Synthesis, structural and fungicidal studies of hydrazone based coordination compounds

Article abstract of DOI:10.1016/j.saa.2012.11.012

The coordination compounds of the Co(II), Ni(II) and Cu(II) metal ions derived from imine based ligand, benzil bis(carbohydarzone) were structurally and pharmaceutically studied. The compounds have the general stoichiometry [M(L)]X₂ and [Co(L)X

Full text of DOI:10.1016/j.saa.2012.11.012

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 103 (2013) 96–100
Contents lists available at SciVerse ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Synthesis, structural and fungicidal studies of hydrazone based
coordination compounds
Amit Kumar Sharma a,b, Sulekh Chandra b,
⇑
a Department of Chemistry, Ramjas College, University of Delhi, University Enclave, Delhi 110 007, India
b Department of Chemistry, Zakir Husain College, University of Delhi, J.L. Nehru Marg, New Delhi 110 002, India
g r a p h i c a l a b s t r a c t
h i g h l i g h t s
"
"
Synthesis of hydrazone based imine.
Complexes of Co(II), Ni(II) and Cu(II)
with [M(L)X2] and [M(L)]X2
compositions.
"
Structural elucidation by the
Physicochemical and spectral
studies.
"
"
Fungicidal screening.
Activation of the pharmaceutical
action of the antipathogen by the
metal ions.
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 4 August 2012
Received in revised form 27 October 2012
Accepted 5 November 2012
Available online 16 November 2012
The coordination compounds of the Co(II), Ni(II) and Cu(II) metal ions derived from imine based ligand,
benzil bis(carbohydarzone) were structurally and pharmaceutically studied. The compounds have the
general stoichiometry [M(L)]X2 and [Co(L)X2], where M = Ni(II) and Cu(II), and X ¼ NOꢀ and Clꢀ ions.
3
The analytical techniques like elemental analyses, molar conductance measurements, magnetic suscep-
tibility measurements, IR, UV/Visible, NMR, ESI mass and EPR were used to study the compounds. The
key IR bands, i.e., amide I, amide II and amide III stretching vibrations accounts for the tetradentate metal
binding nature of the ligand. The electronic and EPR spectral results suggest the square planar Ni(II) and
Cu(II) complexes (giso = 2.11–2.22) and tetragonal geometry Co(II) complexes (giso = 2.10–2.17). To
explore the compounds in the biological field, they were examined against the opportunistic pathogens,
i.e., Alternaria brassicae, Aspergillus niger and Fusarium oxysporum. The partial covalent character of metal-
ligand bond is supported by the orbital reduction factor k (0.62–0.92) and nephalauxetic parameter b
(0.55–0.57).
Keywords:
Schiff’s base
Coordination compounds
Tetragonal and square planar geometries
Biological investigations
Ó 2012 Elsevier B.V. All rights reserved.
Introduction
ified to improve its properties. Consequently, the advance synthet-
ical and separation methodologies and biochemical techniques are
The mechanisms of DNA replication and protein synthesis in
fungi are similar to the mammalian cell. Consequently, it is a chal-
lenge to the Biochemists for designing the drugs that are selec-
tively toxic to fungal cells but not to the human host [1]. When a
compound is found to be biologically active, it is chemically mod-
followed for designing of the drug.
Imines constitute one of the most interesting and widely used
families of the hydrazones. The interaction of imines and modified
imines with the transition metal ions as well as lanthanides is
worth a great interest due to synthetical and applicative causes
in array of pharmaceutical, analytical, biochemistry, etc. Further,
the endogenous availability of metal ions and strict regulation of
their intracellular concentration have stimulated the synthesis of
metal-based drugs. A number of drugs do not show purely mode
⇑
Corresponding author. Tel.: +91 11 22911267; fax: +91 11 23215906.
E-mail addresses: sharmaamitk@yahoo.co.in (A.K. Sharma), schandra_00@
yahoo.com (S. Chandra).
1386-1425/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.saa.2012.11.012

A.K. Sharma, S. Chandra / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 103 (2013) 96–100
97
of pharmaceutical action, they are activated by the metal ions [2–
4].
in the test plate to the respective control plate. DMSO and captain
were employed as a control and a standard fungicide, respectively.
