Synthesis, crystal structures, and superoxide dismutase activity of two new multinuclear manganese(III)-salen-4,4′-bipyridine complexes

Article abstract of DOI:10.1016/j.ica.2018.06.018

Manganese(III)-salen complexes have been reported as superoxide dismutase mimics (mSOD) that can scavenge superoxide anion radicals. They are mononuclear complexes with a variety of salen ligands. Here, two new multinuclear manganese(III)-salen complexes

Full text of DOI:10.1016/j.ica.2018.06.018

Accepted Manuscript
Research paper
Synthesis, Crystal Structures, and Superoxide Dismutase Activity of Two New
Multinuclear Manganese(III)-Salen-4,4’-Bipyridine Complexes
Yusi Deawati, Djulia Onggo, Irma Mulyani, Iwan Hastiawan, Dikdik Kurnia,
Peter Lönnecke, Sara Schmorl, Berthold Kersting, Evamarie Hey-Hawkins
PII:
S0020-1693(18)30324-4
https://doi.org/10.1016/j.ica.2018.06.018
ICA 18310
DOI:
Reference:
To appear in:
Inorganica Chimica Acta
Received Date:
Revised Date:
Accepted Date:
1 March 2018
9 June 2018
11 June 2018
Please cite this article as: Y. Deawati, D. Onggo, I. Mulyani, I. Hastiawan, D. Kurnia, P. Lönnecke, S. Schmorl, B.
Kersting, E. Hey-Hawkins, Synthesis, Crystal Structures, and Superoxide Dismutase Activity of Two New
Multinuclear Manganese(III)-Salen-4,4’-Bipyridine Complexes, Inorganica Chimica Acta (2018), doi: https://
doi.org/10.1016/j.ica.2018.06.018
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Research Paper
Synthesis, Crystal Structures, and Superoxide Dismutase Activity of Two New
Multinuclear Manganese(III)-Salen-4,4’-Bipyridine Complexes
1
1
1
2
3
Yusi Deawati* , Djulia Onggo , Irma Mulyani Iwan Hastiawan , Dikdik Kurnia , Peter
,
4
4
4
4
Lönnecke , Sara Schmorl , Berthold Kersting , Evamarie Hey-Hawkins
1
Inorganic and Physical Chemistry Research Group, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung,
Indonesia
Physical and Inorganic Chemistry Laboratory, Faculty of Mathematics and Natural Sciences, Universitas Padjadjaran, Indonesia
Organic Chemistry Laboratory, Faculty of Mathematics and Natural Sciences, Universitas Padjadjaran, Indonesia
Institut für Anorganische Chemie, Fakultät für Chemie und Mineralogie, Universität Leipzig, Germany
2
3
4
*Corresponding author.
E-mail address: yusi.deawati@unpad.ac.id
Full postal address: Program Studi Doktor Kimia, Gedung Kimia Baru, FMIPA, Institut Teknologi Bandung,
Jl. Ganesha No. 10, Bandung, Indonesia, 40132, phone no. +6222 2502103
Manganese(III)-salen complexes have been reported as superoxide dismutase mimics (mSOD)
that can scavenge superoxide anion radicals. They are mononuclear complexes with a variety of
salen ligands. Here, two new multinuclear manganese(III)-salen complexes with 4,4’-bipyridine


