Synthesis and crystal structures of dioxovanadium complexes with schiff bases

Article abstract of DOI:10.1080/15533174.2011.614311

Two new dioxovanadium complexes, [VO₂L¹]₂ (1) and [VO₂L²]₂ (2), where L¹ and L² are the deprotonated forms of 2-bromo-4-chloro-6- {[2-(2-hydroxyethylamino)ethylimino)methyl]phenol (HL¹) and 2- {[2-(2-hydroxyethylamino)ethylimino]methyl } phenol (HL²), respectively, have been synthesized and characterized by IR, UV-Vis spectra, and single-crystal X-ray diffraction. Both complexes are centrosymmetric dimeric dioxovanadium(V) compounds, with the V...V distances of 3.251(2)A and 3.127(2), respectively. The V atoms in the complexes are in octahedral coordination. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/15533174.2011.614311

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Synthesis and Crystal Structures of Dioxovanadium
Complexes With Schiff Bases
Shi-Yong Liu a & Yu-Ping Ma b
a College of Chemistry & Pharmacy, Taizhou University, Taizhou Zhejiang, P. R. China
b Department of Chemistry, Liaoning Normal University, Dalian, P. R. China
Accepted author version posted online: 14 Mar 2012.Published online: 01 May 2012.
To cite this article: Shi-Yong Liu & Yu-Ping Ma (2012): Synthesis and Crystal Structures of Dioxovanadium Complexes With
Schiff Bases, Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 42:4, 603-607
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Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 42:603–607, 2012
Copyright ꢀ Taylor & Francis Group, LLC
C
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2011.614311
Synthesis and Crystal Structures of Dioxovanadium
Complexes With Schiff Bases
Shi-Yong Liu1 and Yu-Ping Ma2
1College of Chemistry & Pharmacy, Taizhou University, Taizhou Zhejiang, P. R. China
2Department of Chemistry, Liaoning Normal University, Dalian, P. R. China
{[2-(2-hydroxyethylamino)ethylimino]methyl}phenol (HL2),
Two new dioxovanadium complexes, [VO2L1]2 (1) and [VO2L2]2
(2), where L1 and L2 are the deprotonated forms of 2-bromo-
4-chloro-6-{[2-(2-hydroxyethylamino)ethylimino)methyl]phenol
(HL1) and 2-{[2-(2-hydroxyethylamino)ethylimino]methyl}phenol
(HL2), respectively, have been synthesized and characterized
by IR, UV-Vis spectra, and single-crystal X-ray diffraction.
Both complexes are centrosymmetric dimeric dioxovanadium(V)
compounds, with the V· · ·V distances of 3.251(2) Å and 3.127(2)
Å, respectively. The V atoms in the complexes are in octahedral
coordination.
respectively, were synthesized and characterized.
EXPERIMENTAL
Materials and Measurements
All chemicals used were commercially available with AR
grade. Elemental analyses (CHN) were performed using a
Perkin-Elmer 240 elemental analyzer (Waltham, MA, USA. The
IR spectra were measured with a Nicolet FT-IR 170-SX spec-
trophotometer (Liaoning Normal University) using KBr pellets
in the 4000–400 cm−1 region. UV-Vis spectra were recorded on
a Perkin-Elmer Lambda 9 instrument. The EPR spectra of the
complexes were measured using a Bruker EMX Micro Premium
X spectrometer (Madison, WI, USA).
