Synthesis and fungitoxic activity of 5-aryl-1-formyl-4,5-dihydro-3-(2- hydroxyphenyl)-1H-pyrazoles and their complexes

Article abstract of DOI:10.1002/(SICI)1526-4998(200003)56:3<284::AID-PS128>3.0.CO;2-M

Cyclization of 3-aryl-1-(2-hydroxyphenyl)prop-2-en-1-ones with hydrazine hydrate in refluxing formic acid afforded the title ligands, 5-aryl-1-formyl- 4,5-dihydro-3-(2-hydroxyphenyl)1H-pyrazoles (HL¹-HL⁴, Ar=Ph, 4-CH₃O- G<

Full text of DOI:10.1002/(SICI)1526-4998(200003)56:3<284::AID-PS128>3.0.CO;2-M

Pest Management Science
Pest Manag Sci 56:284±288 (2000)
Synthesis and fungitoxic activity of 5-aryl-1-
formyl-4,5-dihydro-3-(2-hydroxyphenyl)-1H-
pyrazoles and their complexes
Nisha Singh, Naresh K Sangwan* and Kuldip S Dhindsa
Department of Chemistry, CCS Haryana Agricultural University, Hisar - 125 004, India
Abstract: Cyclization of 3-aryl-1-(2-hydroxyphenyl)prop-2-en-1-ones with hydrazine hydrate in
re¯uxing formic acid afforded the title ligands, 5-aryl-1-formyl-4,5-dihydro-3-(2-hydroxyphenyl)-
1H-pyrazoles (HL1±HL4, Ar=Ph, 4-CH3O-C6H4-, 2-furyl, 2-thienyl). Reaction of HL1±HL4 with the
divalent metal ions, Mn2‡, Co2‡, Ni2‡, Cu2‡, and Zn2‡, afforded novel complexes of the type [ML2]
(M=metal ion; L=deprotonated ligand) which were characterized by elemental analyses, molecular
weight determinations, molar conductances, magnetic moments and electronic and infrared spectral
data. The ligands behaved as tridentate, coordinating through the phenolic oxygen after deprotona-
tion, N-2 of the pyrazole ring and oxygen of the 1-formyl group. The ligands and their complexes were
evaluated for growth-inhibiting activity against four phytopathogenic fungi. Macrophomina phaseoli
was generally most sensitive followed by Alternaria alternata and Colletotrichum falcatum while
Fusarium oxysporum was least sensitive to the tested compounds. The ligand HL1 and its complexes
showed the best activity against the fungi tested.
# 2000 Society of Chemical Industry
1
INTRODUCTION
en-1-one (4) (Fig 1) were available from our earlier
studies.17 All other chemicals were procured from
commercial suppliers. The solvents were distilled prior
to use.
Hydrazones and acid hydrazides have been frequently
used as useful ligands for complexation with transition
metal ions and several of these complexes with useful
biological activities have been studied extensively.1±5
The substituted 1-acyl-4,5-dihydro-1H-pyrazoles pos-
sess structural features of both hydrazones and acid
hydrazides in a rigid cyclic framework which can
provide the added advantage of certain restricted
conformations suitable for complexation. Moreover,
these pyrazoles have been reported as showing
enzyme-inhibiting,6 pharmacological,7 molluscicidal,8
antibacterial,9 antifungal,10 insecticidal,11±13 herbici-
dal,14 herbicide safener15 and antifertility activities.16
Recently, we have reported17 improved antifungal
activity of 4,5-dihydropyrazoles as a consequence of
their coordination with transition metal ions. Con-
tinuing these studies and our interest in development
of newer pesticides,18,19 we report herein the synthesis
of 5-aryl-1-formyl-4,5-dihydro-3-(2-hydroxyphenyl)-
1H-pyrazoles, their coordination with transition metal
ions and the effect of such complexation on in vitro
mycelial growth-inhibitory activity against some eco-
nomically important phytopathogenic fungal pests.
2.2 Synthesis of ligands
The 5-aryl-1-formyl-4,5-dihydro-3-(2-hydroxyphe-
nyl)-1H-pyrazole ligands (HL1±HL4), were synthe-
sized by re¯uxing a mixture of the appropriate
propenone 1±4 (0.1 mole) and hydrazine hydrate
(2ml, excess) in formic acid (50ml) for 20h. The
reaction mixture was cooled and poured onto ice-
water with stirring. The separated solid was ®ltered,
washed with water and crystallized from methanol to
give the corresponding ligands HL1±HL4 in 74±87%
yield. The synthesis is outlined in Fig 1.
