M.L. Sharma et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 95 (2012) 562–568
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procured from Aldrich Chemical Co., England. 3-(Phenyl/substi-
tuted phenyl)-4-amino-5-hydrazino-1,2,4-triazoles were prepared
by a previously reported method [20]. The progress of the reaction,
throughout the synthesis, was monitored by TLC. The physical
measurements and analytical methods were the same as those de-
scribed previously. Elemental analyses (C, H and N) were measured
with a Perkin–Elmer 1400C analyzer. The vanadium metal was esti-
mated gravimetrically as vanadate. Infrared spectra (4000–
200 cmꢀ1) of the ligands and complexes were recorded as KBr
pellets on a Nicolet-5700 FTIR spectrophotometer. The room tem-
perature magnetic susceptibilities were measured by Gouy’s meth-
od using Hg[Co(NCS)4] as calibrant. Electronic spectra of the
complexes were recorded on Varian Cary-100 Bio UV–Vis spectro-
photometer using DMSO as solvent. Conductance measurements
were recorded in DMSO (10ꢀ3 M) using Elico conductivity bridge
type CM-82, provided with a dip type conductivity cell fitted with
Pt electrodes. EPR spectra of the complexes were recorded at room
temperature and at liquid N2 temperature using Varian E-4 X-band
EPR spectrometer operating at microwave frequency ꢁ9.1 GHz.
Field calibration was checked using tetracyanoethylene (TCNE) free
radical for which g = 2.00277 at room temperature. The particle size
of the complexes has been calculated by analysis of the X-ray dif-
fraction pattern, obtained using an X-ray powdered diffractometer
STZ (50 mg/kg body weight) in 0.1 M citrate buffer (pH 4.5). After
48 h, rats with blood glucose levels above 200 mg/dL were consid-
ered as diabetic rats and were used for the present study.
After 29 days of treatment (Group I–IV), the animals were
fasted overnight and then sacrificed. Blood was collected using
EDTA as anticoagulant. The blood was used for the estimation of
glucose, urea and haemoglobin [23]. The plasma was used for the
assay of cholesterol, creatinine and proteins [23].
3. Results and discussion
A new series of diazadioxa macrocyclic oxovanadium(IV) com-
plexes have been prepared by the template synthesis of Schiff
bases (L) derived from 3-(phenyl/substituted phenyl)-4-amino-5-
hydrazino-1,2,4-triazoles and 1,4 dibromobutane in the presence
of vanadyl sulfate in 1:1:1 M ratio (Scheme 1). All the macrocyclic
oxovanadium(IV) complexes are dark green coloured polycrystal-
line solids and the elemental analyses data agree well with the pro-
posed mononuclear macrocyclic framework. The complexes are
stable in the atmosphere and are soluble in DMF, DMSO, acetone
and nitrobenzene. The molar conductance values of the complexes
in nitrobenzene lies in the range 72–80 Oꢀ1 cm2 molꢀ1, indicating
1:1 electrolytic nature. The presence of ionic sulfate group outside
the coordination sphere has also been confirmed by the appear-
ance of white precipitate with BaCl2 solution.
(Rigaku Geigerflex) with CuKa 1(k = 1.54060 Å) source.
2.1. Synthesis of Schiff bases (H2L) derived from 3-(phenyl/substituted
phenyl)-4-amino-5-hydrazino-1,2,4-triazoles and salicylaldehyde/2-
hydroxy acetophenone [20]
3.1. Magnetic moment and electronic spectra
The room temperature magnetic moments of the oxovana-
dium(IV) complexes lie in the 1.70–1.78 B.M. range. These values
are well suited for oxovanadium(IV) complexes with one unpaired
electron [24]. The electronic spectra of the oxovanadium(IV) com-
plexes in DMF show three distinct bands in the regions of 12,200–
A mixture of 3-(phenyl/substituted phenyl)-4-amino-5-hydra-
zino-1,2,4-triazoles and salicylaldehyde/2-hydroxy acetophenone
in 1:2 M ratio, respectively, was refluxed in ethanol (30 mL) con-
taining few drops of hydrochloric acid for 5–6 h. Solvent was re-
moved and the products, so obtained, were recrystallized from
ethanol: ether mixture.
