Polyoxidovanadate complexes: synthesis, structures and catalytic oxidative bromination of phenol red

Article abstract of DOI:10.1080/00958972.2016.1247445

By selecting appropriate ligands, two polyoxidovanadate complexes, [Ni(en)₂]₃[V₁₈O₄₂Cl]·7H₂O·2H₃O⁺ (1) and [H₂N(CH₃)₂]₃[PV₁₄O₄₂]·2TMP·6H₃O⁺ (2), have been synthesized at different pH values using V₂(SO₄)₃, Ni(CH₃COO)₂, and H₆TTHA (for 1), VO(acac)₂ and TPP (for 2) (en?=?C₂H₈N₂, TPP?=?thiamine pyrophosphate, TMP?=?thiamine monophosphate, H₆TTHA?=?1,3,5-triazine-2,4,6-triamine hexaacetic acid). The complexes have been characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis (TG), and single crystal X-ray diffraction. The complexes catalyze the oxidation of the organic substrate phenol red in the presence of H₂O₂ and bromide, and the reaction system is considered as a model for hydrogen peroxide determination. The reaction rate constants (k) for 1 and 2 are calculated as 3.729?×?10³ and 4.083?×?10³ (mol?L)^?2?s^?1. The maximum conversion rate of phenol red for 1 is 83.32%, while for 2 is 81.12%.

Full text of DOI:10.1080/00958972.2016.1247445

Journal of Coordination Chemistry
ISSN: 0095-8972 (Print) 1029-0389 (Online) Journal homepage: http://www.tandfonline.com/loi/gcoo20
Polyoxidovanadate complexes: Synthesis,
structures and catalytic oxidative bromination of
phenol red
Xiao-Meng Lin, Xiao-Dong Feng, Yang Wang, Yong-Heng Xing, Li-Xian Sun, Si-
Yue Wei & Zhan Shi
To cite this article: Xiao-Meng Lin, Xiao-Dong Feng, Yang Wang, Yong-Heng Xing, Li-Xian
Sun, Si-Yue Wei & Zhan Shi (2016): Polyoxidovanadate complexes: Synthesis, structures
and catalytic oxidative bromination of phenol red, Journal of Coordination Chemistry, DOI:
10.1080/00958972.2016.1247445
To link to this article: http://dx.doi.org/10.1080/00958972.2016.1247445
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Date: 12 October 2016, At: 05:15

Publisher: Taylor & Francis
Journal: Journal of Coordination Chemistry
DOI: http://dx.doi.org/10.1080/00958972.2016.1247445
Polyoxidovanadate complexes: Synthesis, structures and catalytic oxidative
bromination of phenol red
XIAO-MENG LIN†, XIAO-DONG FENG†, YANG WANG†, YONG-HENG XING*†, LI-XIAN SUN‡,
SI-YUE WEI‡ and ZHAN SHI§
#
†
College of Chemistry and Chemical engineering, Liaoning Normal University, Huanghe Road 850 ,
Dalian, 116029, P.R. China
Guangxi Key Laboratory of Information Materials, Guilin University of Electronic Technology,
Guilin, 541004, P.R. China
State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University,
‡
§
Changchun, 130012, P. R. China
By selecting appropriate ligands, two polyoxidovanadate complexes,
+
+
[
Ni(en) ] [V O Cl]·7H O·2H O (1) and [H N(CH ) ] [PV O ]·2TMP·6H O (2), have been
2
3
18 42
2
3
2
3 2 3
14 42
3
synthesized at different pH values using V (SO ) , Ni(CH COO) and H TTHA (for 1),
2
4 3
3
2
6
VO(acac)
2
and TPP (for 2) (en = C
2 8 2
H N , TPP = thiamine pyrophosphate, TMP = thiamine
monophosphate, H
6
TTHA = 1,3,5-triazine-2,4,6-triamine hexaacetic acid). The complexes have
been characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis (TG) and
single crystal X-ray diffraction. The complexes catalyze the oxidation of the organic substrate
phenol red in the presence of H O and bromide, and the reaction system is considered as a
2
2
model for hydrogen peroxide determination. The reaction rate constants (k) for 1 and 2 are
*Corresponding author. Email: xingyongheng2000@163.com
1

