Synthesis, structures, spectroscopy and antimicrobial properties of complexes of copper(II) with salicylaldehyde N-substituted thiosemicarbazones and 2,2′-bipyridine or 1,10-phenanthroline

Article abstract of DOI:10.1016/j.ejmech.2014.02.009

Among the biometals (Cu, Co, Ni-cofactors in many enzymes), copper derivatives of O, N, S-donor salicylaldehyde thiosemicarbazones have received considerable attention owing to their potential biological applications. Eight new complexes of salicylaldehyd

Full text of DOI:10.1016/j.ejmech.2014.02.009

European Journal of Medicinal Chemistry 76 (2014) 145e154
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Synthesis, structures, spectroscopy and antimicrobial properties of
complexes of copper(II) with salicylaldehyde N-substituted
thiosemicarbazones and 2,20-bipyridine or 1,10-phenanthroline
,
a
a
b
Tarlok S. Lobana a , Shikha Indoria , Amanpreet Kaur Jassal , Harpreet Kaur ,
*
Daljit S. Arora b, Jerry P. Jasinski c
a Department of Chemistry, Guru Nanak Dev University, Amritsar 143 005, India
b Department of Microbiology, Guru Nanak Dev University, Amritsar 143 005, India
c Department of Chemistry, Keene State College, Keene, NH 03435, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
Among the biometals (Cu, Co, Ni-cofactors in many enzymes), copper derivatives of O, N, S-
donor salicylaldehyde thiosemicarbazones have received considerable attention owing to their potential
biological applications. Eight new complexes of salicylaldehyde-N-substituted thiosemicarbazones [5-
MeO-2-HOeC6H4eC2(H)]N3eN2HeC1(]S)eN1HR; R ¼ Me, H2L1; Et, H2L1, Ph, H2L3, H, H2L4] with
Received 26 July 2013
Received in revised form
6 February 2014
Accepted 7 February 2014
Available online 8 February 2014
copper(II), namely, [Cu(
k
2ꢀ3-O,N,S-L)( k2-N,N-L0)] {(L)2ꢀ ¼ (L1)2ꢀ, L0 ¼ bipy, 1, phen, 2; (L)2ꢀ ¼ (L2)2ꢀ
,
L0 ¼ bipy, 3, phen, 4; (L) ¼ (L3)2-, L0 ¼ bipy, 5, phen, 6; (L)2ꢀ ¼ (L4)2ꢀ, L0 ¼ bipy, 7, phen, 8} have been
isolated. Complexes have slightly distorted square pyramidal geometry around the metal center (
s
Keywords:
parameter ¼ 0.243e0.357) and display weak to intense fluorescence in the region, 375e475 nm. These
copper complexes have shown significant growth inhibitory activity (antimicrobial activity) against
Staphylococcus aureus (MTCC740), methicillin resistant Staphylococcus aureus (MRSA), Klebsiella pneu-
moniae 1 (MTCC109), Shigella flexneri (MTCC1457), Pseudomonas aeruginosa (MTCC741) and Candida
albicans (MTCC227). The activity against MRSA is an interesting observation as the commercially avail-
able gentamycin is found to be inactive against this bacterial strain. Specifically complex 5 formed by 5-
methoxysalicylaldehyde-N-phenylthiosemicatbazone has shown novel antimicrobial activity against
various bacteria and yeast investigated.
Copper(II)
2, 20-Bipyridine
1,10-Phenanthroline
Salicylaldehyde thiosemicarbazones
Fluorescence
Biological activity
Ó 2014 Elsevier Masson SAS. All rights reserved.
1. Introduction
coordination number/oxidation state [7e22]. The thio-ligands have
shown coordination to CuII as monoanions (HLꢀ, the deprotonation
Thiosemicarbazones represent an interesting class of thio-
ligands which have shown coordination to metals through
different donor atoms forming a variety of complexes with different
nuclearities [1]. In addition this class of thio-ligands/their com-
plexes have also shown important biological properties (antitumor,
antibiotic, antiviral), in vitro molecular imaging, metal-sensing
properties, catalytic and analytical applications [1e6]. In partic-
ular salicylaldehyde thiosemicarbazones, R1R2C2]N3eN2(H)e
C(S)eNR3R4 (Chart 1, H2L) constitute an important class of organic
molecules whose coordination chemistry with metals has received
considerable attention [1,2]. There is special interest in copper(II)-
thiosemicarbazone chemistry due to the biological applications of
complexes which can be attributed to the possibility of change in its
of eOH group) [7e11,22], or as dianions (L2ꢀ, the deprotonation of
eOH and -N2H groups) [7e9,12e22], and the geometry around CuII
center is distorted square planar or distorted trigonal bipyramidal
in mono- and di-nuclear complexes [7e22]. Several investigations
pertain to the R1 group with no ring substitution (R, R ¼ H, H, Chart
1) and with R2 ¼ H, while substitution at N1 atom is varied
[7,8,10,12e14,16,22]. There are a few reports with R2 ¼ Me and with
R1 having no ring substitution (R, R ¼ H, H, Chart 1) [15,18,19].
Further with R2 ¼ Me and R1 ring having methyl substitution at 5-
position, a phenoxy bridged dimer is reported [20]. For R2 ¼ H and
with substitution at 5 position of R1 ring (5-NO2, 5-Cl, 5-Br, 5-CH3,
5-MeO, Chart 1), only one complex (5-NO2) is structurally charac-
terized
[17].
5-Bromo-salicylaldehyde-2-methyl
thio-
semicarbazone, a related thio-ligand, also formed a square planar
complex [23]. Finally for R2 ¼ H and with double substitution of R1
ring (R, R; Cl, Cl; Br, Br; 3,5-tBu; 3-MeO, 5-Ph-N]Ne, Chart 1)
* Corresponding author.
E-mail addresses: tslasr@gmail.com, tarlokslobana@yahoo.co.in (T.S. Lobana).
http://dx.doi.org/10.1016/j.ejmech.2014.02.009
0223-5234/Ó 2014 Elsevier Masson SAS. All rights reserved.

146
T.S. Lobana et al. / European Journal of Medicinal Chemistry 76 (2014) 145e154
R2
R1
R
NR3R4
S
R1
1
C
2
NH
C2 N3
OH
H, Me
NH2, NHMe etc
N1R3R4
R2
R
Chart 1. Salicylaldehyde thiosemicarbazones, H2L.
[9,11,13] distorted trigonal bipyramidal complexes have been re-
ported [13].
Copper(II) complexes reported in literature have shown activ-
ities such as antimicrobial [9,12,15,19,21], antitumor [10,11],
photoinduced DNA cleavage [14] and oxidation of ascorbic acid in
the presence of oxygen [13]. The CuN3OS core of complexes model
occurred at 3238 cme1, which disappeared in the complex sug-
gested deprotonation of both (N2eH) and (OeH) moieties and the
ligand binding to the metal as a dianion. Complex 4 with the same
ligand H2L2 showed similar IR spectral changes corresponding to
the
n
(N1eH),
n
(N2eH) and
n
(OeH) stretching frequencies. In the IR
spectrum of free H2L4, the bands due to
n
(N1eH2), (N2eH) and
n
the ascorbate oxidation property of dopamine
b
-hydroxylase (D
b
H)
n
(OeH) occur at 3379 s, 3280 m and 3249 s(b) cmꢀ1 respectively
and peptidylglycine -hydroxylating monooxygenases (PHM) [13].
a
but in complex 7, only eN1H2 group showed bands at 3346 m,
Dinuclear complexes have shown little or no antimicrobial activity
[19,21]. It is noted that the nature of the substituents in the R1 ring
and the presence of co-ligands both have shown effect on the
biochemical properties of complexes [9e15,19,21]. Further, five
coordinated complexes with polypyridyl heterocyclic bases as co-
ligands showed enhanced antimicrobial activity due to the in-
crease of lipophilicity [12e15]. The studies described in literature
pertain to the biological activity either when complexes do not
generally have co-ligands [9e11,19,21], or when R1 ring has no
substitution but metal is coordinated to the polypyridyl bases [12e
15].
