Coordination chemistry and bioactivity of some metal complexes containing two isomeric bidentate NS schiff bases derived from S-benzyldithiocarbazate and the x-ray crystal structures of S-benzyl-β-N-(5-methyl-2-furylmethylene)dithiocarbazate and bis[S-benzyl-β-N-(2-furylmethylketone)dithiocarbazato]cadmium(II)

Article abstract of DOI:10.1016/S0277-5387(02)01272-X

Isomeric bidentate ligands having nitrogen-sulfur donor sequence were prepared by condensing S-benzyldithiocarbazate (SBDTC) with 5-methyl-2-furyladehyde (NS) and 2-furylmethylketone (NS′). Complexes of these ligands with lead, tin, iron, cobalt and cadmium gave complexes of [M(L)₂] (M = Pb, Fe and Cd) and [M(L)₂] Cl_n (M = Sn, n = 2 and Co, n = 1) (L = NS and NS′). The compounds have been characterized by spectroscopic studies (infrared, ¹H NMR and electronic spectra). X-ray crystallographic analysis of S-benzyl-β-N-(5-methyl-2-furylmethylene)dithiocarbazate shows the presence of two independent molecules in the asymmetric unit. The molecule adopts a trans-cis configuration, as was observed in other analogues, such as SBDTC where the furylmethylene and benzyl groups are trans and cis about the N-C and C-S bonds, respectively. The molecular structure of bis[S-benzyl-β-N-(2-furylmethylketone)dithiocarbazato]cadmium(II) shows a tetrahedral geometry about the central cadmium atom with the bidentate ligand coordinating through the thioketo sulfur and the azomethine nitrogen atoms. The lead(II) complex of the NS ligand was highly cytotoxic against leukemic cells (CEM-SS) with a CD₅₀ of 3.25 μg cm^-3 while antimicrobial screening showed that the [Fe(NS)₂] Cl₂·H₂O complex was effective against Aspergillus achraceous.

Full text of DOI:10.1016/S0277-5387(02)01272-X

Polyhedron 21 (2002) 2691ꢁ2698
/
www.elsevier.com/locate/poly
Coordination chemistry and bioactivity of some metal complexes
containing two isomeric bidentate NS Schiff bases derived from
S-benzyldithiocarbazate and the X-ray crystal structures of
S-benzyl-b-N-(5-methyl-2-furylmethylene)dithiocarbazate and
bis[S-benzyl-b-N-(2-furylmethylketone)dithiocarbazato]cadmium(II)
M.T.H. Tarafder a,1, Teng-Jin Khoo a, Karen A. Crouse a,ꢀ, A.M. Ali b, B.M. Yamin c,
H.-K. Fun d
a Department of Chemistry, University Putra Malaysia, 43400 Serdang, Selangor, Malaysia
b Department of Biotechnology, University Putra Malaysia, 43400 Serdang, Selangor, Malaysia
c School of Chemical Sciences and Food Technology, University Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia
d X-ray Crystallography Unit, School of Physics, University Sains Malaysia, 11800 Minden, Penang, Malaysia
Received 15 May 2002; accepted 9 October 2002
Abstract
Isomeric bidentate ligands having nitrogenꢁ
(SBDTC) with 5-methyl-2-furyladehyde (NS) and 2-furylmethylketone (NS?). Complexes of these ligands with lead, tin, iron, cobalt
and cadmium gave complexes of [M(L)2] (MꢂPb, Fe and Cd) and [M(L)2]Cln (MꢂSn, nꢂ2 and Co, nꢂ1) (LꢂNS and NS?). The
/sulfur donor sequence were prepared by condensing S-benzyldithiocarbazate
/
/
/
/
/
1
compounds have been characterized by spectroscopic studies (infrared, H NMR and electronic spectra). X-ray crystallographic
analysis of S-benzyl-b-N-(5-methyl-2-furylmethylene)dithiocarbazate shows the presence of two independent molecules in the
asymmetric unit. The molecule adopts a trans ꢁ/cis configuration, as was observed in other analogues, such as SBDTC where the
furylmethylene and benzyl groups are trans and cis about the Nꢀ
/
C and CꢀS bonds, respectively. The molecular structure of bis[S-
/
benzyl-b-N-(2-furylmethylketone)dithiocarbazato]cadmium(II) shows a tetrahedral geometry about the central cadmium atom with
the bidentate ligand coordinating through the thioketo sulfur and the azomethine nitrogen atoms. The lead(II) complex of the NS
ligand was highly cytotoxic against leukemic cells (CEM-SS) with a CD50 of 3.25 mg cmꢃ3 while antimicrobial screening showed
that the [Fe(NS)2]Cl2×
/
H2O complex was effective against Aspergillus achraceous.