3
3
-2 -1
calculated as 3.729×10 and 4.083×10 (mol/L) s . The maximum conversion rate of phenol red
for 1 is 83.32%, while for 2 is 81.12%.
Keywords: Oxidovanadium clusters; Crystal structures; Haloperoxidases; Mimicking
bromoperoxidase; Hydrogen peroxide determination
1
. Introduction
The chemistry of oxidovanadium clusters has applications in many fields, such as catalysis,
medicine, electrical conductivity, magnetism, etc. [1-3]. Researchers found that oxidovanadium
clusters are effective in oxidative bromination [4-9]. Oxidovanadium clusters can also be
recognized as potential functional models of vanadium haloperoxidases (V-HPOs), which
accelerate the oxidative halogenation of organic complexes in the presence of organic
hydroperoxides, hydrogen peroxide or molecular oxygen. There were disadvantages of natural
V-HPOs, such as digestion by proteases, expensive preparation and purification. However,
artificial enzyme mimics of vanadium clusters have potential to be more stable, available and
exhibit better bioactivity.
Oxidovanadium clusters have varied structural units such as square pyramidal, tetrahedral,
trigonal bipyramidal and octahedral. Vanadium polyhedra have capacity to polymerize, giving
chains, rings, layers, clusters and 3D frameworks [10]. There are many types of oxidovanadium
2
-
4-
3-
6-
8-
6-
4-
clusters, such as [V O ] , [V O ] , [V O ] , [V O ] , [V O ] , [V O ] , [V O ] , etc.
2
6
4
12
5
14
6
18
6
19
10 28
12 32
4
-
[
[
[
[
11]. Most clusters have cage structures. Others extend to ring, such as [V
4
O
12] , or bowl,
32] , etc. The typical ring cluster anion
V O ] is composed of four vanadium oxide tetrahedra connected by sharing corners, while
1
3-
16-
4-
5 8
V O17] , or ribbon, [V O24] , or basket, [V12O
4
-
4
12
6
-
V O ] is composed of vanadium oxide octahedra connected by sharing edges. Using
1
0
28
hydrothermal syntheses, a large number of chain-like, layered, porous oxidovanadium clusters
with high polymerization degree have been prepared and characterized as single crystals. Many
4
oxidovanadium clusters are connected to form a multidimensional network based on {V O12},
2

{
V
10
O
28}, {V15
O
36}, {V16
O
38}, etc., by using transition metal ions as bridges. For example,
2
+
Zubieta used [Cu(enMe)
2
] as bridging groups [12]; the [V15O36Cl] cage structure was
connected to form a two-dimensional structure. Ji-Qing Xu et al. reported
2
+
Ni(en) {V O Cl[Ni(en) ] }⋅8.5H O [13] using [Ni(en) ] as bridging groups to form a
3
16 38
2 3
2
2
three-dimensional network structure. The polymer is closely related to the synthetic conditions,
with pH recognized as a major factor [14-16].
Thiamine (vitamin B1) in its pyrophosphate form (TPP) [17] is a coenzyme for a number
of metabolic enzymes in catalyzing the decarboxylation of α-keto acids (ketoglutaric acid,
pyruvic acid and the like) [18-21] or the transfer of aldehyde or acyl groups. In carbohydrate
metabolic reactions, the decarboxylation of α-keto acids is an important intermediate process.
The catalytic function of TPP and analogue TMP depends on three parts of its structure, the
thiazole ring, the pyrimidine ring and the pyrophosphate/monophosphate group [22, 23].
Through study of the structural properties of complexes of TPP and TMP, they can be divided
into two categories: (i) the ionic salts without metal bonding to the thiamine directly [24-29] and
(ii) the metal directly linked to N of the thiamine [30-34]. There are many biological applications
of vanadium and small molecules, while few works about oxidovanadium clusters with
biomolecule have been reported. In order to study the role of the vanadium in biology, in this
work, we selected TPP/TMP and vanadium as starting materials to design a combination of
vanadium and biomolecule. We hope the diversity of oxidovanadium cluster structures can lead
to functional properties of the complexes.
+
Two oxidovanadium clusters, [Ni(en)
2
]
3
[V18
O
42Cl]·7H
2
O·2H
3
O (1) and
+
[H
2
N(CH
3
)
2
]
3
[PV14
O
42]·2TMP·6H
3
O (2), were synthesized. Their structures have been
determined by single crystal diffraction and also confirmed by elemental analysis and IR
spectroscopy. Catalytic bromination dynamics of the oxidovanadium clusters and the potential
detection of hydrogen peroxide in water are studied.
3