(
4,4’-bpy) as bridging ligand and ClO as axial ligand or PF as counter anion, respectively,
4
6
are reported. The dimeric complex [{Mn(ClO )(salen)} (μ-4,4’-bpy)] (1) was obtained from
4
2
[
MnCl(salen)]·2H O and 4,4’-bipyridine which followed by addition of NaClO . While the
2 4
polymeric complex {[Mn(salen)(4,4’-bpy)]PF } (2) was prepared by the same procedure of 1,
6
n
followed by addition of KPF replacing NaClO . Compounds 1 and 2 were characterized by
6
4
elemental analysis, conductometry, infrared spectroscopy, electrospray-ionization mass
spectrometry, and room temperature/variable temperature magnetic susceptibility
measurements. The crystal structures of compounds 1 and 2 were determined by single crystal
X-ray crystallography. Furthermore, in indirect SOD tests using riboflavin photoreduction, the
polymeric compound 2 shows the slightly higher SOD activity with an IC of 1.6 ± 0.2 µM
5
0
than the dimeric compounds 1 with an IC of 2.0 ± 0.3 µM.
5
0
Keywords: manganese-salen-4,4’-bipyridine, dimeric, polymeric, superoxide dismutase, SOD,
mimic, riboflavin, photoreduction
use of natural SOD was not effective, caused
immunogenicity and was also rather expensive, while the
use of SOD mimics instead showed many advantages [3,
Introduction
Superoxide radical is a highly dangerous reactive
oxygen species [1]. It may cause damage to human tissues
that are often associated with various diseases, such as
rheumatoid arthritis, cancer, neurodegenerative disorder,
diabetic complication, stroke, inflammation, and
reperfusion injuries [2, 3].
Normally, the enzyme superoxide dismutase (SOD)
acts as a catalyst in the conversion of superoxide radicals
to hydrogen peroxide and oxygen [4, 5]. However, if
large amounts of superoxide radicals are present, the
amount of SOD will not be adequate; therefore, uptake of
an exogenous SOD is required. It was observed that the
6].
Several manganese(III)-salen complexes (salen =
N,N’-bis(salicylidene)-1,2-ethylenediamine) have been
reported as SOD mimics with low toxicity [7]. They were
obtained as mononuclear complexes with a variety of
salen ligands. Several monomeric manganese(III)-salen
complexes had been modified through substitution of
their salen ring, such as [Mn(OMe-salen)(OAc)],
[
Mn(OEt-salen)(OAc)], [Mn(OMe-salen)Cl], [Mn(OEt-
salen)Cl], were showed similar activity of SOD mimic to
the normal (unsubstituted) one, i.e. [Mn(salen)OAc] and