# 2002 Elsevier Science Ltd. All rights reserved.
Keywords: Schiff base ligands; Cadmium(II) complexes; Crystal structures; Dithiocarbazate Schiff base crystal structures; Metal complexes;
Bioactivity
1. Introduction
warrant further study because they provide an interest-
ing series of ligands whose properties can be greatly
modified by introducing different organic substituents,
thereby giving variation in donor properties. These
ligands interact with metal ions to give structures of
different geometry and properties and they are often
biologically active [2,3]. To date, reports of the biologi-
Considerable interest has been shown in metal com-
plexes of thiocarbazate derivatives especially those
having NNS donor sequences [1]. These compounds
cal properties of these metalꢁ
are still lacking since previous studies concentrated on
synthesis and characterization [4ꢁ6]. Furthermore, lim-
ited studies have been done on ligands having ONS
donor sequences [7,8]. Therefore, as part of our ongoing
/
dithiocarbazato complexes
ꢀ Corresponding author. Tel.: ꢄ
35380
E-mail address: crouse@pc.jaring.my (K.A. Crouse).
/
603-894-66788; fax: ꢄ603-894-
/
/
1
Present address: Department of Chemistry, Rajshahi University,
Rajshahi 6205, Bangladesh.
0277-5387/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved.
PII: S 0 2 7 7 - 5 3 8 7 ( 0 2 ) 0 1 2 7 2 - X

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M.T.H. Tarafder et al. / Polyhedron 21 (2002) 2691ꢁ2698
/
study on ligands derived from S-benzyldithiocarbazate
(SBDTC), we report herein the synthesis, characteriza-
tion and bioactivity of some transition metal (Fe2ꢄ and
Co2ꢄ) and non-transition metal (Cd2ꢄ, Pb2ꢄ and
Sn2ꢄ) complexes of isomeric nitrogenꢁ
sulfur donor
/
ligands formed between SBDTC with 5-methyl-2-fur-
aldehyde (NS), (Fig. 1) and 2-furaldehyde (NS?), (Fig.
2). The structures of S-benzyl-b-N-(5-methyl-2-furyl
methylene)dithiocarbazate, NS, free ligand and bis[S-
benzyl-b-N-(2-furylmethylketone) dithiocarbazato] cad-
mium(II), [Cd(NS?)2], as determined by X-ray analysis
of single crystals are also given.
Fig. 2. Chemical structure of S-benzyl-b-N-(2-furylmethylketone)
dithiocarbazate.
bath. The product was isolated and washed with
ethanol. It was dried in a vacuum desiccator over
P2O5. The metal salts used were SnCl2, FeCl3, CoCl2,
Pb(CH3COO)2×
/
3H2O and Cd(CH3COO)2×
/2H2O.
2. Experimental
2.4. Physical measurements
All chemicals and solvents were of analytical grade
and were used as received.
The analyses for carbon, hydrogen, nitrogen and
sulfur were carried out using a LECO CHNS-932
instrument. The IR spectra in KBr pellets were recorded
2.1. Preparation of S-benzyldithiocarbazate (SBDTC)
using a Perkinꢁ
/
Elmer FT IR 1750X spectrophotometer
400 cmꢃ1). The molar conductance of 10ꢃ3
SBDTC was prepared as previously reported [9].
(4000ꢁ
/
M
solutions of the metal complexes in dimethyl sulfoxide
(DMSO) were measured at 29 8C using a Jenway 4310
conductivity meter and a dip-type cell with platinized
electrode. Magnetic susceptibilities at room temperature
were measured using a Sherwood Scientific MSB-
2.2. General method for synthesizing Schiff bases
A solution of SBDTC (1.98 g, 0.1 mol) in absolute
ethanol (40 cm3) was added to an equimolar solution of
5-methyl-2-furyladehyde or 2-furylmethylketone in 50
cm3 of the same solvent. The mixture was heated on a
steam bath for 10 min and then cooled to 0 8C in an ice
bath. Precipitated Schiff bases were filtered, washed
with cold ethanol and dried in vacuo over silica gel. The
yield and melting point were recorded for each product.
AUTO magnetic susceptibility balance. The UVꢁ
spectra were run on a Shimadzu UV-2501 PC Recording
Spectrophotometer (900ꢁ200 nm). All these measure-
/
Vis
/
ments were done at the Chemistry Department, UPM.
2.5. X-ray structure determination of NS and
[Cd(NS?)2]
2.3. General method for synthesis of metal complexes
Schiff base (0.0076 mol) prepared as outlined in
Section 2.2 was dissolved in ethanol (50 cm3) in the
presence of an equimolar amount of potassium hydrox-
ide (0.4 g). The clear solution was treated with a solution
containing a stoichiometric amount of metal salt in the
Beautiful dark-yellow crystals of the NS ligand and
[Cd(NS?)2] complex were formed after the DMF solu-
tions were allowed to slowly evaporate for a few weeks.