3281 m cmꢀ1. Similar behavior is noticed in complex 8. As above,
the IR bands of free ligand, H2L3 due to
n
(N2eH) and
n
(OeH) at
3396 cme1 (br) disappeared in complexes 5 and 6. Complexes 1 and
2 showed similar behavior. The (OeH) bands of CH3OH and H2O
appeared at same position, 3380 cmꢀ1 supporting their presence in
n
complexes 1 and 2. The diagnostic n(CeS) bands of free ligands lie
in the region, 1027e1031 cme1 which shifted to the range, 813e
815 cme1 in complexes (see Experimental/supplementarty for
more details). The magnetic moments of complexes [meff ¼ 1.79 (1),
1.94 (2, 8), 1.80 (3), 2.12 (4), 2.08 (5), 1.97 (6), 1.81(7) BM] suggest
the presence of CuII oxidation state in complexes.
It is noted from above that there is no systematic approach to
synthesize new compounds and hence to explore their biological
properties. It was thus considered important to adopt a systematic
approach and study the effect of substituents in the R1 ring, employ
various heterocyclic bases such as polypyridyls or related ligands
and also change substituents at N1 atom of thiosemicarbazones.
Owing to our interest in the chemistry of thiosemicarbazones with
transition metals [24e27], it was designed to react copper(II) with
salicylaldehyde N-substituted thiosemicarbazones as shown in
Chart 2 (H2L1, H2L2, H2L3, H2L4) having methoxy substitution at 5-
position as well as variable substitution at N1 atom. The 2,20-
bipyridyl and 1,10-phenanthroline were planned as co-ligands in
this investigation. Synthesis, structures, spectroscopy, fluorescence
and antimicrobial aspects of complexes are investigated.
2.2. Crystal and molecular structure
The crystals of complexes 1e5, 7 and 8 were grown from
CH2Cl2eMeOH or CH3CNeMeOH mixtures. Complex 6 though
crystalline did not yield crystals of size suitable for X-ray crystal-
lography, however, the analytical data supported stoichiometry
similar to that of other complexes. Complexes 1, 4 and 5 formed
orthorhombic crystals, 3 and 7 formed triclinic crystals and 2 and 8
formed monoclinic crystals in space groups Pna21 (1), Pna21 (4),
Pbca (5), P-1 (3), P21/c (2, 7) and P21/n (8) respectively (Table 1).
Complexes 1e8 are mononuclear in which the metal is bonded to a
thiosemicarbazone through its O, N, S-donor atoms and N,N-donor
atoms of bipy or phen heterocyclic bases. The O, N, S-donor atoms
occupy the basal plane and the heterocyclic N,N-bases occupy the
axial-equatorial sites.
The bipyridine complexes, 1, 3, 5 and 7 have Me, Et, Ph or H
groups at N1 atom. The molecular structure of complex 1 is shown
in Fig. 1. Copper atom is coordinated by phenolato oxygen (O1),
azomethine nitrogen (N1), thiolato sulfur (S), and bipyridine ni-
trogen atoms, N(4) and N(5). The atoms O(1), N(1), S(1) (thio-
ligand), and N(4) (bipy ligand) occupy square basal plane while
2. Results and discussion
2.1. Synthesis, IR spectroscopy and magnetism
Scheme 1 shows the formation of complexes 1e8 incorporating
5-methoxy-salicylaldehyde-N-substituted
thiosemicarbazones
with bipy or phen as co-ligands. In a typical example, Cu(OAc)2
when reacted with H2L1 thio-ligand in methanol formed a brown
compound of empirical composition, [Cu(O,N3,S-L1)]. The addition
of bipy to the solid [Cu(O, N3, S-L1)] suspended in acetonitrilee
methanol mixture led to the formation of a dark green complex of
stoichiometry, [Cu(O,N3,S-L1)(N,N-bipy)]$CH3OH (1). Other thio-
ligands, namely, H2L2, H2L3, H2L4 also yielded complexes of
similar stoichiometry, [Cu(O,N3,S-L)(N, N-bipy)] (L ¼ L2, 3; L3, 5; L4,
7), [Cu(O,N3,S-L)(N,N-phen)D] (L ¼ L1, D ¼ 0.5H2O 2; [Cu(O,N3,S-
L)(N,N-phen)] (L2 4, L3,6; L4, 8). The complexes are dark green in
color and are soluble in dichloromethane, methanol, acetonitrile
and dimethyl sulfoxide.
N(5) (bipy) occupies the axial position. The
suggests that the geometry of complex is distorted square-
pyramidal. Complexes 3, 5 and 7 have similar structures (Figs. 3,
s parameter of 0.3
R
S
OH
C
H
N2
Me, H2L1
N3
C
N
N
bipy
MeO
Et,
H2L2
N1HR
Ph, H2L3
NH2, H2L4
H
N
N
phen
The IR spectrum of H2L2 ligand shows
3344 cmꢀ1 which appears at 3341 cmꢀ1 in its complex, [CuL2(bipy)]
3. A broad band of the free ligand due to (OeH)
(N2eH) and
n
(N1eH) band at
n
n
Chart 2. Thiosemicarbazones and co-ligands.

T.S. Lobana et al. / European Journal of Medicinal Chemistry 76 (2014) 145e154
147
S
OH
C
H
N2
Cu(OAc)2
-2AcOH
N3
R
C
[Cu(N,O,S-L)]
MeO
Me, H2L1
Et,
Ph, H2L3
H,
H2L4
N1HR
H2L2
H
H2L
L'
N
N
O
L'
=
Cu
N
N
N
N3
S
N
1- 8
Scheme 1. Synthetic route to complexes.
ꢀ
ꢁ
ꢀ
ꢁ
5 and 6 respectively). The bond lengths and bond angles of all these
complexes are similar with minor differences as shown in Table 2.
2ꢀ
2ꢀ
L ¼ L3
;
L0 ¼ phen 6; L4
;
L0 ¼ bipy 7
The molecular geometry is close to a square pyramid. The
rameters vary in the close range, 0.260e0.357. The distortion from a
square pyramid varies in the order Ph
s pa-
The electronic absorption spectral data and fluorescence spec-
tral data of complexes are listed in the experimental section. For
observing ded transitions based on CuII ion, 10ꢀ3 M solutions were
used and for transitions centered on the ligands and involving
charge transfer (CT) bands, the 10ꢀ4ꢀ10ꢀ5 M solutions were used.
The absorption spectral bands can be classified into four categories.
