A novel catalyst iron(II) tetra(1,4-dithin)porphyrazine for oxygenating degradation of organic pollutants in aqueous solutions

Article abstract of DOI:10.1246/cl.2004.34

An efficient catalyst of the title complex (abbreviated as FePz(dtn) ₄) is a porphyrin-like complex, which is able to activate molecular oxygen for oxidative degradation of organic compounds in an extensive pH region without light excitation. The experiments indicated that the FePz(dtn) ₄/O₂ system showed an excellent oxygenation capability, in which the Rhodamine B(RhB) was degraded nearly 52% in alkaline aqueous solution in the seven hours and the p-nitrobenzoic acid(NBA) could be also oxygenated nearly 85% detected by UV-vis, HPLC in the similar conditions. The degradation components of RhB and NBA were analyzed by GC-MS and IR. The mineralization rate of RhB and NBA were 12 and 11.1% after reaction for 24 h respectively.

Full text of DOI:10.1246/cl.2004.34

3
4
Chemistry Letters Vol.33, No.1 (2004)
A Novel Catalyst Iron(II) Tetra(1,4-dithin)porphyrazine for Oxygenating
Degradation of Organic Pollutants in Aqueous Solutions
y;yy
yy
yy
ꢀy
y
Kejian Deng,
y
Fei Huang, Duoyuan Wang, Zhenghe Peng, and Yunhong Zhou
Department of Chemistry, Wuhan University, Wuhan 430072, P. R. China
yy
College of Chemistry and Life Science, South-Central University of Nationalities, Wuhan 430074, P. R. China
(Received August 11, 2003; CL-030742)
An efficient catalyst of the title complex (abbreviated as
6.86, citrate pH 3, or borate pH 9.2 were used respectively) with
ꢂ5
FePz(dtn)4) is a porphyrin-like complex, which is able to acti-
vate molecular oxygen for oxidative degradation of organic
compounds in an extensive pH region without light excitation.
The experiments indicated that the FePz(dtn)4/O2 system
showed an excellent oxygenation capability, in which the Rhod-
amine B(RhB) was degraded nearly 52% in alkaline aqueous so-
lution in the seven hours and the p-nitrobenzoic acid(NBA)
could be also oxygenated nearly 85% detected by UV–vis,
HPLC in the similar conditions. The degradation components
of RhB and NBA were analyzed by GC–MS and IR. The miner-
alization rate of RhB and NBA were 12 and 11.1% after reaction
for 24 h respectively.
5 mL RhB aqueous solution (1:0 ꢁ 10 mol/L) or 5 mL NBA
ꢂ3
aqueous solution (1:0 ꢁ 10 mol/L), respectively. The reaction
mixtures were bubbled first with nitrogen for adsorption equili-
bration in the first 30 min, and then, the oxygenation reaction
carried out in ambient temperature and under different pH con-
ditions with constant bubbling of oxygen. Reaction processes
were monitored by UV–vis spectroscopy (Perkin Elmer USA,
Lamberda-Bio35) and HPLC (Hitachi L7000, Turner (Kromasil)
C18 column, Japan) after filtering the catalyst on the ion-ex-
change resin in the different time intervals.
The reaction products with unreacted reactant were ana-
lyzed by GC–MS (HP8986, HP-5MS column) or GC (GC-
1
4
7AATF, OV225 column, Shimadzu, Japan) and by IR (Nexus
70 FTIR, USA) during different time intervals after filtering
Metallo-porphyrazines (MPz) and relative derivatives are a
kind of porphyrin-like complexes, which are of excellent stabil-
ities to light, heat and chemicals and with easier synthetic proce-
dure, so these molecules have potential applications in the cases
of photo-sensitization, photo-catalysis, and molecular recogniz-
the catalyst and removing the water from the degraded species
under the reduced pressure and treating the samples with ester-
ifying or silicifying reagent.
The oxidative degrading trend of RhB described by UV–vis
spectral changes (absorbance) with different oxygen-bubbling
time intervals in the presence of FePz(dtn)4 in borate buffer
(pH 9.2) is shown in Figure 1, during which the absorption peak
at 550 nm was decreasing gradually in the first 5 h, and an obvi-
ous dropping of this peak appeared at after 7 h, while the absorp-
tion peak around 200 nm rapidly increased corresponding with
the peak at 550 nm decreasing. It means that the aromatic ring
of the RhB has been broken during the oxygen bubbling and
the formed smaller molecules have a large absorbance around
the 200 nm. The peak further dropping around 200 nm during
the oxygen bubbling appears the degraded species in mineraliz-
ing.
1
ing for exterior substrates. Some experiments have shown that
the iron(III) tetra-sulfo-phthalocyanine (Fe(PcS))/H2O2 system
can efficiently degrade organic pollutants in a mixed aqueous so-
2
,3
lution with acetonitrile, and an efficient degradation of organic
pollutants employing (Fe(PcS))/H2O2 in aqueous solutions
without acetonitrile and with visible light irradiation has also
4,5
been observed. However, these systems are not yet able to ac-
tivate molecular oxygen for oxidative degradation of organic
pollutants in aqueous solutions. Recently, a new complex pho-
to-catalysis system with iron(II) bipyridine carried on ion-ex-
change resin as bio-mimetic oxygenase enzyme mode has been
6
successfully developed, which allows direct use of molecular
oxygen dissolved in water for pollutants treatment with visible
light at ambient temperature.
The degraded species of RhB in aqueous in the presence of
FePz(dnt)4/O2 are also analyzed by IR spectroscopic changes
1
1
0
0
0
0
0
.2
.0
.8
.6
.4
.2
.0
Here we report a novel catalyst, iron(II)–tetra(1,4-dithin)-
porphyrazine (FePz(dtn)4) carried on ion-exchange resin, which
is used as bio-mimetic oxygenase enzyme to activate molecular
oxygen for degrading the organic pollutants in the aqueous solu-
tions. To our knowledge, this is the first report for activating
molecule oxygen using the FePz(dtn)4 in water without light ex-
citation. The synthesis and characterizations of FePz(dtn)4 are
listed in the reference. The oxygenation degradation of two
non-biodegradable organic compounds, such as Rhodamine B
(RhB) and p-nitrobenzoic acid (NBA) as the target pollutants
have been studied in the presence of FePz(dtn)4 at ambient tem-
perature.
0
h
0
.5h
1h
COOH
3h
5h
Cl
NEt2
7h
Et N
2
o
7
24h
200
300
400
Wavelength/nm
500
600
1
0.0 mg of FePz(dtn)4 carried on the ion-exchange resin
Amberlite resin type CG400, size 200 mesh, FePz(dtn)4/resin
0.7%, w/w) was mixed in 5 mL of buffer (phosphate pH
Figure 1. UV–vis spectral changes of Rodamine B (1 ꢁ
ꢂ5
(
=
10 M) as a function of different oxygen-bubbling time interval
in the presence of FePz(dtn)4.
Copyright Ó 2004 The Chemical Society of Japan

