Synthesis, characterization and antibacterial activity of novel schiff bases derived from 4-phenyl-2-aminothiazole and their Mn(II), Fe(II), Co(II), Ni(II) and Cu(II) Metal complexes

Article abstract of DOI:10.1155/2011/875896

Novel Schiff bases and their metal complexes were derived from some hetero cyclic β-diketones with 4-phenyl-2-aminothiazole. All the synthesized compounds were confirmed their structure by Elemental analysis, FT-IR, ¹H NMR, ¹³C NMR,

Full text of DOI:10.1155/2011/875896

ISSN: 0973-4945; CODEN ECJHAO
E-Journal of Chemistry
2011, 8(4), 1556-1565
http://www.e-journals.net
Synthesis, Characterization and Antibacterial
Activity of Novel Schiff Bases Derived from
4-Phenyl-2-aminothiazole and their Mn(II), Fe(II),
Co(II), Ni(II) and Cu(II) Metal complexes
A. S. THAKAR§*, K. S. PANDYA§, K. T. JOSHI§, A. M. PANCHOLI
§Zydus Research Centre, Ahmedabad-382 210, India
Sir P.T. Science College, Modasa-383 315, India
Department of Chemistry
Navjivan Science College, Dahod-389 151, India
amitthakar_83@yahoo.co.in
Received 24 October 2010; Revised 26 December 2010; Accepted 8 January 2011
Abstract: Novel Schiff bases and their metal complexes were derived from
some hetero cyclic β-diketones with 4-phenyl-2-aminothiazole. All the
synthesized compounds were confirmed their structure by Elemental
analysis, FT-IR, 1H NMR, 13C NMR, Mass spectra, TGA analysis and
UV spectra. All the compounds were tested for their antibacterial activity.
Spectroscopic measurements suggest that all Schiff base metal complexes are
of type ML2.(H2O)2 (M=Mn, Fe, Co, Ni, and Cu) and all the metal complexes
shows moderate antibacterial activity in the agar cup assay method.
Keywords: Thiazole, Pyrazolin-5-one, Schiff base, Metal complex
Introduction
The thiazole ring is very important in nature. It occurs for example, in thiamine, a coenzyme is
required for the oxidative decarboxylation of α-keto acids. A tetra hydrothiazole also appears
in the skeleton of penicillin, which is one of the first and still most important broad-spectrum
antibiotics. Thiazole, thiazolamines are valuable medicines1-3. It is obvious that compounds
with the thiazole ring have a potential biological activity. Similarly 2-aminothiazoles are
known as biologically active compounds with a broad range of activity and they are also used
as intermediate products in the synthesis of antibiotics and dyes4.
2-Aminothiazole derivatives are widely used in pharmacology4. Aminothiazole exhibits
antimicrobial and antioxidant5 activity. Some substituted aminothiazole derivatives are used as
antioxidant additives to hydrocarbon fuels, minerals and synthetic lubricating oils, solid paraffin,

1557
A. S. THAKAR et al.
polyolefins and vegetable fats. Sym triazine derivatives containing substituents with 2-amino-
thiazole fragments are effective anticorrosive, antiwear and antiscuff additives to lubricating oils6.
In continuation of our work7-14 on the metal complexes of Schiff bases, we report here
the study of Schiff base metal complexes of Mn(II), Fe(II), Co(II), Ni(II) and Cu(II) derived
from 2-amino-4-phenylthiazole and substituted 4-acetyl-1-phenyl-3-methyl-2-pyrazolin-5-
one. Preparation, characterization and antibacterial activity of above metal complexes with
Schiff bases Ligand-L and Ligand-L1 are also reported here.
8
8
9
9
7
7
6
11
CH3
11
CH3
6
15
CH3
2
15
CH3
4
2
4
N
5
10
N
5
10
12
3
12
3
1
13
N
1
13
S
N
14
S
14
N
HO
N
N
HO
N
16
16
21
20
17
18
21
20
17
19
CH3
Cl
18
19
22
Ligand-L
Ligand-L1
Where, Ligand-L is a Schiff base of 2-amino-4-phenyl-thiazole with 4-acetyl-1-(4’-
methylphenyl)-3-methyl-2-pyrazolin-5-one and Ligand-L1 is a Schiff base of 2-amino-4-
phenyl-thiazole with 4-acetyl-1-(3’-chlorophenyl)-3-methyl-2-pyrazolin-5-one.
