Reaction of a Nitrosyl Complex of Cobalt Porphyrin with Hydrogen Peroxide: Putative Formation of Peroxynitrite Intermediate

Article abstract of DOI:10.1021/acs.inorgchem.7b00491

The cobalt porphyrin complex [(Cl₄TPP)Co], 1, {Cl₄TPP = 5,10,15,20-tetrakis(4′-chlorophenyl)porphyrinate dianion} in dichloromethane solution was subjected to react with nitric oxide (NO) gas and resulted in the formation of the corr

Full text of DOI:10.1021/acs.inorgchem.7b00491

Article
pubs.acs.org/IC
Reaction of a Nitrosyl Complex of Cobalt Porphyrin with Hydrogen
Peroxide: Putative Formation of Peroxynitrite Intermediate
Soumen Saha,† Kuldeep Gogoi,† Baishakhi Mondal,† Somnath Ghosh,† Hemanta Deka,†
and Biplab Mondal*,†
†Department of Chemistry, Indian Institute of Technology Guwahati, North Guwahati, Assam 781039, India
S
* Supporting Information
ABSTRACT: The cobalt porphyrin complex [(Cl4TPP)Co], 1, {Cl4TPP =
5,10,15,20-tetrakis(4′-chlorophenyl)porphyrinate dianion} in dichlorome-
thane solution was subjected to react with nitric oxide (NO) gas and resulted
in the formation of the corresponding nitrosyl complex [(Cl4TPP)Co(NO)],
2, having {CoNO}8 description. It was characterized by spectroscopic studies
and single-crystal X-ray structure determination. It did not react with
dioxygen. However, in CH2Cl2/CH3CN solution, it reacted with H2O2 to
result in the Co-nitrito complex [(Cl4TPP)Co(NO2)], 3, with the
simultaneous release of O2. It induced ring nitration to the added phenol in
an appreciable yield. The reaction presumably proceeds through the formation
of corresponding Co-peroxynitrite intermediate.
the reaction of cobalt-nitrosyl complex with O2, which resulted
in the formation of corresponding nitrite product.11 Kim et. al
reported the reaction of a nonheme dinitrosyliron with O2 to
afford nitrate.12 In a similar reaction [Cu(NO)] species was
found to result in corresponding nitrite and O2.13 We reported
the reaction of [Cu(NO)]10 complex with H2O2 to give
copper-nitrato complex via thermal decomposition of a
presumed CuI-peroxynitrite intermediate.14 Thus, the metal
complex-mediated reaction of NO with various reduced O2
species is of immense importance for the understanding of NO
reactivity in biological systems. In addition, peroxynitrite-
mediated nitration of added phenols resembles the biologically
well-known tyrosine nitration.
INTRODUCTION
■
Nitric oxide (NO) is known to play the key roles in many
physiological processes like neurotransmission, vasodilation,
immune response, etc.1,2 It can also behave as a cytotoxic
effector and/or pathogenic mediator when produced at high
concentrations.3 It is believed that the cytotoxicity of NO is due
to the formation of secondary reactive nitrogen species (RNS)
like peroxynitrite (ONOO−) or nitrogen dioxide (NO2).3,4 The
formation of these secondary RNS may result from the
oxidation of NO in the presence of oxidants like superoxide
−
radicals (O2 ), hydrogen peroxide (H2O2), and/or transition-
metal ions.3 However, nitric oxide dioxygenases (NODs) are
known to maintain the in vivo level of NO.5,6 It is known that
the oxy-heme (i.e., iron(III)-superoxo) species of the NODs
Herein we report the synthesis and structural character-
ization of a nitrosyl complex of cobalt porphyrin [(Cl4TPP)-
Co(NO)]. In the presence of hydrogen peroxide (H2O2) the
cobalt-nitrosyl complex exhibits NOD reactivity, where the
intermediate formation of peroxynitrite is implicated.