2
2
. Experimental
.1. Materials and methods
Elemental analyses for C, H and N were carried out on a Perkin Elmer 240C automatic analyzer.
Infrared spectra were recorded on a Bruker AXS TENSOR−27 FT−IR spectrometer with KBr
−
1
pellets from 4000−400 cm . X-ray powder diffraction data were collected on a Bruker AXS D8
Advance diffractometer using Cu–Kα radiation (λ = 1.5418 Å) in the 2θ range of 5–60° with a
step size of 0.02° and a scanning rate of 3°/min. Thermogravimetric analyses (TG) were
-1
performed with a heating rate of 10 °C min on a Perkin Elmer Diamond TG/DTA.
2
.2. Synthesis
+
2
.2.1. [Ni(en) ] [V O Cl]·7H O·2H O (1). A mixture of V (SO ) (0.01 g, 0.025 mmol),
2
3
18 42
2
3
2
4 3
Ni(CH
3
COO)
2
(0.0124 g, 0.07 mmol), H
6
TTHA (0.0118 g, 0.025 mmol) and deionized water
(10 mL) was loaded into a Pyrex flask. Two drops of en were added to adjust pH to 9. After the
solution was stirred at room temperature for 3 h, the Pyrex flask was sealed and heated at 120 °C
for one day, and then cooled to room temperature. Finally, black crystals were obtained in ca. 76%
yield based on V (SO ) . Elemental Analysis (%) Calcd. for C H O N ClNi V : C, 6.19; H,
2
4 3
12 68 51 12
3
18
2
.92; N, 7.22. Found: C, 6.22; H, 2.87; N, 7.21%.
+
2
.2.2. [H N(CH ) ] [PV O ]·2TMP·6H O (2). A mixture of TPP (0.0230 g, 0.05 mmol),
2
3 2 3
14 42
3
VO(acac) (0.0265 g, 0.1 mmol), deionized water (6 ml), alcohol (3 ml) and DMF (0.5 ml) was
2
-1
loaded into a Pyrex flask. To this reaction, one drop of HNO (4 mol·L ) was added to adjust pH
3
to 3. After the mixed solution was stirred at room temperature for 3 h, the Pyrex flask was sealed
and heated at 100 °C for three days, and then cooled to room temperature. Finally, black crystals
were obtained in ca. 73% yield based on VO(acac) . Elemental Analysis (%) Calcd. for
2
C H N O P S V : C, 15.27; H, 3.22; N, 6.53. Found: C, 15.31; H, 3.27; N, 6.57%.
30
76 11 56
3
2
14
4

2
.3. X-ray crystallographic determination
Suitable single crystals of 1 and 2 were mounted on glass fibers for X-ray measurement.
Reflection data were collected at room temperature with a Bruker AXS SMART APEX II CCD
diffractometer (Bruker AXS, Germany) with graphite-monochromated Mo-K radiation (l =
α
0
.7107 Å) and a ω scan mode. All measured independent reflections (I > 2 sigma (I)) were used
in the structural analysis and semi-empirical absorption corrections were applied using SADABS
35]. The structures were solved by the direct method using SHELXL-97 [36]. All non-hydrogen
[
atoms were refined anisotropically and by temperature factor with the full-matrix least squares
method. Hydrogens of the organic frameworks were fixed at calculated positions with isotropic
thermal parameters and refined using a riding model. Hydrogens of free water molecules were
found in the difference Fourier map. Crystal data and structure refinements are shown in table 1.
Selected bond lengths and angles are listed in tables S1 and S2. Hydrogen bonds of 1 and 2 are
given in table 2.
2
.4. Measurement of mimic catalytic bromination dynamics in solution
The reactions were initiated with the presence of phenol red solution, KBr, vanadium complex
and H with a buffer solution of NaH PO –Na HPO [37] (pH = 5.8). UV spectral changes
2
O
2
2
4
2
4
were recorded using a UV-1000 spectrophotometer at 5 min intervals. By sequentially collecting
the UV absorption spectrum data during the reaction and carrying out data treatment and fitting,
the bromine reaction rate constants of vanadium complexes were obtained by the method in the
literature [8, 38-42].
3
3
. Results and discussion
.1. Synthesis
Two oxidovanadium clusters have been synthesized by hydrothermal reactions. V (SO ) was
2
4 3
employed to synthesize 1, while VO(acac) to 2. Complex 1 was generated in 10 mL water and
2
kept at 120 °C, while 2 was in mixed solution of alcohol, water and DMF and kept at 100 °C.
5

