Syntheses, crystal structures, and antibacterial activities of manganese(III), nickel(II), and copper(II) complexes containing a tetradentate Schiff base

Article abstract of DOI:10.1080/00958972.2012.727990

Three new mononuclear Schiff-base complexes, namely [Mn(L)Cl] (1), [Ni(L)] (2), and [Cu(L)] (3), where L = anion of [N,N′-bis(2- hydroxybenzophenylidene)]propane-1,2-diamine, have been synthesized by reacting equimolar amounts of the respective metal chloride and the tetradentate Schiff base, H₂L, in methanol. The complexes have been characterized by microanalytical, spectroscopic, single-crystal X-ray diffraction, and other physicochemical studies. Structural studies reveal that 1 adopts a distorted square-pyramidal geometry whereas 2 and 3 are isotypic with distorted square-planar geometries. The antibacterial activities of 1-3 along with their Schiff base have been tested against some Gram(+) and Gram(-) bacteria.

Full text of DOI:10.1080/00958972.2012.727990

This article was downloaded by: [University of Haifa Library]
On: 13 June 2013, At: 12:16
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered
office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
Journal of Coordination Chemistry
Publication details, including instructions for authors and
subscription information:
http://www.tandfonline.com/loi/gcoo20
Syntheses, crystal structures,
and antibacterial activities of
manganese(III), nickel(II), and
copper(II) complexes containing a
tetradentate Schiff base
Mahendra Ghosh a , Michel Fleck b , Bibekananda Mahanti a ,
Anupam Ghosh c , Guillaume Pilet d & Debasis Bandyopadhyay a
a Department of Chemistry, Bankura Christian College, Bankura
722101, West Bengal, India
b Institute of Mineralogy and Crystallography Geozentrum,
University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria
c Department of Zoology, Bankura Christian College, Bankura
722101, West Bengal, India
d Laboratoire des Multimatériaux et Interfaces, Groupe de
Cristallographie et Ingénierie Moléculaire, UMR 5615 CNRS –
Université Claude Bernard Lyon 1, 2 Avenue Grignard, 69622
Villeurbanne Cedex, France
Accepted author version posted online: 10 Sep 2012.Published
online: 25 Sep 2012.
To cite this article: Mahendra Ghosh , Michel Fleck , Bibekananda Mahanti , Anupam Ghosh ,
Guillaume Pilet & Debasis Bandyopadhyay (2012): Syntheses, crystal structures, and antibacterial
activities of manganese(III), nickel(II), and copper(II) complexes containing a tetradentate Schiff
base, Journal of Coordination Chemistry, 65:22, 3884-3894
To link to this article: http://dx.doi.org/10.1080/00958972.2012.727990
PLEASE SCROLL DOWN FOR ARTICLE
Full terms and conditions of use: http://www.tandfonline.com/page/terms-and-
conditions
This article may be used for research, teaching, and private study purposes. Any
substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing,
systematic supply, or distribution in any form to anyone is expressly forbidden.

The publisher does not give any warranty express or implied or make any representation
that the contents will be complete or accurate or up to date. The accuracy of any
instructions, formulae, and drug doses should be independently verified with primary
sources. The publisher shall not be liable for any loss, actions, claims, proceedings,
demand, or costs or damages whatsoever or howsoever caused arising directly or
indirectly in connection with or arising out of the use of this material.

Journal of Coordination Chemistry
Vol. 65, No. 22, 20 November 2012, 3884–3894
Syntheses, crystal structures, and antibacterial activities of
manganese(III), nickel(II), and copper(II) complexes
containing a tetradentate Schiff base
MAHENDRA GHOSHy, MICHEL FLECKz, BIBEKANANDA MAHANTIy,
ANUPAM GHOSHx, GUILLAUME PILET{ and
DEBASIS BANDYOPADHYAY*y
yDepartment of Chemistry, Bankura Christian College, Bankura 722101, West Bengal, India
zInstitute of Mineralogy and Crystallography Geozentrum, University of Vienna,
Althanstrasse 14, A-1090 Vienna, Austria
xDepartment of Zoology, Bankura Christian College, Bankura 722101, West Bengal, India
{Laboratoire des Multimate
riaux et Interfaces, Groupe de Cristallographie et Ingenierie
´ ´
Moleculaire, UMR 5615 CNRS – Universite Claude Bernard Lyon 1, 2 Avenue Grignard,
´ ´
69622 Villeurbanne Cedex, France
(Received 29 May 2012; in final form 13 August 2012)
Three new mononuclear Schiff-base complexes, namely [Mn(L)Cl] (1), [Ni(L)] (2), and [Cu(L)]
(3), where L ¼ anion of [N,N0-bis(2-hydroxybenzophenylidene)]propane-1,2-diamine, have been
synthesized by reacting equimolar amounts of the respective metal chloride and the tetradentate
Schiff base, H2L, in methanol. The complexes have been characterized by microanalytical,
spectroscopic, single-crystal X-ray diffraction, and other physicochemical studies. Structural
studies reveal that 1 adopts a distorted square-pyramidal geometry whereas 2 and 3 are isotypic
with distorted square-planar geometries. The antibacterial activities of 1–3 along with their
Schiff base have been tested against some Gram(þ) and Gram(ꢀ) bacteria.
Keywords: Manganese(III); Nickel(II); Copper(II); Tetradentate Schiff base; Crystal structure;
Antibacterial activity
1. Introduction
Schiff bases are useful chelating ligands in synthesis of transition metal complexes due
to ease of preparation and structural varieties. Studies on such complexes of
manganese, nickel, or copper have received overwhelming attention due to their
important catalytic, magnetic, and biological properties [1–11]. Many Schiff bases
obtained by condensation of diamines and salicylaldehyde or analogous carbonyl
compounds have been used to synthesize manganese(III), nickel(II), and copper(II)
complexes. However, transition metal complexes of the tetradentate Schiff base, derived
from propane-1,2-diamine and 2-hydroxybenzophenone, have not received much
attention. A limited number of transition metal complexes containing similar
*Corresponding author. Email: dbbccchem@yahoo.co.in
Journal of Coordination Chemistry
ISSN 0095-8972 print/ISSN 1029-0389 online ß 2012 Taylor & Francis
http://dx.doi.org/10.1080/00958972.2012.727990

