Synthesis, characterization and combined superoxide dismutase and catalase activities of manganese complexes of l,4-Bis(salicylidenamino)butan-2-ol

Article abstract of DOI:10.1002/ejic.200901018

Two Mn^IV complexes of general formula [Mn(salbutO)X] [H ₃salbutO = l,4-bis(salicylidenamino)butan-2-ol, 1; X = N₃, 2: X = SCN] have been prepared and structurally characterized. The crystal structure of 1 shows that salbutO^3- acts as a pentadentate ligand through the two phenolato-O, two imino-N, and one alcoholato-O atoms, and the sixth coordination position, is occupied by the azido-N atom, resulting in a slightly distorted N³O³ donor set: around the Mn ^IV ion. ESIMS, UV/Vis, and. ¹H NMR spectroscopy were used, for solution studies. In methanol and dmf, the starting complexes are converted into [Mn^III(salbutO)] and its dimeric form. The E₁/ ₂ of Mn^III/Mn^Iv (ca. 0.4 V vs. Ag/AgCl) allows this couple to efficiently catalyze the dismutation of O₂-with catalytic rate constant and IC₅₀ values of 1.91X10⁶M- ¹S-^a and 1.43 μM, respectively, which were obtained, through the nitro blue tetrazolium photoreduction inhibition SOD assay, in aqueous solution of pH 7.8. The Mn-salbutO complexes also show catalase activity in methanol and dmf, with k_cat =1.6 M^-2S^-1 and 5.6 M^-1S^-1, respectively, an advantageous property for acting as scavenger of reactive oxygen species (ROS). This valuable conjunction of properties results from, the conversion of [Mn^IV(SaIbUtO)X] into [Mn^III(salbutO)]₂ in equilibrium with its monomer [Mn ^III(salbutO)].

Full text of DOI:10.1002/ejic.200901018

FULL PAPER
DOI: 10.1002/ejic.200901018
Synthesis, Characterization and Combined Superoxide Dismutase and Catalase
Activities of Manganese Complexes of 1,4-Bis(salicylidenamino)butan-2-ol
[a]
[a]
[b,c]
a]
Jean-Pierre Tuchagues,[b,c] and
Verónica Daier, Diego Moreno, Carine Duhayon,
Sandra Signorella*[
Keywords: Manganese / Superoxide dismutase / Catalase / Biomimetic catalyst / Kinetics / Enzyme catalysis
Two MnIV complexes of general formula [Mn(salbutO)X]
salbutO = 1,4-bis(salicylidenamino)butan-2-ol, 1: X = N
: X = SCN] have been prepared and structurally charac-
terized. The crystal structure of 1 shows that salbutO acts
as a pentadentate ligand through the two phenolato-O, two
to efficiently catalyze the dismutation of O
·–
with catalytic
2
–1 –1
[
2
H
3
3
,
rate constant and IC50 values of 1.91ϫ106
1.43 µ , respectively, which were obtained through the nitro
blue tetrazolium photoreduction inhibition SOD assay, in
aqueous solution of pH 7.8. The Mn-salbutO complexes also
M
s
and
M
3
–
imino-N, and one alcoholato-O atoms, and the sixth coordi- show catalase activity in methanol and dmf, with kcat = 1.6
–
2
–1
–1 –1
nation position is occupied by the azido-N atom, resulting in
M
s
and 5.6
M
s , respectively, an advantageous prop-
IV
a slightly distorted N
3
O
3
donor set around the Mn ion. ESI-
erty for acting as scavenger of reactive oxygen species (ROS).
This valuable conjunction of properties results from the con-
version of [Mn (salbutO)X] into [Mn (salbutO)] in equilib-
2
1
MS, UV/Vis, and H NMR spectroscopy were used for solu-
tion studies. In methanol and dmf, the starting complexes are
IV
III
III
III
converted into [Mn (salbutO)] and its dimeric form. The
rium with its monomer [Mn (salbutO)].
III
IV
E1/2 of Mn /Mn (ca. 0.4 V vs. Ag/AgCl) allows this couple
Introduction
nese-based complexes has been investigated as low-molecu-
[
10–15]
lar-weight catalytic scavengers of H O .
Particularly
2
2
Manganese is known to be an essential element in many
biological systems, and its oxidation-reduction chemistry is
especially important for the electron-transfer reactions of
mitochondrial superoxide dismutase, bacterial catalases,
attractive are complexes exhibiting combined CAT and
SOD activity, because they offer a possible therapeutic ad-
vantage arising from their multiple mechanism of ac-
[16–18]
tion.
Here, we report the synthesis, structure, proper-
[
1]
and photosystem II in green plant photosynthesis. Cata-
lases (CATs) and superoxide dismutases (SODs) efficiently
ties, and combined SOD and CAT activity of two novel
manganese complexes, [Mn(salbutO)N ] (1) and [Mn(sal-
3
2
–
·–
and O2
catalyze disproportionation of intracellular O2
butO)SCN] (2), based on the asymmetric Schiff base ligand
and provide a vital biological defense against these toxic
oxygen metabolites through a mechanism involving cyclic
oxidation and reduction of the metal cofactor. In MnSODs,
the active site contains one pentacoordinate Mn ion in a
1
,4-bis(salicylidenamino)butan-2-ol (H salbutO). Further,
3
we compare their structure/activity with that of Mn com-
plexes of symmetric Schiff base ligands with different ali-
phatic bridges, as a means to evaluate the effect of the
length and symmetry of the aliphatic unit on the properties
and activity of Mn complexes.
[
2,3]
N O environment,
whereas MnCATs catalyze the dis-
3
2
proportionation of H O by using a bis[µ-oxido(hy-
2
2
droxido)]-µ-carboxylatodimanganese structural unit as the
[
4,5]
active site.
Owing to their potential application as thera-
peutic agents against oxidative stress, various mononuclear
Mn complexes have been selected for pharmaceutical uses
·
–
[6–9]
as O2 scavengers,
and a number of dinuclear manga-
[
a] IQUIR (Instituto de Química Rosario), CONICET, Uni-
versidad Nacional de Rosario
Results and Discussion
Suipacha 531, S2002LRK Rosario, Argentina
Fax: +54-341-4370477
E-mail: signorel@infovia.com.ar
Solid State Characterizations
[b] LCC (Laboratoire de Chimie de Coordination), CNRS
2
05, route de Narbonne, 31077 Toulouse, France
Crystal structure of [Mn(salbutO)(N )] (1)
[c] UPS, INPT; LCC, Université de Toulouse
1077 Toulouse, France
3
3
The lattice consists of discrete Mn(salbutO)N molecules.
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.200901018.
3
The molecular structure of complex 1 is illustrated in Fig-
Eur. J. Inorg. Chem. 2010, 965–974
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965

V. Daier, D. Moreno, C. Duhayon, J.-P. Tuchagues, S. Signorella
IV
FULL PAPER
ure 1, together with relevant bond lengths and angles. The decrease in metal–ligand bond lengths when Mn Schiff
II
II
asymmetric unit consists of crystallographically indepen- base complexes are compared with those of Mn (i.e. Mn –
3
–
II
[30]
dent Mn complex molecules in which salbutO acts as a Ophenoxo 2.054, Mn –N
2.258 Å),
there is little dif-
imino
III
pentadentate ligand through the two phenolato-O, two ference from metal–ligand bond lengths of Mn Schiff
III
III
imino-N, and one alcoholato-O atoms, and the sixth coordi- base complexes (Mn –O
1.855–1.902 and Mn –
phenoxo
nation position is occupied by the azido-N atom, resulting Nimino 1.987–2.044 Å).[31–35] However, like most Mn com-
IV
[
26,28,29,36]
in a N O donor set. The coordination environment around plexes with octahedral coordination environment,
3
3
the Mn center can be described as slightly distorted octahe- the pseudo-octahedral O N Mn polyhedron in 1, although
3
3
dral. Most cis and trans angles at the metal center are in showing a slight axial elongation along N1···N3 (average
the range 88.54–92.28° and 177.53–178.24°, respectively. values of 2.000 and 1.896 Å for the axial and equatorial
The O2–Mn1–O1, O2–Mn1–N2, and O2–Mn1–O3 angles bonds, respectively), does not show the Jahn–Teller distor-
III
differ by 4–8° from the ideal ones because of ligand con- tion typical of Mn .