The complexes skeletons also different with 18 vanadium ions in 1, while 14 in 2. A free chloride
was found in 1, although we did not add chloride during the synthesis. We assumed this may be
due to the impurities in H TTA. Although the raw materials of vanadium were trivalent and
6
tetravalent, the valence states of final products were converted to tetravalent and pentavalent,
respectively, from oxidation of vanadium by air at higher temperature. Complexes 1 and 2 are
stable at room temperature and can be easily dissolved in DMF.
3
3
.2. Structure descriptions
.2.1. [Ni(en) ] [V O Cl]·7H O·2H O (1). Single-crystal X-ray diffraction analyses reveal
+
2
3
18 42
2
3
that 1 crystallizes in the monoclinic, space group C2/c. The molecular unit of 1 consists of
8
-
2+
[V
18
O
42Cl] , three [Ni(en)
2
] , seven free water molecules and two free hydronium ions. In the
V
18
O42Cl skeleton, vanadiums (V1, V6 and V9) were five-coordinate with four
tridentate-bridging oxygens and one bidentate-bridging oxygen, other vanadiums were
five-coordinate with four tridentate-bridging oxygens and a terminal oxygen to form a distorted
square pyramidal geometry. Nickel ions were six-coordinate with four nitrogens from two en
ligands and two bidentate-bridging oxygens to form a distorted octahedral geometry. Combining
2
+
nickel ion and ethylenediamine to form a bridging linker group [Ni(en)
2
] , each anionic cluster
2
+
V O Cl was surrounded by six [Ni(en) ] groups and connected to the adjacent V O Cl
1
8
42
2
18 42
skeleton to form a 2D sheet structure (figure 1c). There is a chloride in the center of the V O Cl
1
8
42
skeleton. The interaction contact between chloride and O7, O8, O9 as well as O10 is 3.6457
0.0082) Å, 3.6033 (0.0079) Å, 3.6058 (0.0062) Å and 3.6058 (0.0063) Å, respectively. V-O
bond lengths ranged from 1.617(7) to 1.962(6) Å. V=O bond lengths ranged from 1.596(7) to
.617(7) Å. Ni-N bond lengths ranged from 2.067(10) to 2.112(9) Å, Ni-O bond lengths ranged
from 2.101(6) to 2.148(6) Å.
In the packing structure, there were two kinds of hydrogen bonding, as illustrated in
table 2: (i) hydrogen bonding of N-H···O between N from en and O from terminal oxygen (O19),
(
1
#
4
#7
free water (O2W) and bridged oxygen (O4, O8, O9): N4-H4B···O19 , N3-H3B···O2W ,
6

#
2
#3
N5-H5A···O4 , N1-H1A···O9 , N2-H2A···O8; (ii) hydrogen bonding of O-H···O between
#
5
oxygens from free water (O3W, O4W), and terminal oxygen (O15, O17): O3W-H3WB···O17 ,
#
6
#4
O4W-H4WB···O15 . By the hydrogen bonding of N4-H4B···O19 , the 2D sheets are further
connected to form a 3D supramolecular network structure (figure 1d).
+
3
.2.2. [H
2
N(CH
3
)
2
]
3
[PV14
O
42]·2TMP·6H
3
O (2). Single-crystal X-ray diffraction analyses
reveal that 2 crystallizes in the monoclinic, space group C2/c. The molecular unit of 2 consists of
9
-
+
a [PV O ] , two free TMP, three [H N(CH ) ] from decomposed DMF and six free hydronium
1
4
42
2
3 2
9
-
ions. The structure of [PV O ] is shown in figure 2a with the central PO tetrahedron sharing
1
4
42
4
its oxygens with four V O groups, each of which is constructed from three edge-sharing VO
6
3
13
3
octahedra. The V O13 subunits are connected to each other by corner-sharing. This assembly
produces a slightly distorted α-Keggin framework, capped by two [VO] subunits [43-45]. In the
9
-
structure of [PV O ] , vanadiums (V1 and V6) were six-coordinate with four
1
4
42
bidentate-bridging oxygens, one tetradentate-bridging oxygen and a terminal oxygen to form an
octahedral geometry. Vanadiums (V2, V3, V5 and V7) were six-coordinate with two
bidentate-bridging oxygens, two tridentate-bridging oxygens, one tetradentate-bridging oxygen
and a terminal oxygen to form a distorted octahedral geometry. V4 was five-coordinate with four
tridentate-bridging oxygens and a terminal oxygen to form a distorted square pyramidal
geometry (figure 2b). V=O bond lengths were 1.589(8) to 1.621(8) Å. V-O bond lengths ranged
from 1.767(8) to 2.384(8) Å. P-O bond lengths were 1.536(7) to 1.548(8) Å. In TMP, the
dihedral angle between the thiazole ring and the pyrimidine ring is 80.83 (0.46)°. The torsion
T
angles of thiazole ring and pyrimidine ring are Φ =C6-C8-N6-C9 = -77.25 (1.36)° and
Φ =N6-C8-C6-C7 = 171.98 (1.12)° [46]. So, the molecular configuration of TMP belongs to S
P
configuration [18].
In the packing structure, there are three kinds of hydrogen bonding, as illustrated in
+
table 2: (i) hydrogen bonding of C-H···O: between C from TMP (C5, C8), H
2
N(CH
3
)
2
(C1, C2)
#
2
and O from bridged oxygen (O3, O6, O12), terminal oxygen (O15): C5-H5···O6 ,
7

