Nitric oxide reactivity of a manganese(II) complex leading to nitrosation of the ligand

Article abstract of DOI:10.1016/j.ica.2014.12.040

Manganese(II) complexes, [Mn(L)(Cl)₂], 1 and [Mn(L)(H₂O)₂](ClO₄)₂, 2 {L = N¹,N²-bis((pyridine-2-yl)methyl)ethane-1,2-diamine} were prepared and characterized. In acetonitrile solution, complex 1 did not react with nitric oxide gas. However, addition of nitric oxide gas to the acetonitrile solution of complex 2 resulted in unstable Mn(II)-nitrosyl intermediate. The formation of nitrosyl intermediate was evidenced by UV-Vis, solution FT-IR, ¹H NMR spectral studies. Subsequently, Mn(II) center in the complex 2 was undergone reduction to Mn(I) with a simultaneous N-nitrosation of the ligand. The N-nitrosated ligand was isolated and characterized. It should be noted that the corresponding Cu(II) complex of the same ligand in presence of nitric oxide was not found to yield Cu(II)-nitrosyl.

Full text of DOI:10.1016/j.ica.2014.12.040

Inorganica Chimica Acta 429 (2015) 183–188
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Inorganica Chimica Acta
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Nitric oxide reactivity of a manganese(II) complex leading to nitrosation
of the ligand
⇑
Aswini Kalita, Somnath Ghosh, Biplab Mondal
Department of Chemistry, Indian Institute of Technology Guwahati, Assam 781039, India
a r t i c l e i n f o
a b s t r a c t
1
2
Article history:
Received 9 October 2014
Received in revised form 11 December 2014
Accepted 12 December 2014
Available online 14 February 2015
2 2 4 2
Manganese(II) complexes, [Mn(L)(Cl)2], 1 and [Mn(L)(H O) ](ClO ) , 2 {L = N ,N -bis((pyridine-2-
yl)methyl)ethane-1,2-diamine} were prepared and characterized. In acetonitrile solution, complex 1
did not react with nitric oxide gas. However, addition of nitric oxide gas to the acetonitrile solution of
complex 2 resulted in unstable Mn(II)-nitrosyl intermediate. The formation of nitrosyl intermediate
1
was evidenced by UV–Vis, solution FT-IR, H NMR spectral studies. Subsequently, Mn(II) center in the
complex 2 was undergone reduction to Mn(I) with a simultaneous N-nitrosation of the ligand. The N-ni-
trosated ligand was isolated and characterized. It should be noted that the corresponding Cu(II) complex
of the same ligand in presence of nitric oxide was not found to yield Cu(II)-nitrosyl.
Ó 2015 Elsevier B.V. All rights reserved.
Keywords:
Manganese(II) complex
Nitric oxide
Reduction of metal center
Ligand nitrosation
1
. Introduction
The reactions of nitric oxide (NO) with transition metal ions and
In our laboratory, we have been studying the reactivity of NO
with copper(II) complexes and found the reduction of metal ion
by NO leads to the N-nitrosation and diazotization at the secondary
and primary amine centers, respectively, of ligand frameworks
[24–28]. Interestingly, the N-nitrosation, in cases of Cu(II) com-
plexes, may not necessarily always proceed through Cu(II)-nitrosyl
formation. Depending upon the ligand denticity and geometry of
the complex, it may proceed through a deprotonation mechanism
in presence of base. For example, in case of tetradentate tripodal
ligand, the N-nitrosation takes place through a Cu(II)-nitrosyl
intermediate [25]. In case of tetradentate macrocyclic ligand, it
proceeds through a deprotonation of the N-H group [36]. This
diversity of the mechanistic pathway actually prompted us to
study the NO reactivity of Mn(II) complexes.
formation of metal-nitrosyls have long been of interest because of
their relevance and importance in biological systems [1–5]. Many
of the physiological events of NO are attributed to the formation
of nitrosyls of metalloproteins [6–8]. For instance, metal-nitrosyl
adducts are believed to play important roles in nitrosation reac-
tions of various thiols to result in S-nitrosothiols which are pro-
posed as carriers of NO equivalents in cellular systems [9–11].