Preceding our work in the coordination and biological research,
we report here the synthesis, structural and biological studies of
the hydrazone based imine and transition metal complexes de-
rived from it.
Results and discussion
The hydrazone based Schiff’s base ligand L was obtained in good
yield by reacting benzil and carbohydrazide in 1:2 ratio (Supple-
mentary material). The complexes with Cu(II), Ni(II) and Co(II) me-
tal ions were also obtained in the satisfactory yield on reaction of
the ligand with metal salts.
Experimental
Materials and measurements
Metal salts and chemicals (Fluka, S.D. Fine, E. Merck and Tho-
mas Backer) were commercial products and were used as supplied.
Benzil and carbohydrazide (AR grade) were obtained from Sigma-
Aldrich. NMR spectra were recorded with a model Bruker advance
DPX-300 spectrometer operating at 300 MHz using DMSO-d6 as a
solvent and TMS as an internal standard. ESI mass spectrum was
recorded on a model Q Star XL LCMS–MS system. The stoichiome-
tric analyses were carried out on a Carlo-Erba 1106 analyser. IR
spectra were recorded as KBr and CsI2 pellets in the region 4000–
200 cmꢀ1 on a FT-IR spectrum BX-II spectrophotometer. The elec-
tronic spectra were recorded on Shimadzu UV mini-1240 spectro-
photometer. EPR spectra were recorded for solids and solutions on
an E4-EPR spectrometer at room temperature and liquid nitrogen
temperature operating at X-band region using DPPH as a standard.
The molar conductance of complexes was measured in DMSO at
room temperature on an ELICO (CM 82T) conductivity bridge.
The magnetic susceptibility was measured at room temperature
on a Gouy balance using CuSO4ꢁ5H2O as calibrant.
Physical properties
The complexes are insoluble in the nonpolar solvents but solu-
ble in the polar solvents like DMSO. The elemental, molar conduc-
tivities studies of the complexes suggest the [M(L)]X2 and [Co(L)X2]
compositions, where M = Ni(II) and Cu(II), and X ¼ NOꢀ3 and Clꢀ [6].
The analytical data of ligand and its complexes with their physical
properties are given in Table 1 in supporting information, which
indicates 1:1:2 metal:ligand:anion stoichiometry for all the com-
plexes. Measured values of magnetic moments indicate that the
nickel(II) complexes are diamagnetic whereas the copper(II) and
cobalt(II) complexes are paramagnetic having the magnetic mo-
ments 1.86–1.93 and 4.80–4.92 BM respectively.
IR spectra
The important IR bands of the compounds along with their
assignment are given in Table 2. The IR spectrum of the free ligand
displays the bands at 3420 and 3317 cmꢀ1 corresponding to the
Synthesis of ligand, benzil bis(carbohydrazone), (L)
mas(NH2) and ms(NH2) stretching vibrations, respectively, which
suggests the presence of free NH2 groups in the ligand. The spec-
trum exhibits the bands at 1686, 1620 and 1509 cmꢀ1 correspond-
ing to the amide I, amide II and amide III stretching vibrations,
respectively, due to the presence of the amide groups in the ligand
[7]. On complex formation, the position of these bands is altered,
which indicates that the ligand coordinates to the metal ion
through the amide oxygen and azomethine nitrogen atoms. This
NO binding of the ligand is also supported by the appearance of
A solution of carbohydrazide (1.8018 g, 0.02 mol) in water
(15 mL) was heated for 15 min in presence of few drops of acetic
acid and then was added to a hot solution of benzil (2.1023 g,
0.01 mol) in ethanol (15 mL). The reaction mixture was refluxed
for 2 h at 65 °C, allowed to stay at room temperature and then kept
in refrigerator overnight. The white product was precipitated out,
which was filtered off, washed several times with ethanol and
dried under vacuum over P4O10. Yield 80%, m.p. 206 °C. Elemental
analyses, Found (Calcd.) For C16H18N8O2: C, 54.29 (54.24); H, 5.12
(5.08); N, 31.70 (31.64)%. 1H NMR (300 MHz, DMSO-d6): d (ppm):
4.29 (S, 4H, 2 NH2), 9.68 (S, 4H, 4NH), 7.15–7.95 (m, 10H, 2Ph);
13C NMR (300 MHz, DMSO-d6): d (ppm): 125.98–135.54 (m, 12C,
2 Ph), 151.09 and 151.27 (2C, AC@NA), 160.22 and 161.20 (2C,
AC@ONHA).
new IR bands at 405–428 and 500–529 cmꢀ1 due to
(MAO) vibrations, respectively [8,9]. This discussion reveals that
m(MAN) and
m
the Schiff base ligand coordinates to metal ions as tetradentate
chelate to give the complexes.
