Synthesis, crystal structure, and insulin-like activity of [N′-(2-hydroxy-3-methoxybenzylidene)-2-methoxybenzohydrazonato](1,10-phenanthroline)oxovanadium(IV) methanol solvate

Article abstract of DOI:10.1080/24701556.2017.1357613

The aroylhydrazone Schiff base ligand N′-(2-hydroxy-3-methoxybenzylidene)-2-methoxybenzohydrazide (H₂L) reacts with VO(acac)₂ and 1,10-phenanthroline (Phen) in methanol to give the complex [N′-(2-hydroxy-3-methoxybenzylidene)-2-methoxybenzohydrazonato](1,10-phenanthroline)oxovanadium(IV) methanol solvate, [V^IVOL(Phen)]·CH₃OH. The structure of the complex was characterized by elemental analyses and IR spectroscopic method in the solid state. Single-crystal X-ray analysis was also performed. The complex crystallized in the triclinic space group P-1, with unit cell dimensions a = 9.220(3) ?, b = 9.382(3) ?, c = 16.593(5) ?, α = 73.900(5)°, β = 78.618(6)°, γ = 84.959(6)°, V = 1351.1(7) ?³, Z = 2, R₁ = 0.0837, and wR₂ = 0.0751. The vanadium(V) atom in the complex is six-coordinated with an octahedral geometry. Thermal stability as well as the insulin-like activity of the complex have been determined.

Full text of DOI:10.1080/24701556.2017.1357613

Inorganic and Nano-Metal Chemistry
ISSN: 2470-1556 (Print) 2470-1564 (Online) Journal homepage: http://www.tandfonline.com/loi/lsrt21
Synthesis, Crystal Structure,
and Insulin-like Activity of [N'-(2-
Hydroxy-3-methoxybenzylidene)-2-
methoxybenzohydrazonato](1,10-
phenanthroline)oxovanadium(IV) Methanol
Solvate
Xu-Feng Meng, Qi-Feng Liu, Ji-Lai Liu, Ming-Hui Sun & Jing-Jun Ma
To cite this article: Xu-Feng Meng, Qi-Feng Liu, Ji-Lai Liu, Ming-Hui Sun & Jing-Jun Ma (2017):
Synthesis, Crystal Structure, and Insulin-like Activity of [N'-(2-Hydroxy-3-methoxybenzylidene)-2-
methoxybenzohydrazonato](1,10-phenanthroline)oxovanadium(IV) Methanol Solvate, Inorganic and
Nano-Metal Chemistry, DOI: 10.1080/24701556.2017.1357613
To link to this article: http://dx.doi.org/10.1080/24701556.2017.1357613
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Date: 07 August 2017, At: 08:54

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Synthesis, Crystal Structure, and Insulin-like Activity of
[N'-(2-Hydroxy-3-methoxybenzylidene)-2-methoxybenzohydrazonato](1,10-phenanthroline)oxo
vanadium(IV) Methanol Solvate
Xu-Feng Menga, Qi-Feng Liua, Ji-Lai Liub, Ming-Hui Sunc, Jing-Jun Maa,*
aCollege of Sciences, Agricultural University of Hebei, Baoding Hebei 071001, P. R. China
bHebei Changshan Biochemical Pharmaceutical Co., Ltd., Shijiazhuang Hebei 050800, P. R.
China
cDepartment of Economics and Management, Hebei North University, Zhangjiakou Hebei
075000, P. R. China
*e-mail: majingjun71@126.com
Abstract
The aroylhydrazone Schiff base ligand
N'-(2-hydroxy-3-methoxybenzylidene)-2-methoxybenzohydrazide (H2L) reacts with VO(acac)2
and 1,10-phenanthroline (Phen) in methanol gave the complex
[N'-(2-hydroxy-3-methoxybenzylidene)-2-methoxybenzohydrazonato](1,10-phenanthroline)oxov
anadium(IV) methanol solvate, [VIVOL(Phen)]·CH3OH. The structure of the complex was
characterized by elemental analyses and IR spectroscopic method in the solid state. Single crystal
X-ray analysis was also performed. The complex crystallized in triclinic space group P-1, with
unit cell dimensions a = 9.220(3) Å, b = 9.382(3) Å, c = 16.593(5) Å, α = 73.900(5)°, β =
78.618(6)°, γ = 84.959(6)°, V = 1351.1(7) Å3, Z = 2, R1 = 0.0837, wR2 = 0.0751. The V atom in the
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complex is six-coordinated in an octahedral geometry. Thermal stability of the complex was
determined. The insulin-like activity of the complex has been determined.