−
react with NO to result in nitrate (NO3 ) ion, which is
biologically benign. This reaction is believed to proceed
through the formation of peroxynitrite intermediates. The
examples of discrete metal−peroxynitrite complexes are rare;
only a cobalt-peroxynitrite complex is known to be discretely
characterized.7 However, there are a number of examples where
metal-peroxynitrites are proposed to form as transient
intermediate in the reaction of metal−oxygen species with
NO. In those cases, metal-superoxo complexes of heme and
nonheme iron, cobalt, and copper were reported to react with
NO to result in metal−peroxynitrite intermediates.8,9 Apart
from those, recently the reaction of a nonheme CrIV-peroxo
complex with NO was reported to give CrIII-nitrate, whereas
CrIII-superoxo has been shown to result in corresponding CrIV-
oxo and NO2 through the formation of a presumed CrIII-
peroxynitrite intermediate.10
EXPERIMENTAL SECTION
■
General Methods. All reagents and solvents were purchased from
commercial sources and were of reagent grade. Acetonitrile was
distilled from calcium hydride. Deoxygenation of the solvent and
solutions were effected by repeated vacuum/purge cycles or bubbling
with argon for 30 min. NO gas was purified by passing through KOH
and P2O5 column. UV−visible spectra were recorded on a Agilent
Cary 8454 UV−visible spectrophotometer. Fourier transform infrared
(FT-IR) spectra were taken on a PerkinElmer spectrophotometer with
samples prepared as KBr pellets. 1H NMR spectra were obtained with
a 600 MHz Varian FT spectrometer. Chemical shifts (ppm) were
referenced either with an internal standard (Me4Si) for organic
However, a few instances involving the reaction of metal−
nitrosyl and O2 to form transient metal−peroxynitrite have
been exemplified. For instance, Clarkson and Basolo reported
Received: February 22, 2017
© XXXX American Chemical Society
A
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compounds or to the residual solvent peaks. Elemental analyses were
obtained from a PerkinElmer Series II Analyzer. Mass spectra were
recorded on a Waters, model: Q-Tof Premier instrument with
electrospray ionization (ESI) mode of ionization.
(v/v, 5:1), and the solution was cooled at −40 °C. To this cold
solution, precooled 2,4-ditertiarybutylphenol (1.03 g; 5 mmol) was
added and stirred for 5 min. To this, precooled hydrogen peroxide
(37% v/v, 400 μL) in acetonitrile was added, and the resulting mixture
was stirred for 0.5 h at −40 °C. The reaction mixture was then warmed
to room temperature and dried under reduce pressure. The solid mass
was then subjected to column chromatography using silica gel column
and hexane as solvent to obtain 2, 4-ditertiarybutyl-6-nitrophenol
(yield: ca. 50%) and complex 4 as solid (yield, ca. 70%). Elemental
The single crystal of the ligand was obtained by slow evaporation
from a CHCl3 solution, whereas the crystals of complexes 1 and 2
were grown from the respective tetrahydrofuran (THF) solutions. The
intensity data were collected using a Bruker SMART APEX-II CCD
diffractometer, equipped with a fine focus 1.75 kW sealed tube Mo Kα
radiation (λ = 0.710 73 Å) at 273(3) K, with increasing ω (width of
0.3° per frame) at a scan speed of 3 s/frame. The SMART software
was used for data acquisition. Data integration and reduction were
undertaken with SAINT and XPREP software.15 Multiscan empirical
absorption corrections were applied to the data using the program
SADABS.16 Structures were solved by direct methods using SHELXS-
2014 and refined with full-matrix least-squares on F2 using SHELXL-
2014/7.17 Structural illustrations were drawn with ORTEP-3 for
Windows.18
analyses for C14H21NO3, Calcd (%): C, 30.40; H, 4.01; N, 7.60, found
1
(%): C, 30.35; H, 4.03; N, 7.75. H NMR (600 MHz, CDCl3): δppm
,
7.40 (s, 1H), 7.11 (s, 1H), 5.22 (s, 1H), 1.44 (s, 9H), 1.32 (s, 9H). 13C
NMR (150 MHz, CDCl3): δppm, 149.7, 142.9, 136.1, 125.2, 124.8,
122.3, 35.2, 34.4, 31.6, 29.6. Mass (m/z): Calcd: 251.15, found:
250.53. Complex 4: Elemental analyses for C44H25N4OCl4Co, Calcd
(%): C, 63.95; H, 3.05; N, 6.78, found (%): C, 63.91; H, 3.07; N, 6.86.
