Synthesis, characterization, crystal structure, catalytic activity in oxidative bromination, and thermal study of a new oxidovanadium Schiff base complex containing O, N-bidentate Schiff base ligand

Article abstract of DOI:10.1080/00958972.2014.960405

A new oxidovanadium(IV) Schiff base complex, VOL₂ (1), HL = 2-{(E)-[2-(bromoethyl)imino]methyl}-6-methoxy phenol, containing ethyl bromide pendant group was synthesized by direct reaction of HL and VO(acac)₂ in the ratio of 2: 1 in methanol at reflux. The Schiff base ligand and its vanadyl complex were characterized by FT-IR spectra and CHN analysis. Additionally, the Schiff base ligand has been characterized by ¹H NMR spectroscopy. The crystal structure of 1 was also determined by single-crystal X-ray analysis, showing the distorted square-pyramidal N₂O₃ coordination around vanadium(IV). The catalytic activity of 1 was studied in the oxidative bromination of 2-nitrophenol as a model substrate, and different reaction parameters were investigated. The oxidative bromination of some organic compounds in the presence of 1 in optimal conditions showed that it was an effective and selective catalyst in those optimal conditions. Thermogravimetric analysis of 1 showed that it decomposed in two stages. 1 was thermally decomposed in air at 660 °C, and the XRD pattern of the obtained solid showed the formation of the V₂O₅ nanoparticles with average size of 34 nm.

Full text of DOI:10.1080/00958972.2014.960405

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Synthesis, characterization, crystal
structure, catalytic activity in oxidative
bromination, and thermal study of
a new oxidovanadium Schiff base
complex containing O, N-bidentate
Schiff base ligand
Gholamhossein Grivania, Vida Tahmasebia, Aliakbar Dehno
Khalajib, Václav Eignercd & Michal Dušekd
a School of Chemistry, Damghan University, Damghan, Iran
b Faculty of Science, Department of Chemistry, Golestan
University, Gorgan, Iran
c Department of Solid State Chemistry, Institute of Chemical
Technology, Prague, Czech Republic
Click for updates
d Institute of Physics ASCR, v.v.i., Praha 8, Czech Republic
Accepted author version posted online: 23 Sep 2014.Published
online: 10 Oct 2014.
To cite this article: Gholamhossein Grivani, Vida Tahmasebi, Aliakbar Dehno Khalaji, Václav
Eigner & Michal Dušek (2014): Synthesis, characterization, crystal structure, catalytic
activity in oxidative bromination, and thermal study of a new oxidovanadium Schiff base
complex containing O, N-bidentate Schiff base ligand, Journal of Coordination Chemistry, DOI:
10.1080/00958972.2014.960405
To link to this article: http://dx.doi.org/10.1080/00958972.2014.960405
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Journal of Coordination Chemistry, 2014
http://dx.doi.org/10.1080/00958972.2014.960405
Synthesis, characterization, crystal structure, catalytic activity
in oxidative bromination, and thermal study of a new
oxidovanadium Schiff base complex containing
O, N-bidentate Schiff base ligand
GHOLAMHOSSEIN GRIVANI*†, VIDA TAHMASEBI†,
ALIAKBAR DEHNO KHALAJI‡, VÁCLAV EIGNER§¶ and MICHAL DUŠEK¶
†School of Chemistry, Damghan University, Damghan, Iran
‡Faculty of Science, Department of Chemistry, Golestan University, Gorgan, Iran
§Department of Solid State Chemistry, Institute of Chemical Technology, Prague, Czech Republic
¶Institute of Physics ASCR, v.v.i., Praha 8, Czech Republic
(Received 15 March 2014; accepted 16 August 2014)
A new oxidovanadium(IV) Schiff base complex, VOL2 (1), HL = 2-{(E)-[2- (bromoethyl)imino]
methyl}-6-methoxy phenol, containing ethyl bromide pendant group was synthesized by direct reac-
tion of HL and VO(acac)2 in the ratio of 2 : 1 in methanol at reflux. The Schiff base ligand and its van-
adyl complex were characterized by FT-IR spectra and CHN analysis. Additionally, the Schiff base
*Corresponding author. Email: grivani@du.ac.ir
© 2014 Taylor & Francis

