Photoinduced NO and HNO Production from Mononuclear {FeNO}6 Complex Bearing a Pendant Thiol

Article abstract of DOI:10.1021/jacs.9b13837

Light triggers the formation of HNO from a metal-nitrosyl species, facilitated by an intramolecular pendant thiol proton. Two {FeNO}⁶ complexes (the Enemark-Felthan notation), [Fe(NO)(^TMSPS2)(^TMSPS2H)] (1, ^TMSPS2H₂ = 2,2′-dimercapto-3,3′-bis(trimethylsilyl)diphenyl)phenylphosphine; H is a dissociable proton) with a pendant thiol and [Fe(NO)(^TMSPS2)(^TMSPS2CH₃)] (2) bearing a pendant thioether, are spectroscopically and structurally characterized. Both complexes are highly sensitive to visible light. Upon photolysis, complex 2 undergoes NO dissociation to yield a mononuclear Fe(III) complex, [Fe(^TMSPS2)(^TMSPS2CH₃)] (3). In contrast, the pendant SH of 1 can act as a trap for the departing NO radical upon irradiation, resulting in the formation of an intermediate A with an intramolecular [SH···ON-Fe] interaction. As suggested by computational results (density functional theory), the NO stretching frequency (ν_NO) is sensitive to the intramolecular interaction between the pendant ligand and the iron-bound NO, and a shift of ν_NO from 1833 (1) to 1823 cm^-1 (A) is observed experimentally. Subsequent photolysis of the intermediate A results in HNO production and a thiyl group that then coordinates to the Fe center for the formation of [Fe(^TMSPS2)₂] (4). In contrast with the common acid-base coupling pathway, the HNO is not voluntarily yielded from 1 but rather is generated by the photopromoted pathway. The photogenerated HNO can further react with [Mn^III(^TMSPS3)(DABCO)] (^TMSPS3H₃ = (2,2′2′′-trimercapto-3,3′,3′′-tris(trimethylsilyl)triphenylphosphine; DABCO = 1,4-diazabicyclo[2.2.2]octane) in organic media to yield anionic [Mn(NO)(^TMSPS3)]^- (5^-) with a {MnNO}⁶ electronic configuration, whereas [Mn^III(^TMSPS3)(DABCO)] reacts with NO gas for the formation of a {MnNO}⁵ species, [Mn(NO)(^TMSPS3)] (6). Effective differentiation of the formation of HNO from complex 1 with the pendant SH versus NO from 2 with the pendant SMe is achieved by the employment of [Mn^III(^TMSPS3)(DABCO)].

Full text of DOI:10.1021/jacs.9b13837

Subscriber access provided by University of Birmingham
Article
Photoinduced NO and HNO Production from
6
Mononuclear {FeNO} Complex Bearing a Pendant Thiol
Chuan-Kuei Chiang, Kai-Ti Chu, Chia-Chin Lin, Shi-Rou Xie, Yu-Chiao Liu, Serhiy Demeshko,
Gene-Hsiang Lee, Franc Meyer, Ming-Li Tsai, Ming-Hsi Chiang, and Chien-Ming Lee
J. Am. Chem. Soc., Just Accepted Manuscript • DOI: 10.1021/jacs.9b13837 • Publication Date (Web): 11 Apr 2020
Downloaded from pubs.acs.org on April 13, 2020
Just Accepted
“Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted
online prior to technical editing, formatting for publication and author proofing. The American Chemical
Society provides “Just Accepted” as a service to the research community to expedite the dissemination
of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in
full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully
peer reviewed, but should not be considered the official version of record. They are citable by the
Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore,
the “Just Accepted” Web site may not include all articles that will be published in the journal. After
a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web
site and published as an ASAP article. Note that technical editing may introduce minor changes
to the manuscript text and/or graphics which could affect content, and all legal disclaimers and
ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or
consequences arising from the use of information contained in these “Just Accepted” manuscripts.
is published by the American Chemical Society. 1155 Sixteenth Street N.W.,
Washington, DC 20036
Published by American Chemical Society. Copyright © American Chemical Society.
However, no copyright claim is made to original U.S. Government works, or works
produced by employees of any Commonwealth realm Crown government in the course
of their duties.

Page 1 of 14
Journal of the American Chemical Society
1
2
3
4
5
6
7
Photoinduced NO and HNO Production from Mononuclear {FeNO}6 Complex Bearing a
Pendant Thiol
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Chuan-Kuei Chiang,†,# Kai-Ti Chu,§,# Chia-Chin Lin,‡,# Shi-Rou Xie,† Yu-Chiao Liu,§ Serhiy
Demeshko,◊ Gene-Hsiang Lee,& Franc Meyer,◊ Ming-Li Tsai,*,‡,¶ Ming-Hsi Chiang,*,§,¶ and Chien-
Ming Lee*,†
†Department of Applied Science, National Taitung University, Taitung 950, Taiwan
§Institute of Chemistry, Academia Sinica, Taipei 115, Taiwan
‡Department of Chemistry, National Sun Yat-sen University, Kaohsiung 804, Taiwan
¶Department of Medicinal and Applied Chemistry, Kaohsiung Medical University, Kaohsiung 807, Taiwan
◊
Universität Göttingen, Institut für Anorganische Chemie, Tammannstraße 4, D-37077 Göttingen, Germany
&Instrumentation Center, National Taiwan University, Taipei 107, Taiwan
ABSTRACT: Light triggers the formation of HNO from a metal−nitrosyl species, facilitated by an intramolecular pendant thiol
proton. Two {FeNO}6 complexes (the Enemark−Felthan notation), [Fe(NO)(TMSPS2)(TMSPS2H)] (1, TMSPS2H2 = 2,2'-dimercapto-
3,3'-bis(trimethylsilyl)diphenyl)phenylphosphine;
H
is
a
dissociable proton) with
a
pendant thiol and
[Fe(NO)(TMSPS2)(TMSPS2CH3)] (2) bearing a pendant thioether, are spectroscopically and structurally characterized. Both
complexes are highly sensitive to visible light. Upon photolysis, complex 2 undergoes NO dissociation to yield a mononuclear
Fe(III) complex, [Fe(TMSPS2)(TMSPS2CH3)] (3). In contrast, the pendant SH of 1 can act as a trap for the departing NO radical
upon irradiation, resulting in the formation of an intermediate A with an intramolecular [SHON-Fe] interaction. As
suggested by computational results (DFT), the NO stretching frequency (NO) is sensitive to the intramolecular interaction
between the pendant ligand and the iron-bound NO, and a shift of NO from 1833 (1) to 1823 cm−1 (A) is observed
experimentally. Subsequent photolysis of the intermediate A results in HNO production and a thiyl group that then
coordinates to the Fe center for the formation of [Fe(TMSPS2)2] (4). In contrast to the common acid-base coupling pathway,
the HNO is not voluntarily yielded from 1 but rather generated by the photo-promoted pathway. The photogenerated HNO
can
further
react
with
[MnIII(TMSPS3)(DABCO)]
(
TMSPS3H3
=
(2,2'2''-trimercapto-3,3',3''-
tris(trimethylsilyl)triphenylphosphine; DABCO
=
1,4-diazabicyclo[2.2.2]octane) in organic media to yield anionic
[Mn(NO)(TMSPS3)]− (5−) with a {MnNO}6 electronic configuration while [MnIII(TMSPS3)(DABCO)] reacts with NO gas for the
formation of a {MnNO}5 species, [Mn(NO)(TMSPS3)] (6). Effective differentiation of the formation of HNO from the complex 1
with the pendant SH vs. NO from 2 with the pendant SMe is achieved by the employment of [MnIII(TMSPS3)(DABCO)].
INTRODUCTION
HNO in biological systems or medical applications, many
efforts have been made to prepare NO- or HNO-releasing
agents based on metal−NO compounds.10-20 The release of
NO from exogenous metal−nitrosyl sources can be
stimulated by changes in pH, solvation, heat and light.4, 21-32
In contrast to the NO-releasing chemistry from
metal−nitrosyl sources, the generation of HNO from
metal−nitroxyl species (M(HNO/NO−)) remains relatively
unexplored. It is generally proposed that reduction of the
Nitric oxide (NO) and its one-electron reduced derivative
nitroxyl (HNO/NO−) play significant roles in many
physiological processes.1-5 The target receptors of NO and
HNO/NO− often contain iron centers (heme or nonheme)
and/or sulfur ligands (thiol or thiolate), leading to the
formation of NO adducts responsible for biological
processes.3-4 For example, the formation of cyclic guanosine
monophosphate (cGMP) triggered by binding of NO to the
iron-heme center in soluble guanylate cyclase (sGC)
iron−NO complexes, {FeNO}x (x
=
6
or 7; the
Enemark−Felthan notation)33 to electron rich {FeNO}8
species is an essential step in HNO-releasing chemistry.34-48
Subsequent protonation of the Fe-bound NO species
carrying a more likely NO− character would yield the
formation of HNO.49-55 However, protonation of the {FeNO}8
represents
a
key step for neuromodulation or
vasodilation.6-7 HNO also induces a vasorelaxation response
and displays a more vasodilative effect than NO, thereby
showing a promise as a positive cardiac inotrope for heart
failure treatment.8-9 Inspired by the importance of NO and
ACS Paragon Plus Environment

