thermal behav-
iors and decomposition kinetics of these compounds are rare
to literature. In this paper, we report the thermal analysis of
complex [Ni(C6H4NO2)2(H2O)2]·2H2O, which is constructed
RESULTS AND DISCUSSION
Crystal Structure
The crystal structure of complex 1 was found to be a mon-
oclinic system with a = 2.5282 (5), b = 0.59083 (12), c =
Received 12 January 2008; accepted 30 August 2008.
Address correspondence to Xiao-Qing Shen, College of Materials
Science and Engineering, Zhengzhou University, Zhengzhou 450052,
China. E-mail: shenxiaoqing@zzu.edu.cn
˚
◦
1
.5390 (3) A and β = 113.88 , the result of which was the
[7]
same as that reported before. The structure drawing given in
Figure 1 describes the coordination environment of Ni atom.
55

56
X. Q. SHEN ET AL.
FIG. 3. DSC curve of complex 1.
−
1
FIG. 1. Structure drawing of complex 1.
total ꢀHvalue of 393.6 Jg , with a consecutive weight loss
◦
in TG curve and two associated DTG peaks at 331 and 399 C
It can be seen that two 2-pyridinecarboxylic acid molecules can be attributed to the breaking of coordination bonds (Ni N,
chelate Ni atom using their O and N atoms to form the plane Ni O) and the destruction of pyridine ring. Total mass loss of
◦
of a distorted octahedron, and two H2O molecules occupy the 70.44% up to 500 is less than the calculated value of 80.08%
axis direction. Two other H2O molecules connect the structure by taking NiO as the final product, which is because of the
unit through hydrogen bonds (O2-H. O4). A hydrogen bond carbon deposition resulted from decomposed products in N
2
is weaker than coordination bond, but it also plays an important atmosphere.[
8]
role in the construction of crystal units and would provide extra
stability to the whole structure.
It is of interest to further investigate the enthalpy changes
of this complex in first transition. Two slightly overlapped
endothermic peaks appeared in DSC curve with the peak
◦
Thermal Decomposition of Complex 1
temperatures at 102 and 167 C, giving total ꢀH value of
−1
The typical TG–DTG and DSC curves of complex 1 are 630.6 Jg (see Figure 3), correspond to the removal of two crys-
shown in Figures 2 and 3, respectively. Two transitions appeared tal lattice water and two coordinated water, respectively. We use
in the decomposition process. The first transition, which starts the peak-separation technology to calculate the ꢀH value of
◦
◦
from 50 C and ends at 180 C, is a consecutive weight loss pro- each peak. The calculated curves are presented in Figure 4, and
◦
cess containing two endothermic peaks at 102 and 167 C and the calculated results shown in Table 1. The ꢀH values given
two DTG peaks at 98 and 165 C. This thermal event, giving a to- for these two endothermic peaks are 286.5 and 324.6 Jg , re-
tal ꢀH value of 630.6 Jg , is due to the removal of water from spectively. It can be seen that two types of bonding mode result
complex 1. The calculated mass loss of 19.18% for this thermal in these water being lost at different temperatures and the heat
event agrees well with that revealed by the TG curve (19.02%). absorbed for eliminating crystal lattice water is less than that
◦
−1
−
1
◦
The second transition, which ranges from 313 to 430 C, is re- absorbed for eliminating coordinated water.
lated to the thermal decomposition of [Ni(C6H4NO2)2]. The two
◦
consecutive endothermic peaks at 321 and 401 C involving a
FIG. 2. TG-DTG curve of complex 1.
FIG. 4. Peak-separation for first transition of DSC curve.