Mn(III), Ni(II) and Cu(II) complexes
3885
multidentate organic frameworks have been reported [12–17]. Due to their importance
in bioinorganic chemistry, investigation of biological properties of such Schiff bases and
their Mn(III), Ni(II), or Cu(II) complexes continues [18–29].
We describe the syntheses of three new mononuclear complexes of the same Schiff
base with three first row transition metals. [Mn(L)Cl] (1), [Ni(L)] (2), and [Cu(L)] (3)
were obtained by reaction of the corresponding metal chloride and the Schiff base
(H2L) in methanol. The complexes have been characterized by microanalytical,
spectroscopic, and single-crystal X-ray diffraction studies. Structural studies indicate
that 1 is comprised of discrete five-coordinate Mn(III) units with a distorted square-
pyramidal geometry. In contrast, 2 and 3 are isotypic and adopt distorted square-planar
geometries around each metal ion, namely Ni(II) in 2 and Cu(II) in 3. In addition to the
physicochemical studies, 1–3 have been tested in vitro to assess their antibacterial
activities against some common reference bacteria and the results were compared with
similar doses of two commercial antibiotics, namely Gatifloxacin and Ciprofloxacin.
2. Experimental
2.1. Physical measurements
Elemental analyses for carbon, hydrogen, and nitrogen were carried out using a Perkin-
Elmer 2400-II elemental analyzer. Infrared spectra were recorded on a Perkin-Elmer
Spectrum 65 FT-IR spectrophotometer with KBr discs (4000–400 cmꢀ1). Room-
temperature solid-phase magnetic susceptibilities were measured at 298 K with a PAR
155 vibrating sample magnetometer with Hg[Co(NCS)4] as the calibrant. Diamagnetic
corrections were calculated from Pascal’s constants. Molar conductances of the
complexes in dry methanol were measured using a direct reading conductivity meter of
Systronics (Type 304).
2.2. Materials
Commercially available reagent grade 2-hydroxybenzophenone, 1,2-diaminopropane,
manganese(II) chloride tetrahydrate, nickel(II) chloride hexahydrate, copper(II) chlo-
ride dihydrate, and methanol were used without purification. The tetradentate Schiff
base, H2L, was obtained by condensation of 1,2-diaminopropane with 2-hydroxyben-
zophenone using similar methods as described earlier [30].
OH
N
HO
N
CH
3
H L
2