Journal of the American Chemical Society
species by adventitious proton sources frequently results in
Page 2 of 14
R
Ph
the formation of corresponding {FeNO}7 species and H2.49-53
To date, two examples are reported for successful release of
HNO from metal−nitroxyl species. Reaction of phenylthiol
with [Fe(NO)4]− leads to the replacement of the NO− group
toward the formation of [Fe(SPh)2(NO)2]− and HNO.56 The
HNO species is also produced from the protonation of a
{CoNO}9 complex, [K(18-crown-6)][Co(LN4R)(NO)] (R = Ph
or PhCl) while its {CoNO}8 congener is unreactive.57-58
Generation of the HNO is monitored via HNO consumption
by a copper fluorescent probe, [MnIII(TPPS)]3− (TPPS =
meso-tetrakis(4-sulfonatophenyl)porphyrinate) or ferric
myoglobin.59-60 Beyond these studies, little is known about
the release of HNO due to stimuli other than the reduction-
exogenous protonation process and/or,61 especially, from
electronic deficient metal-NO complexes.18
1
2
3
4
5
6
7
8
S
H
P
R
Ph
(a)
R
P
ON
S
Fe
product
HS
+
Fe(CO)2(NO)2
2
+
SH
Fe
S
S
R
R
R
CO + N2O
P
TMSPS2H2
R = SiMe3
Ph
1
[Me3O][BF4]
(b)
R
Ph
(a')
9
(b')
S
S
H
Me
S
P
Me
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
3.155
3.550
R
3.322
3.675
ON
S
Fe
N
N
O
O
S
S
R
R
P
Ph
2
Herein,
we
report
a
{FeNO}6
complex
[Fe(NO)(TMSPS2)(TMSPS2H)] (1) with a pendant thiol, from
which the HNO is released upon irradiation with the
assistance of the pendant thiol-proton. The HNO formation
is
unobserved
in
the
methylated
derivative
pendant
[Fe(NO)(TMSPS2)(TMSPS2CH3)] (2) bearing
a
thioether. The short-lived HNO is characterized via a
trapping agent, [MnIII(TMSPS3)(DABCO)],62 in organic media,
and without it, the downstream product N2O is detected.
This first observation of HNO release from a {FeNO}6
species originates from the synergistic effect of the
electronic structure of the {FeNO}6 modulated by the
Figure 1. ORTEP diagrams of (a) 1 and (b) 2 showing 50%
probability ellipsoids. Calculated hydrogen atoms (except thiol
group of 1), methyl of trimethylsilyl groups and solvents in the
crystal structures are omitted for clarity.
strongly donating thiolato sulfur(s) of TMSPS3H3 or
63-65
TMSPS2H2,27,
and its pendant SH moiety.66-72
Consequences of the light-triggered process, viz.,
modulation of the Fe-nitrosyl bond strength and facilitation
of the intramolecular interaction between thiol and metal-
bonded nitrosyl, are discussed.
stretching band (SH) at ~2440 cm−1, which are consistent
with the presence of these functional groups determined by
X-ray diffraction analysis of 1. The NO band at 1829 cm−1 of
1 shifts to 1792 cm−1 for 15NO-labeled 1; the shift of 37 cm−1
upon substitution of 14NO with 15NO is close to the
calculated value based on Hooke’s law (Figure S2).
Comparison of the SH stretching frequency for 1 and the
free ligand TMSPS2H2 (2478 cm−1)73 indicates that no
intramolecular interaction like SHN, SHO, or SHS is
present in 1 (the S(4)N(1), S(4)O(1) and S(4)S(1)
distances are 3.550, 3.675 and 3.542 Å, respectively, inset
(a’) in Scheme 1). Similarly, the 1H NMR chemical shift of the
thiol group of 1 at 4.79 (d) ppm at 20 C (toluene-d8) is close
to that of TMSPS2H2 (4.82 (d) ppm in toluene-d8). The NO
signature (> 1800 cm−1) and the diagnostic 1H NMR spectra
(aromatic proton resonances at  6.70−8.00 (m) ppm) of 1
RESULTS AND DISCUSSION
Preparation and Characterization of
Treatment of Fe(CO)2(NO)2 (one equiv) with
1
and 2.
THF
a
(tetrahydrofuran) solution containing 2 equiv of the
TMSPS2H2 ligand at ambient temperature in the dark
produced
a
six-coordinate
neutral
complex
[Fe(NO)(TMSPS2)(TMSPS2H)] (1) which was isolated as a red
solid (Scheme 1a). In this reaction, the formation of two
gaseous products, CO(g) and N2O(g), was confirmed by GC
analysis (Figure S1). In solution (toluene or CH2Cl2) 1 is
stable (> 24 h) at room temperature under aerobic
conditions in the dark. Recrystallization from
CH2Cl2/hexane at −15 C in the dark gave crystals of 1
suitable for X-ray crystallography. The structure of 1 is
presented in Figure 1a and selected bond distances and
angles are given in Table S1. The Fe coordination sphere
contains two phosphine atoms in a trans configuration
(167.20(4)°), three thiolato sulfurs and one NO group that
exhibits a linear Fe−N−O geometry (177.3(3)°), giving an
overall distorted octahedral iron center. The structural data
also reveals that 1 contains a pendant thiol group which
comes from the half-deprotonated TMSPS2H− ligand and
resides above the basal plane of the Fe-S(1)-N(1) atoms.
The infrared spectrum of 1 (KBr pellet, Figure S2) shows a
support that
1 is a
diamagnetic non-heme {FeNO}6
species.63, 74-77
As shown in Scheme 1b, treatment of 1 with [Me3O][BF4]
in a CH2Cl2/CH3CN solution (5/1; v/v) in the dark produces
[Fe(NO)(TMSPS2)(TMSPS2CH3)] (2), as confirmed by various
spectroscopies and single-crystal X-ray diffraction. In the
UV−vis spectra, 1 and 2 show the same absorption features
at 480 and 630 (sh) nm (Figure S3). The IR spectrum of 2
(KBr pellet, Figure S4) exhibits NO bands at 1822 and 1830
(sh) cm−1 that shift to 1785 and 1793 (sh) cm−1 for 15NO-
labeled 2. Compared to 1, the lack of signals for a thiol group
1
(SH in the IR spectrum, Figure S5, and SH in the H NMR