2
MATERIALS AND METHODS
2.1 General
1-(2-Hydroxyphenyl)-3-phenylprop-2-en-1-one, (1),
1-(2-hydroxyphenyl)-3-(4-methoxyphenyl)prop-2-en-
1-one (2), 3-furyl-1-(2-hydroxyphenyl)prop-2-en-1-
one (3) and 1-(2-hydroxyphenyl)-3-(thienyl)prop-2-
Figure 1. Synthesis of ligands.
* Correspondence to: Naresh K Sangwan, Department of Chemistry, CCS Haryana Agricultural University, Hisar - 125 004, India
(Received 18 January 1999; revised version received 10 October 1999; accepted 5 November 1999)
# 2000 Society of Chemical Industry. Pest Manag Sci 1526±498X/2000/$17.50
284

Fungitoxic activity of substituted pyrazoles and their complexes
2.3 Synthesis of complexes
2.5.4 Growth-inhibitory activity
A solution of metalII chloride (0.01 mole) in a
minimum amount of ethanol was added slowly at
ambient temperature to an alkaline solution (pH
adjusted between 8 and 10 by adding few drops of
saturated aqueous sodium hydroxide solution) of the
corresponding ligand (0.02 mole) in ethanol (50ml)
with stirring. The reaction mixture was re¯uxed for 2h
during which a solid was precipitated. The reaction
mixture was cooled, the separated solid ®ltered off,
washed successively with water and ethanol and dried
under vacuum to give the complex in 51±65% yield.
For determination of in vitro fungicidal activity,
loopfuls of the test organisms from the slants were
introduced aseptically into sterilized conical ¯asks
containing 100ml of Czapek's Dox broths. The ¯asks
were incubated with intermittent shaking at
28(Æ1)°C for 24h. The inoculated broths were used
as such for testing the growth-inhibitory activity of the
test compounds by a two-fold serial-dilution tech-
nique.20 For this purpose, 1.8ml of the inoculated
broth was taken in a test tube and 0.2ml of the stock
solution of the test compound was added to it to form
the ®rst dilution. This solution (1ml) was diluted
further with the inoculated broth (1ml) to produce the
second dilution. The process was repeated to give a set
of eight dilutions containing test compound concen-
trations of 100, 50, 25, 12.5, 6.25, 3.13, 1.56 and
0.78mg litre 1. A set of tubes containing the
inoculated broths with equivalent quantity of DMSO
was kept as control. Each test was replicated twice.
The tubes were incubated for 72h at 28(Æ1)°C.
Results are reported as minimum inhibitory concen-
tration limits (MIC, mg litre 1), ie the minimum
concentration of the compound where no growth of
the mycelia could be observed.
2.4 Physicochemical measurements
The melting points were determined in open capil-
laries in a sulfuric acid bath and are uncorrected.
[1H]NMR spectra were recorded on a Bruker AC
300F instrument (300MHz) in deuterochloroform
using trimethylsilane as internal reference. Infrared
spectra were recorded on a Perkin Elmer spectro-
1
photometer, model 621 in the range 4000±200cm
using potassium bromide pellets. Electronic spectra of
the metal complexes were recorded on a Beckmann
DU-64 spectrophotometer in dimethylsulfoxide
(DMSO). Conductance measurements were made
3
on freshly prepared 1Â10 M solutions in dry DMSO
at 25°C using a Digital Conductivity Meter, model
NDS-732. All ligands and complexes were analysed
forC, H and N on a Carlo Erba Strumentazion
automatic elemental analyser, model 1106. Metal
contents were determined on a Varian Techtron
atomic absorption spectrophotometer, model AA
120. Molecular masses of the complexes were deter-
mined by the cryoscopic method in dry DMSO.
Magnetic susceptibility was determined at 25(Æ1)°C
using a magnetic susceptibility balance (Sherwood
Scienti®c, England).