Experimental
All the chemicals used in the present study were of A.R. grade. Acetophenone, 4-methyl
acetophenone, propiophenone, 4-methylpropiophenone, iodine, hydrochloric acid,
sulfuric acid, thiourea, ethylacetoacetate, sodium acetate, calcium hydroxide, benzoyl
chloride, acetyl chloride, 1,4-dioxane and methanol (SD’s fine chemical Ltd and Merck
chemicals., Mumbai) were used without further purification. Absolute ethanol from
alembic Chemical Works Co. Ltd., Baroda was used after distillation. The Mn(II),
Co(II), Ni(II), Cu(II) metal acetate and Fe(II) sulphate (SD’s fine chemical Ltd,
Qualigens-Glaxo, Mumbai and Merck chemicals., Mumbai) were used for the
preparation of Schiff base metal complexes.
Melting points were taken in one side open capillaries on a Melting point apparatus having
model number VMP-D of a make VEEGO. Electronic Spectra were recorded in DMF solution
on LAMBDA 19, UV/VIS/NIR (“SICART-CVN” at Vallabh Vidyanagar, Gujarat, India). The
Mass spectra of all ligands were recorded on the instrument named LCMS-2010 A of make
Shimadzu. Carbon, hydrogen and nitrogen were estimated on a thermo fisher (Thermo electron
corporation Limited), flash elemental analyzer-1112. The 1H NMR and 13C NMR spectra of all
the ligands [in Deuterated Chloroform(CDCl3)] were recorded on a AVANCE-II 400 of make
BRUKER spectro-photometer using TMS [(CH3)4Si] as internal standard. The Infrared spectra of
the ligands studied in the present work were recorded on the model FT-IR-8300 of Shimadzu in
KBr (Zydus Research Center, Ahmedabad, India).
Synthesis of Schiff base ligands
5-Methyl-4-[1-(4-phenyl-thiazole-2-yl-imino)-ethyl]-2-p-tolyl-2H-pyrazol-3-ol (L)
A hot solution of 4-acetyl-1-(4’-methylphenyl)-3-methyl-2-pyrazolin-5-one (0.1 mol, 23 g)
in methanol (50 mL) was slowly added drop wise to a hot solution of 2-amino-4-phenyl-

Synthesis, Characterization and Antibacterial Activity
1558
thiazole15 (0.1 mol, 17.6 g) in methanol (35 mL). The resulting solution was refluxed for 3 h at 64 ˚C.
Solid compound precipitate out is desire Schiff base. Filtered and washed with cold methanol and
dried under vacuum oven at 50 ˚C. Yield: 29 g (75%). M.P. = 216 ˚C. Anal. Calcd. For C22H20N4OS:
C, 68.02; H, 5.19; N, 14.42; S, 8.25. Found: C, 67.94; H, 5.12; N, 14.32; S, 8.26. 1H NMR: (400
MHz, CDCl3 δ =14.10 (s, 1H, OH), 7.33 (s, 1H, Thiazole ring), 7.22-7.85 (m, 9H, 2Ar), 2.96 (s, 3H,
CH3), 2.47 (s, 3H, CH3), 2.31 (s, 3H, CH3). 13C NMR: (400 ΜΗz, CDCl3δ =165.18 (C=N, 3C),
161.02 (C=N, 10C), 159.56 (C-OH, 14C), 153.08 (C=C, 2C), 147.71 (C=N, 13C), 136.20, 134.65,
133.96, 129.49, 128.94, 128.73, 128.62, 127.89, 126.27, 126.14, 120.87, 119.54, (12C, 2Ar), 108.51
(C=C, 1C), 103.60 (C=C, 12C), 21.12 (CH3, 15C), 18.47(CH3, 22C), 17.94 (CH3, 11C).
