Study on coordination behaviour of manganese chloride with L-α-histidine

Article abstract of DOI:10.1023/B:JTAN.0000027176.44701.69

The reaction thermodynamic and kinetic equations for the non-reversible reactions are established. The enthalpy change of formation reaction of manganese(II) histidine (His) complex in water has been determined by microcalorimetry, using manganese chlorid

Full text of DOI:10.1023/B:JTAN.0000027176.44701.69

Journal of Thermal Analysis and Calorimetry, Vol. 75 (2004) 795–805
STUDY ON COORDINATION BEHAVIOUR OF
MANGANESE CHLORIDE WITH L-α-HISTIDINE
*
G. Shengli , C. Sanping, L. Huanyong, H. Rongzu and S. Qizhen
Shaanxi Key Laboratory of Physico-Inorganic Chemistry, Department of Chemistry,
Northwest University, Xi’an Shaanxi 710069, People’s Republic of China
(
Received May 6, 2003; in revised form December 2, 2003)
Abstract
The reaction thermodynamic and kinetic equations for the non-reversible reactions are established.
The enthalpy change of formation reaction of manganese(II) histidine (His) complex in water has been
determined by microcalorimetry, using manganese chloride with L-α-histidine at 298.15–323.15 K.
2
+
The standard enthalpy of formation of Mn(His) (aq) has been calculated. On the basis of experimen-
2
tal and calculated results, three thermodynamics parameters (the activation enthalpy, the activation en-
tropy and the activation free energy), the rate constants, along with three kinetic parameters (the ap-
parent activation energies, the pre-exponential constant and the reaction order) are obtained. The
results show that the reaction easily takes place over the studied temperature range. The solid complex
2 2 2
Mn(His) Cl ⋅4H O was prepared and characterized by IR and TG-DTG.
Keywords: complex, formation reaction, L-α-histidine, manganese chloride, thermokinetics
Introduction
Manganese is an essential trace element for the living organisms. It is involved in a va-
riety of matalloenzymes and participates in activating hundreds of other enzymes. En-
zymes activated by manganese ion are closely associated with elimination of radicals,
anti-aged, synthesis of amylose as well as procreation and growth. L-α-Amino acids
are structural units of proteins. A better understanding of the complex of manganese
and L-α-amino acids is thus of considerable practical and fundamental importance. It is
expected that a desired additive of manganese would generated from the complexes of
Mn(II) and amino acids. The complexes of manganese(II) and L-α-amino acids have
been widely investigated in the literatures. Simeonova have investigated the stability
constants and thermodynamic properties for the complexes of manganese with fifteen
amino acids [1–3]. Quay and Basosi studied the properties of the complexes of manga-
nese with amino acids in H O and D O by NMR and ESR [4, 5]. The catalytic activities
2 2
of the complexes in H O were discussed by Batry [6, 7], and the structure of the
2
2
*
Author for correspondence: E-mail: gaoshli@nwu.edu.cn
1
388–6150/2004/ $ 20.00
Akadémiai Kiadó, Budapest
©
2004 Akadémiai Kiadó, Budapest
Kluwer Academic Publishers, Dordrecht

7
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SHENGLI et al.: MANGANESE CHLORIDE WITH L-α-HISTIDINE
complex of alanine and bromide was illustrated by Giunik [8]. Recently, thermo-
chemistry behavior of solid complexes of Mn(His) Cl ⋅4H O was investigated in our re-
2
2
2
search group [9]. In addition, kinetics of thermal decomposition of manganese(II) oxa-
late was reported [10]. However, the thermochemical properties and the formation
thermokinetics of the complex of manganese and L-α-histidine have not been expounded
in literature.
In this manuscript, the enthalpy change of formation reaction of manganese(II)
histidine (His) complex in water has been determined by a microcalorimeter, using
manganese chloride with L-α-histidine at 298.15–323.15 K, fundamental parameters
for reaction of preparing manganese histidine complex, including the reaction rate
constant (k), the activation energy (E), the pre-exponential constant (A), the reaction
θ
≠
θ
≠
order (n), the activation enthalpy (∆H ), the activation entropy (∆S ), the activation
θ
θ
free energie (∆G ) and the enthalpy (∆ H ) were attained. The solid complex
Mn(His) Cl ⋅4H O was prepared and characterized by IR and TG-DTG.
≠
r
≠
2
2
2
Experimental
Derivation of thermokinetics equations for the non-reversible reaction
In order to build up thermokinetics equations for the non-reversible reaction, a gen-
eral mode of the reaction is depicted in following,
≠
A(aq)+B(aq) or B(s) ↔ [AB] →product+heat
t=0, c0=1
t=t, ci
c
α =0 H =0
0
0
αi
Hi
t=∞, c∞
α =1 H∞
¥
The relationship of reaction system energy with reaction process is attained
from boundary conditions,
c0 −ci 0−α i 0−Hi
=
=
(1)
c0 −c
∞
0−α ∞ 0−H∞
and
Hi
α=
(2)
(3)
H∞
dα
1 dHi
dt H∞ dt
=
Equation (4) is deduced from introducing Eqs (2) and (3) to the differential
th
equation for n order reaction
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SHENGLI et al.: MANGANESE CHLORIDE WITH L-α-HISTIDINE
797
1
dHi
n
=
k(1−α)
(4)
H∞ dt
furthermore,
n
1
dHi