THERMAL BEHAVIORS AND KINETICS OF A NI(II) COMPLEX
57
TABLE 1
Peak-separation results for the first transition of decomposition
TABLE 2
Parameters E and lgA for the thermal decomposition of title
complex by using OFW analysis
◦
◦
◦
Area /Jg1
Shape
Position/ C
Onset/ C
Endset/ C
Partial
mass
First transition
Second transition
1
2
95.4571
165.3691
56.409
135.347
119.425
177.593
286.4991
324.6029
−1
−1
E /(kJ·mol−1
−1
lg(A/s )
loss (α) E/(kJ·mol ) lg(A/s
)
)
0.02
0.05
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
0.98
62.76 ± 5.73
55.06 ± 3.18
50.52 ± 2.19
47.07 ± 1.40
45.49 ± 1.41
45.11 ± 1.65
49.50 ± 3.71
71.17 ± 5.75
69.39 ± 3.15
67.64 ± 2.76
65.61 ± 3.65
64.50 ± 6.24
6.30
186.48 ± 23.79 12.56
5.19
4.56
4.09
3.87
3.90
4.36
6.85
6.48
6.23
6.01
1.96
137.41 ± 4.41
177.16 ± 2.57
201.66 ± 1.67
209.38 ± 1.66
213.89 ± 4.01
218.24 ± 6.57
221.97 ± 8.93
8.15
11.49
13.55
14.21
14.60
14.98
15.29
Non-Isothermal Kinetics of Thermal Decomposition
Model-Free Estimation of Activation Energy
A series of dynamic scans with different heating rates results
in a set of data, that exhibits the same degree of conversion
(
α) at different temperatures. Based on this, two methods are
developed by Friedman as well as Ozawa-Flynn-Wall (OFW) to
determine the kinetic parameters without having to presuppose
a certain model. Figure 5 shows the TG curves of complex 1
224.92 ± 12.11 15.56
224.87 ± 15.22 15.60
230.69 ± 25.08 16.11
258.37 ± 26.42 18.25
◦
decomposition from 35 to 460 C with the heating rate of 5, 10,
1
◦
−1
5 and 20 C min , respectively. The basic data (β, α, T ) taken
from the TG curves are used in the equations below:
[9]
Ozawa-Flynn-Wall equation
with slopes m(1) = −1.052 E/R and m(2) = −E/R, respectively.
The slopes of these straight lines are directly proportional to the
reaction activation energy (E). The calculated results obtained
by using both Equations are shown in Table 2 and 3, respectively.
The comparable values ofE and lgA of each transition by us-
ing different methods indicates that the kinetic parameters thus
obtained are reasonable, and furthermore, the dependence of ac-
ꢀ
ꢁ
AE
E
ln β = ln
− ln g(α) − 5.3305 − 1.052 ·
[1]
R
RT
where β is heating rate, α degree of conversion, g(α) mechanism
function, E activation energy, A pre-exponential factor and R
gas constant.
Friedman equation,[10]
tivation energy on the degree of conversion (E -dependence),
α
given in Tables 2 and 3, shows that the activation energy is not a
ꢀ
ꢁ
constant. Two maximums appear with the extent of decomposi-
tion, which betokens that the two transitions of thermal decom-
dα
dt
E
ln
= ln[A · f (a)j ] −
[2]
RT
α=αj
[11]
position of title complex both are double-step reactions.
where dα/dt is the rate of conversion, and f (α) mechanism
function.
TABLE 3
From Equations (1) and (2), it is seen that the graphs lnβ
versus 1/T and ln (dα/dt) versus 1/T both show straight lines
Parameters E and lgA for the thermal decomposition of title
complex by using Friedman analysis
Partial
mass
First transition
Second transition
loss (α) E/(kJ·mol 1) lg(A/s−1) E /(kJ·mol−1) lg(A/s
−
−1
)
0.02
0.05
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
0.98
46.89 ± 1.64
44.92 ± 1.72
43.03 ± 1.76
3.99
91.51 ± 32.72
4.44
3.78 183.11 ± 1.85
11.89
15.08
15.50
15.31
3.56 221.17 ± 2.72
41.71 ± 2.023 3.38 225.21 ± 5.32
45.17 ± 2.39
48.49 ± 3.29
3.85 222.14 ± 9.91
4.23 228.44 ± 14.64 15.85
69.42 ± 10.10 6.57 234.20 ± 14.95 16.31
69.91 ± 0.44
67.80 ± 0.48
64.02 ± 3.59
61.13 ± 8.56
6.20 234.79 ± 17.14 16.38
6.11 235.74 ± 23.56 16.49
5.83 235.67 ± 30.09 16.55
5.68 256.55 ± 49.75 18.23
73.97 ± 23.59 7.35 311.67 ± 28.44 22.32
FIG. 5. TG curves with different heating rates.