2-(3-Chloro-phenyl)-5-methyl-4-[1-(4-pheny-thiazol-2-ylimino)-ethyl]-2H-pyrazol-3-ol (L1)
A hot solution of 4-acetyl-1-(3’-chlorophenyl)-3-methyl-2-pyrazolin-5-one16 (0.1 mol, 25 g)
in methanol (50 mL) was slowly added drop wise to a hot solution of 2-amino-4-phenyl-
thiazole (0.1 mol, 17.6 g) in methanol (35 mL). The resulting solution was refluxed for 3 h
at 64 ˚C. Solid compound precipitate out is desire Schiff base. Filtered and washed with cold
methanol and dried under vacuum oven at 50 ˚C. Yield: 32.6 g (80%). M.P. = 174 ˚C. Anal.
Calcd. For C21H17ClN4OS: C, 61.68; H, 4.19; N, 13.70; S, 7.84. Found: C, 57.59; H, 3.97; N,
12.77; S, 8.79. 1H NMR: 400 ΜΗz, CDCl3δ =13.93 (s, 1H, OH), 7.22 (s, 1H, Thiazole ring),
7.13-8.09 (m, 9H, 2Ar), 2.93 (s, 3H, CH3), 2.45 (s, 3H, CH3). 13C NMR: (400 ΜΗz, CDCl3
δ =165.55 (C=N, 3C), 161.42 (C=N, 10C), 159.26 (C-OH, 14C), 153.18 (C=C, 2C), 148.35
(C=N, 13C), 139.79, 137.48, 134.70, 133.87, 128.94, 128.69, 126.28, 124.79, 119.17, 117.03
(12C, 2Ar), 108.76 (C=C, 1C), 103.40 (C=C, 12C), 18.49(CH3, 11C), 17.94 (CH3, 15C).
Synthesis and characterization of metal complexes
For the preparation of complexes, an aqueous solution of metal acetate (0.05 M) and 1:4 dioxane
solution of ligand (0.05 M) were mixed in presence of acetate buffer (pH=6.5) and the mixture was
digested on sand bath for 30 minutes, cooled and filtered the precipitate and then washed with water
and then methanol to remove excess metal ions and unreacted Schiff bases respectively.
All the complexes are colored, non-hygroscopic and stable solids. They are insoluble in
water, sparingly soluble in all the common organic solvents but fairly soluble in DMF. Physical
properties of the complexes are given in Table 1. The molar conductance of the complexes is in
the range of 7.68 to 15.32 ohm-1 cm2 mol-1 indicates their non-electrolytic nature.
The metal contents in all the complexes were determined gravimetrically as MoO3 by
the method reported by Mohanti et al17. Carbon, hydrogen and nitrogen were determined
micro analytically. Molar conductivities in 10-3 M DMF were measured using “Equiptronics
EQ-660 digital conductivity meter” and a calibrated conductivity cell at room temperature.
Magnetic susceptibilities of the complexes were measured at room temperature (30 ˚C) using
Gouy balance (Sartorius, semi-micro, Sardar Patel University, Vallabh Vidyanagar, India).
Results and Discussion
Mass spectra
Mass spectra provide a vital clue for elucidation of compounds. The mass spectrum of
ligand L shows the molecular ion peak at m/z = 389.18 (M+), confirms the theoretical
molecular weight i.e. 388.49 of ligand L and spectrum of ligand L1 shows the molecular ion
peak at m/z = 409.15 (M+) and the isotopic peak at m/z = 411.16 due to 35Cl and 37Cl
isotopes of ligand L1. In both the spectra the molecular ion peak is base peak and the
intensity of these peaks reflects the stability and abundance of the ions.

1559
A. S. THAKAR et al.
Infrared spectral analysis of ligands and their metal complexes
The infrared spectra of the both ligands show υO-H (weakly H-bonded) band at 3086 cm-1 and
3134 cm-1 respectively18. The absence of this band in all the metal complexes indicates the
removal of proton of hydroxyl group of pyrazolin ring during the chelation. This is further
supported by the shift of C-O frequency from 1350 cm-1 (in ligand-L) to 1381-1356 cm-1
(in complexes) and from 1321 cm-1 (in Ligand-L1) to 1325-1379 cm-1 (in complexes) at the
higher frequency respectively19. The sharp intense band at 1626.05 cm-1 and 1624.12 cm-1
respectively in the ligands can be assigned to υC=N (azomethine). A downward shift
(∆υ = 10-35 cm-1) in υC=N (azomethine) is observed upon coordination indicating that the
nitrogen of azomethine group is involved in coordination. All the complexes show broad
band in the region 3300 cm-1 to 3550 cm-1 which may be assigned to υO-H of coordinated
water20. To account for the octahedral stereochemistry of the metal complexes, the
coordination of two water molecules is expected.