3886
M. Ghosh et al.
2.3. Syntheses of 1–3
Complexes 1–3 were prepared by mixing the respective metal chloride with the Schiff
base in 1 : 1 molar ratio in methanol followed by slow evaporation. For 1, a methanolic
solution (10 mL) of H2L (0.22 g, 0.5 mmol) was added dropwise to a methanolic
solution (10 mL) of MnCl2 ꢁ 4H2O (0.1 g, 0.5 mmol) with constant stirring at room
temperature. Stirring was continued for 15 min and the resulting deep brown solution
was left for slow evaporation at room temperature in a beaker open to the atmosphere.
After a week, deep brown crystals of 1 appeared. The crystals were collected by
filtration, washed with methanol, and finally dried. Yield: 0.16 g (61%). The synthetic
route described for 1 was followed in the preparation of 2 and 3, except that 10 mL
methanolic solution of NiCl2 ꢁ 6H2O (0.12 g, 0.5 mmol) for 2 or CuCl2 ꢁ 2H2O (0.09 g,
0.5 mmol) for 3 was used instead of the manganese salt. Bright red crystals of 2 and
blue crystals of 3 were obtained after 8–10 days. Yields of 2 and 3 were 0.14 g (57%)
and 0.12 g (48%), respectively. Anal. Calcd for C29H24ClMnN2O2 (1) (%): C, 66.61; H,
4.63; N, 5.36. Found (%): C, 66.56; H, 4.58; N, 5.32. FTIR (KBr, cmꢀ1): 1598(s),
1579(s), 1530(s), 1489(m), 1460(m), 1440(s), 1430(m), 1330(s), 1239(m), 1146(s),
847(m), 755(s), 707(m), 622(m). LM (MeOH, ꢀꢀ1 cm2 molꢀ1): 5. ꢀeff (RT, BM): 4.83.
Anal. Calcd for C29H24N2NiO2 (2) (%): C, 70.91; H, 4.92; N, 5.70. Found (%): C,
71.06; H, 4.93; N, 5.72. FTIR (KBr, cmꢀ1): 1599(s), 1580(s), 1530(s), 1458(m), 1439(s),
1431(m), 1347(s), 1242(s), 1134(m), 1008(w), 842(m), 759(s), 707(m), 604(w). LM
(MeOH, ꢀꢀ1 cm2 molꢀ1): 7. Diamagnetic. Anal. Calcd for C29H24CuN2O2 (3) (%): C,
70.22; H, 4.88; N, 5.65. Found (%): C, 69.94; H, 4.85; N, 5.72. FTIR (KBr, cmꢀ1):
1598(s), 1579(s), 1530(s), 1458(m), 1439(s), 1431(m), 1347(s), 1257(m), 1242(s),
1138(m), 841(m), 759(s), 707(m), 604(w). LM (MeOH, ꢀꢀ1 cm2 molꢀ1): 6. ꢀeff (RT,
BM): 1.74.
2.4. Crystal structure determination and refinement
For X-ray diffraction studies, suitable single crystals of 1–3 with approximate
dimensions of 0.15 ꢂ 0.27 ꢂ 0.36, 0.60 ꢂ 0.82 ꢂ 0.95, and 0.08 ꢂ 0.10 ꢂ 0.10 mm3,
respectively, were mounted on a Bruker-Nonius Kappa diffractometer equipped
with
a CCD area detector and employing graphite-monochromated Mo-Ka
radiation. The reflection data were collected and processed using the Bruker-
Nonius program suites COLLECT, DENZO-SMN, and related analysis software
[31–35]. The structures were solved by direct methods and subsequent Fourier and
difference Fourier syntheses, followed by full-matrix least-squares refinements on F2
using SHELX [36]. All non-hydrogen atoms were refined with anisotropic
displacement parameters. Hydrogen atoms were partially located from the
difference Fourier maps, partially placed geometrically and refined keeping
restraints (riding mode). For 2 and 3, several carbon and hydrogen atoms
showed disorder between two distinct positions. Initially, the occupation parameters
for these disordered atoms were refined freely but when it turned out to be refined
around 1/2, they were fixed at this value. A summary of the crystallographic data,
structural parameters, and refinement details for the compounds is presented in
table 1.

Mn(III), Ni(II) and Cu(II) complexes
3887
Table 1. Crystallographic data and refinement parameters for 1–3.
Parameters
1
2
3
Formula
C
522.90
Monoclinic
P21/n
29H24ClMnN2O2
C29H24N2NiO2
491.21
Orthorhombic
P212121
C29H24CuN2O2
496.04
Orthorhombic
P212121
Formula weight (g molꢀ1
Crystal system
Space group
)
ꢃ
˚
Unit cell dimensions (A, )
a
b
c
ꢁ
ꢂ
ꢃ
11.185(1)
17.662(2)
12.617(1)
90
92.36(1)
90
2490.2(3), 4
1.40
0.67
9.781(2)
15.448(3)
15.789(3)
90
90
90
2385.7(8), 4
1.37
0.84
9.792(2)
15.444(3)
15.806(3)
90
90
90
2390.3(8), 4
1.38
0.94
3
˚
Volume (A ), Z
Calculated density (g cmꢀ3
)
Absorption coefficient (mmꢀ1
F(000)
hkl range
)
1080
1024
1028
ꢀ11 ꢄ h ꢄ 14;
ꢀ24 ꢄ k ꢄ 23;
ꢀ16 ꢄ l ꢄ 17
110(2)
0.71069
16,767
6048
ꢀ14 ꢄ h ꢄ 14;
ꢀ22 ꢄ k ꢄ 22;
ꢀ23 ꢄ l ꢄ 23
296(2)
0.71073
8244
8244
ꢀ14 ꢄ h ꢄ 14;
ꢀ23 ꢄ k ꢄ 23;
ꢀ23 ꢄ l ꢄ 23
296(2)
0.71073
27,914
8268
Temperature (K)
Wavelength (Mo-Ka) (A)
Reflections measured
Reflections unique
Data with Fo 4 4ꢄ(Fo)
Rint
˚
4997
0.094
4605
0.124
6155
0.065
Parameters refined
Ra Fo 4 4ꢄ(Fo)
wRb
316
0.078
0.091
–
1.078
356
0.057
0.117
0.06(2)
1.150
356
0.041
0.098
0.02(1)
1.021
Flack parameters
S
ꢀ3
˚
Dꢅmax/Dꢅmin (e A
)
1.68 and ꢀ0.87
0.47 and ꢀ0.41
0.34 and ꢀ0.40
aR ¼ ꢁ(jjFoj ꢀ jFcjj)/ꢁjFoj.
2
1=2
2
bwR ¼ ½ꢁwðFo2 ꢀ Fc2Þ =ꢁwFo4ꢅ , w ¼ 1=½ꢄ 2ðFo2Þ þ ða ꢂ PÞ þ b ꢂ Pꢅ, P ¼ ðFo2 þ 2Fc2Þ=3.
2.5. Antibacterial screening
Antibiograms of 1–3 and two reference commercial antibiotics, namely Gatifloxacin
and Ciprofloxacin (purchased in powder form from Span Diagnostic Limited, Surat,
India), were prepared against two Gram-positive bacteria (Staphylococcus aureus
MTCC 2940 and Bacillus subtilis MTCC 441) and two Gram-negative bacteria
(Pseudomonas aeruginosa MTCC 2453 and Escherichia coli MTCC 739) using the agar
well diffusion method on nutrient agar medium with necessary modifications [37].
During the experiment, the test microbes were removed from the slant aseptically with
inoculating loops and transferred to separate test tubes containing 5.0 mL of saline
solution (0.85% NaCl). Sufficient inoculums were then added to adjust the turbidity to
0.5 McFarland (108 CFU mLꢀ1), as recorded in a digital colony counter. For each
bacterium, 1.0 mL of the suspension was added to 15–20 mL of nutrient agar and
transferred to an agar plate of 9.0 cm diameter. The antibacterial activities of the
compounds were tested after cooling the inoculated agar at room temperature for
25 min. The antibacterial activities of propane-1,2-diamine (DAP), 2-hydroxybenzo-
phenone (HBP) and H2L were also evaluated during the same experiment. All the
compounds including the antibiotics were dissolved in DMSO to prepare five different

