Synthesis, spectral characterization and biological activity of zinc(II) complexes with 3-substituted phenyl-4-amino-5-hydrazino-1, 2, 4-triazole Schiff bases

Article abstract of DOI:10.1016/j.saa.2011.08.019

New Zn(II) complexes have been synthesized by the reactions of zinc(II) acetate with Schiff bases derived from 3-substituted phenyl-4-amino-5-hydrazino- 1, 2, 4-triazole and benzaldehyde, 2-hydroxyacetophenone or indoline-2,3-dione. All these complexes are soluble in DMF and DMSO; low molar conductance values indicate that they are non-electrolytes. Elemental analyses suggest that the complexes have 1:1 stoichiometry of the type [ZnL(H₂O)₂], [ZnL′(OAc)₂(H₂O)₂] (L = dianionic Schiff bases derived from 3-(substituted phenyl)-4-amino-5-hydrazino-1, 2, 4-triazole and 2-hydroxyacetophenone or indoline-2,3-dione; L′ = neutral Schiff bases derived from 3-(substituted phenyl)-4-amino-5-hydrazino-1, 2, 4-triazole and benzaldehyde) and they were characterized by FT-IR, ¹H NMR, ¹³C NMR and FAB mass. All these Schiff bases and their complexes have also been screened for their antibacterial activities against Bacillus subtilis, Escherichia coli and antifungal activities against Colletotrichum falcatum, Aspergillus niger, Fusarium oxysporium and Carvularia pallescence by petriplates methods.

Full text of DOI:10.1016/j.saa.2011.08.019

Spectrochimica Acta Part A 85 (2012) 1–6
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Synthesis, spectral characterization and biological activity of zinc(II) complexes
with 3-substituted phenyl-4-amino-5-hydrazino-1, 2, 4-triazole Schiff bases
A.K. Singh, O.P. Pandey, S.K. Sengupta∗
Department of Chemistry, DDU Gorakhpur University, Gorakhpur 273009, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 9 June 2010
Received in revised form 27 July 2011
Accepted 10 August 2011
New Zn(II) complexes have been synthesized by the reactions of zinc(II) acetate with Schiff
bases derived from 3-substituted phenyl-4-amino-5-hydrazino-1, 2, 4-triazole and benzaldehyde,
2-hydroxyacetophenone or indoline-2,3-dione. All these complexes are soluble in DMF and DMSO; low
molar conductance values indicate that they are non-electrolytes. Elemental analyses suggest that the
complexes have 1:1 stoichiometry of the type [ZnL(H2O)2], [ZnLꢀ(OAc)2(H2O)2] (L = dianionic Schiff bases
derived from 3-(substituted phenyl)-4-amino-5-hydrazino-1, 2, 4-triazole and 2-hydroxyacetophenone
or indoline-2,3-dione; Lꢀ = neutral Schiff bases derived from 3-(substituted phenyl)-4-amino-5-
hydrazino-1, 2, 4-triazole and benzaldehyde) and they were characterized by FT-IR, 1H NMR, 13C NMR
and FAB mass. All these Schiff bases and their complexes have also been screened for their antibacterial
activities against Bacillus subtilis, Escherichia coli and antifungal activities against Colletotrichum falcatum,
Aspergillus niger, Fusarium oxysporium and Carvularia pallescence by petriplates methods.
© 2011 Published by Elsevier B.V.
Keywords:
Zn(II)
Schiff bases
FT-IR
1H NMR
13C NMR
Antifungal and antibacterial
1. Introduction
2. Experimental
Metal complexes of Schiff bases are playing an important role
in the development of coordination chemistry, which is evident
in number of publications, including physicochemical studies [1]
and biological aspects [2–6]. Triazoles and their derivatives are
found to be associated with various biological activities, such
as anticonvulsant, antifungal, anticancer, anti-inflammatory and
antibacterial properties [7–15]. Several compounds containing 1,
2, 4-triazole ring are well known for drug synthesis [7]. 1, 2,
4-Triazole containing amino group is also important for obtain-
ing various Schiff bases with well known antimicrobial properties
[16–23]. The Zn(II) complexes of Schiff bases are also biologi-
cally active and they exhibit enhanced activities as compared to
their parental ligands [22,24–26]. Several complexes of various
transition metals with Schiff bases derived from 3-substituted
phenyl-4-amino-5-hydrazino-1, 2, 4-triazole have been reported
from our laboratory [27]. The ligands have donor sites with ONNO
sequence and varied coordination ability. In this article we report
the synthesis, characterization, antifungal and antibacterial activ-
ity of Zn(II) complexes derived from Schiff bases of 3-substituted
phenyl-4-amino-5-hydrazino-1, 2, 4-triazole.