FT-IR (in KBr): 3439, 2958, 1656, 1491, 1369, 1090, 998, 785 cm−1.
UV−visible (CH2Cl2/CH3CN): λmax, 390, 498, 621 nm.
Synthesis. Ligand, Cl4TPPH2 (5,10,15,20-Tetrakis(4′-chloro-
phenyl)porphyrin). The ligand Cl4TPPH2 was prepared by
following earlier reported general procedure of porphyrin synthesis
with slight modification. p-Chlorobenzaldehyde (2.80 g, 20 mmol) and
freshly distilled pyrrole (1.34 g, 20 mmol) were added to 37 mL of
propionic acid. After it refluxed for 2 h, the solution was cooled to
room temperature. It was then neutralized by aqueous Na2CO3. A
precipitate appeared, and it was filtered off. The crude mass was
subjected to purification using column chromatography using CH2Cl2
and hexane as solvent to afford the desired ligand as purple solid
(0.750 g, ca. 20% yield). Elemental analyses for C44H26N4Cl4. Calcd
(%): C, 70.23; H, 3.48; N, 7.45, found (%): C, 70.15; H, 3.47; N, 7.58.
FT-IR (in KBr): 3444, 2922, 1487, 1469, 1090, 1015, 966, 797, 728,
RESULTS AND DISCUSSION
■
The cobalt porphyrin complex [(Cl4TPP)Co] (1) [Cl4TPP =
(5,10,15,20-tetrakis(4′-chlorophenyl)porphyrinate dianion]
was prepared following an earlier reported procedure.19
Elemental and spectral analyses confirmed the formation of
the complex (Experimental Section and Supporting Informa-
tion). Bubbling of an excess of NO gas to the degassed
dicholoromethane solution of complex 1 resulted in the
formation of corresponding Co-nitrosyl complex [(Cl4TPP)-
Co(NO)] (2) (Scheme 1; Experimental Section). The complex
1
491 cm−1. H NMR (600 MHz, CDCl3): δppm, 8.85 (s, 8H), 8.14−
Scheme 1. Synthesis of Nitrosyl Complex
[(Cl4TPP)Co(NO)], 2
8.13(d; J, 6 Hz; 8H), 7.75−7.74 (d; J, 6 Hz; 8H). Mass (m/z): Calcd:
752.52, found: 753.08 (M+1).
Complex 1. To a mixture of ligand, Cl4TPPH2 (188 mg, 0.25
mmol) in CHCl3 (12 mL) and acetic acid (12 mL), cobalt(II) acetate
tetrahydrate (622 mg, 2.50 mmol) was added. After the solution
refluxed at 120 °C for 2 h, the precipitate that formed was filtered and
washed with methanol. The crude mass was subjected to column
chromatography using silica gel column and CHCl3:hexane (2:3, v/v)
solvent mixture to result in complex 1 as violet solid (141 mg, ∼70%
yield). Elemental analyses for C44H24N4Cl4Co, Calcd (%): C, 65.29;
H, 2.99; N, 6.92, found (%): C, 65.22; H, 2.98; N, 7.02. FT-IR (in
KBr): 1541, 1486, 1348, 1090, 1001, 795, 719, 505 cm−1. Mass (m/z):
Calcd 809.00, found: 809.05.
