Synthesis of novel acyclic and multiple phenyl iron tetraamino ligand catalysts and its catalytic activity for degradation of dye wastewater by H2O2

Article abstract of DOI:10.1002/aoc.6252

We need a practical, inexpensive, and green way to reduce the environmental pollutants, especially for dye wastewater. The discharge of industrial wastewater such as organic dyes will cause serious pollution to water bodies, thereby affecting people's liv

Full text of DOI:10.1002/aoc.6252

Received: 10 February 2021
DOI: 10.1002/aoc.6252
Revised: 18 March 2021
Accepted: 21 March 2021
F U L L P A P E R
Synthesis of novel acyclic and multiple phenyl iron
tetraamino ligand catalysts and its catalytic activity for
degradation of dye wastewater by H2O2
Shun-Lai Li
| Run Zhou
| Wei-Jing Zhao
| Hong-Guang Du
College of Chemistry, Beijing University
of Chemical Technology, Beijing, China
We need a practical, inexpensive, and green way to reduce the environmental
pollutants, especially for dye wastewater. The discharge of industrial wastewater
such as organic dyes will cause serious pollution to water bodies, thereby affect-
ing people's lives. In this work, we designed and successfully synthesized four
new ligand catalysts. The total outputs of diamide diamino iron ligand
compounds A and B are 71.33% and 61.39%, respectively. The total outputs of
polyaromatic iron tetraamido macrocyclic ligand (TAML) compounds C and D
are 38.49% and 49.11%, respectively. The catalytic effects of four catalysts on the
degradation of dye wastewater by hydrogen peroxide oxidation were studied
and compared with the second-generation FeIII-TAML catalyst. The experimen-
tal results showed that acyclic catalyst A and B has good catalytic effect. For
methylene blue, methyl orange, rhodamine B three dyes wastewater, under the
conditions of 20ꢀC, Ccatalyst A = 0.056–0.28 mM and Chydrogen peroxide = 33 mM,
the decolorization rate and chemical oxygen demand (COD) removal rate are
81.53%–97.58% and 52.2%–60.7%, respectively. Under the condition of 20ꢀC,
Correspondence
Hong-Guang Du PhD, College of Science,
Beijing University of Chemical
Technology, Beijing 100029, China.
Email: dhg@mail.buct.edu.cn
Funding information
National Natural Science Foundation of
China, Grant/Award Number: 21272022
C
catalyst B = 0.75 mM and Chydrogen peroxide = 33 mM, the decolorization rate and
COD removal rate are 48.33%–80.33% and 44.6%–57.8%, respectively.
K E Y W O R D S
COD, diamide diamino iron ligand, iron tetraamido macrocyclic ligand, wastewater
treatment
1 | INTRODUCTION
There are three kinds of wastewater treatment
methods: physical method, chemical method, and biolog-
In our daily life, chemistry is inseparable everywhere.
However, the pollution caused by chemistry also affects
our daily life. The severe situation of water pollution has
received increasing attention from all over the world, and
the pollution of water has become one of the most con-
cerned environmental problems that need to be urgently
addressed in the 20th century. Organic pollutants
produced and used by industries and pharmaceutical
companies are one of the main factors causing water
pollution and health problems.[1]
ical method. At present, the treatment methods of toxic
and harmful chemical pollutants such as azo dyed and
nitroaromatics mainly include reduction, degradation,
and adsorption.[2–5] The difference between them is that
one is a chemical process to convert chemical pollutants
into other substances by catalysts; the other is a physical
process in which composites combined with pollutants
and adsorbed to its body. This article mainly studies the
degradation of pollutants through chemical catalysis.
Chemical methods mainly include chemical oxidation
Appl Organomet Chem. 2021;e6252.
wileyonlinelibrary.com/journal/aoc
© 2021 John Wiley & Sons, Ltd.
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https://doi.org/10.1002/aoc.6252

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LI ET AL.
and advanced oxidation. Chemical oxidation is a treat-
ment method that uses strong oxidants (such as KMnO4,
ClO2, H2O2, and O3) and peroxymonosulfate or
peroxydisulfate to generate free radicals for degradation
of organic pollutants in water.[6,7] Advanced oxidation
process (AOP) is a new water treatment method, which
oxidizes the hard-to-degrade macromolecular toxic
organic matter into low-toxic or nontoxic small mole-
cules.[8–12] The photocatalytic effect of semiconductor
materials on organic substances can degrade organic sub-
stances into CO2, H2O, and other inorganic substances.
Fenton oxidation was first discovered by British scientist
Fenton, and the optimal pH value for Fenton oxidation
was 3. It mixed hydrogen peroxide with iron salts to form
a strong oxidation system, which can degrade organic
substances in wastewater, but a large amount of iron
hydroxide sludge is produced after the reaction. At the
same time, the dependence of Fenton reaction on ferrous
ion also limits the wide application of Fenton oxidation
method to a certain extent.[13]
At the end of the 20th century, researchers at
Carnegie Mellon University developed a type of long-life
catalyst through iterative design, which is iron-tetraamido
macrocyclic ligand (FeIII-TAML).[14] The target com-
pound is based on the advantages of biological enzyme
imitation, high efficiency, and low pollution. The
research team spent about 15 years synthesizing the
first structure of the FeIII-TAML activator. So far, many
FeIII-TAML catalysts with different structures have
appeared.[15–22]
The structure of the iron tetra amide-based macrocy-
clic ligand catalyst is very similar to the structure of the
porphyrin in heme. Compared with advanced oxidation
technology in wastewater system treatment, it has high
reactivity and selectivity for the oxidation of aromatic
organic pollutants.[23–25] FeIII-TAML catalyst can catalyst
the decomposition of peroxide to generate free radicals,
and then the free radicals react with organic compounds
to degrade organics.[26] This catalytic treatment method
can effectively replace the current wastewater treatment
method. According to the toxicity test, the toxicity of the
polluted water is sharply reduced after the organic waste-
water is treated with FeIII-TAML/H2O2, and the catalyst
itself can be degraded, and a small amount of residual
FeIII-TAML has no adverse effect on fish or microorgan-
ism.[27] In addition, the amount of FeIII-TAML used is
low; the concentration of FeIII-TAML catalyst is in the
range of nM to μM. Compared with the inorganic ferrous
salt used in the Fenton process, FeIII-TAML catalyst has
the advantages of wide pH range, low dosage, no second-
ary pollution, and environmental friendliness.[28] There-
fore, it has been widely studied and applied in various
fields. At present, FeIII-TAML has been used to degrade a
variety of pollutants in wastewater, including dyes,
estrogen compounds, nitrophenol, bromophenol,
thiophosphate insecticides, and pharmaceuticals.[29–35]
However, due to the long synthesis route and high
cost of FeIII-TAML catalyst, it cannot be applied in indus-
try. In order to solve these problems, the structure of the
second-generation FeIII-TAML catalyst was simplified in
this study. We designed and synthesized two new com-
pounds A and B (Figure 1). The synthesis steps are short-
ened, so the synthesis cost of the catalyst was reduced,
and the total yield is greatly improved.