The electronic spectral bands in the region, 265e295 nm are
R
¼
(5) > Me(1) > Et(3) > H(7). The CueNeq(bipy) distances are shorter
than the CueNax(bipy) bond distances. Further CueN(thio-ligand)
bond distance is shorter than the CueNeq(bipy) bond distance. The
trans OeCueS bond angles deviate significantly from 180ꢁ, while
NeCueNeq angles are close to 180ꢁ. The NaxeCueNeq bite angles are
shortest and similar.
assigned to
347 nm are assigned to n /
in the region 389e430 nm are attributed to the combined O / Cu
(CT) and 2B1e2Eg
n3 (ded)] transitions. Finally, the bands in the
region 560e585 nm are pure ded (n3) transitions. The ded transi-
tions confirm divalent oxidation state of the metal in complexes 1e
8 [16].
p
/
p
* transitions, and those in the region 305e
p* plus S / Cu transitions. The bands
The 1,10-phenanthroline complexes, 2, 4 and 8 have Me, Et and
H groups at N1 atom. Complex 2 showed the presence of two in-
dependent molecules in the unit cell. In molecule 2a, copper atom
is coordinated by phenolato oxygen (O1), azomethine nitrogen
(N5), thiolato sulfur (S), and phen nitrogen atoms, N(2) and N(5).
[
The atoms O(1), N(5), S(1)(thio-ligand), and N(1)(phen
occupy
ligand)
As regards fluorescence spectral studies, all complexes were
screened for fluorescence corresponding to the excitation wave-
length of 355 nm. However, complexes 1, 3 and 7 were non-
fluorescent and other complexes, namely, 2, 4e6 and 8, most of
which have phen as co-ligand were found to be fluorescent in the
region, 375e475 nm (Fig 8). It can be noted that complex 4 with N-
ethyl substitution at C1 carbon has shown the most intense emis-
sion bands covering a wide visible region of the spectrum. Complex
5 has shown similar emission behavior, though emission intensity
is somewhat less than that shown by complex 4 and likewise
emission intensity of complexes 2 and 8 is lowest. Finally, complex
square basal plane, while N(2)(phen) occupies the axial position (Fig
2). The parameter of 0.34 suggests that the geometry of complex is
distorted square-pyramidal. Similarly, the value for complex 2b is
0.24 which suggests more distortion from square pyramid of 2a
molecule than that of 2b molecule. The molecular structure and
bond parameters of 4 and 8 (Figs. 4 and 7) are similar to those of
s
s
complex 2. The
s values vary in the range, 0.243 to 0.341. The
structures as well as bond parameters are also similar to those of
bipy complexes. The coordination pattern and bonding trends are
similar to those reported in literature [13]. Methanol in 1 and 4 as
well as H2O in 2 was lying in the lattice as non-bonded.
6 has shown one emission band at
l
¼ 400 nm with a vibrational
fine structure at
attributed to
l
¼ 380 nm. The origin of fluorescence emission is
2.3. ESI-mass, electronic absorption and fluorescence spectroscopy
pe
p* transitions centered on phen/bipy ligands.
ESI-mass spectral study has shown an intense molecular ion for
each of complexes 1, 2, 3, 4, 6 and 7. It reveals the stability of
complexes under ESI-mass environments. This ionization may be
represented as follows:
2.4. Antimicrobial studies
2.4.1. Importance of this study
The antimicrobial investigations have been carried out against
h
ꢀ
ꢁꢀ
ꢁi
Cu k3 ꢀ O; N; S ꢀ L k2 ꢀ N; N ꢀ L0
/ Cu k3 ꢀ O; N; S ꢀ L k2 ꢀ N; N ꢀ L0
gram negative bacteria, namely, Klebsiella pneumoniae
1
(MTCC109), Shigella flexneri (MTCC1457), Pseudomonas aeruginosa
(MTCC741), gram positive bacteria, namely, Staphylococcus aureus
(MTCC740) and methicillin resistant Staphylococcus aureus (MRSA)
and one yeast, Candida albicans (MTCC227. These bacteria are
responsible for causing gastrointestinal tract infections and respi-
ratory infections. It is known that K. pneumoniae 1 (MTCC109), P.
aeruginosa (MTCC741) and S. flexneri (MTCC1457) acquire resis-
tance more readily due to their outer membrane which contains
narrow porin channels, a lipopolysaccharide moiety responsible to
h
ꢀ
ꢁꢀ
ꢁiþ
ꢀ
ꢀ
ꢁ
ꢁ
ꢀ
ꢀ
ꢁ
ꢁ
2ꢀ
2ꢀ
L ¼ L1
;
;
L0 ¼ bipy 1; L1
;
;
L0 ¼ phen 2
L0 ¼ phen 4
2ꢀ
2ꢀ
L ¼ L2
L0 ¼ bipy 3; L2

148
T.S. Lobana et al. / European Journal of Medicinal Chemistry 76 (2014) 145e154
Table 1
Crystallographic data for complexes 1e5, 7, 8.
1
2
3
4
Empirical formula
M
C20H19CuN5O2S$CH3OH
489.04
C22H19CuN5O2S.0.5H2O
490.03
C21H21CuN5O2S
471.05
C23H22CuN5O2S$CH3OH
528.12
T(K)
293(2)
295(2)
296(2)
296(2)
Crystal system
Space group
Unit cell dimensions
Orthorhombic
Pna21
Monoclinic
P21/c
Triclinic
P-1
Orthorhombic
Pna21
ꢀ
a(A)
18.1670(3)
6.6879(2)
17.3213(3)
90.00
90.00
90.00
2104.5(8)
4
1.543
10.8253(4)
12.3099(5)
32.1284(11)
90.00
97.928(2)
90.00
4240.5(3)
4
1.535
8.290(3)
10.380(5)
13.2628(2)
71.647(2)
82.728(2)
75.73(2)
1049.48(8)
2
20.100(2)
6.801(1)
17.339(2)
90.00
90.00
90.00
2370.0(4)
4
1.480
ꢀ
b(A)
ꢀ
c(A)
a
b
g
(ꢁ)
(ꢁ)
(ꢁ)
3
ꢀ
V(A )
Z
D
m
calcd(g cmꢀ3
)
1.491
1.168
(mmꢀ1
)
1.171
1.162
1.046
F(000)
1012
2016
486
1096
Reflections collected
Unique reflections
22893
6598,
34143
9213,
27283
7564,
12529
4392,
(Rint ¼ 0.0308)
6598/1/287
6152
(Rint ¼ 0.0547)
9213/5/602
5924
(Rint ¼ 0.0244)
7564/1/276
5487
(Rint ¼ 0.0435)
4392/2/311
3570
Data/restraints/parameters
Reflens.with [I > 2s(I)]
R indices
R1
WR2
0.0281
0.0646
0.0477
0.1120
0.0478
0.1282
0.0346
0.0795
R indices (all data)
R1
0.0317
0.0899
0.0724
0.0483
WR2
0.0665
0.1315
0.1474
0.0864
Largest diff. Peak and hole
0.400 and
ꢀ0.311 e A
1.407 and
ꢀ0.308 e A
1.759 and
ꢀ0.525 e A
0.397 and
ꢀ0.388 e A
ꢀꢀ3
ꢀꢀ3
ꢀꢀ3
ꢀꢀ3
5
7
8
Empirical formula
M
T(K)
C25H21CuN5O2S
519.07
173(2)
Orthorhombic
Pbca
C19H17CuN5O2S
C21H17CuN5O2S
467.02
296(2)
Monoclinic
P21/n
443.00
296(2)
Triclinic
P21/c
Crystal system
Space group
Unit cell dimensions
ꢀ
a(A)
13.8291(4)
9.5928(4)
34.298(13)
90.00
90.00
90.00
4549.9(3)
8
1.516
16.359(2)
6.786(1)
18.209(2)
90.00
110.607(5)
90.00
1892.1(4)
4
1.555
16.278(2)
6.906(1)
19.445(3)
90.00
112.95(1)
90.00
2013.1(5)
4
1.541
ꢀ
b(A)
ꢀ
c(A)
a
b
g
(ꢁ)
(ꢁ)
(ꢁ)
3
ꢀ
V(A )
Z
D
m
calcd(g cmꢀ3
)
(mmꢀ1
)
2.492
1.290
1.217
F(000)
2136
908
956
Reflections collected
Unique reflections
Data/restraints/parameters
33005
15528
13622
4348, (Rint ¼ 0.0505)
4348/0/309
3942
2645, (Rint ¼ 0.0598)
2645/0/254
4097
3658, (Rint ¼ 0.0810)
3658/2/278
2185
Reflens.with [I > 2s(I)]
R indices
R1
WR2
0.0332
0.0916
0.0473
0.1003
0.0518
0.0878
R indices (all data)
R1
0.0369
0.0887
0.1090
WR2
0.0949
0.1163
0.1056
Largest diff. Peak and hole
0.341 and
ꢀ0.427 e A
0.343 and
ꢀ0.287 e A
0.340 and
ꢀ0.331 e A
ꢀꢀ3
ꢀꢀ3
ꢀꢀ3
slow down the transmembrane diffusion of lipophilic antibiotics
[28]. It is also important to highlight that methicillin-resistant
Staphylococcus aureus (MRSA) causes nosocomial and
community-onset infections which have shown increasing
endemic and epidemic spread in the last four decades, while its
control has become a serious concern worldwide [29e33]. The
control and prevention of MRSA cross-infection is among the most
important challenges of infection control, especially due to the fact
that these bacteria have shown resistance not only to methicillin
but also to several other drugs except vancomycin (glycopeptides)
[34e36]. The increased resistance has invited the search for new
antimicrobial agents, a challenging task for chemists [37,38].