NO band at 1829 cm−1 and a broad S−H
Scheme 1. Synthesis of 1 and 2
spectrum, Figure S6) in case of 2 is consistent with
ACS Paragon Plus Environment

Page 3 of 14
Journal of the American Chemical Society
methylation of the thiol group of 1 to give the thioether of these complexes in solution have shown reactivity
1
group in 2. Recrystallization of 2 from Et2O/CH3CN under
aerobic conditions in the dark afforded crystals suitable for
X-ray diffraction. Complex 2 shares a similar coordination
environment with 1 (Figure 1b). The Fe−N and N−O bond
lengths are almost the same for 1 and 2 (Fe−N = 1.644(3) Å
for 1 and 1.642(3) Å for 2; N−O = 1.153(4) Å for 1 and
1.152(3) Å for 2, Table S1), and methylation of the thiol in 1
does not affect the linear Fe−N−O arrangement (angles
177.3(3)° for 1; 176.1(3)° for 2). It is noted that the N−O
bond distances in 1 and 2 are very close to that of a NO
radical (1.15 Å).4 Analysis of the structural data of 2 reveals
that the C(34)−P(2)−Fe(1) angle of 117.11(9)° is different
from that of 1 (111.58(11)°) and that the distances CH3SN,
CH3SO and CH3SS are reduced (these distances
S(4)N(1), S(4)O(1) and S(4)S(1) are 3.155, 3.322 and
3.300 Å, respectively, inset (b’) in Scheme 1). It is also noted
that four molecules of 2 with slight deviations of bond
distances and angles are present in a unit cell (Figure S7).
These observations may explain the shoulder peak at 1830
cm−1 found in the IR spectrum of solid 2. In solution, only
one NO peak is observed (Figure S8). Meanwhile, the
shorter distance between the pendant sulfur and X atom (X
= N, O or S) of 2 may cause the shift of NO as suggested by
computational results (vide infra).
toward dioxygen at room temperature.66-68, 70 In contrast to
the above complexes, 1 displays its inertness toward O2.78
Complex 1 in CH2Cl2 or toluene solution shows good
stability in contact with O2 at room temperature in the dark.
Interestingly, upon photoirradiation with visible light ( >
400 nm, 150 W Xenon lamp) for 20 sec, FTIR spectra of 1 in
toluene at ambient temperature display a shift of the NO
stretching frequency from 1833 to 1823 cm−1 (from black to
blue traces, inset in Figure 2a), suggesting NO being
electronically perturbed. After the first 20 sec of irradiation,
subsequent photolysis results in intensity loss of the NO at
1823 cm−1 with concurrent growth of NN of N2O at 2219
cm−1 (in toluene) and a proposed {FeNO}7 species with NO
at 1774 cm−1 (from blue to red traces in Figure 2a).
Photoirradiation of 15NO-labeled 1 also exhibits similar
reactions. Shift of the NO peak from 1796 to 1786 cm−1 in
toluene occurs first, followed by decay of the new peak at
1786 cm−1 in the subsequent photolysis, along with the
concomitant formation of 15N2O at 2150 cm−1 (Figure S9).
The GC analysis of the reaction headspace exhibits a signal
(tr = 6.52 min) that is assigned to N2O (~15.0 % yield, Figure
S10). The thiol proton of 1 resonating at 4.79 (d) ppm
(toluene-d8 in the dark) shifts to 5.78 (br) ppm after 10 s
illumination (Figure S11). As it is known that metal-bound
HNO species show a large downfield shift for the HNO
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
proton and
a
low NO stretching frequency,79-82 the
(a)
formation of iron-bound HNO species upon photolysis of 1
can be ruled out. Ryan and coworkers have demonstrated
that the OH group of phenol is deshielded in 1H NMR
100
2219
90
spectrum
of
Fe(OEP)(NO)−HOPh
(OEP
=
1774
octaethylporphyrin) because of the hydrogen-bonding
interaction.55 The slight changes observed in the IR and
NMR spectra of 1 driven by visible light may be attributed
to the [SHON−Fe] interaction that is caused by a
conformational change as the distances between the sulfur
of the pendant thiol and the X atom (X = N, O or S) are
reduced. We also examined the effect of heat as a different
80
1823
70
1833
60
1
type of stimulus. UV−vis and H NMR spectra of a toluene
2300
2200
1900
1800
1700
Wavenumber (cm1)
solution of 1 show no apparent change after the solution has
been heated at 60 C for 10 min and then cooled back to 20
C in the dark. These observations imply that the ligated NO
of 1 does not undergo nucleophilic attack by the pendant
thiol with the aid of thermal energy at 60 C.
(b)
100
90
80
70
60
As shown in Figure 2a, the NO shift from 1833 to 1823
cm−1 (black to blue traces) along with partial intensity loss
of the NO peak and the absence of the FTIR signature band
of N2O imply that dissociation of NO occurs first at the
beginning of the photoreaction. Synthetic and
computational studies suggest that the energies of
corresponding M  *(NO) transitions are responsible for
1830
light sensitivity of the metal-nitrosyl species with a {MNO}6
2300
2200
1900
1800
1700
Wavenumber (cm1
)
83-84
configuration.25,
To explore the vertical electronic
transitions and related electronic structure of 1 and 2,
density functional theory (DFT) and TD-DFT computations
have been carried out and the results lend support to the
assumption that complexes 1 and 2 are good candidates for
NO photolability (vide infra). To further corroborate that a
solution of 1 undergoes partial photodissociation of NO,
tube-to-tube NO trapping experiments were performed.85
The transfer of NO from 1 to CoII(TPP) upon photolysis was
Figure 2. Spectral changes of 1 (a) and 2 (b) monitored by FTIR
spectroscopy upon irradiation with a Xe lamp ( > 400 nm, 150
W) at ambient temperature. The Inset shows an expansion of
the 1800 to 1860 cm−1 region for the first 20 sec of irradiation.
Photoreaction of 1 and 2. A handful of metal-thiolate
(metal = V, Mn, Fe, Co or Ni) complexes bearing a pendant
thiol(s) have been reported in the literature,66-72 and some
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 4 of 14
observed, resulting in the formation of the corresponding
{CoNO}8 species, Co(NO)(TPP) (TPP