straints imposed by the adjacent five- and six-membered
The crystal packing of complex 1 (Figure 2) may be de-
IV
chelate rings. In this compound, the Mn cation accommo- scribed as an extended 3D network due to numerous inter-
dates the pentadentate ligand forming four adjacent six-six- molecular hydrogen-bonding contacts (20 for each complex
five-six-membered chelate rings. The different bite angles molecule) involving the oxygen atoms from coordinated
and flexibilities of the methylene and ethylene bridges sus- alkoxide and phenoxide groups, both terminally coordi-
tain the observed distortion of the coordination octahe- nated and uncoordinated azido nitrogen atoms, and imino,
dron.
phenolic, and aliphatic carbon atoms. A more detailed de-
scription is of interest: As shown in Figure 2, the unit cell
(z = 4) includes four symmetry-related molecules, where the
basic one (A, x, y, z) and its congener through the inversion
center (D, 1–x, 1 – y, 1 – z) are connected to molecules C
(1/2 + x, 1/2 – y, –1/2 + z) and B (1/2 – x, 1/2 + y, 1.5 – z),
respectively, through four contacts (C11H···O1 3.248,
C12H···O2 3.176, C14H···O2 3.302, and C14H···C10,
3
.588 Å). These two pairs of complex molecules are inter-
connected through C5H···N5 (A···C) and N5···HC5 (B···D),
.497 Å, contacts. In addition, each complex molecule of
3
the unit cell is connected to seven molecules of adjacent
units. As an example, for A, the contacts involved are
{C3H···N3 and N3···HC3}, 3.265 Å (E, –x, –y, 1 – z),
N5···HC5 (G, –1/2 + x, 1/2 – y, 1/2 + z), N5···HC16 (I, 1/2
+
+
x, 1/2 – y, 1/2 + z), C16H···N5 (J, –1/2 + x, 1/2 – y, –1/2
z), {C15···HC8 3.467, C16···HC8 3.593, C17···HC8
3.814 Å} (F, –1 + x, y, z), {C8H···C15, C8H···C16,
C8H···C17} (K, 1 + x, y, z), and {O1···HC11, O2···HC12,
3
Figure 1. Plot of the asymmetric unit of [Mn(salbutO)N ] (1) at the
3
0% probability level with atom numbering. Hydrogen atoms have
been omitted for clarity. Selected bond lengths (Å) and angles (°):
Mn1–N1 2.008(2), Mn1–N2 1.983(2), Mn1–N3 1.991(2), Mn1–O1
1
.8619(17), Mn1–O2 1.8482(18), Mn1–O3 1.8926(18), N1–Mn1–
N3 178.24(10), N2–Mn1–O1 177.53(8), O3–Mn1–O2 171.94(8),
N1–Mn1–N2 92.28(9), N3–Mn1–N2 89.43(10), N1–Mn1–O3
8
8.70(9), N3–Mn1–O3 90.85(9), N2–Mn1–O3 90.36(8), N1–Mn1–
O1 88.87(8), N3–Mn1–O1 89.44(9), O3–Mn1–O1 91.86(8), N1–
Mn1–O2 88.54(9), N3–Mn1–O2 92.1(1), N2–Mn1–O2 82.19(8),
O1–Mn1–O2 95.65(8).
The average Mn–O/N distance of 1.931 in complex 1
IV
compares well with those reported for another Mn O N
3
3
Schiff base complex (Mn–O/Nav 1.934 Å),[ the Mn–N
length of 1.991 Å in 1 is shorter than those found for Mn
19]
azido
III
complexes (2.21–2.35 Å),[
20,21]
and the Mn–Ophenoxo and
Mn–Nimino distances in 1 lie within the respective ranges
of 1.82–1.92 and 1.981–2.01 Å found for other structurally
IV
[22–29]
characterized Mn complexes of Schiff base ligands.
It is important to notice that, although there is a marked lecular hydrogen-bonding interactions.
Figure 2. Crystal packing diagram for 1, emphasizing the intermo-
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Manganese Complexes of 1,4-Bis(salicylidenamino)butan-2-ol
–1
O2···HC14, C10···HC14} (L, 1/2 – x, –1/2 + y, 1.5 – z). As 2.065 (1), 2.04 (2); J (cm ) = –0.05 (1), –0.30 (2); Par (para-
a result, the supramolecular network is made of complex magnetic contribution) = 0.6% (1), 0.05% (2), agreement
2
2
–5
molecules of 1 tightly associated in one-dimensional (1D) factor R = Σ[(χ T) – (χ T) ] /Σ[(χ T) ] = 4.7 10
M
obs
M
calc
M
obs
chains through the C11H···O1, C12H···O2, C14H···O2, and (1), 1.3 10–4 (2).
C14H···C10 contacts; these chains are in turn more loosely
interconnected to yield a 3D network through the
C3H···N3, C5H···N5, C16H···N5, C8H···C15, C8H···C16,
and C8H···C17 contacts described above (Table S1).
FTIR Spectroscopy
Comparison of the IR spectra of 1 and 2 evidences the
fingerprint” pattern of salbutO3– coordinated to the Mn
“
ion and confirms their analogous structures. The IR spectra
Magnetic Properties
of complexes 1 and 2 (Figure 4) exhibit strong imine and
–1
The room-temperature magnetic moment (µ ) of com- phenolato absorptions at 1618 and 1605 cm , downshifted
eff
plexes 1 and 2 in the solid state is 4.04 and 4.09 BM, respec- by approximately 15 cm–1 from those in the free ligand be-
tively, close to the spin-only magnetic moment expected for cause of the coordination of the metal to these groups, and
3
–1
a d ion (µ = 3.87 MB for g = 2). Variable-temperature one strong band at 2031 (1) [2058 (2)] cm attributable to
SO
magnetic susceptibility measurements on 1 and 2 were per- coordinated N3– [SCN ], in agreement with their molecular
formed in the 2 to 300 K temperature range on cylindrical structure. Powder samples of both compounds display a
pellets of 3 mm diameter pressed from ground microcrys- broad band at approximately 3450–3400 cm–1 assigned to
tals. Plots of the inverse corrected molar susceptibility vs. non-coordinated water molecules. Except for the νOH ab-
temperature yielded straight lines, indicating Curie–Weiss sorption, the powder and crystalline samples of 1 show
behavior. The temperature intercept of these plots gave ex- identical IR spectra.
–
perimental Weiss constants (θ) of –1.84 K for 1 and –6.6 K
for 2. The Curie constant (C) values of 2.05 (1) and 2.2 (2)
are also close to the expected value for one non-interacting
IV
Mn ion (S = 3/2 and g = 2), and the negative θ value
suggests the operation of weak antiferromagnetic interac-
tions in these complexes. Considering the mononuclear na-
ture of 1 and 2 and the molecular structure of 1, their mag-
netic behavior may originate from antiferromagnetic inter-
molecular spin–spin interactions and/or single-ion zero-
IV
field-splitting (zfs) of Mn , the latter effect being usually
IV
weak in the case of Mn . In view of the minute axial elong-
ation of the coordination octahedron along N1···N3 in 1,
we neglected the possible operation of axial zfs. Taking into
account the 1D chains formed through C11H···O1,
C12H···O2, C14H···O2, and C14H···C10 contacts, we fitted
the magnetic data by considering chain interactions. As
shown in Figure S1 and Figure 3 for 1 and 2, respectively,
Figure 4. FTIR spectra of complexes 1 and 2.
the fits obtained when computing the magnetic suscep-
tibility with the assumption of a Heisenberg chain of S =
[
37]
3/2 spins
were fairly good for the parameter values g = Solution Studies
UV/Vis Spectra
The UV/Vis spectrum taken immediately after preparing
a dmf solution of complex 1 [Figure 5(a)] is characterized
–1
–1
by three absorption bands at 340 nm (8680  cm ),
–1
–1
–1
–1
4
00 nm (6730  cm ), and 490 nm (4000  cm ). The
electronic spectrum of this complex is in agreement with
IV
those reported for other mononuclear Mn Schiff base
[
26,28]
complexes.