2.1. Materials and reagents
The solvents were purchased from Merck and used with-
out further purification. Zinc acetate dihydrate was purchased
from Aldrich. The ligands were prepared as reported in literature
[28].
2.2. Instruments
Melting points were determined by Buchi 530 apparatus in open
capillary tubes. IR spectra were recorded by Shimadzu 8201 PC
model FT IR spectrophotometer as KBr disks. 1H and 13C NMR
spectra were recorded by a Bruker DRX-300 spectrometer using
DMSO-d6 as solvent. Chemical shifts (ı) are reported in parts per
million (ppm) relative to an internal standard of Me4Si. Elemental
analysis was recorded by Elementar Vario EL III Carlo Erba 1108
models. Zinc was estimated gravimetrically as its dioxide ZnO2. A
known weight of the compound was decomposed by concentrated
nitric acid and the mass was extracted with distilled water. Sodium
carbonate solution was added. The precipitate obtained was filtered
by Whatmann filter paper No. 41, and finally ignited in silica cru-
cible to zinc oxide. Elemental analysis (C, H, N, Zn) indicates that the
found and calculated values were within acceptable limits ( 0.5).
Molar conductance of 10−3 M solutions of the complexes in DMSO
was recorded on a Hanna EC 215 conductivity meter by using 0.01 M
KCl water solution as calibrant. Magnetic measurements were
∗
Corresponding author. Tel.: +91 5512203621.
E-mail addresses: sengupta@hotmail.co.uk, sengupta2002@yahoo.co.in
(S.K. Sengupta).
1386-1425/$ – see front matter © 2011 Published by Elsevier B.V.
doi:10.1016/j.saa.2011.08.019

2
A.K. Singh et al. / Spectrochimica Acta Part A 85 (2012) 1–6
N
N
NH
R
N
NH2
NH2
Benzaldehyde
Isatin
ethanol
ethanol
N
N
2-Hydroxy-
N
N
NH
N
acetophenone
ethanol
R
H
N
N
NH
N
C
N
R"
N
N
N
H
C
R'
NH
NH
CH3
N
H3C
O
O
N
H
N
C
C
N
R=H, (L1H2); R=2-Cl,(L2H2);
R"=H, (L9); R"=2-Cl,(L10);
R=4-Cl, (L3H2); R=4-NO2, (L4H2)
R"=4-Cl, (L11); R"=4-NO2, (L12
)
HO
OH
R'=H, (L5H2); R'=2-Cl,(L6H2);
R'=4-Cl, (L7H2); R'=4-NO2, (L8H2)
Zn(OAc)2.2H2O
ethanol
Zn(OAc)2.2H2O
ethanol
Zn(OAc)2.2H2O
ethanol
N
N
N
N
N
N
NH
N
R"
NH
N
N
OH2
R
H2O
N
HC
N
N
N
NH
H3C
R'
N
CH3
OH2
C
H
N
C
C
O
O
Zn
O
N
O
Zn
C
OH2
C
O
N
O
O
O
OH2
OH2
CH3
CH3
R=H, [ZnL1(H2O)2];
R'=H, [ZnL5(H2O)2];
R=H, [ZnL9(OAc)2(H2O)2];
R=2-Cl, [ZnL2(H2O)2];
R=4-Cl, [ZnL3(H2O)2];
R=4-NO2, [ZnL4(H2O)2]
R'=2-Cl, [ZnL6(H2O)2];
R'=4-Cl, [ZnL7(H2O)2];
R'=4-NO2, [ZnL8(H2O)2]
R=2-Cl, [ZnL10(OAc)2(H2O)2];
R=4-Cl, [ZnL11(OAc)2(H2O)2];
R=4-NO2, [ZnL12(OAc)2(H2O)2]
Fig. 1. Reaction scheme for the preparation of Schiff bases and their zinc(II) complexes.