5,10,15,20-
tetraphenyl-21H,23H-porphine). As shown by UV−vis and
FTIR spectra (Figure S12), the features shifted from 410,
527 nm to 414, 537 nm and the NO stretch at 1697 cm−1
indicate the conversion of CoII(TPP) into Co(NO)(TPP) in
~25 % yield.86
1
2
3
4
5
6
=
For comparison, irradiation of 2 that contains a thioether
group in the secondary coordination sphere and has a
similar electronic configuration to 1 was investigated.
Similar to 1, the Fe−NO bond in 2 is not labile in the dark
when a solution of 2 is evaporated to dryness under vacuum
or is heated at 60 C in toluene, as confirmed by UV−vis and
NMR spectroscopies. Similarly, FTIR spectra of 2 in toluene
upon visible-light irradiation at room temperature exhibit a
rapid decrease of the NO peak at 1830 cm−1 (Figure 2b).
During this transformation, however, no peak for N2O at
2219 cm−1 is detected (Figure 2b). Moreover, no IR
absorptions in the range of 2200−2300 cm−1 are observed
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 3. ORTEP diagrams of (a) 3 and (b) 4 showing 50%
probability ellipsoids. Calculated hydrogen atoms, the methyl
groups of trimethylsilyl substituents and solvents in the crystal
structures are omitted for clarity.
The reaction sequences shown in Scheme 2 might explain
these observations. Upon photolysis, 1 is converted into
three intermediates,
A
(a {FeNO}6 species with the
[SHON−Fe] interaction; NO at 1823 cm−1), NO and B (a
FeIII(TMSPS2)(TMSPS2H) species). Two of intermediates (NO
and B) are comparable with those observed during
photolysis of 2 (NO and 3). The formation of A in 1, but not
in the case of 2, may be attributed to the pendant thiol which
acts as a trap for dissociative NO activated by light. Without
further irradiation, the NO at 1823 cm−1 (A) will not decay,
indicating that reattack of NO to A does not occur. The
intermediate A is reminiscent of an adduct formed by
treatment of NO and RE−H (R = aryl; E = O, S or Se), which
then undergoes electron transfer coupled to a proton
transfer to generate HNO and a radical species.90-93 In this
case, excitations driven by light increase the electronic
density of the Fe-NO center in A, resulting in the formation
of the iron-nitrosyl species with the enhanced NO radical
character, which reacts with the pendant thiol situated that
serves as a NO trap.28, 30 Since NO (~25%) is generated upon
photolysis of 1, the alternative pathway for HNO production
may involve the reaction of NO and thiol of intermediate B
(Scheme 2d).92 After HNO production, a mononuclear
formal iron(IV) complex [FeIV(TMSPS2)2] is expected to be
generated (4, Scheme 2c/d). The ESI-MS (electrospray
ionization mass spectrometry) shows fragments in which
the m/z at 992.13 corresponds to [1−NO−H]− (Figure S16;
m/z = 992.13 calculated for [4]+). The absorption bands at
475, 670 and 865 nm upon photolysis of 1 also support the
formation of 4. As seen by the evolution of the UV−vis
spectra (Figure S17), these bands of 4 are gradually
converted into an unknown species with bands at 630 and
915 nm, leading to the difficulty of structural
characterization. In the presence of a HNO-trapping agent,
however, 4 becomes the major product (Figure S16) and
can be structurally characterized (vide infra). Then, the
generated HNO can undergo dimerization or react with NO
to form N2O (Scheme 2e/f).94-95 We also propose that a part
of HNO can react with B to yield a {FeNO}7 species (NO at
1774 cm−1; Scheme 2g).
upon photolysis of the mixture containing
adventitious proton sources like
2
and
2-
trimethylsilylphenylthiol or HBF4 (Figure S13) under the
same condition, indicating that the intramolecular
hydrogen bonding in 1 is a key step for N2O production.87-89
Based on the tube-to-tube NO trapping reaction, exposure
of 2 to visible light in solution leads to rapid release of NO
that reacts with CoII(TPP) to produce Co(NO)(TPP) in ~90
% yield.
After photolysis of 2, a mononuclear iron(III) complex,
[Fe(TMSPS2)(TMSPS2CH3)] (3) can be spectroscopically and
structurally characterized. Complex 3 can be crystallized by
diffusion of hexane into the THF/CH2Cl2 solution under
aerobic conditions at room temperature (70% yield). The
structure of 3 reveals that the Fe(III) ion is located at a
distorted octahedral site composed of two tridentate
−
ligands, fac-TMSPS22− and -TMSPS2CH3 as depicted in Figure
3a. Compared to 1 and 2, the two phosphine donors of 3 are
arranged in a cis fashion with a bite angle of 106.68(3)°. This
is consistent with previous findings that oxidation of the
trans-nickel(II) complex NiII(HPS2H)2 results in the
formation of the more stable cis-form of NiIV(HPS2)2.70 The
UV−vis spectrum of 3 displays features different from those
of 1 and 2 (Figure S14). The EPR spectrum of 3 in toluene at
100 K shows an anisotropy pattern with g values at 2.127,
2.110 and 1.998 (Figure S15), indicating a S = 1/2 low-spin
Fe(III) electronic configuration for 3 with inequivalent 31P
hyperfine coupling constants (AP1 = 17.7 G, 0.1 G, 17.8 G; AP2
= 33.6 G, 29.4 G, 33.8 G), which is consistent with the
asymmetrical Fe−P(1) and Fe−P(2) bond distances. After
addition of excess NO(g) to the solution of 3 in the dark, NO
re-coordination and regeneration of 2 in toluene is not
observed by IR and UV−vis spectroscopies. This may be
attributed to poor lability of the thioether group (chelate
effect) or a high rearrangement barrier for the cis-to-trans
configuration rearrangement of the two phosphine donors.
Computational Modeling. To further understand the
electronic and geometric properties of complexes 1 and 2,
density functional theory (DFT) calculations have been
performed. The electronic structures of 1 and 2 are best
described as diamagnetic low-spin Fe(II) (dxz2, dyz2, dxy2, dx2-
0, dz20 configuration) (Figures S18 and S19) where the dxz
y2
ACS Paragon Plus Environment

