A zig-zag end-to-end azido bridged MnIII 1-D coordination polymer: Spectral elucidation, magnetism, redox study and biological activity

Article abstract of DOI:10.1016/j.poly.2017.02.017

A zig-zag one-dimensional Mn(III) coordination polymer, {[C₆H₄(O)CHN(CH₂)₂NCH(O)C₆H₄]Mn(N₃)}_n (1) has been synthesized reacting a manganese salt with the Schiff base precursor H₂L, obtained condensing salicyldehyde and ethylenediamine. The compound has been characterized by IR, UV–Vis and EPR spectroscopy. Single crystal X-ray diffraction studies have revealed that the Mn atom possesses a distorted octahedral environment and the metals connected by end-to-end azido ligands lead to the formation of 1-D zig-zag molecular chains. Temperature dependent magnetic studies have shown the presence of weak anti-ferromagnetic coupling among the Mn centers. Cyclic voltammetry has evidenced the presence of a reversible redox couple for the Mn³⁺/Mn²⁺ system. Both the ligand and complex 1 exhibit anti-mycobacterial activity and considerable efficacy on Mycobacterium tuberculosis H37Rv ATCC 27294 and M. tuberculosis H37Ra ATCC 25177 strains. The cytotoxicity study on different human cancer cell lines (Caco 2, MCF7 and A549) suggests that complex 1 has potential anticancer properties.

Full text of DOI:10.1016/j.poly.2017.02.017

Accepted Manuscript
A zig-zag end-to-end azido bridged MnIII 1-D coordination polymer: Spectral
elucidation, magnetism, redox study and biological activity
Kuheli Das, Amitabha Datta, Belete B. Beyene, Chiara Massera, Eugenio
Garribba, Chittaranjan Sinha, Takashiro Akitsu, Shinnosuke Tanka
PII:
S0277-5387(17)30127-4
DOI:
http://dx.doi.org/10.1016/j.poly.2017.02.017
POLY 12484
Reference:
Polyhedron
To appear in:
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Revised Date:
Accepted Date:
21 December 2016
10 February 2017
12 February 2017
Please cite this article as: K. Das, A. Datta, B.B. Beyene, C. Massera, E. Garribba, C. Sinha, T. Akitsu, S. Tanka,
A zig-zag end-to-end azido bridged MnIII 1-D coordination polymer: Spectral elucidation, magnetism, redox study
and biological activity, Polyhedron (2017), doi: http://dx.doi.org/10.1016/j.poly.2017.02.017
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A zig-zag end-to-end azido bridged MnIII 1-D coordination polymer:
Spectral elucidation, magnetism, redox study and biological activity
Kuheli Dasa,b, Amitabha Dattaa,b,*, Belete B. Beyenea, Chiara Masserac, Eugenio
Garribbad, Chittaranjan Sinhab,*, Takashiro Akitsue, Shinnosuke Tankae
aInstitute of Chemistry, Academia Sinica, Nankang – 105, Taipei, Taiwan
bDepartment of Chemistry, Jadavpur University, Kolkata – 700032, India
cDipartimento di Chimica, Universita` degli Studi di Parma, Viale delle Scienze,
17/A, 43124 Parma, Italy
dDipartimento di Chimica e Farmacia, Università di Sassari, Via Vienna 2, I-07100
Sassari, Italy
eDepartment of Chemistry, Faculty of Science, Tokyo University of Science, 1-3
Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan
*Corresponding authors. amitd_ju@yahoo.co.in (A. Datta); c_r_sinha@ yahoo.com
(C. Sinha)

A B S T R A C T
zig-zag
A
one-dimensional
Mn(III)
coordination
polymer,
{[C6H4(O)CHN(CH2)2NCH(O)C6H4]Mn(N3)}n (1) has been synthesized reacting a
manganese salt with the Schiff base precursor H2L, obtained condensing
salicyldehyde and ethylenediamine. The compound has been characterized by IR,
UV-vis and EPR spectroscopy. Single crystal X-ray diffraction studies have revealed
that the Mn atom possesses a distorted octahedral environment and the metals
connected by end-to-end azido lignads lead to the formation of 1-D zig-zag molecular
chains. Temperature dependent magnetic studies have shown the presence of weak
anti-ferromagnetic coupling among the Mn centers. Cyclic voltammetry has
evidenced the presence of a reversible redox couple for the Mn3+/Mn2+ system. Both
the ligand and complex 1 exhibit anti-mycobacterial activity and considerable efficacy
on M. tuberculosis H37Rv ATCC 27294 and M. tuberculosis H37Ra ATCC 25177
strains. The cytotoxicity study on different human cancer cell lines (Caco 2, MCF7
and A549) suggests that complex 1 has potential anticancer properties.
_____________________________________________________________________
Keywords: Mn(III); Coordination polymer; Spectra; Cyclic voltammetry; Biological
property