#
4
#2
C8-H8B···O3 , C8-H8A···O15 , C1-H1B···O15, C2-H2B···O12; (ii) hydrogen bonding of
O-H···O: among O atom from free water molecule (O1W,O3W), TMP (O24) and bridged
#
5
#1
#2
oxygen (O14): O3W-H3WA···O14 , O1W-H1WB···O3W , O24-H24···O1W ; (iii) hydrogen
bonding of N-H···O between N from TMP and O from terminal oxygen (O23) and bridged
#
3
#4
#4
oxygen (O3): N5-H5A···O23 , N5-H5B···O3 . By the hydrogen bonding of C8-H8B···O3
#
2
and C5-H5···O6 , the cluster skeleton PV14
O42 and TMP formed an infinite 1D chain structure
#
3
(
figure 3c). By the hydrogen bonding of N5-H5A···O23 , the 1D chain structures are connected
to form a 2D sheet structure (figure 3d); furthermore, with the same hydrogen bonding
#
3
interaction of N5-H5A···O23 , the 2D structure connected a 3D supramolecular network
structure (figure S1).
3
.3. Infrared spectroscopy
-1
IR spectra of 1 and 2 are listed in figure S2. A broad absorption at 3443 and 3438 cm indicates
-1
the presence of water molecules. An absorption at 3264 cm for 1 is attributed to the stretch of
-1
N-H from en ligand. An absorption at 3083 cm for 2 is attributed to stretch of aromatic nucleus
-1
=
C-H. Absorptions at 2925 and 2858 cm for 1 should be assigned to the stretch of −CH
2
from
-1
-1
en ligand. The peaks at 975 cm for 1 and 950 cm for 2 were attributed to the V=O stretch.
−
1
−1
Absorptions at 870 and 759 cm for 1 and 863 and 758 cm for 2 were characteristic of the
asymmetric stretching vibrations of bridged V-O-V. The symmetric stretching vibrations of
−
1
−1
bridged V-O-V were observed at 670 and 560 cm for 1 and 593 cm for 2.
3
.4. Thermal properties
To examine the thermal stabilities of 1 and 2, thermogravimetric analyses (TG) were carried out
at a heating rate of 10 °C/min under nitrogen from 30-1000 °C (figure S3). In 1, the results show
that the initial weight loss of 6.4% before 296 °C was assigned to the departure of seven free
water molecules and two free hydronium ions (calc: 6.9%). The second step to 826 °C (obs:
1
5.6%) was attributed to removal of six coordinated en ligands (calc: 15.5%). The final residue
8

of complex corresponded to the oxide of vanadium and nickel. For 2, the initial loss of 34.9%
before 905 °C was assigned to loss of six free water hydronium ions and two free TMP (calc:
3
3.8%). The final residue of complex corresponded to the oxide of vanadium and phosphorus.
3
.5. PXRD analysis
In order to confirm whether the crystal structures were truly representative of the bulk materials,
PXRD patterns of 1 and 2 were recorded, as shown in figure S4. The phase of the corresponding
complex was considered as purities owning to the agreement of the peak positions. The different
intensities may be due to the preferred orientation of the powder samples.
3
.6. Catalytic bromination dynamics studies of the oxidovanadium clusters
Vanadium complexes can mimic a haloperoxidase reaction in which vanadium complex
catalyzes the bromination of organic substrates in the presence of bromide and H O [47-51].
2
2
Herein, we investigate the bromination reaction activities of 1 and 2 using phenol red as organic
substrate, which is converted to bromophenol blue during the reaction. By the reaction of
oxidized halogen species with the organic substrate, the halogenated product was produced and
the reaction is shown in scheme 1. The addition of solution of 2 to the standard reaction of
bromide in phosphate buffer with phenol red as a trap for oxidized bromine resulted in color
change from yellow to blue. UV absorption spectra recorded a decrease in absorbance of the
peak at 443 nm due to loss of phenol red and an increase of the peak at 592 nm with production
of bromophenol blue (figure 4), showing that 2 has significant catalytic activity. The mimic
catalytic activity for 1 is similar to that of 2.
O
O
O
O
S
S
Br
Br
O
O
KBr, V Complex
OH
OH
H O
2
2
Br
Br
OH
OH
9