2.4.2. Biological data and discussion of results
The antimicrobial activities of mixed-ligand complexes, [Cu(k3
-
O,N,S-L)(N,N-donor)] 1e8 (Class I compounds), [Cu(k
3-O,N,S-L)]n
compounds without bipyridine or phenanthroline bases (Class II
compounds) and thio-ligands H2L {H2L ¼ H2L1, H2L2, H2L3, H2L4}
(Class III compounds) have been studied in dimethyl sulfoxide
(dmso). The biological data listed in Table 3 reveal that, in general,

T.S. Lobana et al. / European Journal of Medicinal Chemistry 76 (2014) 145e154
149
activity, but activity of complex 5 was as good as that of Gentamycin.
All complexes showed activity against C. albicans in the range 23e
31 mm zoi and activity of complex 1 (31 mm zoi) was as good as
that of commercial Amphotericin (34 mm zoi). From the above
discussion it is noted that among bipyridyl complexes, complex 5
with a phenyl substituent at N1 atom of H2L3 ligand appears
generally suitable for inhibiting all the microorganisms including
the methicillin resistant Staphylococcus aureus and it can be
considered as a potential antimicrobial agent.
It can be seen from Table 4 that several complexes were active at
minimum inhibitory concentration (MIC) of 5
resistant Staphylococcus aureus: 4, 5, 8; K. pneumoniae 1: 4, 5, 7; C.
albicans: 1e4), MIC of 10 g/mL (methicillin resistant Staphylo-
coccus aureus: 1e3; S. aureus: 1, 3, 5, 7, 8; K. pneumoniae 1: 1, 2, 6, 8;
C. albicans: 5e8), MIC of 25 g/mL (methicillin resistant staphylo-
coccus aureus: 6, 7; S. aureus: 2, 4, 6; K. pneumoniae 1: 3). Complexes
6 and 8 showed activity at MIC of 750 g/mL for S. flexneri while
only complex 5 showed activity at MIC of 750 g/mL for P. aerugi-
mg/mL (methicillin
m
m
m
m
Fig. 1. Molecular structure of complex [Cu(k k
3-O,N,S-L1)( 2-N,N-bipy)]$CH3OH (1).
nosa. Further it has been observed that bipyridyl and phenan-
throline base adducts of copper(II) complexes with
thiosemicarbazones are less toxic in biological systems than the
free thio-ligand. Higher antimicrobial activity of complexes is
attributed to their better membrane penetrating ability and the
cause of inhibitory action of complexes can be due to their inter-
action with enzyme prosthetic group which inhibits the replication
of DNA [39].
the antimicrobial activity of three types of compounds varies in the
order : Class I > Class II > Class III. Thus the mixed-ligand com-
plexes become the preferred choice for antimicrobial activity and
some most significant observations made are presented as follows.
Complexes 1e5 and 8 have shown highest antimicrobial activity
ranging from 25 to 32 mm zone of inhibition (zoi) against methi-
cillin resistant staphylococcus aureus (MRSA). This is an interesting
observation as the commercially available Gentamycin is found to
be inactive against this bacterial strain. Complexes 1, 3, 5, 7 and 8
have shown activity against S. aureus (23e27 mm zoi) which is
comparable to that of Gentamycin (25 mm zoi) (Table 3). Complexes
1e8 have shown activity against K. pneumoniae 1 in 23e33 mm zoi
and it is interesting to remark that complexes 2 and 4 showed ac-
tivity (30e33 mm zoi) close to that of Gentamycin (32 mm zoi).
None of Class II compounds were active against S. flexneri, two
compounds of Class III were active but activity is much lower than
that shown by complexes 4e8 (15e18 mm zoi), which is compa-
rable to that of Gentamycin (20 mm zoi). As regards activity against
P. aeruginosa only complex 5 and two of Class II compounds showed
2.4.3. A comparison with literature reports of relevance to the
present study
It is pertinent to point out here that in literature reports with 3-
methoxy substitution along with 5-phenylazo moiety in the 2-
hydroxy phenyl ring (Chart 1) and with both hydrogens at N1
atom (-ie, eN1H2), complexes were dinuclear in the absence of co-
ligands and were found to show antitumor activity, though no
antimicrobial activity was studied [11]. With 5-methoxy substitu-
tion along with methyl/ethyl substitution at N1 nitrogen of the thio-
ligand in the absence of co-ligands again formed dinuclear com-
plexes which did not show antimicrobial activity [21]. The presence
of 5-methoxy substitution in the 2-hydroxy phenyl ring and with
hydrogen, methyl, ethyl and phenyl substituents at N1 atom, five
coordinate complexes 1e8 have been prepared using bipyridine/
phenanthroline as co-ligands which have shown unusual antimi-
crobial activity as detailed above. This activity could be attributed to
the fact that five coordinate complexes exhibit greater lipophilicity
than four coordinate dinuclear complexes [11,21]. The fact that
several Class II compounds have shown significant activity suggests
that the nature of the thio-ligand with different substituents at N1
atom appears to be important. Further increase in activity shown by
mixed-ligand Class I compounds suggests a cumulative effect of
thio-ligands and N,N-donor bases bonded to CuII metal center
which determine the total antimicrobial activity. Complex 5 formed
by 5-methoxysalicylaldehyde-N-phenylthiosemicatbazone has
shown novel antimicrobial activity against various bacteria and
fungi investigated.
3. Conclusion
In the present study salicylaldehyde-N substituted thio-
semicarbazones having 5-methoxy substitution in the 2-hydroxy
phenyl ring along with different substituents at N1 nitrogen using
2,20-bipyridine and 1,10-phenanthroline as co-ligands formed dis-
torted square pyramidal complexes which have shown significant
growth inhibitory activity against S. aureus (MTCC740), methicillin
resistant Staphylococcus aureus (MRSA), K. pneumoniae
(MTCC109), S. flexneri (MTCC1457), P. aeruginosa (MTCC741) and C.
