Synthesis, characterization and catalytic activity of oxovanadium(IV) complexes of heterocyclic acid hydrazones

Article abstract of DOI:10.14233/ajchem.2015.19115

Two acid hydrazones, furan-2-carbaldehyde nicotinic hydrazone (L1) and furan-2-carbaldehyde benzhydrazone (L2) have been synthesized and they are characterized by elemental analysis, IR, NMR and UV spectral analysis. Oxovanadium(IV) complexes of these two

Full text of DOI:10.14233/ajchem.2015.19115

Asian Journal of Chemistry; Vol. 27, No. 11 (2015), 4135-4137
A
SIAN
J
OURNAL OF HEMISTRY
C
http://dx.doi.org/10.14233/ajchem.2015.19115
Synthesis, Characterization and Catalytic Activity of
Oxovanadium(IV) Complexes of Heterocyclic Acid Hydrazones
*
MANJU PANDEY, K.R. SUNAJA DEVI and P.B.SREEJA
Department of Chemistry, Christ University, Bangalore-560 029, India
*Corresponding author: E-mail: sreeja.pb@christuniversity.in
Received: 18 February 2015; Accepted: 31 March 2015;
Published online: 16 July 2015;
AJC-17419
Two acid hydrazones, furan-2-carbaldehyde nicotinic hydrazone (L1) and furan-2-carbaldehyde benzhydrazone (L2) have been synthesized
and they are characterized by elemental analysis, IR, NMR and UV spectral analysis. Oxovanadium(IV) complexes of these two hydrazones
were synthesized and characterized by elemental analysis, IR, UV, EPR, molar conductivity and magnetic susceptibility measurements.
Conductivity measurements reveal that the complexes are non-electrolytes. Spectral data indicates the square pyramidal geometry for the
monomeric five coordinated oxovanadium(IV) complexes with the general formula [VO(L)(OCH3)]. The complex was studied for its
catalytic activity and was found to be a good catalyst in quinoxaline synthesis.
Keywords: Acid hydrazones, Oxovanadium complexes, EPR spectrum, Square pyramidal, Catalytic activity.
INTRODUCTION
EXPERIMENTAL
Schiff base ligands such as hydrazones are widely studied
for their applications in pharmaceutical and industrial fields1-3.
Over the past few decades, a great deal of attention has been
focused on the complexes formed by transition metal ions with
hydrazones due to their widespread applications and interesting
coordination capability with transition metal ions4-6. The transi-
tion metal complexes of hydrazones have potential applications
as active materials in non-linear optics7, catalysts8, innovative
magnetic materials9, luminescent probes10 and molecular
sensors11.
Introduction of a >C=O group in the hydrazide part increases
the electron delocalization and denticity of the hydrazone and
the resulting compound is known as acid hydrazone. Further,
the number of coordination sites can be increased by suitable
substitution on the hydrazone framework. If a hetero ring is
attached to the hydrazone framework, the hetero atom can also
coordinate to the metal center thus increasing the denticity12.
Another possibility is that if the hydrazide part of hydrazones
contains a hetero atom, it can also involve in bonding. This
unusual coordination can evidently change the way the
complexes are formed13. In the case of complexes with ONO
donor hydrazones we can incorporate heterocyclic bases to
the central metal structure14. We report here the synthesis and
structural studies of some oxovanadium(IV) complexes of
heterocyclic acid hydrazones.
All the chemicals used of AR grade. The solvents were
purified before use by standard procedures. Elemental analysis
for carbon, hydrogen and nitrogen were performed on a Vario
EL III CHNS instrument. The molar conductivity of the
complexes in DMF solution (10-3 M) at room temperature was
measured using a direct reading conductivity meter. The IR
spectrum was recorded on Bruker αT instrument as KBr pellets
in the range 4000-400 cm-1.The 1H NMR spectra were recorded
using Bruker 400 MHz Spectrometer, with CDCl3 as solvent
and TMS as standard. X-band EPR spectra of the complexes
were recorded in the DMF at LNT using JES-FA200 ESR
spectrometer. The magnetic susceptibility measurements were
done on powdered samples at room temperature, using VSM.
The electronic spectrum was recorded by using Shimadzu UV-
visible spectrophotometer instrument.
Preparation of acid hydrazones: Nicotinic hydrazide/
benzhydrazide dissolved in methanol and refluxed with furan-
2-carbaldehyde in the presence of few drops of acetic acid for
6 h. Product was filtered off, washed with methanol and dried.