On the other hand, the reduction of metal ion by NO has been
known for a long time. For example, ferriheme proteins are known
to undergo reduction to ferroheme in presence of NO through
Fe(III)-nitrosyl intermediate. In this direction, iron-nitrosyls, both
in protein and synthetic model systems have been studied exten-
For the present study,
a tetradentate N-donor ligand, L
II
1
2
sively [12–17]. The reduction of Cu centres in some proteins, such
{L = N ,N -bis((pyridine-2-yl)methyl)ethane-1,2-diamine} having
two pyridine nitrogen and two aliphatic amine nitrogen is chosen
(Fig. 1). Earlier, NO reactivity of Cu(II) complex of the same ligand
has been reported from our laboratory. So the present study will
also demonstrate the difference of reactivity towards NO while
moving from Cu(II) to Mn(II).
as cytochrome c oxidase and laccase, by NO is known for a long
time [18,19]. In recent years this has been exemplified by a number
of model copper(II) complexes [20–28].
The examples manganese-nitrosyls in organometallic, por-
phyrin and thalocyanine complexes are known; however, the
detail reactivity of manganese complexes with NO has not been
studied to that extent [29–32]. A few Mn(II)-nitrosyls are reported
recently with an aim to develop NO releasing material for photo
dynamic therapy [33,34]. Other than those, Mascharak et al.
reported the reductive nitrosylation of the metal ion in the reaction
2
. Experimental
2.1. Materials and methods
of a l-oxo bridged Mn(III) complex with NO [35].
All reagents and solvents of reagent grade were purchased from
⇑
Corresponding author. Tel.: +91 361 258 2317; fax: +91 361 258 2339.
E-mail address: biplab@iitg.ernet.in (B. Mondal).
commercial sources and used as received except specified.
Acetonitrile was distilled from calcium hydride. Deoxygenation of
http://dx.doi.org/10.1016/j.ica.2014.12.040
020-1693/Ó 2015 Elsevier B.V. All rights reserved.
0

1
84
A. Kalita et al. / Inorganica Chimica Acta 429 (2015) 183–188
H
N
N
H
N
N
Fig. 1. Ligand (L) used for the present study.
the solvent and solutions was effected by repeated vacuum/purge
cycles or bubbling with argon for 30 min. Nitric oxide gas was puri-
fied by passing it through a KOH and P O column. UV–Vis spectra
2 5
were recorded on a Perkin–Elmer LAMBDA 35 UV–Vis spectropho-
tometer. FT-IR spectra of the samples were taken on a Perkin Elmer
spectrophotometer with samples prepared either as KBr pellets or
in a KBr cell. Solution electrical conductivity was measured using a
Fig. 2. ORTEP diagram of complex 1 (50% thermal ellipsoid plot; H-atoms are
removed for clarity).
1
Systronic 305 conductivity bridge. H NMR spectra were recorded
in a 400 MHz Varian FT spectrometer. Chemical shifts (ppm) were
referenced either with an internal standard (Me
dual solvent peaks. The X-band Electron Paramagnetic Resonance
EPR) spectra were recorded on a JES-FA200 ESR spectrometer, at
4
Si) or to the resi-
(
1
100 MHz, CDCl
57.8. ESI-Mass (m+1), Calc. 243.32. Found: 243.04.
3
) dppm: 46.9, 53.1, 120.5, 120.8, 134.4, 147.5 and
(
room temperature and 77 K with microwave power, 0.998 mW;
microwave frequency, 9.14 GHz and modulation amplitude, 2.
Elemental analyses were obtained from a Perkin Elmer Series II
Analyzer. The magnetic moment of complex was measured on a
Cambridge Magnetic Balance.