A selected crystal was mounted on a SMART CCD
diffractometer in each case. Reflection data were
same solvent (Â
/
50 cm3). The mixture was heated at
salt
measured at 20 8C using graphite monochromated Mo
90 8C for 5 min and subsequently cooled in an iceꢁ
/
˚
0.71073 A) radiation with a detector distance of
Ka (lꢂ
/
4 cm and swing angle of ꢃ358. The collected data were
/
reduced using the program SAINT [10] and an empirical
absorption correction was carried out using SADABS
[11]. The structure was solved by direct methods and
refined by using the full-matrix least-squares method on
F2obs using the SHELXTL [12] software package. All non-
H atoms were anisotropically refined. The hydrogen
atoms were located by difference syntheses and refined
isotropically. The molecular graphics were created using
SHELXTL. Atomic scattering factors and anomalous
dispersion correction were taken from the International
Table for X-ray Crystallography [13].
Fig. 1. Chemical structure of S-benzyl-b-N-(5-methyl-2-furylmethy-
lene) dithiocarbazate.

M.T.H. Tarafder et al. / Polyhedron 21 (2002) 2691ꢁ
/2698
2693
2.6. Target microorganisms
Cytotoxicity was expressed as CD50, i.e. the concen-
tration that reduced the absorbance of treated cells by
50% with reference to the control (untreated cells).
Doxorubicin and tamoxifen were used as control
cytotoxins.
Eight pathogenic microbials were used to test the
biological potential of the ligands and their complexes.
They were Methicillin resistant sthaphylococcus
(MRSA), Bacillus subtilis wild type (B29), Subtilis
mutant (mutant defective DNA repair-B28), Pseudomo-
nas aeruginosa (60690), Candida albicans (C.A.), Asper-
gillus ochraceous (398), Saccaromyces ceciricaee (20341)
and Candida lypolytica (2075).
3. Results and discussion
The physical and analytical data for the metal
complexes are given in Table 1. All the analytical data
obtained are in agreement with the proposed empirical
formulae. The characterized ligands are soluble in all
organic solvents tested and all compounds are stable in
air. For both the NS and NS? free ligands, the physical
and analytical data have been reported earlier [17].
2.6.1. Qualitative antimicrobial assay
Antimicrobial activity of each sample was qualita-
tively determined by a modified disc diffusion method as
previously reported [14]. Antimicrobial activity was
indicated by the presence of clear inhibition zones
around the discs. Commercially available streptomysin
(Sigma, USA) was used for antibacterial control while
nystatin (Sigma, USA) was used as antifungal control.
3.1. Infrared spectra
Major vibration bands of the free ligands and metal
complexes are given in Table 2. For complexation to
2.6.2. Quantitative antimicrobial assay
occur, the free ligand must exibit thiolꢁ
which is brought about by the presence of thioamide ꢀ
S) band at
/
thione tautomers
Compounds that showed positive (ꢀ15 mm) anti-
/
/
microbial activities with the disc diffusion assay were
subjected to the broth dilution method for the quanti-
tative measurement of microbiostatic (inhibitory) activ-
ity as described by Hufford and Clark [15]. The lowest
concentration that completely inhibited visible microbial
growth was recorded as the minimum inhibitory con-
centration (MIC, mg cmꢃ3). Both streptomycin and
nystatin were used as positive controls for bacteria and
fungi, respectively.
NHꢀ
/
Cꢁ
/
S functional group [18,19]. The n(Cꢁ
/
1096 cmꢃ1 and the n(NH) band at approximately 3150
cmꢃ1 were present, indicating that the free ligands
remain as the thione tautomer in the solid state. The
n(NH) band present in the free ligand was not observed
in any metal complex, indicating deprotonation of the
ligand in situ to form the thiol tautomers for the
formation of metal complexes to take place.
The n(Cꢁ
/
S) bands at 1096 and 1026 cmꢃ1 for NS and
NS? free ligand were also not observed in the metal
complexes, thus supporting the suggestion of coordina-
tion through the thione sulfur. Sharp bands observed in
the spectrum of the free ligand at approximately 1600
2.6.3. Cytotoxic assay
The CEM-SS (Human T-lymphoblastic leukemia) cell
line was obtained from the National Cancer Institute,
USA. The cells were cultured in RPMI-1640 medium
supplemented with 10% fetal calf serum. Cytotoxicity
was determined using the microtitration of 3-(4,5-
dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide
(MTT) assay (Sigma, USA) as reported by Mosmann
[16]. Controls that contained only cells were included for
each sample.