Scheme 1. Reaction for bromination with the complexes.
To investigate the catalytic reaction we use 2 as an example to carry out kinetic studies of
the bromination reaction. According to relationship of the UV absorbance data with the different
reaction time during the reaction, a series of linear plots of the absorbance at 592 nm time
dependence for different concentrations of 2 were obtained (figure 5). Then, using the catalytic
reaction kinetic equation about dc/dt = k ·c x ·c
2
y·c
3
z, the equation was treated into lg(dc/dt) =
lgk+xlgc+ylgc +zlgc . We used dA/dt data (where A = absorbance at 592 nm) corresponding to
2
3
the concentration change of the oxidovanadium complexes as function of -log (dc/dt) vs. –logc
where c = concentration of complex) to obtain a straight line (figure 6) [52-55]. Through the
(
straight line, the slope and intercept were 1.09 and 0.7869, respectively. The former confirmed
that the reaction order was first-order on vanadium. According to the intercept, the reaction rate
3
-2 -1
constant (k) for 2 was calculated as 4.083×10 (mol/L) s . Similar plots for 1 were generated in
the same way (figures 7 and 8), and values of the slope and intercept were 1.06 and 0.8262; the
3
-2 -1
reaction rate constant (k) was 3.729×10 (mol/L) s . Through the experimental results, we
conclude that (i) the reaction orders of the vanadium complexes in the bromination reaction were
close to 1, confirming the first-order dependence on vanadium and (ii) the reaction rate constants
of the two complexes were 2>1 (table 3).
To evaluate the catalytic reaction of phenol red based on vanadium complex as a catalyst,
we have carried out an experiment adding the DMF-water solution of the complexes to the
2 2
reaction system involving phosphate buffer, KBr, H O and phenol red which acted as a substrate
to be brominated, resulting in color change of the solution from yellow to blue. Spectral change
was recorded at 10 min intervals. The loss of mole amount of phenol red was equal to the
increase in amount of bromophenol blue (scheme 1); in the reaction, the conversion of phenol
red indicated the produced amount of bromophenol blue.
According to conversion of phenol red = (1-C /C ) × 100% (1)
t
0
10

where C
could change the conversion of phenol red based on equation 1 into (1-A
equilibrium absorbance, A = initial absorbance).
t
= equilibrium concentration, C
0
= initial concentration, due to relationship of C A, we
t
/A )×100% (A
0
t
=
0
As shown in figure 9, in the reaction, without vanadium complex as catalyst, the
conversion rate of phenol red is lower than that with vanadium complexes as catalyst. The
reaction of 2 is faster than that of 1, consistent with the kinetics results. After 24 h, the reaction
reached equilibrium and the absorbance value almost had no change. For 1, A = 0.4376 and for 2,
t
A = 0.4954; we got a maximum conversion rate of phenol red, 83.32% for 1 and 81.12% for 2,
t
respectively.
3
.7. The effect of the concentration of H
2
2
O on bromination
Hydrogen peroxide plays an important role in our daily life, industry, pharmaceutical production
and clinical physics, especially in catalytic reactions [56-59]. We have studied the dependence of
H O concentration upon the bromination catalytic reaction for developing a new H O detection
2
2
2
2
method. As shown in the experimental results, oxidation catalyzed by the oxidovanadium cluster
complexes is related to H concentration, and the absorbance at 592 nm presents a linear
dependence on the concentration of H along with the formation of bromophenol blue. The
linear absorbance dependence of c(H O ) is obtained (figures 10 and 11); the detection limit
2
O
2
2
O
2
2
2
value of the concentration H O is estimated to be 1.12 mol/L for 1 and 1.1 mol/L for 2 by
2
2
extension of the line. All these observations further confirm that the catalytic reaction system can
be used as a potential method for detection of H
2
2
O .
4
. Conclusion
By selecting appropriate ligands, two new oxidovanadium clusters were synthesized under
different reaction systems by controlling the temperature. We first tested the bromination
reaction activities and finally calculated the reaction rate constants (k) of 1 and 2. The results
verified that they could be considered as potential functional models of vanadium
11

