Synthesis, structure and antibacterial activity of manganese(III) complexes of a Schiff base derived from furfurylamine

Article abstract of DOI:10.1016/j.poly.2009.08.034

Two new mononuclear complexes of manganese(III) viz. [MnL₂(LH)₂]ClO₄ (1) and [MnL₂(N₃)]·0.5CH₃OH (2) have been synthesized by reacting manganese perchlorate with furfurylamine and salicylal

Full text of DOI:10.1016/j.poly.2009.08.034

Polyhedron 28 (2009) 3858–3862
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Synthesis, structure and antibacterial activity of manganese(III) complexes
of a Schiff base derived from furfurylamine
Santanu Mandal a, Ashok Kumar Rout b, Anupam Ghosh c, Guillaume Pilet d, Debasis Bandyopadhyay a,
*
a Department of Chemistry, Bankura Christian College, Bankura, West Bengal, India
b Department of Chemistry, Kalinga Institute of Industrial Technology, Bhubaneswar, Orissa, India
c Department of Zoology, Bankura Christian College, Bankura, West Bengal, India
d Laboratoire des Multi-matériaux et Interfaces, Groupe de Cristallographie et Ingénierie Moléculaire, UMR 5615 CNRS, Université Claude Bernard Lyon 1,
Campus de la Doua, Bâtiment Raulin (rdc), France
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 3 July 2009
Accepted 24 August 2009
Available online 15 September 2009
Two new mononuclear complexes of manganese(III) viz. [MnL2(LH)2]ClO4 (1) and [MnL2(N3)]Á0.5CH3OH
(2) have been synthesized by reacting manganese perchlorate with furfurylamine and salicylaldehyde
(plus sodium azide in 2) where L = (2-hydroxybenzyl-2-furylmethyl)imine, an asymmetric bidentate
Schiff base formed in situ to bind the Mn(III) ion. The complexes have been characterized by elemental
analysis, IR spectroscopy, TGA and single crystal X-ray diffraction studies. Structural studies reveal that
the complexes 1 and 2 adopt an octahedral and a square pyramidal geometry, respectively. The antibac-
terial activity of the complexes has been tested against Gram(+) and Gram(À) bacteria.
Ó 2009 Elsevier Ltd. All rights reserved.
Keywords:
Manganese(III)
Furfurylamine
Crystal structure
Square pyramidal geometry
Antibacterial activity
1. Introduction
We describe here the synthesis of two new mononuclear com-
plexes of manganese(III) containing a Schiff base ligand (HL) ob-
Coordination chemistry of manganese in various oxidation
states has long been investigated as an area of considerable inter-
est in inorganic biochemistry [1]. A large number of Schiff base
complexes of manganese(III) find important roles in metalloen-
zymes, redox and non-redox proteins [2,3]. They possess suitable
biometric properties that can mimic the structural features of the
active site [4–6]. In recent years, there has been enhanced interest
in the synthesis and characterization of such complexes not only
due to their biological importance, but also for their interesting
catalytic [7] and magnetic properties [8]. Schiff bases derived from
salicylaldehyde and various amines have been extensively used to
synthesize many complexes of manganese(III). However, com-
plexes with furfurylamine as the amine counterpart of the Schiff
base have received very scanty attention. A report on the prepara-
tion and characterization of such complexes of Cu(II), Ni(II) and
Co(II) has only appeared very recently [9]. However, report on syn-
thesis of complexes of manganese(III) by preparation of the Schiff
base in situ or along with any pseudohalide is lacking. Again, the
investigation of biological properties of Schiff base complexes of
Mn(III) have received less attention in comparison to the corre-
sponding Mn(II) complexes. A few reports on the antimicrobial
activity of Mn(III) complexes have been reported recently [10–12].
tained in situ from furfurylamine and salicylaldehyde. The
complexes have been characterized by microanalytical, spectro-
scopic, thermogravimetric and single crystal X-ray structural stud-
ies and tested in vitro to assess their antibacterial activities against
some common reference bacteria and compared with commercial
antibiotic biodiscs of Nalidixic acid and Gattifloxacin.
OH
N
O
HL
2. Experimental
2.1. Physical measurements
Elemental analyses were carried out using a Perkin–Elmer 2400
elemental analyzer. The infrared spectra were recorded on a Per-
kin–Elmer FT-IR spectrophotometer with KBr discs (4000–
300 cmÀ1). Molar conductances of the complexes in dry methanol
were measured using a direct reading conductivity meter of
Systronics (Type 304). 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.