The bands present at ~500 cm-1 in Mn(II) complexes, ~560 cm-1 in Fe(II) complexes, ~590
cm-1 in Co(II) complexes, ~490 cm-1 in Ni(II) complexes and ~590 cm-1 in Cu(II) complexes
respectively may be due to metal-nitrogen stretching vibration21,22. A less intense band at ~1610
cm-1 in the spectrum of ligands may be assigned to υC=N (ring)23. All the metal complexes do not
show shifting in υC=N compared to its respective ligands. This suggests that the nitrogen atom of
the thiazole ring has not participated in the coordination. However, in water containing metal
complexes, this band is observed as a broad band with some fine structures this may be due to
coupling of the bending mode of coordinated24 water molecules with υC=N
.
Electronic spectra and magnetic studies of both ligands and their metal complexes
Both the ligands show two absorption bands at 38314 cm-1, 27472 cm-1 and 36900 cm-1,
26247 cm-1 respectively. No absorption was observed in the visible region for any of the
ligands. In the absence of quantum mechanical calculation, it is not possible to assign the
absorption bands to definite electronic transitions with complete certainty. However, it
appears reasonable to assign the bands to π→ π* transitions25. The electronic spectra of
Mn(II) complexes exhibit three very low intense bands, one at 16995 cm-1, 17012 cm-1
6
respectively which may rise due to A1g→4T1g (G) transition, another band at 18790 cm-1,
18305 cm-1 respectively assigned to 6A1g →4A1g(G) transition and the third band at 26049 cm-1,
6
25580 cm-1 respectively may be assigned to A1g →4A1g, 4Eg,(G) transition for Mn(II) ion in
octahedral environment. The µeff (c.f.Table 1) value of the complexes suggests the spin 3d5
configuration26. The electronic spectra of all Fe(II) complexes shows a broad band at
14700 cm-1, 15700 cm-1 respectively which may be assigned to the 5T2g→5Eg transition. The
magnetic moment value 4.99 and 5.09 B M respectively which indicates that the complexes
are spin-free and it has octahedral geometry27. The electronic spectra of Co(II) complexes
exhibited absorption bands in the region 8400 cm-1 to 9350 cm-1 and 18600 cm-1 to
4
4
19700 cm-1 corresponding to υ1 and υ3 transitions T1g(F)→4T2g(F)(υ1); T1g(F)→4T1g(P)( υ3).
In the present investigation, Co(II) complexes show the absorption bands at 9350 cm-1,
6670 cm-1 and 18600 cm-1, 19100 cm-1 corresponding to υ1 and υ3 transitions respectively.
These bands are the characteristics of high spin octahedral Co(II) complexes. However, υ2
band is not observed because of its proximity to strong υ3 transition. The magnetic
measurement of Co(II) complexes display magnetic moment value of 4.41 and 4.55 B.M.
which is in the octahedral range 4.40 to 4.53 B.M23. The Ni(II) complexes exhibited three
bands at 11047 cm-1, 15265 cm-1 and 26400 cm-1 as well as three bands at 10255 cm-1
3
17501 cm-1 and 26299 cm-1 which are attributed to the A2g→3T2g(F) (υ1); 3A2g→3T1g(F) (υ2)

Synthesis, Characterization and Antibacterial Activity
1560
and 3A2g→3T1g(p) (υ3) transitions respectively indicating octahedral geometry around Ni(II) ion.