1
Fig. 2. Molecular structure of complex [Cu(k k
3-O,N,S-L1)( 2-N,N-phen)]$0.5H2O (2).

150
T.S. Lobana et al. / European Journal of Medicinal Chemistry 76 (2014) 145e154
analysis C, H, and N were carried out with a thermoelectron FLA-
SHEA1112 analyzer. The melting points were determined with a
Gallenkamp electrically heated apparatus. Magnetic susceptibility
measurements were made at room temperature with the help of a
magnetic susceptibility balance procured from Johnson Matthey,
Catalytic Systems Division Equipment, UK. The IR spectra of com-
pounds were recorded in 4000e450 cmꢀ1 region with a Perkin
Elmer FT-IR Spectrometer by making their KBr pellets. The UVe
visible spectra of compounds were recorded in dmso or methanol
solvents with the help of a UV-1601 PC Shimadzu spectropho-
tometer. Fluorescence spectra of complexes were recorded with a
Varian Cary Eclipse Fluorescence spectrophotometer. The mass
spectra were recorded using Bruker Daltonik LS-MS high resolution
microTOF-Q II 10356.
4.2. Synthesis of complexes
Complexes 1e8 were prepared by initially reacting copper(II)
acetate with a thio-ligand which formed a compound of empirical
composition [CuII(O,N3,S-L] (presumably a dimer or an oligomer)
which was reacted with a N,N-donor co-ligand. The experimental
procedures and characterization data are summarized below.
Fig. 3. Molecular structure of complex [Cu(k k
3-O,N,S-L2)( 2-N,N-bipy)] (3).
4.2.1. [Cu(
To
pale yellow solution of thio-ligand L1H2 (0.029 g,
k k
3-O,N,S-L1)( 2-N,N-bipy)]$CH3OH (1)
a
albicans (MTCC227). Complex
5
formed by 5-methox-
0.127 mmol) in methanol (15 mL) was added dark green solid
Cu(OAc)2$H2O (0.025 g, 0.125 mmol). Brown precipitate start
forming immediately and were stirred for one hour to ensure
complete precipitation. The precipitate were filtered and allowed to
dry at room temperature. The analytical data supported the for-
mation of a compound of empirical composition, [CuII(O,N, S-L1]
(Anal. calcd for C10H11CuN3O2S: C 39.93; H 3.69; N 13.97; Found: C
40.06; H 3.47; N 13.78%, meff ¼ 2.01 BM). To a suspension of
[CuII(O,N,SꢀL1] (0.028 g, 0.092 mmol) in a mixture of acetonitrile
and methanol (1 : 1 v/v) was added solid bipy co-ligand (0.014 g,
0.092 mmol) and the contents were stirred for 15 min. A clear dark
green solution formed was allowed to evaporate at room temper-
ature which yielded a dark green complex (Yield. 0.031 g, 71%, M.p.
206e208 ꢁC); meff ¼ 1.79 BM. C20H19CuN5O2S$CH3OH : Calcd. C
52.56; H 4.19; N 15.32; S 7.02; Found: C 52.32; H 4.04; N 15.17; S
ysalicylaldehyde-N-phenylthiosemicarbazone has shown novel
antimicrobial activity against various bacteria and fungi investi-
gated. The results are encouraging especially related to MRSA and
further pursuit is needed both in alteration of groups in rings at C2
carbon, at N1 atoms of thiosemicarbazones and the nature of co-
ligands. The activity against MRSA is an interesting observation as
the commercially available gentamycin is found to be inactive
against this bacterial strain.
4. Experimental section
4.1. Materials and methods
Copper(II) acetate monohydrate Cu(OAc)2$H2O, thio-
semicarbazide, N-methyl thiosemicarbazide, N-ethyl thio-
7.12%. IR (KBr, selected absorption bands): n n(OeH)
(N1eH) 3419 s;
semicarbazide,
N-phenyl
thiosemicarbazide,
5-methoxy-
salicylaldehyde, 2,2-bipyridine (bipy) and 1,10-phenanthroline
(phen) were procured from Aldrich Sigma Ltd. The thio ligands
were synthesized by conventional procedures [25,40]. Elemental
Fig. 4. Molecular structure of complex [Cu(
k
3-O,N,S-L2)(
k
2-N,N-phen)]$CH3OH (4).
Fig. 5. Molecular structure of complex [Cu(k k
3-O,N,S-L3)( 2-N,N-bipy)] (5).

T.S. Lobana et al. / European Journal of Medicinal Chemistry 76 (2014) 145e154
151
(1.63 ꢂ 102); [10ꢀ4 M] 404 s, br (6.81 ꢂ 103), 320 br (1.24 ꢂ 104),
290 m (1.51 ꢂ 104), 268 m (2.70 ꢂ 104). ESI mass data: calcd for
C
21H21CuN5O2S, [M]þ, m/z ¼ 470; obsd. m/z ¼ 471 s.
4.2.4. [Cu(k k
3-O,N,S-L2)( 2-N,N-phen)]$CH3OH (4)
To a suspension of [CuII(O,N,S-L2)] (0.025 g, 0.079 mmol) in a
mixture of acetonitrile and methanol (1:1 v/v) was added phen co-
ligand (0.012 g, 0.079 mmol) and the contents were stirred for
15 min. A clear dark green solution was allowed to evaporate at
room temperature, which yielded dark green complex. (Yield.
0.031 g, 73%, M.p. 227e229 ꢁC); meff ¼ 2.12 BM. C23H22Cu-
N5O2S$CH3OH: Calcd. C 55.69; H 4.47; N 12.81; S 6.46; Found: C
55.72; H 4.37; N 13.08; S 6.29%. IR (KBr, selected absorption bands):
n
(N1eH) 3342 br;
(CH3O-);
(C]N) þ
1498 s; 1472 s, 1414 s; 1298 s, 1219 s, 1199 s, 1163 s, 1097 s, 1042 s,
n
(CeH) 2970 m, 2925 m, 2873 m;
n
(CeH) 2832 m
(CeH)
n
n
(C]C) þ (NeH) 1589 s, 1534 s;
d
d
1022 s, 938 s, 836 s;
n(CeS) 815 s; 764 s, 736 s, 650 s, 625 s,
486 m cmꢀ1. Electronic absorption spectrum, MeOH, lmax/nm,
ε/L molꢀ1 cmꢀ1: [10ꢀ3 M] 574 s, br (2.10 ꢂ 102); [10ꢀ4 M] 423 m, br
(9.70 ꢂ 103), 330 br (1.64 ꢂ 104), 297 m (1.52 ꢂ 104). Fluorescence
Fig. 6. Molecular structure of complex [Cu(k k
3-O,N,S-L4)( 2-N,N-bipy)] (7).
em
ex
3380 s (CH3OH),
n(CeH) 3010 w, 2990 w, 2940 w,
n(CeH)
spectrum: (
l
¼ 400, 456 nm;
l
¼ 355 nm). ESI mass data :
max
max
calcd for C23H22CuN5O2S, [M]þ, m/z ¼ 495.5; obsd. m/z ¼ 495.3 s.