Single crystals were grown by slow diffusion followed by slow
evaporation technique. The intensity data were collected using a
Bruker SMART APEX-II CCD diffractometer, equipped with a fine
2.2.2. Synthesis of complex 1
II
2 4 2
[Mn (H O) ]Cl (0.989 g, 5 mmol) was dissolved in 10 ml of
distilled methanol. To this solution, L (1.21 g, 5 mmol), dissolved
in distilled methanol was added slowly with constant stirring. The
color of the solution turned into pale-yellow. The stirring was con-
tinued for 2 h at room temperature. The volume of the solution was
then reduced to ꢂ2 ml. To this, diethyl ether (10 ml) was added to
layer on it and kept overnight in a freezer. This resulted into yellow
colored precipitate of complex 1. Yield: 1.58 g (ꢂ85%) and UV–Vis
a
focus 1.75 kW sealed tube MoK radiation (k = 0.71073 Å) at
2
73(3) K, with increasing (width of 0.3° per frame) at a scan
x
ꢁ1
ꢁ1
ꢁ1
speed of 3 s/frame. The SMART software was used for data acquisi-
tion [37]. Data integration and reduction were undertaken with
(methanol): kmax, 474 nm (
e
, 380 M cm ), 595 nm (
cm ). H NMR (400 MHz, CD OD) dppm: 1.33 (s, 4H), 2.52 (s, 4H),
.67 (s, 4H), 9.10 (s, 2H), 9.86 (s, 2H). X-band EPR (in methanol at
RT) gav = 2.025. FT-IR (KBr pellet): 3429, 3270, 3232, 2884, 1604,
e
, 201 M
-
ꢁ1
1
3
8
SAINT and XPREP software [38]. Structures were solved by direct
methods using SHELXS-97 and refined with full-matrix least squares
ꢁ1
2
1569, 1481, 1431, 1264, 1095, 1008, 775, 637 cm . lobs, 5.82 BM.
on F using SHELXL-97 [39]. Structural illustrations have been drawn
with ORTEP-3 for Windows [40].
2
.2.3. Synthesis of complex 2
Complex 1 (0.736 g, 2 mmol) was dissolved in minimum vol-
ume of acetonitrile. To this, aqueous solution of silver nitrate
0.680 g, 4 mmol; 2 ml) was added with constant stirring. The pre-
2
2
2
.2. Experimental
(
.2.1. Synthesis of L
The ligand L was reported earlier [41]. To a solution of pyridine-
-carboxaldehyde (2.14 g, 20 mmol) in 20 ml methanol, ethylene-
cipitated AgCl was removed by filtration through a frit. To the fil-
trate, aqueous solution of sodium perchlorate (20%, 2 ml) was
added dropwise and the mixture was kept in freezer for 12 h which
afforded brown precipitate of complex 2. Yield, 595 mg (ꢂ60%).
diamine (0.60 g, 10 mmol) was added into a 50 ml round bottom
flask equipped with a stirring bar. The solution was refluxed for
5
The complex 2 can also be prepared from manganese(II) per-
II
h. The resulting reddish-yellow solution was then reduced by
chlorate, hexahydrate. [Mn (H
2
6 4
O) ](ClO )
2
. It (1.81 g, 5 mmol)
NaBH (1.52 g, 40 mmol). Removal of the solvent under reduced
4
was dissolved in 10 ml of distilled acetonitrile. To this solution, L
(1.21 g, 5 mmol) was added slowly with constant stirring. The color
of the solution turned into brown. The stirring was continued for
2 h at room temperature. The volume of the solution was then
reduced to 2 ml. To this, benzene (5 ml) was added to layer on it
and kept overnight in a freezer. This resulted in brown colored pre-
cipitate of complex 2. Yield: 2.44 g (82%) and UV–Vis (acetonitrile):
pressure affords a crude mass. It was dissolved in water (50 ml)
and extracted with chloroform (50 ml ꢀ 4 portions). The organic
part was dried under reduced pressure and the reddish yellow oil
thus obtained was subjected to chromatographic purification using
a silica gel column to yield the pure ligand, L as yellow oil. Yield:
ꢁ
1
8
0%, 1.96 g. UV–Vis (acetonitrile): kmax, 241 nm (
e
, 20335 M
-
ꢁ
1
ꢁ1
1
ꢁ1
ꢁ1
ꢁ1
ꢁ1
cm ). FT-IR in KBr: 2791, 1591, 1475, 1431, 767 cm
400 MHz, CDCl ) dppm: 2.81 (s, 4H), 3.91 (s, 4H), 7.12–7.15 (t,
H), 7.30 (d, 4H) 7.60–7.64 (t, 2H), 8.52–8.53 (d, 2H). C NMR
.