3888
M. Ghosh et al.
concentrations (0.2, 0.4, 0.6, 0.8, and 1.0 mg mLꢀ1) for evaluation of limiting doses.
Wells of 0.6 cm diameter were pierced in the agar and filled with the test compounds of
varied concentrations and incubated for 24 h at 303 K for B. subtilis and at 310 K for all
other bacteria. Antibacterial activities were evaluated by measuring the inhibition zone
diameters (IZDs) and their minimum inhibitory concentrations (MICs). MIC is the
lowest concentration of a compound in DMSO that exhibited no visual growth of the
organisms in the culture tubes. Such value of the test compounds was determined by
the serial dilution technique adopted by the National Committee for Clinical
Laboratory Standards [38]. Each of the above experiments was repeated thrice along
with a control set using DMSO. The mean value obtained for three individual replicates
was then used to calculate the growth inhibition zone of each sample.
3. Results and discussion
3.1. Syntheses
Complexes 1–3 were obtained by reaction of the respective metal chloride with a
tetradentate Schiff base in 1 : 1 molar ratio in methanol. MnII underwent aerial
oxidation to MnIII during formation of 1 to form a more stable complex with ligand
containing harder donors [30, 39]. As a result, the pentacoordinate 1 has Mn(III) with a
square-pyramidal geometry with a chloride in the apical position. However, both Ni(II)
and Cu(II) formed square planar 2 and 3, respectively, containing the NNOO donor
Schiff base only. The complexes have been characterized by elemental analysis, IR
spectroscopy, electrical conductivity, and magnetic susceptibility as well as by single-
crystal X-ray structural analysis. In methanol, these compounds behave as non-
electrolytes as evident from LM values (ca 5–7 ꢀꢀ1 cm2 molꢀ1). Room-temperature
magnetic susceptibility measurements show that 1 and 3 possess magnetic moment
values of 4.83 and 1.74 B.M., respectively, close to the spin-only values of Mn(III) and
Cu(II). These observations are consistent with discrete and magnetically non-coupled d4
system in 1 and d9 system in 3. As expected, 2 is diamagnetic showing square-planar low
spin 3d8 system. All these results along with those of X-ray structural analysis are
consistent with the proposed mononuclear formulae of 1–3.
3.2. FTIR spectra
Infrared spectra of 1–3 have some common features as expected from their structural
similarities. All exhibit strong absorptions at 1579–1580 and 1598–1599 cmꢀ1 corre-
sponding to C¼N stretch [ꢆCN] of the Schiff-base ligands. All other vibrations including
the phenolic C–O stretch of metal-bound Schiff bases are located in the range
600–1600 cmꢀ1, in agreement [40] with the respective structural features of the Schiff-
base complexes.
3.3. Crystal structures of 1–3
The molecular structures of 1–3 are displayed in figure 1 and some selected bond
distances and angles are listed in table 2. The molecular unit of each complex can be