12,500, 16,000–16,500 and 22,400–25,000 cmꢀ1 The electronic
.
spectra of two representative complexes are shown in Fig. 1. The
position of these bands are nearly the same as reported for other
five-coordinated (C4v symmetry) oxovanadium(IV) complexes
[25,26]. Several schemes have been advanced to interpret the elec-
tronic spectra of oxovanadium(IV) complexes [27–30]. However,
the scheme developed by Ballhausen and Gray (the BG scheme)
can account well for complexes confirming both to idealized and
low symmetry systems [27]. On the basis of Ballhausen and Gray
energy level scheme, these bands can be assigned to
2.2. Synthesis of oxovanadium(IV) macrocyclic complexes
A mixture of appropriate Schiff base, derived from 3-(phenyl/
substituted phenyl)-4-amino-5-hydrazino-1,2,4-triazole and sali-
cylaldehyde/2-hydroxyacetophenone (1 mmol), 1,4-dibromobu-
tane (1 mmol) and oxovanadium sulfate (1 mmol) was refluxed
in ethanol for ꢁ8 h. The compound separated in the form of crys-
tals from the clear solution of the mixture was filtered, washed
several times with cold ethanol and then dried in vacuo.
The empirical formulae, colour, percentage yield, elemental
analyses and molar conductance values are listed in the Table 1.
Synthesis of the ligands and their corresponding macrocyclic com-
plexes are schematically represented in the Scheme 1.
p
b2 ? eꢂ (2B2 ? E), b2 ? bꢂ1(2B2 ? 2B1) and b2 ? aꢂ1(2B2 ? 2A1)
transitions in increasing order of energy. The second transition cor-
responds to 10 Dq. One more band is observed at ca. 32,000–
35,000 cmꢀ1 due to intra-ligand transition.
3.2. Infrared spectra
2.3. In vivo studies to test the anti-diabetic properties of the complexes
The important infrared spectral bands of the ligands and the
metal complexes are presented in Table 2. The tentative assign-
ments for the compounds were made by comparing the spectra
with reported literature on similar systems [20,28]. The acyclic li-
gands (L) and their corresponding oxovanadium(IV) macrocyclic
The animal study was carried out according to the guidelines of
Animals Ethics Committee (Zoology Department, D.D.U. Gorakhpur
University). The experiments were designed and conducted as
mentioned in the literature [21,22]. Male albino rats of Wistar
strain (150–180 g) were used for the present study. The rats were
randomly divided into four groups. Group I: control animals
administered with saline (n = 6). Group II: control animals admin-
istered with [VO(mac1)]SO4 (aqueous suspension of 5 mg/kg body
weight/mL/daily orally for 30 days) (n = 6). Group III: STZ-induced
diabetic animals (n = 6). Group IV: STZ-induced diabetic animals
treated with [VO(mac1)]SO4 ((aqueous suspension of 5 mg/kg body
weight/mL/daily orally for 30 days) (n = 6).
complexes show a band at ca. 3210 assigned [11] to m(NAH). The
strong characteristic peak for azomethine nitrogen appears in the
1640–1620 cmꢀ1 region which shifts downwards (ca. 20–
15 cmꢀ1) in the complexes indicating [20] a decrease in the bond
order of C@N due to the coordination of the azomethine nitrogens
to vanadyl ion. This has further been confirmed by the appearance
of medium bands at ca. 425–410 cmꢀ1 assignable [31] to
m(VAN).
The infrared spectra of the acyclic ligands show medium bands
in the 3410–3380 cmꢀ1 due to phenolic oxygens. This disappears
in their corresponding oxovanadium(IV) complexes indicating the
For the preparation of diabetic rats, animals were kept fasting
for 24 h. Diabetes was induced by intraperitoneal injections of
Sharma