2825 m(CH3Oꢀ);
n
(C]N) þ (C]C) þ (NeH) 1601 s, 1562 s,
n
d
1522 s, 1508 s,
1048 s, 950 s,
d
(CeH) 1484 s; 1440 s, 1407 m; 1272 s, 1190 s, 1158 s,
(CeS) 813 s; 762 s, 736 s, 465 m cmꢀ1. Electronic
4.2.5. [Cu(k k
3-O,N,S-L3)( 2-N,N-bipy)] (5)
n
absorption spectrum, DMSO, lmax/nm, ε/L molꢀ1 cmꢀ1: [10ꢀ3 M]
565 m, br (2.51 ꢂ 102); [10ꢀ5 M] 420 s, br (1.21 ꢂ 104), 330 br
(1.96 ꢂ 104), 295 m (3.44 ꢂ 104). The crystals were grown from
dichloromethaneemethanol mixture (3:1 v:v) over a period of 10
days. Complexes 2e8 were prepared by a similar method. ESI mass
data: calcd for C20H19CuN5O2S, [M]þ 456; obsd. m/z ¼ 457 s.
To a suspension of [CuII(O,N,S-L3)] (0.03 g, 0.082 mmol) in
acetonitrile was added bipy co-ligand (0.013 g, 0.083 mmol) and
the contents were stirred for 15 min. The clear dark green solution
obtained was allowed to evaporate at room temperature, which
yielded dark green crystals. (Yield. 0.043 g, 81%, M.p. 211e213 ꢁC).
meff ¼ 2.08 BM. C25H21CuN5O2S: Calcd. C 57.85; H 4.08; N 13.49, S
6.18; Found: C 58.06; H 4.12; N 13.17, S 6.09%. IR (KBr, selected
4.2.2. [Cu(k k
3-O,N,S-L1)( 2-N,N-phen)]$0.5H2O (2)
absorption bands):
2865 m; (CeH) 2825 m (CH3O-);
1601 s,1561 s,1522 s; (CeH) 1485 s,1440 s,1407 s,
1191 s, 1159 s, 1047 s, 950 s, 854 s; (CeS) 814 s; 762 s, 735 s,
n
(N1eH) 3418 br;
(C]N) þ
n
(CeH) 2993 m, 2932 m,
(C]C) þ (NeH)
1272 s,1223 s;
To a suspension of [CuII(O,N,S-L1)] (0.028 g, 0.089 mmol) in a
mixture of acetonitrile and methanol (1:1 v/v) was added phen co-
ligand (0.018 g, 0.089 mmol) and the contents were stirred for
15 min. A clear dark green solution formed was allowed to evap-
orate at room temperature which yielded a dark green complex
(Yield. 0.032 g, 70%, M.p. 212e214 ꢁC); meff ¼ 1.94 BM. C22H19Cu-
N5O2S$0.5H2O: Calcd. C 53.92; H 4.11; N 14.29; S 6.54; Found: C
54.07; H 3.97; N 14.42; S 6.41%. IR (KBr, selected absorption bands):
n
n
n
d
d
n
n
468 m cmꢀ1. Electronic absorption spectrum, MeOH, lmax/nm,
ε/L molꢀ1 cmꢀ1: [10ꢀ3 M] 570 br (3.00 ꢂ 102); [10ꢀ4 M] 414 s, br
(7.71 ꢂ 103), 327 s (1.36 ꢂ 104), 287 m (1.43 ꢂ 104). Fluorescence
em
ex
spectrum: (
l
¼ 400, 470 nm;
l
¼ 355 nm).
max
max
n
(N1eH) 3418 s;
2885 w; (CeH) 2833 m(CH3Oe);
1592 s, 1567 s, 1507 s; (CeH) 1472 s, 1438 s, 1414 m; 1297 s, 1272 s,
1190 s, 1158 s, 1034 s, 950 s, 846 s; (CeS) 813 s; 768 s, 727 s, 475 m
n
(OeH) 3380 s (H2O);
n
(CeH) 2933 w, 2897 w,
4.2.6. [Cu(k k
3-O,N,S-L3)( 2-N,N-phen)] (6)
To a suspension of [CuII(O,N,S-L3)] (0.03 g, 0.083 mmol) in a
mixture of acetonitrile and methanol was added phen (0.017 g,
0.083 mmol) and the contents were stirred for 15 min. The clear
dark green solution obtained was allowed to evaporate at room
temperature, which yielded dark green crystalline complex (Yield.
0.037 g, 82%, M.p. 223e225 ꢁC); meff ¼ 1.97 BM. C27H21CuN5O2S:
Calcd. C 59.71; H 3.90; N 12.90; S 5.90; Found: C 59.90; H 3.73; N
n
n
(C]N) þ
n
(C]C) þ (NeH)
d
d
n
cmꢀ1
.
Electronic absorption spectrum, MeOH, lmax/nm,
ε/L molꢀ1 cmꢀ1: [10ꢀ3 M] 575 m, br (1.92 ꢂ 102); [10ꢀ4 M] 404 s, br
(8.93 ꢂ 103), 321 br (1.64 ꢂ 104), 290 m (2.32 ꢂ 104), 269 m
em
(3.91 ꢂ 104). Fluorescence spectrum: (
l
¼ 378, 461 nm;
max
¼ 355 nm). ESI mass data: calcd for C22H19CuN5O2S, [M]þ, m/
ex
max
13.06; S 5.81%. IR (KBr, selected absorption bands):
br; (CeH) 3059 m, 2986 m, 2929 m;
(CeH) 2830 m (CH3Oꢀ);
(C]N) þ (C]C) þ (NeH) 1583 s, 1535 s, (CeH) 1489 s, 1471 s,
1426 s; 1311 s, 1256 s, 1243 s, 1209 s, 1157 s, 1041 s, 950 s, 845 s;
n
(N1eH) 3401
l
z ¼ 480; obsd. m/z ¼ 481 s. n.
n
n
n
n
d
d
4.2.3. [Cu(k k
3-O,N,S-L2)( 2-N,N-bipy)](3)
To a suspension of [CuII(O,N,S-L2)] (0.025 g, 0.079 mmol) in a
mixture of acetonitrile and methanol (1:1 v/v) was added bipy co-
ligand (0.016 g, 0.079 mmol) and the contents were stirred for
15 min. A clear dark green solution was allowed to evaporate at
room temperature, which yielded dark green complex (Yield.
0.03 g, 78%, M.p. 216e218 ꢁC); meff ¼ 1.80 B.M. C21H21CuN5O2S:
Calcd. C 53.55; H 4.49; N 14.87; S 6.81; Found: C 53.78; H 4.36; N
n
(CeS) 812 s; 774 s, 755 s, 726 s, 695 s, 509 m cmꢀ1. Electronic
absorption spectrum, MeOH, lmax/nm, ε/L molꢀ1 cmꢀ1: [10ꢀ3 M]
585 s, br (3.2 ꢂ 102); [10ꢀ4 M] 430 br (2.81 ꢂ104), 347 s (3.63 ꢂ 104),
331 m (4.42 ꢂ 104), 265 s (0.9 ꢂ 104). Fluorescence spectrum:
em
ex
(
C
l
¼ 380, 400 nm;
l
¼ 355 nm). ESI mass data: calcd for
max
max
27H21CuN5O2S, [M]þ, m/z ¼ 542; obsd. m/z ¼ 543 s.