[
Mn(salen)Cl] [8, 9]. [Mn(salen)OAc] was included in the
MPMS 7XL SQUID magnetometer (Quantum Design)
over the temperature range 2–330 K at an applied
magnetic field of 1.0 Tesla.
first compounds that have activity as SOD mimics. Its
SOD mimic activity is expressed by IC of 2.7  0.1 M
5
0
through non-enzymatic indirect method of photoreduction
riboflavin-nitrobluetetrazolium SOD assay [10]. So far,
no multinuclear manganese(III)-salen reported as SOD
mimics.
Synthesis
H
salen
2
Bridging ligands such as 4,4’-bipyridine (4,4’-bpy)
facilitate the formation of dimeric or polymeric
The ligand H salen was prepared salicylaldehyde and
2
ethylenediamine in ethanol following the published
procedure [17]. A yellow solid was formed during the
manganese(III)-salen
complexes.
However,
in
[
Mn(salpn)(CH OH)(4,4’-bpy)]BPh4 (salpn
=
N,N’-
reaction (yield 80-88%). Anal. calc. for C16
(268.31): C, 71.62; H, 6.01; N, 10.44; found: C, 71.60; H,
6.05; N, 10.44 %. Conductivity (in methanol) Λ = 0 μS.
IR (KBr, cm ): ν(O-H) 3425 (m), ν(C=N) 1636 (vs), ν(C-
H N O
16 2 2
3
bis(salicylidene)-1,3-diaminopropane) [11], 4,4’-bpy does
not act as a bridging ligand, and a mononuclear complex
was obtained. With 3,3’-bpy, the polymeric complex
M
–
1
+
[
Mn(salen)(3,3’-bpy)]Tf N
(Tf N
=
bis(trifluoro
O) 1283 (s). ESI [MS]: m/z 269 [H salen+H] .
2
2
2
methanesulfonyl)amide) was obtained [12].
[
MnCl(salen)]·2H O
2
The presence of counter anions also contributes to the
structural aspects of manganese(III)-salen complexes.
With chloride or acetate anions, usually mononuclear
complexes were obtained. However, when perchlorate
The compound was prepared from manganese(II)
chloride tetrahydrate and H salen in ethanol according to
the published procedure [18]. Upon standing at room
temperature for 3 days, brown-black crystals formed.
These were isolated by filtration, washed with water and
ethanol, and dried in the air. Yield 75-90%. Anal. calc. for
2
–
–
(
ClO ) and hexafluorophosphate (PF ) anions are
4 6
involved, dimeric complexes were formed [13-16].
Here, we report the synthesis and characterization of
manganese(III)-salen multinuclear complexes containing
C
H
14ClMnN
O
(392.72): C, 48.93; H, 4.62; N, 7.13;
16
2
2
–
4
–
6
4
,4’-bpy bridging ligand and ClO axial ligand or PF
found: C, 48.36; H, 4.34; N, 7.13 %. Conductivity (in
methanol) Λ
(m), ν(C=N) 1634 (vs), ν(C-O) 1292 (s). ESI [MS]: m/z
321.9 [Mn(salen)] . Magnetic moment: μeff = 5.22 μ .
B
–
1
counter anion. This study is neded to investigate the effect
of multinuclear structural to SOD activity. The SOD
activity of the two resulting complexes was studied.
= 0.17 mS. IR (KBr, cm ): ν(O-H) 3426
M
+
[
{Mn(salen)(ClO )} (μ-4,4’-bpy)] (1)
4 2
Experimental
The complex was prepared from [MnCl(salen)]·2H O
0.39 g, 1 mmol) in methanol (20 mL) and 4,4’-bipyridine
0.31 g, 2 mmol) in methanol (20 mL) at 50 °C. During
2
Materials and Methods
(
(
Chemicals including solvents used without further
purification in the preparation and characterization of
manganese(III)-salen complexes have been purchased
from Sigma-Aldrich. Elemental analyses (C, H, N) were
carried out using a Vario EL III from elemental analyzer
the reaction, an aqueous solution of NaClO (1 g in 5 mL)
4
was added and then the solvent was reduced slowly. After
cooling to room temperature, the solution was filtered to
remove any unwanted precipitate. Upon standing at room
temperature for 3 days, brown-black crystals were
formed. These were isolated by filtration, washed with
methanol, and dried in air. Yield 70-88%. Anal. calc. for
C H Cl Mn N O (997.55): C, 50.57; H, 3.64; N, 8.42;
found: C, 50.23; H, 3.25; N, 8.45 %. Conductivity
(
3
-3
system GmbH. Conductivities of 10 M solutions in
methanol were measured on a HANNA Instruments HI
8
819W Professional ATC conductivity meter. Infrared
–1
4
2
36
2
2
6
12
spectra (400 - 4000 cm ) were recorded as KBr pellets on
PerkinElmer System 2000 FTIR spectrometer.
a
–
1
in methanol) ΛM = 0.24 mS. IR (KBr, cm ): ν(O-H)
417 (m), ν(C=N) 1621 (vs), ν(C-O) 1287 (s). ESI [MS]:
Electrospray ionization mass spectra (ESI-MS) were
obtained on a Bruker Daltonics ESQUIRE 3000Plus (ESI-
Ion Trap MSn) spectrometer. Magnetic susceptibilities at
room-temperature were measured using a Magnetic
Susceptibility Balance (MSB) from Sherwood Scientific.
+
m/z 677.0 [Mn(salen)(4,4’-bpy) +CH CN] ; 743.0
[
2
3
+
Mn (salen) (ClO )+H] . Magnetic moment: μ =6.86 μ .
2 2 4 eff B
Temperature-dependent
magnetic
susceptibility
measurements on powders were carried out using an

