Effect of the structure of the macroheterocyclic ligand on the catalytic properties of tetraarenoporphyrazine metal complexes: II. Oxidation of cysteine, catalyzed by cobalt tetraarenoporphyrazines

Article abstract of DOI:10.1023/B:RUGC.0000007664.25584.34

The catalytic activity of cobalt tetraarenoporphyrazine complexes in heterogeneous oxidation of cysteine is much dependent on the macrocycle structure and is inversely related to the electron-acceptor power of the ligand.

Full text of DOI:10.1023/B:RUGC.0000007664.25584.34

Russian Journal of General Chemistry, Vol. 73, No. 8, 2003, pp. 1315 1318. Translated from Zhurnal Obshchei Khimii, Vol. 73, No. 8, 2003,
pp. 1390 1393.
Original Russian Text Copyright
2003 by Korzhenevskii, Shikova, Koifman, Bykova.
Effect of the Structure of the Macroheterocyclic Ligand
on the Catalytic Properties
of Tetraarenoporphyrazine Metal Complexes:
II.1 Oxidation of Cysteine, Catalyzed
by Cobalt Tetraarenoporphyrazines
A. B. Korzhenevskii, T. G. Shikova, O. I. Koifman, and V. V. Bykova
Ivanovo State University of Chemistry and Technology, Ivanovo, Russia
Ivanovo State University, Ivanovo, Russia
Received July 10, 2001
Abstract The catalytic activity of cobalt tetraarenoporphyrazine complexes in heterogeneous oxidation of
cysteine is much dependent on the macrocycle structure and is inversely related to the electron-acceptor power
of the ligand.
At present both water-soluble [2, 3] and insoluble
Y
X
[4] transition metal phthalocyanine complexes have
been studied as catalysts in oxidation of sulfur-con-
taining compounds, such as hydrogen sulfide, ethane-
thiol, and cysteine.
X
Y
N
Co
N
N
N
N
N
N
N
Cystein oxidation with molecular oxygen is widely
used as a model for the industrially important oxida-
tion of thiols into disulfides. The reaction is activated
by various metal phthalocyanine complexes. The most
active is PcCo, its activity in heterogeneous condi-
tions being two orders of magnitude lower than in
homogeneous, iron phthalocyanine, too, is active both
in heterogeneous and homogeneous conditions [4],
whereas copper phthalocyanine exhibits low activity
in homogeneous conditions and is absolutely inactive
is heterogeneous [5].
X
Y
Y
X
Ia Ic
Y
X
X
Y
N
Co
N
N
N
N
N
N
N
To assess the effect of the nature of the macro-
cyclic ligand on the catalytic properties of cobalt tetra-
arenoporphyrazines in cysteine oxidation, we com-
pared the catalytic activity of cobalt complexes of
tetra-2,3-pyridinoporphyrazine (2,3-PycCo) (Ib), tetra-
pyrazinoporphyrazine (PzcCo) (Ic), 2,3-naphthalianine
(2,3-NcCo) (IIa), tetra-2,3-quinolinoporphyrazine
(2,3-QlcCo) (IIb), and tetra-2,3-quinoxalinoporphy-
razine (2,3-QxcCo) (IIc) with that of cobalt phthalo-
cyanine (PcCo) (Ia).
X
Y
Y
X
IIa IIc
X = Y = CH (a); X = CH, Y = N (b); X = Y = N (c).
complexes, based on the hypothesis of changing
transition metal valence [6].
There are several concepts of the mechanism of
catalytic oxidation of thiols in the presence of metal
The kinetics and mechanisms of heterogeneous
oxidation of thiols in the presence of metal phthalo-
cyanines have been studied in [7 9]. Borisenkova [7]
1
For communication I, see [1].
1070-3632/03/7308-1315$25.00 2003 MAIK Nauka/Interperiodica

