Synthesis, characterisation and biological activities of 2-methylbenzyl 2-(dipyridin-2-yl methylene) hydrazinecarbodithioate

Article abstract of DOI:10.1007/s10870-010-9907-3

A new tridentate nitrogen-sulphur Schiff base has been synthesised from the condensation of di-2-pyridylketone and a novel dithiocarbazate, S-2-methylbenzyl-dithiocarbazate (S2MBDTC). The Schiff base was characterized using various physico-chemical and sp

Full text of DOI:10.1007/s10870-010-9907-3

J Chem Crystallogr (2011) 41:491–495
DOI 10.1007/s10870-010-9907-3
ORIGINAL PAPER
Synthesis, Characterisation and Biological Activities
of 2-Methylbenzyl 2-(dipyridin-2-yl methylene)
hydrazinecarbodithioate
Thahira B. S. A. Ravoof
•
•
K. A. Crouse
•
•
M. Ibrahim M. Tahir
Fiona N. F. How
R. Rosli
David J. Watkin
•
Received: 7 May 2010 / Accepted: 17 November 2010 / Published online: 2 December 2010
Ó Springer Science+Business Media, LLC 2010
Abstract A new tridentate nitrogen–sulphur Schiff base has
been synthesised from the condensation of di-2-pyridylketone
and a novel dithiocarbazate, S-2-methylbenzyl-dithiocarbazate
and biological activities can be greatly modified by intro-
ducing organic substituents thereby inducing different
stereochemistry in the resultant metal complexes [1–12].
Ianelli et al. [13] reported the ligand behavior of related
HNNS Schiff bases, di-2-pyridyl ketone 2-aminobenzoyl
hydrazone and phenyl (2-pyridyl) ketone 2-aminobenzoylhyd-
razone towards organotin derivatives, their structural charac-
teristics and antimicrobial activities. The two ligands showed
slight antibacterial activity but di-2-pyridylketone 2-amin-
obenzoylhydrazone gave a better response than phenyl(2-pyr-
idyl) ketone 2-aminobenzoylhydrazone against Gram positive
bacteria, thus demonstrating quantitative differences related to
the presence of the pyridine or benzene ring in the cell nucleus.
Carcelli et al. [14] synthesized two organotin com-
pounds containing di-2-pyridylketone 2-thenoylhydrazone
chosen as it contains a hydrazide–hydrazone chain and a
pyridine moiety, often associated with genotoxic proper-
ties, DNA-damaging activity and mutagenicity [15].
Hence, as part of our ongoing study on dithiocarbazate
Schiff bases containing pyridine rings and their transition
metal complexes, we report herein the crystal structure of
(
S2MBDTC). The Schiff base was characterized using vari-
ous physico-chemical and spectroscopic techniques. The
X-ray crystallographic analysis of the Schiff base is repor-
ted. The Schiff base crystallized in a monoclinic system with
a space group of P 2 /n, with crystal cell parameters a =
1
1
˚ ˚ ˚
0.8128 (2) A, b = 9.3832 (2) A, c = 18.0352 (4) A,
b = 97.1311 (9)°. The Schiff base was found to be inactive
against selected microbes and two breast cancer cell lines
(MCF-7 = Human breast cancer cell line with positive estro-
gen receptor and MDA-MB-231 = Human breast cancer cell
line with negative estrogen receptor).
Keywords Dithiocarbazate Á Di-2-pyridylketone
Schiff base Á Biological activity
Introduction
Dithiocarbazic acid and its substituted derivatives continue
to receive considerable attention because their properties
2-methylbenzyl 2-(dipyridin-2-ylmethylene)hydrazinecarbod-
ithioate.
T. B. S. A. Ravoof (&) Á K. A. Crouse Á
M. I. M. Tahir Á F. N. F. How
Experimental
Department of Chemistry, Faculty of Science, Universiti Putra
Malaysia, UPM Serdang, 43400 Selangor, Malaysia
e-mail: thahira.begum@science.upm.edu.my
All chemicals and solvents were of analytical grade and
were used as received.
R. Rosli
Department of Obstetrics and Gynaecology, Faculty of Medicine
and Health Sciences, Universiti Putra Malaysia, UPM Serdang,
Preparation of S-2-Methylbenzyldithiocarbazate
4
3400 Selangor, Malaysia
(S2MBDTC)
D. J. Watkin
Chemistry Research Laboratory, Department of Chemistry,
Oxford University, Mansfield Road, OX13TA Oxford, UK
The procedure used to synthesize this new dithiocarbazate was
similar to that used in the synthesis of S-benzyldithiocarbazate
123