14.95; S 6.69%. IR (KBr, selected absorption bands):
br; (CeH) 2970 m, 2927 m, 2871 m; (CeH) 2830 m (CH3Oe);
(C]N) þ (C]C) þ (NeH) 1589 s, 1538 s; (CeH) 1471 s, 1438 s,
1412 s; 1297 s, 1218 s, 1190 s, 1160 s, 1096 s, 1034 s, 1021 s, 937 s,
836 s;
(CeS) 815 s; 735 s, 649 s, 476 m cmꢀ1. Electronic absorption
spectrum, MeOH, lmax/nm, ε/L molꢀ1 cmꢀ1: [10ꢀ3 M] 570 s, br
n
(N1eH) 3342
4.2.7. [Cu(k k
3-O,N,S-L4)( 2-N,N-bipy)] (7)
n
n
To a suspension of [CuII(O,N,S-L4] (0.027 g, 0.098 mmol) in a
mixture of acetonitrile and methanol (1:1 v/v) was added solid bipy
(0.015 g, 0.098 mmol) and the contents were stirred for 15 min. A
clear dark green solution formed was allowed to evaporate at room
temperature which yielded dark green complex (Yield. 0.036 g,
n
n
d
d
n

152
T.S. Lobana et al. / European Journal of Medicinal Chemistry 76 (2014) 145e154
Table 2
15 min. A clear dark green solution formed was allowed to evap-
orate at room temperature which yielded dark green complex
(Yield. 0.037 g, 80%, M.p. 190e192 ꢁC). meff ¼ 1.94 BM. C21H17Cu-
N5O2S: Calcd. C 54.01; H 3.67; N 15.00; S 6.87; Found: C 53.87; H
ꢁ
ꢀ
Bond distances (A) and bond angles ( ) in complexes 1e5, 7, 8.
[Cu(
k
3-O,N,S-L)(
k
2-N,N-bipy)] (1, 3, 5 and 7). ax ¼ axial; eq ¼ equatorial
1
3
5
7
3.46; N 15.18; S 7.01%. IR (KBr, selected absorption bands):
3347 s, 3289 s (NH2); (CeH) 3161 m, 3108 m, 3072 m,
(CeH) 2834 m (CH3O-); (C]C) þ (NeH) 1630 s,
(C]N) þ
(CeH) 1493 s, 1469 s, 1424 s; 1319 s, 1299 s, 1252 s,
(CeS) 812 s, 769 s, 702 s,
n
(N1eH)
n 2989 br,
CueO
CueN
CueS
CueNeq
CueNax
1.9466(12)
1.9522(13)
2.2695(5)
2.0192(13)
2.2529(14)
1.9307(17)
1.9567(18)
2.2584(7)
2.0451(19)
2.234(2)
1.9293(2)
1.9529(14)
2.2623(5)
2.0274(15)
2.253(15)
1.913(3)
1.949(3)
2.2849(11)
2.028(3)
2.268(3)
n
n
n
n
n
n
d
1586 s, 1533 s,
d
1217 s, 1191 s, 1040 s, 942 s, 864 s, 844 s;
n
638 s, 484 m cmꢀ1. Electronic absorption spectrum (10ꢀ3/10ꢀ5 m in
MeOH, lmax/nm, ε/L molꢀ1 cmꢀ1: [10ꢀ3 M] 585 br (1.85 ꢂ 102),
[10ꢀ3 M] 420 m, br (1.23 ꢂ 104), 343 s (1.61 ꢂ 104), 328 s
(2.10 ꢂ 104), 282 m (3.91 ꢂ 104). The crystals were grown from
OeCueN
NeCueS
OeCueS
NeCueNeq
93.43(5)
85.31(4)
159.37(4)
177.28(6)
76.59(5)
0.298
93.88(7)
85.26(6)
160.47(6)
176.88(8)
76.77(8)
0.273
92.63(6)
85.61(4)
157.75(4)
179.22(6)
76.32(6)
0.357
92.53(11)
85.25(9
161.62(11)
177.25(12)
76.32(11)
0.260
N
eqeCueNax
dichloromethaneemethanol mixture (3:1 v:v). Fluorescence spec-
s
value
em
trum: (
l
¼ 400, 460 nm; lex ¼ 355 nm).
max
[Cu(
k
3-O,N,S-L)(
k
2-N,N-phen)] (2, 4 and 8).
2
4
8
4.3. X-ray crystallography
2a
2b
A single crystal was mounted on a glass fiber and used for data
collection with a Xcalibur, Eos, Gemini (1, 5), and a Bruker Kapa e
CueO
CueN
CueS
CueNeq
CueNax
1.9466(12)
1.958(3)
2.2611(10)
2.031(3)
1.923(3)
1.951(3)
2.2740(11)
2.027(3)
2.327(3)
1.9307(17)
1.9567(18)
2.2584(7)
2.0451(19)
2.234(2)
1.9293(2)
1.946(3)
2.2790(12)
2.037(3)
2.278(4)
Apex (II) CCD diffractometer (2e4, 7, 8), equipped with graphite
ꢀ
monochromated Mo-K
a
(
l
¼ 0.71073 A). Crystal data were collected
2.276(3)
at 173 (2) (5), 295(2) (1, 2), 296(2) (3, 4, 7, 8) K. For complexes 1 and
5 data were processed with CrysAlisPro CCD (data collection),
CrysAlisPro RED (cell refinement, data reduction) [41]. The struc-
ture was solved by direct methods using the program SHELXS- 97,
refined by full-matrix least-squares techniques against FV using
SHELX-97 and molecular graphics from SHELXL [42]. For complexes
2e4, 7, 8 data were processed with Bruker Kapa e Apex(II) CCD and
corrected for absorption using SADABS [43]. The structures were
solved by direct methods using SIR-92 software [43] and refined by
full-matrix least-squares method based on FV using the program
using SHELX-97 [42]. Atomic scattering factors taken from “Inter-
national Tables for Crystallography” [44]. The crystallographic data
and important bond parameters of complexes 1e5, 7 and 8 are
given in Tables 1 and 2, respectively.
OeCueN
NeCueS
OeCueS
NeCueNax
92.26(11)
85.31(9)
153.33(9)
173.74(12)
77.87(11)
0.341
92.84(12)
86.23(11)
161.66(10)
176.43(13)
76.65(12)
0.246
93.83(10)
85.30(8)
159.68(8)
176.44(12)
77.34(10)
0.279
93.15(13)
85.29(10)
161.62(11)
77.38(15)
176.24(15)
0.243
N
eqeCueNax
s
value
85%, M.p. 199e201 ꢁC). meff ¼ 1.81 BM. C19H17CuN5O2S: Calcd. C
51.52; H 3.87; N 15.81; S 7.24; Found: C 51.36; H 3.63; N 16.03; S
6.95%. IR (KBr, selected absorption bands:
(NH2); (CeH) 3158 m, 3108 m, 3073 m, 2991 br, 2951 s, 2927 s;
(CeH) 2831 m (CH3Oe); (C]C) þ (NeH) 1626 s,
(C]N) þ
1586 s, 1533 s; (CeH) 1485 s, 1469 s,, 1458 s, 1438 s, 1415 s; 1302 s,
1250 s, 1215 s, 1192 s, 1044 s, 946 s, 836 s;
n
(N1eH) 3347 s, 3280 s
n
n
n
n
d
d
n
ꢀ(1CeS) 816 s; 800 s, 769 s,
735 s, 704 s, 650 s, 627 s, 485 m cm . Electronic absorption
spectrum, MeOH, lmax/nm, ε/L molꢀ1 cmꢀ1: [10ꢀ3 M] 580 br
(2.0 ꢂ 102); [10ꢀ4 M] 389 s, br (6.10 ꢂ 103), 305 s (1.30 ꢂ 104), 287 m
(1.41 ꢂ 104), 270 m (1.93 ꢂ 104). The crystals were grown from
dichloromethaneemethanol mixture (3:1 v:v). ESI mass data: calcd
for C19H17CuN5O2S, [M]þ, m/z ¼ 442; obsd. m/z ¼ 443 s.