{
[Mn(salen)(μ-4,4’-bpy)]PF } ·1.5MeOH·0.5H O (2)
all hydrogen atoms were located on difference Fourier
maps calculated at the final stage of the structure
refinement. The isotropic displacement parameter for
H(17) and H(18) of compound 1 are fixed. The three
methanol and one water molecule are highly disordered
for symmetry reasons. The electron density of all solvent
molecules has been confirmed with the SQUEEZE
routine implemented in PLATON. The SQUEEZE
electron count revealed 63 electrons for all disordered
solvent molecules, which is in excellent agreement with
6
n
2
A similar procedure as stated above for 1 was used to
prepare this complex, using KPF (1 g in 15 mL) instead
of NaClO . Deep brown crystals were obtained; yield 65-
8
4
%
6
4
5%. Anal. calc. for C27.5H F MnN O P (679.46): C,
29 6 4 4
8.76; H, 3.78; N, 8.75; found: C, 48.21; H, 3.62; N, 8.69
. Conductivity (in methanol) Λ = 0.27 mS. IR (KBr,
M
–1
cm ): ν(O-H) 3453 (m), ν(C=N) 1602 (vs), ν(C-O) 1289
s). ESI [MS]: m/z 661 [Mn(salen)(4,4'-
(
+
bpy)(PF )·1.5MeOH·0.5H O + H] . Magnetic moment:
μ = 4.8 μ .
6
2
the above given composition (3 MeOH + 1 H O =
2
eff
B
64 electrons). Solvent hydrogen donor-acceptor bonds
(
Table 5) are illustrated in Figure 4(b). The position of
SOD-Mimic Activity Assay
oxygen bonded hydrogen atoms was deduced from
adjacent hydrogen acceptor atoms. Figures of crystal
structures were drawn using the program Diamond-3 [22].
Selected bond lengths and angles for complexes 1 and 2
are listed in Tables 2 and 4.
The SOD-mimic activity of complexes 1 and 2 were
evaluated using an indirect method of riboflavin
photoreduction, which was described previously [10, 19].
The method involves the competitive reaction between
the complex and reduced NBT (NBT = nitroblue
•–
CCDC 1579051 (1) and 1579052 (2) contain the
supplementary crystallographic data for this paper. These
data can be obtained free of charge via
https://summary.ccdc.cam.ac.uk/structure-summary-form
tetrazolium) for O2 generated by riboflavin under
illumination at room temperature (25 °C). The sample
mixture (240 µL) contained the complex (11 different
concentrations), 6 µM riboflavin (Thermo Scientific), 0.8
µM of N,N,N',N'-tetramethylethylene-diamine (TMEDA)
(
or from the Cambridge Crystallographic Data Centre, 12
Union Road, Cambridge CB2 1EZ, UK; fax: (+44)1223-
36-033; or deposit@ccdc.cam.uk).
(
Biorad) in 0.016 M phosphate buffer (pH 7.4) and 85 µM
3
NBT (Thermo Scientific). The reaction was stopped by
switching off the light after 15 min (4 fluorescence tubes,
Philips TLD/20 W, 20 cm distance) and the absorbance of
reduced NBT was measured at  560 nm with a
Multiskan Go Thermo Fischer Scientific UV/Vis double
beam spectrophotometer.
Results and Discussion
Synthesis
Compounds 1 and 2 were prepared from reaction
between [MnCl(salen)]·2H O and 4,4’-bpy to give deep
2
Crystal Data Collection and Refinement
brown solution, with further addition of a saturated
NaClO or KPF solution, respectively. The crystal of
4
6
The single crystal of 1 and 2 were obtained from
methanol. Single crystal X-ray data were collected on a
Gemini CCD diffractometer (Rigaku, Inc.) with graphite-
monochromated Mo-Kα radiation (λ = 0.71073 Å) and ω-
scan rotation in the θ range 2.412 to 30.414° (1) and
compounds 1 and 2 have the similar deep brown colours,
but 1 forms longer crystal than 2. The structures of both
complexes were obtained by single crystal XRD.
Crystal Structures
1
.884 to 32.400° (2) at 130 K. Information regarding the
crystallographic data collection and refinement
parameters of the structures are compiled in Table 1 and
Table 3, respectively. Semi-empirical absorption
correction from equivalents was applied to the data. The
structures were solved with SHELXT-2014 [20].
[{Mn(salen)(ClO )} (μ-4,4’-bipyridine)] (1)
4
2
Compound 1 crystallized in the triclinic space group
P 1 (Table 1). It is a neutral centrosymmetric
manganese(III) complex coordinated by salen, bipyridine
and the perchlorate anion in a distorted octahedral fashion
caused by the Jahn-Teller effect (Figure 1).
Disorderd solvent molecules and a minor disordered
–
6
fraction of the PF anion in 2 were refined isotropically,
whereas all other non-hydrogen atoms were refined
anisotropically by full-matrix least-squares techniques on
F with SHELXL-2016 [21]. Except disordered moieties,
The four donor atoms of the tetradentate salen ligand,
a Schiff base, occupy the equatorial plane [Mn-O
2