Complex 2. To a dry and degassed CH2Cl2 solution of complex 1
(0.8 g, 1 mmol), NO gas was bubbled for 5 min. The violet color of
the solution changed to dark red. The excess of NO gas was removed
by applying several cycles of vacuum/argon purge. The crude product
was isolated by drying under reduced pressure. The pure crystalline
complex 2 was obtained after recrystallization from THF (0.68 g yield,
ca. 80%). Elemental analyses for C44H24N5OCl4Co, Calcd (%): C,
62.96; H, 2.88; N, 8.34, found (%): C, 62.92; H, 2.85; N, 8.41. FT-IR
(in KBr): 1701, 1485, 1346, 1090, 999, 795, 714, 504 cm−1. 1H NMR
(600 MHz, CDCl3): δppm, 8.94 (s, 4H), 8.82 (s, 4H), 8.05 (d; J, 6 Hz;
8H), 7.64 (d; J, 6 Hz; 8H).
2 was isolated as solid and characterized spectroscopically as
well as by single-crystal X-ray structure determination. The
ORTEP diagram of the complex 1 is shown in Figure 1. The
crystallographic data and metric parameters are listed in the
Supporting Information. The crystal structure revealed that the
cobalt center is six-coordinated with a distorted octahedral
geometry. The four N atoms from the porphyrinate dianion
bind the metal ion to form a square plane, and two THF units
Complex 3. Complex 2 (0.418 g, 0.5 mmol) was dissolved in 20 mL
of dried and degassed CH2Cl2/CH3CN (v/v, 5:1), and the solution
was cooled at −40 °C. To this cold solution, precooled hydrogen
peroxide (37% v/v, 200 μL) was added and stirred for 0.5 h. The red
color of the solution changed to yellowish red. The solution was then
warmed to room temperature and dried under reduced pressure
(0.254 g, yield, ca. 60%). Elemental analyses for C44H24N5O2Cl4Co,
Calcd (%): C, 61.78; H, 2.83; N, 8.19, found (%): C, 61.72; H, 2.80;
N, 8.25. FT-IR (in KBr): 1637, 1485, 1390, 1321, 1270, 1090, 1063,
798, 504 cm−1. 1H NMR (600 MHz, CDCl3): δppm, 8.90 (s, 8H), 8.09
(d; J, 12 Hz; 8H), 7.73 (d; J, 12 Hz; 8H). Mass (m/z): Calcd: 854.99,
found: 856.08 (M+1).
Nitration of 2,4-Ditertiary-butylphenol. Complex 2 (0.837 g, 1
Figure 1. ORTEP diagram of complex 1 (50% thermal ellipsoid plot;
mmol) was dissolved in 20 mL of dried and degassed CH2Cl2/CH3CN
H atoms are removed for clarity).
B
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are bonded to the metal center from the axial position. The
average Co−Np bond distance was 1.989(2) Å, which is within
the range observed for hexa-coordinated Co(II)-porphyrinate-
s.20a Co−OTHF distances were found to be 2.404 Å. The
average Co−OTHF distance of 2.204 (2) Å was reported in case
of [(F28TPP)CoII(THF)2].20b In case of five coordinated
Co(II) pporphyrinate with THF as an axial ligand, this distance
was reported to be 2.206 (2) Å.20a It is to be noted that for six-
coordinated Co(III)-porphyrinates, the average Co−Np dis-
tance lies in the range of ca. 1.950 Å.20d In 1H NMR spectrum,
complex 1 in CDCl3 displayed peak broadening expected for
low-spin cobalt(II) porphyrinates (Supporting Information). In
the UV−visible spectrum, complex 2 exhibited characteristic
absorption bands at 538 nm (ε/M−1 cm−1, 3.1 × 104) and 415
nm (ε/M−1 cm−1, 2.21 × 105; Figure 2).