The strong absorbance at 340 nm can be
assigned to a ligand-centered transition, while the other two
intense absorptions of lower energy are likely to be phen-
IV
olato-to-Mn charge-transfer transitions, as observed for
IV
[22–24,26]
other Mn
complexes with phenoxido ligands.
These strong charge-transfer transitions probably obscure
–1
–1
the low-intensity (ε Յ 200  cm ) absorption bands ex-
M M
Figure 3. Temperature dependence of χ (᭺) and χ T (∆) for com-
pound 2. The solid lines show the best fit based on the Heisenberg
chain model (see text).
IV 4
4
4
4
pected for the Mn
A2g Ǟ T and A Ǟ T d–d
2g 2g 1g
transitions (octahedral approximation).
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V. Daier, D. Moreno, C. Duhayon, J.-P. Tuchagues, S. Signorella
FULL PAPER
sponding MnIII complex. In this solvent, the electronic
spectrum [Figure 5(b)] is characterized by two strong ab-
–1
–1
sorptions at 215 nm (7590  cm ) and 233 nm
–1
–1
(
6980  cm ), corresponding to ligand-centered transi-
tions: one phenolato-to-metal charge-transfer at 298 nm
–
1
–1
(
(
2820  cm ) and a weak d–d transition at 480 nm
–
1
–1
III
700  cm ) with the characteristic intensity of Mn
[
32,33,38]
complexes.
The protic solvent probably facilitates
the loss of the coordinated azide anion (as observed in the
ESI mass spectra) resulting in the decrease of the redox
IV
III
stability of the Mn complex that converts to the Mn
species.
ESI Mass Spectrometry (ESI-MS)
ESI mass spectra of complexes 1 and 2 in methanol or
acetonitrile confirmed their chemical composition in solu-
tion. For both complexes, the main peak is observed at m/z
=
365 (100% intensity) in the positive mode ESI mass spec-
tra [see Figure 6(a) for the spectrum of 2] and originates
+
from the [Mn(salbutOH)] monocation. In the whole set
of mass spectra registered at different times and complex
concentrations, two other peaks are observed at m/z = 728
and 729, the isotopic pattern of which matches very well
+
the simulated spectra for dimers [Mn (salbutO) ] and
2
2
+
III
IV
[
Mn (salbutO) H] (Figure S2). Since the Mn Mn
2 2
Figure 5. Electronic spectra of 1 (a) immediately (black line) and
+
mixed-valence species [Mn (salbutO) ] is not observed by
30 min (gray line) after dissolution in dmf; (b) in methanol.
2
2
EPR spectroscopy, it must be generated within the spec-
trometer from the neutral [Mn (salbutO) ] dimer. The coex-
2
2
The initial spectrum of a 5ϫ10–5  solution of 1 in dmf istence of neutral and cationic [Mn (salbutO(H))]
III
0/+
and
gradually changed to the gray line spectrum shown in Fig- [MnIII
(salbutO(H))
]
0/+
species in solution could be the
2
2
ure 5(a) as time passed. After 30 min, the spectrum did not cause of the low molar conductivity value measured for
exhibit any further change. The spectrum of the new species these compounds in methanol. The intensity of the peaks
formed in solution is characterized by three absorption at m/z = 728 (729) relative to the monomer (m/z = 365)
–
1
–1
–1
–1
bands at 315 nm (6300  cm ), 365 nm (5300  cm ), decreases from acetonitrile to methanol [Figure 6(a) and
–
1
–1
and 500 nm (645  cm ), which can be assigned to intrali- Figure S3]. Moreover, addition of HClO (1 µ) to the
4
gand π–π*, phenolatoǞM charge-transfer, and d–d transi- methanol solution of the complex causes further decrease
tions, respectively. The energy and intensity of the LMCT in the intensity of the peak at m/z = 728 to around 5% of
and d–d transitions are in agreement with those reported
III
[32,33,38]
for related Mn complexes.
These results indicate
IV
that the Mn (salbutO)N complex is not stable in solution
and converts to a Mn complex. The stability of the Mn
3
III
IV
complex in solution is significantly decreased by the pres-
ence of trace HCl or increased amounts of H O in the sol-
2
vent. More concentrated dmf solutions of 1 require longer
III
times for complete conversion to the reduced Mn form.
Water substitution of the azide anion followed by oxidation
IV
of coordinated water could be responsible for the Mn re-
dox instability in solution. The lower water to complex ratio
in the more concentrated solutions of 1 would explain the
slower reduction. Alternatively, the redox instability of 1
could be due to the presence of trace amounts of methanol
or dimethylamine, which are difficult to avoid in dmf.
–
5
Diluted 5ϫ10  solutions of 2 in dmf rapidly convert
III
to the Mn species, and the first electronic spectrum taken
III
after mixing corresponds to the Mn complex, thus indi-
–
–
cating the lower stabilizing effect of SCN vs. N .
3
The electronic spectra of solutions of complexes 1 and 2
in methanol showed immediate conversion to the corre- spectrum of 2 in [D
1
Figure 6. ESI mass spectrum of 2 in acetonitrile (a) and H NMR
]methanol (ca. 10 m) (b).
4
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Manganese Complexes of 1,4-Bis(salicylidenamino)butan-2-ol
the main peak with m/z = 365. The peaks belonging to the
dimeric species disappear when [HClO ]Ն0.10 m (Fig-
4
ure S4), thus showing that protons disfavor dimer forma-
tion.
1H NMR Spectroscopy
NMR spectroscopy has proved to be a useful probe of
the ligand conformation for Schiff base complexes of Mn
in solution. In Mn–salicylidenamino complexes, the reso-
nances of the protons ortho to the O-phenoxide (H3) and
imino (H6) groups of the ligand are normally too broad to
[
39]
be detected because of their closeness to the Mn center.
1
Therefore, H NMR spectra of tetragonal mononuclear Mn
complexes with Schiff base ligands symmetrically posi-
tioned in the equatorial plane show two up-field resonances
around –20 to –25 ppm assigned to H4 and H5 protons of
the phenolato ring.[
40–43]
However, a more complex pattern
1
is observed in the H NMR spectra of Mn complexes in
which the ligand is not symmetrically positioned around
[
31b,40]
1
the Mn ion.
The paramagnetic H NMR spectra of
complexes 1 and 2 in [D ]methanol show a common pattern
4
with five signals ranging from +24 to –13 ppm [Figure 6(b)].
Resonances observed at 24, 16, –7, and –13 ppm may arise
from two pairs of nonequivalent H4, H5 ring protons, while
the signals at 20 and 21 ppm may arise from the methylene
protons of the butane backbone.[
31b]
The magnetic non-
equivalence of the phenolato protons may be the result of
the different extent of spin delocalization over the protons
of the phenolato trans to the imine group vs. that of the
1
phenolato trans to the alcoholato-O atom. Therefore, H
NMR spectra indicate that the arrangement of the ligand
in the solid state is retained in solution, in both the mono-
mer and dimer forms of the complex.