Mass spectrum
ESI mass spectrum was recorded on a LCMS–MS system. The
mass spectrum of the ligand gives the peak at m/z = 354 due to
molecular ion (M+). The weak peaks at m/z = 355 and 356, are also
observed in the spectrum which are due to the (M + 1)+ and
(M + 2)+ isotopes. The maximum intensity peak (base peak, 100%
intensity) is observed at m/z = 77 is due to the phenyl cation and
another intense peak at m/z = 177 is also appeared in the spectrum
due to the six membered cyclic positive ion (C8H9N4O+), which is
Synthesis of the complexes
A hot solution of metal salt (nitrate or chloride) (1 mmol) in
ethanol (10 mL) was added slowly to a hot solution of ligand
(1 mmol) in ethanol (15 mL) with constant stirring. The mixture
was refluxed for 8–10 h at 80–85 °C. On keeping the resulting mix-
ture overnight at 0 °C, the colored product was separated out,
which was filtered off, washed with ethanol and dried under vac-
plausibly the resultant of the cd CAC bond cleavage and followed
uum over P4O10
.
by cyclization. The other structural units present in the ligand gives
peaks at various mass numbers with variable intensity like at m/
z = 59 due to amide group and 41, 118, 295, etc. corresponding to
the different fragments (Supplementary material) [10].
Biological screening
The Food Poison Technique was employed to examine the syn-
thesized compounds against the fungi, i.e. Alternaria brassicae,
Aspergillus niger and Fusarium oxysporum for their fungicidal inves-
tigations [5]. The stock solutions of the compounds were prepared
in DMSO solvent. The fungicidal capacity of the compounds was
determined in percentage terms from the growth of the fungus
Electronic spectra
The UV/Visible spectra of complexes were recorded in DMSO
solvent. The data of electronic spectra are summarized in Table 3.

98
A.K. Sharma, S. Chandra / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 103 (2013) 96–100
Table 1
Microanalytical data of complexes with their physical properties.
S. no.
Complex
Color
m.p. (°C)
Molar conductance
ꢀ1 cm2 molꢀ1
Yield (%)
Microanalytical data (%) calcd. (found)
(
X
)
M
C
H
N
1
2
3
4
5
6
[Cu(L)]Cl2
CuC16H18N8O2Cl2
Green
Brown
Orange
Brown
Brown
Brown
216
162
230
>300
188
230*
130
120
128
140
11
68
60
65
70
62
64
12.99
(13.04)
39.30
(39.35)
3.68
(3.72)
22.93
(22.98)
[Cu(L)](NO3)2
CuC16H18N10O8
11.73
(11.78)
35.46
(35.50)
3.32
(3.37)
25.85
(25.89)
[Ni(L)]Cl2
NiC16H18N8O2Cl2
12.14
(12.19)
39.69
(39.75)
3.72
(3.76)
23.15
(23.20)
[Ni(L)](NO3)2
NiC16H18N10O8
10.94
(10.99)
35.77
(35.82)
3.35
(3.40)
26.08
(26.14)
[Co(L)Cl2]
CoC16H18N8O2Cl2
12.17
(12.22)
39.68
(39.74)
3.72
(3.76)
23.14
(23.18)
[Co(L)(NO3)2]
14
10.97
35.76
3.35
26.08
CoC16H18N10O8
(10.92)
(35.81)
(3.39)
(26.14)
*
Decomposition temperature.
Table 2
(a)
(b)
Comparative IR data of compounds.