At the same time, according to the structure of the
first- and second-generation FeIII-TAML catalysts,
the structure of the catalyst was redesigned in this paper,
and polyphenyl FeIII-TAML compounds C and D were
synthesized (Figure 1). In this paper, four new catalysts
of A, B, C, and D have been successfully synthesized, and
the optimal catalytic conditions of catalysts A, B, C, and
D were explored by treatment methylene blue, methyl
orange, and rhodamine B wastewater, and the catalytic
effects of the four catalysts were compared with those of
the second-generation FeIII-TAML catalyst.[36]
2 | EXPERIMENT
2.1 | Materials
All reagents were analytical pure, and solvents were
dried by standard procedures before used. The infrared
(IR) spectra were recorded by Bruker Vector22 spectro-
1
photometer. The H (400 MHz) and 13C{1H} (100 MHz)
nuclear magnetic resonance (NMR) spectra were
recorded on a Bruker AVANCE AV 400-MHz spectrome-
ter in D2O, CDCl3, or DMSO-d6. The High Resolution
Mass Spectrometer (HRMS) were recorded with Agilent
Q-TOF-6540 high-resolution mass spectrometer. The dye
absorbance was measured using a 722 spectrophotometer.
The elemental analyses (C, H, N, and O) were performed
on an Elementar Vario EL CUBE.
2.2 | Synthesis of iron diamide diamino
ligand a
The synthesis of iron diamide diamino ligand A is shown
in Figure 2.
In a 100-ml round-bottom flask, o-phenylenediamine
(5.0 g, 46.23 mmol) was dissolved in tetrahydrofuran
(THF) (50 ml). Stir until the solid is completely dissolved,
and triethylamine (7.69 ml, 55.48 mmol) was added. Di-
tert-butyl dicarbonate (10.63 ml, 46.23 mmol) and 20-ml
THF were added slowly under ice bath. Slowly add the

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FIGURE 1 Structures of acyclic iron diamide diamino ligands compounds A and B and multiple phenyl iron tetraamido macrocyclic
ligand compounds C and D
FIGURE 2 Synthetic route of iron diamide diamino
ligand A
liquid dropwise to the system, then the system returns to
room temperature, and the progress of the reaction is
checked by Thin Layer Chromatography (TLC). At the
end of the reaction, the filtrate was evaporated: add
10-ml ethanol, heat to dissolve completely, add 5-ml
n-hexane, crystallize in ice bath, filter, and dry to obtain
white solid product A1. Yield: 89% (8.55 g). 1H NMR
(400 MHz, CDCl3, δ, ppm): 7.28 (d, J = 9.6, 1H, ArH),
7.00 (td, J1 = 7.6, J2 = 1.2, 1H, ArH), 6.78 (td, J1 = 7.6,
J2 = 1.2, 1H, ArH), 6.79 (d, J = 6.0, 1H, ArH), 6.20 (s, 1H,
–NH–), 3.48 (s, 2H, ArNH2), and 1.51 (s, 9H, –CH3). 13C
NMR (100 MHz, CDCl3, δ, ppm): 153.8, 139.9, 126.2,
124.8, 119.7, 117.7, 80.6, and 28.4.
Add A1 (2.0 g, 18.5 mmol) into a 100-ml round-
bottom flask, add 40-ml freshly distilled THF, and stir
until the solid is completely dissolved. Triethylamine
(3.08 ml, 22.19 mmol) was added. A mixture of 0.78-ml
(9.25 mmol) oxalyl chloride and 20-ml freshly distilled
THF was slowly added under ice bath. At the end of drip,
return to room temperature and react for 8 h. Filter and
remove the solvent under reduced pressure to obtain a
crude product, add 5-ml ethanol to wash, filter, and dry
to obtain a white solid product A2. Yield: 88% (1.98 g). 1H
NMR (400 MHz, CDCl3, δ, ppm): 9.76 (s, 2H, –NHC=O),
7.77 (t, J1 = 5.2, J2 = 4.4, 2H, ArH), 7.46 (t, J1 = 4.8,
J2 = 4.4, 2H, ArH), 7.23 (m, 4H, ArH), 6.66 (s, 2H,
–NH–), and 1.53 (s, 18H, –CH3). 13C NMR (100 MHz,
CDCl3, δ, ppm): 158.1, 153.8, 130.1, 129.2, 126.8, 125.9,
125.1, 124.0, 81.5, and 28.3.
Add 1.0 g of A2 into a 100-ml round-bottom flask and
dissolve with 30 ml of ethyl acetate. The system was
stirred in an ice bath and slowly added 5 ml of concen-
trated hydrochloric acid. After the ice bath was removed,
the system returned to room temperature and the reac-
tion was continued for 2 h. The reaction was completed
by TLC. The acid was neutralized with ice cold aqueous
NaOH, and the pH of the aqueous layer was adjusted to
9–10, and the organic and aqueous layers were separated.
The aqueous layer was extracted three times with ethyl
acetate (EA). Organic layers were combined and dried
over Na2SO4, and by the rotary evaporation, solvent was
1
removed to afford white solid A3. Yield: 99% (0.58 g). H
NMR (400 MHz, DMSO-d6, δ, ppm): 9.99 (s, 2H,
–NHC=O), 7.27 (d, J = 7.2, 2H, ArH), 6.98 (td, J1 = 8,
J2 = 0.8, 2H, ArH), 6.78 (d, J = 7.2, 2H, ArH), 6.61 (t,
J = 7.6, 2H, ArH), an 4.99 (s, 4H, ArNH2). 13C NMR
(100 MHz, DMSO-d6, δ, ppm): 158.7, 142.6, 126.8, 125.5,
122.2, 116.4, and 116.3. Fourier transform IR (FT-IR)
(KBr): 3436 (ArNH2), 3366 (ArNHC=O), 3245 (ArNH2),
3035 (ArNH), 1664 (RCONHR'), 1617 (Ph), 1527 (Ph),
1485 (Ph), 1450, 1315, 1291, 1158, 887, 745, and
649 cmꢁ1
.