Compound recrystallized from methanol. The results of the
spectroscopic and composition analyses are as follows.
Furan-2-carbaldehyde nicotinic hydrazone (L1): Colour-
less crystalline solid,Yield: 70 %, m.w.: 215 m.f.: C11H9N3O2,
Anal. calcd. (%): C, 61.39; H, 4.18; N, 19.53. Found, (%): C,
61.7; H, 4.27; N, 19.56. IR (KBr, νmax, cm-1): 3213 ν(NH),

4136 Pandey et al.
Asian J. Chem.
165 2 ν(C=O), 1564 ν(C=N),1H NMR (δ, ppm): 9.1 (NH),
8.7 (C-H, azomethine), 6-8 (Ar-H). UV-visible (DMF, 10-5 M,
cm-1): 31250 (n→π*), 45450 (π→π*).
support the suggested formulae. Methanol and ethanol
solvents used as reaction media can act as co-ligands during
the preparation of the complexes. As the literature suggests
the coordinated methanol in [VO(L)(MeOH)] can be deproto-
nated to yield a methoxy derivative, [VO(L)(OMe)]20,21. The
molar conductivity measurements in 10-3 M DMF solutions
indicated that both the complexes are non-electrolytic in nature.
The values of magnetic moment were found to be close to the
spin only value 1.73 B.M. which indicate the presence of one
unpaired electron. It also proved that there is no interaction
between oxovanadium-oxovanadium moiety.
Furan-2-carbaldehyde benzhydrazone (L2): Colourless
needle-like crystalline solid, Yield: 72 %, m.w.: 214, m.f.:
C12H10N2O2, Anal. calcd. (%): C, 67.29; H, 4.67; N 13.08.
Found (%): C, 67.0 2; H 4.57; N 12.94. IR (KBr, νmax, cm-1): 3
244 ν(NH), 1644 ν(C=O), 1563 ν(C=N),1H NMR (δ, ppm):
9.2 (NH), 8.5 (C-H, azomethine), 6-8 (Ar-H). UV-visible
(DMF, 10-5 M, cm-1): 31750 (n→π*), 45454 (π→π*).
Preparation of the oxovanadium(IV) complexes: To a
solution of furan-2-carbaldehyde nicotinic hydrazone/furan-
2-carbaldehyde benzhydrazone (1 mmol) in methanol (20 mL),
vanadylacetylacetonate (1 mmol) solution in methanol (20 mL)
was added. Mixture was stirred in magnetic stirrer for 5 h. The
resulting solution was allowed to stand at room temperature
for slow evaporation. The precipitate that separated out was
filtered, washed with methanol and dried over P4O10.
Oxovanadium(IV) complex VOL1(OCH3)]: m.w.: 312,
Yield: 55 %, Colour: Dark brown, µeff. (B.M.): 1.87,Anal. calcd.
(%): C, 46.15; H, 3.52; N, 13.46. Found (%): C, 46.83; H,
3.66; N, 13.33, IR (KBr, νmax, cm-1): 1520 ν(C=N), 1582 ν(C=N
(new)), 1374 ν(C-O), 959 ν(V=O); UV-visible (DMF, 10-5 M,
cm-1): 31746 (n→π*), 46200 (π→π*); EPR spectra parameters:
g|| = 1.94, g⊥ =1.99, A|| (cm-1) = 181.11 × 10-4, A⊥ (cm-1) =
46.44 × 10-4.
In V(IV) complexes value of g is below the value for free
electron. The spin of 51V nucleus is I = 7/2. In mononuclear
V(IV) complexes the EPR signals are split into eight hyperfine
lines. VO2+ is one of the most stable diatomic cation and its
paramagnetism is almost due to spin angular momentum. EPR
spectra were recorded in DMF solution at 77K. In frozen DMF,
tumbling motions of the molecules are restricted which results
in anisotropic spectrum. Corresponding parameters are charac-
teristics of square pyramidal oxovanadium(IV) complexes with
C4V symmetry, theV=O bond along z and the other four donor
atoms are along the x, y axes, exhibiting two g (g||, g⊥) and
two A (A||, A⊥) values.The g|| < g⊥ and A|| > A⊥ values are
characteristic of an axially compressed system with unpaired
electron in dxy orbital22,23
.
Based on the above data obtained, the following tentative
structures have been proposed for the present complexes.