cmꢃ1 are assigned to n(Cꢁ
/N) [20]. In the metal
complexes this absorption was shifted to lower frequen-
cies indicating coordination of the azomethine nitrogen
to the central metal atoms [21,22]. The lowering in
frequency of the n(Nꢀ
/
N) band in all the metal
complexes is another clear indication that the coordina-
tion involves azomethine nitrogen. There was no
Table 1
Analytical data and physical properties of NS and NS? complexes
Compound
Color
M.p. (8C)
Found (Calc.) (%)
Yield (%)
C
H
N
S
[Pb(NS)2]×H2O
[Sn(NS)2]Cl2×2H2O
[Fe(NS)2]Cl2×H2O
[Co(NS)2]×Cl
[Pb(NS?)2]
yellow
198.0
172.0
173.5
222.0
228.0
217.0
41.79(41.83)
41.69(41.81)
51.25(51.55)
54.70(52.75)
42.65(42.79)
48.94(48.67)
3.66(3.24)
3.23(3.73)
4.18(4.29)
4.18(4.38)
3.59(3.31)
3.85(3.77)
6.99(6.97)
6.99(6.97)
8.62(8.60)
8.94(8.80)
7.23(7.13)
8.12(8.11)
75
80
68
65
72
70
dark yellow
dark brown
brown
16.00(15.93)
19.68(19.54)
20.40(20.10)
yellow
yellow
[Cd(NS?)2]
19.17(18.54)

2694
M.T.H. Tarafder et al. / Polyhedron 21 (2002) 2691ꢁ2698
/
Table 2
Infrared spectral data (band maxima) and molar conductance
Compound
Absorption bands (frequency, cmꢃ1
)
Molar conductance (Vꢃ1 cm2 molꢃ1
)
Ion ratio
n(NH) n(CꢁN) n(CꢁS) n(NꢀN)
n(CꢀOꢀC)
NS
NS?
3102
3200
1618
1600
1612
1612
1592
1598
1584
1590
1096
1026
1023
1062
934
936
962
962
990
998
1232 [17,24]
1232 [17,24]
1234
[Pb(NS)2]×H2O
[Sn(NS)2]Cl2×2H2O
[Fe(NS)2]Cl2×H2O
[Co(NS)2]×Cl
[Pb(NS?)2]
18
85
88
20
22
20
1234
1236
2:1
2:1
1230
1230
[Cd(NS?)2]
1230
[Sn(NS)2]Cl2 ×H2OꢄDMSO
0 [Sn(NS)2](DMSO)2 ×H2Oꢄ2Clꢃ
and
significant displacement of the frequency of the ring
breathing and n(CꢀOꢀ
C) vibrations at 1230 cmꢃ1 [7]
and no presence of metal oxygen bond stretching
observed at 440ꢁ
450 cmꢃ1 [8] in any complex. This
shows that there was no coordination by the furanic
oxygen. Indeed there is no indication of oxygen bonding
to the central metal atom in the crystal structure of the
[Cd(NS)2] complex.
/
/
/
[Fe(NS)2]Cl2 ×H2OꢄDMSO
0 [Fe(NS)2](DMSO)2 ×H2Oꢄ2Clꢃ
The electronic spectrum of the [Co(NS)2] complex
displays two diagnostic absorptions at 393 and 339 nm
1
1
corresponding to A1g0
/
1T1g and A1g0
/
1T2g transi-
tions. The remaining compounds showed bands that are
3.2. Magnetic and conductivity data and electronic
spectra
caused by charge transfer.
3.3. Crystal structure studies
At room temperature, magnetic susceptibility (Table
3) measurements show that all the complexes are
3.3.1. Crystal structure of NS (see Table 6)
diamagnetic and low spin except for [Fe(NS)2]Cl2×
/
H2O
A perspective view of the ligand with the numbering
scheme is shown in Fig. 3. The relevant bond distances
and bond angles are given in Table 7. The asymmetric
unit consists of two independent S-benzyl-b-N(5-meth-
yl-2-furylmethylene)dithiocarbazate molecules. The
methylfurylmethylenedithiocarbazate moiety of the
two molecules are not exactly planar. The methylfuryl
which has paramagnetic properties with meff of 1.77
B.M., characteristic of a square planar structure. All the
diamagnetic complexes are four-coordinated and ex-
pected to be distorted tetrahedral, as proved for our
cadmium complex by its crystal structure. For the
iron(II) ion which has a 3d6 electron configuration, the
magnetic moment (1.77 B.M.) suggests that the iron(II)
ion is in a low-spin iron(II) state.
plane of (O1ꢀ
C14 atom deviated by only ꢃ
makes a dihedral angle of 11.33(9)8 with the S1ꢀ
N1ꢀN2ꢀC7ꢀC8 plane. Similarly, in the second mole-
cule the methylfuryl O2ꢀC24ꢀC25ꢀC26ꢀC27ꢀC28 is
planar with maximum deviation of 0.04(2) A at the C28
/
C10ꢀ
/
C11ꢀ
/
C12ꢀ
/
C13ꢀ
0.030(3) A. This plane
S2ꢀ
/
C9) is planar with
˚
/
The complexes [Sn(NS)2]Cl2×
/
H2O and [Fe(NS)2]Cl2×
/
/
/
H2O exhibit molar conductance values corresponding to
2:1 electrolytes in DMSO. The conductivity presumably
arises from solvation according to the following scheme:
/
/
/
/
/
/
/
/
˚
Table 3
UVꢁVis spectral of band maxima (l, nm (log o )) and magnetic susceptibility of metal complexes
/
a
Compound
lmax (nm)
meff (B.M.)