Page 5 of 14
Journal of the American Chemical Society
and dyz orbitals form highly covalent bonding interactions weaken the Fe-NO bond, leading to the dissociation of NO.
with two orthogonal NO  orbitals, respectively. The TD-
DFT calculation of 1 and 2 are also performed to explore
their excited states. As shown in Figure S20 and Table S2,
the calculated absorption spectra of 1 and 2 reasonably
agree with the experimental results and the assignments of
the major transitions mainly are from HOMO−2~HOMO to
LUMO~LUMO+1. For both 1 and 2, ligands take most of the
contribution (> 90%) in the occupied MOs. However, LUMO
and LUMO+1 only have around 10% orbital contribution
from the ligands but a major part on the Fe-NO center. In
addition, LUMO+2 and LUMO+3 have about 35~50% of the
MOs locating on the Fe-NO center. As the unoccupied MOs
correspond to the Fe-NO  and N-O  MOs, most of
the calculated electronic transitions have been assigned as
ligand-to-metal charge transfer (LMCT) transitions (Seq/Sax
 Fe-NO ) and ligand-to-ligand charge transfer
(LLNOCT) transitions (Seq/Sax  N-O /). Based on the
TD-DFT calculations (Table S2), the charge-transfer bands
(520, 543 and 649 nm for 1; 531, 558, 651 nm for 2) are the
transitions responsible for light sensitivity for 1 and 2,
respectively. Electrons can be excited from the ligands to
Fe-NO  and N-O / antibonding MOs upon visible-
light irradiation. The population of these orbitals could
1
2
3
4
5
6
7
8
These results are consistent with experimental data.
One possible pathway for the release of HNO upon
irradiation of 1 is via A having the [SHON−Fe] interaction
that causes a shift of NO from 1833 to 1823 cm−1 in toluene
(Scheme 2c). Learning from the solid-state structure of 2 as
shown in Figure S7, four molecules with the slight
deviations of bond distances and angles observed in a unit
cell provide good models to examine the correlation
between NO and the distance from the pendant S to the N or
O atoms (dSN/O). These four isomers have been investigated
by DFT to obtain their free energies and harmonic
vibrational frequencies. The free energy differences among
these isomers are within 10 kcal mol−1 (Figure S21). The
most thermodynamically stable isomers (2-iso2 and 2-iso4)
exhibit similar NO within only 8 cm−1. This result is
consistent with the observation of the IR shoulder peak of 2
in the solid state. Although the dSN/O of these isomers are
slightly deviating by 0.16 Å (max.), the NO difference
reaches up to 39 cm−1. It indicates that NO is sensitive to the
intramolecular interaction between the pendant thiol
ligand and NO. The relationship between dHN (the
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Scheme 2. Proposed pathways for photolysis of 1 and 2
R
Ph
S
N2O
+
*NO2
1/2 N2O
+
1/2 *H2O
H
P
R
P
R

S
ON
S
Fe
P
S
S
2 NO
R
R
hv
(c)
(e)
(f)
+
R
Ph
S
Fe
P
R
Ph
S
S
Ph
HNO
R
S
R
P
H
NO
*A, NO = 1823 cm-1
R
(a)
S
S
ON
Ph
(d)
Fe
P
hv
(g)
R
P
S
4
H
B
R
(b)
S
R
R
+
Ph
*{FeNO}7 species
NO at 1774 cm-1
~25% NO
Ph
S
Fe
P

1
S
S
R
R
Ph
*B
* predicted species
R
P
R
Ph
Me
S
S
P
Me
R
R
S
ON
hv
(h)
Ph
S
Fe
P
Fe
P
+
~90% NO
S
S
S
S
R
R
R
R
Ph
Ph
3
2
distance from H of the pendant thiol to the N atom of the
NO group) and NO is investigated by DFT with geometry
optimization at given bond distances. As shown in Figure
4, the fully optimized structure of 1 has the dHN around
2.7 Å. The free energy increases with the shorter dHN
accompanied with a lower NO. When dHN reaches 2.2 Å,
the NO shift is about 10 cm−1. Meanwhile, G is only
about 3.5 kcal mol−1 uphill. Although the proposed
is reflected in the NO stretching frequency. Therefore, this
complex 1HN2.2 (M = 1) is proposed to be as intermediate
A. In addition, the triplet state of 1 was investigated with
the different dHN (Figure 4). It was observed that the
singlet state has a lower energy when the dHN is long. 1
(M = 3) becomes more stable than 1 (M = 1) when dHN is
shorter than 1.8 Å. This result gives us a hint to depict the
HNO releasing pathway by the intramolecular fashion. As
shown in Scheme S1, the irradiation of 1 leads to 1HN2.2 (M
= 1). The second step is the formation of species 1-HNO
(M = 3) that is a precursor to HNO-release. It shows a HNO-
Fe adduct structure with dHN of 1.22 Å and a bent Fe-N-O
structure of
A
could not be captured as
a
thermodynamically stable species by DFT, the theoretical
results indicate that the Fe-NO interaction is very
sensitive to the orientation of the neighboring thiol, which
ACS Paragon Plus Environment

Journal of the American Chemical Society
(Figure S22). Meanwhile, the Fe-N bond increases to 1.83
Page 6 of 14
conditions. For comparison, photolysis of 2 in the
presence of [MnIII(TMSPS3)(DABCO)] in CH2Cl2 solution at
room temperature only affords 6 (NO = 1778 cm−1, Figure
5b). There is no evidence for the formation of 5−.
1
2
3
4
5
6
7
8
Å. The orbital analysis of 1-HNO (M = 3) shows that the
ligands take most of the contribution in the occupied MOs
(Figure S23). The unoccupied MOs are mainly Fe-NO 
and N-O / antibonding MOs. It is rationalized that the
continuous photo excitation could favor the HNO release.
The dissociation of HNO leads to the formation of 1’ (M =
3) with G about 34 kcal mol−1. This high energy barrier
could be overcome by the input of irradiation energy as
described above. Finally, generation of 4 (M = 3), H2O and
N2O is thermodynamically favored (G = −33.9 kcal
mol−1).
(a)
100
90
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
80
1778
1703
70
60
1832
2300
(b)
2200
1900
1800
1700
Wavenumber (cm1)
100
90
80
70
60
50
Figure 4. Calculated NO vibrational frequencies with
corresponding dHN (red circles) for 1 (M = 1). Free energy
differences are marked as blue circles for 1 (M = 1) and blue
triangles for 1 (M = 3). Geometries are fully optimized at
1778
1829
given dHN
.
2300
2200
1900
1800
1700
Wavenumber (cm1)
Photoreaction of 1 and 2 in the presence of
[MnIII(TMSPS3)(DABCO)]. The presence of N2O (~15 %) as
a product upon photolysis of 1, but not in the case of 2,
underlines the importance of the proton of the pendant
thiol. Furthermore, generation of N2O suggests that 1
could serve as a HNO-releasing agent upon photolysis. It is
shown that reaction of [MnIII(TPPS)]3− and a HNO donor
generates [Mn(NO)(TPPS)]4− in aqueous media.96-97 In this
work, we utilize neutral [MnIII(TMSPS3)(DABCO)] as a HNO
trapping agent in organic media.98 In the dark, no reaction
is observed between 1 and [MnIII(TMSPS3)(DABCO)] at
room temperature, as evidenced by IR spectroscopy. Upon
photolysis, the IR spectra as shown in Figure 5a indicate
the formation of an anionic {MnNO}6 complex
[Mn(NO)(TMSPS3)]− (5−, NO =1703 cm−1) and a neutral
{MnNO}5 complex [Mn(NO)(TMSPS3)] (6, NO = 1778 cm−1),
respectively. The lower energy NO band of 5−, which is
shifted by 75 cm−1 in CH2Cl2 solution from that of 6, is
comparable to that of [Mn(NO)(L)2]2− (a {MnNO}6 species;
LH2 = 1,2-benzenedithiol and toluene-3,4-dithiol) and
[Mn(NO)(L)2]− (a {MnNO}5 species).99 Photoirradiation of
15NO-labeled 1 in the presence of [MnIII(TMSPS3)(DABCO)]
in CH2Cl2 solution at room temperature displays similar
reactivity in which the NO peak is shifted from 1703 to
1670 cm−1 for 15NO-labeled 5− and from 1778 to 1744 cm−1
for 15NO-labeled 6, respectively (Figure S25). It is noted
that no IR bands assigned to N2O are observed in the range
of 2200−2300 cm−1 upon photolysis of the mixture
containing 1 and [MnIII(TMSPS3)(DABCO)] under the same
Figure 5. Spectral changes of the mixtures in CH2Cl2, (a) for 1
and [MnIII(TMSPS3)(DABCO)], and (b) for
2
and
[MnIII(TMSPS3)(DABCO)] monitored by FTIR spectroscopy
upon irradiation with a Xe lamp for 20 sec at ambient
temperature.
It is also noted that a cis form of the formal iron(IV)
complex [FeIV(TMSPS2)2] (4) can be isolated and
structurally characterized after photolysis of 1 with the
HNO-trapping agents. Upon photolysis of 1 without the
HNO trapping agents, formation of 4 was not observed,
presumably due to the high reactivity of HNO that
reattacks complex 4. The ORTEP diagram of 4 is presented
in Figure 3b and selected bond distances and angles are
given in Table S1. Complex 4 shares a similar coordination
sphere with 3. Two phosphine atoms of 4 are found in a
cis configuration with a bite angle of 106.08(2)°.
The 57Fe Mössbauer spectrum of 3 at 80 K shows a
quadrupole doublet characterized by an isomer shift δ =
0.23 mm s−1 and a quadrupole splitting ∆EQ = 1.65 mm s−1
with the line width Γ = 0.37 mm s−1 (ratio of line width left
(Γl) to line width right (Γr) Γl : Γr = 1.84) (Figure S26). The
asymmetric line broadening may result from
paramagnetic relaxation that is typical for iron complexes
with half-integer spins.100 In comparison, the Mössbauer
parameters of 4 (δ = 0.15 mm s−1, ∆EQ = 1.99 mm s−1 with
Γ = 0.29 mm s−1) are clearly different, and the lower
isomer shift suggests a higher iron oxidation state.
ACS Paragon Plus Environment