carried out on a Sherwood Scientific magnetic balance according
to the Gouy method. The purity of compounds was checked by
thin layer chromatography on silica gel plate using ether and ethyl
acetate as a solvent system. Iodine chamber was used as a devel-
oping chamber.
ligand (0.04 mol) to an aqueous ethanolic solution of zinc acetate
dihydrate (0.04 mol) and sodium acetate (0.08 mol). The mixture
was refluxed for 10–11 h on a water bath. Light yellow or brown
precipitate obtained was filtered, washed with ethanol and hot
water and dried in vacuo at room temperature. The complexes were
obtained as powdered material.
2.3. Synthesis of 3-(substituted phenyl)-4-amino-5-hydrazino-1,
2, 4-triazole
The details of the reactions along with the analytical data of the
product are given in Table 1. The general reaction scheme is given
in Fig. 1.
A mixture of 3-(substituted phenyl)-4-amino-5-mercapto-1, 2,
4-triazole and N2H4·H2O in molar proportions in ethanol was
boiled under reflux for 4–5 h on a water bath. The reaction mixture
was cooled at room temperature, within an hour the compound
separated from the clear solution. It was filtered, washed and
recrystallized in ethanol.
2.6. Biological activity study
2.6.1. Bio safety during the antibacterial and antifungal activity
Bacteria/fungi are potentially hazardous and care should be
taken while working with them. Standard bio safety lab techniques
were followed while handling bacteria/fungi and various media.
Gloves were used during all experimentation, and any acciden-
tal spills were immediately sterilized using 70% isopropanol/water
followed by bleach. The work area was also sterilized with 70%
isopropanol/water after completion of work. Unused media and
bacterial suspensions were first deactivated with commercial
bleach for 1 h before being disposed in bio safety bags. All mate-
rial that had come in contact with bacteria (e.g., pipette tips, tubes,
agar plates, etc.) was also thrown in bio safety bags in tightly closed
bins. Bio safety bags were autoclaved for 2 h before final disposal.
2.4. Synthesis of Schiff bases
A mixture of 3-(substituted phenyl)-4-amino-5-hydrazino-1,
2,
4-triazole
and
2-hydroxyacetophenone/indoline-2,3-
dione/benzaldehyde in 1:2 molar ratio in an alcoholic medium
containing a few drops of conc. HCl was refluxed for 5–6 h. The
product separated on evaporation of the alcohol was recrystallized
in ethanol.
2.5. Synthesis of zinc(II) complexes
2.6.2. Antimicrobial activity
A general procedure was followed to synthesize these com-
plexes. The procedure involves the addition of the appropriate
Synthesized Schiff bases and Zn(II) complexes were screened
for their antimicrobial activity against two bacterium (E. coli and

A.K. Singh et al. / Spectrochimica Acta Part A 85 (2012) 1–6
3
Table 1
Physical properties and analytical data of Zn(II) complexes of 3-(substituted phenyl)-4-amino-5-hydrazino-1, 2, 4-triazole Schiff bases.
Complex
Colour
Molecular weight found (cal.)
% Analysis found (cal.)