Figure 7. Cyclic voltammogram of (a) 2 in methanol, (b) 2 in dmf
at various scan rates between 50 and 1000 mV, and (c) 1 in dmf a
few minutes after dissolution. Conditions: Pt/Pt/Ag/AgCl; conc.:
1
4 6
m; supporting electrolyte: Bu NPF . Scan rate in (a) and (c):
–
1
Electrochemical Studies
100 mVs .
The electrochemical properties of complexes 1 and 2
were investigated by cyclic, linear, and square-wave voltam-
Voltammograms of dmf solutions of complex 2 recorded
metry in methanol and dmf solutions containing 0.1  at different times show a quasi-reversible oxidation wave
III
IV
Bu NPF . In methanol, the two complexes show the same at 360 mV that corresponds to the Mn /Mn couple, as
4
6
electrochemical behavior, in agreement with the analogous confirmed by linear and square-wave voltammetry. This
spectroscopic pattern they exhibit in this protic solvent. The process is diffusion-controlled. Cyclic voltammograms at
cyclic voltammograms of 1 and 2, taken 30 min after the different scan rates are shown in Figure 7(b). An additional
III
preparation of their methanol solutions, display one quasi- nonreversible reduction wave that corresponds to the Mn /
II
reversible oxidation wave at E1/2 = 425 mV, with a peak-to- Mn couple was observed at around –400 mV in the cath-
peak separation of 110 mV (at 100 mV/s scan rate), slightly odic scan. In addition, the voltammogram displays one ad-
above the value expected for a one-electron electrochemi- ditional peak in the anodic scan at E1/2 = 1140 mV that
–
cally reversible process, and a nonreversible reduction at corresponds to the oxidation of the SCN anion.
–450 mV [Figure 7(a)]. Voltammetry at a rotating electrode
In the voltammograms recorded immediately after prep-
confirmed that the waves at 425 mV and –450 mV corre- aration of dmf solutions of complex 1 [Figure 7 (c)], a non-
spond to an oxidation and a reduction process, respectively. reversible reduction peak was observed at –66 mV, in ad-
W1/2 values of approximately 130 mV in the square-wave dition to the quasi-reversible oxidation wave at 360 mV cor-
III
IV
voltammetry experiments suggest that they correspond to responding to the Mn /Mn couple analogous to that ob-
III
IV
one-electron processes attributed to the Mn /Mn and served in dmf solutions of complex 2. The reduction peak
III
II
IV
III
IV
Mn /Mn redox couples. The irreversibility of the re- may correspond to the Mn /Mn couple of the [Mn (sal-
II
duction process suggests that reduction to Mn results in a butO)N ] complex 1, while the oxidation wave may be at-
chemically transformed species generated at the electrode. tributed to the Mn /Mn couple of the [Mn (salbutO)]
3
III
IV
III
The additional peak at 880 mV observed in the anodic scan complex formed upon loss of the azido ligand. The assign-
–
IV
corresponds to the oxidation of the SCN anion.
ment of the peak at –66 mV to the reduction of [Mn -
Eur. J. Inorg. Chem. 2010, 965–974
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969

V. Daier, D. Moreno, C. Duhayon, J.-P. Tuchagues, S. Signorella
Inhibition percentages were measured for several com-
FULL PAPER
(
salbutO)N ] is supported by the increased intensity of the
3
oxidation peak of the free azide at E1/2 = 1130 mV upon plex concentrations, and the IC50 value, graphically evalu-
decrease in intensity of the peak at –66 mV. ated, was 1.43 µ for the two complexes. On the basis of
The Mn /Mn redox potential of [Mn(salbutO)] is sim- competition with NBT, at 50% inhibition, the rates of the
IV
III
·
–
ilar to those of [Mn(salpn)(OMe)] [458 mV vs. Ag/AgCl, reactions of NBT and the mimic with O2 are equal, kcat
2
H salpn = 1,3-bis(salicylidenamino)propane] and [Mn- [catalyst] = k
[NBT], where kNBT (pH = 7.8) =
2
NBT
–1 –1 [45,46]
4
(
salpn)(acac)](523 mVvs.Ag/AgCl),whichhaveacis-β-tetra- 5.94ϫ10  s .
Hence, the catalytic rate constant,
[31b]
dentate salpn ligand,
but much lower than those found kcat = k
[NBT]/IC , was calculated to be k
NBT
6 –1 –1
=
cat
50
+
for the tetragonal complexes [Mn(salpn)(MeOH) ] and 1.91ϫ10  s . This value is independent of the detector
2
+
[
Mn(salpnOH)] [H salpnO = 1,3-bis(salicylidenamino)- concentration and appropriate for comparison with litera-
3
[
40]
propan-2-ol], with the ligand in the equatorial plane and ture values. The SOD-like activity of the Mn-salbutO com-
5
no alkoxido group bound to Mn. The latter complexes plex is similar to that of Mn-salen [k = 8ϫ10 , H salen
cat
2
III
II
[6]
show Mn /Mn reduction at –98 and –172 mV vs. Ag/ = 1,2-bis(salicylidenamino)ethane], and higher than those
AgCl (methanol), respectively, without a metal-centered of other Mn-SOD mimics with open chain ligands having
[
47]
[48]
[17]
oxidation wave in the anodic scan. The redox potential of phenolato,
pyridyl,
donor sites. These results clearly indicate that
that found for [(Mn salpentO)(OMe)(OAc)] [384 mV vs. [Mn(salbutO)] is a suitable SOD mimic.
benzymidazolyl,
and pyraz-
III
IV
[49]
the Mn /Mn couple of [Mn(salbutO)] is also similar to olyl
+
2
Ag/AgCl, H salpentO = 1,5-bis(salicylidenamino)pentan-3-
It has been observed that the catalytic rate constants for
3
ol],[ in which the ligand is located in the meridional plane the dismutation of the superoxide anion are related to the
44]
III
[50]
affording six-membered chelate rings around each manga- metal-centered reduction potential of Mn compounds.
3
–
IV
nese ion. In addition, salbutO stabilizes Mn complexes The closer this potential approaches the midpoint potential
·
–
more poorly than other ligands with a similar donor set between the oxidation and reduction of O2 (E1/2 = 0.12 V
that form five-membered chelate rings around Mn.[ Thus, vs. Ag/AgCl) the more potent the mimic. The Mn /Mn
26]
III
II
the presence of the coordinated alkoxido group combined potential of [Mn(salbutO)] is too negative to account for
·
–
with the ligand arrangement around the metal center and any efficient redox cycling of O2 . Thus, it is the accessi-
IV
the size of the chelate rings adjust the potential of the bility of the Mn state that enables this complex to redox
III
IV
·–
Mn /Mn
00 mV.
cycle in [Mn(salbutO)] to approximately cycle O2 and be a powerful SOD mimic.
4
SOD Activity
CAT Activity
In order to evaluate the activity of complexes 1 and 2
toward superoxide in aqueous buffer, the nitro blue tetrazol-
The catalytic activity of complexes 1 and 2 toward H O
2 2
ium (NBT) assay was used. This assay is based on kinetic disproportionation was investigated in methanol and dmf
competition for the superoxide reaction between NBT and at 25 °C. Addition of H O to previously stabilized dmf or
2 2
the complex with SOD activity. In this way, the SOD ac- methanol solutions of complexes 1 and 2 causes immediate
tivity is inversely related to the amount of formazan, the vigorous evolution of dioxygen. Volumetric measurements
purple product formed by reaction of NBT with superoxide, of evolved O
observed at 560 nm. When added to the reaction mixture, to disproportionate more than 1200 equiv. of H
both 1 and 2 were found to inhibit the reduction of NBT, only slight lowering of activity. During catalytic dispropor-
showed that, in dmf, these complexes are able
2
O
2
with
2
as shown in Figure 8.
tionation of H
lengths, and a new electronic transition is observed at
10 nm [Figure 9 (a)]. This band, which appears at very
2 2
O , the LMCT band shifts to lower wave-
5
short reaction times and disappears when O evolution has
2
ceased, may account for the formation of a catalyst–sub-
strate adduct, generated by direct binding of H O to the
2
2
complex through ligand-shift. Formation of this intermedi-
ate is consistent with the increase in intensity of the 510 nm
band with increasing [H O ] or [catalyst]. The absence of a
2
2
signal in the EPR spectra taken during the reaction ex-
cludes the possibility that this intermediate corresponds to
II
a mixed-valence or Mn species. At the end of the reaction,
the electronic spectrum and the cyclic voltammogram [inset
in Figure 9 (a)] of the final form of the catalyst are analo-
gous to those of the starting dmf solutions of the complex.