Mn(III), Ni(II) and Cu(II) complexes
3889
Figure 1. Molecular structures of (a) 1 and (b) 2 (M ¼ Ni2þ) or 3 (M ¼ Cu2þ).
ꢃ
˚
Table 2. Selected bond lengths (A) and angles ( ) for 1–3.
1
2
3
Mn1–O1
Mn1–N1
Mn1–N2
Mn1–O2
Mn1–Cl1
1.864(2)
2.002(3)
2.001(3)
1.873(2)
2.355(1)
Ni1–O1
Ni1–N1
Ni1–N2
Ni1–O2
1.887(2)
1.934(3)
1.944(3)
1.877(2)
Cu1–O1
Cu1–N1
Cu1–N2
Cu1–O2
1.886(2)
1.942(2)
1.943(2)
1.877(2)
O1–Mn1–O2
O1–Mn1–N1
O1–Mn1–N2
O2–Mn1–N1
O2–Mn1–N2
N1–Mn1–N2
Cl1–Mn1–O2
Cl1–Mn1–N2
Cl1–Mn1–N1
Cl1–Mn1–O1
89.56(1)
90.08(1)
158.66(1)
158.67(1)
89.26(1)
83.42(1)
101.57(8)
101.06(9)
99.49(1)
100.05(1)
O1–Ni1–O2
O1–Ni1–N1
O1–Ni1–N2
O2–Ni1–N1
O2–Ni1–N2
N1–Ni1–N2
88.98(1)
92.25(1)
178.61(1)
178.73(1)
92.34(1)
86.42(1)
O1–Cu1–O2
O1–Cu1–N1
O1–Cu1–N2
O2–Cu1–N1
O2–Cu1–N2
N1–Cu1–N2
88.84(8)
92.66(9)
178.25(9)
178.43(9)
92.89(8)
85.61(9)
described as a butterfly-like arrangement around a metal cation by the Schiff-base
anion (L2ꢀ) with four of its aromatic rings disposed as wings. X-ray studies reveal that
each central ion in 1–3 is a member of one five-membered and two six-membered rings.
A distorted square-pyramidal geometry is adopted by 1, whereas 2 and 3 are distorted
square planar. The torsion angles (O1–N1–N2–O2) for 1, 2, and 3 are ꢀ0.07, 0.13, and
ꢀ0.16ꢃ, respectively. The irregular five-coordinate environment (figure 1a) around
Mn(III) in 1 is maintained by a chloride (Cl1) at the apical position and two imino
nitrogen atoms (N1, N2) plus two phenolate oxygen atoms (O1, O2) in the basal plane.
As expected, the Mn–N bond distances are greater than Mn–O bonds; bond distances
˚
ranging from 1.864 to 2.002 A agree well with similar Schiff-base complexes of
manganese(III) [20, 39]. Distortion in the coordination sphere of Mn(III) from ideal
geometry is obvious due to structural constraints imposed by the polydentate ligand
framework. However, distortion is less pronounced in 1 as reflected by cisoid and
transoid angles, being much closer to the ideal values. The observed bond angles thus
indicate that Mn(III) is slightly above the square base.
Apart from the additional chloride which gives a different geometry of 1, there is
another notable difference between 1 and 2 or 3 (figure 1). The isopropyl part between

3890
M. Ghosh et al.
Figure 2. Disordered parts of 2 and 3 in ball-and-stick representation. Isopropyl chains containing the
carbon atoms C14, C15, and C16 (labeled a or b) are half-occupied. Notice that some hydrogen atoms (H16a,
H16b) belong only to one half, i.e. half-occupied, while others belong to both positions (H14a, H14b, H14c,
H16c, H16d), i.e. fully occupied.
the imino nitrogen atoms of the Schiff base is disordered in both 2 and 3 (figure 2).
While the position of C16 of the methyl group is clearly located in 1, there are two
different half-occupied positions for this atom in 2 and 3 (labeled as C16a and b in
figure 2). Thus, the C16 atom as well as the whole isopropyl chain is split between two
positions. In each molecule of the lattice, the chain faces either from left to right or from
right to left. These two alternatively occupied chains or orientations are represented by
the atoms C14a, C15a, C16a in one case and C14b, C15b, C16b in the other (figure 2).
As a consequence of this disorder, hydrogen atoms of this part of the molecule are also
disordered. Five hydrogen positions overlap in both configurations and hence H14a,
H14b, H14c, H16c, and H16d are fully occupied. Although these atoms may not share
the same positions exactly, it was impossible to distinguish two slightly overlapping,
half-occupied hydrogen positions in the refinement. Hydrogen atoms H16a and H16b
are properly half-occupied since these are realized only in one conformation. As the
same disorder was found in both 2 and 3, they were modeled independently to obtain
virtually the same geometry of the Ni(II) and Cu(II) complexes.
Unaffected by the above disorder, M (where M ¼ Ni2þ in 2 and Cu2þ in 3) is
coordinated by the tetradentate Schiff base in the same manner as for 1 to form the
square base (figure 1). Thus, in both 2 and 3, MN2O2 chromophores constitute the
distorted square-planar arrangement in which the four coordination of the metal is
completed by the same two imino nitrogen atoms (N1, N2) and two phenolate oxygen
atoms (O1, O2) donated by L2ꢀ. Although both 2 and 3 undergo slight distortions from
ideal geometry due to the asymmetric nature of the Schiff base, they are isotypic, which
is reflected in their very similar magnitudes of bond parameters. All relevant bond
distances and angles are also comparable to other analogous Schiff-base complexes of
Ni(II) and Cu(II) [6–10].
The crystal packing diagrams of 1–3 are presented in figure 3. The molecules are
packed rather loosely in herringbone patterns and isolated from each other in their
crystal lattices. Weak intermolecular van der Waals and ꢇꢁ ꢁ ꢁꢇ interactions are operative
to hold the molecules together in the solid state.

