Synthesis, characterization and antibacterial activity of some halo substituted Schiff bases

Article abstract of DOI:10.1155/2010/571309

Some new halo substituted Schiff bases have been prepared from different aromatic aldehydes and a series of substituted aromatic amines to form a number of potentially biologically active compounds. The structures of the Schiff bases have been characterized by using IR and 1HNMR spectroscopy. These compounds were screened against human pathogenic bacteria by agar diffusion method. Ampicillin was used as control.

Full text of DOI:10.1155/2010/571309

ISSN: 0973-4945; CODEN ECJHAO
E-Journal of Chemistry
2010, 7(3), 882-886
http://www.e-journals.net
Synthesis, Characterization and Antibacterial
Activity of Some Halo Substituted Schiff Bases
S.B. JUNNE*, ARCHANA B. KADAM,
S.L. SHINDE§, G.S. WAGHAMARE and Y.B. VIBHUTE.
P.G. Department of Chemistry,
Yeshwant Mahavidyalaya, Nanded-05. (M.S.), India.
§Department of Botany, Yeshwant Mahavidyalaya, Nanded, India.
sbjunne@gmail.com
Received 13 September 2009; Revised 11 November 2009; Accepted 5 January 2010
Abstract: Some new halo substituted Schiff bases have been prepared from
different aromatic aldehydes and a series of substituted aromatic amines to
form
a number of potentially biologically active compounds. The
structures of the Schiff bases have been characterized by using IR and
1HNMR spectroscopy. These compounds were screened against human
pathogenic bacteria by agar diffusion method. Ampicillin was used as
control.
Keywords: Aromatic amines, Aromatic aldehydes, Schiff bases, Antibacterial activity, Ampicillin.
Introduction
New halo substituted Schiff bases were used as substrates in the preparation of number
of biologically active compounds1. Moreover Schiff bases were also known to have
biological activities such as antimicrobial2-5, antifungal4-6, antitumor7-9 and herbicides10.
They were also used as starting materials for synthesis of various biologically active
heterocyclic compounds11.
Considering a literature survey of Schiff bases, we have decided to synthesize new
Schiff bases which were predicted to have useful biological activity. Present study of Schiff
bases have been synthesized by refluxing a mixture of different aromatic aldehydes with
substituted aromatic amines and few drops of acetic acid in methanol12. On cooling, solid
separated out. Solid products were crystallized from ethyl alcohol. Structures of the
synthesized compounds were conformed by elemental analysis and spectral studies.
All these compounds were screened against human pathogenic bacteria i.e.
Dermatophillus congolensis, Proteus vulgaris, Staphylococcus aureus, Corynebacterium

Synthesis, Characterization and Antibacterial Activity
883
parvum and Actinomyces bovis. The antibacterial activity was evaluated using agar diffusion
method13-15. The solvent were used as dimethyl formamide (DMF) and dimethyl sulfoxide
(DMSO). Ampicillin was used as control for comparison.
MeOH + ACOH
Ar-NH2 + Ar`-CHO
Ar-N=CH-Ar`
Scheme 1
Experimental
All the melting points were taken in open capillary tube. The purity of compounds was
checked by TLC using silica gel G. The IR spectra were recorded with KBr pellets on
1
Perkin-Elmer 157 spectrophotometer, HNMR spectra on Bruker WN-400 MHz FT-NMR
instrument using CDCl3 on reference (Chemical shift in δ, ppm).
Typical procedure for synthesis of Schiff bases
An equimolar mixture of aromatic aldehydes (0.001 M) and substituted aromatic amines (0.001
M) in methanol containing acetic acid (0.5 mL) was refluxed for 3 h. Excess of solvent was
distilled and residue kept in cold water. The separated solid was filtered, dried and recrystallized
from ethyl alcohol. The purity of the products was conformed by TLC. Details of their
elemental and physical properties are given in Table 1 and spectral data are given in Table 2.
Table 1. Elemental and physical data of halo substituted Schiff bases.
Ar
Ar’
I=28.73
Synthesis,
OMe
I
C16H15
N2O5I
43.43 3.39 6.33
(43.56) (3.48) (5.89)
OMe
Ia
Ib
120 80
Characterization
and Antibacterial
(28.68)
NO2
OMe
OMe
Cl
Cl=15.23
(15.38)
I=27.25(26.98)
OMe
C16H14
NO3ICl2
41.20 3.00 3.00
(41.32) (2.88) (3.12)
I
80 78
OMe
Cl
HO
COOH
Br=17.92
(18.09)
I=28.47(28.52)
C14H9
NO3IBr
37.66 2.01 3.13
(37.52) (2.12) (2.98)
Ic
230 64
86 75
I
Br
HO
Br=17.89
(18.06)
I= 28.41(28.55)
I
C13H8
N2O3IBr
34.89 1.78 6.26
(35.02) (2.02) (6.10)
Id
NO2
Br
OMe
C14H10
NO2FBr2
41.68 2.48 3.47 F=4.71 (5.01)
(41.82) (2.62) (3.02) Br=39.70(39.98)
F
OH
Ie
65 58
Br
Br