Ni(II) complexes showed the magnetic moment value of 2.93 and 2.86 which is in the range of
2.90 to 3.02 B.M suggesting consistency with their octahedral environment28. For the Cu(II)
complexes with D4h symmetry, three spin allowed transitions 2B1g→2A1g (υ1),2B1g→2B2g (υ2) and
2B1g→2Eg (υ3) are possible but the electronic spectra of Cu(II) complexes display two bands at
14295 cm-1, 21548 cm-1 and 14156 cm-1, 21380 cm-1 respectively. There should be third
transition but we could not observe the same which may be due to very close energy values of
different states. Absence of any spectral band below 10000 cm-1 rules out the possibility for
tetrahedral structure of the present complexes are also suggestive for distorted octahedral
geometry of the complexes29. The low molar conductance values in DMF solution for all metal
complexes (Table 1) are indicating that the complexes are nonelectrolytes.
Magnetic properties
The room temperature magnetic moments of all the metal complexes are listed in Table 1.
The magnetic moment of Mn(II), Fe(II), Co(II) and Ni(II) metal complexes are in the range
required for high-spin octahedral metal complexes30-35 and Cu(II) metal complexes
correspond to one-unpaired electron36,37
.
TGA analysis of Mn(II), Fe(II), Co(II), Ni(II) and Cu(II) metal complexes
The thermograms of this group of metal complexes show three stage decomposition (c.f.Table 2).
All the metal complexes do not show weight loss below 120 °C, it indicates the absence of
lattice water in the metal complexes.
The first stage decomposition is obtained in the temperature range 140-210 °C. The %
weight loss in this range is corresponds the loss of two coordinated water molecules38,41. The
second stage decomposition is obtained in the temperature range 210-400 °C. The % weight
loss in this range is corresponds % weight loss of two Schiff base ligands.
The third stage decomposition range is obtained in the temperature range 400-900 °C.
The % weight loss in this range is corresponds % weight loss of metal oxide residue. The
decomposition pattern for the metal complexes of this category may be as follow: On the
basis of TGA and analytical data of all Mn(II), Fe(II), Co(II), Ni(II) and Cu(II) complexes
studied in the present work correspond to [ML2.(H2O)2] group.
On the basis of these results obtained from elemental analysis, infrared spectra,
electronic spectra, TGA analysis and magnetic susceptibility measurements the following
structures are proposed for the complex compounds of both ligands (Figure 1& 2).
CH3
CH3
N
CH3
N
S
H2O
N
O
M
N
O
N
OH2
N
S
N
H3C
N
CH3
H3C
Where M= Mn(II), Fe(II), Co(II), Ni(II) and Cu(II)
Figure 1. Metal complexes of ligand-L

Table 1. Analytical and physical data of Schiff base ligands and their metal complexes
Elemental analysis, % Found (Calculated)
Yield
λM
µeff
B.M.
Ohm-1
Ligand/Complexes Colour
M. F.
M .W.
%
75
68
68
61
65
60
80
60
61
55
56
65
C
H
N
S
Cl
M
cm2 mol-1
67.94 5.12 14.32 8.26
(68.02) (5.19) (14.42) (8.25)
60.95 4.86 12.98 7.45
(61.03) (4.89) (12.94) (7.41)
60.99 4.92 12.90 7.38
(60.97) (4.88) (12.93) (7.40)
60.74 4.82 12.85 7.42
(60.75) (4.87) (12.88) (7.37)