* Corresponding author. Tel./fax: +91 3242 250924.
E-mail address: dbbccchem@yahoo.co.in (D. Bandyopadhyay).
0277-5387/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2009.08.034

S. Mandal et al. / Polyhedron 28 (2009) 3858–3862
3859
Table 1
Diamagnetic corrections were taken from standard sources. Ther-
mogravimetric analyses were carried out using Netzsch
Crystallographic data and structure refinement for 1 and 2.
a
STA409PC instrument from 30 °C to 700 °C in an atmosphere of
Parameters
1
2
dinitrogen at the heating rate of 10 °C minÀ1
.
Formula
C48H42Cl1Mn1N4O12 C24.5H22Mn1N5O4.5
957.3
Formula weight (g molÀ1
Crystal system
Space group
a (Å)
)
513.4
monoclinic
P21/a
9.5848 (4)
24.1361 (6)
11.1908 (5)
90
113.433 (2)
90
2375.4 (2)
4
293
0.71073
5196 (0.052)
triclinic
2.2. Materials
ꢀ
P1
9.3469 (2)
9.6091 (3)
24.6111 (7)
83.409 (2)
89.692 (2)
78.914 (2)
2154.6 (1)
2
Reagent grade salicylaldehyde, furfurylamine, manganese(II)
perchlorate hexahydrate and sodium azide were purchased from
reputed manufacturers and used as received. All other chemicals
and solvents were of analytical grade.
Caution! Compounds containing perchlorate and azide are
potentially explosive. Therefore, only a small amount of the mate-
rials should be used at a time and handled with proper care. How-
ever, no problems were encountered during our studies including
the thermogravimetric analyses of compounds 1 and 2 within
the experimental range of temperature in inert atmosphere.
b (Å)
c (Å)
a
(°)
b (°)
c
(°)
V (Å3)
Z
T (K)
k (Mo K
150
0.71073
10218 (0.079)
a
) (Å)
Number of unique reflections
(Rint
D (g cmÀ3
(mmÀ1
)
)
1.475
0.44
4534
598
1.436
0.599
3457
325
l
)
Number of reflections used
Number of parameters refined
2.3. Synthesis of compounds
R (F), I > 3
r
r
(Fo)
(Fo)
0.045
0.0465
1.11
0.37
À0.38
0.0584
0.0679
1.12
0.40
À0.45
2.3.1. Synthesis of [MnL2(LH)2]ClO4 (1)
Rw (F), I > 3
S
A methanolic solution of manganese(II) perchlorate hexahy-
drate (0.36 g, 1.0 mmol) was added to a mixture of salicylaldehyde
(0.24 g, 2.0 mmol) and furfurylamine (0.19 g, 2.0 mmol) in metha-
nol with constant stirring and the total volume was made up to
50 ml (solution-1) by adding the same solvent. Stirring was contin-
ued for half an hour and the solution was left for slow evaporation
at room temperature in a beaker open to the atmosphere. After a
week, dark brown crystals of compound 1 appeared. The crystals
were collected by filtration, washed with methanol and finally
dried (0.26 g, 55%). Anal. Calc. for C48H42ClMnN4O12: C, 60.22; H,
4.42; N, 5.85; Mn, 5.74. Found: C, 59.98; H, 4.38; N, 5.82; Mn,
5.69%. FTIR (KBr, cmÀ1): 1644(s), 1623(s), 1599(m), 1530(w),
1485(m), 1448(m), 1419(w), 1320(m), 1290(s), 1151(m), 1094(s),
1013(w), 898(w), 835(w), 758(m), 623(w). KM (MeOH,
D
D
qmax (e ÅÀ3
)
)
qmin (e ÅÀ3
2.5. Antimicrobial activity – minimum inhibitory concentration
Complexes 1, 2 and two reference commercial antibiotics viz.
Nalidixic acid and Gattifloxacin (purchased in powder form from
Span Diagnostic Limited, Surat, India) were tested in vitro to assess
their growth inhibitory activity against two Gram positive bacteria,
viz. Staphylococcus aureus MTCC 2940 and Bacillus subtilis MTCC 441
and two gram negative bacteria viz. Pseudomonas aeruginosa MTCC
2453 and Klebsiella pneumoniae MTCC 530 by Kirby Bauer method
with necessary modifications [16]. The antibacterial activity of fur-
furylamine, salicylaldehyde and the Schiff base HL prepared [9]
from furfurylamine and salicylaldehyde were also evaluated during
the same experiment. The bacterial strains grown on nutrient agar
at 37 °C for 18 h were suspended in a saline solution (0.85% NaCl)
X
À1 cm2 molÀ1): 130. leff (RT, BM): 4.7.