Keywords
Vanadium complex, crystal structure, aroylhydrazone, thermal property, insulin-like activity
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Introduction
The presence of vanadium(IV) and vanadium(V) compounds in many vanadium-dependent
enzymes, for instance, nitrogenases and haloperoxidases,[1-3] as well as insulin mimicking,[4,5] have
stimulated the search for structural and functional models based on vanadium complexes.
Moreover, oxovanadium complexes have been attracted tremendous attention for their versatile
catalytic properties in organic synthesis.[6-8] In recent years, the remarkable biological activity of
aroylhydrazones and the dependence of their mode of chelation with transition metal ions in living
systems have been of significant interest.[9-14] 1,10-Phenanthroline (Phen) is a well-known
bidentate ligand, which has been usually used as co-ligands in the preparation of metal
complexes.[15] Recently, we have reported some aroylhydrazone compounds.[16,17] As a further
study on the coordination of aroylhydrazone to vanadium ions, in this paper, a new oxovanadium
complex,
[N'-(2-hydroxy-3-methoxybenzylidene)-2-methoxybenzohydrazonato](1,10-phenanthroline)oxov
anadium(IV) methanol solvate, [VIVOL(Phen)]·CH3OH, was synthesized and characterized.
Experimental
Materials and Methods
3-Methoxysalicylaldehyde, 2-methoxybenzohydrazide, 1,10-phenanthroline and vanadium(IV)
oxide acetylacetonate ([VO(acac)2]) were purchased from Merck and Fluka, and used as received.
The aroylhydrazone Schiff base ligand
N'-(2-hydroxy-3-methoxybenzylidene)-2-methoxybenzohydrazide (H2L) was prepared in a 93%
yield by condensation reactions of 3-methoxysalicylaldehyde with 2-methoxybenzohydrazide in
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methanolic media, according to the literature method.[16,17] All other chemicals and solvents used
in this work were of analytical grade available commercially and were used without further
purification. Elemental analyses (carbon, hydrogen and nitrogen) of the compounds were obtained
from a Carlo ERBA Model EA 1108 analyzer. Infrared spectra were collected by using KBr pellets
on a Jasco-5300 FT-IR spectrophotometer. Solution electrical conductivity was measured with a
DDS-11A conductivity meter. Thermal analysis of the complex was carried out by heating at a rate
of 10°C per minute on a Perkin Elmer TGA-4000 thermo balance.
Synthesis of the Complex
[VO(acac)2] (0.01 mmol, 2.65 g) dissolved in methanol (30 mL) was added dropwise to a stirred
methanolic solution (30 mL) of H2L (0.01 mol, 3.00 g) and 1,10-phenanthroline (0.05 mmol, 0.09
g). The mixture was gently refluxed for 2 h, then most of the solvent was evaporated by
distillation. After cooling, the resulting brown solid was filtered off, washed with cold absolute
methanol, and dried in a vacuum containing anhydrous CaCl2. Yield: 0.20 g (69%). IR data (cm--1,
KBr): 3449 (m), 1616 (s), 1525 (m), 1440 (m), 1375 (m), 1303 (w), 1244 (m), 1107 (m), 1028 (w),
963 (s), 846 (w), 735 (m), 676 (w), 598 (w), 493 (w), 435 (w). Dark brown block-like single
crystals of the complex, suitable for single crystal X-ray diffraction, were obtained by slow
evaporation of a methanol solution containing the complex. Anal. Calcd. for C29H26N4O6V (%): C,
60.32; H, 4.54; N, 9.70. Found: C, 60.50; H, 4.67; N, 9.59.
X-Ray Crystallography
A suitable X-ray quality crystal of the complex was pick up under a microscope and investigated in
a diffraction experiment at 298(2) K on a Bruker Apex II diffractometer with monochromated Mo
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Kα radiation (λ = 0.71073 Å) obtained from a graded multilayer X-ray optics. The structure was
solved by direct methods with SHELXS-97,[18] and refined with full-matrix least-squares
techniques on F2 with SHELXL-97.[18] The C-bonded hydrogen atoms were calculated in an
idealized geometry, riding on their parent atoms, with distances restrained to 0.93--0.96 Å. The
crystal data and refinement parameters are listed in Table 1.
