Synthesis, spectral and biological studies of Cu(II), Ni(II), Fe(III), Co(II), Mn(II) and Cd(II) complexes of 3-acetyl-4-hydroxy-6-methyl-2H-pyran-2-one Schiff base derived from 3-amino-1,2,4-triazole

Article abstract of DOI:10.14233/ajchem.2017.20668

The solid metal complexes of Cu(II), Ni(II), Fe(III), Co(II) Mn(II) and Cd(II) with novel Schiff base ligand derived from 3-acetyl-4-hydroxy-6-methyl-2H-pyran-2-one and aromatic primary amine, 3-amino-1,2,4-triazole were synthesized and characterized by elemental analysis, FTIR, UV-visible, ¹H NMR and XRD spectroscopic techniques. The signals of ¹H NMR spectra and important bands in IR spectra are considered and discussed in relation to molecular structure of ligand. The UV-visible absorption bands are assigned to corresponding electronic transitions, which are also studied by magnetic study. The biological (antibacterial and antifungal) activity of ligand and its metal complexes have been screened in vitro against Bacillus subtilis, Staphylococcus aureus, Aspergillus niger and Candida albicans. Schiff base ligand as well as all metal complexes have shown significant biological activities.

Full text of DOI:10.14233/ajchem.2017.20668

Asian Journal of Chemistry; Vol. 29, No. 10 (2017), 2167-2170
ASIAN JOURNAL OF CHEMISTRY
https://doi.org/10.14233/ajchem.2017.20668
Synthesis, Spectral and Biological Studies of Cu(II), Ni(II), Fe(III), Co(II),
Mn(II) and Cd(II) Complexes of 3-Acetyl-4-hydroxy-6-methyl-2H-
pyran-2-one Schiff Base Derived from 3-Amino-1,2,4-triazole
*
D.G. PALKE and S.D. SALUNKE
Department of Chemistry & Analytical Chemistry, Rajarshi Shahu Mahavidyalaya (Autonomous), Latur-413 512, India
*
Corresponding author: Fax: +91 2382 253645; Tel: +91 2382 245933; E-mail: salunke_shridhar@yahoo.co.in
Received: 25 March 2017; Accepted: 28 June 2017; Published online: 31 August 2017;
AJC-18513
The solid metal complexes of Cu(II), Ni(II), Fe(III), Co(II) Mn(II) and Cd(II) with novel Schiff base ligand derived from 3-acetyl-4-
hydroxy-6-methyl-2H-pyran-2-one and aromatic primary amine, 3-amino-1,2,4-triazole were synthesized and characterized by elemental
1
1
analysis, FTIR, UV-visible, H NMR and XRD spectroscopic techniques. The signals of H NMR spectra and important bands in IR
spectra are considered and discussed in relation to molecular structure of ligand. The UV-visible absorption bands are assigned to
corresponding electronic transitions, which are also studied by magnetic study. The biological (antibacterial and antifungal) activity of
ligand and its metal complexes have been screened in vitro against Bacillus subtilis, Staphylococcus aureus, Aspergillus niger and Candida
albicans. Schiff base ligand as well as all metal complexes have shown significant biological activities.
Keywords: 3-Acetyl-4-hydroxy-6-methyl-2H-pyran-2-one, Schiff bases, Metal complexes, Biological activity.
were dried and distilled before use following the literature reported
INTRODUCTION
procedure [1].
3
-Acetyl-4-hydroxy-6-methyl-2H-pyran-2-one (DHA)
The C, H and N analysis of the compounds were obtained
on Perkins Elmer CHNAnalyzer (2400). The IR spectra of ligand
and the metal complexes were recorded by KBr pellet method
on Perkin Elmer (1430) FTIR spectrophotometer in the range
and its derivatives constitute an important class of compounds
in organic synthesis, especially as starting material for the
preparation of various heterocyclic systems viz. Schiff bases,
Mannich bases, chalcones, etc. The Schiff bases are one of the
most widely used chelating ligands in coordination chemistry.