H NMR
k
max, 246 nm (
e, 7108 M cm ), kmax, 296 nm (e, 8345 M cm ),
ꢁ
1
ꢁ1
ꢁ1
ꢁ1
(
2
3
kmax, 421 nm (e, 1620 M cm ), 644 nm (e, 210 M cm ).
13
X-band EPR (in acetonitrile at RT: gav = 2.021. FT-IR (KBr pellet):
H
H
H
N
H
N
N
N
N
N
CH
Stirred, 2h
3
OH
[
Mn(H
2
4
O) ]Cl
2
N
N
Mn
2
4 H O
Cl
Cl
Scheme 1. Synthesis of complex 1.

A. Kalita et al. / Inorganica Chimica Acta 429 (2015) 183–188
185
Table 1
Crystallographic data for complex 1.
Complex 1
16Mn
366.15
orthorhombic
Aba2
296(2)
0.71073
15.6763(17)
12.2746(12)
8.5407(12)
90.00
90.00
90.00
1643.4(3)
4
1.480
Formula
Mol. wt.
Crystal system
Space group
T (K)
Wavelength (Å)
a (Å)
b (Å)
C
14
H
1 4 2
N Cl
c (Å)
a
(°)
b (°)
(°)
c
3
V (Å )
Z
Density (mg mꢁ3)
Absorption coefficient (mmꢁ1)
Absorption correction
F(000)
1.126
none
748
Fig. 3. UV–Vis spectra of complex 1 (black trace), after purging NO (red trace) in
acetonitrile. (For interpretation of the references to color in this figure legend, the
reader is referred to the web version of this article.)
Total no. of reflections
1122
Reflections, I > 2
r(I)
934
Maximum 2h (°)
Ranges (h, k, l)
25.24
ꢁ18 6 h 6 17
ꢁ
ꢁ
14 6 k 6 13
10 6 l 6 5
Complete to 2h (%)
98.7
Refinement method
full-matrix least-squares on F2
2
GOF (F )
0.999
R indices [I > 2
R indices (all data)
r
(I)]
0.0354
0.1014
Table 2
Selected bond length (Å) of complex 1.
Bond length (Å)
Mn1–Cl1
Mn1–N1
Mn1–N2
N1–C1
N1–C5
N2–C6
N2––C7
C1–C2
C2–C3
C3–C4
C4–C5
C5–C6
2.471(2)
2.271(5)
2.328(4)
1.338(7)
1.339(7)
1.455(8)
1.441(9)
1.384(9)
1.37(1)
Fig. 4. UV–Vis spectrum of complex 2 (blue trace), after purging NO to complex 2
(
red trace) and gradual diminishing of peaks at 421 nm and 644 nm with time in
acetonitrile. Inset shows the spectral change in the range from 350 nm to 800 nm.
For interpretation of the references to color in this figure legend, the reader is
(
1.37(1)
1.370(9)
1.529(8)
referred to the web version of this article.)