Cell Culture and Viable Cell Counts
C2C12 mouse skeletal muscle cells were cultured in Dulbecco modified Eagle’s medium with 4
mmol·L1 L-glutamine. C2C12 cells were sub-cultured in log phase to 70% confluence and seeded
at a density of 5000 cells per well into 96-well culture plates. After three days culture myotube
formation was induced by replacing the fetal bovine serum in the medium with 10% horse serum.
All experiments were done in 5 days when more than 75% of the cells were differentiated
morphologically. The cells were suspended in a trypan blue (0.1% w/w) phosphate buffered saline
solution and the ratio of stained to nonstained cells was determined after 5 min of incubation time.
Viable cell counts were performed using a hemocytometer.
Glucose Uptake Determination
Cells were incubated in glucose and serum-free media after 3 hours prior to glucose uptake. On the
5th day, the medium was removed and replaced with 50 mL modified Dulbecco modified Eagle’s
medium without phenol red, supplemented with 8 mmol·L1 glucose and 0.1% bovine serum
albumin containing either the complex at concentration of 0.10 g·L1 or the positive controls,
insulin, at 1 mmol·L1 were added to the 96-well plate. The plate was then incubated for 2 h at
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37°C and 5% CO2. After incubation, 4 mL media was removed from each well and transferred to a
new 96-well plate to which 196 mL deionized water was added in each well. A total of 50 mL of
this diluted medium was transferred to a new 96-well plate and 50 mL of the prepared glucose
assay reagent was added per well and incubated for 30 min at 37°C. Absorbance was taken at 570
nm on a 96-well plate reader. The glucose concentration per well was calculated from a standard
curve. Glucose utilization was determined by subtracting the glucose concentration left in the
medium of the relevant wells following incubation to media not exposed to cells during
incubation.
Results and Discussion
Synthesis and Characterization
The reaction of VO(acac)2 with the tridentate aroylhydrazone Schiff base ligand
N'-(2-hydroxy-3-methoxybenzylidene)-2-methoxybenzohydrazide and 1,10-phenanthroline in
methanol afforded the neutral oxovanadium(IV) complex (Scheme 1). Elemental analyses of the
complex are consistent with the general molecular formula proposed by single crystal X-ray
determination. The complex is soluble in common organic solvents such as dimethylsulphoxide,
dimethylformamide, methanol, and ethanol. In absolute methanolic solution, it is electrically
non-conducting.
IR Spectra
The infrared spectra of the free aroylhydrazone Schiff base ligand and the complex gave
information about the coordination. The free ligand displays a broad band centered at 3415 cm1
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and a weak and sharp band at 3223 cm1. These bands are possibly due to the O--H and N--H
stretches. However, the sharp band is absence in the spectrum of the complex. The absence of the
ν(C = O) band, presents in H2L at 1651 cm1, indicates the enolization of the amide functionality
upon coordination to the V atom. Strong band observed at 1616 cm1 for the complex can be
attributed to the stretching vibrations of the azomethine group, νC = N.
[19] The spectrum of the
complex displays typical and intense band at 963 cm1 which can be assigned to the stretches of the
V = O bond.[20]
Description of the Crystal Structure of the Complex
The molecular structure and atom numbering scheme for the complex is depicted in Figure 1.
Selected bond lengths and angles are given in Table 2. The complex contains a neutral
mononuclear oxovanadium complex and a methanol molecule of crystallization. The coordination
geometry around the vanadium atom can be described as distorted octahedral with the tridentate
aroylhydrazone ligand coordinated in a meridional fashion, forming five- and six-membered
chelate rings with bite angles of 76.48(19)° (N(1)--V(1)--O(2)) and 88.2(2)° (N(1)--V(1)--O(1)),
typical for this type of ligand system.[21,22] The aroylhydrazone Schiff base ligand coordinates in its
dianionic enolate form, which is consistent with the observed C(8)--O(2) and C(8)--N(2) bond
lengths of 1.278(6) and 1.311(7) Å. The three donor atoms of the aroylhydrazone ligands and N4
atom of 1,10-phenanthroline ligand define the equatorial plane of the octahedral coordination. The
two axial positions of the octahedral coordination are occupied by the N(3) atom of
1,10-phenanthroline ligand and one oxo group. The N(3) atom in the complex coordinates to the V
atom at rather elongated distance of 2.354(5) Å, due to the trans influence of the oxo group. This is
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accompanied by a significant displacement of the V atom from the equatorial plane towards the
oxo group by 0.352(2) Å.