Herein we describe the synthesis and characterization of
the Schiff base derived from 3-acetyl-4-hydroxy-6-methyl-2H-
pyran-2-one (DHA) and 3-amino-1,2,4-triazole as well as their
synthesized metal complexes with Cu(II), Ni(II), Fe(III), Co(II),
Mn(II) and Cd(II). The Schiff base and metal complexes were
-1
1
4
000-400 cm . The H NMR spectrum of ligand is recorded
on Brucker FT-300 MHz NMR spectrophotometer in CDCl
3
by using TMS as reference. The electronic spectral measure-
ments were made on Shimadzu UV-visible spectrophotometer
UV160, Magnetic susceptibility measurements were carried
out with on Gouy’s balance at laboratory temperature by using
Hg[Co(CNS) ] as standard. The TG and DT analysis were
4
1
characterized by elemental analysis, FTIR, UV-visible, H
NMR, XRD spectroscopic techniques and their magnetic
profiles are recorded and discussed herein. The biological
carried out in 25-1000 °C range. The biological (antibacterial
and antifungal) activities of ligand and metal complexes were
screened in vitro against Staphylococcus aureus (NCIM-2079)
and Bacillus subtilis (NCIM from 24 h cultures of microorganisms
were adjusted to 0.5 McFarland. Muller-Hinton Petri dishes-
(
antibacterial and antifungal) activities of ligand and its
metal complexes have been screened in vitro against Bacillus
subtilis, Staphylococcus aureus, Aspergilus niger and Candida
albicans.
2063, B. subtilis) as bacterial strains and Candida albicans
(
MTCC-227) and Aspergillus niger (NCIM-545) as fungal
strains were used. For the study of antibacterial activity suspen-
sions in sterile peptone water of 90 mL were prepared and
inoculated using these suspensions. Wells (6 mm in diameter)
containing 100 µL of the substance to be tested (at a concentration
of 1 mg/mL in DMSO) were formed in a circular pattern in each
using a ruler. Streptomycin was used as a reference substance.
EXPERIMENTAL
3
-Acetyl-4-hydroxy-6-methyl-2H-pyran-2-one (DHA)
was procured from E-Merck, Germany, 3-amino-1,2,4-triazole
was obtained fromAvra. Metal chlorides were purchased from
E. Merck as well as from Loba chemie Pvt. Ltd. The solvents

2
168 Palke et al.
Asian J. Chem.
For antifungal activity, the same procedure was repeated with
replacement of peptone water with phosphates buffered saline
RESULTS AND DISCUSSION
Synthesized Schiff base is yellowish solid, stable to air
non-hygroscopic, insoluble in water and soluble in hot alcohols.
The melting points were determined by open capillaries. All
the metal complexes are coloured solids, stable to air non-hygro-
scopic (Table-1). They are insoluble in water, methanol, ethanol,
but soluble in DMF and DMSO.
(
(
PBS) and Muller-Hinton medium with yeast peptone dextrose
YPD) medium. Griesofulvin was used as reference. Incubation
of the plates was done at 37 °C for 24 h. Reading of the results
was done by measuring the diameters of the inhibition zones
generated by the tested substances [2].
Synthesis of Schiff bases: Schiff base motif (L
prepared by the addition of ethanolic solution of 3-amino-
,2,4-trizole (0.05 mol) into ethanolic solution of DHA (0.05
1
) was
Ar
1
OH
Cl
mol). The reaction mixture was subjected to reflux for 8 h on
rotamantle. The yellowish coloured Schiff base separated out
as solid upon cooling subsequently followed by filtration. The
recrystallization is subsequently done in dry ethanol. The purity
was ascertained by TLC technique and melting point [3].