1. Introduction
The rational design and synthesis of novel coordination compounds based on
transition metals and multifunctional bridging ligands is of great research interest, due
to their interesting frameworks and potential applications as functional materials.
Schiff base metal complexes are very important tools for inorganic chemists as they
are widely used in constructing supramolecular architectures such as coordination
polymers or double and triple helicates [1,2]. Additionally, they can be employed in a
variety of applications, for instance as antibacterial and antifungal agents [3], in
homogeneous or heterogeneous catalysis [4-7] and magnetism [8]. There are
numerous accounts in the literature describing the chemistry of metal complexes of
Schiff base ligands containing two, three, four, five and six donor atoms [9].
Multidentate Schiff bases with NO donor atoms have been often used to block the
coordination sites of metal ions which prefer square planar or square pyramidal
geometry and to saturate the coordination number of the metal ion. A bridging ligand
has been used to synthesize multinuclear metal complexes [10-13]. The nature and the
tuning of magnetic interactions between metal centres are crucial points in the
conception of molecule-based magnetic materials [14-18]. The manganese(III)
salen-type compounds are generally in equilibrium between the monomeric and the
dimeric species, their solid state form depending on the steric characteristics of the

salen-type Schiff bases [14]. Dimeric manganeses(III) complexes generally exhibit an
antiferromagnetic intra-dimer interaction which is very well explored [19-23], but a
few examples of ferromagnetic interactions have been reported as well [24-27].
Pseudohalide coligands, such as cyanide, azide, thiocyanate, and dicyanamide (dca),
have been utilized to bridge transition metal–Schiff base complexes, in order to
explore and modify their magnetic properties and network topology, as well as to
increase the dimensionality of the resulting coordination polymers [28-30]. Magnetic
interactions between the metal centers of such complexes can be tuned by skillful
control of the chain length and the byte angle of the bridging ligands, and in this
respect the azide ion plays a significant role. The different binding modes of the azide
-
ion are shown in Scheme 1. The end-to-end or 1,3-coordination mode of N3 generally
results in antiferromagnetic coupling between the metal centres but if the bond angle
in M-µ1,3-N3-M is very large, then the sign of the coupling may be reversed [31-37].
In contrast, the end-on or 1,1-coordination mode produces ferromagnetic coupling,
but the ferromagnetic ordering between the metal centers is reduced if the bridging
byte angle exceeds 108° [38]. Tuberculosis, which is caused primarily by
Mycobacterium tuberculosis and rarely by M. bovis and M. africanum, is one of the
oldest disease in the world affecting lungs and spreading to the other organs [39]. At
present, a million children per year has died from this disease [40]. Mycobacteria

resist to many chemicals, disinfectant antibiotics and chemotherapeutical agents
[41,42]. Mycobacteria show a strong resistance to most of the antibiotics and
chemicals due to the low permeability of the mycobacterial cell wall. Porins in the
thickness and low permeability of this bilayer membrane allow inefficient
permeability of the substances [42]. The prospect of developing new and affective
drugs is central to the global control of tuberculosis. As an extension of earlier work,
we report one zig-zag end-to-end azido bridged Mn(III) 1-D coordination polymer
{[H2L]Mn(N3)}n (1), where H2L = C6H4(OH)CH=N-CH2CH2-N=CH(OH)C6H4. We
have systematically characterized the compound by X-ray diffraction spectrometry, as
well as by IR and UV-vis studies. Temperature and solvent dependent EPR spectra
have been also obtained and discussed. Besides studying the magnetic and cyclic
voltammetric properties, we have also focused our attention on the anti-mycobacterial
activity on human tuberculosis cells like M. tuberculosis H37Rv ATCC 27294 and M.
tuberculosis H37Ra ATCC 25177 strains.
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
(c)
(d)
(e)
(b)
(a)
Scheme 1. Different binding modes of the azide ion.