60.79 4.92 12.92 7.39
(60.77) (4.87) (12.88) (7.37)
60.46 4.81 12.84 7.36
(60.43) (4.84) (12.81) (7.33)
Ligand-L
Mn(L)2.2H2O
Fe(L)2.2H2O
Co(L)2.2H2O
Ni(L)2.2H2O
Cu(L)2.2H2O
Ligand-L1
Yellow
Creamy
Brown
C22H20N4OS
C44H42MnN8O4S2
C44H42FeN8O4S2
C44H42CoN8O4S2
C44H42N8NiO4S2
C44H42CuN8O4S2
C21H17ClN4OS
388.49
865.9
866.8
869.9
869.6
874.5
408.90
-
-
-
-
6.37
(6.34)
6.43
(6.44)
6.74
(6.77)
6.70
(6.75)
7.29
(7.27)
-
5.81
4.99
4.55
2.93
1.92
-
9.15
13.62
15.32
11.25
7.68
-
-
Dark
brown
-
Green
Brown
Yellow
-
-
61.59 4.20 13.77 7.89 8.72
(61.68) (4.19) (13.70) (7.84) (8.67)
-
55.23 3.98 112.41 7.01 7.73 6.07
(55.63) (4.00) (12.36) (7.07) (7.82) (6.06)
55.61 3.99 12.41 7.19 6.97 6.11
(55.58) (4.00) (12.35) (7.07) (7.01) (6.15)
55.60 4.12 12.27 7.14 7.71 6.65
(55.39) (3.98) (12.30) (7.04) (7.79) (6.47)
54.89 3.67 12.41 7.01 7.73 6.61
(55.40) (3.99) (12.31) (7.04) (7.79) (6.45)
55.17 4.01 12.34 7.03 7.81 6.69
(55.11) (3.96) (12.24) (7.01) (7.75) (6.94)
Mn(L1)2.2H2O
Fe(L1)2.2H2O
Co(L1)2.2H2O
Ni(L1)2.2H2O
Cu(L1)2.2H2O
Creamy C42H36Cl2MnN8O4S2 906.76
5.78
5.09
4.41
2.86
1.87
10.87
12.85
15.14
9.56
12.51
Brown
C42H36Cl2FeN8O4S2 907.66
C42H36Cl2CoN8O4S2 910.75
C42H36Cl2N8NiO4S2 910.51
Dark
brown
Green
Brown C42H36Cl2CuN8O4S2 915.37
Spectroscopic analysis of the Schiff bases Ligand-L and Ligand-L1 are given below

Synthesis, Characterization and Antibacterial Activity
1562
Table 2. Thermo analytical results of ligands and its metal complexes (control-DMF)
Mass lose observed (Calculated)
Compounds
Stage-III
Stage-I [140-210 °C] Stage-II [210-400 °C]
[400-900 °C]
[Mn(Ligand-L)2.2H2O]
[Fe(Ligand-L)2.2H2O]
[Co(Ligand-L)2.2H2O]
[Ni(Ligand-L)2.2H2O]
[Cu(Ligand-L)2.2H2O]
[Mn(Ligand-L1)2.2H2O]
[Fe(Ligand-L1)2.2H2O]
[Co(Ligand-L1)2.2H2O]
[Ni(Ligand-L1)2.2H2O]
[Cu(Ligand-L1)2.2H2O]
4.12 (4.16)
4.11 (4.15)
4.20 (4.14)
4.07 (4.14)
4.09 (4.12)
3.93 (3.97)
3.87 (3.96)
3.99 (3.95)
3.97 (3.95)
3.89 (3.93)
86.85 (86.96)
86.79 (86.87)
88.45 (88.49)
89.28 (89.35)
86.85 (87.02)
87.34 (87.54)
87.35 (87.45)
88.09 (88.04)
89.77 (89.82)
87.55 (87.59)
9.07 (9.11)
9.25 (9.21)
8.49 (8.61)
6.66 (6.75)
8.97 (9.10)
8.77 (8.70)
8.76 (8.79)
8.12 (8.22)
6.39 (6.44)
8.66 (8.69)
Loss of two coordinated Loss of two Schiff base
water molecules
Assignment
Metal Oxide
ligand molecules
CH3
N
Cl
CH3
N
O
S
H2O
N
M
N
O
N
OH2
N
S
N
H3C
Cl
N
H3C
Where M= Mn(II), Fe(II), Co(II), Ni(II) and Cu(II)
Figure-2. Metal complexes of ligand-L1
Antibacterial activity
The effect of the ligands and their metal complexes in the growth media were investigated
by standard microbiological parameters. Concentration of the test compounds were kept
constant (500 ppm) during all the experiments. The bacterial, fungal and yeast cultures were
maintained on Nutrient-agar, Potato dextrose-agar and YEDP culture-tubes (slants)
respectively and were sub cultured every fortnight and stored at 0-5 °C temperature.
The compounds were tested in vitro for the antibacterial activity (Table 3) against
bacterial [Escherichia coli, Bacillus subtilis and S. aureus] and fungal [A.niger] and yeast
[S. cerevisiae] cultures were tested with both ligands and their metal complexes using Agar
cup assay method.