1316
KORZHENEVSKII et al.
ln kapp
ln cc, M
9
2.5
3
1
2
6
6
5
2.7
8
4
5
4
2.9
3.1
7
3
2
6
3.3
3.5
1
5
0
1
2
3
4
5
6
7 , min
2
4
6 ln ccat
Fig. 1. Kinetic curves for cysteine oxidation at 298 K in
the presence of cobalt arenoporphyrazines (c, M):
(1) 2,3-NcCo (1.98), (2) PcCo (1.75), (3) 2,3-QlcCo (2.4),
(4) 2,3-PycCo (1.73), (5) 2,3-QxcCo (3.01), and
(6) PzcCo (5.46).
Fig. 2. Plot of ln k
vs. ln c for cysteine oxidation at
app
cat
298 K in the presence of (1) PzcCo, (2) 2,3-QxcCo,
(3) 2,3-PycCo, (4) 2,3-QlcCo, (5) PcCo, and
(6) 2,3-NcCo.
found that cystein is only oxidized in alkaline media
where its thiolic group is deprotonated; the reaction
begins with coordination of the substrate anion with
the metal ion; the reaction rate depends on the pH of
the solution and directly related to the partial pressure
of oxygen in the system, and the rate-limiting stage is
reaction between O2 and the adduct of the catalyst
with the thiol anion (Ct RS ).
ing the highest reaction rate (1% solution of cysteine
in 2% sodium hydroxide, pH 12.35).
It was found that in the presence of all the metal
complexes studied the process is first-order in sub-
strate (Fig. 1). From the kinetic curves we calculated
apparent reaction rate constants (kapp) and estimated
reaction order by the arbitrary molar catalyst con-
centration (ccat) (Fig. 2). The reaction order was equal
to one in all the cases.
According to general concepts of chemical kinetics
and published data, we can write the following equa-
tion for the cystein oxidation rate.
In view of the fact that the reaction orders in the
presence of PcCo and the other metal complexes are
the same both in substrate and catalyst, we proposed
a common reaction mechanism with all the cobalt
tetraarenoporphyrazines (Figs. 1 and 2).
dcc /d = kt cmt cncat cOp or dct/d = kapp ccm.
2
Here kapp = kt cncat cOp , cc is the cysteine concentra-
2
The kt value found from kapp, ccat, and cO (the
tion, ccat is the arbitrary molar catalyst concentration
2
[1], cOp is the oxygen concentration, kt and kapp are the
reaction order in oxygen was taken to be one), can be
used for comparing the catalytic activities of the
compounds and for calculating the activation energy
and entropy of the reaction studied.
2
true and apparent reaction rate constants, and m, n,
and p are the reaction orders in the corresponding
component.
The table lists the experimental and calculated
kinetic parameters. As seen, the reaction rate de-
creases in the order 2,3-NcCo > PcCo > 2,3-QlcCo >
2,3-PycCo > 2,3-QxcCo > PzsCo.
By the Winkler method we found that the initial
concentration of oxygen in the reaction medium is
1.05 10 M.
3
Taking into account that the gas phase over the re-
action mixture always consisted of oxygen and the
pressure in the system was maintained equal to
atmospheric thus ensuring effective transfer of oxygen
from the gas phase into water, we can consider the
oxygen concentration during experiment constant.
The activation parameters reveal a compensation
effect for all the cobalt tetraarenoporphyrazines
studied (Fig. 3). This result provides evidence for our
assumption of a common mechanism with all the
macroheterocycles. Consequently, the mechanism
proposed for the catalytic oxidation of cysteine on
PcCo is also valid for the reactions that occur on the
other complexes studied.
Based on earlier data for PcCo-catalyzed cysteine
oxidation, we chose experimental conditions provid-
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 73 No. 8 2003

EFFECT OF THE STRUCTURE OF THE MACROHETEROCYCLIC LIGAND... : II.
1317
Catalytic activity of cobal complexes of phthalocyanine and its structural analogs in cysteine oxidationa
ccat 102,
kapp 104,
kt,
ccat 102,
kapp 104,
kt,
T, K
1
1
1
1
M
s
l s 1 mol
M
s
l s 1 mol
PcCo
2,3-PycCo
2.94 0.12
8.11 0.31
13.40 1.03
4.07 0.11
10.33 0.50
20.94 2.28
6.96 0.14
12.80 0.93
22.91 2.58
35.5/ 111
298
303
313
1.29
1.75
3.04
0.59
1.12
1.80
0.66
1.14
2.31
6.83 0.18
9.24 0.48
16.13 1.02
3.81 0.15
7.23 0.23
11.65 0.63
6.24 0.22
10.77 0.53
21.76 2.08
29.7/ 121
50.51
50.53
50.53
61.60
61.59
61.60
89.72
89.74
89.74
1.73
4.76
7.86
1.89
4.79
9.70
2.06
3.78
6.77
16.23
16.23
16.23
20.55
20.55
20.55
32.23
32.24
32.24
1
1
1
E , kJ/mol/ S , J K 1 mol
PzcCo
2,3-NcCo
3.87 0.21
9.14 0.57
17.17 1.18
5.07 0.19
10.46 0.38
18.27 1.37
7.50 0.25
15.23 1.07
21.26 2.20
27.0/ 126
298
5.46
9.86
16.99
9.83
12.62
19.61
3.85
3.96 0.16
7.15 0.46
12.32 0.86
9.29 0.39
11.94 0.67
18.55 1.61
6.05 0.16
11.78 0.51
23.44 2.69
40.0/ 103
6.90
6.90
6.90
9.01
9.01
0.45
1.05
1.98
0.49
1.01
1.76
0.51
1.04
1.45
82.59
82.59
82.58
98.79
98.87
303
313
9.01
98.83
14.97
14.97
14.97
139.14
139.24
139.24
7.50
14.91
E , kJ/mol/ S , J K 1 mol
2,3-QlcCo
6.93 0.38
13.37 0.88
18.50 1.59
9.25 0.59
11.97 0.64
19.69 1.57
3.88 0.16
7.27 0.41
16.02 2.19
33.0/ 115
2,3-QxcCo
3.50 0.05
5.69 0.25
8.28 0.18
3.91 0.17
7.92 0.34
14.25 0.97
2.83 0.2
298
2.40
4.63
6.40
2.57
3.32
5.47
0.71
1.33
2.93
27.53
27.53
27.53
34.29
34.29
34.29
52.10
52.09
52.11
3.01
4.89
7.12
2.62
5.30
9.54
1.18
2.67
7.88
11.08
11.08
11.08
14.22
14.22
14.22
22.88
22.89
22.89
303
313
6.43 0.2
18.95 0.2
37.5/ 107
E , kJ/mol/ S , J K 1 mol
a
1
1
The errors in E (kJ/mol) and
S
(J K mol ) are 10%.
Our results show that, like in the catalytic decom-
position of hydrogen peroxide [1], the structure of the
macroheterocyclic ligand exerts a considerable effect
on the catalytic activity of metal complexes. Thus,
peripheral aza substitution reduces the catalytic
activity, whereas benzannelation both of phthalo-
cyanine and of its aza analogs enhances it.
complexes [10].
On the other hand, our data are supportive of the
mechanism proposed in [7] for oxidation of thiols
with molecular oxygen and involving reaction of
Cat RS with O2 as a limiting stage. The latter reac-
tion is favored by increased partial negative charge
on the metal atom [11].
At first glance, such a relationship between the
structure of the ligand and its catalytic activity may
seem unexpected, especially in view of the earlier
established fact that metal phthalocyanines are less
active catalysts than tetrapyrazinoporphyrazine
Actually, provided this mechanism is operative,
the least active should be the complex of a phthalo-
cyanine octaaza substituted in the periphery, tetra-
pyrazinoporphyrazine, containing eight strongly elec-
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 73 No. 8 2003