O
O
O
N
O
O
N-Ar
M
MCl2
+
2
N
Cl
O
O
O
Ar
L
ML
M = Cu(II), Ni(II), Co(II), Mn(II),
Zn(II) Cd(II) and Fe(III)
Synthesis of metal complexes
OH
OH
IR spectra: The characteristic IR frequencies of the ligand
O
and metal complexes are shown in Table-2. The IR spectrum
of synthesized free ligand revealed a broad weak absorption
N-Ar
H N-Ar
2
+
-1
O
O
band at 3400 to 3100 cm appear due to intramolecular hydrogen
-1
O
O
bonding of ν(O-H). The band at 1689 cm is assigned to ν(C=O)
DHA
-1
L1
lactone carbonyl, 1654 cm is assigned to ν(C=N) (azomethine),
Ar -NH = 3-amino-1,2,4-triazole
-1
2
1
360 cm is assigned to ν(C-N) aryl azomethine and 1257
-1
cm is assigned to ν(C-O) enolic are in tune with the literature
Synthesis of Schiff bases
-
1
values. The disappearence of band at 3400-3100 cm in the
spectra of all the metal complexes indicates deprotonation of
enolic oxygen and azomethine nitrogen due to coordination
to the metal ion. It is further supported by downward shift in
band due to ν(C=N) and upward shift in band due to ν(C-O)
and ν(C-N) azomethine. This indicates the coordination of
azomethine ‘N’and enolic ‘O’ in complex formation. The IR
spectra of the metal complexes showed new bands in the region
Synthesis of metal complexes: Refluixing of methanolic
solution (0.002 mol) of DHA Schiff base (L ) treated with
refluxing with methanolic solution (0.001 mol) of Cu(II), Ni(II),
Fe(III), Co(II) and Mn(II) and Cd(II) metal chloride in 2:1
1
molar ratio yielded corresponding metal complexes (ML ) after
1
the addition of 10 % methanolic solution of ammonia at different
pH values. Solid metal complexes were filtered, washed with
hot methanol and petroleum ether and dried over anhydrous
calcium chloride in vacuum desiccator.
-1
-1
650-540 cm and 580-450 cm , which can be assigned to ν(M-O)
and ν(M-N) vibrations, respectively [4].
TABLE-1
ANALYTICAL DATA OF SYNTHESIZED COMPOUNDS
Elemental analysis (%): Found (calcd.)
Compound
Colour
Yellow
f.w.
m.p. (°C)
C
H
N
M
–
C H N O (L )
234.00
638.47
597.70
630.21
705.93
522.94
834.22
180
51.29 (51.28)
38.8) (37.59)
40.20 (40.15)
39.00 (38.08)
33.38 (33.99)
45.28 (45.89)
28.64 (28.76)
4.27 (4.27)
3.20 (3.13)
3.22 (3.35)
3.27 (3.17)
2.68 (2.83)
3.67 (3.83)
2.30 (2.39)
23.95 (23.93)
17.6 (17.54)
18.64 (18.74)
18.00 (17.77)
14.93 (15.87)
20.85 (21.42)
13.11 (13.42)
10
10
4
3
1
Cu(C H N O ) Cl
Green
> 250
> 250
> 250
> 250
> 250
> 250
9.85 (9.95)
9.9 (9.82)
8.88 (8.86)
8.74 (8.35)
10.63 (10.51)
13.22 (13.47)
10
10
4
3
2
Ni(C H N O )Cl
Greenish
Brown
Pink
Yellowish
Yellow
10
10
4
3
2
Fe(C H N O )Cl
10
10
4
3
3
Co(C H N O )Cl
10
10
4
3
2
Mn(C H N O )Cl
10
10
4
3
2
Cd(C H N O )I
10
10
4
3
2
TABLE-2
-
1
CHARACTERISTICS IR FREQUENCIES (cm ) OF THE LIGAND AND ITS METAL COMPLEXES
Compound
ν(C=O)
ν(C=C)
ν(C=N)
ν(C–N)
ν(C–O)
ν(M–O)
ν(M–N)
C H N O (L )
1689
1714
1717
1701
1697
1694
1707
1559
1566
1553
1579
1577
1554
1573
1654
1650
1642
1649
1643
1648
1645
1360
1361
1373
1365
1375
1364
1368
1257
1263
1262
1261
1268
1267
1264
–
–
1
0
10
4
3
1
Cu(II)L1
Ni(II)L1
Fe(III)L1
CO(II)L1
Mn(II)L1
Cd(II)L1
542
566
547
556
553
559
480
465
466
478
480
473

Vol. 29, No. 10 (2017)
Studies of Transition Metal(II) Complexes of 3-Acetyl-4-hydroxy-6-methyl-2H-pyran-2-one Schiff Base 2169
1
1
H NMR: The H NMR spectra of ligand in CDCl
3
at
ponding to d value 6.2444. The diffractogram of Ni complex
had 9 reflections with maxima at 2θ 12.78° corresponding to
d value 8.3366. The X ray diffraction pattern of these complexes
with respect to major peaks of relative intensity greater than 10 %
has been indexed by using computer program [13]. The above
indexing method also yields Miller indices (h k l), unit cell para-
meter and unit cell volume. The unit cell of Cu complex yielded
values of lattice constant a = 14.7884 Å, b = 7.5475 Å and c =
laboratory temperature showed the signals at δ (ppm) values
for L 2.28 (3H, s, C -CH ), 16.00(1H, s, C -H), 5.94 (1H, s,
-H), 2.67 (3H, s, N = C-CH ) methyl hydrogen linked carbon
azomethine, for DHA moiety 13.30 (1H, s, NH) 7.27(1H, s,
1
6
3
3
C
5
3
C
5
-H) of triazole moiety.