[Pb(NS)2]×H2O
[Sn(NS)2]Cl2×2H2O
[Fe(NS)2]Cl2×H2O
[Co(NS)2]×Cl
[Pb(NS?)2]
355.5(4.817), 588.0(4.738)
diamagnetic
diamagnetic
1.77
357.5(4.821), 295.5(4.056), 585.0(1.523)
354.5(6.045), 418.0(5.574), 587.0(5.097)
339.0(4.402), 393.0(4.385)
diamagnetic
diamagnetic
diamagnetic
303.5(4.434), 347.5(4.569)
307.5(4.320), 359.5(4.420)
[Cd(NS?)2]
Beer’s law: Aꢂobc where A, absorption, bꢂ1 cm and c, concentration (M), log o (cmꢃ1 molꢃ1 l) are given in parentheses.
a
Tetrahedral complex, 1.94ꢁ
/
2.00 B.M.; distorted square-planar, 1.90ꢁ
/
1.93 B.M.; square-planar, 1.85ꢁ1.89 B.M.
/

M.T.H. Tarafder et al. / Polyhedron 21 (2002) 2691ꢁ
/2698
2695
Fig. 5. Packing arrangement of [Cd(NS?)2].
˚
bond distances of 1.3820(16) and 1.3824(17) A are
slightly shorter than the corresponding bond lengths in
˚
unsubstituted SBDTC (1.406(3) A) [24] due to the
delocalised electrons of the furan ring. The two mole-
cules are connected by hydrogen bondings, N1ꢀ
/
Fig. 3. Molecular structure and atom numbering scheme of (NS).
˚
H1AÁ Á ÁS4 ( H1AÁ Á ÁS4 2.578 A) and N3ꢀH3AÁ Á ÁS2 (
/
˚
H3AÁ Á ÁS2 2.589 A), and therefore, are arranged as
dimers parallel to the b and c axes in the lattice.
atom. However, the S3ꢀ
plane showed large deviation from the planar S3ꢀ
C21ꢀC22 group at the S4 and N4 atoms of 0.126(1) and
0.119(1) A, respectively. The dihedral angle between
the methylfurfuryl O2ꢀC24ꢀC25ꢀC26ꢀC27ꢀC28 plane
and S3ꢀN3ꢀC21ꢀC22 is 6.41(16)8 which is smaller than
in the first molecule. The phenyl ring C1ꢀC2ꢀC3ꢀC4ꢀ
C5ꢀC6ꢀC7 is nearly perpendicular to the methylene-
dithiocarbazate S1ꢀS2ꢀN1ꢀN2ꢀC7ꢀC8 of 80.21(6)8.
In the second molecule, the phenyl ring C15ꢀC16ꢀ
C17ꢀC18ꢀC19ꢀC20 makes dihedral angle of
74.12(9)8 with the S3ꢀN3ꢀC21ꢀC22 plane.
The C8ꢀS2 and C22ꢀS4 bond lengths in the two
molecules of 1.6669(15) and 1.6667(15) A, respectively,
/
S4ꢀ
/
N3ꢀ
/
N4ꢀ
/
C4ꢀ
/
C5ꢀ
/
C6ꢀ
/
C7
/
N3ꢀ
/
/
˚
ꢃ
/
3.3.2. Crystal structure of the [Cd(NS?)2] complex
The molecular structure of the [Cd(NS?)2] complex is
shown in Fig. 4, while Fig. 5 shows the packing
arrangement of the molecules on the ac plane. The
central cadmium atom is bis-chelated by the uninega-
tively charged bidentate ligand through the azomethine
nitrogen atoms, N2 and N4, and the thiolate sulfur
atoms, S2 and S3. Both nitrogen atoms (N2, N4) and
sulfur atoms (S2 and S3) from the two ligands are
coordinated at opposite positions. The formation of this
complex gives a distorted tetrahedral geometry about
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
a
/
/
/
/
/
˚
˚
are intermediate between 1.82 A for Cꢀ
/
S single bond
the central cadmium atom with angles of 78.89(10)8ꢁ
/
˚
and 1.56 A for Cꢁ
/
S double bond [23] and is in
137.72(11)8. The bond lengths of the complex are
comparable to the analogous complex bis[S-benzyl-b-
N(5-methyl-2-furylmethylene)dithiocarbazato]cadmiu-
m(II) reported earlier [17]. Both complexes show non-
participation of the furanic oxygen in the coordination
to the central cadmium atom. This observation, how-
ever, is in contrast to the one proposed by Jouad et al.