2.3.2. Synthesis of [MnL2(N3)]Á0.5CH3OH (2)
To a 50 ml of solution-1 in methanol (prepared using the same
mole ratio of reactants as in Section 2.3.1. above), 0.065 g (1 mmol)
of sodium azide dissolved in minimum volume of water was
added. Stirring was continued for further half an hour. Pure dark
brown crystals of 2 were collected after two days, washed and
dried following the same procedure described in Section 2.3.1.
(0.37 g, 72%). Anal. Calc. for C24.5H22MnN5O4.5: C, 57.31; H, 4.32;
N, 13.64; Mn, 10.70. Found: C, 57.25; H, 4.27; N, 13.62; Mn,
10.68%. FTIR (KBr, cmÀ1): 2926(s), 2853(s), 2038(s), 1613(s),
1546(w), 1301(m), 1142(w), 904(w), 738(m). KM (MeOH,
and adjusted to
a turbidity of 0.5 MacFarland standards
(108 CFU mlÀ1). The suspension was used to inoculate 90 mm diam-
eter sterile Petri plates in which the test organisms were grown on
nutrient agar medium. All the compounds including the commer-
cial antibiotics were dissolved in dimethylsulphoxide (1 mg mlÀ1
)
and soaked in filter paper discs of 5 mm diameter and 1 mm thick-
ness for 12 hours at <40 °C. The discs were placed on the previously
seeded plates and incubated at 30 °C for B. subtilis and at 37 °C for
other bacteria. Antibacterial activities were evaluated by measuring
inhibition zone diameters (IZD). The experiments were repeated
thrice along with a control set using dimethylsulphoxide (dmso).
The minimum inhibitory concentrations (MIC) were also deter-
mined by serial dilution technique (from 1 mg mlÀ1 to 5 mg mlÀ1
concentrations) as followed by the National Committee for Clinical
Laboratory Standards [17]. MIC was the lowest concentration of a
compound extracted in dmso that exhibited no visual growth of
the organisms in the culture tubes.
X
À1 cm2 molÀ1): 5. leff (RT, BM): 4.8.
2.4. Crystal structure determination and refinement
Single crystal X-ray studies of 1 and 2 were carried out in a Nonius
Kappa CCD diffractometer using the related analysis software [13].
No absorption corrections were made to the data sets. All structures
were solved by direct methods using the SIR97 program [14] com-
bined with Fourier difference syntheses and refined against F using
reflections with [I/r(I) > 3] utilizing the CRYSTALS program [15]. All
3. Results and discussion
atomic displacement parameters for non-hydrogen atoms have
been refined with anisotropic terms. The hydrogen atoms were the-
oretically located on the basis of the conformation of the supporting
atom or found by Fourier difference. Complex 2 crystallizes appar-
ently with one methanol molecule which shows positional disorder
with 50% occupancies. Crystallographic data and refinement details
for the compounds are summarized in Table 1.
3.1. Synthesis
The mononuclear Mn(III) complexes 1 and 2 have been prepared
by adding salicylaldehyde and furfurylamine directly to the reac-
tion mixture and the bidentate Schiff base HL was formed in situ
in both the cases. Thus the pre-condensation to form the Schiff base

3860
S. Mandal et al. / Polyhedron 28 (2009) 3858–3862
Fig. 1. Molecular structure of 1 with atom labeling. (a) and (b) represent the two independent mononuclear units of Mn2 and Mn1, respectively.
ligand has been avoided and no HL was needed to be isolated. Addi-
tion of azide to the reaction mixture of 1 yielded the mixed ligand
azido complex 2 with a completely different geometry. The com-
plexes have been characterized by elemental analysis, IR spectros-
copy, electrical conductivity and magnetic susceptibility
measurements as well as by thermogravimetric and single crystal
X- ray structural analysis. The results are consistent with the mono-
nuclear formulae. In methanol solution, 1 behaves as a 1:1 electro-
lyte while 2 behaves as a non-electrolyte as is evident from their
250°–360 °C, corresponding to the removal of one ligand followed
by gradual weight loss up to 700°C. In compound 2, the first stage
of weight loss (ꢀ3.12%) occurs between 60 °C and 70 °C corre-
sponding to the loss of the methanol molecule present in the crys-
Table 2
Selected bond lengths (Å) and bond angles (°) of 1.