Keywords crystal structure, dioxovanadium complex, Schiff base,
synthesis
INTRODUCTION
Synthesis of the Schiff Bases HL1 and HL2
Much attention has been focused on the Schiff bases and their
complexes in the fields of coordination chemistry and biological
chemistry.[1–3] Vanadium compounds present innumerous phar-
macological applications as antitumorals, antimicrobials, and
insulin-mimics.[4–6] It has been demonstrated that the insulin ef-
fects of promoting glucose uptake and inhibiting lipolysis can be
duplicated by vanadium. It has been known that there exists trig-
onal bipyramidal vanadium within the phosphate-metabolizing
enzyme.[7,8] Mokry and coworkers reported that the steric bulk
of the substituent of the benzene ring can be used to modify the
coordination geometry and/or number of vanadium atoms by
preventing dimerization pathways.[9] To further explore the role
in the synthesis of such complexes,[10] in this study, two new oxo-
vanadium complexes, [VO2L1]2 (1) and [VO2L2]2 (2), where L1
and L2 are the deprotonated forms of 2-bromo-4-chloro-6-{[2-
(2-hydroxyethylamino)ethylimino)methyl]phenol (HL1) and 2-
The two Schiff bases were synthesized according to the
general method. A methanol solution (50 mL) of 2-(2-
aminoethylamino)ethanol (1.0 mmol, 104.1 mg) was added
dropwise to a stirred methanol solution (50 mL) of alde-
hydes (1.0 mmol; salicylaldehyde for HL1 and 3-bromo-5-
chlorosalicylaldehyde for HL2). The mixture was stirred for
30 min and the solvent was then evaporated to give orange oil
product with quantitative yield. Anal. Calcd. for HL1: C, 63.4;
H, 7.7; N, 13.4%. Found: C, 63.2; H, 7.8; N, 13.5%. Anal. Calcd.
for HL2: C, 41.1; H, 4.4; N, 8.7%. Found: C, 41.2; H, 4.5; N,
8.6%. Selected IR data (KBr, cm−1): HL1, 3237 (νN-H), 1633
(νC N); HL2, 3233 (νN-H), 1637 (νC N).
Synthesis of the Complex [VO2L1]2 (1)
A methanol solution (5 mL) of VO(acac)2 (0.1 mmol,
26.5 mg) was added to a methanol solution (10 mL) of HL1
(0.1 mmol, 20.8 mg) under stirring. The mixture was stirred at
room temperature for 30 min to give a brown solution. The re-
sulting solution was allowed to stand in air for a few days. The
brown block-shaped crystals suitable for X-ray single crystal
diffraction were formed at the bottom of the vessel. The iso-
lated product was washed with cold methanol, and dried in air.
Received 5 April 2011; accepted 10 August 2011.
The authors acknowledge the Zhejiang Provincial Natural Science
Foundation of China (project no. Y4090281) for funding this work.
Address correspondence to Shi-Yong Liu, College of Chemistry &
Pharmacy, Taizhou University, Taizhou, Zhejiang 317000, P. R. China.
E-mail: liushiyong2010@yahoo.cn
603

604
S.-Y. LIU AND Y.-P. MA
H
N
Cl
OH
OH
H
N
N
N
OH
OH
Br
HL1
HL2
SCH. 1. HL1 and HL2.
Yield: 49%. Anal. Calcd. for C22H30N4O8V2: C, 45.5; H, 5.2; with HL2 (0.1 mmol, 32.1 mg). Yield: 62%. Anal. Calcd. for
N, 9.7%. Found: C, 45.3; H, 5.3; N, 9.5%. IR data (cm−1): 3343 C22H26Br2Cl2N4O8V2: C, 32.7; H, 3.2; N, 6.9%. Found: C,
(br, m), 3209 (sh, m), 1645 (vs), 1599 (s), 1549 (m), 1472 (m), 32.4; H, 3.3; N, 7.1%. IR data (cm−1): 3345 (br, m), 3213 (sh,
1448 (m), 1417 (w), 1397 (w), 1334 (w), 1297 (s), 1208 (w), m), 1647 (vs), 1597 (s), 1545 (m), 1471 (m), 1448 (m), 1417
1148 (m), 1128 (w), 1088 (m), 1049 (m), 1029 (m), 1005 (m), (w), 1398 (w), 1331 (w), 1297 (s), 1210 (w), 1146 (m), 1128
968 (w), 939 (s), 840 (s), 803 (w), 770 (s), 628 (m), 569 (w), (w), 1088 (m), 1048 (m), 1029 (m), 1012 (m), 973 (w), 937 (s),
447 (w). UV-Vis spectra data in DMSO [nm (ε, M−1 cm−1)]: 845 (s), 802 (w), 770 (s), 621 (m), 568 (w), 439 (w). UV-Vis
254 (1.3 × 104), 372 (3.4 × 103), 552 (173).
spectra data in DMSO [nm (ε, M−1 cm−1)]: 259 (1.4 × 104),
367 (3.2 × 103), 561 (187).