ESI-FTMS [M + H]+ m/z: calcd for
+
C14H15N4O2 271.1190 (100.0%), 272.1223 (15.1%), found
217.1186 and 272.1227.

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Add 0.45 g (1.66 mmol) A3 to a 100-ml round-bottom
small amount of methanol, filtered, and dried to obtain
golden yellow solid product Bl. Yield: 78.5% (10.58 g). H
1
flask and dissolve with 60 ml of freshly distilled THF.
Heat in a water bath at 40ꢀC and slowly add 400 mg of
sodium hydride (16.64 mmol) with stirring. After reaction
for 3 h, the system became turbid. FeCl3 (270 mg,
1.66 mmol) was dissolved in 10-ml freshly distilled THF
and slowly dropped into the system. The system turns
brown gray and reacts for 2 h. The liquid was dried, and
the gray green solid was washed with ethanol, filtered,
NMR (400 MHz, CDCl3, δ, ppm): 11.15 (s, 2H, CONH),
8.79 (dd, J1 = 1.2, J2 = 8.4, 2H, ArH), 8.23 (dd, J1 = 1.6,
J2 = 8.4, 2H, ArH), 7.67 (td, J1 = 1.2, J2 = 7.2, 2H, ArH),
7.22 (td, J1 = 7.6, J2 = 1.2, 2H, ArH), and 1.79 (s, 6H,
CH3). 13C NMR (100 MHz, CDCl3, δ, ppm): 171.7, 137.0,
136.0, 134.3, 125.8, 123.9, 122.6, 53.2, and 23.7.
B1 (5.0 g, 13.43 mmol) was added to a 250-ml round-
bottom flask and dissolved in 60-ml ethyl acetate. Stan-
nous chloride (24.24 g, 107.4 mmol) was dissolved in
8.0-ml concentrated hydrochloric acid, dropped into the
flask under ice bath, and stirred for 2 h at room tempera-
ture. It was observed that the yellow solution gradually
became clear, and the TLC monitoring reaction did not
change. Adjust pH to 9–10 with NaOH cold solution
under ice bath. The aqueous layer was extracted three
times with EA; all organic layers were combined and
dried over Na2SO4 and rotary evaporated till no solvent
under reduced pressure; and the yellow solid crude prod-
uct was obtained. The solid was recrystallized with etha-
nol and n-hexane to obtain light pink solid B2. Yield: 85%
1
and dried to obtain gray solid A. Yield: 92% (0.55 g). H
NMR (400 MHz, D2O, δ, ppm): 7.74 (s, 2H, ArH), 7.55 (s,
2H, ArH), 7.27 (s, 4H, ArH), and 2.84 (s, 4H, NH2). FT-IR
(KBr): 3322 (ArNH2), 3060 (Ar–H), 1573 (RCONHR'),
1467 (Ph), 1404 (Ph), 1339, 1148, 1042, 918, 874, and
750 cmꢁ1
.
ESI-HRMS [M + H]ꢁ m/z: calcd for
+
C14H13FeN4O2 325.0388, found 325.0963. Elemental
analysis: C, 51.88; H, 3.73; N, 17.29; O, 9.87; found (%): C,
49.19; H, 2.91; N, 13.50; O, 10.03.
2.3 | Synthesis of iron diamide diamino
ligand B
1
(3.55 g). H NMR (400 MHz, DMSO-d6, δ, ppm): 8.99 (s,
The synthesis of iron diamide diamino ligand B is shown
in Figure 3.
2H, CONH), 6.95 (td, J1 = 8.8, J2 = 0.8, 4H, ArH), 6.71
(dd, J1 = 7.6, J2 = 1.2, 2H, ArH), 6.53 (td, J1 = 7.6,
J2 = 1.2, 2H, ArH), 4.87 (s, 4H, NH2), and 1.56 (s, 6H,
–CH3). 13C NMR (100 MHz, DMSO-d6, δ, ppm): 172.8,
144.1, 127.5, 126.9, 122.7, 115.8, 115.4, 50.7, and 23.5. FT-
IR (KBr): 3419 (ArNH2), 3375 (ArNH2), 3307 (ArNHR),
3261 (ArNH2), 3033 (Ar-H), 2973 (RCH3), 1682, 1642
(RCONHR'), 1595 (Ph), 1505 (Ph), 1455, 1302, 1221, 1158,
922, and 746 cmꢁ1. ESI-FTMS [M + H]+ m/z: calcd for
C17H21N4O2+: 313.1659 (100.0%), 314.1693 (18.4%), found
313.1654 and 314.1689.
The 0.30 g (0.96 mmol) of B2 was added to a 100-ml
round-bottom flask and dissolved in 50 ml of freshly dis-
tilled THF. The system was heated in a water bath at
30ꢀC, and 230 mg of sodium hydride (9.6 mmol) was
slowly added with stirring. After 3 h of reaction, the sys-
tem became turbid and heated to 40ꢀC. FeCl3 (155.8 mg,
In
a 250-ml round-bottom flask, 2-nitroaniline
(10.0 g, 72.4 mmol) was dissolved in freshly distilled THF
(150 ml). After stirring and dissolving completely, pyri-
dine (8.16 ml, 101.4 mmol) was added. The system is
cooled by ice bath. Add 2,2-dimethylmalonyl chloride
(4.78 ml, 36.2 mmol) to 30-ml freshly distilled THF, and
add it into the reaction bottle drop by drop through the
dropping funnel at the rate of 1 drop per second. At
the end of drip, the ice bath was removed, and the reac-
tion was returned to room temperature and stir over-
night. The solid salt is removed by filtration. The liquid
was evaporated to obtain an orange oil, and 20 ml of
methyl tert-butyl ether was added and sonicate for
10 min to precipitate a large amount of yellow solid. The
crude product obtained by filtration was washed with a
FIGURE 3 Synthetic route of iron diamide diamino
ligand B

LI ET AL.