Chemistry Letters Vol.33, No.1 (2004)
35
after oxygen bubbling for 24 h. There are some new absorption
peaks to be observed, for example, the new strong absorption
changes before and after 10 cycle runs. It means that the
FePz(dtn)4 carried on the resin is able to be used repeatedly
and stable, which is strongly adsorbed on the carrier without ob-
vious desorption during the oxygenating degradation reaction.
So the catalyst FePz(dtn)4 as bio-mimetic oxygenase enzyme
to activate molecular oxygen dissolved in water for degrading
organic pollutants is efficient at ambient temperature.
ꢂ1
at 2360 cm is attributed to –CꢃN of an aliphatic fragment.
ꢂ1
The new strong absorptions between 2800–3100 cm should
be attributed to the stretch vibration of –CH2– and –CH3 of ali-
phatic fragment cleaved from aromatic ring and the new strong
ꢂ1
absorptions at 1466 and 1389 cm are attributed to their bend
ꢂ1
vibration. The new absorption at 3379 cm is designated to
some fragment containing –OH or –NH groups. The new absorp-
tion peaks of C–H bonds of di-substituted benzene are designat-
The variations of relative concentration of RhB versus dif-
ferent oxygen-bubbling time interval at different pH conditions
in the presence of FePz(dtn)4 are shown in Figure 2, which indi-
cates that the oxidative degradations of RhB were significant ei-
ther in acidic and neutral aqueous, or in basic aqueous solutions.
The degradation rates calculated from the variations of relative
ꢂ1
ed to 833 and 586 cm , which appeared the benzopyran ring to
ꢂ1
have been fragmented. The absorption peak at 1713 cm is at-
ꢂ1
tributed to a C=O group other than in the RhB at 1759 cm , a
ꢂ5
strengthened absorption at this position means that there are
some conjugated carboxylic fragments generated during the
oxygenating degradation.
concentration of RhB with initial concentration (1 ꢁ 10 mol/
L) are about 20–22% in acidic and neutral aqueous and 52%
in basic aqueous solutions in the 7 h oxygen bubbling. It demon-
strated that the FePz(dtn)4 as a kind of novel catalyst, is able to
oxygenate degrading organic pollutants in an extensive pH con-
ditions.
The fragmental species of the RhB in the oxygenation deg-
radation were further confirmed by GC–MS analysis after react-
ing for 24 h and esterificating of the fragments in ethanol, in
which there are nine peaks to be observed in the GC analysis.
These fragments have been identified by MS analysis as degrad-
ed small molecules and some substituted benzenes, such as 1-
isocyano-4-methylbenzene (Retention time tR ¼ 5:57 min), 5-
pyrrolidin-2-ylidenmethyl-3,4-dihydropyrorol-2-one (tR ¼ 6:21
min), 2-furancarboxylic acid (tR ¼ 6:65 min), 2-methyl-3-oxo
cyclohex-1-enyloxyacetic acid ethanol ester (tR ¼ 9:15 min),
In order to further examine the role of FePz(dtn)4 in the oxy-
genation reaction, the degradation components of the NBA was
also investigated by HPLC in the similar conditions. According
to the peak intensity variations of the NBA during the oxygenat-
ing degradation, above 85% (in aqueous phase) of the NBA has
been degraded by oxygen bubbling for 24 h in the presence of
FePz(dtn)4. The IR data of the degraded species indicated that