In methanol, these complexes are able to disproportionate
up to 200 equiv. of H O , and then they are inactivated. In
2
2
this solvent, the absorption pattern of the electronic spectra
shows only slight changes during the reaction course [Fig-
Figure 8. SOD activity of complexes 1 and 2 in the riboflavin-
methionine-NBT assay.
970
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© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2010, 965–974

Manganese Complexes of 1,4-Bis(salicylidenamino)butan-2-ol
ure 9 (b)]. In the protic solvent, the monomer/dimer equilib- with decreasing proton donor ability of the solvent: meth-
rium shifts toward the monomer, reducing the concentra- anol + acid to methanol (αmethanol = 0.93) to acetonitrile
tion of dimer available for catalase activity.
(αacetonitrile = 0.19), supports that in dmf, a nonprotic sol-
vent (αdmf = 0), this ratio should be much higher.
2 2 0
Figure 10. Effect of (a) [catalyst] ([H O ] = 12.9 m) and (b)
[H
2
O
2
] on the initial rate of H disproportionation at 25 °C in
2 2
O
dmf.
The CAT-like activity of the salbutO3– complex, al-
though lower than those observed for other dinuclear or
+
dimeric catalysts, such as [Mn (salpentO)(OMe)(OAc)] or
2
[
44,51]
[
Mn(salpnO)]2,
is significantly higher than those for
and Mn-bipyridinephen-
Figure 9. Electronic spectra of 2 before (black line) and after (gray olato series, which also show combined CAT/SOD activi-
[
52]
complexes of the Mn-salen
[
16]
2 2
line) addition of 300 equiv. of H O , in (a) dmf (b) methanol. Inset:
Cyclic voltammogram at the end of the reaction in dmf.
ties. This result is probably related to the higher proportion
of dimer (required for CAT activity) in solutions of the Mn-
salbutO complex than in solutions of the Mn-salen and
Mn-bipyridinephenolato complexes. Because peroxide is
produced in vivo during oxidative stress, the ability to con-
The initial rate of disproportionation of H O was deter-
2
2
mined as a function of the complex and substrate concen-
trations in methanol and dmf by measuring dissolved oxy-
gen with a Clark-type electrode. It was found that, in both
solvents, complexes 1 and 2 afford identical kinetic param-
sume H O2 is an advantageous property of the Mn-
salbutO complex to scavenge reactive oxygen species (ROS).
2
eters. In dmf, the reaction is first-order in catalyst and H O2
2
(
Figure 10) with a second-order rate constant (kcat), ob-
Conclusions
–
1
tained from the slope of r /[cat] (s ) vs. [H O ], of
5
in catalyst (Figure S5) and first order in H O , with a third- is able to stabilize Mn under conditions where related
order kcat of 1.6Ϯ0.2  s . The different dependence of symmetric Schiff bases yield Mn complexes: the shorter
i
2
2
–
1 –1
.6Ϯ0.1  s . In methanol, the reaction is second-order
The results presented in this work show that H salbutO
3
IV
2
2
–
2
–1
III
III
the rate of H O disproportionation on catalyst concentra- H salpnO affords mononuclear Mn complexes, their di-
2
2
3
[
32,40,53]
tion in the two solvents may be interpreted in terms of the mers, or polymeric chains;
the longer H salpentO
3
unfavorable effect of the protic solvent on dimer formation. yields dinuclear Mn complexes.[44,54–56] Thus, the length
Thus, in methanol, where an equilibrium between monomer and symmetry of the aliphatic bridging units between the
and dimer exists (the monomer being the major form in central alcohol function and the imino-N donor sites of
III
solution, as observed in the ESI mass spectra), the rate is salbutO3– modulates not only the structure of the resulting
2
given by r = k Kdimer [H O ] [cat] , where K
is the di- complex but also the Mn oxidation state.
2
2
dimer
merization equilibrium constant and k is the rate constant
Complexes [Mn(salbutO)N ] and [Mn(salbutO)SCN] are
3
for the reaction of the dimer with H O . Distinctly, in dmf, not stable in methanol or diluted dmf solutions and convert
2
2
III
the first-order dependence suggests that dimerization is ther- to [Mn (salbutO)] in equilibrium with the dimer. The li-
modynamically more favored [Kdimer(dmf) ϾϾKdimer(methanol)]. gand arrangement around the metal in the monomer is
III
Therefore, if the catalyst exists in solution as a preformed close to that in the dimeric form of the Mn complex, as
dimer, r = k [H O ][dimer], just as observed. The increasing no additional resonances are observed in the 1H NMR
2
2
dimer/monomer ratio observed in the ESI mass spectra spectra of the complexes. The fact that Mn-salbutO3– shows
Eur. J. Inorg. Chem. 2010, 965–974
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
971

V. Daier, D. Moreno, C. Duhayon, J.-P. Tuchagues, S. Signorella
better SOD and CAT activities than those of catalysts of a microwave frequency generated by a Bruker ER 04 (9–10 GHz)
FULL PAPER
1
[
16]
instrument. H NMR spectra were recorded with a Bruker AC 200
NMR spectrometer at ambient probe temperature (ca. 26 °C), with
a nominal operating frequency of 200.1 MHz. Variable-tempera-
ture magnetic susceptibility data were obtained with a Quantum
Design MPMS SQUID susceptometer, under a magnetic field of
the Mn-salen series
makes this complex particularly at-
tractive as ROS scavenger for pharmaceutical purposes. The
ligand arrangement around Mn and the additional alkoxido
3
–
donor site in the Mn-salbutO complex shift the metal-
centered redox potentials to values lower than those in Mn-
1
.0 T (1) and 0.5 T (2) in the temperature range 2–300 K. Diamag-
III
salen. This facilitates the redox reaction through the Mn /
[58]
netic corrections were applied by using Pascal’s constants. Least-
IV
Mn cycle and results in improved activity.
squares fittings were accomplished with an adapted version of the
function-minimization program MINUIT.[
59]
Conductivity mea-
surements were performed by using a Horiba F-54 BW conductiv-
ity meter, on 1.0 m solutions of the complexes in methanol. The
electrochemical experiments were performed with a computer-con-
trolled Princeton Applied Research potentiostat, model VERSAS-
TAT II, with model 270/250 Research Electrochemistry Software.
Studies were carried out under Ar, in dmf or methanol solutions
Experimental Section
Materials: All reagents or AR chemicals were used as purchased.
Solvents were purified by standard methods. The concentration of
H
2
O
2
stock solution was determined by iodometric titration.
,4-Bis(salicylidenamino)butan-2-ol (H salbutO): H salbutO was
prepared by Schiff base condensation of salicylaldehyde with 1,4-
–
3
4 6
with Bu NPF (0.1 ) as supporting electrolyte and a ca. 10 
1
3
3
solution of the complex. The working electrode was a Pt wire and
the reference electrode was Ag/AgCl with Pt as the auxiliary elec-
trode. Using the described conditions, the ferrocene/ferrocenium re-
[
57]
diaminobutan-2-ol
pure yellow solid by precipitation from the reaction mixture at
room temperature. Yield: 73%. C18 (312.37): calcd. C
9.21, H 6.45, N 8.97; found C 69.31, H 6.34, N 8.92. H NMR
200 MHz, [D ]dmso, 25 °C, TMS): δ = 8.66 (s, 2 H, N=CH-), 7.44
m, 4 H, Ar), 6.99 (m, 4 H, Ar), 3.93–3.80 [m, 5 H, H-C(OH)-,
CH -N=C], 1.90 [m, 2 H, (OH)CH-CH -CH ] ppm. Significant
in ethanol at 60 °C, and was isolated as a
dox couple was observed at E1/2 = 417 mV in methanol and E1/2
=
20 2 3
H N O
1
491 mV in dmf.