58
X. Q. SHEN ET AL.
TABLE 4
Kinetic parameters and fitting quality after nonlinear regression
Transition Corr. Coeff. Reg. Par. Step E (kJmol−1) lg (A/s−1
)
Foll. React.
0.47698
1st
0.998804
0.999876
0.00100 I R3
II F1
54.89332
97.59743
124.28316
268.73316
5.14834
9.72111
7.98461
2nd
0.00100
I F1
II F1
19.07224
0.11801
Kinetic parameters of a reaction can be estimated from
In short, the results of the kinetic analysis above show that
the maximums of Friedman method or OFW method, also the thermal decomposition of [Ni(C6H4NO2)2(H2O)2]·2H2O
from the average values of the two methods. According to preferably performs as two double-step following reactions.
−
1
−1
OFW method, the activation energies and pre-exponential fac- In the first transition: E1 = 55 kJmol , lg (A1/s ) = 5.2;
−1
−1
tors of thermal decomposition of title complex are E1 = E1 = 98 kJmol , lg (A1/s ) = 9.8. In the second transition:
−
1
−1
−1
−1
−1
−1
−1
6
2 kJmol , lg (A1/s ) = 6.3, and E2 = 69 kJmol
,
,
E1 = 124 kJmol , lg (A1/s ) = 7.8; E2 = 269 kJmol , lg
−1
−1
lg(A2/s ) = 6.5 for first transition, while E1 = 186 kJmol
(A1/s ) = 19.1.
−
1
−1
−1
lg (A1/s ) = 12.6, and E2 = 258 kJmol , lg(A2/s ) = 18.3
for the second, respectively. The values of these parameters
would offer initial values for getting reaction model by means
[12]
of non-linear regression (NLR)
finally.
and would be optimized
Multivariate Non-Linear Regression (NLR)
Mode-free method has solved the problem of kinetic pa-
rameters and these data can be used to estimate potential
model on which the reaction occurred. NLR allows a direct
fit of the model to the experimental data without a trans-
formation and there are no limitations with respect to the
complexity of the model. For this reason, NLR method can
be used and iterative procedures can be employed for es-
timating of the reaction model of a thermal decomposition
process.
Selecting mechanism function f (α) of different singular re-
action types;[ testing all two-step reaction types to which in-
dividual steps are linked as consecutive (d:f), parallel (d:p) and
independent (d:i);[ setting the initial values of the parameters
of E and lgA according to mode–free method, the calculation
of the regress values is carried out. To minimize the deviance,
least squares (LSQ) method is used and a smooth convergence
is ensured.
13]
13]
The calculated curves were obtained by means of NLR. These
curves were fitted to the experimental ones and corrected with
least-squares procedure. During this procedure in order to get
high fitting quality kinetic parameters of initial values are op-
timized. Considering fitting quality (characterized by correla-
tion coefficient and relative precision), the mechanism of d:f,
R3
F1
A−→ B−→ C, is the most suitable for the reaction of the first
F1
F1
transition, and d:f, A−→ B−→ C, is the most suitable for that
of the second one. The kinetic parameters and statistical char-
acterization after the NLR are listed in Table 4 and graphic
presentations of the curve fitting are shown in Figure 6(a) and
FIG. 6(a). Curve fitting of first transition, simulated with reaction types R3
and F1. ∇,♦, ꢀ,ꢁ experimental plots, — integral plots.