Oxovanadium(IV) complexVOL2(OCH3).H2O]: m.w.:
329,Yield: 56 %, Colour: Dark brown, µeff. (B.M.): 1.88,Anal.
calcd. (%): C, 47.41; H, 3.05; N, 7.95. Found (%): C, 47; H,
3.59; N, 7.47; IR (KBr, νmax, cm-1): 1520 ν(C=N), 1594 ν(C=N
(new)), 1366 ν(C-O), 988 ν(V=O); UV-visible (DMF, 10-5 M,
cm-1): 31820 (n→π*), 45600 (π→π*); EPR spectra parameters:
g|| = 1.87, g⊥ = 1.98, A|| (cm-1) = 174.58 × 10-4, A⊥ (cm-1) =
44.36 × 10-4.
O
O
V
O
O
V
O
CH3
O
CH3
H2O
N
O
N
O
N
N
RESULTS AND DISCUSSION
In ligand (L1) strong bands due to the ν(NH) and ν(C=O)
modes at 3213 cm-1 and 1652 cm-1 while in ligand (L2) at 3244
cm -1 and 1644 cm-1 are observed. It suggested that both the
hydrazone exists in the amido form in the solid state15.A promi-
nent band at 1564 cm-1 due to azomethine ν(C=N) linkage is
observed indicating that condensation between carbonyl
compound and that of the hydrazide has taken place16. In both
the complexes absence of strong bands due to (NH) and (C=O)
modes indicated that the ligand coordinates to the metal in
enolate form. A downward shift of the band (C=N) of azome-
thine group suggesting coordination of azomethine nitrogen
to the metal centre17. The band observed at 959 cm-1 and 988
cm-1 are due to the V=O stretching18.
The bands attributed to the transitions of the n→π* and
π→π* of uncomplexed hydrazones are slightly shifted upon
complexation. The bands related to d-d transitions in theVO2+
complex could not be visualized in solution spectrum.
However, the diffuse reflectance spectrum of the complex
could exhibit bands characteristics of a square pyramidal
oxovanadium complex, due to the high concentration of the
complex in the solid state19.
N
[VOL1(OCH3)]
[VOL2(OCH3)]·H2O
Catalytic activity studies:We studied the synthesis of quina-
xaline derivatives using oxovanadium complex [VOL1(OCH3)].
Quinoxaline derivatives are nitrogen-containing heterocycles,
which are important in the fields of medicine as antitumor,
anticonvulsant, antimalarial, anti-inflammatory, antiamoebic,
antioxidant, antidepressant etc.24-26. The classic method for
quinoxaline preparation is the condensation of a 1,2-dicarbo-
nylic compound with a 1,2-diamino compound. In general,
this procedure needs high temperature, the use of a strong
acid catalyst and long reaction times. The salient features of
the present catalytic activity studies were high yields, short
reaction times, mild reaction conditions and operational
simplicity. Synthesis of quinoxaline derivatives were done by
using benzil and different diamines. Benzil (1 mmol) and o-
phenylene-diamine/4-nitro-o-phenylenediamine (1 mmol)
dissolved in 3 mL of methanol/acetonitrile and stirred in room
temperature in the presence of 0.02 g of oxovanadium complex.
The progress of the reaction was monitored by TLC. On
cooling, the crystals of quinoxaline were separated out. It was
The complexes were formulated from the analytical data,
magnetic measurements and molar conductance data. They

Vol. 27, No. 11 (2015)
Synthesis and Catalytic Activity of Oxovanadium(IV) Complexes of Heterocyclic Acid Hydrazones 4137
4.
M.M. Heravi, L. Ranjbar, F. Derikvand, H.A. Oskooie and F.F. Bamoharram,
J. Mol. Catal. Chem., 265, 186 (2007).
then dried over P4O10. The compounds were recrystallized from
methanol and acetonitrile (Table-1) and characterized by
spectral methods.
5. R.C. Maurya and S. Rajput, J. Mol. Struct., 833, 133 (2007).
6. U.O. Ozmen and G. Olgun, Spectrochim. Acta A, 70, 641 (2008).
7. F. Cariati, U. Caruso, R. Centore, W. Marcolli, A.D. Maria, B. Panunzi,
A. Roviello and A. Tuzi, Inorg. Chem., 41, 6597 (2002).
8. O. Pouralimardan, A.-C. Chamayou, C. Janiak and H. Hosseini-Monfared,
Inorg. Chim. Acta, 360, 1599 (2007).