6
(
(
-
6
Disproportionation of H
portionation catalyzed by 1 and 2 was measured by volumetric de-
termination of O evolved from reaction mixtures in dmf or meth-
anol as described previously.
2 2 2 2
O : The stoichiometry of the H O dispro-
2
2
2
2
IR bands (KBr): ν˜ = 3425 (OH, broad), 3048, 2921, 2850 (CH),
[60]
Kinetic studies were carried out
–
1
1
634 (C=N), 1609 (Ar), 754, 740 (CH rock) cm .
Mn(salbutO)(N )]·0.5H O (1·0.5H O): To a solution of freshly
prepared Mn(OAc) ·2H O (86 mg, 0.32 mmol) and H
0.1 g, 0.32 mmol) in methanol (8 mL) was added NaN
polarographically by using a Clark-type oxygen electrode with an
YSI oxygen-monitoring system (Model 5300, Yellow Springs In-
struments Co., Inc.). The initial rate method was used to determine
the rate constants (see ref.[ for further details). Each rate constant
reported here represents the average value of multiple determi-
nations that fall within Ϯ5%.
[
3
2
2
3
2
3
salbutO
3
(42 mg,
60]
(
0.64 mmol) in methanol (2 mL), and the reaction mixture was
stirred for 24 h. A dark brown microcrystalline precipitate formed,
which was collected by filtration, washed with methanol, and
dried under vacuum. Yield: 75 mg (0.18 mmol, 58%).
C H17MnN O ·0.5H O (415.30): calcd. C 52.06, H 4.37, Mn 13.2,
18 5 3 2
N 16.86; found C 51.91, H 4.19, Mn 13.4, N 16.53. Significant IR
Indirect SOD Assay: The SOD activity of the complexes was as-
sayed by measuring inhibition of the photoreduction of nitro blue
tetrazolium (NBT), by a slightly modified version of the method
[61]
originally described by Beauchamps and Fridovich.
The solu-
bands (KBr): ν˜ = 3452 (OH, broad), 3052, 3019, 2940, 2914, 2875
–6
tions containing riboflavin (3.4ϫ10 ), methionine (0.01 ),
NBT (4.6ϫ10 ), and complex of various concentrations were
(
4
CH), 2032 (N
3
), 1617 (C=N), 1596 (Ar), 757 (CH rock), 613, 576,
–5
–1
–l
2
–l
49, 410 (MnL) cm . Molar conductivity = 69 Ω cm  . Single
prepared with phosphate buffer (pH 7.8). The mixtures were illumi-
nated with a fluorescent lamp with constant light intensity at 25 °C.
The reduction of NBT was monitored at 560 nm with various illu-
mination periods (t). Rates in the absence and in the presence of
complex were determined for each concentration of complex added
and plotted against it. Inhibition percentage was calculated accord-
crystals of 1 suitable for X-ray diffraction were obtained from the
filtrate of the reaction mixture, which was left to stand for several
days.
[
Mn(salbutO)(SCN)]·2H
2
O (2·2H
2
O): To a solution of Mn(OAc)
salbutO (0.10 g, 0.32 mmol) in
3
·
2H
2
O (172 mg, 0.64 mmol) and H
3
methanol (5 mL) was added KSCN (195 mg, 2.1 mmol) in water ing to: {(∆Abs/t)without complex
–
(∆Abs/t)with complex}ϫ100/
(
1 mL), and the reaction mixture was stirred for 24 h. A dark
(∆Abs/t)without complex. The IC50 value represents the concentration
of the SOD mimic that induces a 50% inhibition of the reduction
of NBT. Control experiments were performed on mixtures of NBT
brown microcrystalline precipitate formed, which was collected by
filtration, washed with methanol, and dried under vacuum. Yield:
0
4
1
broad), 3049, 3025, 2921, 2865 (CH), 2058 (SCN), 1618 (C=N),
1
ductivity = 64 Ω cm  .
3 3 2
.14 g (0.3 mmol, 94%). C19H17MnN O S·2H
O (458.39): calcd. C + complex, riboflavin + complex, and NBT + methionine + com-
9.78, H 4.58, Mn 12.0, N 9.17, S 6.99; found C 49.86, H 3.74, Mn
3, N 9.01, S 6.98. Significant IR bands (KBr): ν˜ = 3413 (OH,
plex, in phosphate buffer, to ensure that the complex does not react
independently with any of the components of the mixture. On the
basis of these experiments, cross reactivity of the complex with
NBT or riboflavin was disregarded. Under conditions used in this
work, the catalytic rate constant (kMcCF) for MnSOD was found
–1
598 (Ar), 757 (CH rock), 613, 577, 455 (MnL) cm . Molar con-
–l
2
–l
to be 5.5ϫ10  s–1, a value consistent with that reported in the
8
–1
Physical Measurements: Electronic spectra were recorded with a
JASCO V550 spectrophotometer having thermostatted cell com-
partments. IR spectra were recorded with a Perkin–Elmer Spec-
trum One FTIR spectrophotometer. Electrospray ionization (ESI)
mass spectra were recorded with a Perkin–Elmer SCIEX 365
LCMSMS mass spectrometer, by using ca. 10–5  solutions of the
[62]
literature.
X-ray Crystal Structure Determination: Crystallographic data for
compound 1, [Mn(salbutO)(N )], were collected at 180 K with an
3
Oxford-Diffraction XCALIBUR CCD Diffractometer equipped
with a Cryojet cooler device from Oxford Instruments and a graph-
–1
complexes in methanol at a flow rate of 5 µLmin . EPR measure-
α
ite-monochromated Mo-K radiation source. The unit cell determi-
ments were made with a Bruker ESP 300 E spectrometer by using
nation and data integration were carried out by using the CrysAlis
972
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© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2010, 965–974

Manganese Complexes of 1,4-Bis(salicylidenamino)butan-2-ol
package.[63] The structure was solved with SIR 92[64] and refined
Robinson), Nova Science Publishers, Inc., New York, 2008, pp.
243–279.
by full-matrix least-squares on F
o
with CRYSTALS,[ with aniso-
65]
[
[
14] B. K. Shin, Y. Kim, M. Kim, J. Han, Polyhedron 2007, 26,
tropic displacement parameters for non-hydrogen atoms. The H
atoms were all located in a difference map, but those attached to
carbon atoms were repositioned geometrically. The H atoms were
initially refined with soft restraints on the bond lengths and angles
to regularize their geometry and isotropic displacement parameters
in the range 1.2–1.5 times Ueq of the parent atom, after which the
positions were refined with riding constraints. Absorption correc-
4557–4566.
15] L. Dubois, J. Pécaut, M. F. Charlot, C. Baffert, M. N. Col-
lomb, A. Deronzier, J. M. Latour, Chem. Eur. J. 2008, 14, 3013–
3025.
[
16] G. M. P. Giblin, P. C. Box, I. B. Campbell, A. P. Hancock, S.
Roomans, G. I. Mills, C. Molloy, G. E. Tranter, A. L. Walker,
S. R. Doctrow, K. Huffman, B. Malfroy, Bioorg. Med. Chem.
Lett. 2001, 11, 1367–1370.
[17] Q. X. Li, Q. H. Luo, Y. Z. Li, Z. Q. Pan, M. C. Shen, Eur. J.
Inorg. Chem. 2004, 4447–4456.