5 of 11
0.96 mmol) was dissolved in 10-ml freshly distilled THF
and slowly dropped into the system, the system turned
brown, and reacted for 2 h. The solvent was removed
under reduced pressure, and the brown solid was washed
with ethanol, filtered, and dried to obtain of a red-brown
(100 MHz, CDCl3, δ, ppm): 164.6, 136.6, 136.3, 135.2,
135.0, 131.0, 129.9, 126.8, 126.0, 123.8, and 122.3.
C1 (1.86 g, 4.58 mmol) was added to 250-ml round-
bottom flask, add 90-ml anhydrous ethanol and 30-ml
water to dissolve. The system is yellow and turbid.
Reduced iron powder (2.04 g, 36.62 mmol) and NH4Cl
(0.98 g, 18.31 mmol) were added. After refluxing for 2 h,
the system was gray black. Filter while it is hot, the liquid
by rotatory evaporation under reduced pressure to get
solid, wash with a small amount of anhydrous ethanol
and deionized water, filter, and dry to get gray solid C2.
Yield: 92.5% (1.47 g). 1H NMR(400 MHz, DMSO-d6, δ,
ppm): 9.79 (s, 2H, –NHCO), 8.59 (s, 1H, ArH), 8.16 (t,
J = 1.2, 2H, ArH), 7.65 (t, J = 7.6, 1H, ArH), 7.19 (d,
J = 7.2, 2H), 6.99 (dt, J1 = 1.2, J2 = 8, 2H, ArH), 6.79 (dd,
J = 1.2, 2H, ArH), 6.61 (dt, J1 = 1.2, J2 = 7.6, 2H, ArH),
and 4.95 (s, 4H, ArNH2). 13C NMR (100 MHz, DMSO-d6,
δ, ppm): 165.0, 130.6, 128.5, 127.2, 126.7, 126.7, 123.0,
116.3, and 116.1.
1
solid B. Yield: 92% (0.28 g). H NMR (400 MHz, DMSO-
d6, δ, ppm): 10.58 (s, 4H, NH2), 6.92 (s, 8H, ArH), and
1.06 (s, 6H, –CH3). FT-IR (KBr): 3402 (ArNH2), 2951
(RCH3), 1698 (RCONHR'), 1598 (Ph), 1450 (Ph), 1361,
1063, 880, and 757 cmꢁ1. ESI-HRMS[M-Cl]ꢁ m/z: calcd
+
for C17H18FeN4O2 366.0780, found 366.0691. Elemental
analysis: C, 55.76; H, 4.95; N, 15.3; O, 8.74; found (%): C,
52.28; H, 5.02; N, 14.50; O, 8.82.
2.4 | Synthesis of iron TAML C
The synthesis of iron TAML C is shown in Figure 4.
In a 250-ml round-bottom flask, 2-nitroaniline (4.0 g,
28.96 mmol) was dissolved in freshly distilled THF
(140 ml), and pyridine (4.18 ml, 40.54 mmol) was added.
The system is in an ice bath. Dissolve m-dibenzoyl chlo-
ride (2.94 g, 14.48 mmol) in 40-ml freshly distilled THF,
and add it into the reaction bottle drop by drop at the rate
of 1 drop per second. After adding, remove the ice bath to
recover to room temperature and stir overnight. The solid
obtained by filtration is washed with water and then
washed with ethanol to obtain light yellow solid product
C1. The liquid was dried under reduced pressure and
turned into orange yellow oil. After adding 10-ml etha-
nol, solid precipitated out and filtered, golden yellow
C2 (0.20 g, 0.577 mmol) was added to a 250-ml round-
bottom flask and dissolved in freshly distilled THF
(150 ml). Pyridine (0.19 ml, 2.31 mmol) was added under
stirring. The system is cooled by ice bath. Add
2,2-dimethylmalonyl chloride (0.076 ml, 0.577 mmol) to
30-ml freshly distilled THF, and add it into the reaction
bottle drop by drop through the dropping funnel at the
rate of 1 drop per second. At the end of drip, the ice bath
was removed, and the reaction was returned to room
temperature and stir overnight. The solid salt is removed
by filtration, the solvent was removed from the liquid, a
small amount of ethanol was added, and the system was
sonicated for 10 min. A large amount of solids appeared
in the system, filtered, and dried, liquid adding a small
amount of n-hexane recrystallization, and a total of white
1
solid product C1 was obtained. Yield: 95% (5.61 g). H
NMR (400 MHz, CDCl3, δ, ppm): 11.47 (s, 2H, –NHCO),
9.01 (dd, J1 = 8.4, J2 = 0.8, 2H, ArH), 8.67 (s, 1H, ArH),
8.31 (dd, J1 = 8.4, J2 = 1.6, 2H, ArH), 8.21 (dd, J1 = 7.6,
J2 = 1.6, 2H, ArH), 7.75 (dt, J1 = 10.0, J2 = 2.0, 3H,
ArH), and 7.27 (dt, J1 = 8.4, J2 = 0.8, 2H, ArH). 13C NMR
1
solid product C3 was obtained. Yield: 60% (0.15 g). H
NMR (400 MHz, DMSO-d6, δ, ppm): 10.02 (s, 2H, CON-
HAr), 9.83 (s, 2H, CONHAr), 8.29 (d, J = 8.4, 2H, ArNH),
FIGURE 4 Synthetic route of iron tetraamido macrocyclic ligand C

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8.25 (s, 1H, ArH), 8.20 (d, J = 7.6, 2H, ArH), 7.78 (t,
J1 = 8.0, J2 = 7.6, 1H, ArH), 7.37 (t, J1 = 8.4, J2 = 8.0,
2H, ArH), 7.33 (d, J = 1.2, 2H, ArH), and 7.37 (td,
J1 = 7.6, J2 = 1.2, 2H, ArH). 13C NMR (100 MHz, DMSO-
d6, δ, ppm): 174.2, 163.2, 134.2, 132.1, 131.8, 130.0, 128.3,
126.7, 126.5, 124.4, 123.5, 122.7, 52.2, and 23.6. FT-IR
(KBr): 3279 (ArNHR), 3068 (Ph-H), 2968 (–CH3), 1645
(RCONHR'), 1600 (RCONHR'), 1524 (Ph), 1447 (Ph),
1304, 1362, 1141, 918, 756, 711 cmꢁ1. ESI-FTMS [M
The synthetic route of ligand D is basically the same
as that of ligand C, and the first two steps are the same.