884
S.B. JUNNE et al.
Br
OMe
Me
C16H15
NO2Br
57.65 4.50 4.20
(57.78) (4.38) (3.99)
Br= 24.02
(23.85)
OH
If
160 68
110 72
Me
Br
Br
OMe
Me
Br
C16H15N
O2Br2
46.48 3.63 3.38
(46.62) (3.78) (3.09)
Br=38.74
(39.00)
OH
Ig
Me
Br
OMe
C13H10N2
O2Br2
40.41 2.59 7.25
(40.10) (2.10) (7.38)
Br= 41.45
(41.28)
OH
Ih
Ii
130 55
55 55
N
Br
F
F=7.08
(6.92Br=29.85
(30.02)
C11H7NO
FBr
49.25 2.61 5.22
(48.98) (2.42) (5.01)
O
Br
Cl
C11H6
NOBr 78 58
Cl2
Cl= 22.25
(21.99)Br=25.07
(24.89)
Cl
41.37 1.88 4.30
(41.10) (1.71) (4.05)
Ij
O
Br
Table 2. IR (cm-1) and 1HNMR (δ, ppm) spectral data of halo substituted Schiff bases.
Entry
IR, cm-1
1HNMR, δ, ppm
2920, 2800 (CH3),1660 (C=N), 1515, 3.1 (s, 3H, OMe), 3.2 (s,6H,OMe), 8.7
1440 (NO2), 1620, 1600, 1560 (C=C) (s,1H,=CH), 7.5-8.3 (m.5H,Ar-H).
Ia
Ib
Ic
Id
Ie
2910, 2800 (CH3), 1660 (C=N),
1610, 1600, 1550 (C=C).
3.0(s,3H,OMe), 3.3 (s,6H,OMe)8.8
(s,1H,=CH),7.9-8.5 (m,4H,Ar-H).
8.3 (s,1H,=CH), 7.5-8.1 (m, 6H,Ar-H),
11.4 (s,1H,OH) 12.2 (s,1H,Ar-OH).
3400 (-OH),1764 (C=O), 1655,
(C=N),1610,1590, 1500 (C=C).
3350 (-OH), 1670 (C=N) 1525, 1430 8.8 (s,1H,=CH), 7.5-8.6 (m,6H,Ar-H),
(NO2), 1610, 1520, 1490 (C=C).
2915, 2850 (CH3), 1650 (C=N),
1620, 1600, 1580 (C=C) 3320 (OH). (s,1H,Ar-OH), 7.2-8.4 (m,5H,Ar-H).
12.1 (s,1H,Ar-OH).
3.2 (s,3H, OMe), 8.9 (s,1H,=CH) 12.1
3.4 (s,3H,OMe), 2.5 (s,6H, CH3), 8.8
2930,2845, (CH3), 3400 (-OH), 1640
(s,1H,=CH), 7.5-8.4 (m,4H,Ar-H), 12.4
(C=N) 1620, 1590, 1550, (Ar-H)
If
(s,1H,Ar-OH)
2.4 (s,6H,CH3), 3.3 (s,3H, OMe), 8.7
2915, 2850 (CH3), 1640 (C=N), 3450
(s,1H,=CH), 7.2-8.3 (m,4H,Ar-H), 12.2
(OH), 1630, 1595, 1580 (C=C).
Ig
(s,1H,Ar-OH).
2930, 2840 (CH3), 3450 (OH), 1655
(C=N), 1620, 1600, 1590 (C=C).
1660 (C=N) 1625, 1535, 1460
(C=C), 1050 (C-O-C).
1665 (C=N), 1630, 1535, 1490,
(C=C), 1020, (C-O-C).
3.2 (s,3H,OMe), 8.4 (s,1H,=CH), 7.4-8.1
(m,5H,Ar-H), 12.2 (s,1H,OH).
Ih
Ii
8.2 (s,1H,=CH), 6.3-7.9 (m,5H,Ar-H).
8.2 (s,1H,=CH), 6.3-7.9 (m,5H,Ar-H).
Ij