[25]. There is slight variation in corresponding bond
agreement with the reported value in SBDTC [24].
Thus, the compound exits as a thioketo tautomeric
form. The furylmethylene and benzyl groups are trans
and cis with respect to the ion about the the Cꢀ
CꢀS bonds, respectively. A similar configuration was
also reported for SBDTC [24]. The N1ꢀN2 and N3ꢀN4
/
N and
/
/
/
lengths in the C9ꢀ
N3ꢀC22ꢀS4ꢀC21 moieties in the complex. The largest
variation is shown by the C9ꢀC10 and C23ꢀC24 of
1.466(6) and 1.419(7) A, respectively. The C8ꢀN1 and
/
N2ꢀ
/
N1ꢀ
/
C8ꢀ
/
S1ꢀ
/
C17 and C23ꢀ
/
N4ꢀ
/
/
/
/
/
/
˚
/
˚
N3 bond lengths of 1.257(6) and 1.300(7) A clearly
C22ꢀ
/
indicate the complexation involves deprotonation at N1
and N3 atoms of the ligand. The conjugation system of
the moieties is influenced by the coordination with the
metal as shown by the slight bond lengthenings com-
pared with the uncomplexed ligand. The N1ꢀ
N3ꢀN4 distances of of 1.424(5) and 1.417(5) A are
slightly longer than the normal values of about 1.36ꢁ
/
N2 and
˚
/
/
Fig. 4. Molecular structure and atom numbering scheme of
[Cd(NS?)2].
˚
1.38 A [22,26]. The corresponding bond lengths in

2696
M.T.H. Tarafder et al. / Polyhedron 21 (2002) 2691ꢁ2698
/
octahedral
methylene)dithiocarbazato]zinc(II) are 1.379(4) and
tridentate
bis[S-benzyl-b-N(2-pyridyl-
Table 4
Results of screening against leukemic cells (CEM-SS)
˚
1.374(4) A, respectively [1]. The cadmium atom makes
a linear plane with the furyl groups Cd1ꢀO1ꢀN1ꢀN2ꢀ
C9ꢀC10ꢀC11ꢀC12ꢀC13ꢀC14, with maximum devia-
tion of 0.048(4) A at C11, and Cd1ꢀO2ꢀN3ꢀN4ꢀC23ꢀ
C24ꢀC25ꢀC26ꢀC27 with maximum deviation of
0.032(7) A at N4, respectively. The cadmium-bidentate
rings are less planar. The Cd1ꢀS2ꢀN1ꢀN2ꢀC8 has a
minimum deviation of 0.085(5) A at the N1 atom and
a
Compound
CD50 (mg cmꢃ3
)
CEM-SS
/
/
/
/
[Fe(NS)2]Cl2×H2O
[Sn(NS)2]Cl2×2H2O
[Co(NS)2]×Cl
[Pb(NS)2]×H2O
[Cd(NS?)2]
ꢁ/
29
/
/
/
/
/
˚
/
/
/
/
/
ꢁ/
3.25
/
/
/
˚
ꢁ/
29.7
/
/
/
/
[Pb(NS?)2]
˚
Metal salts
SnCl2
˚
maximum deviation of 0.181(4) A at the S4 atom. For
the Cd1ꢀS3ꢀN3ꢀN4ꢀC22 plane the minimum devia-
tion is 0.096(5) A at the N3 atom and the maximum
ꢁ/
ꢁ/
ꢁ/
12.00
14.00
FeCl2
PbNO3
CoCl3
/
/
/
/
˚
˚
deviation is 0.219(9) A at the N4 atom. The dihedral
angles between the planar benzyl planes C1ꢀC2ꢀC3ꢀ
C4ꢀC5ꢀC6ꢀC7 and C15ꢀC16ꢀC17ꢀC18ꢀC19ꢀC20ꢀ
C21 with their corresponding furyl planes O1ꢀC10ꢀ
C11ꢀC12ꢀC13ꢀC14 (maximum deviation at C9,
0.021(5) A) and O2ꢀC32ꢀC24ꢀC25ꢀC26ꢀC27 (max-
CdBr2
/
/
/
Standard
/
/
/
/
/
/
/
/
/
Doxorubicin
Tamoxifen
0.10
36.00
/
/
/
/
/
ꢁ, inactive.
/
˚
/
/
/
/
/
CD50 (mg cmꢃ3), cytotoxic dose at 50%, i.e. the concentration to
reduce growth of cancer cells by 50%.
a
˚
imum deviation at C24, 0.047(6) A) are quite different
with values of 83.9(4)8 and 67.7(4)8, respectively. The
intramolecular
interaction
˚
of
C14ꢀ
/
H14AÁ Á ÁN1
remainder of the complexes investigated do not possess
any significant activity against CEM-SS, with the
(H14AÁ Á ÁN1, 2.259 A) and C28ꢀ
/
H28AÁ Á ÁN3
˚
(H28AÁ Á ÁN3, 2.248 A) result in the formation of six-
membered rings in the ligand moieties and may con-
tribute to the planarity of the furyl-Schiff base group of
the complex.
exception of [Sn(NS)2]Cl2×2H2O and [Pb(NS?)2] com-
/
plexes which are toxic at higher concentrations. Detailed
results against CEM-SS cell lines are shown in Table 4.