4.4. Antimicrobial studies
4.4.1. Test organisms
The reference strains of bacteria and yeast, used for testing their
sensitivity to complexes, were obtained from Microbial Type Cul-
ture Collection (MTCC), Institute of Microbial Technology (IMTECH),
Chandigarh, India and the clinical isolate methicillin resistant
Staphylococcus aureus (MRSA) was obtained from Post graduate
Institute of Medical Education and Research, (PGIMER), Chandi-
garh, India. Reference strains used Gram positive bacteria, S. aureus
4.2.8. [Cu(k k
3-O,N,S-L4)( 2-N,N-phen)] (8)
To a suspension of [CuII(O,N,S-L4] (0.028 g, 1.02 mmol) in a
mixture of acetonitrile and methanol (1:1 v/v) was added solid
bipyridine (0.024 g, 1.02 mmol) and the contents were stirred for
Fig. 8. Fluorescence spectral bands of complexes 2, 4e6, 8. {l
em: (2) 378, 461; (4) 400,
Fig. 7. Molecular structure of complex [Cu(
k
3-O,N,S-L4)(
k
2-N,N-phen)] (8).
456; (5) 400, 470; (6), 380, 400; (8) 400, 460 nm; lex ¼ 355 nm}.

T.S. Lobana et al. / European Journal of Medicinal Chemistry 76 (2014) 145e154
153
Table 3
Biological data for complexes 1e8.a,b,c
Complex/ligand
MRSAe
S. aureusf
K. pneumoniae 1g
S. flexnerih
P. aeruginosai
C. albicansj
[Cu(L1)(bipy)]1
[Cu(L2)(bipy)]3
[Cu(L3)(bipy)]5
[Cu(L4)(bipy)]7
[Cu(L1)(phen)]2
[Cu(L2)(phen)]4
[Cu(L3)(phen)]6
[Cu(L4)(phen)]8
25
26
27
21
32
27
21
26
20
20
17
21
N.A
10
17
N.A.
N.A.
27
25
25
23
20
21
21
24
15
18
17
17
14
15
15
15
25d
26
23
26
26
33
30
25
25
20
19
20
21
12
13
14
10
32d
N.A
N.A
15
16
N.A
16
N.A
N.A
17
31
24
23
24
27
27
24
25
15
20
21
20
12
12
15
14
34d
N.A
N.A
N.A
N.A
N.A
N.A
N.A
12
17
18
[CuL1]n
N.A
N.A
N.A
N.A
N.A
11
k
[CuL2]n
k
[CuL3]n
k
[CuL4]n
12
k
H2L1
N.A
N.A
N.A
N.A
17d
H2L2
H2L3
11
H2L4
N.A
Gentamycind/,l
Amphotericind/l
20d
a
All measurements are in mm diameter of the inhibition zone (N.A indicates no activity).
The standard deviation varied in the range 0e1 based on three readings.
Studies were made in dmso.
Commercially available anti-microbial agents.
Methicillin resistant Staphylococcus aureus.
Staphylococcus aureus.
Klebsiella pneumoniae 1.
Shigella flexneri.
Pseudomonas aeruginosa.
Candida albicans.
b
c
d
e
f
g
h
i
j
k
l
See Supporting information for more details of the compounds.
Gentamycin acts as positive control against bacteria (S. aureus, K. pneumoniae 1, S. flexneri, P. aeruginosa) and Amphotericin acts as positive control against yeast (Candida
albicans).
(MTCC740), Gram negative bacteria, K. pneumoniae 1 (MTCC109), P.
aeruginosa (MTCC741), S. flexneri (MTCC1457) and one yeast strain
C. albicans (MTCC227). The bacterial cultures were maintained on
nutrient agar slants, and C. albicans was maintained on yeast malt
agar.
diffusion assay [45]. All the compounds were dissolved in dimethyl
sulfoxide (dmso) to a final concentration of 0.1%. The plates con-
taining Muller Hinton agar medium, yeast malt agar and Sabouraud
agar were spread with 50
respectively. Wells (6 mm diameter) were cut out from agar plates
using sterilized stainless steel cork borer and filled with 50 L of the
mL of the bacterial and yeast inoculums
m
compound. The plates were incubated at 37 ꢁC and 25 ꢁC for 24 h
and diameter of resultant zone of inhibition was measured. Ex-
periments were run in duplicate for each combination of extract
and microbial strains. The results were compared with control in
which compounds were replaced with dmso. In order to compare
the effectiveness of compounds their activities were compared
with standard antibiotic, namely, Gentamycin (1 mg/mL) for bac-
terial culture and amphotericin (1 mg/mL) for yeast culture. Gen-
tamycin acts as positive control against bacteria (S. aureus, K.
pneumoniae 1, S. flexneri, P. aeruginosa) and Amphotericin acts as
positive control against yeast (C. albicans).
4.4.2. Inoculum preparation
A loopful of isolated bacterial colonies and yeast colony were
inoculated into 5 mL of respective medium and incubated at 37 ꢁC
and 25 ꢁC respectively for 4 h. The turbidity of actively growing
bacterial suspension was adjusted to match the turbidity standard
of 0.5 Mc Farland units prepared by mixing 0.5 mL of 1.75% (w/v)
barium chloride dihydrate (BaCl2,2H2O) to 99.5 mL of 0.18 M (v/v)
sulfuric acid with constant stirring. The microbial suspension so
prepared was used for testing their sensitivity to all the compounds
used.
4.4.3. Screening of compounds for antimicrobial activity by agar
well diffusion assay
4.4.4. Minimum inhibitory concentration of complexes
Sensitivity of different bacterial strains to different compounds
was measured in terms of zone of inhibition using agar well
Minimum inhibitory concentration (MIC) was worked out by
agar dilution method. The compounds were prepared and
Table 4
Minimum Inhibitory concentration (MIC in
m
g/mL) of copper(II) complexes 1e8.
S. aureus K. pneumoniae 1
Complex
MRSA
S. flexneri
P. aeruginosa
C. albicans
[Cu(L1)(bipy)]1
[Cu(L1)(phen)]2
[Cu(L2)(bipy)]3
[Cu(L2)(phen)]4
[Cu(L3)(bipy)]5
[Cu(L3)(phen)]6
[Cu(L4)(bipy)]7
[Cu(L4)(phen)]8
10
10
10
m
m
m
g
g
m
m
g
g
g
g
10
25
10
25
10
25
10
10
m
m
m
m
m
m
m
m
g
g
g
g
g
g
g
g
10
10
25
m
m
m
g
g
m
g
m
g
g
g
e
e
e
e
e
e
e
5
5
5
5
10
10
10
10
m
m
m
m
g
g
g
g
m
m
m
m
5
5
m
m
5
5
m
m
1000
1000
750 m
1000
750
m
m
g
m
g
g
g
750
e
m
g
g
g
g
g
25
25
g
g
10
g
g
5
m
g
e
5
m
10
m
e
Methicillin resistant Staphylococcus aureus (MRSA), Staphylococcus aureus (S. aureus), Klebsiella pneumoniae 1 (K. pneumoniae 1), Shigella flexneri (S. flexneri), Pseudomonas
aeruginosa (P. aeruginosa), Candida albicans (C. albicans).

154
T.S. Lobana et al. / European Journal of Medicinal Chemistry 76 (2014) 145e154
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Acknowledgment
Financial assistance from UGC (BSR) and DST (X-ray diffrac-
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Appendix A. Supplementary data
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