Magnetic moment and electronic absorption spectra:
The magnetic and electronic spectral data is given in Table-3.
The data is of significance for the projected structure of complexes.
The electronic spectra of the Cu(II) complex in DMSO shows
the bands at 10976 and 15524 cm due to Eg → T2g transition
which is characteristic of distorted octahedral geometry. This
further supported by magnetic moment value (1.79 µeff) within
3
5.8163 Å and unit cell volumeV = 649.1889 Å . In concurrence
with these cell parameters, the condition such that a ≠ b ≠ c
and α = β = γ = 90° required for sample to be orthorhombic
was tested and found to be satisfactory. The unit cell of Ni(II)
complex yielded values of lattice constant a = 18.3652 Å, b =
4.7725 Å and c- = 9.4358 Å and unit cell volumeV = 827.0282
-
1
2
2
9
the required range for d -system [5]. The electronic spectra of
3
the Ni(II) complex shows three bands in the range 10476 (ν
1
),
) assigned to the transitions A2g(F)
2g and a charge transfer transition, respectively, signifying
Å . In concurrence with these cell parameters, the condition
3
1
→
5234 (ν
T
2
) and 24231 (ν
3
such that a ≠ b ≠ c and α = γ = 90° ≠ β required for sample to be
monoclinic was tested and found to be satisfactory. Hence, it
3
square planar geometry of the complexes [6,7].Also the diamag-
netic nature supports to the above geometry by it’s magnetic
moment value (2.87 µeff). The electronic absorption spectrum
can be concluded that CuL
1
complex is orthorhombic crystal
system while NiL complex is monoclinic crystal system. The
1
experimental density value of complexes were obtained by
of Co(II) complex has three bands in the range 12453 (ν
1
),
using specific gravity method [14,15] and found to be 2.4686
3
1
8547 (ν ) and 27472 (ν ) which may be endorsed to three spin-
2
3
and 2.0478 g/cm for CuL
1
and NiL complexes, respectively.
1
4
4
4
4
allowed transitions T1g (F) → T2g (F), T1g (F) → A2g (F) and
TGA-DTA analysis: The consecutiveTGA and DTA exami-
nation of Cu(II), Ni(II), Co(II), Mn(II) and Fe(III) metal complexes
was studied from ambient temperature to 1000 °C under an inert
nitrogen atmosphere using alumina as reference. The TG curve
Cu(II) and Ni(II) metal complexes up to 220 °C showed no
change indicating the absences of coordinated water [16,17].
Therefore, the complexes exhibit high thermal stability. The
TG thermograms show single step exothermic peak at 323 °C
which specify the decomp-osition temperature of the complexes.
The complexes start decomposing partially giving metal oxide
at 323 °C, the organic part completely decomposes in the
temperature of range 335-483 °C as indicating by DTA curve.
The TG curve of Co(II) complex shows two stages decompo-
sition. The weight loss encountered at 90 °C supported by
broad exothermic peak in TG curve which is characteristic of
lattice water, second step was encountered at 190 °C where
the organic constituent of the complex starts breaking and
decomposes at 337 °C. It is supported by the two endothermic
peaks at 310 and 391 °C in DTA curve. The constant weight
after 391 °C corresponds to cobalt oxide as final product. The
thermogram of Mn(II) complex shows decomposition tempe-
rature at 240 °C indicated by sharp peak the organic part comp-
letely decompose in the temperature range 230-280 °C which
was supported by DTA curve. The TG curve of Fe(III) complex
shows an exothermic peak at 180 °C which may be decompo-
sition temperature of organic matter and exothermic peak at
4
4
T
1g (F) → T2g(P), respectively, signifying an octahedral geometry
[5]. The effective magnetic moment value (4.8 µeff) was found
to be well within the range as expected for octahedral geometry.