9. S. Banerjee, S. Sen, S. Basak, S. Mitra, D.L. Hughes and C. Desplanches,
Inorg. Chim. Acta, 361, 2707 (2008).
10. C. Basu, S. Chowdhury, R. Banerjee, H.S. Evans and S. Mukherjee,
Polyhedron, 26, 3617 (2007).
11. M.O. Bakir, O. Green and W.H. Mulder, J. Mol. Struct., 873, 17 (2008).
12. A. Ray, S. Banerjee, S. Sen, R.J. Butcher, G.M. Rosair, M.T. Garland and
S. Mitra, Struct. Chem., 19, 209 (2008).
13. C.M. Armstrong, P.V. Bernhardt, P. Chin and D.R. Richardson, Eur. J.
Inorg. Chem., 1145 (2003).
14. P.B. Sreeja, M.R.P. Kurup, A. Kishore and C. Jasmin, Polyhedron, 23,
575 (2004).
15. S.N. Rao, D.D. Mishra, R.C. Maurya and N.N. Rao, Polyhedron, 16,
1825 (1997).
TABLE-1
EFFECT OF SOLVENT ON SYNTHESIS OF QUINOXALINE
Time
(min)
2
3
Yield
(%)
96
92
92
Compound
Solvent
MeOH
2,3-Diphenyl quinoxaline
2,3-Diphenyl quinoxaline
6-Nitro-2,3-diphenyl quinoxaline MeOH
Acetonitrile
180
2,3-Diphenyl quinoxaline:White solid, m.p.: 125-128 °C,
m.f.: C20H14N2, m.w.: 282, IR (KBr, νmax, cm-1): 3055, 1620,
1577, 1H NMR (CdCl3) δ (ppm): 7.3 (m, 6H), 7.5 (d, 4H), 8.6
(d, 2H), 7.75 (t, 2H).
6-Nitro,2,3-diphenyl quinoxaline: White solid, m.p.:
193-194 °C, m.f.: C20H13N3O2, m.w.: 327, IR (KBr, νmax, cm-1):
3055, 1600, 1570, 1370.
16. N. Mathew, M. Kuriakose, E.B. Seena and M.R.P. Kurup, Acta Cryst.,
E63, o2190 (2007).
17. M. Carcelli, P. Cozzini, T. Maccagni, C. Pelizzi and L. Righi, Inorg.
Chim. Acta, 303, 238 (2000).
Conclusion
18. N.A. Mangalam and M.R.P. Kurup, Spectrochim. Acta A, 71, 2040 (2009).
19. S.A. Sallam, Transition Met. Chem., 30, 341 (2005).
20. M.R. Maurya, Coord. Chem. Rev., 237, 163 (2003).
21. R. Bikas, H. Hosseini-Monfared, E. Jeanneau and B. Shaabani, J.
Chem., Article ID 546287 (2013).
22. D. Collison, B. Gahan, C.D. Garner and F.E. Mabbs, J. Chem. Soc.,
Dalton Trans., 1980, 667 (1980).
23. F.E. Dickson, C.J. Kunesh, E.L. McGinnis and L. Petrakis, Anal. Chem.,
44, 978 (1972).
We carried out the experiment without catalyst under
identical conditions. Only very low amount of substrate was
converted in the reaction (below 80 %) and took 3 h for first
derivative and 24 h for the second derivative suggesting that
our complex is functioning as a catalyst for quinoxaline synthesis.
It proved that oxovanadium complexes have the advantages
of high activity and short reaction times as a catalyst for the
synthesis of quinoxaline.
24. P. Corona, A. Carta, M. Loriga, G. Vitale and G. Paglietti, Eur. J. Med.
Chem., 44, 1579 (2009).
25. Q. Weng, D. Wang, P. Guo, L. Fang, Y. Hu, Q. He and B. Yang, Eur. J.
Pharmacol., 581, 262 (2008).
26. S. Wagle, A.V. Adhikari and N.S. Kumari, Eur. J. Med. Chem., 44, 1135
(2009).
REFERENCES
1. C. Loncle, J.M. Brunel, N. Vidal, M. Dherbomez and Y. Letourneux,
Eur. J. Med. Chem., 39, 1067 (2004).
2. B.K. Kaymakcioglu and S. Rollas, Farmaco, 57, 595 (2002).
3. R. Maccari, R. Ottana and M.G. Vigorita, Bioorg. Med. Chem. Lett.,
15, 2509 (2005).