Compound
Amide I
Amide II
Amide III
m
(MAO)
m(MAN)
Ligand
[Cu(L)]Cl2
[Cu(L)](NO3)2
[Ni(L)]Cl2
[Ni(L)](NO3)2
[Co(L)Cl2]
1686
1617
1664
1664
1663
1719
1660
1620
1595
1595
1590
1609
1569
1590
1509
1444
1446
1542
1445
1446
1442
–
–
519
510
500
508
529
504
420
418
405
415
423
428
C
N
C
N
C
C
O
X
N
N
X2
HN
C
M
NH
HN
C
NH
Co
C
C
[Co(L)(NO3)2]
X
HN
O
O
N
H
HN
O
NH
H
2N
H2N
H
2N
NH2
The copper(II) complexes show the electronic spectral bands in
the region 11,248–11,547, 14,814–16,140 and 24,450–
Fig. 1. Structure of the complexes (a) [M(L)]X2 and (b) [Co(L)X2], where M = Cu(II)
and Ni(II), and X ¼ NOꢀ3 and Clꢀ.
25,360 cmꢀ1. These transitions may be assigned to the 2B1g 2A1g
2
ðdx2
ðdx2
dz2 Þm1
,
2B1g 2B2g ðdx2
dxyÞm2 and B1g 2Eg
ꢀy2
ꢀy2
ꢀy2
covalency factor b and ligand field stabilization energy (LFSE) have
been calculated for the Co(II) complexes. The values of B and Dq of
Co(II) complexes were calculated from the transition energy ratio
dxz; dyzÞm3 transitions, respectively [11–13]. The transi-
tions suggest the D4h symmetry and square planar geometry for
the complexes (Fig. 1a).
diagram using m3/m1 ratio. The value of b (0.55–0.57) for the Co(II)
complexes accounts for the covalent nature of the complexes [14].
The evaluated parameters are listed in Table 3.
The absorption spectra of nickel(II) complexes give the d-d tran-
sitions in the range 11,185–11,210, 22,883 and 30,864 cmꢀ1. The
lowest energy transition corresponds to the transition
1A1g ? 1A2g ðdxy ! dx2
Þ
m1 which suggest the energy levels order
ꢀy2
dz2 < dxy. The other transitions correspond to the 1A1g ? 1B1g
EPR spectra
ðdz2 ! dx2
Þ
m2 and intraligand band, respectively [11–13]. These
transitions reveal that the nickel(II) complexes possess square pla-
nar geometry (Fig. 1a).
ꢀy2
The EPR spectra of copper(II) and cobalt(II) complexes were re-
corded at room temperature as well as liquid nitrogen temperature
in polycrystalline form and DMSO frozen. The data are given in
Table 4.
The spectra of the Cu(II) complexes show only one signal (Sup-
plementary material) at giso = 2.11–2.22. The calculated values of g||
and g\ for the complexes at room temperature and liquid nitrogen
temperature show the order as g|| > g\ > 2.0023 which is consistent
The electronic spectra of cobalt(II) complexes display the d–d
transition bands in the region 10,341–10,649 and 18,621 cmꢀ1
.
These transitions may be assigned to the T1g (F) ? 4T2g (F)m1 and
4
4T1g (F) ? 4A2g (F)m2
,
respectively [11–13]. The band at
29325 cmꢀ1 is due intraligand transition. The transitions corre-
spond to the tetragonal geometry of the complexes (Fig. 1b).
The complexes exhibit the high energy bands in the range
33,003–36,900 cmꢀ1 which may be attributed to the charge trans-
fer transitions. The ligand field parameters like Racah inter-elec-
tronic repulsion parameter B, ligand field splitting energy Dq,
with the dx2
ground state [15–18]. The odd electron is located in
ꢀy2
the B1g antibonding orbital. The spectral studies reveal that the
Cu(II) ion in the present complexes is in square planar field. The
approximate antibonding wave functions are
Table 3
Electronic spectral data and Ligand field parameters of the complexes.
Complex
leff (BM)
kmax (cmꢀ1
)
Dq (cmꢀ1
)
B (cmꢀ1
)
b
LFSE (kJ molꢀ1
)
[Cu(L)]Cl2
[Cu(L)](NO3)2
[Ni(L)]Cl2
[Ni(L)](NO3)2
[Co(L)(NO3)2]
[Co(L)Cl2]
1.86
1.93
Dia.
Dia.