Mn1–N126
Mn2–N206
Mn1–O114
2.048(3)
2.068(3)
2.150(3)
Mn1–O134
Mn2–O214
Mn2–O234
1.882(3)
1.875(2)
2.151(3)
KM values (ca. 130 and 5
X
À1 cm2 molÀ1, respectively). Room tem-
perature magnetic susceptibility measurements indicate that the
complexes have magnetic moments (4.7–4.8 B.M.) close to the
spin-only value of Mn(III) as expected from discrete and magneti-
cally non-coupled mononuclear d4 ions. Mn(II) has undergone aer-
ial oxidation to Mn(III) in both the reactions as was observed earlier
by our research group and others [18,19] in similar syntheses. This
is probably due to the formation of more stable complexes by hard-
er MnIII ion with ligands containing harder donor atoms. As usual,
the furyl group is not coordinated to Mn(III) ion and our attempt
to synthesize complexes with tridentate Schiff base of furfuryl-
amine remained unsuccessful.
O114–Mn1–N126
N126–Mn1–O134
N126–Mn1–O114
O114–Mn1–N126
O134–Mn1–N126
O114–Mn1–O134
O134–Mn1–O134
N206–Mn2–O214
O234–Mn2–O234
N206–Mn2–O234
89.5(1)
89.9(1)
90.5(1)
90.5(1)
90.1(1)
95.1(1)
180
90.0(1)
180
89.4(1)
O114–Mn1–O134
O114–Mn1–O114
O134–Mn1–O114
N126–Mn1–N126
O114–Mn1–N126
N126–Mn1–O134
O114–Mn1–O134
O214–Mn2–O214
N206–Mn2–O234
O214–Mn2–O234
84.9(1)
180
95.1(1)
180
89.5(1)
90.1(1)
84.9(1)
180
90.6(1)
84.2(1)
3.2. FTIR spectra
The infrared spectra of the compounds 1 and 2 are similar in
some respects as expected. They show strong bands at 1613–
1623 cmÀ1 which are assignable to the C@N stretching vibrations
[mCN] indicating the formation of the Schiff base products. However,
the spectrum of compound 2 exhibits a very strong and sharp
absorption band at 2038 cmÀ1 corresponding to the asymmetric
stretching vibrations of the terminal azide ion [mas(N3)]. The asym-
metric single and sharp band expected for ClO4- is also observed at
1094 cmÀ1 in compound 1. All other characteristic vibrations
including the phenolic C–O stretching of the metal-bound Schiff
bases are located in the range 600–1600 cmÀ1. Thus the IR spectra
of the compounds are in good agreement [20] with the respective
structural features of Mn(III) Schiff base complexes.
3.3. Thermogravimetric analysis
The thermograms of TGA reveal that the compound 1 is stable
up to 160 °C and first stage of weight loss (ꢀ21%) occurs between
Fig. 2. Molecular structure of 2 with atom labeling.

S. Mandal et al. / Polyhedron 28 (2009) 3858–3862
3861
Table 3
Selected bond lengths (Å) and bond angles (°) of 2.
Mn1–O1
Mn1–N29
1.861(2)
2.053(2)
Mn1–N9
Mn1–N41
2.049(2)
2.100(3)
Mn1–O21
1.850(2)
O1–Mn1–N9
O1–Mn1–N29
O1–Mn1–N41
N29–Mn1–N41
89.9(1)
89.3(1)
94.7(1)
95.9(1)
O1–Mn1–O21
N9–Mn1–N29
N9–Mn1–N41
168.4(1)
162.0(1)
102.1(1)
N9–Mn1–O21
O21- Mn1–N29
O21–Mn1–N41
87.9(1)
89.2(1)
96.9(1)
tal lattice. This is followed by a steep weight loss up to 320 °C, after
which it again decreases gradually up to the maximum tempera-
ture of study.
Table 5
Minimum inhibitory concentrations (mg mlÀ1) of 1, 2 and related compounds.