The electronic spectra Mn(II) complex showed two bands at
-
1
-1
6
1
→
7456 cm (ν
1
) and 24756 cm (ν
2
) assigned to transition A1g
4
6
4
T
1g and A1g → T2g, respectively, indicating tetrahedral
geometry. The magnetic moment value (5.07 µeff) which is
slightly lower than the spin only value expected for tetrahedral
Mn(II) complex [7]. This may be due to the presence of magnetic
exchange and small traces of Mn(II) species [8]. In addition to
metal analysis, this is an additional evidence for the dimeric
nature of Mn(II) complex.The subnormal magnetic moment value
is investigative of metal-metal interaction supporting dimeric
nature. The electronic spectra of the Fe(III) complex showed three
-
1
bands at 16984 (ν
1
), 24258 (ν
2
) and 31532 cm (ν ) assigned
3
6
4
6
4
6
4
to transitions A1g → T1g(D), A1g → T1g and A1g → T1g
,
B
respectively and the magnetic moment value (5.8 µ ) signifying
high spin octahedral geometry [9-12].
TABLE-3
MAGNETIC AND ELECTRONIC ABSORPTION
SPECTRAL DATA (DMSO) OF THE COMPLEXES
-1
Compound
µeff
ν (cm )
Geometry
Cu(II)L1
Ni(II)L1
Fe(III)L1
CO(II)L1
Mn(II)L1
Cd(II)L1
1.79
2.87
5.80
4.80
5.07
1.75
10976, 15524
Distorted octahedral
10476, 15234, 24231 Square planner
16984, 24258, 31532 Octahedral
12453, 18547, 27472 Octahedral
17456, 24756
20400, 24378, 25700 Octahedral
390 °C indicate decomposition temperature of the complex.
Octahedral
The FeO is obtained as the end product at 474 °C as showed
in DTA curve. All the complexes finally decomposed to their
metal oxides [9,10,18].
XRD powder diffraction: The powder X ray diffraction
of Cu and Ni complexes was screened in the range 5 to 70° at
wavelength λ 1.543 Å The diffractogram and associated data
depict the data 2θ values of each peak relative intensity and inter
planar spacing (d-values). The diffractogram of Cu complex
Biological evaluation: in vitroAntibacterial and antifungal
activity was screened by considering zone of inhibition of growth.
The synthesized compounds were screened and compared with
standard antibiotics such as streptomycin (1 mg/mL) and
griesofluvin (1 mg/mL). It was found that metal complexes have
good activity than ligand under similar condition [19,20].
of L ligand has 12 reflections with maxima at 2θ 14.19° corres-
1

2
170 Palke et al.
Asian J. Chem.
All the compounds were found moderate in growth inhi-
are also grateful to Director, BCUD, SRTM University, Nanded
and Head of the Department of Chemistry & Analytical
Chemistry. Special thanks to Dr. S.H. Kathwate, Department
of Microbiology, Savitribai Phule Pune University, Pune, India
and Dr.V.S. Shembekar, Department of Biotechnology,
Rajarshi Shahu Mahavidyalaya (Autonomous) Latur, India for
useful suggestions.
bition against B. subtilis with maximum zone of inhibition
mm (compound L , FeL and CoL ) and minimum zone of
inhibition 5 mm (CuL ).Against S. aureus, the compounds L
CoL and MnL have showed 13, 13 and 14 mm zone of
inhibition while compound CuL , NiL , FeL and CdL showed
2 mm zone of inhibition. Compound MnL showed maximum
zone of inhibition (14 mm). Compound L , CuL , FeL , CdL
and CoL has showed 12 mm, 12 mm, 10 mm, 10 mm, and 13
mm, respectively. Lowest activity was showed by compound
NiL with 9 mm zone of inhibition against A. niger. Maximum
zone of inhibitory zone was showed by compound CuL
mm), moderate activity by compounds L , NiL and FeL
mm) and MnL (14 mm) while compound CoL
9
1
1
1
1
1
,
1
1
1
1
1
1
1
1
1
1
1
1
REFERENCES
1
1
2
.
.
A.I.Vogel, Text Book of Practical Organic Chemistry, Longman, London,
edn 5, pp. 400-401 (1989).
W. Rahman, Z. Hassan, U. Rashid, F. Rahim, U.R.A. Obaid and M.
Waseem, Med. Chem. Res., 23, 2207 (2014);
1
1
(18
(15
1
1
1
https://doi.org/10.1007/s00044-013-0828-5.