(b). From Figure 6 it can be seen that the experimental data and
(b) Curve fitting of second transition, simulated with reaction types F1 and F1.
the nonlinear regression model fit very well.
∇, ♦, ꢀ, ꢁ experimental plots, — integral plots.

THERMAL BEHAVIORS AND KINETICS OF A NI(II) COMPLEX
59
CONCLUSIONS
3. Pahor, N.B., Nardin, G., Bonomo, R.P., and Rizzarelli, E. Properties and
ꢁ
ꢁ
ꢁꢁ
structural characterization of copper(II) mixed complexes with 2,2 :6 ,2 -
terpyridyl and iminodiacetate or pyridine-2,6-dicarboxylate. J. Chem. Soc.,
Dalton Trans., 1984, 2625.
1. Thermal analysis indicates that the process of
[
Ni(C6H4NO2)2(H2O)2]·2H2O decomposition includes
two transitions. The first transition is assigned to the loss
of water; the second corresponds to the decomposition of
4
. Batten, S.R., Harris, A.R., Jensen, P., Murray, K.S., and Ziebell, A.
Copper(I) dicyanamide coordination polymers: ladders, sheets, layers,
diamond-like networks and unusual interpenetration. J. Chem. Soc., Dalton
Trans., 2000, 3829.
[
Ni(C6H4NO2)2]. Two types of bonding mode result in the
crystal lattice water and the coordinated water being lost at
different temperatures.
5
. Wang, Q.M., Wu, X.T., and Zhang, W.J. Solids with rhombic channels:
ꢁ
syntheses and crystal structures of [Cu3(NTA)2(4,4 -bpy)2(H2O)2]·9H2O
2. Kinetic analysis shows that the thermal decomposition of
ꢁ
ꢁ
and [{Cu(4,4 -bpy)(H2O)4}{Cu2(NTA)2(4,4 -bpy)}]·7H2O (NTA = Ni-
ꢁ
ꢁ
[
Ni(C6H4NO2)2(H2O)2]·2H2O preferably performs as two
trilotriacetate, 4,4 -bpy = 4,4 -Bipyridine). Inorg. Chem., 1999, 38,
double-step following reactions. The first one for water
2223.
R3
F1
6. Chen H.J. Synthesis and structure characterization of tris-[diaqua-(pyridine-
loss is in a mode of d:f, A−→ B−→ C: a 3-dimensional
2
7
,6-dicarboxylato)copper(II)]. Chinese J. Jinan Univ., 2002, 23(1),
5.
−1
phase boundary reaction (R3) with E1 = 55 kJmol , lg
−
1
(
A1/s ) = 5.2, is followed by a 1st order reaction (F1) with
7. Yuan, Q., and Liu, Y.H. Synthesis and crystal structure of nickel (II) complex
with picolinic acid. Chinese J. Chem. Res., 2003, 14(3), 35.
8. Shen, X.Q., Zhong, H.J., Zheng, H., and Zhang, H.Y. Crystal struc-
ture, thermal decomposition kinetics and antimicrobial activities of
[Zn(eatz)2(OAc)2] (eatz =5-ethyl-2-amino-1,3,4-thiadiazole). Polyhedron,
2004, 23(11), 1851.
−1
−1
E2 = 98 kJmol , lg (A2/s ) = 9.7; The second one for
F1
F1
main decomposition is d:f, A−→ B−→ C: an 1st order re-
−
1
−1
action (F1) with E1 = 124 kJmol , lg (A1/s ) = 8.0, is
−1
followed by a 1st order reaction (F1) with E2 = 269 kJmol
,
−1
9. Ozawa, T. A new method of analyzing thermogravimetric data. Bull. Chem.
Soc. Jpn., 1965, 38, 1881.
lg (A2/s ) = 19.1.
1
0. Friedman, H.L. Kinetics of thermal degradation of char-forming plastic
from thermogravimetery. Application to phenolic plastic. J. Polym. Sci.
Part C, 1963, 6, 183.
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