2
G. Grivani et al.
ligand has been characterized by 1H NMR spectroscopy. The crystal structure of 1 was also deter-
mined by single-crystal X-ray analysis, showing the distorted square-pyramidal N2O3 coordination
around vanadium(IV). The catalytic activity of 1 was studied in the oxidative bromination of 2-nitro-
phenol as a model substrate, and different reaction parameters were investigated. The oxidative bro-
mination of some organic compounds in the presence of 1 in optimal conditions showed that it was an
effective and selective catalyst in those optimal conditions. Thermogravimetric analysis of 1 showed
that it decomposed in two stages. 1 was thermally decomposed in air at 660 °C, and the XRD pattern
of the obtained solid showed the formation of the V2O5 nanoparticles with average size of 34 nm .
Keywords: Oxidovanadium(IV); Schiff base; Single crystal; Oxidative bromination; V2O5 nanoparticle
1. Introduction
Schiff base transition metal complexes have been extensively studied because of their poten-
tial applications [1–4]. Interest in the coordination chemistry of vanadium complexes has
grown enormously due to its structural features [5–7], catalytic applications [8–10], and bio-
logical roles in a variety of biochemical processes such as haloperoxidation [11–13], nitrogen
fixation [14], phosphorylation [15], glycogen metabolism [16–18], and insulin mimicking
[19–22] as well as some biological outcomes such as antimicrobial [23, 24], spermicidal
[25], antileukemia [26], and antitumor activities [27]. Halogenated organic compounds are
essential substrates because incorporation of halogen on an organic substrate gives suitable
properties for different uses such as synthetic intermediates and starting compounds, designer
molecules for material science, industrial chemicals, and bioactive compounds [27–29].
Vanadium-dependent haloperoxidases are an important group of halogenating enzymes, and
their action was investigated in enzymatic reactions and in biomimetic studies [11–13, 30,
31]. In these enzymes, the vanadium(V) center was surrounded by histidine residue contain-
ing O, N donors [32]. Thus, the design and synthesis of vanadyl Schiff base complexes con-
taining O, N donors can be useful as a model compound. In this research, we describe the
synthesis, characterization, crystal structure determination, catalytic activity in oxidative bro-
mination, and thermal study of a new oxidovanadium Schiff base complex 1, derived from
3-methoxy-2-hydroxybenzaldehyde and 2-bromoethyl ammonium hydrobromide.
2. Experimental
2.1. Materials and physical measurements
All reagents and solvents for synthesis and analysis were commercially available and pur-
chased from Merck and used as received. FT-IR spectra were recorded from 400 to
4000 cm−1 on a Perkin Elmer FT-IR spectrophotometer using KBr pellets. Elemental analy-
ses were performed on a Heraeus CHN–O-rapid analyzer, and results agreed with calculated
values. 1H nuclear magnetic resonance (NMR) spectrum was recorded on a BRUKER
DRX-500 AVANCE spectrometer at 500 MHz for HL. All gas liquid chromatography
(GLC) yields based on the starting materials were obtained by using Teif Gostar Fraz Co.
instrument with silicon-DC 200 column and FID detector. All measurements were taken at
20 psi, 20 psi, and 15 psi for N2, air, and H2, respectively, while the temperature of the col-
umn was kept at 150 °C. Thermogravimetry (TG) and differential thermoanalysis (DTA)
were carried out on a Mettler Toldeo. The measurements were performed in air. The heating
rate was kept at 10 °C min−1. XRD pattern of the nanoparticles was recorded on a Bruker
AXS diffractometer D8 ADVANCE with Cu-Kα radiation with nickel beta filter in the
range 2θ = 10–80°.