haloperoxidases (V-HPOs). Furthermore, a new colorimetric detection method based on the
catalytic bromination reaction for the detection of H has been proposed; this detection system
2
O
2
is simple and sensitive. We will investigate the application of the detection reaction mechanism
in the future.
Supplementary material
Figures of infrared spectra, TG analysis, PXRD, 3D packing framework and the bond lengths (Å)
and angles (°) are presented in the Supplementary Material. CCDC 1448220-1448221.
Acknowledgements
We are grateful for support provided by the National Natural Science Foundation of China
(Grant Nos. 21371086 and 21571091), and Commonweal Research Foundation of Liaoning
province in China (No. 2014003019), State Key Laboratory of Inorganic Synthesis and
Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012, P.R. China
(Grant No. 2016−02) for financial assistance.
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15

Figure 1. (a) V O Cl building block; (b) Ni(en) building block; (c) a view of a 2D
1
8
42
2
supramolecular network structure; (d) the 3D packing framework of 1.
16

Figure 2. (a) Polyhedral representation of the cluster unit, highlighting the 12 [VO ] octahedra;
6
9–
(b) ball-and-stick representation of the [PV14O42] unit.
17

9
–
Figure 3. (a) [PV O ] unit; (b) free TMP; (c) 1D infinite chain structure formed by the
1
4
42
hydrogen bonds; (d) a view of a 2D supramolecular network structure.
18

Figure 4. Oxidative bromination of phenol red catalyzed by 2. Spectral change was recorded at
-1
1
0 min intervals. The reaction mixture contained phosphate buffer (pH = 5.8), KBr (0.4 mol·L ),
-1
-4
-1
-5
-1
H O (1 mol·L ), phenol red (10 mol·L ) and 2 (2.84×10 mmol·L ).
2
2
19

Figure 5. A series of linear plots of the absorbance at 592 nm versus time for different
-1
-1
concentrations of 1. Conditions used: pH = 5.8, c(KBr) = 0.4 mol·L , c(H O ) = 1 mol·L ,
2
2
-
4
-1
-5
-1
-6
-6
c(phenol red) = 10 mol·L . c(vanadium 2.24×10 mmol·L ) = (a) 1.12×10 ; (b) 2.24×10 ;
-6
-6
-6
(
c) 3.36×10 ; (d) 4.48×10 ; (e) 5.6×10 .
20

Figure 6. –log (dc/dt) dependence of –logc for 1 in DMF-H O at 30±0.5 °C.
2
21

Figure 7. A series of linear plots of the absorbance at 592 nm versus time for different
-1
-1
concentrations of 2. Conditions used: pH = 5.8, c(KBr) = 0.4 mol·L , c(H O ) = 1 mol·L ,
2
2
-
4
-1
-5
-1
-6
-6
c(phenol red) = 10 mol·L . c(vanadium 2.84×10 mmol·L ) = (a) 1.42×10 ; (b) 2.84×10 ;
-6
-6
-6
(
c) 4.26×10 ; (d) 5.68×10 ; (e) 7.1×10 .
22

Figure 8. –log (dc/dt) dependence of –logc for 2 in DMF-H O at 30±0.5 °C.
2
23

Figure 9. The measurable absorbance dependence on time for different complexes at 443 nm.
-
1
The reaction mixture contained phosphate buffer (pH = 5.8), c(KBr) = 0.4 mol·L , c(H
2
O
2
) =
-1
-4
-1
-6
-1
1
8
mol·L , c(phenol red) = 10 mol·L , c(complex 1) = 6.72×10 mmol·L , c(complex 2) =
-6
-1
.52×10 mmol·L .
24

Figure 10. A linear calibration plot of the absorbance at 592 nm on the concentration of H O
2
2
from 1 as catalyzer in DMF – H O at 30 min.
2
25

Figure 11. Linear calibration plot of the absorbance at 592 nm on the concentration of H O from
2
2
2
as catalyzer in DMF–H O at 25 min.
2
26