H 
i
=
k1−


(5)
(6)

H∞ dt
H∞



ln

1 dH 

H 
i
i
 =lnk+nln1−




H∞ dt
H∞




So, the reaction rate constant k and the reaction order n are procured from
thermokinetics experimental data by linear least square fitting.


E 

lnk=lnA−
(7)

RT 
According to Arrhenius Eq. (7) and the value k with temperature changing, the
apparent activation energy E and the pre-exponential constant A are calculated out.
From the absolute rate theory, quantum theory and energy distribution theory,
the Eq. (8) is given,
≠
d[AB] c
≠
ε
h
≠
k T
≠
kT
≠
B
−
=
v=v[AB] = [AB] =
[AB] =
[AB]
(8)
dt
τ
h
N h
A
≠
where v is the vibration frequency. It is assumed that a molecular of c is dissociated af-
ter one vibration. ε is the vibration freedom energy, h Planck constant, k Boltzmann
B
constant and N Avogadro constant.
A
As we know, the relationship between the reaction rate and concentration is rep-
resented,
d[AB]
−
=k[A][B]
(9)
dt
When the reaction comes to the equilibrium, we have
≠
≠
[
AB] =K A[B]
(10)
(11)
The combination of the Eqs (8) – (10) gives
RT
≠
k=
K
N h
A
To the reaction system the basic thermodynamic Eqs (12) and (13) exist.
≠
∆
G = –RTlnK
≠
(12)
(13)
θ
θ
θ
∆
G =∆H −T∆S
≠ ≠ ≠
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98
SHENGLI et al.: MANGANESE CHLORIDE WITH L-α-HISTIDINE
Connecting the Eqs (11) and (12), Eq. (14) is derived.
θ
≠
 RT 
Nhk 
∆
G =RT ln
(14)
(15)



while Eq. (15) is from the combination of the Eqs (11) – (13).
RT −∆ Gθ / RT
RT (T∆Sθ −∆ Hθ ) / RT
RT ∆S / R −∆ Ηθ / RT
θ
≠
≠
≠
≠
≠
k=
e
=
e
=
e
e
N h
N h
N h
A
A
A
Finally, Eq. (16) is set up.
θ
≠
θ


k 
T 
 k
B

∆S
R
∆H
≠
ln
=ln  +
 h 
−
(16)


RT
θ
θ
∆
H and ∆S are thus available by linear least square regression.
≠ ≠
In conclusion, the reaction thermodynamic and kinetic parameters for the
non-reversible reactions are procured from the Eqs (6), (7), (14) and (16) at constant
pressure and isothermal conditions.
Materials
The MnCl ⋅6H O (A) is of A.R. grade. L-α-histidine (B) is of B.R. grade with the
2
2
>
and B are 0.1000 mol L . In our experiments, the molar ratio of two solutions, A to B
99.5% purity. They are dissolved in distilled water. The molarities of solution A
–
1
–
8
–1
is l:2. The conductivity of the deionized water is 5.48⋅10 S cm .
Experimental equipment and conditions
The reaction thermokinetics was executed by a microcalorimeter, type RD496-III
(
China, Southwest Institute of Electronic Engineering), which was equipped with
two 15 mL vessels (Fig. 1) [9]. After reaching equilibrium, the spacers of the sample
and reference vessels were pushed down simultaneously and the samples were
mixed. The microcalorimeter was calibrated by Joule effect and its sensitivity were
(
63.994±0.042), (64.308±0.027), (64.499±0.064), (64.638±0.078), (64.733±0.077)
–1
and (64.739±0.059) µV mW at the experimental temperatures of (298.15±0.005),
303.15±0.005), (308.15±0.005), (313.15±0.005), (318.15±0.005) and (323.15
0.005) K, respectively. The experimental precision and accuracy were checked by
measuring the enthalpy of special purity crystalline KCl in deionized water at
(
±
θ
m
–1
2
98.15 K. The experimental value of ∆ H of (17.238±0.048) kJ mol (t test, 99%
sol
–1
confidence) is the best agreement with that of (17.241±0.018) kJ mol reported
in [10]. This indicated that the device used in this work was reliable. The precision
measured was in 0.5%.
The IR spectra for the complex of manganese and histidine were determined by
the Bruker of USA, Model EQ Uinox-550 FT-IR spetrophotometer (KBr pellet). The
content of Mn was determined by ammonium peroxydisulfate oxidation method. The
2+
–
content of Cl was determined by Fajans method. Carbon, hydrogen, and nitrogen
J. Therm. Anal. Cal., 75, 2004