Oxidovanadium Schiff base
3
2.2. Synthesis of 2-{(E)-[2- (bromoethyl)imino]methyl}-6-methoxy phenol (HL)
3-Methoxy-2-hydroxy benzaldehyde (1.52 g, 10 mM), 2-bromoethyl ammonium hydrobro-
mide (2.04 g, 10 mM), and NaOH (0.4 g, 10 mM) were added to 150 mL of methanol, and
the mixture was stirred for 4 h. After evaporating the solvent, the yellow precipitate was
collected and washed slightly with cooled water and then with 1 : 1 mixture of n-hexane
and dichloromethane. Yield: 2.2 g (85%). M.p.: 60 °C. Anal. Calcd for C10H12BrNO2: C,
47.28; H, 4.63; and N, 5.27%. Found: C, 46.53; H, 4.65; and N, 5.42%. IR (KBr pellet,
cm−1): 3350–3450 (b, O–H, phenolic), 2782–3000 (w, C–H aliphatic, and aromatic), 1632
1
(s, C=N), 1436, 1468, 1502, 1581 (m, C=C), 1250 (m, C–O), and 736 (m, C–Br). H NMR
(CDCl3, δ(ppm)): 13.39 (s, 1H, –O–H), 8.35 (s, 1H, H–C=N–), 6.95 (d, 1H, phenyl–H:),
6.91 (d, 1H, phenyl–H:), 6.82 (s, 1H, phenyl–H:), 4.01 (t, 2H,–CH2Br), 3.89 (3H, –OMe),
and 3.64 (t, 2H, –N–CH2–).
2.3. Synthesis of VOL2 (1)
A mixture of HL (1.3 g, 5 mM) and VO(acac)2 (0.66 g, 2.5 mM) was dissolved in methanol
(70 mL) and refluxed for 2 h. After evaporating the solvent, the remaining reaction mixture
was recrystallized in a solvent mixture of MeOH/CHCl3 (1/1, v/v). The greenish crystals that
formed were filtered off, washed with n-hexane and dried in an oven. Yield: 1.2 g (82%).
M.p.: 194.2 °C. Anal. Calcd for C20H22Br2N2O5 V: C, 40.13; H, 3.74; and N, 4.83. Found:
C, 41.32; H, 3.78; and N, 4.82%. IR (KBr pellet, cm−1): 2802–2984 and 3008–3080 (w, C–H
aliphatic and aromatic), 1612 (s, C=N), 1444–1550 (m, C=C), 740 (m, C–Br), and 982
(s, V=O).
Table 1. Crystallographic data and structure refine-
ment for 1.
Empirical formula
Formula weight
Temperature
C20H22Br2N2O5V1
581.2
120
Crystal system
Space group
Monoclinic
P21/c
Unit cell dimensions
a = 11.2742(7) Å
b = 12.1729(7) Å
c = 23.1756(14) Å
β = 136.161(9)°
2203.0(4) Å3
4
Volume
Z
Absorption coefficient
Measured reflections
8.31 mm−1
12,060
Independent reflections
3882
Reflections with I > 3σ(I)
3338
Tmin
0.152
Tmax
0.432
0.025
0.030
R[F2 > 2σ(F2)]
wR(F2)
S
1.37
Δρmax
Δρmin
0.25 e Å−3
−0.48 e Å−3