Synthesis of the Complex [VO2L2]2 (2)
The complex was prepared and crystallized according to
Crystal Structure Determination
Diffraction intensities for the complexes were collected at
298(2) K using a Bruker SMART 1000 CCD area-detector
the same method as that described for (1), with HL1 replaced
TABLE 1
Crystal data for the complexes
TABLE 2
Selected bond lengths (Å) and bond angles (◦) for the
complexes
(1)
(2)
Formula
FW
Crystal shape/color
Crystal system
Space group
a (Å)
C22H30N4O8V2 C22H26Br2Cl2N4O8V2
580.4
Block/brown
Monoclinic
P21/n
11.259 (2)
6.843 (2)
16.094 (3)
105.356 (3)
1195.7 (4)
4
807.1
Block/brown
Monoclinic
P21/n
14.003 (2)
6.802 (1)
16.446 (2)
112.391 (2)
1448.4 (3)
2
(1)
V1-O1
V1-O4
V1-N2
O3-V1-O4
O4-V1-O1
O4-V1-N1
O3-V1-N2
O1-V1-N2
O3-V1-O4i
O1-V1-O4i
N2-V1-O4i
1.9084 (19)
1.6775 (18)
2.161 (2)
107.83 (10)
100.34 (9)
151.75 (9)
93.38 (9)
157.16 (9)
171.94 (9)
82.92 (7)
V1-O3
1.606 (2)
2.139 (2)
2.4519 (19)
101.43 (9)
98.43 (9)
84.11 (8)
91.41 (9)
76.53 (8)
77.76 (8)
75.12 (7)
V1-N1
V1-O4i
O3-V1-O1
O3-V1-N1
O1-V1-N1
O4-V1-N2
N1-V1-N2
O4-V1-O4i
N1-V1-O4i
b (Å)
c (Å)
β (◦)
V (Å3)
Z
T (K)
298 (2)
1.612
600
0.838
0.831
298 (2)
1.851
800
3.640
0.488
Dc (g cm−3
F(000)
)
80.51 (7)
(2)
V1-O1
V1-O4
µ/mm−1 (Mo-Kα)
Tmin
1.923 (4)
1.605 (4)
2.191 (5)
107.3 (2)
98.56 (19)
155.08 (19)
91.8 (2)
158.3 (2)
170.72 (18)
84.64 (16)
80.46 (17)
V1-O3
2.322 (4)
2.135 (5)
1.686 (4)
101.26 (19)
96.7 (2)
83.06 (19)
93.9 (2)
78.2 (2)
V1-N1
V1-N2
V1-O3ii
Tmax
0.850
2594/169
1841
0.530
3139/187
1576
O4-V1-O3ii
O3ii-V1-O1
O3ii-V1-N1
O4-V1-N2
O1-V1-N2
O4-V1-O3
O1-V1-O3
N2-V1-O3
O4-V1-O1
O4-V1-N1
O1-V1-N1
O3ii-V1-N2
N1-V1-N2
O3-V1-O3ii
N1-V1-O3
Reflections/parameters
Independent reflections
Restraints
2
2
Goodness of fit on F2
1.023
0.976
R1, wR2 [I ≥ 2σ(I)]a 0.0435, 0.0957
0.0603, 0.1145
0.1483, 0.1478
ꢀ
R1, wR2 (all data)a
0.0681, 0.1070
78.63 (18)
76.77 (16)
ꢀ
ꢀ
ꢀ
aR1 = ||Fo| – |Fc||/ |Fo|, wR2 = [ w(Fo2 – Fc2)2/ w(Fo2)2]1/2
,
w1 = [σ2 Fo2 + (0.0483(Fo2 + 2Fc2)/3)2]−1, w2 = [σ2 Fo2 + (0.0602
(Fo2 + 2Fc2)/3)2]−1
.
Symmetry codes: (i) 1 – x, 2 – y, – z; (ii) 1 – x, 2 – y, 2 – z.