In the third step, C2 (0.235 g, 0.678 mmol) was added into
a 250-ml round-bottom flask and dissolved in freshly dis-
tilled THF (150 ml). Pyridine (0.22-ml, 2.71 mmol) was
added under stirring. m-dibenzoyl chloride (0.138 g,
0.678 mmol) was dissolved in 50 ml of freshly distilled
THF and added to the solution by a drop funnel at room
temperature. During the reaction, white solid is produced
and the system becomes turbid. The white solid was
filtered and washed with water dried to obtain 0.18-g
product D3. The liquid was dried under reduced pressure
and washed with ethanol and dried obtain 0.082-g
product D3. The total D3 was 0.262 g. Yield: 81%.
1H NMR (400 MHz, DMSO-d6, δ, ppm): 10.28 (s, 4H,
CONHAr), 8.71 (s, 2H, ArNH), 8.19 (dd, J1 = 8.0,
J2 = 1.2, 4H, ArH), 7.88 (q, J = 3.6, 4H, ArH), 7.72
(t, J = 8.0, 2H, ArH), and 7.33 (q, J = 3.6, 4H, ArH). 13C
NMR (100 MHz, DMSO-d6, δ, ppm): 164.9, 134.7, 130.9,
130.7, 129.1, 126.2, 125.8, and 125.1. FT-IR (KBr): 3305
(ArNHR), 3067 (Ph-H), 1680 (RCONHR'), 1639
(RCONHR'), 1603 (Ph), 1531 (Ph), 1490, 1446, 1315, and
+ H]+ m/z: calcd for C25H23N4O4 443.1714 (100.0%)
+
and 444.1747 (27.0%); found 443.1711 and 444.1746.
C3 (0.11 g, 0.237 mmol) was dissolved in freshly
distilled THF (50 ml) under the protection of nitrogen. n-
BuLi (25.43%, 0.44 ml, 1.19 mmol) was slowly added to
the system under the cooling of liquid nitrogen ethyl ace-
tate. Gradual dissolution of the ligand was observed.
After stirring for 30 min, FeCl3 (38.5 mg, 0.237 mmol)
was dissolved in freshly distilled THF (5 ml), and the
color of the system changed to light yellow. After half an
hour, remove the cooling device and return to room tem-
perature. The system turned gray and turbid, stirred for
4 h under the protection of nitrogen at room tempera-
ture, heated for 2 h at 70ꢀC, filtered, and washed
with ethanol to obtain solid C. Yield: 73% (0.087 g).
FT-IR (KBr): 3278, 3068 (Ph-H), 2964 (RCH3), 1646, 1600,
1518 (Ph), 1442 (Ph), 1306, 1142, 1088, 868, 759,
753 cmꢁ1
.
ESI-FTMS [M + H]+ m/z: calcd for
+
C28H21N4O4 477.1557 (100.0%) and 478.1591 (30.3%);
found 477.1557 and 478.1600.
D3 (0.124 g, 0.259 mmol) was dissolved in freshly dis-
tilled THF (50 ml) under the protection of nitrogen, the
solubility of ligand was poor and the solution was white
and turbid. n-BuLi (0.48 ml, 1.29 mmol) was slowly
added to the system under the cooling of liquid nitrogen
ethyl acetate. Gradual dissolution of the ligand was
observed. After stirring for 30 min, FeCl3 (42 mg,
0.259 mmol) was dissolved in freshly distilled THF
(5 ml), and the color of the system changed to light yel-
low. After reacting in ice bath for half an hour, the
and 711 cmꢁ1
.
ESI-HRMS [M-H]ꢁ m/z: calcd for
C25H17FeN4O4ꢁ493.0605; found 493.0648. Elemental
analysis: C, 59.91; H, 3.62; N, 11.18; Found (%): C,
59.25; H, 3.78; N, 10.89.
2.5 | Synthesis of iron TAML D
The synthesis of iron TAML D is shown in Figure 5.
FIGURE 5 Synthetic route of iron tetraamido macrocyclic ligand D

LI ET AL.
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cooling device was removed, the system was restored to
room temperature, the reaction continued for 8 hours
under the protection of nitrogen, the solid was filtered
and washed with ethanol to obtain the yellowish brown
solid D. Yield: 69% (0.095 g). FT-IR (KBr): 3388, 2959,
1522 (Ph), 1430 (Ph), 1326, 1263, 1086, 1051,
867, 800 cmꢁ1. ESI-HRMS [M + H]+ m/z: calcd for
+
C28H17FeN4O4 529.0599, found 529.0735. Elemental
analysis: C, 62.83; H, 3.01; N, 10.47; found (%): C,
63.25; H, 3.57; N, 9.86.
2.6 | Activity test method of four catalyst
Methylene blue, methyl orange, and rhodamine B were
used as dyes; 50-ml dye aqueous solution with a certain
mass concentration were prepared. The maximum
absorption wavelengths of three dyes were scanned with
an ultraviolet (UV) spectrophotometer to determine and
measure the initial absorbance value at the maximum
absorption wavelength as A0. Use Na2CO3/NaHCO3
buffer to adjust different pH values. Under certain condi-
tions, add different amounts of iron diamide diamino
acyclic ligand catalyst, add different amounts of H2O2 to
initiate the reaction, at different moments, use an UV
spectrophotometer to measure the absorbance At of the
solution, and use Formula (1) to calculate the decoloriza-
tion rate at the corresponding moment.
A0 ꢁAt
Decolorization rate% ¼
ꢂ 100%:
ð1Þ
A0
The method for measuring chemical oxygen demand
(COD) was carried out in accordance with the national
standard GB 11914-89 (determination of COD in water
quality). Use Equation (2) to calculate COD value.