C
H
N
Zn
[ZnL1(H2O)2]
[ZnL2(H2O)2]
[ZnL3(H2O)2]
[ZnL4(H2O)2]
[ZnL5(H2O)2]
[ZnL6(H2O)2]
[ZnL7(H2O)2]
[ZnL8(H2O)2]
[ZnL9(OAc)2(H2O)2]
[ZnL10(OAc)2(H2O)2]
[ZnL11(OAc)2(H2O)2]
[ZnL12(OAc)2(H2O)2]
Brown
Brown
Yellow
Orange
Cream
Cream
Yellow
Brown
White
Muddy
Yellow
White
546(547.86)
581(582.10)
581(582.12)
590(592.85)
524(525.89)
559(560.34)
558(560.34)
569(570.89)
584(585.94)
618(620.39)
620(620.39)
630(630.94)
52.55(52.61)
49.41(49.50)
49.43(49.50)
48.50(48.62)
54.71(54.81)
51.32(51.44)
51.35(51.44)
50.33(50.49)
53.20(53.29)
50.25(50.34)
50.20(50.34)
49.33(49.49)
3.20(3.31)
2.86(2.94)
2.85(2.94)
2.80(2.89)
4.55(4.60)
4.10(4.14)
4.11(4.14)
4.00(4.06)
4.75(4.82)
4.30(4.39)
4.31(4.39)
4.25(4.31)
20.34(20.45)
19.12(19.24)
19.16(19.24)
21.16(21.26)
15.87(15.98)
14.95(15.00)
14.93(15.00)
17.10(17.17)
14.29(14.34)
13.45(13.55)
13.46(13.55)
15.45(15.54)
11.85(11.94)
11.11(11.23)
11.10(11.23)
10.95(11.03)
12.30(12.44)
11.60(11.67)
11.62(11.67)
11.40(11.46)
11.10(11.16)
10.45(10.54)
10.47(10.54)
10.20(10.37)
B. subtilis) and four fungal (C. falcatum, A. niger, F. oxysporium and
C. pallescence) organisms by different two ways.
weight of complexes is unaffected in magnetic field which indicates
that they are diamagnetic.
2.6.2.1. Growth of inhibition. All Schiff bases and Zn(II) complexes
were screened for their activity against four fungal organisms
C. falcatum, A. niger, F. oxysporium and C. pallescence and two bac-
teria namely B. subtilis, and E. coli by petridishes method [29].
Fungicidal and bactericidal activity of each compound was eval-
uated at three different concentrations, i.e., 10, 100 and 1000 ppm.
For each compound 1% standard solution was prepared and 1 ml
of the solution was diluted with 9 ml of the solvent (DMSO).
Petridishes of equal diameter were sterilized at 180 ◦C. Stock solu-
tions of each compound were prepared for three concentration viz.
10, 100 and 1000 ppm. Solution of 1 ml of each concentration was
poured in presterilized petridishes and 9 ml of agar medium was
added immediately. Each dish was rotated on the table top in order
to achieve thorough mixing of medium with the compound. After
this, fungus and bacterial strain was inoculated in the dishes (diam-
eter 5 mm). These set were then inoculated at 30 2 ◦C. The colony
diameter of the test organism was measured with mm scale after 6
days. The percentage inhibition of the growth of the test organism
was calculated by following formula
3.1. Infrared spectra
The characteristic FT-IR spectral bands of Zn(II) derivatives
are given in Table 2. The IR spectra provide valuable informa-
tion regarding the nature of the functional group attached to the
metal atom. Schiff bases (L1H2–L4H2) appear to exist in both keto
and enol tautomeric forms (Fig. 2) suggested by a broad band
(solution spectra) at 2600 cm−1, due to intramolecular H-bonded
OH group. The spectra of Schiff bases show a medium band at
3175 cm−1 due to ꢁ(N–H) which remains almost at the same posi-
tion in complex indicating the non involvement of N–H group in
bond formation. The ligands show one medium intensity band at
1630 cm−1 assignable [27] to ꢁ(C N) which shifts to 1605 cm−1
in the complexes. This shift indicates the coordination of azome-
thine nitrogen to metal ion [32–35]. The bands at 435–400 cm−1
are assigned [35] to ꢁ(Zn–N). L5H2–L8H2 Schiff bases show broad
band at 2640 cm−1 due to intramolecular H-bonded OH group. This
band disappears in their corresponding Zn(II) complexes indicat-
ing the coordination of phenolic oxygen to zinc metal ion through
deprotonation. This is further supported by shift in phenolic ꢁ(C–O)
band from 1285 cm−1 (in the free ligand) to 1380–1310 cm−1 in
the complexes. The coordination through phenolic oxygen further
confirmed by the appearance of band at 480–445 cm−1 assignable
[36] to ꢁ(Zn–O). The presence of coordinated water in the com-
plexes [37] is indicated by a broad band in the region 3400 cm−1
and two weaker bands in the region 810–750 and 730–700 cm−1
dueto ꢁ(–OH)rockingandwaggingmodeof vibrations, respectively
[38]. The complexes with ligands L9–L12 show strong bands in the
region 1750–1720 cm−1 which are assigned to ꢁ(OOCCH3). In com-
plexes Zn–O band appears at 402–380 cm−1 [39], which indicates
that metal zinc is bonded to acetate molecule. Further, the absorp-
tion at 1616 and 1410 cm−1, confirm the monodentate nature of
the acetate ion in complexes with ligand L9–L12 [39].