DIOXOVANADIUM COMPLEXES WITH SCHIFF BASES
605
TABLE 3
Hydrogen bond geometry (Å, ◦) for the complexes
D−H· · ·A
(1)
D−H
H· · ·A
D· · ·A D−H· · ·A
N2−H2· · ·O1#1 0.894(10) 2.31(2) 3.116(3) 149(3)
O2−H2A· · ·O4#2 0.848(10) 2.103(11) 2.948(3) 174(4)
O2−H2A· · ·N1#3 0.848(10) 2.69(3) 3.137(3) 114(3)
(2)
O2−H2A· · ·O3#4 0.852(10) 1.93(2) 2.768(7) 168(8)
N2−H2· · ·O1#4 0.897(10) 2.31(5) 3.066(6) 141(7)
Symmetry codes: #1: 1 – x, 2 – y, – z; #2: 1/2 – x, –1/2 + y, –1/2 –
z; #3: –1/2 + x, 3/2 – y, –1/2 + z; #4: 1 – x, 2 – y, 2 – z.
FIG. 1. Molecular structure of the complex (1) at 30% probability displace-
ment. Atoms labeled with the suffix A are at the symmetry position 1 – x, 2 – y,
– z. Hydrogen bonds are drawn as dashed lines.
with MoKα radiation (λ = 0.71073 Å). The collected data
were reduced using the SAINT program,[11] and empirical ab-
sorption corrections were performed using the SADABS pro-
gram.[12] The structures were solved by direct methods and
refined against F2 by full-matrix least-squares methods us-
ing the SHELXTL package.[13] All of the non-hydrogen atoms
were refined anisotropically. H2 atoms attached to N2 in both
complexes were located from difference Fourier maps and re-
fined isotropically, with N−H distances restrained to 0.90(1) Å,
and with Uiso(H) set to 0.08 Å2. Other H atoms in the com-
plexes were placed in calculated positions and constrained to
ride on their parent atoms. The crystallographic data for the
complexes are summarized in Table 1. Selected bond lengths
and angles are listed in Table 2. Hydrogen bonds are listed in
Table 3.
The crystals of the complexes are soluble in DMSO, DMF,
MeCN, MeOH, and EtOH, insoluble in water. The vanadium
in both complexes are +5 oxidation state and therefore EPR
silent.
Structure Description of the Complexes
The molecular structures of the complexes (1) and (2) are
shown in Figures 1 and 2, respectively. Both compounds are
centrosymmetric dimeric dioxovanadium(V) complexes, with
the inversion center located at the midpoint of the two V atoms.
The V atom in each complex is six-coordinated through three
bonds to oxo groups and through bonds to the tridentate Schiff
base ligand, forming an octahedral geometry. The V1-O3 dis-
tance in (1) and the V1-O4 distance in (2) are about 1.605 Å,
indicating them as typical V O bonds. The O4 atom in (1) and
O3 atom in (2) are involved in the bridge between V1 and V1A.
RESULTS AND DISCUSSION
Preparation of the Schiff Bases and the Complexes
The Schiff bases HL1 and HL2 were prepared via the reaction The coordinate bond lengths are comparable to those observed
of equimolar quantities of 2-(2-aminoethylamino)ethanol with in other similar oxovanadium complexes.[14–16] The distortion
salicylaldehyde and 3-bromo-5-chlorosalicylaldehyde, respec- of the octahedral coordination can be observed by the coordi-
tively, in methanol. The two complexes were readily synthesized nate bond angles, ranging from 75.1(1)◦ to 107.8(1)◦ for the
according to the standard procedure (Scheme 2), crystallized as perpendicular angles, and from 151.8(1)◦ to 171.9(1)◦ for the
brown crystals, which are stable in air at room temperature. diagonal angles. In complex (1), there form two intermolecular
OH
NH
X
H
N
OH
N
Y
O
V
Y
MeOH
O
V
N
O
VO(acac)
+
O
2
O
Y
O
OH
N
X
X
HN
HO
SCH. 2. The synthesis of the complexes. (1) X = Y = H; (2) X = Br, Y = Cl.

606
S.-Y. LIU AND Y.-P. MA
FIG. 2. Molecular structure of the complex (2) at 30% probability displace-
ment. Atoms labeled with the suffix A are at the symmetry position 1 – x, 2 – y,
2 – z. Hydrogen bonds are drawn as dashed lines.