1
1
.874(2) and 1.876(2) Å, and Mn-N 1.978(2) and
.968(2) Å], while the axial bond lengths to an N donor
Table 2. Selected bond lengths (Å) and angles (°) in
[{Mn(salen)(ClO
)}
2
(μ-4,4’-bpy)] (1).
4
atom in 4,4’-bpy [2.296(2) Å] and an O atom of
perchlorate [2.433(2) Å] are longer (Table 2).
Mn(1)-O(1)
1.874(2)
1.876(2)
1.968(2)
1.978(2)
2.296(2)
2.433(2)
Mn(1)-O(2)
Mn(1)-N(2)
Mn(1)-N(1)
Mn(1)-N(3)
Mn(1)-O(3)
Table 1. Crystallographic data of [{Mn(salen)(ClO )} (μ-
4
2
4,4’-bpy)] (1).
Empirical formula
Formula weight
T / K
C H Cl Mn N O
42 36 2 2 6 12
997.55
130(2)
Wavelength / Å
Crystal system
Space group
Unit cell dimensions:
a / Å
0.71073
Triclinic
O(1)-Mn(1)-O(2) 94.13(9)
O(1)-Mn(1)-N(2) 172.64(9)
O(2)-Mn(1)-N(2) 91.91(9)
O(1)-Mn(1)-N(1) 92.0(1)
O(2)-Mn(1)-N(1) 173.1(1)
N(2)-Mn(1)-N(1) 81.7(1)
N(2)-Mn(1)-N(3) 94.20(9)
N(1)-Mn(1)-N(3) 98.85(9)
O(1)-Mn(1)-O(3) 88.96(8)
O(2)-Mn(1)-O(3) 83.85(8)
N(2)-Mn(1)-O(3) 87.51(9)
N(1)-Mn(1)-O(3) 93.21(9)
N(3)-Mn(1)-O(3) 167.93(8)
P 1
8.3114(4)
8.6461(5)
14.7044(9)
77.959(5)
79.477(5)
85.071(5)
1014.8(1)
1
b / Å
c / Å

°
°
°
V / Å
Z


O(1)-Mn()-N(3)
90.60(9)
3
O(2)-Mn(1)-N(3) 84.16(8)
-3
ρcalcd / Mg m
1.632
0.829
510
-1
{[Mn(salen)(μ-4,4’-bipyridine)]PF
2)
} ·1.5MeOH·0.5H O
6 n 2
Absorption coefficient / mm
F(000)
(
3
Crystal size / mm
0.3 x 0.15 x 0.02
2.412 to 30.414
10286
5493 (0.0482)
99.9
1 and 0.75023
5493 / 0 / 359
0.997
R1 = 0.0543,
wR2 = 0.0996
R1 = 0.1043,
wR2 = 0.1206
Compound 2 is ionic and crystallizes in the triclinic
space group P 1 (Table 3) with one [Mn(salen)(4,4'-
θ range for data collection / °
Reflections collected
+
–
bpy)] cation and one PF anion in the asymmetric unit
6
Independent reflections / Rint
Completeness to θ = 28.285° / %
Max. and min. transmission
Data / restraints / parameters
(
Figure 4(a)). As illustrated in Figure 4(b), the
manganese(III)-salen units are interconnected by bridging
,4’-bpy ligands forming polymeric cationic chains along
4
2
Goodness-of-fit on F
(
(
010). Disordered co-crystallized solvent molecules
Final R indices [I>2σ(I)]
3MeOH and H O) were located near a center of
2
inversion (Figure 4(c)) and could be identified with
the help of significant hydrogen donor-acceptor bonds
(Table 5). As expected, the manganese(III) ion adopts a
six-coordinated distorted octahedral coordination
geometry (Table 4). The two pyridyl rings in 4,4'-bpy are
rotated with respect to each other. The angle between the
planes of the two crystallographically different pyridyl
rings in 4,4'-bipyridine is 52.18(8)°. The four donor atoms
of the salen occupied the equatorial plane [Mn-O 1.870(2)
and 1.871(2) Å, and Mn-N 1.972(2) and 1.973(2) Å].
R indices (all data)
-
3
Largest difference in peak and hole /e·Å 0.584 and -0.880
Figure 1. ORTEP view of [{Mn(salen)(ClO )} (μ-4,4’-
4
2
bpy)] (1).