Page 7 of 14
Journal of the American Chemical Society
1 or 2
However, ligand non-innocence is known to play a major
role for such thiolato-ligated complexes.101 The 57Fe
dark
(a)
no reaction
1

2
3
4
5
6
7
8
9
+
Mössbauer isomer shifts of 3 and 4 are very similar to
those documented for a pair of related iron complexes
with {P2S4} donor set, [Fe(bdt)2(PMe3)2]− (δ = 0.29 mm s−1,
∆EQ = 1.67 mm s−1 at 92 K; bdt = benzene-1,2-dithiolate)
and [Fe(bdt)2(PMe3)2]0 (δ = 0.17 mm s−1, ∆EQ = 1.54 mm
s−1 at 86 K).102 These complexes were initially reported as
low-spin S = ½ iron(III) and S = 1 iron(IV) species,
respectively,103 but [Fe(bdt)2(PMe3)2]0 was later shown to
be better described as an intermediate spin ferric ion (SFe
= 3/2) antiferromagnetically coupled to a ligand π radical
(Srad = 1/2), giving the observed S = 1 ground state.102 As
shown in Figure S27, the plot of the χMT value of 3 displays
a slightly descending behavior from 0.465 cm3 mol−1 K at
300 K to 0.378 cm3 mol−1 K at 2 K. The values are close to
the spin-only value expected for a S = 1/2 system (0.375
cm3 mol−1 K), in accordance with the view of 3 as a low-
spin (S = ½) ferric complex. For 4, the χMT product at 210
K is 1.08 cm3 mol−1 K, which is very close to the spin-only
value expected for a S = 1 system (1.00 cm3 mol−1 K). The
χMT value is almost constant down to 30 K but decreases
at lower temperatures, indicating a sizable influence of
zero-field splitting (ZFS). Experimental χMT vs. T data as
well as data from variable temperature–variable field
O
N
O
N
H
N
S
1
S
N
N
N
S
hv
(b)
S
Mn
+
Mn
S
S
S
4
3
P
P
S
Mn
P
[C6H12N2H][5]
6 + DABCO
S
6
2
hv
(c)
[MnIII TMS
(
PS3)(DABCO)]
NO(g)
(d)
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
1. Li(C2H5)3BH
2. [PPN][Cl]
=
[PPN][5]
6
SiMe3
(e)
THF solution of 6 is treated with Li(C2H5)3BH (acting as a
reducing agent; 1 equiv), the UV−vis (Figure S28) and IR
spectra support that 6 undergoes one-electron reduction
to yield a monoanionic Mn−nitrosyl species, 5−. [PPN][5]
can be obtained by addition of [PPN][Cl] to the mixture.
Diffusion of diethyl ether into a THF/CH3CN solution of
[PPN][5] leads to dark-red crystals suitable for X-ray
crystallography.
Figures S29 and 6 display thermal ellipsoid plots of
[PPN][5] and 6 respectively, and selected bond distances
and angles are presented in Table S3. The geometry
around the central Mn in both [PPN][5] and 6 adopts a
distorted trigonal bipyramid in which three thiolates
locate equatorial positions and the phosphorus occupy an
axial position trans to the nitrosyl ligand. The Mn–N1
(1.6848(12) Å) and the mean Mn–SR (2.2159(4) Å) bond
distance of 6 are shorter than those of [PPN][5] (Mn–N1,
1.748(2); the mean Mn–SR, 2.3438(5) Å), showing an
electronic deficient Mn center in 6, consistent with the
observed NO stretching frequency.
(VTVH)
magnetization
measurements
were
simultaneously modelled using a fitting procedure to the
following spin Hamiltonian for an S = 1 system including
Zeeman splitting and axial zero-field splitting (parameter
D):
퐻 = 푔휇 퐵푆 + 퐷 푆2 ― 1푆(푆 + )
1
.
]
[
퐵
푧
3
The best fit values are g = 2.09 and D = +12.5 cm−1. While
4 may be formally described as an S = 1 Fe(IV) system,
ligand non-innocence similar to the situation reported for
the [Fe(bdt)2(PMe3)2]0 complex is most likely relevant.
Possible pathways for the photolysis of 1 and 2 in the
presence of [MnIII(TMSPS3)(DABCO)] are shown in Scheme
3. In the dark,
1
or
2
do not react with
[MnIII(TMSPS3)(DABCO)] at room temperature (Scheme
3a), indicating that the formation of 5− or 6 could not
follow any bimolecular attack between the NO ligands of 1
or 2 and [MnIII(TMSPS3)(DABCO)].16, 31 With the aid of light
as shown in Scheme 2, HNO and NO released from 1 can
react with [MnIII(TMSPS3)(DABCO)] to produce 5− and 6,
respectively (Scheme 3b). In the case of 2, NO is only
released upon photolysis and, in contrast to 1, only one of
nitrosylation products, 6, is generated (Scheme 3c).
Figure 6. ORTEP diagram of 6 showing 50% probability
ellipsoids. Calculated hydrogen atoms are omitted for clarity.
The magnetic properties of micro-crystalline samples of
[PPN][5] and 6 were measured under an external field of
5000 G. The χM value of [PPN][5] gradually increases from
4.361 × 10–3 cm3 mol–1 at 300 K to 0.147 cm3 mol–1 at 2 K
(Figure S30). The corresponding χMT value between 300 K
and 2 K decreases from 1.308 to 0.439 cm3 mol–1 K. The
value of 300 K suggests a ST = 1 system for [PPN][5].99, 104
The χM value of 6 gradually increases from 1.529 × 10–3
cm3 mol–1 of 300 K to 0.094 cm3 mol–1 of 2 K (Figure S30).
The corresponding χMT value between 300 K and 2 K
decreases from 0.459 to 0.379 cm3 mol–1 K. The value of
300 K suggests a ST = 1/2 system for 6.99 The resulting spin
ground state for both species originates from the strong
antiferromagnetic coupling between the Mn center and
To further uncover structural parameters of 5− and 6,
NO(g) is utilized to serve as a NO donor (Scheme 3d). Upon
bubbling of NO(g) into the toluene solution of
[MnIII(TMSPS3)(DABCO)], a pronounced color change from
red to dark-purple occurs. The IR spectrum (NO = 1778
cm−1 in toluene) and an X-ray diffraction study confirm the
formation of neutral [Mn(NO)(TMSPS3)] (6). This
observation is consistent with photolysis of 2 in the
presence of [MnIII(TMSPS3)(DABCO)]. As shown in Scheme
3e, when a
Scheme 3. Proposed pathways for photolysis of 1 and
2 in the presence of [MnIII(TMSPS3)(DABCO)]
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 8 of 14
HDMS. Analyses of carbon, hydrogen, and nitrogen were
obtained on an elementary Vario EL cube analyzer.
NO group. Based on these observations, the electronic
structures are best described as {MnNO}6 for [PPN][5] and
{MnNO}5 for 6.
1
2
3
4
5
6
7
8
Preparation of [FeNO(TMSPS2)(TMSPS2H)] (1). A THF solution
of Fe(CO)2(NO)2, freshly prepared from the reaction of [Na-15-
crown-5][Fe(CO)3(NO)] (0.0780 g, 0.20 mmol) and [NO][BF4]
(0.0260 g, 0.22 mmol) at 0 °C, was transferred by the trap-to-trap
distillation to a flask loaded with a THF solution of TMSPS2H2
ligand (0.1880 g, 0.40 mmol). After the mixture was warmed up
and stirred for 3 h in the dark (covered in aluminum foil) at
ambient temperature, the volatile materials were removed under
vacuum. The remaining dark-red solid was washed twice with 20
mL hexane and then dried under vacuum to give
[FeNO(TMSPS2)(TMSPS2H)] (1). Diffusion of hexane into a CH2Cl2
solution of 1 at 15 °C for four weeks led to dark red crystals
suitable for X-ray crystallography (1, 0.1020 g, 50 %). IR (KBr,
pellet): νSH = 2440(w) cm−1, νNO = 1829(vs) cm−1. 1H NMR (CD2Cl2,