2. Results and discussion
2.1. Description of crystal structure
The ligand, (H2L) [C6H4(OH)CH=N-CH2CH2-N=CH(OH)C6H4] was prepared by the
condensation of salicyldehyde and ethylenediamine (2:1 mole proportion) in methanol
[43]. H2L reacted with Mn(CCl3COO)2.4H2O in the same solvent to yield compound
1
which was crystallized by slow evaporation. Single-crystal X-ray analysis
revealed that compound 1 crystallizes in the orthorhombic space group Pca21. As
shown in Figure 1, the monomeric unit consists of one Mn ion, one ligand L2- and a
coordinating azide. The resulting coordination around each Mn ion is therefore
octahedral; the vertexes are occupied by the azide nitrogen atoms N3 and N5a, while
the equatorial plane is occupied by the atoms O1, O2, N1 and N2 of the tetradentate
Schiff base ligand. In the lattice, the different chains are stabilized by C-H···N
contacts.

Figure 1. Molecular structure of the monomeric unit [Mn(L)(N3)] with partial
labelling scheme.
Due to Jahn-Teller effect, the Mn-N bond distances in the apical position (Mn(1)–N(3)
= 2.270(7) Å and Mn(1)–N(5a) = 2.311(7) Å) are significantly longer than those in
the equatorial plane (Mn(1)–O(1) = 1.895(5) Å, Mn(1)‒O(2) = 1.872(5) Å and
Mn(1)–N(1) = 1.976(6) Å, Mn(1) = N(2) = 1.987(6) Å) (see Table 1). These values
are similar to those of other reported complexes with the same [MnN4O2]
coordination sphere [44]. The basal bond angles are all close to 90° with the exception
of the N(1)–Mn(1)–N(2) bite angle (81.96 (8)°) which is considerably smaller. The
monomeric unit is repeated along the b axis of the unit cell, to yield a zig-zag
polymeric chain in which the metal centers are connected through the nitrogen atoms
of symmetry-related azide ligands. The one-dimensional polymeric chain in which the
azide ions are coordinated in end-to-end fashion is depicted in Figure 2. The bridging
(N3)- anions are practically linear, with N3-N4-N5 bond angles of 179.4(5)°. One of
the phenyl rings of the Schiff base

Figure 2. View of the 1D polymer along the b axis of the unit cell. Hydrogen atoms
have been omitted for clarity. a: 1,5-x; ½+y; z.
ligand (C4–C9), (see Figure S1 for the complete labeling scheme) is slightly twisted
out of the central hydrazine moiety by the dihedral angle of 16.47° (Figure 2). All
manganese atoms along the chain are localized in the same plane with intra-chain
Mn-Mn distances of 5.535(3) Å. The shortest inter-chain metal–metal separation in
the lattice is 7.120(2) Å.
Table 1. Selected geometric parameters (Å, °) for 1.
Mn1-O1
Mn1-O2
Mn1-N1
Mn1-N2
Mn1-N3
1.895(5)
1.872(5)
1.976(6)
1.987(6)
2.270(7)
N3-Mn1-N5a
O1-Mn1-O2
N1-Mn1-N2
O1-Mn1-N1
O2-Mn2-N2
176.96(8)
94.02(9)
81.96(8)
92.03(9)
92.09(9)

Mn1-N5a
2.311(7)
5.535(3)
Mn1•••MMnn11a
a: 1,5-x; ½+y; z
2.2. IR spectra
From the IR spectroscopic analysis, the strong absorption band corresponding to νN≡N
of the azido ligand appears at 2029 cm-1. The band at 1614 cm-1 is attributable to νC=N
(imine bond) and this band shifts to a lower frequency region compared to that
obtained for the respective free ligand [at 1640 cm-1 (H2L)] [45]. Ligand coordination
with the manganese ion is substantiated by two types of bands at 445 cm-1 and 361
cm-1, corresponding to νMn–N and νMn–O, respectively.
2.3. Electronic spectra
The electronic spectra of compound 1 comprises two absorption regions. It shows
low-intensity absorption bands associated with d−d transitions at around 515 (ε = 390
mol-1cm-1) nm [46]. In the case of an octahedral complex, only one such transition is
5
5
expected in the form of an intense band corresponding to T2g − Eg. It also displays
two strong absorption bands in the region 230 (ε = 1100 mol-1cm-1) and 275 nm (ε =
1150 mol-1cm-1), which can be assigned to charge transfer from the ligand to the
Mn(III) centre (LMCT).