3
RESULTS AND DISCUSSION
3.1 Chemistry
3.1.1 Characterization of ligands
The ligands displayed characteristic IR and [1H]NMR
spectra. The two protons at C4, which were adjacent to
a chiral center at C5, showed magnetic non-equiva-
lence and, therefore, appeared at different chemical
shifts. These protons were assigned in the [
1H]NMR
spectra on the basis of their characteristic chemical
shifts rather than coupling constants21 which are
known to be in¯uenced by the nature of the N-1
substituent.22 The proton at C4 resonating up®eld (d
3.33±3.63) was assigned trans to C5-H and that
resonating down®eld (d 3.75±3.90) was assigned cis
to C5-H. The coupling constant J4,5-trans was found to
be 4±5Hz, whereas, J4,5-cis was 11±12Hz. These
values of the coupling constants are in agreement with
those described earlier.21,22 The proton at C5 ap-
peared at d 5.46±5.83. The structures were further
supported by elemental analysis data. The character-
ization, analytical and [1H]NMR spectral data of the
ligands HL1±HL4 are given in Table 1.
2.5 Bioassay
2.5.1 Test solutions
Stock solutions of the compounds (1mg ml 1) were
prepared in DMSO and stored in a refrigerator until
needed.
2.5.2 Standard fungicide
The commercial fungicide carbendazim was used as a
standard for comparing the activity of the test
1
compounds. It was used as a commercial 500g kg
WP (Bavistin, BASF).
3.1.2 Characterization of complexes
The complexes were characterized on the basis of their
elemental analyses, molecular mass determinations,
molar conductances, magnetic moments, infrared and
electronic spectral data.
2.5.3 Test organisms
The phytopathogenic fungi Alternaria alternata (Fr)
Keissler from radish siliqua, Coletotricum falcatum
Went from sugar cane, Fusarium oxysporum Schlecht
emend Snyd and Hans f sp ciceri (Padwick) Snyd and
Hans from chick pea and Macrophomina phaseoli
(Maubl) Ashby from green gram were maintained on
Czapek's Dox Agar Slants at 5(Æ1)°C.
The complexes were stable under atmospheric
conditions, decomposed only on heating and were
insoluble in most of the common organic solvents
except polar solvents such as DMSO and nitroben-
zene. The low molar conductance values (0.40±19.50,
Pest Manag Sci 56:284±288 (2000)
285

N Singh, NK Sangwan, KS Dhindsa
Table 1. Characterization, analytical and [1H]NMR spectral data of 5-aryl-1-formyl-4,5-dihydro-3-(2-hydroxyphenyl)-IH-pyrazoles
Analysis (%): found (calcd)
Mp
Compd (°C)
Yield
(%)
Mol formula
(Mol mass)
C
H
N
[1H]NMR (CDCl3, dppm)
HL1
HL2
HL3
HL4
151
168
170
120
74
87
76
79
C16H14N2O2 (266.3)
C17H16N2O3 (296.3)
C14H12N2O3 (256.3)
72.3 (72.2) 5.5 (5.3) 10.7 (10.5) 3.33 (dd, 1H, trans C4-H, J =5 and 18Hz), 3.90 (dd, 1H, cis C4-H, J =11 and 18Hz),
5.50 (dd, 1H, C5-H, J =5 and 11Hz), 6.93±7.95 (m, 9H, aromatic H), 8.91 (s, 1H,
CHO), 10.12 (s, 1H, OH, D2O exchangeable).
68.7 (68.9) 5.5 (5.4)
9.4 (9.5)
3.34 (dd, 1H, trans C4-H, J =5 and 18Hz), 3.78 (d, 3H, OCH3), 3.88 (dd, 1H, cis C4-
H, J =12 and 18Hz), 5.46 (dd, 1H, C5-H, J =5 and 12Hz), 6.85±7.40 (m, 8H,
aromatic H), 8.90 (s, 1H, CHO), 10.14 (s, 1H, OH, D2O exchangeable).
65.6 (65.6) 4.6 (4.7) 10.9 (10.9) 3.63 (dd, 1H, trans C4-H, J =5 and 18Hz), 3.75 (dd, 1H, cis C4-H, J =11 and 18Hz),
5.62 (dd, 1H, C5-H, J =5 and 11Hz), 6.34±7.78 (m, 7H, aromatic H), 8.86 (s, 1H,
CHO), 10.05 (s, 1H, OH, D2O exchangeable).