Deionized water (20 ml) was added to
a 250-ml
reaction flask, followed by HgSO4 (0.4 g), standard
potassium dichromate solution (10 ml), and standard
H2SO4-Ag2SO4 solution (30 ml). After heating to reflux
for 2 h, the solution was cooled to room temperature,
add 90-ml deionized water, and two drops of Ferroin
solution was added as an indicator. Titration system
with 0.1-mol/L ammonium ferrous sulfate standard
solution and the volume of the consumed ammonium
ferrous sulfate was recorded as V0. The water sample
to be tested is treated as described above, and the
volume of the consumed ammonium ferrous sulfate is
recorded as V1.
FIGURE 6 (a) The degradation of methylene blue under the
conditions of Ccatalyst A = 0.056 mM, pH = 6, and 20ꢀC. (b) The
degradation of methyl orange under the conditions of
C
catalyst A = 0.278 mM, pH = 6, and 20ꢀC. (c) The degradation of
rhodamine B under the conditions of Ccatalyst A = 0.278 mM,
pH = 8, and 20ꢀC. The decolorization rate varies with the amount
of H2O2 and time
In the above formula, V is the water sample volume (ml),
and c is the concentration of ammonium ferrous sulfate
(mol/L).
CODCr ¼ ½ðV0 ꢁV1Þꢂcꢂ8ꢂ1000ꢃ=V:
ð2Þ

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LI ET AL.
3 | RESULT AND DISCUSSION
exceeds a certain value, increasing the concentration of
hydrogen peroxide has little effect on the decolorization.
According to the catalyst to catalyze the optimal
effect of dye decolorization, optimal reaction conditions
3.1 | Degradation of dyes by acyclic
catalyst a
C
hydrogen peroxide = 46 mM and the optimal concentration
Test pH = 6, 7, 8, 9, 10, and 11; the acyclic catalyst A
concentration is 0, 0.0056, 0.028, 0.056, 0.167, 0.278, and
0.56 mM; and hydrogen peroxide concentration is 0, 6.5,
19.5, 33, 46, and 65 mM. The decolorization of a dye of
methylene blue, methyl orange, and rhodamine B
changes with time.
It can be seen in Figure 6a that the degradation of
methylene blue is very weak without adding H2O2.
With the increase of the concentration of H2O2,
the decolorization rate is also increasing. According
to the economic effect, optimal reaction conditions
of acyclic catalyst A is 0.167 mM. The degradation reac-
tion has good decolorization effect at pH = 6–11. Most of
the discoloration can be completed within 5 min, and the
decolorization rate can reach 94.56%.
Resting catalysts may undergo acid-induced deactiva-
tion, and active catalysts may undergo intramolecular
dimerization or intermolecular degradation. The catalytic
reaction mechanism is shown in Figure 7.[37]
3.2 | Degradation of dyes by acyclic
catalyst B
C
hydrogen peroxide = 19.5 mM and the optimal concentra-
tion of acyclic catalyst A are 0.056 mM. The degradation
reaction has good decolorization effect at pH = 6–11.
Most of the discoloration can be completed within
20 min, and the decolorization rate can reach 97.58%.
It can be seen in Figure 6b that the degradation of
methyl orange is very weak without adding H2O2.
Increasing the concentration of hydrogen peroxide can
increase the concentration of high valent iron and •OH
in the reaction system, so that the dye degradation is
faster. However, when the concentration of H2O2 exceeds
46 mM, the decolorization rate will be slightly reduced.
The reason is that the excessive hydrogen peroxide com-
petes with the substrate and combines with the high val-
ent iron produced in the reaction process, resulting in the
reduction of the reaction rate and decolorization rate.
According to the economic effect, optimal reaction condi-
tions Chydrogen peroxide = 33 mM and the optimal concen-
tration of acyclic catalyst A is 0.278 mM. With the
increase of pH, the decolorization rate decreased slightly.
Most of the discoloration can be completed within 5 min,
and the decolorization rate can reach 81.53%.
The result showed that the decolorization rate of methy-
lene blue, methyl orange, and rhodamine B dye changed
with time when pH = 8, 9.5, and 11, the concentration of
acyclic catalyst B was 0.75 mM, and the concentration
of H2O2 was 33 mM, 20ꢀC.
It can be seen in Figure 8a that the decolorization rate
decreases slightly with the increase of pH. This is because
hydrogen peroxide is a weak acid, which will be partially
decomposed in a strong alkaline environment, resulting
in a decrease in the number of hydroxyl radicals pro-
duced, and the effect of catalyzing dye fading becomes
slightly weaker. The overall degradation is basically sta-
ble in about 1 h, and the degradation of methylene blue
can reach 80.33%.
It can be seen from Figure 8b that the degradation
effect of the acyclic catalyst B for methyl orange is rela-
tively weak, and the decolorization rate decreases slightly
with the increase of pH value. The overall degradation is
basically stable in about 1 h, and the degradation rate of
methyl orange can reach 53.33%.
It can be seen from Figure 6c that rhodamine B is
degraded weakly without adding H2O2, and the dye deg-
radation is faster with the increase of H2O2 concentra-
tion. When the concentration of hydrogen peroxide
It can be seen from Figure 8c that the decolorization
rate decreases slightly with the increase of pH value, and
the degradation of rhodamine B is located in the middle
of methyl orange and methylene blue. The overall
FIGURE 7 General mechanism of FeIII
TAML activator catalysis adopted for
mathematical treatment
-

LI ET AL.
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3.3 | Degradation of dyes by FeIII-TAML
catalyst C and FeIII-TAML catalyst D
When the concentration of FeIII-TAML catalyst C is
0.4 mM, the concentration of H2O2 is 33 mM, pH = 9,
and the degradation rates of methylene blue, methyl
orange, and rhodamine B are 50.34%, 32.28%, and
43.86%, respectively.
When the concentration of FeIII-TAML catalyst D is
0.38 mM, the concentration of H2O2 is 33 mM, pH = 9,
and the degradation rates of methylene blue, methyl
orange and rhodamine B are 52.37%, 40.15%, and 45.71%,
respectively.
3.4 | Treatment of three kinds of
simulated dye sewage
In this paper, methylene blue, methyl orange, and rhoda-
mine B (Figure 9) simulated dye wastewater were treated
with the optimum reaction conditions of four catalysts A,
B, C, and D. The decolorization rate and COD removal
rate were determined after 120 min. The results are
shown in Tables 1 and 2, respectively.