Figure 3. FT-IR spectrum of complex 2 in KBr.
end-on fashion resulting in a distorted square-pyramidal
geometry around the cobalt center. Notably, the Co−Np
distances in complex 2 are in the range from 1.974 (6) to
1.990 (6) Å with an average of 1.981 (6) Å. This distance is bit
larger than that reported for Co(III)-porphyrinates but in the
range of Co(II)-porphyrinates.20 The Co-NO moiety is bent
with a bond angle of 118.4°. The Co−NNO bond distance is
1.846(7) Å. The N−O distance was found to be 1.230(1) Å.
These are well within the range of those reported previously.23
The observation of bent NO is consistent with {CoNO}8
description.
Reactivity of Nitrosyl Complex with Oxygen and
Hydrogen Peroxide. The reactivity of complex 2 with
oxidants like O2 and H2O2 was explored. It was observed that
complex 2 in CH2Cl2 solution is inert toward O2. This is indeed
in accord with the earlier reported observations that five-
coordinated square pyramidal cobalt(II) nitrosyls do not react
with O2. Similar observation was reported with CoIII-nitrosyls
of 12- and 13-membered N-tetramethylated cyclam ligands as
well.24 However, in CH2Cl2/CH3CN solution complex 2 was
found to react with H2O2. Addition of H2O2 to the CH2Cl2/
CH3CN solution of complex 2 at −40 °C gave corresponding
Co-nitrito complex (3) (Scheme 2).
Figure 2. UV−visible spectra of complexes 1 (black) and 2(red)
(concentration of both the complexes is 0.007 mM) in dichloro-
methane at 298 K.
Complex 2 was silent in the X-band electron paramagnetic
resonance (EPR) spectroscopy suggesting the presence of
Co(III) center having [CoIII−NO−] or {CoNO}8 description
according to the Enemark−Feltham notation.21 In H NMR
1
spectrum, the pyrrole protons appeared as singlet at 8.94 and
8.82 ppm, and the protons from the phenyl group appeared as
doublet at 8.05 and 7.64 ppm (Supporting Information). In the
FT-IR spectrum, the NO stretching band appeared at 1701
cm−1 (Figure 3), which is consistent with the {CoNO}8
description. This frequency is slightly higher than those
reported earlier for [(TPP)Co(NO)] (1689 cm−1, in KBr)
and [(OEP)Co(NO)] (1675 cm−1, in CH2Cl2).22 In case of
cobalt porphyrin nitrosyls of the form [{T(p/m-X)PP}Co-
(NO)] [p/m-X = p-OCH3, p-CH3, m-CH3, p-H, m-OCH3, p-
OCF3, p-CF3, p-CN, etc.], the υNO band in CH2Cl2 was
reported previously to appear in the range of 1681−1695
cm−1.22 The ESI mass spectrum of complex 2 was dominated
by the peak at m/z, 809.05 assignable to [(Cl4TPP)Co]+ [calcd
m/z, 809.00]. This is attributed to the facile loss of axial NO
ligand under experimental condition.23
In the UV−visible spectrum, the characteristic absorption
bands of complex 2 at 538 and 415 nm disappeared with the
formation of new ones at 430 nm (ε/M−1 cm−1, 2.84 × 105),
546 (ε/M−1 cm−1, 3.3 × 104) and 665 nm (ε/M−1 cm−1, 4.2 ×
103), respectively (Figure 5). Spectral titration suggested that
the stoichiometric ratio of complex 2 with H2O2 is 1:1.
Complex 3 was isolated and characterized as the corresponding
CoIII-nitrito complex [(Cl4TPP)Co(NO2)] on the basis of
microanalysis and spectroscopic analyses (Experimental Section
and Supporting Information). The appearance of the signals in
1
the diamagnetic range in H NMR spectrum of complex 3 in
CDCl3 is in agreement with the existence of low-spin
cobalt(III) center in the complex. The pyrrole protons
appeared together at 8.90 ppm, whereas the phenyl protons
appeared as two doublets at 8.09 and 7.73 ppm, respectively.