Mn(III), Ni(II) and Cu(II) complexes
3891
Figure 3. Structural packing diagrams of (a) 1 viewed along [0 0 1] direction and (b) 2 or 3 viewed along
[1 0 0] direction. Hydrogen atoms are omitted for clarity.
3.4. Antibacterial activities of the compounds
The antibacterial potential of the compounds against four chosen bacteria is presented
as their IZD and MIC values in tables 3 and 4, respectively. The results of the
antibacterial screening indicate that 1–3 exhibit broad spectrum antibacterial activity
against all four reference bacteria. However, they possess rather high MIC and low IZD
values. The highest IZD and lowest MIC values are observed in 2 and 3, suggesting that
the Ni(II) and Cu(II) complexes are most susceptible to the reference bacteria.
Although both 2 and 3 are more active toward S. aureus, 2 possesses better bactericidal

3892
M. Ghosh et al.
Table 3. Antibacterial activities of 1–3 and related compounds compared to control and standard
antibiotics.
IZD (mean ꢆ standard error) (cm)
Gram-positive bacteria
Gram-negative bacteria
Compounds
Dose (mg mLꢀ1
)
S. aureus
B. subtilis
P. aeruginosa
E. coli
1
1.0
0.8
0.6, 0.4, 0.2
1.4 ꢆ 0.3
1.1 ꢆ 0.3
–
1.2 ꢆ 0.3
1.4 ꢆ 0.6
1.1 ꢆ 0.3
–
1.4 ꢆ 0.3
1.1 ꢆ 0.3
–
–
–
2
1.0
0.8
0.6
0.4
0.2
1.9 ꢆ 0.7
1.5 ꢆ 0.3
1.4 ꢆ 0.3
1.0 ꢆ 0.3
–
1.9 ꢆ 0.7
1.6 ꢆ 0.3
1.3 ꢆ 0.6
1.1 ꢆ 0.3
–
1.8 ꢆ 0.3
1.4 ꢆ 0.7
1.2 ꢆ 0.3
1.000 ꢆ 0.000
–
1.6 ꢆ 0.3
1.4 ꢆ 0.3
1.1 ꢆ 0.3
–
–
3
1.0
0.8
0.6
0.4
0.2
2.0 ꢆ 0.3
1.6 ꢆ 0.3
1.4 ꢆ 0.3
1.4 ꢆ 0.3
1.1 ꢆ 0.3
1.6 ꢆ 0.3
1.4 ꢆ 0.3
1.1 ꢆ 0.3
1.1 ꢆ 0.3
–
1.7 ꢆ 0.6
1.4 ꢆ 0.3
1.6 ꢆ 0.3
1.3 ꢆ 0.6
1.2 ꢆ 0.3
1.000 ꢆ 0.000
–
1.1 ꢆ 0.3
1.1 ꢆ 0.3
1.000 ꢆ 0.000
H2L
1.0
0.8
0.6
0.4
0.2
1.3 ꢆ 0.6
1.2 ꢆ 0.3
1.2 ꢆ 0.3
1.000 ꢆ 0.000
–
1.4 ꢆ 0.3
1.3 ꢆ 0.3
1.4 ꢆ 0.3
1.1 ꢆ 0.3
1.1 ꢆ 0.3
1.000 ꢆ 0.000
–
1.1 ꢆ 0.3
1.2 ꢆ 0.3
–
–
–
–
–
–
DAP
1.0
0.8
0.6, 0.4, 0.2
1.2 ꢆ 0.3
1.1 ꢆ 0.3
–
–
–
–
–
–
–
1.2 ꢆ 0.3
1.000 ꢆ 0.000
–
HBP
1.0
0.8
0.6, 0.4, 0.2
–
–
–
1.1 ꢆ 0.3
1.1 ꢆ 0.3
–
1.1 ꢆ 0.3
1.000 ꢆ 0.000
–
–
–
–
Gatifloxacin
1.0
0.8
0.6
0.4
0.2
2.6 ꢆ 0.6
2.2 ꢆ 0.3
2.0 ꢆ 0.7
1.9 ꢆ 0.7
1.6 ꢆ 0.3
2.7 ꢆ 0.6
2.2 ꢆ 0.3
1.9 ꢆ 0.7
1.6 ꢆ 0.3
1.4 ꢆ 0.3
2.5 ꢆ 0.3
2.2 ꢆ 0.3
1.8 ꢆ 0.3
1.5 ꢆ 0.3
1.4 ꢆ 0.3
2.6 ꢆ 0.3
2.4 ꢆ 0.7
2.0 ꢆ 0.3
1.6 ꢆ 0.3
1.4 ꢆ 0.3
Ciprofloxacin
1.0
0.8
0.6
0.4
0.2
2.4 ꢆ 0.6
2.1 ꢆ 0.7
1.8 ꢆ 0.7
1.5 ꢆ 0.3
1.1 ꢆ 0.3
2.3 ꢆ 0.3
2.2 ꢆ 0.3
1.8 ꢆ 0.3
1.4 ꢆ 0.7
1.2 ꢆ 0.3
2.1 ꢆ 0.3
2.0 ꢆ 0.3
1.7 ꢆ 0.3
1.4 ꢆ 0.3
1.1 ꢆ 0.3
2.6 ꢆ 0.3
2.4 ꢆ 0.6
1.9 ꢆ 0.7
1.4 ꢆ 0.3
1.000 ꢆ 0.000
Control (DMSO)
0.2–1.0
–
–
–
–
property than 3 against B. subtilis and P. aeruginosa. In contrast, 1 exhibits very poor
antibacterial activity against all the bacteria and its MIC values are quite high. The
antibacterial properties of 2 and 3 are appreciably higher but that of 1 does not differ
much from the Schiff base (H2L). Although the Schiff base is mildly active against the
bacteria at rather high concentrations, its constituents are not very active. The IZD data
show that DAP is active against S. aureus and E. coli but is inactive against B. subtilis or
P. aeruginosa whereas the reverse is seen for HBP. Among all the bacteria, E. coli is
least susceptible against all the complexes.