Table 3. Crystallographic data of {[Mn(salen)(μ-4,4’-
bpy)]PF } ·1.5MeOH·0.5H O (2).
6
n
2
Empirical formula
Formula weight
T / K
C27.5H F MnN O P
679.46
130(2)
29
6
4
4
Wavelength / Å
Crystal system
Space group
0.71073
Triclinic
P 1
Unit cell dimensions:
a / Å
b / Å
c / Å
8.9522(6)
11.7888(4)
15.4129(7)
105.939(3)
105.231(5)
101.932(4)
1439.3(1)
2
1.568
0.595
696
0.25 x 0.25 x 0.15
1.884 to 32.400
16890

°
°
°


(a)
(b)
3
V / Å
Z
ρcalcd / Mg m
Absorption coefficient / mm
F(000)
Crystal size / mm
-
3
-
1
3
θ range for data collection / °
Reflections collected
Independent reflections / Rint
Completeness to θ = 28.285° / % 100.0
9371 (0.0341)
Max. and min. transmission
Data / restraints / parameters
Goodness-of-fit on F
1 and 0.97458
9371 / 24 / 508
1.019
2
Final R indices [I>2σ(I)]
R1 = 0.0591,
wR2 = 0.1324
R1 = 0.0937,
wR2 = 0.1524
R indices (all data)
Largest difference in peak and 0.860 and -0.700
-
3
hole / e·Å
(
c)
Figure 4. (a) ORTEP view of the asymmetric unit of
[Mn(salen)(μ-4,4’-bpy)]PF } ·1.5MeOH·0.5H O
Table 4. Selected bond lengths (Å) and angles (°) in
[
(
Mn(salen)(μ-4,4’-bpy)]PF ·1.5MeOH
2)
·0.5H O
2
6
{
6
n
2
(
2) (H atoms and solvent molecules are
Mn(1)-O(1)
Mn(1)-O(2)
Mn(1)-N(2)
Mn(1)-N(1)
Mn(1)-N(3)
Mn(1)-N(4)
1.870(2)
1.871(2)
1.973(2)
1.972(2)
2.368(2)
2.372(2)
omitted); (b) coordination polymer along (010);
(c) solvent molecules located on (00½). The
disordered fraction is transparent for clarity.
Table 5. Hydrogen bond distances (Å) and angles (°)
in {[Mn(salen)(μ-4,4’-bpy)]PF } ·1.5MeOH ·0.5H O
6
n
2
(
2).
O(1)-Mn(1)-O(2) 93.03(7)
O(1)-Mn(1)-N(2) 174.59(8)
O(2)-Mn(1)-N(2) 92.29(8)
O(1)-Mn(1)-N(1) 92.21(8)
O(2)-Mn(1)-N(1) 174.54(8)
N(2)-Mn(1)-N(1) 82.50(8)
O(1)-Mn(1)-N(3) 91.87(7)
O(2)-Mn(1)-N(3) 91.45(7)
N(2)-Mn(1)-N(3) 87.00(8)
D-H···A
d(D-H)
0.98
d(H···A)
1.72
d(D···A)
2.650(1)
2.658(9)
2.914(9)
<(DHA)
N(1)-Mn(1)-N(3) 89.92(7)
O(1)-Mn(1)-N(4) 89.57(7)
O(2)-Mn(1)-N(4) 91.11(7)
N(1)-Mn(1)-N(4) 87.38(7)
N(2)-Mn(1)-N(4) 91.32(7)
N(3)-Mn(1)-N(4) 176.99(7)
O(3)-H(1O3) ···O(4)
O(4)-H(1O4) ···O(5)
O(5)-H(1O5) ···O(6)
156.6
171.8
148.8
0.98
1.69
0.98
2.03
Symmetry transformations used to generate equivalent atoms:
1 x,y+1,z #2 x,y-1,z
#