0
2.3. Isolation of modified ligand L
Table 3
Selected bond angles (°) of complex 1.
Complex 2 (0.992 g, 2.0 mmol) was dissolved in 10 ml of dis-
tilled and degassed acetonitrile. To this solution NO gas was
purged for 1 min. After removing the excess NO by several cycles
of vacuum purge, the resulting yellowish solution was allowed to
stand at room temperature for 1 h. A light pink colored precipitate
was formed which was then separated by filtration under argon
and the filtrate was dried over vacuum. The crude mixture was
then purified by column chromatography to get pure ligand L as
Bond angle (°)
Cl1–Mn1–N1
Cl1–Mn1–N2
N1–Mn1–N2
N1–Mn1–Cl1
N2–Mn1–Cl1
Mn1–N1–C1
Mn1–N1–C5
C1–N1–C5
96.1(1)
91.3(1)
73.2(1)
96.1(1)
91.3(1)
124.3(3)
117.2(3)
118.2(4)
110.6(3)
108.3(4)
0
yellow oil and L -perchlorate as light yellow solid. Yield; L:
0
Mn1–N2–C6
Mn1–N2–C7
95 mg (30%) and L -perchlorate: 146 mg (40%). FT-IR (KBr pellet):
3
1
3
408, 2928, 1668, 1592, 1571, 1457, 1436, 1355, 1151, 1118,
ꢁ1
093, 998, 758, 614 cm . ESI-Mass (m+1), Calc. 301.1335. Found:
1
3
01.1287. H NMR (400 MHz, CDCl ) dppm: 4.19–4.21 (t, 1H), 4.56–
3
6
l
314, 3234, 2885, 1612, 1440, 1314, 1148, 1091, 930, 770,
4.58 (t, 1H), 5.00 (s, 2H), 5.05 (s, 1H), 5.14 (s, 2H), 5.82 (s, 1H), 7.81–
ꢁ1
ꢁ1
26 cm . Molar conductivity in acetonitrile,
K
M
(S cm ), 124.
7.83 (d, 1H), 7.91–7.98 (m, 3H), 8.47–8.51 (m, 3H), 8.73–8.75 (d,
+
13
,
4
5.76 BM. Mass {[MnL(ClO )] }, Calc. 396.0397. Found:
1H). C NMR (100 MHz, CDCl
3
) dppm: 46.0, 50.5, 124.9, 125.4,
obs
3
96.0361.
142.3, 145.7 and 156.1.

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A. Kalita et al. / Inorganica Chimica Acta 429 (2015) 183–188
the reaction of manganese(II) chloride, tetrahydrate with equiva-
lent amount of ligand, L in methanol solution (Scheme 1). The com-
plex was characterized by various spectroscopic methods as well as
single crystal X-ray structure determination. The ORTEP view of com-
plex 1 is shown in Fig. 2. Crystallographic data, important bond
angles and distances are listed in Tables 1–3, respectively. The crys-
tal structure reveals a distorted octahedral geometry around the
central metal ion. Four nitrogen atoms from the ligand and two
chlorine atoms are coordinated to the Mn(II) center. The Cl atoms
are coordinated in cis-geometry. The Mn-Npy and Mn-Namine
distances are 2.271 and 2.328 Å, respectively. The average Mn-Cl
distance is 2.471 Å. These are within the range of reported complex-
es. The complex 1 displays characteristic EPR signal in X-band (Sup-
porting information).
Fig. 5. FT-IR spectra of complex 2 after purging NO (green trace) and gradual decay
of the peak at 1718 cm in acetonitrile. (For interpretation of the references to
color in this figure legend, the reader is referred to the web version of this article.)
In acetonitrile solution, it shows d-d transition at 595 nm along
with intra ligand transitions at in UV-region (Supporting
information).
ꢁ
1
Addition of nitric oxide gas in dry and degassed acetonitrile
solution of complex 1 was not found to result in any change. This
has been monitored by UV–Vis spectroscopy (Fig. 3). This is per-
haps because of strong coordination of chloride ion with Mn(II).