Mn(III), Ni(II) and Cu(II) complexes
3893
Table 4. MIC values (mg mLꢀ1) of 1–3 for different bacteria.
Compounds
S. aureus
B. subtilis
P. aeruginosa
E. coli
1
2
50.8
50.4
50.2
50.4
50.8
41.0
50.2
50.2
51.0
50.4
50.4
50.8
41.0
50.8
50.2
50.2
50.8
50.4
50.2
50.8
41.0
50.8
50.2
50.2
50.8
50.6
50.4
50.4
50.8
41.0
50.2
50.2
3
H2L
DAP
HBP
Gatifloxacin
Ciprofloxacin
From the in vitro antibacterial assay, most of the tested compounds are found to
possess mild to moderate antibacterial activities which increase with dose. However, the
activities are much lower than those of the tested commercial antibiotics at similar
concentrations. These results suggest that antibacterial activities of the complexes are
affected by ligand as well as metal ions. These observations are similar to earlier reports
[18–29] of bioactivities of analogous first row transition metal Schiff-base complexes.
4. Conclusion
Synthesis and characterization of mononuclear Schiff-base complexes of three first row
transition metals containing a less-studied tetradentate Schiff base are described in this
article. The same reaction mixture yielded a square-pyramidal complex in the presence
of MnCl2 and square-planar complexes in the presence of either NiCl2 or CuCl2.
Antibacterial screening of the compounds indicate mild to moderate bactericidal
activities which are comparable to those of the previously reported Mn(III), Ni(II), and
Cu(II) Schiff-base complexes [18–29]. In addition to the synthetic and structural
investigations, this study describes the antibacterial potential of a Schiff base and its
complexes.
Supplementary material
CCDC 855 538–855540 contain the supplementary crystallographic data for 1–3.
These data can be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/
retrieving.html, or from the Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; Fax: (þ44) 1223-336-033; or E-mail: deposit@
ccdc.cam.ac.uk
Acknowledgments
One of the authors (BM) gratefully acknowledges the financial support under MRP
[No. F. PSW-002/09-10 (ERO)] from UGC, Eastern region, Kolkata, India. They thank