The ESI mass spectrum of complex 3 displayed the molecular
ion peak (M+1) at m/z, 854.99 (calcd. 856.08; Figure 6). The
observed isotopic distribution pattern is also in good agreement
with the simulated one (Figure 6). In the FT-IR spectrum, the
stretching frequency at 1270 cm−1 is assignable to the nitrite
stretching (Supporting Information). In cases of earlier
reported cobalt porphyrin nitrites, this stretching was observed
Furthermore, complex 2 was characterized by a single-crystal
X-ray structure determination. The ORTEP diagram is shown
in Figure 4.
The crystallographic data and other metric parameters are
listed in the Supporting Information. The structure revealed
that the NO is coordinated axially to the cobalt center in an
C
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Figure 4. ORTEP diagram of complex 2 (50% thermal ellipsoid plot; H atoms and solvent molecules are not shown for clarity).
Scheme 2. Reaction of [(Cl4TPP)Co(NO)], 2, with H2O2
in the similar range.25 Comparing the other reported results of
nitrites of metal porphyrinates, it is logical to assume that
complex 3 has an N-bound nitrite.25 Even after several
attempts, we could not get the X-ray quality crystal of complex
3 for structural characterization. The formation of cobalt-nitrito
complex is supposed to be accompanied by the release of O2
(Scheme 2). The formation of O2 in the reaction was
confirmed by its detection in the gas chromatograph (GC)-
mass spectral analysis of the headspace gas of the reaction flask
and by alkaline pyrogallol test, as well. However, no attempts
Figure 6. ESI-mass spectrum of complex 3 in acetonitrile. (inset)
Experimental (a) and simulated (b) spectra in acetonitrile.
were made to quantify the amount of O2 formed in the
reaction. Note that, on the one hand, in case of aqueous
peroxynitrite chemistry, it is reported earlier that ONOOH and
Figure 5. UV−visible spectral monitoring of complex 2 (0.005 mM) (black) and after addition of H2O2 to result in complex 3 (red) at −40 °C.
D
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Scheme 3. Phenol Ring Nitration by [(Cl4TPP)Co(NO)], 2, in the Presence of H2O2
26
−
ONOO− react to result in NO2 , O2, and H+. On the other
hand, Cu-peroxynitrite complexes are also known to undergo
transformation to CuII-nitrito complexes with the release of
O2.13 Though these observations suggested the formation of
Co-peroxynitrite intermediate, no hint of it was observed in
UV−visible spectroscopic monitoring even at −80 °C.
Accession Codes
CCDC 1513973−1513974 and 1534041 contain the supple-
mentary crystallographic data for this paper. These data can be
obtained free of charge via www.ccdc.cam.ac.uk/data_request/
cif, or by emailing data_request@ccdc.cam.ac.uk, or by
contacting The Cambridge Crystallographic Data Centre, 12
Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
While we do not have direct spectroscopic evidence of
formation of Co-peroxynitrite intermediate, we sought chemical
evidence for the postulated species. When the reaction of
complex 2 with H2O2 is followed by the addition of 2,4-
ditertiarybutylphenol (DTBP), complex 3 is formed, and
unreacted DTBP is recovered. However, effective nitration
(ca. 50%) is observed when DTBP is added before the addition
of 1 equiv of H2O2 (Scheme 3). Workup of the reaction
mixture reveals the presence of corresponding CoIII-hydroxo
product [(Cl4TPP)Co(OH)], 4 (ca.70%), and 2,4-ditertiar-
ybutyl-6-nitrophenol (ca. 50%). A product from oxidative
coupled phenol is also observed though in very low yield (ca.
10%). It would be worth mentioning here that the phenol
nitration has been extensively used to provide evidence in
support of presence of metal−peroxynitrite intermediates.