2.4. EPR spectra
EPR spectra of the polycrystalline complex 1 were recorded at 298 and 77 K (Figure
3). The spectral intensity is very low and this is compatible with the oxidation state +3
of Mn in good agreement with the crystal structure. Indeed, EPR spectra of transition
metal ions with an even number of unpaired electrons are very difficult to obtain,
principally because the ground state spin multiplet is largely split in a zero magnetic
field by the low symmetry components of the crystal field [47]. A broad and isotropic
signal emerges only at highest instrumental gain (trace b of Figure 3), with g values
of 2.007 0.005 (298 K) and 2.005 0.005 (77 K). Such unresolved signal can be
attributed to a Mn(II) impurity in the structure of 1 and is due to the presence of a
mixture of inter-center exchange and dipolar interactions, recently discussed by
Brondino and co-workers [48]. The values of g are compatible with a distorted
octahedral environment around Mn(III), consistent with the X-ray structure of 1
[49,50].

Figure 3. X-band EPR spectra recorded at 77 K on the polycrystalline complex 1. In
trace b the signal was amplified by ten times using a highest instrumental gain.
EPR spectra in solution were also recorded; complex 1 was dissolved in both
non-coordinating and coordinating solvents: DMF (Figure 4, trace a), DMSO (Figure
4, trace b), MeOH (Figure 4, trace c) and a mixture CH2Cl2/toluene 60/40 v/v (Figure
4, trace d). The results are very similar to those obtained in the solid state and the
intensity of the spectra is very low. Very week isotropic signals centered around g ∼ 2
are detected in all the solvents and the measured g value is 2.010 0.005 in DMF,
2.009 0.005 in DMSO, 2.013 0.005 in MeOH and 2.013 0.005 in the mixture
CH2Cl2/toluene 60/40 v/v. In this case too, these signals can be attributed to the
impurities represented by Mn(II). The absence of hyperfine coupling interaction,
usually observed for Mn(II) in

Figure 4. X-band EPR spectra of the complex 1 dissolved in: (a) DMF; (b) DMSO; (c)
MeOH) and (d) a mixture CH2Cl2/toluene 60/40 v/v.
solution, could suggest that the structure of the complex remains unchanged in an
organic solvent, in contrast with other polynuclear metal complexes such as those
formed by Cu(II) [51-58].
2.5. Magnetic property
The magnetic properties of compound 1 were studied by variable temperature
magnetic susceptibility measurements in the temperature range of 2–300 K in an
applied field of 1000 Oe on a powdered microcrystalline sample. The

room-temperature µeff value is around 4.90µB per MnIII ion, which is in good
agreement with the expected value for one isolated spin-only MnIII ion (4.90µB for g =
2, S = 2). The magnetic behavior of compound 1 is depicted in the form χMT versus T
plot (Figure 5).
Figure 5. Plot of χMT vs. T for a microcrystalline sample of 1 in 0.1 T.
The temperature dependent χMT data were simulated satisfactorily showing the
parameter set of J = -0.602 cm-1 with g = 2.043. For compound 1 no satisfactory
simulation of the experimental data was possible neglecting any exchange interaction
J and taking into account only zero field splitting parameters. The small negative J
value is indicative of very weakly antiferromagnetic interactions between the MnIII
spin centers [59,60]. Furthermore, comparatively long Mn...Mn distance (5.535 Å in 1)
supports that the super exchange does not arise via direct metal–metal exchange [61].