Table 3 compares five different catalysts to decolorize
dyes. Acyclic catalyst A and the second-generation FeIII-
TAML catalyst catalytic dye degradation effects are basi-
cally the same. The structure of acyclic catalyst B and
acyclic catalyst A is very similar. Acyclic catalyst B is
slightly less effective than acyclic catalyst A. The degrada-
tion effect of FeIII-TAML catalyst C and D is poor.
The structure of the four catalysts shows that the big-
gest difference between acyclic catalyst A and acyclic cat-
alyst B is that the acyclic catalyst A is relatively small, the
acyclic catalyst B is relatively large, and there is a Gemini
effect of isopropyl group. The structure of acyclic catalyst
A is similar to that of acyclic catalyst B, and the structure
is relatively stable. Under alkaline conditions, B is easier
to degrade itself, so the degradation effect of acyclic
catalyst A is slightly worse. For Fe-TAML catalysts C
and D, because the Fe-TAML conjugated structure and
rigid structure of the polyaromatic ring are too strong,
the fat solubility and water solubility are extremely poor.
Therefore, when the dye wastewater is degraded, the
solubility in the system is very poor, and its catalytic
effect is better than that of acyclic catalyst A and B
is weaker.
FIGURE 8 The decolorization rate of three different dyes
varies with time under different pH values
In terms of organic synthesis, the total yield of A is
71.33%, the total yield of B is 61.39%, the total yield of C
is 38.49%, and the total yield of D is 49.11%. Based on
the comprehensive cost and treatment effect, acyclic
catalyst A and acyclic catalyst B have great practical
value.
degradation is basically stable in about 1 h, and the
degradation rate of rhodamine B was 48.33%.
The full-wavelength UV absorption of acyclic catalyst
A and acyclic catalyst B degrading three kinds of dye
wastewater can be viewed in the supporting information.

10 of 11
LI ET AL.
FIGURE 9 Structural
formulas of three dyes
TABLE 1 Degradation effect of
Dye
Methylene blue
Methyl orange
Rhodamine B
acyclic catalyst A
λmax (nm)
664
463
553
Decolorization rate (%)
COD removal rate (%)
97.58
60.7
81.53
52.2
94.56
54.8
TABLE 2 Degradation effect of
Dye
Methylene blue
Methyl orange
Rhodamine B
acyclic catalyst B
λmax (nm)
664
463
553
Decolorization rate (%)
COD removal rate (%)
80.33
57.8
53.33
45.8
48.33
44.6
TABLE 3 Decolorization rate of the
second-generation FeIII-TAML catalyst
and the catalyst A–D for degradation of
three dyes
Methylene blue
Methyl orange
Rhodamine B
FeIII-TAML catalyst
Acyclic catalyst A
98.9
97.6
80.3
50.3
52.4
79.3
81.5
53.3
32.3
40.2
95.4
94.6
48.3
43.9
45.7
Acyclic catalyst B
FeIII-TAML catalyst C
FeIII-TAML catalyst D
4 | CONCLUSION
ACKNOWLEDGMENTS
This work was supported by the National Natural Science
Foundation of China (No. 21272022). The authors grate-
fully acknowledge professor Wang Qing for her contribu-
tion to this project.
Iron coordination compounds are used to catalyze the
degradation of organic pollutants in water by hydrogen
peroxide. The new simplified acyclic iron tetraamido
coordination compound designed and synthesized in this
paper has a good effect on the treatment of simulated dye
wastewater. The cost of synthesis is much lower than that
of the first and second-generation FeIII-TAML catalysts.
The catalytic effect of acyclic catalyst A and acyclic cata-
lyst B is similar to that of the first- and second-generation
catalysts, so they may have high commercial value. In
addition, multiple phenyl FeIII-TAML catalysts C and D
were synthesized, but the catalytic activity is weaker than
that of acyclic catalyst A and B due to poor solubility.
Next, we will continue to design other new iron
tetraamido coordination compounds to further simplify
their structures and optimize their yields, so as to
improve their stability in water.
AUTHOR CONTRIBUTIONS
Shun-Lai Li: Conceptualization; investigation; re-
sources; software; supervision. Run Zhou: Formal analy-
sis; investigation; supervision; visualization. Wei-Jing
Zhao: Conceptualization; investigation.
ORCID
Shun-Lai Li https://orcid.org/0000-0001-9830-6902
Run Zhou https://orcid.org/0000-0002-1350-5409
Wei-Jing Zhao https://orcid.org/0000-0002-0851-9136
Hong-Guang Du https://orcid.org/0000-0003-3237-4261
REFERENCES
DATA AVAILABILITY STATEMENT
Additional supporting information may be found online
in the supporting information section at the end of this
article.
[1] A. Pal, K. Y.-H. Gin, A. Y.-C. Lin, M. Reinhard, Sci. Total Envi-
ron. 2010, 408, 6062.
[2] C. Qian, J.-J. Yin, J.-X. Zhao, X.-T. Li, S.-F. Wang, Z.-H. Bai,
T.-F. Jiao, Colloid Surface a. 2021, 610, 125752.

LI ET AL.
11 of 11
[3] H.-J. Zhao, R. Wang, H.-Z. Deng, L.-J. Zhang, L.-L. Gao, L.-X.
Zhang, T.-F. Jiao, ACS Omega 2021, 6, 294.
[4] P. Zarringhadam, S. Farhadi, J. Alloy. Compd. 2017, 729, 1046.
[5] A. Khataee, L. Alidokht, A. Hassani, S. Karaca, Adv. Environ.
Res. 2013, 2, 291.
[6] A. Hassani, P. Eghbali, B. Kakavandi, K.-Y. A. Lin, F.
Ghanbari, Environ. Technol. Innov. 2020, 20, 101127.
[7] F. Ghanbari, F. Zirrahi, D. Olfati, F. Gohari, A. Hassani,
J. Mol. Liq. 2020, 310, 113217.
[8] M. Canals, R. Gonzalez-Olmos, M. Costas, A. Company,
Environ. Sci. Technol. 2013, 47, 9918.
[9] H.-C. Li, C. Shan, W. Li, B.-C. Pan, Water Res. 2018, 147, 233.
[10] H.-H. Kim, H. Lee, D. Lee, Y.-J. Ko, H. Woo, J. Lee, C. Lee,
A. L.-T. Pham, Environ. Sci. Technol. 2020, 54, 15424.
[11] A. Hassani, M. Faraji, P. Eghbali, J. Photoch. Photobio. A. 2020,
400, 112665.