3.4.2. Antimicrobial assay
3.4. Biological activity
Preliminary screening for antimicrobial activity was
done on all compounds. All the compounds showed
clear inhibition zones of 10 mm and above against A.
3.4.1. Cytotoxic activity
PbNO3 salt is inactive, but chelation by the NS is
active, but chelation by Nsfree ligand gives [Pb(NS)2]×
ochraceous
except
H2O was active against A. ochraceous
the
[Cd(NS?)2]
complex.
/
[Fe(NS)2]Cl2×
/
H2O complex of high cytoxicity against CEM-SS with a
CD50 of 3.25 mg cmꢃ1. Most of our recent research on
cadmium(II) complexes [17] showed high cytotoxic
activity on all of the cell lines, but the activity of the
[Cd(NS?)2] complex was greatly reduced and was even
much lower than the simple cadmium(II) salt. The
with a clear inhibition zone of 21 mm. The qualitative
screening results are shown in Table 5.
Only [Fe(NS)2]Cl2×/H2O was used for quantitative
measurement of MIC. Its MIC value of 100 000 mg
cmꢃ3 towards A. ochraceous is higher than that for the
standard drug nystatin (3125 mg cmꢃ3).
Table 5
Qualitative antimicrobial assay results (diameter in mm)
a
Compound
MRSA
B29
B28
60690
8
C.A.
13.5
398
20341
11
2075
11
[Fe(NS)2]Cl2×H2O
[Pb(NS)2]×H2O
[Sn(NS)2]Cl2×2H2O
[Cd(NS?)2]
[Pb(NS?)2]
Streptomysin (antibacterial control)
8
7
8
8
8
7
9
21
12
12
8
ꢁ/
8
ꢁ/
ꢁ/
ꢁ/
8
11
ꢁ/
ꢁ/
ꢁ/
8
8
11
7
ꢁ/
8
31
ꢁ/
7
30
ꢁ/
8
30
ꢁ/
8
30
12
ꢁ/
ꢁ/
ꢁ/
ꢁ/
ꢁ/
Nystatin (antifungal control)
ꢁ/
ꢁ/
ꢁ/
ꢁ/
21
25
24
27
Methicillin resistant sthaphylococcus (MRSA); Bacillus subtilis wild type (B29); Subtilis mutant (mutant defective DNA repair-B28); P. aeruginosa
(60690); C. albicans (C.A); A. ochraceous (398); S. ceciricaee (20341); C. lypolytica (2075); ‘ꢁ’, inactive.
Diameter of 15 mm and above considered active.
/
a

M.T.H. Tarafder et al. / Polyhedron 21 (2002) 2691ꢁ
/2698
2697
Table 6
Summary of crystal data and structure refinement parameters for NS
Table 7
˚
Selected bond lengths (A) and bond angles (8) for NS and [Cd(NS?)2]
and [Cd(NS?)2
NS
[Cd(NS?)2]
Compound
NS
C14H14N2OS2
290.39
[Cd(NS?)2]
C28H26CdN4O2S4
691.17
Bond lengths
S(1)ꢀC(8)
S(1)ꢀC(7)
S(2)ꢀC(8)
S(3)ꢀC(22)
S(3)ꢀC(21)
S(4)ꢀC(22)
N(1)ꢀC(8)
N(1)ꢀN(2)
N(2)ꢀC(9)
N(3)ꢀC(22)
N(3)ꢀN(4)
N(4)ꢀC(23)
Chemical formula
Formula weight
Crystal class
1.7506(14)
1.8197(17)
Cd(1)ꢀN(4)
Cd(1)ꢀN(2)
2.285(4)
2.315(4)
2.4813(13)
2.4827(13)
1.770(5)
1.812(6)
1.747(6)
1.755(6)
1.730(5)
1.837(6)
1.257(6)
1.424(5)
1.261(6)
1.300(7)
1.417(5)
1.292(7)
Monoclinic
P21/n
triclinic
¯
1.6669(195) Cd(1)ꢀS(2)
Space group
˚
P
/1/
1.7528(15)
1.8149(18)
1.6667(15)
1.3348(19)