SHENGLI et al.: MANGANESE CHLORIDE WITH L-α-HISTIDINE
799
Fig. 1 Device used for the study of the formation reaction; 1 – calorimetric cell;
2
– adding tube containing manganese chloride solution; 3 – adding tube
containing histidine solution; 4 – silicone rubber cover; 5 – glass rod (on de-
pressing the bottom of tube 2 is broken. The two solutions are mixed in the 1
analyses were carried out on a 2400-type elemental analyzer of Perkin Elmer Com-
pany. TG-DTG data were obtained simultaneously by using a Perkin Elmer
thermogravimetric analyzer. The TG-DTG runs were carried out under a dynamic at-
–1
mosphere of dry oxygen at flow rate of 60 mL min . The heating rate used was
10°C min . Sample mass was about 1 mg.
–1
Results and discussion
θ
m
θ
m
Determination of ∆ H and calculation of ∆f,Cu(His) 2+
H
r
(aq)
2
The following Eq. (a) could represent the formation reaction of manganese histidine
complex:
2
+
2+
2
Mn (aq)+2His(aq)→Mn(His) (aq)
(a)
Within the range of the experimental temperature, the reaction is an endother-
mic one. ∆ H of the reaction was measured six times, at 298.15 K. It was 0.122,
θ
m
r
–
1
.121, 0.121, 0.121, 0.121 and 0.120 kJ mol , respectively, mean value was
0
–
1
(0.121±0.001) kJ mol . According to Hess’ law, the standard enthalpy of formation
of Mn(His) (aq) was calculated through Eq. (a):
2+
2
θ
m
θ
m
θ
m
θ
∆f,Mn(His) 22 +(aq) H =∆ H +(∆
2 +
H +2∆
H )
f,L-α-His(aq) m
r
f,Mn (aq)
–
1
=
=
[(0 .1 21±0.001)+(−220.75)+2×(−424.91±1.54)] kJ mol
–
1
(−1070.45±3.08) kJ mol
θ
m
θ
m
Here, ∆f,Mn 2+(aq)
H
is from [11] and ∆f,L-α-His(aq)
H
from [12].
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SHENGLI et al.: MANGANESE CHLORIDE WITH L-α-HISTIDINE
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SHENGLI et al.: MANGANESE CHLORIDE WITH L-α-HISTIDINE
801
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8
02
SHENGLI et al.: MANGANESE CHLORIDE WITH L-α-HISTIDINE
Fig. 2 Thermokinetic curve of the reaction for manganese chloride and L-α-histidine (298.15 K)
The thermokinetics calculation of the formation reaction
The typical thermokinetic (TK) curve of the reaction was shown in Fig. 2. The origi-
nal data obtained from the TK curve were presented in Table 1.
According to the Eqs of (6), (7), (14) and (16), the reaction rate constant (k), the
activation energy (E), the pre-exponential constant (A), the reaction order (n), the ac-
θ
≠
θ
≠
tivation enthalpy (∆H ), the activation entropy (∆S ), the activation free energy
θ
θ
(
∆G ) and the enthalpy (∆ H ) are attained, which were presented in Table 2.
The results in Table 2 indicate that the rate of the reaction increases with the
≠
r
≠
θ
temperature increasing, the reaction is of the first order, and the values of E and ∆H
≠
θ
are very low and ∆S is high. These observations show that the title reaction easily
proceeds over the temperature range of 298.15–323.15 K, as is the reaction of CrCl3
with histidine [13], which is consistent with the large hydroenthalpy and small for-
≠
2+
mation enthalpy of Mn(His) .
2
Preparation and composition of the complex
The final solution collected from each experiment was concentrated at a 343~353 K
water bath till crystal membrane formed on the surface, then it was put into a contain-
ing P O desiccator drying to constant mass.
2
5
The analytical results inflect that they have the identical composition of
Mn(His) Cl ⋅4H O. The analytical results of composition are summarized in Table 3.
2
2
2
Table 3 Analytical results of composition of solid complex (/%)
2
+
–
Mn
Cl
C
H
N
Calculated values
10.81
10.79
13.96
14.02
28.36
28.39
5.16
5.21
16.54
16.51
Experimental values
The IR absorption of main groups for complex and ligand are given in Table 4.
The IR spectrum for the complex shows that characteristic absorption peaks of
amino and carboxyl groups have a great shift as compared to those in the ligand. It in-
2
+
dicates that nitrogen and oxygen atoms in the complex coordinate to Mn in a
bidentate fashion. In addition to above, characteristic absorption peak of imidazolyl
group in the complex shifts intensively. This shows that nitrogen atom in the
J. Therm. Anal. Cal., 75, 2004