[12] P. Y. Motlagh, A. Khataee, T. S. Rad, A. Hassani, S. W. Joo, J.
Taiwan, Inst. Chem. E. 2019, 101, 186.
[13] A. Babuponnusami, K. Muthukumar, J. Environ. Chem. Eng.
2014, 2, 557.
[14] M. R. Mills, A. C. Weitz, D. Z. Zhang, M. P. Hendrich, A. D.
Ryabov, T. J. Collins, Inorg. Chem. 2016, 55, 12263.
[15] A. Ghosh, A. D. Ryabov, S. M. Mayer, D. C. Horner, D. E.
Prasuhn, S. S. Gupta, L. Vuocolo, C. Culver, M. P. Hendrich,
C. E. F. Rickard, R. E. Norman, C. P. Horwitz, T. J. Collins,
J. Am. Chem. Soc. 2003, 125, 12378.
[16] G. R. Warner, M. R. Mills, C. Enslin, S. Pattanayak, C. Panda,
T. K. Panda, S. S. Gupta, A. D. Ryabov, T. J. Collins, Chem
2015, 21, 6226.
[26] G. R. Warner, Y. Somasundar, K. C. Jansen, E. Z. Kaaret, C.
Weng, A. E. Burton, M. R. Mills, L. Q. Shen, A. D. Ryabov, G.
Pros, T. Pintauer, S. Biswas, M. P. Hendrich, J. A. Taylor, F. S.
Vom Saal, T. J. Collins, ACS Catal. 2019, 9, 7023.
[27] C. Wang, J. Gao, C. Gu, Environ. Sci. Technol. 2017, 51, 488.
[28] N. Modirshahla, M. A. Behnajady, R. Rahbarfam, A. Hassani,
Clean-Soil Air Water. 2012, 40, 298.
[29] Y. B. Onundi, B. A. Drake, R. T. Malecky, M. A. DeNardo,
M. R. Mills, S. Kundu, A. D. Ryabov, E. Beach, C. P. Horwitz,
M. T. Simonich, L. Truong, R. L. Tanguay, L. J. Wright, N.
Singhal, T. J. Collins, Green Chem. 2017, 19, 4234.
[30] M. R. Mills, K. Arias-Salazar, A. Baynes, L. Q. Shen, J.
Churchley, N. Beresford, C. Gayathri, R. R. Gil, R. Kanda, S.
Jobling, T. J. Collins, Sci. Rep. 2015, 12, 10511.
[31] S. Kundu, A. Chanda, J. V. K. Thompson, G. Diabes, S.
Khetan, A. D. Ryabov, T. J. Collins, Catal. Sci. Technol. 2015,
5, 1775.
[32] R. Wang, J. Bai, Y.-P. Li, Q.-Y. Zeng, J.-H. Li, B.-X. Zhou,
Nano-Micro Lett. 2017, 9, 14.
[33] A. C. Weitz, M. R. Mills, A. D. Ryabov, T. J. Collins, M. P.
Hendrich, Inorg. Chem. 2019, 58, 2099.
[34] Y. Somasundar, L. Q. Shen, A. G. Hoane, L. L. Tang, M. R.
Mills, A. E. Burton, A. D. Ryabov, T. J. Collins, J. Am. Chem.
Soc. 2018, 140, 12280.
[35] X.-Y. Lu, X.-X. Li, M. S. Seo, Y.-M. Lee, M. Clémancey, P.
Maldivi, J.-M. Latour, R. Sarangi, S. Fukuzumi, W. Nam,
J. Am. Chem. Soc. 2019, 141, 80.
[36] S.-L. Li, L.-Y. Wang, R. Zhou, C. Zhou, H.-G. Du, J. Coord.
Chem. 2020, 73, 217.
[17] W. C. Ellis, C. T. Tran, R. Roy, M. Rusten, A. Fischer, A. D.
Ryabov, B. Blumberg, T. J. Collins, J. Am. Chem. Soc. 2010,
132, 9774.
[37] M. A. DeNardo, M. R. Mills, A. D. Ryabov, T. J. Collins, J. Am.
Chem. Soc. 2016, 138, 2933.
[18] T. J. Collins, A. D. Ryabov, Chem. Rev. 2017, 117, 9140.
[19] N. P. V. Leest, M. A. Tepaske, B. Venderbosch, J.-P. H.
Oudsen, M. Tromp, J. I. V. D. Vlugt, B. D. Bruin, ACS Catal.
2020, 10, 7449.
[20] N. P. V. Leest, M. A. Tepaske, J.-P. H. Oudsen, B.
Venderbosch, N. R. Rietdijk, M. A. Siegler, M. Tromp, J. I.
V. D. Vlugt, B. D. Bruin, J. Am. Chem. Soc. 2020, 142, 552.
[21] X.-Y. Lu, X.-X. Li, Y.-M. Lee, Y.-R. Jang, M. S. Seo, S. Hong,
K.-B. Cho, S. Fukuzumi, W. Nam, J. Am. Chem. Soc. 2020, 142,
3891.
[22] D. G. Karmalkar, X.-X. Li, M. S. Seo, M. Sankaralingam, T.
Ohta, R. Sarangi, S. Hong, W. Nam, Chem. – Eur. J. 2018, 24,
17927.
[23] A. Das, J. E. Nutting, S. S. Stahl, Chem. Sci. 2019, 10, 7542.
[24] K. K. Singh, M. K. Tiwari, B. B. Dhar, K. Vanka, S. S. Gupta,
Inorg. Chem. 2015, 54, 6112.
SUPPORTING INFORMATION
Additional supporting information may be found online
in the Supporting Information section at the end of this
article.
How to cite this article: Li S-L, Zhou R,
Zhao W-J, Du H-G. Synthesis of novel acyclic and
multiple phenyl iron tetraamino ligand catalysts
and its catalytic activity for degradation of dye
wastewater by H2O2. Appl Organomet Chem. 2021;
e6252. https://doi.org/10.1002/aoc.6252
[25] F. Napoly, R. Kieffer, L. Jean-Gérard, C. Goux-Henry, M.
Draye, B. Andrioletti, Tetrahedron Lett. 2015, 56, 2517.