[18] K. Baker, C. Bucay Marcus, K. Huffman, H. Kruk, B. Malfroy,
S. R. Doctrow, J. Pharmacol. Exp. Ther. 1998, 284, 215–221.
19] H. Chun, P. Chaudhuri, T. Weyhermller, K. Weighardt, Inorg.
Chem. 2002, 41,790–795.
20] M. Yuan, F. Zhao, W. Zhang, Z. M. Wang, S. Gao, Inorg.
Chem. 2007, 46, 11235–11242.
21] K. R. Reddy, M. V. Rajasekharan, J.-P. Tuchagues, Inorg.
Chem. 1998, 37, 5978–5982.
[66]
tions were applied by using Multiscan. The molecular plots were
[
67]
[68]
drawn with Cameron and Mercury. Crystal data collection and
refinement parameters for 1 at 180 K: Mo-K (λ = 0.71073 Å),
17MnN , M = 406.297, dark brown needles, dimensions
.1ϫ0.1ϫ0.25 mm, monoclinic, space group: P12 /n1,
.0780(5) Å, b = 12.2813(10) Å, c = 17.2752(12) Å, β =97.074(6)°,
α
C
18
H
5
O
3
r
0
8
1
a =
[
[
[
[
3
–3
–1
V = 1700.8(2) Å , Z = 4, ρcald = 1.59 Mgm , µmo = 0.807 mm ,
F(000) = 836.000, θ range: 3 to 29°, 15798 reflections measured,
2
4
543 unique, 244 refined parameters, GOOF for F 1.0871,
2
2
2
2 2 1/2
wR([Σw(|F
o c o o c o
| – |F |) /Σ w|F | ] ) = 0.040, R(Σ||F | – |F ||/Σ|F |) =
0.034.
22] S. K. Chandra, A. Chakravorty, Inorg. Chem. 1992, 31, 760–
CCDC-743344 contains the supplementary crystallographic data
for this paper. These data can be obtained from The Cambridge
Crystallographic Data Centre free of charge via www.ccdc.cam.
ac.uk/data_request/cif.
765.
[23] S. K. Chandra, P. Basu, D. Ray, S. Pal, A. Chakravorty, Inorg.
Chem. 1990, 29, 2423–2428.
[24] S. Duta, P. Basu, A. Chakravorty, Inorg. Chem. 1991, 30, 4031–
4037.
Supporting Information (see footnote on the first page of this arti-
cle): Hydrogen-bonding interactions and magnetism for complex 1,
[
[
[
[
[
[
25] P. S. Pavacik, J. C. Huffman, G. Christou, J. Chem. Soc., Chem.
Commun. 1986, 43–44.
26] D. P. Kessissoglou, X. Li, W. M. Butler, V. L. Pecoraro, Inorg.
Chem. 1987, 26, 2487–2492.
effect of catalyst on H
lated mass spectra, and ESI mass spectra of 2 in methanol and
HClO /methanol.
2 2
O disproportionation in methanol, simu-
4
27] S. M. Saadeh, M. S. Lah, V. L. Pecoraro, Inorg. Chem. 1991,
30, 8–15.
28] M. Mikuriya, D. Jie, Y. Kakuta, T. Tokii, Bull. Chem. Soc. Jpn.
993, 66, 1132–1139.
Acknowledgments
1
29] T. M. Rajendiran, J. W. Kampf, V. L. Pecoraro, Inorg. Chim.
Acta 2002, 339, 497–502.
We thank the National University of Rosario, the Consejo Na-
cional de Investigaciones Científicas y Técnicas (CONICET), and
the National Agency for Sciences Promotion for financial support,
and CONICET and Centre National de la Recherche Scientifique
30] a) B. Mabad, J.-P. Tuchagues, P. Cassoux, D. N. Hendrickson,
Inorg. Chem. 1986, 25, 1420–1431; b) D. P. Kessissoglou, W. M.
Butler, V. L. Pecoraro, Inorg. Chem. 1987, 26, 495–503; c) D.
Luneau, J. M. Savariault, J.-P. Tuchagues, Inorg. Chem. 1988,
(CNRS) for a bilateral agreement (Res.709/2005).
27, 3912–3918; d) L. Stelzig, B. Donnadieu, J.-P. Tuchagues,
Angew. Chem. Int. Ed. Engl. 1997, 36, 2221–2222; e) L. Stelzig,
[
1] V. L. Pecoraro (Ed.), Manganese Redox Enzymes, VCH, New
York, 1992.
2] W. C. Stallings, K. A. Pattridge, R. A. Strong, M. L. Ludwig,
J. Biol. Chem. 1985, 260, 16424–16432.
A. Steiner, B. Chansou, J.-P. Tuchagues, Chem. Commun. 1998,
7
71–772.
31] a) V. L. Pecoraro, W. M. Butler, Acta Crystallogr., Sect. C 1986,
2, 1151–1154; b) E. J. Larson, V. L. Pecoraro, J. Am. Chem.
[
[
4
[
[
3] M. W. Parker, C. C. Blake, J. Mol. Biol. 1988, 199, 649–661.
4] S. V. Antonyuk, V. V. Barynin, Crystallogr. Rep. 2000, 45, 105–
Soc. 1991, 113, 3810–3818.
[
32] K. Bertoncello, G. D. Fallon, K. S. Murray, E. R. T. Tiekink,
Inorg. Chem. 1991, 30, 3562–3568.
116.
[
5] V. V. Barynin, M. M. Whittaker, S. V. Antonyuk, V. S. Lamzin,
[
33] J. W. Gohdes, W. H. Armstrong, Inorg. Chem. 1992, 31, 368–
P. M. Harrison, P. J. Artymiuk, J. W. Whittaker, Structure 2001,
373.
9, 725–738.
[
[
6] D. P. Riley, Chem. Rev. 1999, 99, 2573–2588.
[34] a) Z. Zhang, C. Brouca-Cabarrecq, C. Hemmert, F. Dahan, J.-
P. Tuchagues, J. Chem. Soc., Dalton Trans. 1995, 1453–1460; b)
X. Xia, M. Verelst, J.-C. Daran, J.-P. Tuchagues, J. Chem. Soc.,
Chem. Commun. 1995, 2155–2157; c) N. Matsumoto, Y. Sunat-
suki, H. Miyasaka, Y. Hashimoto, D. Luneau, J.-P. Tuchagues,
Angew. Chem. Int. Ed. 1999, 38, 171–173; d) J.-P. Costes, F.
Dahan, B. Donnadieu, M.-J. Rodriguez Douton, A. Boussek-
sou, J.-P. Tuchagues, Inorg. Chem. 2004, 43, 2736–2744; e) S.
Deoghoria, S. K. Bera, B. Moulton, M. J. Zaworotko, J.-P. Tu-
chagues, G. Mostafa, T.-H. Lu, S. K. Chandra, Polyhedron
2005, 24, 343–350; f) G. Bhargavi, M. V. Rajasekharan, J.-P.
Costes, J.-P. Tuchagues, Polyhedron 2009, 28, 1253–1260; g) G.
Bhargavi, M. V. Rajasekharan, J.-P. Tuchagues, Inorg. Chim.
Acta 2009, 362, 3247–3252.
7] D. Salvemini, Z. Wang, J. Zweier, A. Samouilov, H. Macarthur,
T. Mismo, M. Currie, S. Cuzzocrea, J. Sikorski, D. Riley, Sci-
ence 1999, 286, 304–306.
[
[
[
[
8] G. F. Liu, M. Filipovic, F. W. Heinemann, I. Ivanovic-Burma-
zovic, Inorg. Chem. 2007, 46, 8825–8835.
9] A. Maroz, G. F. Kelso, R. A. J. Smith, D. C. Ware, R. F. An-
derson, J. Phys. Chem. A 2008, 112, 4929–4935.
10] A. J. Wu, J. E. Penner-Hahn, V. L. Pecoraro, Chem. Rev. 2004,
104, 903–938.