1318
KORZHENEVSKII et al.
Metal tetraarenoporphyrazines were prepared and
S , J K 1 mol
1
purified as described in [12 14] and identified by
spectral characteristics [12 14]. Catalysts were treated
with water to neutral and sulfate-free washings, dried
to constant weight at 423 K, and thoroughly ground
before use.
130
120
110
6
5
4
3
REFERENCES
2
1
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100
90
2. Simonov, A.D., Keier, N.P., Kundo, N.N., and Ma-
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p. 988.
1
25
30
35
40 E, kJ mol
Fig. 3. Compensation effect in cystein oxidation in the
presence of (1) PzsCo, (2) 2,3-QxcCo, (3) 2,3-PysCo,
(4) 2,3-QlcCo, (5) PcCo, and (6) 2,3-NcCo.
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tron-acceptor aza groups in the 3 and 4 positions of
benzene rings. The electronic effect of octaaza sub-
stitution can be assessed on the basis of the hypso-
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1
6. Maizlish, V.E. and Borodkin, I.F., Izv. Vyssh. Uchebn.
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p. 1003.
147 nm in sulfuric acid).
Linear benzannelation, by contrast, considerably
increases the electron density on the major choromo-
phore, i.e. can be considered as electron-donor substi-
tution in the periphery of phthalocyanine, which is
clearly seen from a considerable bathochromic shift
of the Q band in the electronic absortion spectrum in
7. Borisenkova, S.A., Neftekhimiya, 1991, no. 3, p. 391.
8. Borisenkova, S.A. and Denisova, E.P., Abstracts of
Papers, 3 Respublikanskaya konferentsiya po intensi-
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94 (3rd Republican Conf. on Intensification of
Petrochemical Processes Petrochemistry-94 ), Nizh-
nekamsk, 1994, p. 141.
going from PcCo to 2,3-NcCo (
acid).
75 nm in sulfuric
1
9. Anisimov, A.V., Akhmad Mokhammed, R., Borisen-
kova, S.A., Tarakanova, A.V., and Barkanova, S.V.,
Neftekhimiya, 1994, vol. 34, no. 4, p. 358.
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phthalocyanine and its aza analogs is enhanced by
benzannelation. Therewith, this effect is not strong
sufficiently to compensate for the adverse effect on
the catalytic activity of four aza atoms, as judged from
the fact that 2,3-QxcCo stands after 2,3-PycCo in the
activity order, while 2,3-QlcCo stands after PcCo.
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Khim. Geterotsikl. Soedin., 1984, no. 9, p. 1257.
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elektrokataliz metalloporfirinami (Catalysis and Elec-
trocatalysis with Metal Porphyrins), Moscow: Nauka,
1982.
EXPERIMENTAL
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The catalytic properties of metal complexes were
studied by the procedures in [7] using a temperature-
controlled rocker. Substrate concentration was fol-
lowed by the volume of absorbed oxygen.
Ivanovo, 1991.
13. Korzhenevskii, A.B., Cand. Sci. (Chem.) Dissertation,
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14. Bykova, V.V., Cand. Sci. (Chem.) Dissertation,
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Ivanovo, 1981.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 73 No. 8 2003