2.6. Redox study
The cyclic voltammetry (CV) experiment was performed using three electrode
configurations. The working electrode was a glassy carbon; Pt and Ag wires served as
counter and reference electrodes, respectively. Figure 6 illustrates a typical cyclic
voltammogram of 1 mM solution of a complex, in dry acetonitrile using 0.1 M
tetra-n-butylammonium hexafluorophosphate [n-Bu4NPF6] as supporting electrolyte.
The solution was purged by passing a stream of nitrogen gas in the solution for about
10 min, before the measurement. The voltammogram is run between the potentials of
+ 1.5 and -1.6 V vs. Ag at a scan rate of 100 m V/s. Although the complex was
examined not to be electroactive in the high positive (> +1.3 V vs Ag) and negative (<
-0.5 V vs Ag) potentials; it undergo redox processes in potential region between +1.2
and-0.2 V vs Ag. A reversible redox couple at -0.14 V vs Ag is assigned for
Mn3+/Mn2+ redox process. A weak irreversible oxidation peaks were also observed at
+0.7 V and -1.2 V vs Ag. These oxidation peaks could be due to ligand based redox
processes.62 Moreover, weak reversible peak at +1.02 V vs Ag is assigned to be to
oxidation of Mn(III) to Mn(IV). The high cathodic and anodic potential difference
(about 275 mV) could be due to effect of the complex diffusion rate or an activation
barrier from electron transfer process.

60
40
20
0
-20
-40
-60
1.50
0.75
0.00 -0.75 -1.50
Potential (V vs Ag)
Figure 6. Cyclic voltammetry of 1 mM of complex in 0.1 M Bu4NPF6/acetonitrile
solution at scan rate of 0.1 V s-1 using glassy carbon as working electrode, pt-wire as
counter electrode and Ag as reference electrode at room temperature. Epc –cathodic
potential and Epa –anodic potential.
2.7. Anti-mycobacterial activity
In the anti-mycobacterial assay, H2L and complex 1 were tested against M.
tuberculosis H37Rv ATCC 27294 and M. tuberculosis H37Ra ATCC 25177 strains as
well as against two clinical strains (strain 1 and strain 2). The results are shown in
Table 2. M. tuberculosis H37Rv and M. tuberculosis H37R, well-known indicators,

were used for the drug sensitivity tests. The results showed that both the ligand H2L
and complex 1 both exhibited anti-mycobacterial activity against all the tested M.
tuberculosis strains, with MICs of 51.38 µmol/L and MBC values in the range of
51.38-398.71 µmol/L. Both H2L and complex 1 showed a bactericidal activity and
killed the bacteria (Table 2). Trias et al, [63] showed that Mycobacterium cheionae
developed a pore-forming protein as a mycobacterial porin. On the study of
permeability of Mycobacterium smegmatis, Trias & Benz [64] reported that
mycobacterial porin formed an important hydrophilic structure where small molecules
pass through the pores and diffuse into the cell. In this study, we have evidenced that
all compounds show a considerable efficacy on the Mycobacteria strains. The
mycobacteria cell wall includes a large amount of complex lipids, lipopolysaccharides
and mycolic acids. This constitution makes the cell wall a hydrophobic strong barrier
against antimicrobial agents [65,66]. The MIC
Table 2. Antimycobacterial activity (MIC and MBC, µg/ml) of H2L and 1.
Compounds The minimal inhibitory
concentration (MIC)
The minimal bactericidal
concentration (MBC)
M. tuberculosis M. tuberculosis Clinical isolate
RA RV
MIC MIC
51.38 205.59 51.38
Clinical isolate
1
2
MBC
MBC
MIC
MBC
MIC
MBC
205.59 51.38
107.78 51.38
398.71
H2L

51.38 107.78 51.38
51.38
51.38
51.38
51.38
107.78
1
Concentrations of antimycobacterial drugs (µmol/L )
Streptomysin
4.30
8.53
4.30
4.30
2.59
3.37
34.29
6.81
4.30
3.37
-
İzoniazid
3.37
6.81
0.86
6.81
3.37
(Minimal Inhibitory Concentration) and MBC (Minimal Bactericidal Concentration)
values are higher in the present case. These data are quite good when compared with
known drugs like streptomisin and isoniazid.
2.8. Cell cytotoxicity studies
Figures 7, 8 and 9 show the effects of complex 1 on cell population growth in three
human cancer cell lines, human colon carcinoma cells (Caco 2), human breast
carcinoma cells (MCF7 cells) and human lung carcinoma cells (A549 cells). To assess
the inhibitory effect on the growth of human cancer cells, the cells were cultured for
24 and 48 h with or without the test compound (0-100 µM), and the population
growth was determined by MTT assay. In particular, complex 1 shows significant
cytotoxic effect on the A549 cell line (Figure 9); additionally, 1 also exhibits good
cytotoxic activity against MCF7 cancer cell lines (Figure 8). When this result is
compared with the control group, it can be seen that a time-dependent decrease on
mitochondrial activity for all concentrations occurs. The manganese complex shows a