In this connection, nitrosyls of copper(II) complexes with
methyl 2-(2-hydroxybenzylamino)-3-(1H-imidazol-5-yl)-
propanoate27 and bis(2-ethyl-4-methyl-imidazol-5yl)methane14
ligands were reported to react with H2O2 to result in the
corresponding nitrate products. They were also found to induce
the phenol ring nitration reaction. In both of the cases, the
involvement of the peroxynitrite intermediate was presumed.
AUTHOR INFORMATION
Corresponding Author
*E-mail: biplab@iitg.ernet.in. Phone: +91-361-258-2317. Fax:
+91-361-258-2339.
ORCID
Biplab Mondal: 0000-0002-0594-6749
Notes
The authors declare no competing financial interest.
Crystal data for Ligand Cl4TPPH2: CCDC No. 1513973. C44
H26 Cl4 N4 O3, M = 800.49, triclinic (P −1), a = 10.0674(5), b
= 13.1785(11), c = 15.4982(12) Å, α = 85.437(7)°, β =
80.873(5)°, γ = 88.471(5)°, V = 2023.5(3) Å3, Z = 2, Dc =
1.314 g cm−3, μ = 0.337 mm−1, T = 296(2) K, 7104 reflections,
4624 independent, R(F) = 0.1438 [I > 2δ(I)], R(int) = 0.1096,
wR(F2) = 0.2741 (all data), GOF = 1.014. Complex 1: CCDC
No. 1534041. C56 H48 Cl4 N4 Co O3, M = 1025.71, Monoclinic
(C 1 2/c 1), a = 24.4820(3), b = 9.5254(6), c = 24.2250(3)Å, α
= 90.000°, β = 119.561(14)°, γ = 90.000°, V = 4913.8(8)Å3, Z
= 4, Dc = 1.386 g cm−3, μ = 0.616 mm−1, T = 296(2) K, 4320
reflections, 3541 independent, R(F) = 0.0587 [I > 2δ(I)],
R(int) = 0.0471, wR(F2) = 0.1714 (all data), GOF = 0.802.
Complex 2: CCDC No. 1513974. C48 H32 Cl4 N5 Co O2, M =
911.52, Monoclinic (P 121/c1), a = 15.2052(14), b =
15.4115(12), c = 17.6398(16)Å, α = 90.000°, β =
103.442(10)°, γ = 90.000°, V = 4020.4(6)Å3, Z = 4, Dc =
1.506 g cm−3, μ = 0.742 mm−1, T = 100(2) K, 7257 reflections,
4976 independent, R(F) = 0.1321 [I > 2δ(I)], R(int) = 0.0992,
wR(F2) = 0.2466 (all data), GOF = 1.180.
■
CONCLUSION
■
In conclusion, a nitrosyl complex of cobalt porphyrin
[(Cl4TPP)Co(NO)], having {CoNO}8 description, was
synthesized and characterized structurally. It was found to be
inert toward dioxygen. However, in CH2Cl2/CH3CN solution,
the {CoNO}8 complex reacts with H2O2 to result in the
corresponding Co-nitrito complex [(Cl4TPP)Co(NO2)], with
the release of O2. The reaction presumably proceeds through
the formation of Co-peroxynitrite intermediate. Thus, the
present study demonstrates an example of the reaction of a
nitrosyl complex of metal−porphyrin with H2O2, which led to
the formation of the corresponding nitrito complex along with
the release of O2 via a presumed metal−peroxynitrite
intermediate.
ACKNOWLEDGMENTS
■
The authors would like to thank Department of Science and
Technology, India, for financial support (EMR/2014/000291);
DST-FIST for X-ray diffraction facility.
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ASSOCIATED CONTENT
■
S
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.inorg-
chem.7b00491.
Spectral analyses, crystallographic data, and metric
parameters of the complexes (PDF)
E
DOI: 10.1021/acs.inorgchem.7b00491
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
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DOI: 10.1021/acs.inorgchem.7b00491
Inorg. Chem. XXXX, XXX, XXX−XXX