Magnetic Properties
Scheme 1 illustrates the exchange coupling pathways
used to model the susceptibility data for complex 1. In
this model, the exchange interaction between the
The magnetic properties of compound 1 were
investigated
by
temperature-dependent
magnetic
III
neighboring Mn ions are represented by J . The g
1/2
susceptibility measurements in the temperature range
between 2 and 330 K and an external field of B = μ H =
III
values were considered to be identical for the two Mn
ions. A reasonable fit of the experimental susceptibility
data was possible over the full range and led to J
0
1
.0 T. Figure 5 shows the experimental data and the
=
1/2
theoretical fit in the form of a µ  versus T plot. At 330
-1
-1
eff
-
0.042 cm , D = 2.38 cm and g = 2.0.
K, µ  is 6.92 µ , which is in good agreement with the
eff
B
III
presence of two high-spin Mn ions (S = 2). With
decreasing temperature, the effective magnetic moment
remains nearly constant down to 20 K. For lower
temperatures, it decreases faster to a value of µ  = 5.39
eff
Scheme 1. Magnetic exchange pathways used for
simulation of the magnetic susceptibility data for the
dinuclear subunits in [{Mn(salen)(ClO )} (μ-4,4’-bpy)]
µB at 2 K.This curve progression shows a weak
antiferromagnetic exchange interaction between the two
manganese(III) atoms. This is further corroborated by the
continuous decrease of the µ values from 6.93 µ at 330
4
2
a
(
1).
eff
B
K to 5.39 µ at 2 K.
B
Table 6. Magnetic properties of [{Mn(salen)(ClO )} (μ-
4
2
4,4’-bpy)] (1).
-1
-1
Complex
g
J [cm ]
D [cm ]
TIP
cm mol ]
3
-1
[
-5
2
2.0 J1/2 = -0.042
2.38
8.80 x 10
a
Parameters resulting from least-squares fit to be µeff data under
the spin Hamiltonian in eq. 1: J = coupling constant (H =
2JS S ), g = g value, D = zero-field splitting parameter and
−
1
2
TIP = temperature-independent paramagnetism.
SOD-mimic Activity
The mSOD activities of the three manganese(III)-salen
complexes 1, and 2 were evaluated quantitatively using
the indirect method of riboflavin photoreduction in the
presence of TMEDA. Riboflavin was reduced
photochemically in air generating superoxide anions,
which in turn reduced NBT. The results of this assay
indicated that approximately 2.0 ± 0.3 µM of compound 1
or 1.6 ± 0.2 µM of compound 2 was needed in order to
inhibit 50% of the NBT photoreduction (termed as IC ).
Figure 5. Temperature
dependence
of
µeff
(1)
for
per
[
{Mn(salen)(ClO )} (μ-4,4’-bpy)]
4
2
dinuclear unit. The solid line represents the best
theoretical fit to the spin Hamiltonian (eq. 1).
The temperature dependence of the magnetic
susceptibility was simulated using the appropriate spin
Hamiltonian (eq. 1), which includes the isotropic
Heisenberg-Dirac-vanVleck exchange(HDvV), the single-
ion zero-field splitting and the single-ion Zeeman
interaction by using a full-matrix diagonalization
approach.
50
The degree of inhibition is increased in a concentration-
dependent manner for the three compounds that allowed
plotting IC values (Table 7 and Figure 6).
50
ꢉ
ꢉ
ꢘ
ꢇ ꢇ
ꢇ ꢓ
ꢇ
ꢉ
ꢚ
ꢑ
ꢛ
ꢀ
ꢁ
ꢂꢃꢄꢅꢆꢆꢊꢋꢌ ꢎꢏꢂꢐꢆꢒꢊꢏꢋꢏꢎꢕ ꢖꢆ ꢏꢃ ꢏꢚꢆ ꢆ ꢋꢘꢛꢏꢜ
ꢈ
ꢉ
ꢍ
ꢑ
ꢑꢏꢏ
ꢗꢑ
ꢑ
ꢙ
ꢑꢔꢉ
ꢑꢔꢉꢏ
eq. 1