SHENGLI et al.: MANGANESE CHLORIDE WITH L-α-HISTIDINE
803
J. Therm. Anal. Cal., 75, 2004

8
04
SHENGLI et al.: MANGANESE CHLORIDE WITH L-α-HISTIDINE
2
+
–1
imidazolyl group coordinates to Mn as well. 3420 and 811 cm in the IR spectrum
for the complex are assigned to hydroxyl absorption of water. The existence of water
molecule in the complex is believed.
Thermostability of the solid complex
The TG-DTG curve of the solid complex of Mn(His) Cl ⋅4H O are presented in
2
2
2
Fig. 3. The data on the decomposition products, decomposition temperatures and res-
idue obtained from the Fig. 3 are listed in Table 5.
Table 5 Data on thermal decomposition of the complex
Product
Decomposition temperature/°C
Residue/%
a
Mn(His)
2
2
Cl
Cl
2
2
⋅1.5H
2
O
51–360
360–650
650–840
91.52 (91.54)
55.37 (55.29)
24.49 (22.76)
Mn(His)
⋅MnCl
2
MnCl
2
a
The data in brackets are calculated values
Table 5 and Fig. 3 allow the following confirmations:
(
1) The mass loss values in the processes of the thermal decomposition are close
to the calculated values.
2) The thermal decomposition processes proceeds in three steps. The first step is
the loss of the part of crystal water from the complex. The following step is that part of
the complex is discomposed into MnCl , the mixture of MnCl and Mn(His) Cl is ob-
tained. At the last step, the complex is discomposed into MnCl completely.
(
2
2
2
2
2
In order to attest the decomposition processes mentioned above, the intermedi-
ates and final products of the thermal decomposition of the complex was identified
Fig. 3 TG-DTG curve of the solid complex of Mn(His)
2
Cl
2
2
⋅4H O
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SHENGLI et al.: MANGANESE CHLORIDE WITH L-α-HISTIDINE
805
via IR spectrophotometry. IR spectra of these compound are in good agreement with
the characteristic peaks of Mn(His) Cl , Mn(His) Cl and MnCl , MnCl Therefore,
2
2
2
2
2
2.
it is reasonable to get the above results for the decomposition processes of the com-
plex.
Conclusions
•
•
Based on the basic thermodynamic equations, a set of thermokinetics models is de-
veloping for non-reversible reactions at constant temperature and pressure.
On the basis of experimental and calculated results, the reaction order of the for-
mation of Mn(His) Cl ⋅4H O over the studied temperature range is found to be of
2
2
2
the first one and the reaction is exothermic. The enthalpy change of the reaction
–
1
2+
2
is (0.121±0.001) kJ mol , the standard enthalpy of formation of Mn(His) (aq) is
–
1
(
The activation energy of the formation reaction of Mn(His)
–1070.45±3.08) kJ mol .
•
2
Cl
range of 298.15–323.15 K is very small, and the entropy of the formation reaction
2
⋅4H
O over the
2
of Mn(His) Cl ⋅4H O is high. The title reaction easily takes place at
2
2
2
2
98.15–323.15 K, which contributes to strong coordination force of histidine.
*
* *
We thank National Science Foundation of China and National Science Foundation of Shaanxi Prov-
ince for financial support.
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