N−H· · ·O hydrogen bonds between the two [VO2L1] moieties,
while in complex (2), there form two intermolecular N−H· · ·O
hydrogen bonds and two intermolecular O−H· · ·O hydrogen
bonds between the two [VO2L2] moieties. This might be the
reason that the V· · ·V distance of 3.127(2) Å in (2) is shorter
than that of 3.251(2) Å in (1).
In the crystal structure of the complex (1), the molecules
are linked through intermolecular O−H· · ·O, N−H· · ·O, and
O−H· · ·N hydrogen bonds, to form a 3D network, as shown in
Figure 3. In the crystal structure of the complex (2), there are no
obvious short contacts among the dimers, as shown in Figure 4.
FIG. 4. Molecular packing of the complex (2), viewed along the b axis. Hy-
drogen bonds are drawn as thin dashed lines.
FIG. 3. Molecular packing of the complex (1), viewed along the b axis. Hydrogen bonds are drawn as thin dashed lines.

DIOXOVANADIUM COMPLEXES WITH SCHIFF BASES
607
CONCLUSIONS
bis(maltolato)oxovanadium(IV), a potent insulin mimetic agent. J. Am.
Chem. Soc. 1995, 117, 12759–12770.
In the present study, two new dioxovanadium com-
plexes have been synthesized and characterized by X-
ray diffraction. The Schiff bases 2-bromo-4-chloro-6-{[2-(2-
hydroxyethylamino)ethylimino)methyl]phenol and 2-{[2-(2-
hydroxyethylamino)ethylimino]methyl}phenol coordinate to
the V atoms through the phenolate O, imine N, and amine
N atoms. The hydrogen bonds play an important role in the
self-assembly of the final packing structures of the complexes.
6. Bastos, A.M.B.; da Silva, J.G.; da S. Maia, P.I.; Deflon, V.M.; Batista,
A.A.; Ferreira, A.V. M.; Botion, L.M.; Niquet, E.; Beraldo, H. Oxovana-
dium(IV) and (V) complexes of acetylpyridine-derived semicarbazones ex-
hibit insuline-like activity. Polyhedron 2008, 27, 1787–1794.
7. Borah, B.; Chen, C.W.; Egan, W.; Miller, M.; Wlodawer, A.; Cohen, J.S.
Nuclear magnetic-resonance and neutron-diffraction studies of the com-
plex of ribonuclease: A with uridine vanadate, a transition-state analog.
Biochemistry 1985, 24, 2058–2067.
8. Wlodawer, A.; Miller, M.; Sjolin, L. Active site of RNase: neutron diffrac-
tion study of a complex with uridine vanadate, a transition-state analog.
Proc. Natl. Acad. Sci. USA 1983, 80, 3628–3631.
9. Mokry, L.M.; Carrano, C.J. Steric control of vanadium(V) coordination ge-
ometry: A mononuclear structural model for transition-state-analog RNase
inhibitors. Inorg. Chem. 1993, 32, 6119–6121.
SUPPLEMENTARY MATERIALS
Supplementary crystallographic data are available from
the CCDC, Union Road, Cambridge CB2 1EZ, UK on re-
quest quoting the deposition numbers CCDC 820406 for (1)
and 820407 for (2) (fax: +44 1223 336 033; e-mail: de-
posit@ccdc.cam.ac.uk).
10. Liu, S.-Y.; Zheng, R.-H.; Ma, Y.-P.; You, Z. Synthesis, characterization, and
crystal structures of two dioxovanadium(V) complexes with Schiff bases.
Synth. React. Inorg. Met.-Org. Nano-Met. Chem. 2011, 41, 22–25.
11. Bruker. SMART (Version 5.628) and SAINT (Version 6.02); Bruker AXS,
Inc: Madison, WI, USA, 1998.
12. Sheldrick, G.M. SADABS. Program for Empirical Absorption Correction
of Area Detector; University of Go¨ttingen, Germany, 1996.
13. Sheldrick, G.M. SHELXTL V5.1. Software Reference Manual; Bruker AXS,
Inc: Madison, WI, USA, 1997.
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