Table 1. Summary of crystal data and refinement results for 1 and 2*.
Complexes
Formula
1
2
C H ClN Ni O V
C H N O P S V
30 76 11 56 14
2357.21
12
68
12
3
51 18
3
2
-1
M (g mol )
Crystal system
Space group
a (Å)
2325.28
Monoclinic
C2/c
12.8147(8)
26.9244(17)
21.1939(14)
90
Monoclinic
C2/c
20.7551(10)
19.3942(9)
21.4526(12)
90
b (Å)
c (Å)
a (°)
b (°)
92
113.933(6)
90
g (°)
90
3
V (Å )
7304.9(8)
4
7892.8(7)
4
Z
-3
Dcalc (Mg m )
Crystal size (mm)
F(000)
2.112
1.974
0.34 × 0.28 × 0.13
4580
0.42 × 0.34 × 0.33
4762
-
1
μ(Mo-Kα) / mm
θ (°)
3.070
1.800
1.76 to 25.93
19797
3.04 to 25.20
17253
Reflections collected
Independent reflections
Parameters
7090(4744)
442
6970(3523)
530
-3
D(r) (e Å )
3.603 and -1.718
2.956 and -1.213
Goodness-of-fit
1.046
1.021
a
b
b
R
1
0.0670(0.1939)
0.0947(0.2657)
a
b
b
wR2
0.1043(0.2210)
0.1782(0.3121)
a
2
o
2 2
2 2 1/2
o
b
*
R = ΣF – F /ΣF , wR = [Σw(F –F ) /Σw(F ) ] ; F >4σ(F ). Based on
o
c
o
2
c
o
o
all data.
27

Table 2. Bond distances (Å) and angles (°) of hydrogen bonds in 1 and 2*.
D–H···A
d(D–H)/Å d(H···A)/ Å
d(D···A)/ Å ∠D–H···A/°
Complex 1
#
#
5
6
O3W-H3WB...O17
0.85
0.85
0.90
0.90
0.90
0.90
0.90
2.43
1.99
2.21
2.23
2.13
2.21
2.32
2.07(3)
131.8
150.9
149.3
158.7
160.1
149.3
151.2
O4W-H4WB...O15
2.76(2)
#
3
N1-H1A...O9
N2-H2A...O8
3.019(11)
3.086(11)
3.00(4)
#
7
N3-H3B...O2W
#
4
N4-H4B...O19
3.019(11)
3.141(10)
#
2
N5-H5A...O4
Complex 2
#
3
O1W-H1WB···O3W
0.85
0.85
0.82
0.86
0.86
0.96
0.96
0.93
0.97
0.97
2.08
2.38
2.10
2.17
2.07
2.44
2.41
2.49
2.42
2.56
2.80(2)
142.6
102.1
126.6
175.9
166.0
133.4
130.7
140.4
130.2
143.6
#
7
O3W-H3WB...O14
2.689(15)
2.67(2)
#
4
O24-H24...O1W
#
5
N5-H5A...O23
3.03(2)
#
6
N5-H5B...O3
2.907(14)
3.18(4)
C1-H1B...O15
C2-H2B...O12
3.12(3)
#
4
C5-H5...O6
3.259(15)
3.132(15)
3.390(17)
#
6
C8-H8B...O3
#
4
C8-H8A...O15
*
#
#
Symmetry transformation used to generate equivalent atoms for 1: #2 -x+2, y, -z+1/2;
3 -x+1, -y, -z; #4 -x+3/2, -y+1/2, -z; #5 x, y+1, z; #6 -x+1, y, -z+3/2; #7 x+1, y, z; for 2:
3 x+1/2, y+1/2, z; #4 -x+3/2, y+1/2, -z+1/2; #5 x+1/2, y-1/2, z; #6 x, -y+1, z+1/2; #7 x-1/2,
y+1/2, z.
28

Table 3. Kinetic data for 1 and 2 in DMF–H
2
O at 30±0.5 °C.
-
1 -2 -1
Complexes
m
b
k(mol L ) s
3
1
2
1.06
1.09
0.8262
0.7869
3.729×10
3
4.083×10
-1
Conditions used: c(phosphate buffer) = 50 mmol·L , pH = 5.8,
-1
-4
-1
c(KBr) = 0.4 mol·L , c(phenol red) = 10 mol·L . ‘‘x’’ is the
reaction order of the vanadium complex; ‘‘b’’ is the intercept of the
line; ‘‘k’’ is the reaction rate constant for the vanadium complex.
29