20 C): δ = 7.95 (t, J = 8Hz, 2H), 7.667.60 (m, 3H), 7.547.48 (m,
4H), 7.457.42 (m, 3H), 7.37 (t, J = 8Hz, 1H), 7.317.24 (m, 3H),
7.15 (t, J = 8Hz, 1H), 7.046.85 (m, 5H), 4.40 (d, J = 4Hz, 1H), 0.40
(s, 9H), 0.30 (s, 9H), 0.10 (s, 9H), 0.15 (s, 9H). 13C NMR (CD2Cl2,
20 C): δ = 144.6, 142.0, 140.4, 139.7, 138.1, 137.9, 137.5, 135.5,
135.4, 134.4, 134.2, 133.5, 133.1, 132.9, 132.8, 132.7, 132.0,
131.8, 131.5, 131.3, 130.9, 130.6, 130.1, 129.6, 129.3, 129.2,
129.0, 128.9, 126.1, 122.8, 122.7, 122.4, 0.04, 0.29, 0.62,
1.14. UVvis (toluene): λmax (ε) = 480 nm (1810), 630 nm (755).
ESI MS calcd for [1+H]+, m/z = 1024.15. Found: m/z = 1024.00.
Anal. calcd for C48H59FeNOP2S4Si4: C, 56.28; H, 5.81; N, 1.37.
Found: C, 56.77; H, 5.69; N, 1.29.
CONCLUSION
We report two light-sensitive {FeNO}6 complexes,
[Fe(NO)(TMSPS2)(TMSPS2H)] (1) with a pendant thiol and
[Fe(NO)(TMSPS2)(TMSPS2CH3)] (2) bearing
a pendant
thioether. Both complexes are inert in the dark albeit 1
simultaneously possesses a NO group and a proton donor,
which appears to be a favorable situation for HNO
formation. Electronic modulation of the Fe-NO center by
light irradiation for both complexes results in the
generation of NO radicals. The substituent in the
secondary coordination sphere plays a significant role in
dictating the fate of the photo-promoted NO. The pendant
thiol of 1 situated above the iron-bound NO serves as a NO
trap via an intramolecular [SHON−Fe] interaction,
facilitating the release of HNO and a thiyl group that
ligates to the Fe center for the formation of [Fe(TMSPS2)2]
(4) upon subsequent irradiation. Complex 2 bearing the
methyl group in the secondary coordination sphere,
instead, undergoes direct NO dissociation to yield
[Fe(TMSPS2)(TMSPS2CH3)] (3). The presence of exogenous
protons does not assist the HNO production. HNO
trapping in organic media is achieved by the neutral
complex [MnIII(TMSPS3)(DABCO)], leading to the formation
of the nitrosylation product, [Mn(NO)(TMSPS3)]− (5−) with
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Preparation of [Fe15NO(TMSPS2)(TMSPS2H)] (15NO-1). A THF
solution of [Na-15-crown-5][Fe(CO)3(15NO)] (0.1570 g, 0.40
mmol) was added to a flask containing solids [Cp2Fe][BF4]
(0.1100 g, 0.40 mmol) at 0 °C. The reaction mixture was stirred
for 10 min and purified by trap-to-trap distillation to obtain
a
{MnNO}6
electronic
configuration.
[MnIII(TMSPS3)(DABCO)] is capable of trapping the NO for
the production of {MnNO}5 [Mn(NO)(TMSPS3)] (6). The
employment of the specific Mn complex allows us to
effectively discriminate the reactions generating NO and
HNO species. In the case of 2 with a pendant thioether,
upon photolysis only the nitrosylated species 6 is formed
in the presence of [MnIII(TMSPS3)(DABCO)]. The results
reveal the important roles of the photo-excitation and the
intramolecular pendant thiol proton in the HNO
production. This is also a rare example for the HNO release
from an electronic deficient {MNO} core. Further studies
to examine the redox chemistry of 1 relative to the HNO
production are ongoing.
Fe(CO)2(15NO)2, IR (THF): νCO = 2087(s), 2034(vs) cm−1, νNO
=
1772(s), 1726(vs) cm−1 and Fe(CO)5, IR (THF): νCO = 2020(s),
1995(vs) cm−1. The mixture containing Fe(CO)2(15NO)2 and
Fe(CO)5 were then transferred to a flask loaded with a THF
solution of TMSPS2H2 ligand (0.1880 g, 0.40 mmol) by a cannula
under positive N2 pressure at room temperature. After the
mixture was stirred for 3 h in the dark, the volatile materials
were distillated by the trap-to-trap method to obtain unreacted
Fe(CO)5 confirmed by IR spectroscopy. The remaining dark-red
solid was washed twice with 20 mL hexane and then dried under
vacuum to give [Fe15NO(TMSPS2)(TMSPS2H)]. Diffusion of hexane
into a CH2Cl2 solution of 15NO-1 at 15 °C for four weeks led to
dark red crystals (15NO-1, 0.061 g, 30 %). IR (KBr, pellet): νSH
2440(w) cm−1, νNO = 1792(vs) cm−1
Preparation of [FeNO(TMSPS2)(TMSPS2CH3)] (2).
=
.
EXPERIMENTAL SECTION
A
CH3CN
Manipulations and reactions were conducted under a pure
nitrogen atmosphere according to Schlenk techniques or in a
glovebox (nitrogen atmosphere). Solvents were purified and
distillated under nitrogen by utilized appropriate reagents (CaH2
for diethyl ether, methylene chloride and toluene; CaH2 followed
by P2O5 for acetonitrile; sodium(s) with benzophenone for
hexane and tetrahydrofuran) and stored in dried, N2-filled flasks
over 4 Å molecular sieves. The reagents Na15NO2 (98 atom % 15N)
and CoII(TPP), 85%) purchased from Sigma-Aldrich were used as
received. Nitric oxide gas (10% NO + 90% N2) was purified by
passing through a column of Ascarite (8-20 mesh) purchased
from Sigma. TMSPS2H2 and [Na-15-crown-5][Fe(CO)3(NO)] were
solution (1.0 mL) containing [Me3O][BF4] (0.0080 g, 0.05 mmol)
was added dropwise to the CH2Cl2 solution of 1 (0.0520 g, 0.05
mmol) at 0 C under a N2 atmosphere. After the mixture was
stirred for 10 min in the dark, the reaction mixture was dried
under vacuum to give brown-red solid. The brown-red solid was
washed twice with 10 mL of CH3CN and dried under vacuum to
produce red solid [FeNO(TMSPS2)(TMSPS2CH3)] (2, 0.0350 g, 70
%). Vaporization of solvents from diethyl ether/CH3CN (1:1, v/v)
solution of 2 in an open vial (aerobic condition) at room
temperature for one day led to dark red crystals suitable for X-
ray crystallography. IR (KBr, pellet): νNO = 1830(sh), 1822(s)
cm−1; νNO = 1793(sh), 1785(s) cm−1 for 15NO-2. 1H NMR (400 MHz,
CD2Cl2, 20 C): δ = 7.99 (t, J = 8Hz, 2H), 7.707.65 (m, 3H),
7.567.42 (m, 7H), 7.33 (t, J = 8Hz, 1H), 7.297.18 (m, 4H),
7.066.98 (m, 2H), 6.946.85 (m, 3H) 1.60 (s, 3H), 0.46 (s, 9H),
0.28 (s, 9H), 0.08 (s, 9H), 0.22 (s, 9H). 13C NMR (CD2Cl2, 20 C):
δ = 152.0, 150.5, 147.5, 141.6, 141.2, 140.4, 139.5, 138.1, 137.3,
136.1, 135.3, 135.2, 134.6, 132.9, 132.7, 132.6, 132.0, 131.9,
131.6, 131.1, 130.9, 130.0, 129.8, 129.3, 128.9, 128.8, 128.3,
128.2, 122.7, 122.6, 122.5, 122.0, 121.9, 22.62, 0.96, 0.16, 0.57,
1.11. UVvis (toluene): λmax (ε) = 480 nm (1760), 630 nm (705).
synthesized and characterized according to published
105
procedures.73,
Infrared spectra (IR) were recorded on FTIR
(PerkinElmer, Frontier) with sealed solution cells (0.1 mm, CaF2
windows). UVvis spectra were recorded on a SCINCO S-4100 or
on Agilent 8454 spectrophotometer equipped with an UNICOKU
liquid N2 cryostat. NMR spectra were obtained on Agilent 400-
MR DD2. Quantification of N2O was performed on Shimadzu GC-
2030 gas chromatograph equipped with a barrier discharge
ionization (BID) detector. ESI-MS were performed on a Waters
ACS Paragon Plus Environment