C14H12N2O2S (272.3) 61.2 (61.7) 4.3 (4.4) 10.0 (10.3) 3.53 (dd, 1H, trans C4-H, J =4 and 18Hz), 3.88 (dd, 1H, cis C4-H, J =11 and 18Hz),
5.83 (dd, 1H, C5-H, J =4 and 11Hz), 6.93±7.42 (m, 7H, aromatic H), 8.88 (s, 1H,
CHO), 10.05 (s, 1H, OH, D2O exchangeable).
ohm 1cm2mol 1) of the complexes in dry DMSO at
25°C indicated their non-electrolytic nature. The
results of elemental analyses and molecular mass
determinations (Table 2) indicated 1:2 metal:ligand
stoichiometry in the complexes with the general
formula [ML2] where L is the appropriate deproto-
nated ligand HL1±HL4 and M is MnII, CoII, NiII, CuII
and ZnII.
3.1.2.2 Magnetic moments and electronic spectra. The
effective magnetic moment (meff) values of the com-
plexes calculated from the corrected magnetic sus-
ceptibilities are presented in Table 2. Those of the
MnII complexes were found to be in the range of 5.87±
6.12 BM which are characteristic of high-spin MnII
complexes. The electronic spectra of the complexes
showed weak absorption bands in the regions 18520±
19350, 21460±22321, 24681±25542 and 28060±
3.1.2.1 Infrared spectra. All the ligands23 and com-
plexes24 displayed characteristic IR absorptions which
support the coordination of the ligand through the
phenolic oxygen after deprotonation and N-2 of the
pyrazole ring. In addition, a negative shift (20±
30cm 1) for the carbonyl group indicated the parti-
cipation of this group in coordination.25 The furan and
thiophene ring stretching vibrations remained unal-
tered in the spectra of the complexes of the ligands
HL3 and HL4 respectively, suggesting non-participa-
tion of their oxygen and sulfur in the coordination.
The participation of N-2, the phenolic oxygen after
deprotonation and the carbonyl group was also
supported by the appearance of new absorption bands
1
6
6
28927cm
assigned to A1g
→
→
4T1g(G), A1g
→
6
6
4T2g(G), A1g
4Eg(G) and A1g
→
4T2g(D)
transitions, respectively, suggesting a distorted octa-
hedral geometry for the MnII complexes.27
The CoII complexes displayed magnetic moments in
the range of 4.89±5.35 BM which indicates the
presence of three unpaired electrons with signi®cant
orbital contribution and a high spin octahedral
stereochemistry.27 The electronic spectra of the
complexes exhibited three bands in the regions
1
8520±8950, 17560±17980 and 21620±22130cm
4
4
which were assigned to T1g(F) → T2g(F) (n1),
4T1g(F) → A2g(F) (n2) and T1g(F) → T1g(P) (n3)
transitions, respectively. The appearance of these
bands, energy ratio n2/n1 of the complexes (2.01±
4
4
4
1
in the far-IR region at 500±460 and 440±400cm
assigned to n(M-O) and n(M-N), respectively.26
Table 2. Analytical data and magnetic moment values of the metal complexes of 5-aryl-1-formyl-4,5-dihydro-3-(2-hydroxyphenyl)-1H-pyrazoles
Analysis (%): found (calcd)
Molecular
formula
Melting/Decomp.
Yield
(%)
Mol mass
meff.