To study further, the chloride ions in complex 1 are replaced by
water to afford complex 2. This has been done by treating the ace-
tonitrile solution of complex 1 with aqueous silver nitrate followed
by addition of saturated aqueous sodium perchlorate solution
(
Section 2). The complex 2 can also be prepared by stirring a mix-
ture of manganese(II) perchlorate, hexahydrate with equivalent
amount of ligand in acetonitrile under argon atmosphere
(
Section 2). It was characterized by spectral analyses and micro-
analysis (Section 2). In positive mode ESI mass spectrum, a peak
+
at 396.0361 was observed which corresponds to [MnL(ClO
Calculated, 396.0397). Even after several attempts, an X-ray qual-
ity single crystal of the complex has not been grown.
4
)]
(
Complex 2 in acetonitrile solution absorbs at 644 nm in the
UV–Vis spectrum (Fig. 4). Addition of NO gas into the degassed ace-
tonitrile solution of complex 2 resulted in the appearance of a new
band at 421 nm (Fig. 4). The intensity of this newly appeared band
was found to decay with time and finally diminished indicating the
unstable nature of the intermediate. The decay was found to follow
Fig. 6. X-band EPR spectra of complex 2 before (black trace) and after (blue trace)
the reaction with NO in acetonitrile at room temperature. (For interpretation of the
references to color in this figure legend, the reader is referred to the web version of
this article.)
ꢁ3 ꢁ1
a pseudo first order kinetics with a rate constant 4.3 ꢀ 10
98 K.
Addition of stoichiometric amount of NO also results in same
observation.
In solution FT-IR study, the addition of NO to the acetonitrile
s
at
2
3
. Results and discussion
The ligand was prepared using a reported protocol from the reac-
tion of ethylenediamine with two equivalent of pyridine-2-carbox-
aldehyde followed by reduction of the corresponding imine using
solution of complex 2 displayed a new strong stretching frequency
ꢁ1
at ꢂ1718 cm (Fig. 5). The intensity of this band was found to
4
NaBH (Section 2) [41]. The ligand was characterized by various
diminish with time suggesting this stretching from an unstable
intermediate. This has been assigned as the coordinated nitrosyl
spectroscopic techniques (Section 2). Complex 1 was prepared from
Fig. 7. 1H NMR spectrum of complex 2 after the reaction of NO under argon atmosphere in CD
CN.
3

A. Kalita et al. / Inorganica Chimica Acta 429 (2015) 183–188
187
O
N
N
HN
(
ClO )
N
N
4 2
NH
O
(
a)
(
b)
0
0
Fig. 8. (a) Modified ligand, L (ClO
4 2
)
. (b) ORTEP diagram of perchlorate salt of L (50% thermal ellipsoid plot; H-atoms are removed for clarity).
Table 4
Table 5
0
0
Crystallographic data for modified ligand L .
Selected bond length (Å) of L .
0
L
Bond length (Å)
Bond length (Å)
Formula
Mol. wt.
Crystal system
Space group
T (K)
Wavelength (Å)
a (Å)
b (Å)
C
14
H
18
N
6
O
10Cl
2
Cl1–O5
Cl1–O4
Cl1–O3
Cl1–O6
Cl2–O9
Cl2–O8
Cl2–O7
1.42(1)
1.40(1)
1.40(1)
1.42(2)
1.14(2)
1.36(2)
1.34(2)
Cl2–O10
C6–N2
N2–N3
N2–C7
N3–O1
C13–N5
O2–N6
1.41(2)
1.45(2)
1.41(2)
1.45(2)
1.25(2)
1.44(2)
1.19(2)
501.24
monoclinic
C2/c
296(2)
0.71073
22.837(6)
14.466(6)
13.121(4)
90.00
103.89(3)
90.00
4208(2)
8
1.582
0.375
c (Å)
a
(°)
b (°)
(°)
Table 6
Selected bond angles (°) of L .