Cd − Td
inhibition (%) =
× 100
Cd
where Cd = colony diameter of control; Td = colony diameter of
treated set.
2.6.2.2. Minimum inhibitory concentration MIC (ppm). The min-
imum inhibitory concentration to 99% kill of the bacterial
population (MIC) of against the bacterial strain was determined
by reported methods [30]. Bacteria were grown overnight in 10 ml
of LB, 37 ◦C for E. coli and 30 ◦C for B. subtilis at 220 rpm. A total
of 100 ␮l of the overnight culture was subcultured in 10 ml of
LB, 220 rpm and grown to exponential phase (OD600 = 2.3299), and
1 ml was then inoculated into LB broth containing various concen-
trations of Schiff base and there Zn(II) complexes (OD600 = 1.000)
maintained by adding DMSO. Cultures were then grown for 24 h,
220 rpm and bacterial growth was determined by measuring the
optical density at 600 nm. Fungal MIC was measured by reported
methods [31].
3. Results and discussion
Zn(II) complexes are sparingly soluble in common solvents;
however, these complexes are soluble in DMF and DMSO. The
molar conductivity values for all Zn(II) complexes in (10−3 M)
were in range of 6–15 ꢀ−1 cm2 mol−1 suggesting them to be non-
electrolytes. Magnetic susceptibility measurement shows that the
Fig. 2. Synthesized Schiff bases in tautomeric forms.

4
A.K. Singh et al. / Spectrochimica Acta Part A 85 (2012) 1–6
Table 2
The importance infra red frequencies in (cm−1) of Zn(II) complexes of 3-(substituted phenyl)-4-amino-5-hydrazino-1, 2, 4-triazole Schiff bases.
Complex
IR frequency (cm−1
)
ꢁ(O–H)
ꢁ(N–H)
ꢁ(CH3COO)
ꢁ(C N)
ꢁ(C C)
Phenolic ꢁ(C–O)
ꢁ(Zn–O)
ꢁ(Zn–N)
[ZnL1(H2O)2]
[ZnL2(H2O)2]
[ZnL3(H2O)2]
[ZnL4(H2O)2]
[ZnL5(H2O)2]
[ZnL6(H2O)2]
[ZnL7(H2O)2]
[ZnL8(H2O)2]
[ZnL9(OAc)2(H2O)2]
[ZnL10(OAc)2(H2O)2]
[ZnL11(OAc)2(H2O)2]
[ZnL12(OAc)2(H2O)2]
3430
3434
3340
3445
3435
3436
3438
3446
3425
3432
3431
3442
3175
3170
3172
3170
3170
3175
3180
3185
3155
3165
3170
3175
–
–
–
–
–
–
–
–
1595
1580
1600
1588
1580
1615
1605
1610
1595
1580
1590
1610
1575
1580
1615
1570
1575
1578
1595
1598
1576
1585
1592
1580
1375
1350
1343
1380
1355
1350
1310
1340
–
450
452
455
445
460
465
462
470
480
475
472
470
425
435
419
430
415
410
400
405
420
422
425
430
1735
1740
1750
1745
–
–
–
3.2. 1H NMR spectra
Zinc(II) complexes also show new signal at 5.5 ppm due to the water
protons.
The proton magnetic resonance spectra of these complexes have
been recorded in DMSO-d6. Chemical shifts for protons in different
environments have been given in Table 3. Schiff bases derived from
indoline-2, 3-dione of type (L1H2–L4H2) exhibit signals at 12.40
and 5.5 ppm due to hydrazino NH proton and indoline-2, 3-dione
NH proton, respectively. In zinc(II) complexes indoline-2, 3-dione
NH peak disappears. Multiplet is observed at 7.00–7.75 ppm due to
aromatic protons in the Schiff bases and their corresponding Zn(II)
complexes. Zinc (II) complexes show new signal at 5.6 ppm which
are assigned for water protons.