4.92
4.80
11,248, 14,814, 24,450, 36,496
11,547, 16,140, 25,360, 36,900
11,185, 22,883, 30,864, 35,714
11,210, 33,222
10,341, 18,621, 36,900
10,669, 18,621, 29,325, 33,003
–
–
–
–
1155
1241
–
–
–
–
642
620
–
–
–
–
0.57
0.55
–
–
–
–
110
118

A.K. Sharma, S. Chandra / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 103 (2013) 96–100
99
Table 4
EPR and bonding parameters of the complexes.
k?2
(RT)
k2jj
(RT)
k?2
(LNT)
k2jj
(LNT)
Complex
Medium g\
(RT)
g||
(RT)
giso
(RT)
g\
(LNT)
g||
(LNT)
giso
(LNT)
k
(RT)
k
G
(RT)
G
(LNT)
(LNT)
[Cu(L)]Cl2
[Cu(L)](NO3
[Co(L)Cl2]
Solid
DMSO
2.07
2.09
2.42
2.37
2.18
2.18
2.06
2.06
2.26
2.28
2.12
2.13
0.76
0.98
0.93
0.82
0.82
0.92
0.65
0.64
0.58
0.62
0.62
0.64
6.16
4.19
4.47
4.81
Solid
DMSO
2.05
2.06
2.29
2.37
2.13
2.22
2.05
2.06
2.27
2.24
2.12
2.11
0.73
0.88
0.70
0.90
0.72
0.89
0.73
0.88
0.65
0.58
0.70
0.78
6.03
6.37
5.61
4.12
Solid
DMSO
–
–
–
–
–
–
1.91
1.87
2.62
2.78
2.14
2.17
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
[Co(L)(NO3)2] Solid
DMSO
–
–
–
–
–
–
1.86
1.85
2.59
2.62
2.10
2.10
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
ðdx2 Þ ꢀ a0½ꢀrðx1Þ
þ
rðy2Þ
þ
ꢀ
rðx3Þ
ꢀ
rðy4Þꢂ=2
complexes. The spectral features correspond to the tetragonal sym-
metry around the Co(II) ion [15–18].
wB1g
¼
a
ꢀy2
wB2g ¼ bðdxyÞ ꢀ b0½pyð1Þ ꢀ pxð2Þ ꢀ pðy3Þ
wA1g
wE1g
wE1g
rðx4Þꢂ=2
¼
¼
¼
a1ðdz2 Þ ꢀ a01
½
rðx1Þ
þ
rðy2Þ
ꢀ
rðx3Þ
ꢀ
rðy4Þꢂ=2
Antimicrobial activities
pffiffiffi
2
c
ðdxzÞ ꢀ c0½pðz1Þ ꢀ pzð3Þꢂ=
pffiffiffi
2
The low lipophilicity is a typical problem because that leads to
poor permeability through membrane of organism. Several modifi-
cations like pharmacodynamics and pharmacokinetics lead the im-
proved lipophilicity of the drug through the target cell. Moreover,
the pharmaceutical action of the antipathogen is activated by the
metal ions. This improvement in the antipathogenic activity of li-
gand on complexation is based on the Overtone’s Concept and Che-
lation Theory. The polarity of the metal ion is reduced on
complexation by the partial sharing of its positive charge with le-
wis base, which causes the delocalization of the charge over the
whole ring. Consequently, the lipophilicity of the compound is im-
proved [19,20].
c
ðdyzÞ ꢀ c0½pðz2Þ ꢀ pzð4Þꢂ=
For the copper(II) ion in tetragonal field, the spin-Hamiltonian is
given by
H ¼ b½gjjHzSz þ g?ðHxSx þ HySyÞꢂ þ AIzSz þ BðIxSx þ IySyÞ
where b is the Bohr magneton. H is the applied magnetic field and
the last term in expression represents the ligand hyperfine term.
The geometric parameter G, is calculated by using the
expression:
4k2jj ꢁ
DExz
k2?DExy
Further, the biological activity of a drug is related to its affinity
for the receptor, i.e., the stability of the drug-receptor complex.