Conclusions
Table 7. The inhibition percentage of complexes 1 and 2
from the mSOD assay.
Two
new
multinuclear
manganese(III)-salen
Concentration
Inhibition (%)
complexes containing 4,4’-bipyridine bridging ligand and
No.
–
–
(
µM)
Complex 1
Complex 2
ClO axial ligand or PF counter anion, namely dimeric
4
6
1
2
3
4
5
6
7
8
0
1
2
3
4
6
10
20
0
0
[
{Mn(salen)(ClO )} (μ-4,4’-bpy)] (1), and polymeric
4 2
27
50
62
74
83
89
95
43
57
70
75
84
93
97
{
[Mn(salen)(μ-4,4’-bpy)]PF } (2), were prepared and
6 n
structurally characterized. Their SOD mimic activity was
determined and indicates that structural features affect
SOD activity.
Acknowledgments
These IC values are in the range of the IC of mSOD
6], which means that the superoxide anion radical
scavenging effects of the two manganese(III)-salen
complexes 1, and 2 were effectively inhibiting NBT
reduction.
5
0
50
This study was supported by a scholarship of BPPDN
013, a scholarship of Sandwich-like Program (PKPI)
015, and Doctoral Grants 2017 (No. 006/ADD/SP2H/
LT/DRPM/VIII/2017 from the Directorate Generale of
Higher Education, Republic of Indonesia. We would like
to thank Dr. Debbie S. Retnoningrum from the
Pharmaceutical Biotechnology Laboratory, School of
Pharmacy, Institut Teknologi Bandung, for support with
the SOD-like assays.
[
2
2
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Research
Paper
Synthesis
Crystal Structure of :
{Mn(salen)(ClO )} (μ-4,4’-bpy)] (1)
[
4
2
Deawati, Y.,
Onggo, D.,
Muyani, I.,
Hastiawan, I.,
Kurnia, D.,
Lonnecke, P.,
Schmorl, S.,
Kersting, B.,
Hey-Hawkins, E.
Coordination polymer along (010) of
6 n 2
{[Mn(salen)(μ-4,4’-bpy)]PF } ·1.5MeOH·0.5H O (2)

Synthesis,
Crystal
Structures,
and
Superoxide Dismutase Activity of Two
New Multinuclear Manganese(III)-Salen-
4
,4’-Bipyridine Complexes
1
1
Yusi Deawati* , Djulia Onggo , Irma
1
2
3
Mulyani Iwan Hastiawan , Dikdik Kurnia ,
,
4
4
Peter Lönnecke , Sara Schmorl , Berthold
4
4
Kersting , Evamarie Hey-Hawkins
HIGHLIGHTS:

So far, no multinuclear manganese(III)-salen reported
as SOD mimics.

Here, we report the synthesis and characterization of
manganese(III)-salen multinuclear complexes
–
4
containing 4,4’-bpy bridging ligand and ClO axial
–
ligand or PF counter anion. This study is neded to
6
investigate the effect of multinuclear structural to
SOD activity.

Two new multinuclear manganese(III)-salen
complexes containing 4,4’-bipyridine bridging ligand
–
4
–
6
and ClO axial ligand or PF counter anion, namely
dimeric [{Mn(salen)(ClO )} (μ-4,4’-bpy)] (1), and
4
2
polymeric {[Mn(salen)(μ-4,4’-bpy)]PF } (2), were
6
n
prepared and structurally characterized. Their SOD
mimic activity was determined and indicates that
structural features affect SOD activity.