In the crystal structure of the complex, methanol molecules are linked to the vanadium complex
molecules through intermolecular O(6)--H(6)···N(2) hydrogen bond [O(6)--H(6) = 0.82 Å,
H(6)···N(2)ii = 2.30(2) Å, O(6)···N(2)ii = 2.906(8) Å, O(6)--H(6)···N(2)ii = 131(3)°; symmetry
code for ii: x, y, 1 + z] (Figure 2).
Thermal Property
The thermogravimetric analysis of the complexes was carried out in the temperature range
50--1000°C at a heating rate of 10°C min1. The TG and DTA curves of the complex are given
following degradation scheme (Figure 3). The complex is stable up to 83°C. Above this
temperature, the TG curve show three steps of weigh losses. The first step of decomposition in the
temperature range 83--104°C involved the removal of the lattice methanol molecule. The second
step of decomposition in the temperature range 231--494°C involved the removal of the
1,10-phenanthroline ligand. With further elevation in temperature, a rapid weigh loss in the
temperature range 494--538°C was observed. The decomposition of the final stage weight loss
may be ascribed to the dissociation of the aroylhydrazone Schiff base ligand, and the formation of
the final product V2O5.
Insulin-Like Activty
The glucose uptake by C2C12 muscle cells following exposure to the vanadium complex was
studied. Insulin-like activity indicated that the complex can significantly stimulate cell glucose
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utilization with percentage in glucose utilization of 163. As a comparison, the percentage in
glucose utilization of insulin is 145. It is excited that the insulin-like activity of the complex is
more active than insulin.
Acknowledgments
The authors are grateful to the Natural Science Foundation of Hebei Key Laboratory of
Bioinorganic Chemistry and College of Sciences of Agricultural University of Hebei for financial
support.
Supplementary Material
CCDC 906161 contains the supplementary crystallographic data for the complex. These data can
be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the
Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44)
1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk.
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Table 1. Crystallographic data for the complex
Chemical formula
Formula weight
Crystal system
Space group
Unit cell dimensions
a (Å)
C29H26N4O6V
577.48
Triclinic
P-1
9.220(3)
9.382(3)
16.593(5)
73.900(5)
78.618(6)
84.959(6)
1351.1(7)
2
b (Å)
c (Å)
α (°)
β (°)
γ (°)
V (Å3)
Z
ρ (g cm3)
μ (mm1)
1.419
0.418
Tmin, Tmax
Reflections collected
Reflections unique
0.8955, 0.9100
9275
4487
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Reflections observed [I >
2σ(I)]
1904
Parameters
365
R1, wR2 [I > 2σ(I)]
R1, wR2 (all data)
Goodness-of-fit on F2
0.0751, 0.0837
0.1059, 0.2081
0.973
Largest difference in peak
and hole (e Å3)
0.308, --0.332
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Table 2. Selected bond lengths (Å) and angles (°) for the complex
V(1)--O(1)
1.953(4)
1.610(4)
2.354(5)
101.1(2)
155.44(18)
88.2(2)
V(1)--O(2)
1.999(4)
2.026(5)
2.133(5)
101.4(2)
105.0(2)
76.48(19)
97.38(18)
159.1(2)
79.87(19)
89.3(2)
V(1)--O(5)
V(1)--N(1)
V(1)--N(3)
V(1)--N(4)
O(5)--V(1)--O(1)
O(1)--V(1)--O(2)
O(1)--V(1)--N(1)
O(5)--V(1)--N(4)
O(2)--V(1)--N(4)
O(5)--V(1)--N(3)
O(2)--V(1)--N(3)
N(4)--V(1)--N(3)
O(5)--V(1)--O(2)
O(5)--V(1)--N(1)
O(2)--V(1)--N(1)
O(1)--V(1)--N(4)
N(1)--V(1)--N(4)
O(1)--V(1)--N(3)
N(1)--V(1)--N(3)
93.6(2)
90.96(18)
165.7(2)
80.82(19)
72.1(2)
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Figure 1. Structure of the complex with the atom labeling scheme. All non-hydrogen atoms are
represented at 30% probability thermal ellipsoids.
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Figure 2. Molecular packing diagram of the complex, viewed down the a axis. Hydrogen bonds
are drawn as dashed lines.
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120
100
80
100
80
60
40
20
60
40
20
0
-20
-40
-60
-80
200
400
600
800
1000
Temperature (oC)
Figure 3. DT-TGA curves of the complex.
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N
H
N
N
O
O
N
O
N
OMe
MeOH
O
OMe
V
VO(acac)2
OH
+
+
OMe
MeOH
N
N
OMe
N
Scheme 1. The synthesis of the complex.
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