4
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J Chem Crystallogr (2011) 41:491–495
(
SBDTC) [16]. Potassium hydroxide (11.4 g, 0.2 mol) was
week. A crystal was mounted on a glass fibre using perflu-
oropolyether oil and cooled rapidly to 150 K in a stream of
dissolved in absolute ethanol (70 mL). To this solution,
hydrazine hydrate (10 g, 0.2 mol) was added and the mixture
was cooled in an ice-salt bath to 0 °C. Carbon disulphide
cold N using Oxford Cryosystems CYROSTREAM unit.
2
Diffraction data were collected using an Enraf–Nonius
Kappa CCD diffractometer (graphite-monochromated Mo
(
15.2 g, 0.2 mol) was added dropwise with constant stirring
˚
over a period of 1 h. The two layers that subsequently formed
were separated using a separating funnel. The light-brown
lower layer was dissolved in 40% ethanol (60 mL) below
Ka radiation, k = 0.71073 A). Intensity data were processed
using the DENZO-SMN package [17]. The structures were
solved using the direct-methods program SIR92 [18] which
located all non-hydrogen atoms. Subsequent full-matrix
least-squares refinement was carried out using CRYSTALS
Program Suite [19]. Coordinates and anisotropic thermal
parameters of all non-hydrogen atoms were refined. Hydro-
gen atoms were positioned geometrically after each cycle of
refinement. A five-term Chebychev polynomial weighting
scheme was applied.
5
°C. The mixture was kept in an ice-bath and 2-methyl-
benzyl chloride (26.5 mL, 0.2 mol) was added dropwise to it
with vigorous stirring of the mixture. The sticky white
product (S2MBDTC), which formed was filtered and left to
dry overnight in a dessicator over anhydrous silica gel.
(
Yield: 82%, m.p. 171.2 °C.)
Preparation of 2-Methylbenzyl 2-(dipyridin-2-ylmethylene)
hydrazinecarbodithioate (dpyS2M)
Bioactivity
S2MBDTC (0.01 mol) was dissolved in hot acetonitrile
Target Microorganisms
(
150 mL). This was added to an equimolar solution of
di-2-pyridylketone (0.01 mol) in ethanol (20 mL). The mix-
ture was heated and stirred for 30 min and then allowed to
stand for a fewhours. Theyellowcrystalsformedwerefiltered
off and recrystallised from acetonitrile. Yields were fairly
high, ca. 85%, m.p. 186–187 °C. Elemental analysis (Exper-
Eight pathogenic microbes were used to test the biological
potential of the complexes. They were Methicillin resistant
staphylococcus (MRSA), Bacillus subtilis wild type (B29),
Pseudomonas aeruginosa (60690), Salmonella Cholerae-
suis (S.C.) Candida albicans (C.A.), Aspergillus ochra-
ceous (398) and Saccaromyces ceciricaee (20341). The
source of microbes and culture maintenance were as pre-
viously described [20].
imental (calc.): C = 62.97 (63.46), H = 4.68 (4.79), N =
1
4.57 (14.80) and S = 17.96 (16.94). H-NMR: (DMSO-d6,
1
ppm, 14.94 (s, 1H, NH), 7.13–7.32 (multiplet, 16H, Ar–H),
1
3
4
.46 (d, 4H, –SCH ), 2.35 (s, 6H, –CH ), C-NMR:
2 3
(
DMSO-d6, ppm), 198.98 (C=S), 164.71 (C=N), 126.15–
54.49(Ar–C), 36.25(S–CH ), 18.88, 18.79(CH ). Massdata
Qualitative Antimicrobial Assay
1
2
3
?
m/z (%): [M] 378 (0.40), [C H N ] 211 (0.40),
?
Antimicrobial activity of each sample was qualitatively
determined by a modified disc diffusion method [21] as pre-
viously detailed [22]. A lawnofmicroorganisms wasprepared
1
2 12 4
?
?
?
[
C H N ] 183 (0.03), [C H S] 138 (0.22), [C H N ]
11 8 3 8 10 6 5 2
?
?
1
05 (100.0), [C H ] 91 (2.65), [C H N] 78 (4.79). Crystals
7 8 5 5
-4
3
of the dpyS2M Schiff base suitable for X-ray diffraction
analysis were obtained from acetonitrile.
by pipetting and evenly spreading inoculum (10 cm ,
5
6
3
adjusted turbidometrically to 10 –10 cfu cm (cfu: colony
forming units) on to agar set in Petri dishes, using Nutrient
agar (NA) for the bacteria and potato dextrose agar (PDA) for
fungi. Whatman No. 1 filter paper discs of 6 mm diameter
were impregnated with stock solution of the compound
Physical Measurements
The analyses for carbon, hydrogen, nitrogen and sulphur
were carried out using a LECO CHNS-932 instrument. The
IR spectra in KBr pellets were recorded on a Perkin-Elmer
-3
(100 mg cm ) and dried under sterile conditions. The dried
discs were then placed on the previously inoculated agar
surface. The plates were inverted and incubated for 24 h at
30 °C for bacteria and 37 °C for fungi. Antimicrobial activity
was indicated by the presence of clear inhibition zones around
the discs. Commercially available streptomycin (Sigma,
USA) was used for the antibacterial control while nystatin
(Sigma, USA) was used as the antifungal control.
-
1
FT IR 1750X spectrophotometer (4,000–400 cm ).
The UV–VIS spectra were run on a Shimadzu UV-2501
PC/Shimadzu UV–Vis-1650 recording Spectrophotometer
(
1,000–200 nm).
X-ray Structure Analysis of 2-Methylbenzyl
-(dipyridin-2-ylmethylene)hydrazinecarbodithioate
dpyS2M)
2
(
Quantitative Antimicrobial Assay
Yellow crystals of the Schiff base were formed after the
acetonitrile solution was allowed to slowly evaporate over a
Compounds that showed positive (diameter[15 mm) anti-
microbial inhibition with the disc diffusion assay were
1
23