11] S. Signorella, A. Rompel, K. Buldt-Karentzopoulos, B. Krebs,
V. L. Pecoraro, J.-P. Tuchagues, Inorg. Chem. 2007, 46, 10864–
10868.
[
12] J. W. De Boer, W. R. Browne, B. L. Feringa, R. Hage, C. R.
Chim. 2007, 10, 341–354.
13] S. Signorella, J.-P. Tuchagues, D. Moreno, C. Palopoli in Inor-
ganic Biochemistry Research Progress (Eds.: J. G. Hughes, A. J.
[35] M. Maneiro, M. R. Bermejo, A. Sousa, M. Fondo, A. M.
González, A. Sousa-Pedrares, C. A. McAuliffe, Polyhedron
2000, 19, 47–54.
[
Eur. J. Inorg. Chem. 2010, 965–974
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
973

V. Daier, D. Moreno, C. Duhayon, J.-P. Tuchagues, S. Signorella
FULL PAPER
[
36] a) M. W. Lynch, D. N. Hendrickson, B. J. Fitzgerald, C. G. Pi-
erpont, J. Am. Chem. Soc. 1984, 106, 2041–2049; b) J. R. Hart-
mann, B. M. Foxman, S. R. Cooper, Inorg. Chem. 1984, 23,
J. Mascarenhas, B. Malfroy, J. Med. Chem. 2002, 45, 4549–
4558.
[53] J. A. Bonadies, M. L. Kirk, M. S. Lah, D. P. Kessissoglou,
W. E. Hatfield, V. L. Pecoraro, Inorg. Chem. 1989, 28, 2037–
2044.
[54] H. Biava, C. Palopoli, S. Shova, M. De Gaudio, V. Daier, M.
González-Sierra, J.-P. Tuchagues, S. Signorella, J. Inorg. Bio-
chem. 2006, 100, 1660–1671.
[55] D. Moreno, C. Palopoli, V. Daier, S. Shova, L. Vendier, M.
González Sierra, J.-P. Tuchagues, S. Signorella, Dalton Trans.
2006, 5156–5166.
1381–1387; c) D. T. Richens, C. G. Smith, D. T. Sawyer, Inorg.
Chem. 1979, 18, 706–712; d) K. Wieghardt, U. Bossek, D. Ven-
tur, J. Weiss, J. Chem. Soc., Chem. Commun. 1985, 347; e) M. J.
Camenzind, F. J. Hollander, C. L. Hill, Inorg. Chem. 1982, 21,
4301–4308.
[
[
[
37] K. Konig, V. P. Desai, B. Kanellakopulos, R. Klenze, Chem.
Phys. 1980, 54, 109–113.
38] D. Pursche, M. U. Triller, C. Slinn, N. Reddig, A. Rompel, B.
Krebs, Inorg. Chim. Acta 2004, 357, 1695–1702.
[56]
C. Palopoli, M. González-Sierra, G. Robles, F. Dahan, J.-P.
Tuchagues, S. Signorella, J. Chem. Soc., Dalton Trans. 2002,
39] M. Hoohenraad, K. K. Ramkisoensing, W. L. Driessen, H.
Kooijman, A. L. Spek, E. Bowman, J. G. Haasnoot, J. Reedijk,
Inorg. Chim. Acta 2001, 320, 117–126.
3813–3819.
[
57] L. Murase, S. Ueno, S. Kida, Inorg. Chim. Acta 1984, 87, 155–
[
[
[
40] J. Bonadies, M. Maroney, V. L. Pecoraro, Inorg. Chem. 1989,
157.
28, 2044–2051.
[
[
58] P. Pascal, Ann. Chim. Phys. 1910, 19, 5–70.
41] M. T. Caudle, P. Riggs-Gelasco, A. K. Gelasco, J. E. Penner-
Hahn, V. L. Pecoraro, Inorg. Chem. 1996, 35, 3577–3584.
42] M. R. Bermejo, A. M. González, M. Fondo, A. García-Deibe,
M. Maneiro, J. Sanmartín, O. Hoyos, M. Watkinson, New J.
Chem. 2000, 24, 235–241.
43] M. R. Bermejo, A. M. González-Noya, V. Abad, M. I.
Fernández, M. Maneiro, R. Pedrido, M. Vásquez, Eur. J. Inorg.
Chem. 2004, 3696–3705.
59] F. James, M. Roos, “MINUIT Program, a System for Function
Minimization and Analysis of the Parameters Errors and Corre-
lations”; Comput. Phys. Commun. 1975, 10, 343–367.
60] C. Palopoli, B. Chansou, J.-P. Tuchagues, S. Signorella, Inorg.
Chem. 2000, 39, 1458–1462.
[
[
[
[
[
[
61] C. Beauchamps, I. Fridovich, Anal. Biochem. 1971, 44, 276–
287.
62] G. F. Liu, M. Filipovic, F. W. Heinemann, I. Ivanovic-Burma-
[
44] V. Daier, H. Biava, C. Palopoli, S. Shova, J.-P. Tuchagues, S.
Signorella, J. Inorg. Biochem. 2004, 98, 1806–1817.
45] S. Durot, C. Policar, F. Cisnetti, F. Lambert, J.-P. Renault, G.
Pelosi, G. Blain, H. Korri-Youssoufi, J.-P. Mahy, Eur. J. Inorg.
Chem. 2005, 3513–3523.
zovic, Inorg. Chem. 2007, 46, 8825–8835.
63] CrysAlis RED, version 1.171, Oxford Diffraction Ltd., Oxford,
U. K., 2006.
64] A. Altomare, G. Cascarano, C. Giaccovazzo, A. Guagliardi,
M. C. Burla, G. Polidori, M. Camalli, J. Appl. Crystallogr.
[
[
[
[
[
[
[
[
46] Z. R. Liao, X. F. Zheng, B. S. Luo, L. R. Shen, D. F. Li, H. L.
1994, 27, 435.
Liu, W. Zhao, Polyhedron 2001, 20, 2813–2821.
47] E. A. Lewis, H. H. Khodr, R. C. Hilder, J. R. Smith, P. H. Wal-
ton, Dalton Trans. 2004, 187–188.
48] J. Lin, C. Tu, H. Lin, P. Jiang, J. Ding, Z. Guo, Inorg. Chem.
Commun. 2003, 6, 262–265.
49] U. P. Singh, A. K. Sharma, P. Tyagi, S. Upreti, R. K. Singh,
Polyhedron 2006, 25, 3628–3638.
[
[
65] P. W. Betteridge, J. R. Carruthers, R. I. Cooper, K. Prout, D. J.
Watkin, J. Appl. Crystallogr. 2003, 36,1487.
66] R. H. Blessing, Acta Crystallogr., Sect. A 1995, 51, 33.
[67] D. J. Watkin, C. K. Prout, L. J. Pearce, CAMERON, Chemical
Crystallography Laboratory, University of Oxford, Oxford,
UK, 1996.
[68] C. F. Macrae, I. J. Bruno, J. A. Chisholm, P. R. Edgington, P.
McCabe, E. Pidcock, L. Rodriguez-Monge, R. Taylor, J.
van de Streek, P. A. Wood, J. Appl. Crystallogr. 2008, 41, 466–
470.
50] I. Batinic-Haberle, I. Spasojevic, P. Hambright, L. Benov, A.
Crumbliss, I. Fridovich, Inorg. Chem. 1999, 38, 4011–4022.
51] A. Gelasco, S. Bensiek, V. L. Pecoraro, Inorg. Chem. 1998, 37,
3301–3309.
52] S. R. Doctrow, K. Huffman, C. Bucay Marcus, G. Tocco, E.
Malfroy, C. A. Adinolfi, H. Kruk, K. Baker, N. Lazarowych,
Received: October 21, 2009
Published Online: January 12, 2010
974
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