4
G. Grivani et al.
2.4. X-ray structure determination
Suitable single crystal of dimensions 0.40 mm × 0.23 mm × 0.14 mm of 1 was chosen for
X-ray diffraction study. Crystallographic measurements were done at 150 K with a four-cir-
cle CCD diffractometer Gemini of Oxford Diffraction, Ltd, with mirrors-collimated Cu-Kα
radiation (λ = 1.54184 Å), using the area detector Atlas. The crystal structure was solved by
direct methods with the program SIR2002 [33] and refined with the Jana2006 program
package [34] by full-matrix least squares on F2. The molecular structure plots were pre-
pared by ORTEP III [35]. Hydrogens were mostly discernible in difference Fourier maps
and could be refined to reasonable geometry. According to common practice, they were
nevertheless kept in ideal positions during the refinement except the ones bonded to nitro-
gen. The isotropic atomic displacement parameters of all hydrogens were evaluated as
1.2Ueq of the parent atom. Crystallographic data, details of the data collection and structure
solution and refinements are listed in table 1. The synthesized vanadyl complex structure
was established on the basis of its spectral analysis: IR, elemental analysis data, and melting
point determination.
2.5. General procedure of the oxidative bromination reaction
In a 10-mL round-bottom flask equipped with a magnetic stirring bar, 1 mM of the 2-nitro
phenol was reacted with different amounts of the oxidant, acid, bromide source, and the vana-
dyl Schiff base complex in 4 mL of solvent. The content was stirred at room temperature.
The progress of the reaction was monitored by GLC.
3. Results and discussion
3.1. Synthesis and characterization
HL was prepared by the condensation of 3-methoxy-2-hydroxy benzaldehyde and 2-bromo-
ethyl ammonium hydrobromide in methanol, and then, the product was isolated by the
evaporation of solvent. The corresponding VO2+ complex (1) was synthesized by the reac-
tion of VO(acac)2 and the related Schiff base ligand (HL) in methanol (scheme 1). The
ligand and complex are quite air stable as solids and also in solution. They are characterized
1
by FT-IR and H NMR spectra and CHN and X-ray analysis. The CHN analysis of HL and
1
1 confirms the chemical composition. The H NMR spectrum of HL is given in figure 1. In
agreement with the structure of the ligand, eight signals with integration ratios of
1 : 1 : 1 : 1 : 1 : 2 : 3 : 2 were seen in this spectrum related to the protons of a : b : c : d :
e : f : h : g (figure 1). The two distinct triplets at 4.00 and 3.63 ppm corresponded to the
protons (f and g) of N–CH2– and –CH2–Br, respectively. The three peaks at 6.70–7.00 ppm
were attributed to the aromatic protons b, c, and d. The signal of the iminic proton (e) was
at 8.35 ppm. The methoxy protons (h) appear as singlets at 3.9 ppm. The chemical shift of
phenolic proton (H) was strongly shifted downfield at 13.39 ppm. This high chemical shift
can be related to the intramolecular hydrogen bonding between nitrogen of imine and
hydrogen of phenol [36]. In the FT-IR spectrum of HL, a sharp band appeared at
1632 cm−1, due to v(C=N) (azomethine). This band shifted to lower wave number at
1612 cm−1 in the FT-IR spectrum of 1, indicating binding of azomethine nitrogen to vana-
dium(IV). Complex 1 exhibits a sharp band at 982 cm−1 due to vV=O that clearly identifies

Oxidovanadium Schiff base
5
Br
O
Br
N
CH3OH/ NaOH
BrH.H2N
Reflux/ 4 h
OH
OH
OCH3
OCH3
HL
Reflux/ 2 h
VO(acac)2/CH3OH
Br
OCH3
N
O
O
V
O
N
OCH3
Br
1
Scheme 1. The preparation procedures of HL and its vanadyl complex (1).
the vanadium(IV) complex. It has been reported that oxovanadium complexes with coordi-
nation number of five (monomeric five-coordinate V=O complexes) have vV=O about
980 cm−1 and with coordination number of six (with polymeric vanadium–oxygen as
⋯V=O⋯V=O⋯ units) have the vV=O lower than 980 cm−1, and this provides an index for
discriminating the coordination number of oxovanadium complexes [37–39]. Thus, the
sharp band at 982 cm−1 was attributed to vV=O of five-coordinate 1. In comparison of the
V=O bond length in 1 with those of polymeric forms of vanadyl complexes, it is clear that
the length of this bond in 1 is shorter than⋯V=O⋯V=O⋯complexes and lies in the range
of the bond lengths of five-coordinate V=O complexes [37–40]. These data are consistent
with the crystal structure of 1.
3.2. Crystal structure of 1
An ORTEP view of 1 with the atom-numbering scheme is given in figure 2. table 2 lists
selected bond lengths and angles. In 1, the Schiff base ligand is anionic and a bidentate N, O
chelate. Vanadium(IV) is coordinated by two oxygens and two nitrogens of two independent
ligands in the equatorial plane and the terminal O occupies the axial position [8, 41–44]. The
square-pyramidal geometry around V(IV) in 1 is distorted because of the different bond dis-
tances and angles. The greatest angular distortion from an ideal square-pyramidal geometry