J Chem Crystallogr (2011) 41:491–495
493
subjected to the broth dilution method for the quantitative
measurement of microbiostatic (inhibitory) activity as
described by Hufford and Clark [23]. The lowest concen-
tration that completely inhibited visible microbial growth
was recorded as the minimum inhibitory concentration
Results and Discussion
Spectroscopic Data
The electronic spectrum of the dpyS2M Schiff base in
DMSO exhibits an intra-ligand n ? p* band around
280 nm. The IR spectra of the ligand exhibits the m(C=N),
-
3
(MIC, lg cm ). Streptomycin and nystatin were used as
controls for bacteria and fungi, respectively.
-
1
m(N–N) and m(CSS) bands at ca. 1584, 964 and 958 cm
,
Cytotoxic Assay
respectively, which are shifted to higher or lower frequen-
cies in the spectra of the metal complexes, indicating
coordination of the ligand to the metal ions via the azo-
methine nitrogen and the thiolate sulphur atoms. The
spectra of the complexes also exhibit the weak m(NH) bands
The MCF-7 (Human breast cancer cells with positive estrogen
receptor) and MDA-MB-231 (Human breast cancer cells with
negative estrogen receptor) cell lines were obtained from the
National Cancer Institute, USA. The cells were cultured in
RPMI-1640/DMEM (High glucose) (Sigma) medium sup-
plemented with 10% fetal calf serum, Cytotoxicity was
determined using the microtitration of 3-(4,5-dimethylthia-
zol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay
-
1
of the dpyS2M Schiff base at 3,052 cm
.
X-ray Crystallographic Analysis of the 2-methylbenzyl
2-(dipyridin-2-ylmethylene)hydrazinecarbodithioate
(dpyS2M)
(
Sigma, USA) as reported by Mosmann [20]. Controls that
contained only cells were included for each sample. Cyto-
toxicity was expressed as CD , i.e. the concentration that
The ORTEP diagram of the dpyS2M Schiff base with
atomic numbering scheme is shown in Fig. 1. Selected
bond lengths and bond angles are depicted in Tables 1
and 2. The dpyS2M Schiff base crystallized in a mono-
5
0
reduced the absorbance of treated cells by 50% with reference
to the control (untreated cells). Tamoxifen was used as the
standard cytotoxin.
clinic system with a space group of P 2 /n. The Schiff base
1
S26
C18
C4
C16
C19
C25
N3
N15
C24
C5
C20
S17
C23
C2
C21
N14
C1
C6
C22
C7
C8
N9
C13
C12
C10
C11
Fig. 1 ORTEP diagram of the dpyS2M Schiff base
123