the benzene ring of the NBA has been broken by the catalysis
oxygenation. Further, the GC data of the degraded products of
the NBA silicified by chlorotrimethylsilane was compared with
silicified standard samples to demonstrate that the NBA has been
degraded to form small molecule compounds such as fumaric
acid and maleic acid and mineralized products in the presence
of FePz(dtn)4/O2 system. The mineralization of the NBA is
11.1% after reacting for 24 h.
4
3
-methyl-2H-1-benzopyran-2-one (tR ¼ 12:25 min), 3-methyl-
-phenyl-2-propenal (tR ¼ 14:36 min), 5-hydroxytryptophan
(
1
tR ¼ 14:86 min), 2-cyanohexanoic acid ethyl ester (tR ¼
6:0 min) and 5-hydroxy-1H-indole-3-ethanol (tR ¼ 20:24 min).
These fragmental species are rearranged oxidative products from
RhB.
Combing the analyses of the GC–MS and IR data indicated
that the oxygenation degradation of RhB in the presence of
FePz(dtn)4/O2 without light irradiation produced a broken of
the pyran-ring and benzene ring to form small molecule species
in the oxidative processes. The mineralization rate of RhB deter-
This work introduced a novel FePz(dtn)4/O2 system, which
can activate molecular oxygen and degradate toxic organic pol-
lutants without light excitation in an extensive pH regions in
aqueous solution at ambient temperature.
8
,9
mined by chemical oxygen demand values (CODCr method ) is
about 12% after reacting for 24 h. The catalytic activity of the
FePz(dtn)4 in the degradation of RhB was maintained effectively
after 10 recyclic experiments (ca. 40 h) if 7 h is as a cycle run.
The IR spectra of the catalyst carried on the resin appeared no
The work was supported by the National Science Founda-
tion of China (No. 29771025) and (No. 20377053); The authors
also appreciate for the support of The State Key Projection
(
No. 29833090).
1
0
0
0
0
0
0
.0
.9
.8
.7
.6
.5
.4
References
1
C. F. van Nostrum and R. J. M. Nolte, J. Chem. Soc., Chem.
Commum., 21, 2385 (1996).
2
3
A. Sorokin, J.-L. Seris, and B. Meunier, Science, 268, 1163 (1995).
M. Sanchez, N. Chap, J.-B. Cazaux, and B. Meunier, Eur. J. Inorg.
Chem., 2001, 1775.
Fitting line of blank
Basic
Acid
4
5
6
7
X. Tao, W. Ma, T. Zhang, and J. Zhao, Angew. Chem., Int. Ed., 40,
3
014 (2001).
X. Tao, W. Ma, T. Zhang, and J. Zhao, Chem.—Eur. J., 8, 1321
(2002).
Neutral
0
1
2
3
4
5
6
7
8
W. Ma, J. Li, X. Tao, J. He, Y. Xu, J. C. Yu, and J. Zhao, Angew.
Chem., Int. Ed., 42, 1029 (2003).
Z.-B. Qin, Z.-H. Peng, et al., Wuhan Univ. Nat. Sci. (in Chinese), 2,
Time/hour
Figure 2. The variation of relative concentration of Rodamine
ꢂ5
B (1 ꢁ 10 M) versus different oxygen-bubbling time interval
6
5 (1985).
Chinese National Standard. GB 11914-89 (1989).
T. Wu, G. Liu, J. Zhao, H. Hidaka, and N. Serpone, J. Phys. Chem.
B, 102, 5845 (1998); T. Wu, G. Liu, J. Zhao, H.
Hidaka, and N. Serpone, J. Phys. Chem. B, 103, 4862 (1999).
and different pH (citrate pH 3.0, phosphate pH 6.86, borate pH
8
9
9.18) in the presence of FePz(dtn)4, The fitting line in the top
is a blank experiment in the absence of FePz(dtn)4 in borate
buffer.
Published on the web (Advance View) December 15, 2003; DOI 10.1246/cl.2004.34