3894
M. Ghosh et al.
Rt. Revd Dr P.K. Dutta (Chairman of Governing Body) and Dr R.N. Bajpai
(Principal) of Bankura Christian College for their constant encouragement and valuable
suggestions during this work. They also thank Mr Kalyan Dana for his assistance.
References
[1] V.L. Pecoraro, W.-Y. Hsieh. In Metal Ions in Biological Systems: Manganese and its Role in Biological
Processes, A. Sigel, H. Sigel (Eds), Vol. 37, p. 431, Marcel Dekker, New York, NY (2000).
[2] J.J.R. Frau´ sto da Silva, R.J.P. Williams. The Biological Chemistry of the Elements, Oxford University
Press, Oxford (2001).
[3] E.M. McGarrigle, D.G. Gilheany. Chem. Rev., 105, 1563 (2005).
[4] Reviews: O. Kahn. Molecular Magnetism, VCH, Weinheim (1993).
[5] J.R. Lancaster (Ed.). The Bioinorganic Chemistry of Nickel, VCH, New York, NY (1988).
[6] E. Fujita, B.S. Brunschwig, T. Ogata, S. Yanagida. Coord. Chem. Rev., 132, 195 (1994).
[7] P.G. Cozzi. Chem. Soc. Rev., 33, 410 (2004).
[8] E.I. Solomon, U.M. Sundaram, T.E. Machokin. Chem. Rev., 96, 2563 (1996).
[9] G. Wilkinson. Comprehensive Coordination Chemistry, Vol. 5, p. 775, Pergamon Press, Oxford (1987).
[10] K.D. Karlin, J. Zubieta (Eds). Copper Coordination Chemistry, Biochemical and Inorganic Perspectives,
Adenine Press, Guilderland, NY (1983).
[11] M.R. Bermejo, M.I. Fernandez, E. Gomez-Forneas, A. Gonzalez-Noya, M. Maneiro, R. Pedrido,
´ ´ ´ ´
M.J. Rodrıguez. Eur. J. Inorg. Chem., 3789 (2007).
´
[12] R. Atkins, G. Brewer, E. Kokot, G.M. Mockler, E. Sinn. Inorg. Chem., 24, 127 (1985).
[13] C. Bi, Y. Fan, L.-J. Liu. Synth. React. Inorg. Met.-Org. Chem., 34, 687 (2004).
[14] P. Gluvchinsky, G.M. Mockler, P.C. Healy, E. Sinn. J. Chem. Soc., Dalton Trans., 1156 (1974).
[15] H. Han, W.-J. Ruan, X.-J. Zhao, G.-H. Hu, Z.-A. Zhu. Synth. React. Inorg. Met.-Org. Chem., 33, 1011
(2003).
[16] E.-P. Luo, Y.-Q. Chai, R. Yuan. Anal. Lett., 40, 369 (2007).
[17] A.A. El-Asmy, G.A.A. Al-Hazmi. Spectrochim. Acta A, Mol. Biomol. Spectrosc., 71, 1885 (2009).
_
¨
[18] H. Temel, U. C¸ akir, B. Otludil, H.I. Ugras¸. Synth. React. Inorg. Met.-Org. Chem., 31, 1323 (2001).
˘
[19] B. Samanta, J. Chakraborty, C. Choudhury, S. Dey, D. Dey, S. Batten, P. Jensen, G. Yap, S. Mitra.
Struct. Chem., 18, 33 (2007).
[20] S. Mandal, A.K. Rout, A. Ghosh, G. Pilet, D. Bandyopadhyay. Polyhedron, 28, 3858 (2009).
[21] D.P. Singh, M. Kamboj, K. Kumar, K. Jain, C. Sharma. J. Coord. Chem., 64, 502 (2011).
[22] N. Nishat, S.A. Khan, S. Parveen, R. Rasool. J. Coord. Chem., 63, 3944 (2010).
´
[23] M.A. Va
´
M.J. Rodrı
zquez-Fernandez, M.I. Fernandez-Garcıa, G. Gonzalez-Riopedre, M. Maneiro,
´ ´ ´ ´
guez-Douton. J. Coord. Chem., 64, 3843 (2011).
´
´
[24] A. Vijayaraj, R. Prabu, R. Suresh, C. Sivaraj, N. Raaman, V. Narayanan. J. Coord. Chem., 64, 637 (2011).
[25] M. Rajasekar, S. Sreedaran, R. Prabu, V. Narayanan, R. Jegadeesh, N. Raaman, A.K. Rahiman.
J. Coord. Chem., 63, 136 (2010).
[26] N. Raman, K. Pothiraj, T. Baskaran. J. Coord. Chem., 64, 4286 (2011).
[27] M. Manjunatha, V.H. Naik, A.D. Kulkarni, S.A. Patil. J. Coord. Chem., 64, 4264 (2011).
[28] A.A. Nejo, G.A. Kolawole, M.C. Dumbele, A.R. Opoku. J. Coord. Chem., 63, 4367 (2010).
[29] T.K. Karmakar, M. Ghosh, M. Fleck, G. Pilet, D. Bandyopadhyay. J. Coord. Chem., 65, 2612 (2012).
[30] S. Mandal, G. Rosair, J. Ribas, D. Bandyopadhyay. Inorg. Chim. Acta, 362, 2200 (2009).
[31] NONIUS. Kappa CCD Program Package: COLLECT, DENZO, SCALEPACK, SORTAV, Nonius BV,
Delft (1999).
[32] Z. Otwinowski, W. Minor. Methods Enzymol. A, 276, 307 (1997).
[33] A. Altomare, M.C. Burla, M. Camalli, G.L. Cascarano, C. Giacovazzo, A. Guagliardi,
A.G.G. Moliterni, G. Polidori, R. Spagna. J. Appl. Cryst., 32, 115 (1999).
[34] D.J. Watkin, C.K. Prout, J.R. Carruthers, P.W. Betteridge. CRYSTALS 11, Chemical Crystallography
Laboratory, Oxford (1999).
[35] H.D. Flack. Acta Crystallogr., Sect. A, 39, 876 (1983).
[36] G.M. Sheldrick. Acta Crystallogr., Sect. A, 64, 112 (2008).
[37] C. Perez, M. Paul, P. Bazerque. Acta Biol. Med. Exp., 15, 113 (1990).
[38] National Committee for Clinical Laboratory Standards, Performance Standards for Antimicrobial Disc
Susceptibility Tests. Approved Standard NCCLS Publications. M2-A5, Villanova (1993).
[39] S. Mandal, A.K. Rout, M. Fleck, G. Pilet, J. Ribas, D. Bandyopadhyay. Inorg. Chim. Acta, 363, 2250
(2010).
[40] K. Nakamoto. Infrared and Raman Spectra of Inorganic and Coordination Compounds, 6th Edn, Wiley &
Sons, New Jersey (2009).