Compounds
S. aureus
B. subtilis
P. aeruginosa
K. pneumoniae
1
2
<2
>5
>5
>5
>5
<1
<1
>5
<2
>5
>5
>5
<1
<1
<1.5
>5
>5
>5
>5
<2
<2
>5
>5
>5
<1
<1
3.4. Crystal structure of the compounds
Furfurylamine
Salicylaldehyde
HL
Nalidixic acid
Gattifloxacin
3.4.1. Crystal structure of 1
The molecular structure of 1 is shown in Fig. 1 and a few se-
lected bond distances and angles are listed in Table 2. The X-ray
structure reveals that the compound 1 is built up of two indepen-
dent mononuclear units (Fig. 1a and b with Mn2 and Mn1, respec-
tively as the central metal ions) in the solid state. These two
molecules are structurally identical except for a slight variation
in bond angles and lengths.
In both the units, the Mn(III) ion adopts a distorted octahedral
geometry in which the equatorial plane is formed by the coordina-
tion of the bidentate Schiff base ligand i.e., two imino nitrogen
(N126 for Mn1 and N206 for Mn2) and two phenolic oxygen atoms
(O134 for Mn1 and O214 for Mn2). The apical positions are occu-
pied by two phenolic oxygen atoms (O114 and O234 for Mn1
and Mn2, respectively) of N-protonated Schiff base molecules, each
acting as a monodentate ligand. All the axial bonds are slightly
longer than the equatorial ones as a result of Jahn-Teller distortion
occurred in octahedral Mn(III) complexes which is evident from
the average Mn–O, –N and Mn–O bond lengths of 1.968 and
2.150 Å, respectively in the equatorial and the apical positions.
The electroneutrality is maintained by the presence of the perchlo-
rate anions.
<1
<1
is due to the asymmetric nature of the bidentate Schiff base ligand.
However, the distortion is much less as evidenced from the cisoid
and transoid angles, all being closer to 90° and 180°, respectively.
The observed bond angles indicate that the Mn(III) ion is slightly
above the square base.
3.5. Antibacterial activity
The antibacterial activity of all of the tested compounds and
their MIC values are presented in Tables 4 and 5, respectively.
The results of the antibacterial screening indicate that although
furfurylamine, salicylaldehyde and the corresponding Schiff base
lack any bacterial growth retardation activity, the complexes 1
and 2 exhibit antibacterial activity to some extent. However, both
the complexes possess rather higher MIC and lower IZD values. The
IZD data shows that compound 1 is active against S. aureus but is
inactive against B. subtilis whether the reverse is seen in compound
2. Again, complex 1 shows activity against both the Gram(À) bac-
teria, but 2 is active only against K. pneumoniae. Thus the antibac-
terial study reveals that K. pneumoniae is susceptible against both
the compounds and the MIC values of the two are of the same or-
der. However, the antibacterial activities of both 1 and 2 are much
lower than the tested commercial antibiotics at similar
concentrations.
3.4.2. Crystal structure of 2
The molecular structure of 2 is displayed in Fig. 2. and a few se-
lected bond dimensions are collected in Table 3. The coordination
geometry around the Mn(III) ion is a distorted square pyramid. The
two imino nitrogen (N9, N29) and two phenolic O-atoms (O1, O21)
are located in the trans positions to form the square base.
As expected, the Mn–N bond distances are greater than the Mn–
O bonds in the basal plane. The apical position is occupied by one
N-atom of the azide ion with a Mn(1)–N(41) bond length of
2.100(3) Å. Distortion from an ideal square pyramidal geometry
4. Conclusion
Two new mononuclear Mn(III) complexes could be synthesized
with a less familiar asymmetric bidentate Schiff base ligand ob-
tained in situ from the respective aldehyde and amine. Both the
complexes possess rather unusual ligand coordination and geome-
try. The results of antibacterial screening of the compounds indi-
cate mild bactericidal activities. In addition to the synthetic and
structural investigations, this study helps to evaluate the potential-
ity and effectiveness of newer Schiff base complexes of Mn(III) to
use as antibacterial agents.
Table 4
Antibacterial activities of 1, 2 and related compounds compared to control (dmso)
and standard antibiotics (concentration = 1 mg mlÀ1 and n = 3 trials/compound).