1.3820(16)
1.275(2)
Cd(1)ꢀS(3)
S(1)ꢀC(8)
S(1)ꢀC(7)
S(2)ꢀC(8)
S(3)ꢀC(22)
S(4)ꢀC(22)
S(4)ꢀC(21)
N(1)ꢀC(8)
N(1)ꢀN(2)
N(2)ꢀC(9)
N(3)ꢀC(22)
N(3)ꢀN(4)
N(4)ꢀC(23)
a (A)
˚
9.7144(2)
23.26670(10)
12.93790(10)
90
10.5620(2)
10.5926(2)
14.9458(3)
95.377(1)
93.468(1)
114.156(1)
1509.97(5)
2
b (A)
˚
c (A)
a (8)
b (8)
g (8)
97.2500(10)
90
3
˚
1.337(2)
1.3824(17)
1.285(2)
V (A )
2900.87(7)
8
Z
˚
Mo Ka (A)
T (K)
0.71073
293(2)
1.330
0.71073
293(2)
rcalc (Mg mꢃ3
)
1.520
1.032
m (mmꢃ1
)
0.360
0.48ꢅ0.46ꢅ0.42
Sample dimension
(mm)
F(000)
0.46ꢅ0.34ꢅ0.32
Bond angles
1216
19 747
700
10 658
C(8)ꢀS(1)ꢀC(7)
C(22)ꢀS(3)ꢀC(21)
C(8)ꢀN(1)ꢀN(2)
C(9)ꢀN(2)ꢀN(1)
C(10)ꢀO(1)ꢀC(13) 106.65(15)
C(27)ꢀO(2)ꢀC(24) 106.23(13)
C(8)ꢀN(1)ꢀN(2)
C(9)ꢀN(2)ꢀN(1)
C(22)ꢀN(3)ꢀN(4)
C(23)ꢀN(4)ꢀN(3)
C(1)ꢀC(7)ꢀS(1)
N(1)ꢀC(8)ꢀS(2)
N(1)ꢀC(8)ꢀS(1)
S(2)ꢀC(8)ꢀS(1)
N(2)ꢀC(9)ꢀC(10)
102.37(7)
101.91(8)
119.36(12)
115.86(13)
N(4)ꢀCd(1)ꢀN(2)
N(4)ꢀCd(1)ꢀS(2)
N(2)ꢀCd(1)ꢀS(2)
N(4)ꢀCd(1)ꢀS(3)
N(2)ꢀCd(1)ꢀS(3)
S(2)ꢀCd(1)ꢀS(3)
C(8)ꢀS(1)ꢀC(7)
C(8)ꢀS(2)ꢀCd(1)
C(22)ꢀS(3)ꢀCd(1)
C(22)ꢀS(4)ꢀC(21)
115.98(15)
137.20(11)
79.11(10)
78.89(10)
136.04(11)
119.26(5)
104.6(3)
Total number of
reflections collected
Independent
reflections
6962 [Rintꢂ0.0669]
7007 [Rintꢂ0.0845]
Number of data used 6962
for refinement
7007
353
119.36(12)
115.86(13)
120.74(13)
114.38(13)
106.30(10)
121.75(11)
112.96(11)
125.29(9)
Number of parameters 346
refined
Goodness-of-fit on F2 0.944
93.15(17)
93.15(17)
104.5(3)
0.970
empirical
Correction
Final R indices
empirical
R1ꢂ0.0416,
wR2ꢂ0.1090
R1ꢂ0.0643,
wR2ꢂ0.1184
0.326 and ꢃ0.265
C(10)ꢀO(1)ꢀC(13) 106.3(4)
C(27)ꢀO(2)ꢀC(24) 107.8(4)
R1ꢂ0.0716,
wR2ꢂ0.1670
R1ꢂ0.0919,
wR2ꢂ0.1845
1.259 and ꢃ1.990
[I ꢀ2s(I)]
R indices (all data)
C(8)ꢀN(1)ꢀN(2)
C(9)ꢀN(2)ꢀN(1)
C(9)ꢀN(2)ꢀCd(1)
N(1)ꢀN(2)ꢀCd(1)
C(22)ꢀN(3)ꢀN(4)
C(23)ꢀN(4)ꢀN(3)
115.3(4)
114.3(4)
131.3(3)
114.4(3)
114.6(4)
113.6(4)
121.32(15)
Largest and smallest
ꢃ3
C(11)ꢀC(10)ꢀO(1) 109.51(15)
N(3)ꢀC(22)ꢀS(4)
S(4)ꢀC(22)ꢀS(3)
˚
peak (e A
)
121.48(12)
125.23(10)
N(4)ꢀC(23)ꢀC(24) 123.11(15)
C(23)ꢀN(4)ꢀCd(1) 130.7(3)
N(3)ꢀN(4)ꢀCd(1) 115.3(3)
4. Supplementary material
Crystallographic data for the structural analyses of
NS ligand and [Cd(NS?)2] complex have been deposited
with the Cambridge Crystallographic Data Center,
CCDC 164801 and CCDC 164800. Copies of this
information may be obtained free of charge from: The
Director, CCDC, 12 Union Road, Cambridge, CB2
Priority Areas (IRPA) program (Grant No. 09-02-04-
0296).
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1EZ, UK (fax:
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