This stability is commonly measured its Kd, the dissociation con-
stant for the drug-receptor complex at equilibrium:
ðgjj ꢀ 2:0023Þ
ðg? ꢀ 2:0023Þ
G ¼
¼
The complexes show the G values greater than four (Table 4),
which indicate that the exchange interaction between the cop-
per(II) ions in the polycrystalline form is negligible. The EPR
parameters and the d–d transition energies are used to evaluate,
½drugꢂ½receptorꢂ
Kd
¼
½drug ꢀ receptor complexꢂ
the orbital reduction factor
k
by using the expression:
Smaller the Kd, the larger the concentration of the drug-receptor
k2 ¼ k2 þ 2k2 =3, where k|| and k\ are the parallel and perpendicu-
complex, the stable is that complex and the greater is the affinity of
the drug for the receptor. Solvated compound (drug) and solvated
proteins (receptor) generally exist as an equilibrium mixture of
several conformers each. The solvent molecules that occupy the
binding site of the receptor must be displaced by the drug to pro-
duce a solvated complex. The interactions between the drug and
the receptor are stronger than the interaction between the drug
and the receptor with solvent molecule. The noncovalent interac-
tions are generally weak. However, other several types of interac-
tions like electrostatic, dipole–dipole, hydrogen bonds,
hydrophobic, Charge transfer complexes, Van der Waals or London
jj
?
lar components of the orbital reduction factor. The low values of k
(0.62–0.92) indicate the partial covalent nature of the complexes
(Table 4) [15–18].
The X-band EPR spectra of the Co(II) complexes were recorded
at liquid nitrogen temperature in polycrystalline form and solution
form. Due to the fast spin-relaxation of high-spin cobalt(II) ion, the
signals are observed only at low temperature. The EPR spectra give
the one signal with giso = 2.10–2.17 (Table 4). The spectra of the
complexes do not display any hyperfine splitting. Because this
hyperfine splitting is resolved only in magnetically diluted Co(II)
Table 5
Fungicidal activity data of the compounds.
Compound
Fungal inhibition (%) (conc. in
l
g mLꢀ1
)
A. brassicae
A. niger
F. oxysporum
100
200
300
100
200
300
100
200
300
Ligand
[Cu(L)]Cl2
[Cu(L)](NO3)2
[Ni(L)]Cl2
[Ni(L)](NO3)2
[Co(L)Cl2]
30
45
48
40
45
46
48
70
42
60
62
60
68
70
70
80
50
72
75
70
76
78
80
100
28
42
40
36
38
35
36
75
38
55
52
45
45
42
45
90
45
70
72
58
60
54
55
100
25
36
38
35
34
32
34
65
32
50
52
44
46
40
40
75
44
60
65
52
55
50
52
100
[Co(L)(NO3)2]
Standard (Captan)

100
A.K. Sharma, S. Chandra / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 103 (2013) 96–100
Fig. 2. Graph showing the activation of the pharmaceutical action of the antipathogen by the metal ions.
dispersion forces, are also taking place during the formation of
drug-receptor complex. These several weak interactions may com-
bine to produce a strong interaction to form drug –receptor com-
plex [21].
Appendix A. Supplementary material
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.saa.2012.11.012.
The results of the antifungal investigations of the ligand and
complexes are given in Table 5. After investigations, it has been
found that the compounds have fungicidal potential (Supplemen-
tary material) and the antipathogenic potential of the metal free li-
gand is positively modified by the coordination (Fig. 2) [22–25].
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The hydrazone based Schiff’s base has been synthesized and its
coordination behavior with Cu(II), Ni(II) and Co(II) metal ions has
also been studied. Formation of the hydrazone and its structural
studies reveal that it exhibits in fully protonated form in solid as
well as in solution form. Cu(II) and Ni(II) complexes were found
to have square planar geometry whereas the Co(II) complexes were
of tetragonal geometry. The ligand coordinates to metal ions in tet-
radentate fashion to give the stable complexes. The low value of
orbital reduction factor k and covalency factor b reveals the partial
covalent nature of complexes. Analytical data correspond to the
monomeric composition of the complexes. The fungicidal exami-
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ligand has growth inhibition capacity against the tested fungal
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Acknowledgements
Authors are thankful to the Sophisticated Analytical Instrument
Facility of IIT Bombay for recording EPR spectra and USIC, Univer-
sity of Delhi, for recording IR, Mass and NMR spectra. We also
acknowledge the financial assistance of DRDO, Delhi. We are also
thankful to Prof. Pratibha Sharma, IARI Pusa, New Delhi, for provid-
ing the laboratory facilities for biological studies.
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