Compounds
Inhibition zone diameter (mean standard error)
Gram positive bacteria
Gram negative bacteria
S. aureus
B. subtilis
P. aeruginosa K. pneumoniae
1
13.66 0.33
15 1.00
13.00 1.00
2
12.66 0.88
14.66 0.88
Furfurylamine
Salicylaldehyde
HLa
Supplementary data
dmso
Nalidixic acid
Gattifloxacin
CCDC 714205 and 714206 contains the supplementary crystal-
lographic data for 1 and 2. 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,
26.66 1.33 28.33 1.66 22.66 1.20
31.33 0.76 32.66 1.00 29.33 1.20
29.33 0.88
30.66 1.00
a
Schiff base of furfurylamine and salicylaldehyde [9].

3862
S. Mandal et al. / Polyhedron 28 (2009) 3858–3862
[6] J. Reedijk, E. Bouwman, Bioinorganic Catalysis, Marcel Dekker Inc., New York,
1999.
[7] E.M. McGarrigle, D.G. Gilheany, Chem. Rev. 105 (5) (2005) 1563.
[8] Reviews: O. Kahn, Molecular Magnetism, VCH, Weinheim, Germany, 1993.
[9] Y. Song, Z. Xu, Q. Sun, B. Su, Q. Gao, H. Liu, J. Zhao, J. Coord. Chem. 61 (2008)
1212.
Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail:
deposit@ccdc.cam.ac.uk.
Acknowledgements
[10] I. Sakiyan, E. Logoglu, S. Arslan, N. Sari, N. Sakiyan, BioMetals 17 (2004) 115.
[11] C.D. Samara, A.N. Papadopoulos, D.A. Malamatari, A. Tarushi, C.P. Raptopoulou,
A. Terzis, E. Samaras, D.P. Kessissoglou, J. Inorg. Biochem. 99 (2005) 864.
[12] M. Balakrishnan, M. Kochukittan, J. Enzyme Inhib. Med. Chem. 22 (2007) 65.
This work was financially supported by Star Consultancy Ser-
vices Pvt. Ltd., Bhubaneswar, Orissa, India. Our thanks are extended
to Rt. Revd. Dr. P. K. Dutta (Chairman of Governing Body), Dr. R. N.
Bajpai (Principal) and Dr. S. K. Roy (Head, Chemistry Department)
of Bankura Christian College for their constant encouragement
and valuable suggestions in doing the work. We also thank Mr.
Kalyan Dana for his assistance.
[13] Nonius, Kappa CCD Program Package: COLLECT
Delft, The Netherlands, 1999.
, DENZO, SCALEPACK, SORTAV, Nonius BV,
[14] A. Altomare, M.C. Burla, M. Camalli, G.L. Cascarano, C. Giacovazzo, A.
Guagliardi, A.G.G. Moliterni, G. Polidori, R. Spagna, J. Appl. Crystallogr. 32
(1999) 115.
[15] D.J. Watkin, C.K. Prout, J.R. Carruthers, P.W. Betteridge, CRYSTALS 11, Chemical
Crystallography Laboratory, Oxford, UK, 1999.
[16] A.W. Bauer, W.M. Kirby, J.C. Sheris, M. Turck, Am. J. Clin. Pathol. 45 (1966) 149.
[17] National Committee for Clinical Laboratory Standards, Performance Standards
for Antimicrobial Disc Susceptibility Tests, Approved Standard NCCLS
Publications, M2-A5, Villanova, 1993.
[18] S. Mandal, G. Rosair, J. Ribas, D. Bandyopadhyay, Inorg. Chim. Acta 362 (2009)
2200.
[19] Z. Lu, M. Yuan, F. Pan, S. Gao, D. Zhang, D. Zhu, Inorg. Chem. 45 (2006) 3538.
[20] K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordination
Compounds, fourth ed., Wiley Interscience, New York, 1986.
References
[1] V.L. Pecoraro, W.-Y. Hsieh, in: A. Sigel, H. Sigel (Eds.), Metal Ions in Biological
Systems: Manganese and its Role in Biological Processes, vol. 37, Marcel
Dekker, New York, 2000, p. 431.
[2] J.J.R. Fraústo da Silva, R.J.P. Williams, The Biological Chemistry of the Elements,
Oxford University Press, 2001.
[3] V.L. Pecoraro (Ed.), Manganese Redox Enzymes, VCH, New York, 1992.
[4] H.-L. Shyu, H.-H. Wei, Y. Wang, Inorg. Chim. Acta 290 (1999) 8.
[5] Y. Cringh, S.W. Gordon-Wylie, R.E. Norman, G.R. Clark, S.T. Weintraub, C.P.
Horwitz, Inorg. Chem. 36 (1997) 4968.