Schiff bases derived from 2-hydroxyacetophenone (L5H2–L8H2)
exhibit signals at 12.66 and 10.50 ppm due to hydrazino NH and
phenolic –OH proton respectively and phenolic protons disappear
in their corresponding Zn(II) complexes; this confirms that the
hydroxyl group reacted with metal ion via deprotonation. Multi-
plet is observed at 7.00–7.70 ppm due to aromatic protons in the
Schiff bases and their corresponding Zn(II) complexes. Schiff bases
(L5H2–L8H2) and their corresponding Zn(II) complexes also exhibit
a signal at 1.15–1.30 ppm due to methyl protons and zinc(II) com-
plexes ([ZnL5·H2O)2]–[ZnL8·(H2O)2]) show new signal at 5.4 ppm
due to the water protons.
3.3. 13C NMR spectra
The 13C NMR spectra of these complexes were recorded
(Table 3) in DMSO-d6. Schiff bases derived from Indoline-2, 3-dione
(L1H2–L4H2) show signals at ı 156 and ı 147 for their azomethine
carbons and they shift downfield in their corresponding zinc(II)
complexes due to the coordination through azomethine nitrogens.
Schiff bases derived from 2-hydroxyacetophenone (L5H2–L8H2)
show signals at ı 164 and ı 154 for their azomethine carbons and
they shift downfield in zinc metal complexes due to coordination
through the azomethine nitrogen. For –CH3 carbon, a signal appears
at ı 13.5 in ligands and their corresponding complexes.
Schiff bases derived from benzaldehyde (L9–L12) show signals
at ı 174 and ı 166 for their azomethine carbons and they shift
downfield in their corresponding zinc(II) complexes due to coor-
dination through the azomethine nitrogen. The complexes of type
([ZnL9(OAc)2·(H2O)2]–[ZnL12(OAc)2·(H2O)2]) show signals at ı 23.5
(CH3) and ı 181.5 (–COO) due to the presence of coordinated acetate
molecules.
Schiff bases of type (L1H2–L8H2, and L9–L12) and their corre-
sponding zinc(II) complexes show signals at about ı 158 and ı 152
assignable for triazole ring carbons. For aromatic ring, a number of
signals appear.
The 1H NMR spectra of Schiff bases of type (L9–L12) exhibit
signals at 12.4 and 8.10 ppm due to NH and azomethine protons,
respectively. In zinc(II) complexes, the first signal remains almost
at the same position but the second signal shifts downfield. The
downfield shift indicates the deshielding effect due to the co-
ordination of azomethine nitrogen to central metal ion. Complexes
of type ([ZnL9(OAc)2·(H2O)2]–[ZnL12(OAc)2·(H2O)2]) show signal
at 2.48–2.50 ppm due to methyl protons of coordinated acetate
molecules [34]. Schiff bases and their corresponding Zn(II) com-
plexes show multiplet at 6.98–7.80 ppm due to aromatic protons.
3.4. FAB mass spectra
The molecular weight of the complexes, as determined from
their FAB-mass spectra, is given in Table 1. Elemental analysis
values are in close agreement with the values calculated from
Table 3
1H NMR and 13C NMR spectral band (ppm) of Zn(II) complexes of 3-(substituted phenyl)-4-amino-5-hydrazino-1, 2, 4-triazole Schiff bases.