c
0
3
V (Å )
Z
Bond angles (°)
109.5(7)
114.5(8)
105.2(8)
109.5(7)
110.6(8)
107.4(8)
114(2)
Bond angles (°)
Density (mg m–3
)
O5–Cl1–O4
O5–Cl1–O3
O5–Cl1–O6
O4–Cl1–O3
O4–Cl1–O6
O3–Cl1–O6
O9–Cl2–O8
O9–Cl2–O7
O9–Cl2–O10
O8–Cl2–O7
O8–Cl2–O10
O7–Cl2–O10
C6–N2–N3
C6–N2–C7
N3–N2–C7
N2–N3–O1
N4–C12–C11
N4–C12–C13
O2–N6–N5
N6–N5–C14
124(1)
96(1)
–
1)
Absorption coefficient (mm
Absorption correction
F(000)
Total no. of reflections
Reflections, I > 2
none
2064
1412
1119
131(1)
121(1)
108(1)
102(1)
118(2)
123(1)
109(1)
110(1)
r
(I)
Maximum 2h (°)
Ranges (h, k, l)
25.50
ꢁ27 6 h 6 26
124(1)
106(1)
92(1)
ꢁ
ꢁ
17 6 k 6 16
15 6 l 6 15
Complete to 2h (%)
98.6
Refinement method
full-matrix least-squares on F2
2
GOF (F )
0.999
R indices [I > 2
R indices (all data)
r
(I)]
0.1057
0.2977
ment of the formal oxidation states of the metal in metal nitrosyls
is difficult because of non-innocent nature of NO ligands. NO can
+
ꢁ
exist as NO , NO (radical) or NO in metal nitrosyl complexes.
The observed intermediate is diamagnetic complex of Mn(II) with
6
stretching. The EPR study of the intermediate has been done and it
was found to be silent (Fig. 6). Thus, intermediate is presumably
Mn(II)-mononitrosyl. This has been further supported from the
ESI mass spectrum of the intermediate. The peak at 327.112 corre-
sponds to Mn(II)-mononitrosyl (Supporting information). The
unstable nature of the intermediate did not allow its isolation of
further characterization. It should be noted that the correct assign-
NO having {MnNO} configuration according to Enemark–Feltham
notation. Thus, it may have Mn(I)-NO , Mn(II)-NO or Mn(III)-NO
+
ꢁ
configuration. Since the crystal structure is not available, direct
comparison of the metric parameters with other reported results
to assign the configuration is not possible. On the other hand, the
nitrosyl stretching frequency in the intermediate complex appears
ꢁ1
at ꢂ1718 cm in solution FT-IR spectroscopy. This is comparable

1
88
A. Kalita et al. / Inorganica Chimica Acta 429 (2015) 183–188
with the other reported Mn(II)-nitrosyls having Mn(I)-NO+ con-
figuration [42–47].
Appendix A. Supplementary material
The decomposition of the [Mn(II)-NO] intermediate is resulted
in the reduction of Mn(I) and NO . The reduction was confirmed
Supplementary data (the spectral data of all the compounds)
associated with this article can be found, in the online version, at
http://dx.doi.org/10.1016/j.ica.2014.12.040.
+
by the disappearance of the EPR signal of Mn(II) (Fig. 6).
1
In addition, the broad H NMR signals of the complex 2 became
sharp and well resolved after its reaction with NO (Fig. 7). This has
been attributed to the reduction of paramagnetic Mn(II) to diamag-
netic Mn(I) by NO.
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Acknowledgements
2
92.
The authors sincerely thank the Department of Science and
Technology, India for financial support; DST-FIST for X-ray diffrac-
tion facility. A.K. and S.G. would like to thank CSIR and UGC, India
for providing the scholarship.
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[