6
G. Grivani et al.
Figure 1. The 1H NMR spectrum of HL.
(109.5°) occurs in the angles O1–V1–O12b [112.63(12)°] and O12b–V1–N4b [85.87(10)°].
The V–N and V–O distances (table 1) are similar to those found in other V(IV) complexes
with Schiff base ligands [8, 41–44].
The geometries of the hydrogen bonds in 1 are listed in table 3. As shown in figure 2,
there are several intra- and intermolecular hydrogen bonds in 1, effective in the stabilization
of the crystal structure.
3.3. Catalytic activity
The oxidative bromination of 2-nitrophenol using hydrogen peroxide, which did not pro-
ceed in the absence of catalyst at room temperature, was used as a model reaction. To find
the optimum reaction conditions, the influence of different factors that may affect the con-
version and selectivity of the reaction was investigated. A systematic examination of the
oxidative bromination of 2-nitrophenol in various solvents such as MeOH, MeCN, and
CHCl3, and mixture of solvents of H2O/MeOH, H2O/MeCN, and H2O/CHCl3 was carried
out in the presence of catalytic amount of 1. In coordinating solvent mixtures such as H2O/
MeOH, H2O/MeCN, and H2O/CHCl3, oxidative bromination of 2-nitrophenol proceeded
efficiently. Considering the yield and reaction rate, H2O/MeOH was the best solvent mix-
ture (figure 3). The typical reaction medium for bromo peroxidases is ocean water [30].
Water, however, is a nucleophile and therefore able to intercept electrophiles, changing

Oxidovanadium Schiff base
7
Figure 2. (a) An ORTEP view of 1; atomic displacement parameters are shown at the 50% probability level. (b)
Diagram packing of 1 with the atom-numbering scheme. Dashed lines represent hydrogen bonds.

8
G. Grivani et al.
Table 2. Selected bond distances and angles in 1.
V1–O12b
V1–N4b
V1–O1
1.9042(1)
2.101(3)
1.598(2)
V1–O12a
V1–N4a
1.910(2)
2.102(3)
O1–V1–N4
O1–V1–N4b
N4a–V1–O12a
N4a–V1–O12b
O12a–V1–O12b
102.00(13)
100.64(11)
85.95(11)
85.51(9)
O1–V1–O12a
O1–V1–O12b
N4a–V1–N4b
O12a–V1–N4b
N4b–V1–O12b
111.02(10)
112.63(12)
157.35(11)
85.93(11)
85.87(10)
136.35(10)
Table 3. Some intra- and intermolecular hydrogen bonds in 1.
D–H⋯A
D–H
H⋯A
D⋯A
D–H⋯A
C5–H1c5a⋯O1
C3–H1c3a⋯O1
C3a–H2c3a⋯O13b
0.960
0.959
0.960
2.458
2.530
2.874
3.207
3.364
3.549
131.857
145.339
128.233
selectivity. In order to achieve a good catalytic system for H2O2, the formation of the perox-
ovanadium(IV) and the interaction with hypoacid (HOBr) or BrÀ3 , lipophilicity of the sol-
vent should be improved [30]. The effect of bromide salt (bromide source), inorganic acid,
and oxidant was also investigated. Based on the yield and reaction rate, among KBr, NaBr,
and NH4Br, KBr was the best bromide source and among the H2SO4, HNO3, and H3PO4,
H2SO4 was the best inorganic acid. H2O2 was the best oxidant among H2O2, TBHP, and
KHSO5 oxidants (table 4). In the presence of homogeneous and enzyme catalysts, liberation
Figure 3. The solvent effect in the oxidative bromination of 2-nitrophenol by 1 in the presence of H2O2 as oxidant
and KBr as bromide source. Reaction conditions at room temperature: substrate (1 mM), catalyst (0.0073 mM),
H2O2 (2 mM), H2SO4 (2 mM), KBr (4 mM), and solvent (4 mL).