cytotoxic effect which induces DNA hypermetilation and oxidative stress on the
cancer cell lines. Moreover, the 50% inhibitory concentration (IC50) as determined by
MTT assay after 48 h of incubation shows the highest activity with an IC50 value of
46.00 1.09 µM.
Figure 7. Cytotoxic effects of complex 1 on CACO2 cell line.
Figure 8. Cytotoxic effects of complex 1 on MCF7 cell line.

Figure 9. Cytotoxic effects of complex 1 on A549 cell line.
3. Experimental section
3.1. Materials
All chemicals and solvents used for the synthesis were of reagent grade, obtained
commercially and used as received. Salicyldehyde and ethylenediamine were
purchased from Aldrich Chemicals. Hydrated manganese(II) trichloroacetate was
prepared by the treatment of basic manganese(II) carbonate, MnCO3.Mn(OH)2 (AR
grade, E. Merck), with 60% trichloroacetic acid (AR grade, E. Merck), followed by
slow evaporation on a steam bath. It was then filtered through a fine glass frit and
stored in a CaCl2 desiccators.
3.2. Physical techniques
Microanalytical data (C, H, and N) were collected on a Perkin–Elmer 2400 CHNS/O

elemental analyzer. FTIR spectra were recorded on a Perkin-Elmer RX-1
spectrophotometer in the range 4000–400 cm-1 as KBr pellets. Electronic spectra were
measured on a Lambda 25 (U.V.–Vis.–N.I.R.) spectrophotometer. EPR spectra were
recorded from 0 to 8000 Gauss in the temperature range 77-298 K with an X-band
(9.4 GHz) Bruker EMX spectrometer equipped with an HP 53150A microwave
frequency counter. Magnetic properties were investigated with a Quantum Design
MPMS-XL superconducting quantum interference device magnetometer (SQUID) at
an applied field 0.5 T in a temperature range 5-300 K. The diamagnetic correction was
carried out by using Pascal constants.
3.3. Synthesis of {[C6H4(O)CHN(CH2)2NCH(O)C6H4]Mn(N3)}n (1)
To a methanol solution (10 mL) of Mn(CCl3COO)2.4H2O (0.716 g, 2 mmol), the
ligand H2L [43] (2 mmol) in 15 mL of methanol was added with under constant
stirring. The resulting green solution was kept boiling for 10 mins. After that an
aqueous solution (10 mL) of anhydrous NaN3 (0.195 g, 3 mmol) was added slowly in
warm condition and the mixture was kept undisturbed at room temperature.
Dark-brown square-shaped single crystals of 1 were generated after one week. These
were separated over filtration and air-dried before X-ray diffraction analysis. Yield:
0.58 g. Anal. Calc. for C16H14MnN5O2: C, 52.86; H, 3.88; N, 19.27. Found: C, 52.59;

H, 4.12; N, 19.41%.
3.4. X-ray crystallography
The crystal structure of compound 1 was determined by X-ray diffraction methods.
Intensity data and cell parameters were recorded at 190(2) K on a Bruker APEX II
equipped with a CCD area detector and a graphite monochromator (MoKα radiation λ
= 0.71069 Å) The raw frame data were processed using SAINT and SADABS to yield
the reflection data file [67]. The structure was solved by Direct Methods using the
2
SIR97 program [68] and refined on Fo by full-matrix least-squares procedures, using
the SHELXL-2014/7 program [69] in the WinGX suite v.2014.1 [70]. All
non-hydrogen atoms were refined with anisotropic atomic displacements. The
hydrogen atoms were included in the refinement at idealized geometry (C-H 0.95 Å)
and refined “riding” on the corresponding parent atoms. The weighting scheme used
2
2
in the last cycle of refinement was w = 1/ [σ2Fo + (0.0523P)2], where P = (Fo +
2Fc2)/3. Geometric calculations were performed with the PARST97 program [71].
Crystal data and experimental details for data collection and structure refinement are
reported in Table 3. Crystallographic data for the structures reported have been
deposited with the Cambridge Crystallographic Data Centre as supplementary
publication no. CCDC-1501177 and can be obtained free of charge on application to

the CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK (fax: +44-1223-336-033;
e-mail deposit@ccdc.cam.ac.uk or http://www.ccdc.cam.ac.uk).
Table 3. Crystal data and structure refinement information for 1.
Compound
1
empirical formula
C16H14N5O2Mn
363.26
M
crys syst
Orthorhombic
Pca21
space group
a/Å
10.881(3)
11.070(3
12.943(3)
1559.0(7)
4
b/Å
c/Å
V/Å3
Z
T/K
190(2)
ρ /g cm–3
1.548
µ /mm–1
0.866
F(000)
744
total reflections
unique reflections (Rint)
12235
2861 (0.0866)
observed reflections [Fo>4σ(Fo)] 2055
GOF on F2a
1.010
R indices [Fo>4σ(Fo)]bR1, wR2
0.0464, 0.0977
largest diff. peak and hole (eÅ–3) 0.519, -0.374
2
2 2
aGoodness-of-fit S = [Σw(Fo -Fc ) / (n-p)]1/2, where n is the number of reflections

and p the number of parameters. bR1 = Σ║Fo│-│Fc║/Σ│Fo│, wR2 =
2
2 2
[Σ[w(Fo -Fc2)2]/Σ[w(Fo ) ]]1/2.
3.5. Anti-mycobacterial activity
3.5.1. Medium
In the assays, Mycobacteria Growth Indicator Tubes (MGIT) and their supplements,
BBL MGIT OADC enrichment and BBL MGIT PANTA were purchased from BD.
The MGIT Mycobacteria Growth Indicator Tube contains 4 mL of modified
Middlebrook 7H9 Broth base.
3.5.2. Inoculum preparation
For the cultivation of mycobacteria, the MGIT (Mycobacteria Growth Indicator Tube),
a fluorescent compound is embedded in silicone on the bottom, then 4 mL of modified
Middle brook 7H9 Broth base are added to the mixture. After that 0.5 mL of OADC
enrichment, (an oleic acid, albumin, dextrose and catalase) and PANTA antibiotic
mixture to prevent the growth of any non-mycobacteria (0.1 mL) are added to this
medium. Oleic acid plays an important role in metabolism of mycobacteria; Albumin
acts as a protective agent; Dextrose is an energy source; Catalase destroys toxic
peroxides. Tubes are incubated at 37 °C. For positive control, MGIT tubes are
prepared by inoculating bacteria. An un-inoculated MGIT tube is used as a negative

control. Blood Agar is used for checking the growth of other bacteria. Daily tube
reading starts on the second day of incubation using a Micro MGIT fluorescence
reader which has a long wave UV light [72]. To prepare inoculums from a positive
BACTEC MGIT tube, the positive tubes (day 1 or day 2 positive) are used directly as
inoculums. The positive tubes between day 3 and day 5 are diluted to 1:4 ratio by
sterile saline. Inoculums, prepared from a Day 1 to Day 5 MGIT 7 mL positive tube,
range between 0.8 × 105 and 3.2 × 105 CFU/mL. Each assay is performed according
to the MGIT manual fluorometric susceptibility test procedure recommended by the
manufacturer [72,73].
3.5.3. Antimycobacterial susceptibility assay
The activity of the ligand, H2L and complex 1 against M. tuberculosis strains was
tested using the Microplate Presto Blue Assay (MPBA) by the method described by
Collins & Franzblau [74] and modified by Jimenez-Arellanes et al. [75] 128 µl of
compound 1 and 72 µl of 7H9 broth were transferred in the first column; then 100 µl
of 7H9 broth was transferred from column 2 to column 8. Column 9 and 10 were the
positive and negative control, respectively. 100 µl of a mixture of broth and of
compound 1 were transferred from column 1 to column 2, then mixed by pipettes
three times; the procedure was repeated to provide serial 1:2 dilutions. 100 µl of the