(BM)
Complex
(D) point (°C)
Found (Calcd)
C
H
N
Metal
[Mn(L1)2]
[Mn(L2)2]
[Mn(L3)2]
[Mn(L4)2]
[Co(L1)2]
[Co(L2)2]
[Co(L3)2]
[Co(L4)2]
[Ni(L1)2]
[Ni(L2)2]
[Ni(L3)2]
[Ni(L4)2]
[Cu(L1)2]
[Cu(L2)2]
[Cu(L3)2]
[Cu(L4)2]
[Zn(L1)2]
[Zn(L2)2]
[Zn(L3)2]
[Zn(L4)2]
C32H26MnN4O4
C34H30MnN4O6
C28H22MnN4O6
C28H22MnN4O4S2
C32H26CoN4O4
C34H30CoN4O6
C28H22CoN4O6
C28H22CoN4O4S2
C32H26NiN4O4
C34H30NiN4O6
C28H22NiN4O6
C28H22NiN4O4S2
C32H26CuN4O4
C34H30CuN4O6
C28H22CuN4O6
C28H22CuN4O4S2
C32H26ZnN4O4
C34H30ZnN4O6
C28H22ZnN4O6
C28H22ZnN4O4S2
> 220
165 (D)
190
55
55
54
55
55
55
55
55
52
51
52
52
55
55
55
55
52
52
56
56
608 (585.5)
660 (645.6)
580 (565.4)
620 (597.6)
617 (589.5)
675 (649.6)
590 (569.4)
626 (601.6)
605 (589.3)
674 (649.3)
585 (569.2)
627 (601.3)
615 (594.1)
678 (654.2)
588 (574.1)
620 (606.2)
623 (596.0)
681 (656.0)
600 (575.9)
633 (608.0)
66.1 (65.6)
62.9 (63.3)
60.0 (59.5)
55.9 (56.3)
65.7 (65.2)
63.4 (62.9)
59.3 (59.1)
56.4 (55.9)
65.6 (65.2)
62.6 (62.9)
59.5 (59.1)
56.4 (55.9)
64.4 (64.7)
62.0 (62.4)
59.1 (58.6)
56.9 (55.5)
65.0 (64.5)
62.0 (62.3)
58.7 (58.4)
55.6 (55.3)
4.3 (4.5)
5.1 (4.7)
3.8 (3.9)
4.6 (3.7)
4.3 (4.4)
5.1 (4.7)
3.8 (3.9)
4.1 (3.7)
4.2 (4.4)
5.0 (4.7)
4.0 (3.9)
4.1 (3.7)
4.8 (4.4)
5.0 (4.6)
3.7 (3.9)
4.1 (3.7)
4.7 (4.4)
5.0 (4.6)
3.7 (3.9)
4.1 (3.6)
10.0 (9.6)
9.2 (8.7)
10.4 (9.9)
10.3 (9.4)
10.0 (9.5)
9.1 (8.6)
9.4 (9.8)
9.2 (9.3)
9.9 (9.5)
9.0 (8.6)
10.3 (9.8)
9.0 (9.3)
9.2 (9.4)
9.0 (8.6)
10.2 (9.8)
9.4 (9.2)
9.9 (9.4)
9.0 (8.5)
9.9 (9.7)
9.7 (9.2)
9.9 (9.4)
9.0 (8.5)
6.10
5.87
5.99
6.12
5.15
5.20
5.35
4.89
3.00
3.33
3.09
3.20
2.11
2.12
1.92
1.96
±
10.1 (9.7)
9.3 (9.2)
140 (D)
> 220
175 (D)
> 220
140
9.6 (10.0)
8.7 (9.1)
10.4 (10.3)
10.3 (9.8)
10.4 (10.0)
9.5 (9.0)
> 220
170 (D)
> 220
> 220
> 220
> 220
190
10.6 (10.3)
10.2 (9.8)
11.2 (10.7)
9.6 (9.7)
11.5 (11.1)
10.8 (10.5)
11.2 (11.0)
10.5 (10.0)
11.3 (11.4)
11.2 (10.8)
> 220
220 (D)
150 (D)
> 220
124 (D)
±
±
±
286
Pest Manag Sci 56:284±288 (2000)

Fungitoxic activity of substituted pyrazoles and their complexes
2.06),28 nephelauxetic ratio (0.910±0.935), 10Dq
Teller distortion.32 The electronic spectra displayed a
broad band in the region 15500±16000cm 1 pertain-
ing to the 2Eg → 2T2g transition, suggesting a distorted
octahedral con®guration for the complexes. The
possibility of a tetrahedral structure33 was excluded
by the absence of any band below 10000cm 1. The
observed values of 10Dq (15500±16000cm 1) and
LFSE (111.24±114.83kJ mol 1) supported the pro-
posed geometry.