1
1
and CdL
1
3
4
5
6
7
8
9
.
.
.
.
.
.
.
G. Reddelien, Ber., 46, 2712 (1913);
https://doi.org/10.1002/cber.19130460340.
K. Namkamoto, Infrared Spectra of Inorganic and Coordination Compounds,
Wiley Interscience, New York, edn. 3 p. 159, 167 and 714 (1970).
B.N. Faiggis, Introduction to Ligand Fields; Interscience, London
showed minimum zone of inhibition (12 mm) against human
opportunistic pathogen, C. albicans.
TABLE-4
BIOACTIVITY SCREENING DATA
(
1966).
K.M. Reddy, M.B. Halli and A.C. Hiremath, J. Indian Chem. Soc., 71,
118 (1994).
R.N. Patel, V.L.N. Gundla and D.K. Patel, Indian J. Chem., 47A, 353
a
a
a
a
Sample
Streptomycin
Griesofluvin
L1
CuL1
NiL1
B. subtilis
S. aureus
19.5
NA
13
A. niger
NA
25
C. albicans
16
NA
9
5
6
9
9
8
NA
22
15
18
15
15
12
14
12
(
2008).
A.B.P. Lever, Inorganic Electronic Spectroscopy, Elsevier, Amsterdom
1968).
12
12
9
10
13
14
10
(
12
12
12
13
14
12
P.S. Mane, S.D. Salunke, S.G. Shirodkar and T.K. Chondhekar, Asian J.
Chem., 13, 1573 (2001).
FeL1
10.
P.S. Mane, S.D. Salunke, S.G. Shirodkar and T.K. Chondhekar, J. Indian
Chem. Soc., 79, 1 (2002).
CoL1
MnL1
CdL1
11. P.S. Mane, S.M. Salunke, B.S. More and Chondhekar, Asian J. Chem.,
24, 2235 (2012).
12. P.S. Mane, S.M. Salunke and B.S. More, E-J. Chem., 8(s1), S245 (2011);
https://doi.org/10.1155/2011/763915.
6
a
b
NA = Not applicable. Zone of inhibition in m
1
3. T. Roisnel and J.R. Carvajal, WinPLOTR, A Graphic Toolfor Powder
Diffraction, Laboratoire Leon Brillouin (CEA/CNRS), Cedex France
Conclusion
(
2004).
From the analytical data, composition of Schiff base ligand
and its metal complexes was determined. Structure of ligand
was confirmed by its H NMR and IR spectra and its metal
1
4. D.P. Shomaker and C.W. Garland, Experiment in Physical Chemistry,
McGraw-Hill International Edition, New York, edn 5 (1989).
15. A.S.Munde, V.A. Shelke, S.M. Jadhav, A.S. Kirdant, S.R. Vaidya, S.G.
1
Shankarwar, T.K. Chondhekar, Adv. Appl. Sci. Res., 3, 178 (2012).
complexes was confirmed from electronic, IR, XRD, TGA-
DTA spectra and their magnetic moment values. The DHA
Schiff base and its metal complexes were showed strong
antifungal activity than antibacterial activity. Cobalt, copper
and manganese complexes were among the stronger inhibitors
of growth and least growth inhibitory activity was showed by
iron and cadmium complexes against biological species.
1
1
6. D.C. Dash and A.K. Panda, J. Indian Chem. Soc., 79, 48 (2002).
7. A.S. Munde, J. Korean Chem. Soc., 53, 407 (2009);
https://doi.org/10.5012/jkcs.2009.53.4.407.
8. S.M. Jadhav, V.A. Shelke, S.G. Shankarwar, A.S. Munde and T.K.
Chondhekar, J. Saudi Chem. Soc., 18, 27 (2014);
https://doi.org/10.1016/j.jscs.2011.05.010.
9. S. Saini, R. Pal, A.K. Gupta and V. Beniwal, Der Pharma Chemica, 6,
330 (2014).
1
1
2
0. S. Saini, R. Pal, A.K. Gupta and V. Beniwal, World J. Pharm. Pharm. Sci.,
3, 1621 (2014).
ACKNOWLEDGEMENTS
The authors express their sincere thanks to UGC (WRO)
th
for the award of TRF under UGC 11 plan period. The authors