Compound
NMR data
–NH(s)
13C NMR
–COO
–CH3(s)
Aromatic ring (M)
–HC N(S)
–CH3
–C
N
Aromatic ring
[ZnL1(H2O)2]
[ZnL2(H2O)2]
[ZnL3(H2O)2]
[ZnL4(H2O)2]
[ZnL5(H2O)2]
[ZnL6(H2O)2]
[ZnL7(H2O)2]
[ZnL8(H2O)2]
[ZnL9(OAc)2(H2O)2]
[ZnL10(OAc)2(H2O)2]
[ZnL11(OAc)2(H2O)2]
[ZnL12(OAc)2(H2O)2]
12.40
12.42
12.41
12.40
12.44
12.45
12.41
12.40
12.30
12.45
12.43
12.40
–
–
–
–
1.15
1.18
1.24
1.30
2.48
2.54
2.52
2.57
7.02–7.51
7.02–7.55
7.00–7.65
7.05–7.70
6.95–7.45
6.92–7.40
6.90–7.35
6.91–7.37
6.98–7.70
7.05–7.80
7.04–7.75
7.00–7.80
–
–
–
–
–
–
–
–
8.26
8.31
8.34
8.28
–
–
–
–
–
–
–
–
–
–
–
–
13.3
13.4
13.5
14.2
23.6
23.4
23.8
23.5
166.3,156.7
166.1,156.1
166.2,156.2
166.3,156.4
165.3,157.2
165.4,157.3
165.7,157.5
165.8,157.7
166.6,158.5
167.3,158.5
167.1,158.6
167.4,158.9
150.2,131.2,130.6,130.2,129.4,127.5,126.6,122
150.3,138.7,132.5,130.3,130.0,129.4,128.9,127.3,126.7
151.2,135.2,130.2,129.5,128.9128.7,126.7,122
149.5,147.9,130.2,127.7,126.6,124.8,122.3
131.3,130.7,129.5,127.5,121.4,116,115.9
135.2,130.2,129.9,128.7,121.4,116.3,115.9
148.3,137.5,130.2,127.3,124.5,121.3,116.2,116.2,115.9
150.3,131.4,130.9,130.6,129.7,128.9,127.8
150.3,138.6,132.8,131.4,130.7,129.6,129.1,129.8,127.6
150.9,136.6,131.5,130.5,129.6,128.6
181.3
181.5
181.8
182.6
150.8,131.2,132.2,131.0,129.7,128.6,126.9
151.0,132.1,132.8,131.5,129.9,128.7,127.4

A.K. Singh et al. / Spectrochimica Acta Part A 85 (2012) 1–6
5
Table 4
Fungicidal screening data of Zn(II) complexes of 3-[substituted phenyl]-4-amino-5-hydrazino-1, 2, 4-triazole Schiff bases.
Compound
% Fungicidal inhibition ppm
C. falcatum
A. niger
F. oxysporium
C. pallescence
1000
100
10
40
1000
100
10
35
1000
100
10
38
1000
100
10
42
[ZnL1(H2O)2]
[ZnL2(H2O)2]
[ZnL3(H2O)2]
[ZnL4(H2O)2]
[ZnL5(H2O)2]
[ZnL6(H2O)2]
[ZnL7(H2O)2]
[ZnL8(H2O)2]
[ZnL9(OAc)2(H2O)2]
[ZnL10(OAc)2(H2O)2]
[ZnL11(OAc)2(H2O)2]
[ZnL12(OAc)2(H2O)2]
Standard
75
95
91
83
70
90
85
80
69
85
80
75
100
55
81
80
70
60
77
73
69
58
65
63
68
100
70
91
89
81
75
85
80
77
85
87
81
82
100
50
80
76
69
61
67
64
63
60
69
63
61
100
73
93
90
85
69
87
83
79
81
92
91
91
100
54
79
75
72
58
74
70
64
65
66
74
61
100
70
90
87
82
67
84
80
78
65
85
81
79
100
52
70
67
64
58
64
64
65
55
58
57
52
100
56
56
50
40
58
60
59
41
45
51
48
100
50
47
50
45
51
49
50
33
48
44
45
100
52
50
60
43
54
51
51
51
54
57
46
100
51
49
53
43
50
49
55
45
48
47
46
100
Table 5
Bactericidal Screening data of Zn(II) complexes of 3-[substituted phenyl]-4-amino-5-hydrazino-1, 2, 4-triazole Schiff bases.