excess medium was discarded from the wells in column 8. Afterwards, 20 µl of M.
tuberculosis inoculum was added to the wells of column 1 to 8 and to the positive
control columns. Negative control columns were not inoculated with bacteria. Positive
control columns included 7H9 broth and bacteria, while negative control columns
contained 7H9 broth and compound 1. Final-test concentration ranges were
423.68-6.62 µmol/L in the mixture. Microplates were inoculated with the bacterial
suspension (20 µL per well) except for the negative control and incubated at 37 °C for
6 days. Presto blue (15 µL, Life Technologies) was then added to the bacterial growth
control wells (without compound 1) and the microplates were incubated at 37 °C for
an additional 24 h. If the dye turned from blue to pink (indicating positive bacterial
growth), the Presto blue solution was added to the other wells to determine the MIC
values. All tests were performed in triplicate. The minimal inhibitory concentration
(MIC) was defined as the lowest concentration of sample that prevents a color change
to pink. The minimal bactericidal concentration (MBC) corresponded to the minimum
compound concentration which does not cause a color change in the cultures when
re-incubated in fresh medium [76,77]. Streptomycin (STR) from Sigma, and isoniazid
(INH) from Fluka were used as standard drugs.
3.6. Cell cytotoxicity

3.6.1.
Cell culture
A549 (non-small cell lung cancer), MCF-7 (breast cancer) and Caco-2 (colon cancer
cell line) were used in the study, provided by ATCC cell bank. The cells were grown
in RPMI 1640 medium supplemented with 2 mM L-glutamine and 10% fetal bovine
serum, 1% penicillin-streptomycin at a temperature of 37 oC in a humidified incubator
with a 5% CO2 atmosphere.
3.6.2.
MTT assay
Complexes 1 and 2 having the concentration of 1500, 250, 125, 62.5, 31.25, 15.625,
7.812, 3.9, 1.95, 0.97 µg/ml were seeded in 5 × 103 cells which were cultivated in
each well of a 96-well plate. After 24 hours of incubation, 0.1 mL of WST-1 working
solution was added to each well and they were incubated at 37 °C in a 5 % CO2
incubator for 3-4 hours. The absorbance intensity of the living cell in the plate was
read in an ELISA device (Cytation3, Biotek, USA) at 450 nm. The acquired
absorbance values corresponded to the metabolic activities of the cells in the culture.
Because this value was correlated to the number of living cells, the results were
expressed in liveliness percent and calculated using the formula below.
100
ꢀꢁꢂꢃꢄꢁꢅꢃꢆꢆꢇꢈꢃꢉꢊꢃꢅꢋ =
ꢌꢍꢆꢎꢉꢍꢏꢅꢊꢃꢇꢎꢐꢇꢋℎꢃꢇꢊꢎꢅꢋꢉꢎꢄ
ꢒ
ꢌꢍꢆꢎꢉꢍꢏꢅꢊꢃꢇꢎꢐꢇꢋℎꢃꢇꢆꢏꢑꢈꢄꢃꢇ

4. Conclusion
A new Schiff base assisted, Mn(III) one-dimensional network was generated and
spectroscopically characterized. The solid state structure of 1 shows that the Mn
atoms in the polymer present a distorted octahedral arrangement. Solvent-mediated
EPR spectra is carried out and found to remain unchanged while varying from
coordinating to non-coordinating organic solvents. The temperature dependent
magnetic moment supports the presence of weak antiferromagnetic interactions
between the bridging Mn(III) ions. Both the ligand H2L and complex 1 exhibit
anti-mycobacterial activity and considerable efficacy on M. tuberculosis H37Rv
ATCC 27294 and M. tuberculosis H37Ra ATCC 25177 strains. Further investigations
in this area with other transition metal ions and chemo-sensor activities of the ligand
for selective detection of metal ions are currently being carried out in our laboratories.
Appendix A. Supplementary data
CCDC 1501177contains the supplementary crystallographic data for complex 1.
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: (+44)
1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk.

Acknowledgements
KD and CS would like to thank DST (Department of Science and Technology, New
Delhi, India) for the grant (SR/S1/IC-31/2008) to carry out the present study.
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