Synthesis, Characterization and Antibacterial Activity
885
Assessment of antibacterial activity of Schiff bases
The antibacterial test was performed using the agar diffusion method of Collins et al16. The
test organisms were inoculated on nutrient agar plates and spread uniformly using a sterile
glass spreader. Wells of 5 mm in diameter were made on the nutrient agar using a sterile
cork borer. To each wells, the different concentration of different compound was introduced.
o
Ampicillin was used as control. The plates were incubated at 37 C for 24 h. The zones of
inhibition were then recorded.
Determination of minimum inhibitory concentration (MIC) of extracts
The MIC of these compounds were determined on solid medium (Nutrient agar) using the
method of Collins et al16. The range of concentration was used 3.5 to 6.5 mg/mL.
Results and Discussion
Aromatic aldehydes and substituted aromatic amines were chosen as the starting
materials. Treatment of different aromatic aldehydes with aromatic amines in solvent
methanol gave the desired Schiff bases. These Schiff bases shows IR absorption peak
at 1660-1635 cm-1 (C=N stretching). Antibacterial activity recorded in terms of average
zones of inhibition in millimeter (mm.) in Table 3. These compounds showed a range
of activity against most of the tested bacteria. The dimethyl formamide (DMF) and
dimethyl sulfoxide (DMSO) solution exhibited very strong activity against two bacteria
i.e., Dermatophillus cangolensis and staphylococcus aureus and only one compound in
DMF solution failed to exhibit any significant antibacterial activity i.e. Ig for Proteus
vulgaris and Staphylococcus aureus where as in DMSO solution Ic and Id also failed
to exhibit antibacterial activity against Actinomyces bovis. Most of the compounds
showed more activity than control Amphicillin. The MIC (Minimum inhibitory
concentration) of these compounds in both solvent against the test organisms ranged
between 3.5 to 6.5 mg/mL.
Table 3. Antibacterial activity of halo substituted Schiff bases.
DMF
Sa.
DMSO
Sa.
S. No.
Entry
Dc.
Pv.
Cp.
Ab.
Dc.
Pv.
Cp.
Ab.
+
1
2
3
+++ ++
++
++
+++ +++ ++ +++
+
++++ ++++ ++++ ++++ ++++ ++++ ++++ ++++ ++
Ia
Ib
Ic
Id
Ie
If
++
-
++++
++
++++ ++++ ++++ ++
+
++
+
++ +++ ++
+
++
++++
++
+
++
++++ ++
+++
4
+
-
5
+++ ++++ ++++ +++ ++++ ++++
6
+++
+++
+++
+
-
+
-
+
+
++++ +++ +++ ++
+
+
+
7
++
++
++ ++++ ++ ++++
+++ ++++ +++
++ ++++ +++ +++ +++ ++
+
+
Ig
Ih
Ii
8
9
10
+
++
+
+++ +++ +++ +++
+++ ++ +++
+
++ +++ ++ ++++
+++ +++ ++ +++ ++
+
+
++
Ij
Control Ampicillin +++ +++ +++ ++
# DMF= Dimethyl formamide, # DMSO=Dimethyl sulfoxide, # Dc= Dermatophilus congolensis, # Pv
=Proteus vulgaris, # Sa= Staphylococcus aureus, # Cp= Corynebacterium parvum. # Ab=
Actinomyces bovis. = No inhibition, + = 5-10 mm diameter of zone of inhibition. ++ = 10-15 mm
diameter of zone of inhibition. +++ = 15-20 mm. diameter of zone of inhibition. ++++ = 20-25 mm
diameter of zone of inhibition. +++++ = 25-30 mm diameter of zone of inhibition.

886
S.B. JUNNE et al.
Acknowledgments
The authors are thankful to Principal, Yeshwant Mahavidyalaya, Nanded for providing
1
laboratory facilities and the Director of IICT, Hyderabad for providing IR, HNMR spectra.
The authors are also thankful to Western Regional office U.G.C, Pune for providing
financial support (Project file no.47-876/09).
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