Compound
% Bactericidal inhibition concentration in ppm
B. subtilis
E. coli
1000
100
10
36
1000
100
10
[ZnL1(H2O)2]
[ZnL2(H2O)2]
[ZnL3(H2O)2]
[ZnL4(H2O)2]
[ZnL5(H2O)2]
[ZnL6(H2O)2]
[ZnL7(H2O)2]
[ZnL8(H2O)2]
[ZnL9(OAc)2(H2O)2]
[ZnL10(OAc)2(H2O)2]
[ZnL11(OAc)2(H2O)2]
[ZnL12(OAc)2(H2O)2]
Standard
63
69
65
68
62
67
63
66
59
66
62
65
100
52
59
54
58
53
57
53
55
47
54
49
51
100
64
71
67
68
63
70
65
67
62
68
66
67
100
56
61
58
60
56
62
57
60
49
57
51
55
100
38
44
42
40
34
39
36
34
32
39
38
35
100
43
40
37
31
37
35
33
30
35
34
31
100
molecular formulas assigned to these complexes, which is further
supported by the FAB-mass studies.
mechanism of increased activity of complexes is not certain but
factors like solubility, dipole moment and cell permeability mech-
anism and their enzymatic action may be the possible reason.
In antifungal strain we observed that the all ligands and Zn(II)
complexes are more active against C. falcatum. Substitution of the
ligands increases the activity against bacteria and fungi. 2-Chloro
3.5. Microbial activity
Microbial studies suggested that all the Schiff bases are antimi-
crobial active and their Zn(II) complexes shows importantly raised
antibacterial and antifungal activities. The antibacterial, antifungal
results are systematized in Tables 4 and 5 and MIC of the 2-chloro
substituted Zn(II) complexes are shown in Table 6. The compara-
tive data for active compounds and standard drug used for present
study is shown in Fig. 3. This experimental observation indicates
that increases chelation, bacterial and fungal growth inhibition also
increases. Previously reported [40,41] observation shows that het-
erocyclic ring has cell wall damaged capacity, in newly synthesized
Schiff bases have oxadiazole ring which contact with the microbes
cell wall and damaged this causes microbes dead. The actual
Table 6
Minimum inhibitory concentration results in ppm.
Microbes
MIC in ppm
[ZnL2(H2O)2]
[ZnL6(H2O)2]
[ZnL10(OAc)2(H2O)2]
B. subtilis
E. coli
C. falcatum
A. niger
F. oxysporium
C. pallescence
>2000
>1700
>1300
>1450
>1400
>1500
>2200
>1750
>1400
>1600
>1500
>1700
>2250
>1900
>1450
>1700
>1550
>1800
Fig. 3. In vitro antibacterial and antibacterial spectrum of compounds [ZnL2(H2O)2],
[ZnL6(H2O)2], [ZnL10(OAc)2(H2O)2] Standard (gentamycine for antibacterial and flu-
conazole for antifungal) at 1000 ppm concentration.

6
A.K. Singh et al. / Spectrochimica Acta Part A 85 (2012) 1–6
substituted ligands/compounds are more active than the other
substituted ligands/compounds due to the chelating properties of
2-chloro group. The compound [ZnL2(H2O)2] is more active against
all bacteria and fungi because they have additional heterocyclic ring
(indoline-2,3-dione). All Schiff bases and Zn(II) complexes are more
active against E. coli.
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The new zinc(II) complexes with Schiff bases derived from
3-substituted phenyl-4-amino-5-hydrazino-1, 2, 4-triazole have
been synthesized and characterized on the basis of analyses, elec-
trical conductance, magnetic moment and spectral data. The Schiff
bases derived from 3-substituted phenyl-4-amino-5-hydrazino-
1, 2, 4-triazole and isatin/2-hydroxyacetophenone act as dibasic
tetradentate ligands coordinating through the two azomethine
nitrogens and two oxygen atoms to the metal ion. The ligands
derived from 3-substituted phenyl-4-amino-5-hydrazino-1, 2, 4-
triazole and benzaldehyde act as neutral, bidentate ligands. The
six-coordinated structures of complexes have been proposed. Anti-
fungal and antibacterial activity of the ligands and the complexes
have also been evaluated which show that activity increases on
chelation.
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Acknowledgements
The authors are thankful to the Head, Sophisticated Analytical
Instrument Facility, Central Drug Research Institute, Lucknow, for
providing IR, 1H NMR, 13C NMR and FAB mass spectra data. We
thank the UGC [Ref.F.4-5/2006 (XI plan)/23 dated Jan 12, 2007)
for financial support. Authors are also thankful to Department of
Biotechnology, D.D.U. Gorakhpur University, Gorakhpur, for help
in evaluating antibacterial activities.
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