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J Chem Crystallogr (2011) 41:491–495
Table 1 Crystallographic data and structure refinement details of the
dpyS2M Schiff base
example, the 2-quinolinecarboxaldehyde Schiff base of
S-methyldithiocarbazate has a C=S bond distance of 1.645
˚
A and a C–S bond distance of 1.757 A [25].
˚
Empirical formula
Formula weight
Temperature
20 18 4 2
C H N S
The C–N and C=N bond distances are 1.352 and 1.295
˚
A respectively. This was also observed in the 2-quinoli-
378.52
150 K
˚
necarboxaldehyde Schiff base of S-methyldithiocarbazate
˚
Wavelength
0.71073 A
Monoclinic
P 2 /n
[
25]. The N–N bond distance was 1.377 A, shorter than a
Crystal system
Space group
single bond, indicating significant p-charge delocalization
along the C(S)NNS moiety. The attachment of the pyridyl
groups to the imino nitrogen atoms is probably responsible
for the shortening of the N–N distance.
1
˚
Unit cell dimensions
a = 10.8128 (2) A,
˚
b = 9.3832(2) A
˚
c = 18.0352 (4) A, a = 90°,
b = 97.1311 (9)°,
c = 90°
1815.67 (7) A
Cis–trans isomerism was exhibited in the Schiff bases
around the S(NH)C=S moiety. It was observed that the
2-methylbenzyl group and the ketone moiety of the dith-
iocarbazate Schiff base were at cis and trans positions with
respect to the terminal thione S atom about the C–S and the
C–N bonds, respectively.
3
˚
Volume
Z
4
-
1
Absorption coefficient
F(000)
0.305 mm
792.000
Crystal size
0.28 9 0.60 9 0.66 mm
5–27°
-13 B h B 13
The dihedral angle between the methylbenzyl ring
C25/C19/C24/C23/C22/C21/C20/C18 and the dithiocar-
bazate chain S26/C16/N15/N14/C1/C2/C8 was 85.91°
which was almost orthogonal relative to each other. Both
pyridine rings of the di-2-pyridylketone moiety were not
planar but inclined to each other at an angle of 58.28°. The
h range for data collection
Limiting indices
-
-
12 B k B 12
23 B l B 23
Reflections collected/unique
7947/4117 (Rint = 0.0002)
values of the C–N –C angles obtained were also in
Maximum and minimum
transmission
0.83, 0.92
py
agreement with those found by other authors for pyridine-
2-carbaldehyde thiosemicarbazone (average of 122°) [26].
Any differences are attributable to different electronic
and spatial effects of the hydrogen, methyl and benzyl
groups [26].
Data/restraints/parameters
2
Goodness of fit on F
4117/0/235
0.93
Final R indices [I [ 3ri]
R = 0.048, R
w
= 0.082
-
3
˚
-0.37 and 0.38 e A
Largest difference
peak and hole
Biological Activities
˚
Table 2 Selected bond lengths (A) and bond angles (°) for the
dpyS2M Schiff base
Several factors are known to affect the biological activity
of a molecule including physicochemical properties like
solubility, chemical structure parameters such as resonance
and type of bonding, and spatial effects such as the size and
stereochemistry of the molecule [27].
Bond lengths
Bond angles
C8–N9
1.349 (2)
1.295 (2)
1.346 (2)
1.377 (2)
1.352 (2)
1.642 (2)
1.659 (1)
1.827 (1)
N14–C1–C2
125.92 (13)
117.62 (12)
120.52 (11)
125.88 (9)
106.45 (9)
C1–N14
C2–N3
C1–N14–N15
N15–C16–S26
S26–C16–S17
S17–C18–C19
Many dithiocarbazate Schiff bases and their metal
complexes have been shown to exhibit a wide range of
antimicrobial and cytotoxic activities. Small changes in
structure often lead to vast differences selectivity as well as
activity [1, 2, 12, 13, 27].
N14–N15
C16–N15
C16–S26
C16–S17
S17–C18
It was observed that the dpyS2M Schiff base in this
study was inactive against all seven microbial strains and
the two breast cancer cell lines [MCF-7 (Human Breast
carcinoma with positive estrogen receptor) and MDA-MB-
231 (Human Breast carcinoma with negative estrogen
receptor)] tested.
˚
is in the thione form with C=S bond length of 1.642 A. The
˚
value is intermediate between a C–S single bond (1.82 A)
˚
and a C=S double bond (1.56 A) [24]. The C–S single bond
˚
length is 1.659 A, which is longer than the C=S bond
˚
length but still shorter than expected (1.82 A). This is
Related Schiff bases prepared using di-2-pyridylketone
have, however, been reported to be active against certain
bacterial and fungal strains, different from those used in this
study [12, 13]. These include S-methyl-b-N-(di-2-pyridyl)
methylene dithiocarbazate which differs from the compound
possibly due to extensive conjugation over the C=N–N–C
chain and other intermolecular interactions. This was
observed in many similar dithiocarbazate Schiff bases for
1
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J Chem Crystallogr (2011) 41:491–495
495
in this study only in the absence of a single methyl group
attached to the benzyl ring which is mildly active against
S. dysenteriae, B. cercus, S. aureus and E. coli as well as
A. alternata and M. phaseolina [28].
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Acknowledgments We thank the Department of Chemistry, the
Laboratory of Molecular and Cell Biology, Institute of Biosciences
and the Molecular Genetics Laboratory, Dept of Obstetrics and
Gynaecology, Universiti Putra Malaysia, for the provision of labo-
ratory facilities and the Chemical Crystallography Lab, Oxford
University for providing X-ray crystallographic services. The research
was funded by a grant from the Ministry of Science and Environment,
Malaysia, under the Intensification of Research in Priority Areas
Scheme (IRPA grant No. 09-02-04-0296). F.N.F How wishes to thank
the Malaysian Government for the award of a National Science
Fellowship.
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