Oxidovanadium Schiff base
9
of Br2 from KBr by H2O2 is well known [30, 45, 46]. Thus, it was expected that the same
situation may prevail in the present case and could be explained by the proposed mecha-
nism where generation of Br2 is much easier. For the homogeneous vanadium bromoperoxi-
dase mimics, appreciable catalytic activity is observed in strong acid [45]. Examination of
various molar ratios of oxidant/substrate and salt/substrate in the catalytic oxidative bromin-
ation of 2-nitrophenol showed that full oxidation of 2-nitrophenol was obtained in 2 : 1
ratio of oxidant/substrate and 4 : 1 ratio of salt/substrate in H2O/MeOH in the presence of
H2SO4 and a catalytic amount of 1 (figures 4 and 5). In order to establish the general appli-
cability of the method, various substrates were subjected to the oxidation protocol under the
influence of 1 (table 5). In the conversion of 2-nitrophenol, 2-chlorophenol, phenol,
2-hydroxy benzaldehyde, 2-hydroxy-3-methoxy-benzaldehyde, and 2-hydroxy acetophe-
none, 1 selectively and efficiently converted them to mono-brominated products with full
conversion in optimal conditions, while in the case of the benzaldehyde and 2-chloro
Table 4. The effects of oxidant, acid, and bromide salt in the oxidative bromination of 2-nitrophenol by
1a,b,c at room temperature.
Run
Saltc
Acid
Oxidantd
Time (min)
% Yields
1e
2
3
4
6
7
8
9
KBr
KBr
KBr
KBr
KBr
KBr
NaBr
NH4Br
H2SO4 2 mM
HNO3 4 mM
H3PO4 2 mM
H2SO4 2 mM
H2SO4 2 mM
H2SO4 2 mM
H2SO4 2 mM
H2SO4 2 mM
H2O2
H2O2
H2O2
H2O2
TBHP
KHSO4
H2O2
H2O2
100
80
100
35
120
100
60
No reaction
100
45
100
27
No reaction
100
40
60
a2-Nitrophenol as substrate.
bSolvent (4 mL with 1 : 3 ratio of H2O/MeOH).
cCatalyst (0.0073 mM).
d2 mM.
eBlank experiment.
Figure 4. The effect of oxidant amount in the oxidative bromination of 2-nitrophenol by 1 in the presence of
H2SO4 as an acid source and KBr as a bromide source. Reaction conditions at room temperature: substrate
(1 mM), catalyst (0.0073 mM), H2O2 (1, 2, and 3 mM), H2SO4 (2 mM), KBr (4 mM), and solvent (4 mL).

10
G. Grivani et al.
Figure 5. The effect of salt amount in the oxidative bromination of 2-nitrophenol by 1 in the presence of H2SO4
as an acid source and H2O2 as an oxidant. Reaction conditions at room temperature: substrate (1 mM), catalyst
(0.0073 mM), H2O2 (2 mM), H2SO4 (2 mM), KBr (2, 3, and 4 mM), and solvent (4 mL).
Table 5. The oxidative bromination of organic substrates by catalytic amounts of 1 in optimal conditionsa at room
temperature.
Time
(min)
Selectivity
(%)
%
Substrate
Product
Yields TOFb
2-Nitrophenol
2-Chlorophenol
Phenol
Salicylaldehyde
Benzaldehyde
2-Chloro benzaldehyde
2-Hydroxy-3-methoxy-
benzaldehyde
35
80
80
70
90
65
15
4-Bromo-2-nitrophenol
4-Bromo-2-chlorophenol
4-Bromophenol
5-Bromo-2-hydroxy benzaldehyde
4-Bromobenzaldehyde
4-Bromo-2-chloro benzaldehyde
4-Bromo-2-hydroxy-3-methoxy
benzaldehyde
100
100
100
100
100
100
100
100
100
100
100
50
236
103
103
118
50
41
100
52
547
2-Hydroxy acetophenone
25
4-Bromo-2-hydroxy acetophenone
100
100
328
aReaction conditions: substrate(1 mM), catalyst (0.0073 mM), H2O2 (2 mM), H2SO4 (2 mM), and solvent (1 : 3 ratio of H2O/
MeOH, 4 mL).
bTOF = M of substrate/M of catalyst × time (h).
benzaldehyde, the catalyst showed lower activity. Comparison of the selectivity and activity
(TOF = M of substrate/M of catalyst × time (h)) of recent V(V) and V(IV) complexes
[47–51] or other metal mediated catalysts [52, 53] with the selectivity and TOF of the titled
vanadyl complex (1) shows high selectivity and activity of 1 in oxidative bromination.
Almost all of the organic compounds in table 5 brominated effectively and selectively to
mono-brominated compounds only.
3.4. Thermal analysis and XRD of 1
Thermal gravimetric analyses were carried out to examine the thermal stability of 1 and the
nature of the produced vanadium oxide. The TG/DTA/DTG profiles of 1 in air with a
heating rate of 10 °C min−1 are shown in figure 6. Based on these profiles, 1 shows two
stages of thermal decomposition. The first stage occurs at 422.95–734.5 K with a weight