1563
A. S. THAKAR et al.
Table 3. Antibacterial activity of ligands and its metal complexes (control-DMF)
Compounds
E. coli
+
B. subtilis
S. aureus
S. cerevisiae
A. niger
[ Ligand-L]
[Mn(L)2(H2O)2]
[Fe(L)2(H2O)2]
[Co(L)2(H2O)2]
[Ni(L)2(H2O)2]
[Cu(L)2(H2O)2]
[Ligand-L1]
+
+
+ +
+ +
+ +
+
+
+
+
++
+
+ +
+ +
++
+
+
+
+
+ +
+ +
+
+ +
+ +
+ +
+ +
+ +
+
++
+ +
+ +
+ +
+
+
+
[Mn(L1)2(H2O)2]
[Fe(L1)2(H2O)2]
[Co(L1)2(H2O)2]
[Ni(L1)2(H2O)2]
[Cu(L1)2(H2O)2]
+ +
+ +
+ + +
+ + +
+ +
+
+
+
+ +
+ +
+ +
+
+
+
+ +
+ +
+
+ +
+ +
+ +
+
+ +
+ +
+ + +
+
The degree of effectiveness was measured by determining the diameters of the zone of
inhibition caused by the compounds. Effectiveness was classified into three zones on the
bases of their diameter of zone of inhibition.
+++
++
+
: Most effective
: Moderate effective
: Slightly effective
: Non effective
-
Most of the compounds were active against both gram (-) negative and gram (+)
positive bacteria. The results are presented in table given below.
The Schiff base Ligand-L without metal is slightly effective against all strains of
microorganisms.
•
•
•
•
The Mn(II) metal complexes are slightly effective against B. subtilis S. aureus & A.
niger when moderately effective against E. coli and S. cerevisiae.
The Fe(II) metal complexes are slightly effective against S. cerevisiae & A. niger when
moderately effective against E. coli, B. subtilis and S. aureus.
All the Co(II) and Ni(II) metal complexes are moderately effective against E. coli, B.
subtilis, S. aureus, S. cerevisiae and A. niger.
The Cu(II) metal complexes are slightly effective against B. subtilis & A. niger when
moderately effective against E. coli, S. aureus and S. cerevisiae.
The Schiff base Ligand-L1 without metal is slightly effective against all strains of
microorganisms.
•
•
•
•
•
The Mn(II) metal complexes are slightly effective against B. subtilis, S. aureus, S.
cerevisiae and A. niger when moderately effective against E. coli.
The Fe(II) metal complexes are slightly effective against A. niger and S. aureus when
moderately effective against E. coli, B. subtilis and S. cerevisiae.
The Co(II) metal complexes are moderately effective against S. aureus, B. subtilis, S.
cerevisiae and A. niger when most effective against E. coli.
The Ni(II) metal complexes are moderately effective against S. aureus, B. subtilis and
A. niger when most effective against E. coli and S. cerevisiae.
The Cu(II) metal complexes are slightly effective against A. niger, B. subtilis and S.
cerevisiae when moderately effective against S. aureus and. E. coli.

Synthesis, Characterization and Antibacterial Activity
1564
Conclusion
Spectroscopic measurements suggest that all Schiff base metal complexes are of type
ML2.(H2O)2 (M=Mn, Fe, Co, Ni and Cu). The synthesized metal complexes in comparison to
the uncomplexed Schiff base ligand were screened for their antibacterial activity against
pathogenic bacteria species (Escherichia coli, Bacillus subtilis, S. aureus, A. niger and
S. cerevisiae). The activity of the Schiff base complexes became more pronounced when
coordinated with metal ions. The biological activity of the complexes follow the order
Co(II)=Ni(II)> Mn(II), Fe(III), Cu(II).
Acknowledgments
The authors wish to express their gratitude to Dahod Anaj Mahajan Sarvjanik Education
Society for laboratory facilities, Principal N.V Patel Science College, V.V Nagar, Anand and
Zydus Cadila for spectral analysis and Chintan Shah for antibacterial activity of the complexes.
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