The ZnII complexes were diamagnetic. On the basis
of their elemental analyses, infrared spectra, molecular
weight determinations and molar conductance studies
octahedral structures have been proposed for these
ZnII complexes.34
1
(9030±9060cm 1) and LFSE (86.41±86.69kJ mol
were all in agreement with an octahedral con®guration
)
around CoII. The Racah interelectronic repulsion
1
parameter `B' was found to be less (884±908cm
)
than the free ion value (971cm 1), suggesting a weak
covalent character of the metal±ligand bond.29
The effective magnetic moment values of 3.00±3.33
BM for the NiII complexes suggested octahedral
geometry around NiII which was further supported
by the electronic spectra where three bands in the
regions 10050±10240, 15600±15825 and 24420±
1
24660cm were observed. These were assigned to
3
3
3
3A2g(F) → T2g(F) (n1), A2g(F) → T1g(F) (n2) and
3A2g(F) → T1g(P) (n3) transitions, respectively. The
3
various ligand ®eld parameters, such as 10Dq, B, b
and LFSE, for the NiII complexes were found to be in
the range 10050±10240cm 1, 651±658cm 1, 0.625±
0.631 and 144.26±146.98kJ mol 1, respectively. The
energy ratio n2/n1 for the complexes was within the
range of 1.52±1.56 as required for octahedral com-
plexes.30 The Racah interelectronic repulsion par-
ameter `B' (651±658cm 1) value was less than the free
ion value because of decreased interelectronic repul-
sion resulting from electron delocalization.31
The magnetic moment of the CuII complexes was
observed in the range of 1.92±2.12 BM which
corresponds to a single unpaired electron with
signi®cant orbital contribution. The increase from
the spin-only value (1.73 BM) might be due to Jahn±
3.2 Fungicidal activity
The growth-inhibitory activity in vitro of the ligands
(HL1±HL4) and their metal complexes against four
test fungi are shown in Table 3, with data for
carbendazim included for comparison.
The data indicate no clear trends with respect to the
in¯uence of coordination on fungitoxicity and little or
no activity against F oxysporum in any case. The HL1
ligand and its complexes gave the most promising
results with the other three fungi and M phaseoli
tended to be the most sensitive fungus to both ligands
and complexes.
Although no ligand or complex showed activity
comparable to that of carbendazim, nevertheless some
Minimum inhibitory concentration (mg litre 1) against
Ligand
Complex with a A alternata C falcatum F oxysporum M phaseoli
HL1
None
MnII
CoII
NiII
25
6.25
>100
12.5
25
12.5
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
3.13
6.25
6.25
6.25
3.13
12.5
3.13
50
12.5
25
CuII
ZnII
6.25
25
50
25
50
HL2
HL3
HL4
None
MnII
CoII
NiII
CuII
ZnII
50
50
50
50
50
6.25
3.13
50
50
100
50
100
50
>100
<3.13
100
100
100
<3.13
25
None
MnII
CoII
NiII
CuII
ZnII
100
100
100
25
100
50
50
25
25
25
100
50
100
100
25
100
50
None
MnII
CoII
NiII
CuII
ZnII
25
6.25
50
100
50
100
25
12.5
6.25
50
50
50
50
50
Carbendazimb
None
0.78
1.56
3.13
0.78
a
Complexes were of the type [ML2] where M is metal ion and L is deprotanated ligand.
b Included for comparison.
Table 3. Activities in vitro of the ligands and
their metal complexes against four test fungi
Pest Manag Sci 56:284±288 (2000)
287

N Singh, NK Sangwan, KS Dhindsa
16 Sangwan NK and Rastogi SN, Studies in antifertility agents: Part
XXXII ±Synthesis and stereochemistry of 3,3a-trans and cis-
2(H)-acetyl-3-aryl-3,3a-dihydropyrazolo[4,3-c][2H]chromenes,
pyrazolo[3,4-a]benzocycloalk-1-enes and 3,3a-trans and cis-
2(H)-acetyl-3-aryl-8-methoxy-5-tosyl-3,3a,4,5-tetrahydropyr-
azolo[4,3-c]quinolines. Indian J Chem 20B:135±139 (1981).
17 Singh N, Sangwan NK and Dhindsa KS, Synthesis of novel
coordination compounds of 5-aryl-4,5-dihydro-3-(2-hydroxy-
phenyl)pyrazoles as potential fungicides. Synth React Inorg
Metal±Org Chem 29:673±685 (1999).
showed promising activity and could serve as lead
structures for future work.
ACKNOWLEDGEMENT
Instrumental facilities provided by Regional Sophisti-
cated Instrumentation Centre, Punjab University,
Chandigarh are acknowledged.
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