Oxidovanadium Schiff base
11
Figure 6. TG/DTA/DTG profiles of 1.
loss of 35.88%, due to loss of two methoxy and bromines from the Schiff base ligand: 2
(OCH3), Br (Calcd 38.19%). The second stage from 743.5–923 K is observed with a mass
loss of 50.05% due to elimination of organic residue from the remaining Schiff base ligand
1600
1400
1200
1000
800
600
400
200
0
10
20
30
40
50
60
70
80
90
2θ(degree)
Figure 7. The XRD pattern of the residual powder obtained from thermal decomposition of 1.

12
G. Grivani et al.
Table 6. Characteristics of the XRD pattern obtained from thermal decomposition of 1.
Pos. [°2Th.]
Height [cts]
Rel. Int. [%]
h
l
k
15.4946
20.3774
21.7974
26.2657
31.0929
32.5033
33.4262
34.3972
41.4282
42.1268
45.595
343.37
1332.03
408.56
686.72
748.15
300.38
92.64
25.78
100
2
0
1
1
3
0
1
3
0
1
1
6
0
1
0
6
0
4
3
7
6
7
6
3
0
0
0
1
0
1
1
1
0
0
1
0
1
1
2
0
2
1
2
1
0
1
2
1
0
1
1
0
1
1
1
0
2
2
1
0
2
2
0
1
1
2
1
0
2
1
0
3
30.67
51.55
56.17
22.55
6.96
18.77
11.17
7.74
13.1
15.8
14.12
9.1
250.05
148.8
103.09
174.56
210.43
188.15
121.26
213.1
111.13
88.5
84.82
96.03
141.42
44.52
55.28
73.6
47.4554
47.9292
48.912
51.3507
52.1344
55.7545
59.1332
61.2047
62.2711
64.6822
66.212
16
8.34
6.64
6.37
7.21
10.62
3.34
4.15
5.53
5.59
72.6231
74.5965
74.47
(Calcd 48.21%), resulting in the formation of V2O5. We also examined a simple route for
the preparation of the V2O5 nanoparticles. 1 was heated in an oven at 933 K. After cooling
to room temperature, the obtained powder was analyzed by X-ray powder diffraction. The
XRD of the obtained powder from this thermal decomposition and the obtained results
(positions; intensities; and h, k, and l) from this pattern are given in figure 7 and table 6.
Based on the resulting XRD pattern, the average crystallite size calculated using Scherrer’s
formula was 34 nm.
4. Conclusion
We described the synthesis and characterization of a new monomeric oxidovanadium Schiff
base complex containing bidentate O, N Schiff base ligand. The complex shows distorted
square-pyramidal N2O3 coordination sphere around the vanadium(IV) with two N, O
coordinations from two Schiff base ligands and one oxido ion in an apical position. The
catalytic activity of 1 was investigated in oxidative bromination, and different reaction
parameters were optimized in the oxidative bromination of 2-nitrophenol. The results
showed that the vanadyl complex was active and selective in the oxidative bromination of
substituted phenols and produced mono-bromo products. In addition, thermal decomposi-
tion of this vanadyl Schiff base complex showed that the complex was stable to 180 °C and
decomposed at two stages and converted to V2O5 at the end of decomposition.
Supplementary material
Crystallographic data (excluding structure factors) for the structure reported in this article
has been deposited with the Cambridge Crystallographic Center, CCDC No. 965176.

Oxidovanadium Schiff base
13
Copies of the data can be obtained free of charge on application to The Director, CCDC, 12
Union Road, Cambridge CB2 1EZ, UK; Fax: +44 1223 336 033; Email: deposit@ccdc.ca-
m.ac.uk or http://www.ccdc.cam.ac.uk.
Acknowledgments
G. Grivani, V. Tahmasebi, and A.D. Khalaji are grateful to the Damghan University and
Golestan University for financial support.
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