Page 9 of 14
Journal of the American Chemical Society
ESI MS calcd for [2+H]+, m/z = 1038.15. Found: m/z = 1037.90.
Anal. Calcd for C49H61FeNOP2S4Si4: C, 56.68; H, 5.92; N, 1.35.
Found: C, 56.68; H, 5.92; N, 1.37.
color of solution gradually turned deep purple. The reaction
mixture was stirred for 10 min at 0 C, and the solvent was
removed under vacuum to obtain purple solid. The purple solid
was dissolved in hexane (20 mL) and then purified by silica gel
chromatography using hexane as eluent to give
[Mn(NO)(TMSPS3)] (6). (0.1180 g, 60 %). Vaporization of solvents
from diethyl ether/hexane (1:3, v/v) solution of 6 in an open vial
in glovebox at room temperature for one week led to dark purple
crystals suitable for X-ray crystallography. IR: νNO = 1780 (s, KBr)
cm−1; νNO = 1778 (s, toluene) cm−1. UVvis (toluene): λmax (ε) =
445 nm (4745), 575 nm (6115), 760 nm (2620), 970 nm (2810).
ESI MS calcd for [6]+, m/z = 656.04. Found: m/z = 655.91. Anal.
calcd for C27H36MnNOPS3Si3: C, 49.36; H, 5.52; N, 2.13. Found: C,
49.56; H, 5.53; N, 2.13.
1
2
3
4
5
6
7
8
Preparation of [Fe(TMSPS2)(TMSPS2CH3)] (3). In a glovebox, a
toluene solution (3.0 mL) containing [FeNO(TMSPS2)(TMSPS2CH3)]
(2, 0.013 g, 0.011 mmol) was loaded into the Schlenk flask and a
CH2Cl2 solution of CoII(TPP) (5 mL, 2 mM) was loaded into a
smaller tube. The smaller tube containing solution of CoII(TPP)
then was placed into the Schlenk flask with solution of 2, keeping
the two solutions separate (see Figure S12). The reaction flask
was sealed with a glass stopper and was then irradiated with a
Xe lamp for 3 min (filtering out heat and wavelengths less than
400 nm, 150 W). The reaction was kept sealed for 1 h in the dark
before workup. The UVvis spectrum obtained from inner tube
displayed absorption bands at 414 and 537 nm, indicating the
formation of Co(NO)(TPP). Diffusion of hexane into a CH2Cl2
solution of Co(NO)(TPP) at 4 °C for one week led to dark red
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Photolysis of 1 or 2. A toluene solution of 1 or 2 (~0.3 mL, 15
mM) was loaded into a sealed IR liquid cell composed of CaF2
windows with a 0.1 mm spacer in a glove box (N2 atmosphere).
The IR cell was inserted to the cell holder of FTIR spectrometer
and the solution of 1 or 2 sandwiched between two CaF2
crystals, Co(NO)(TPP) (0.0060 g, 90 %). IR (KBr, pellet): νNO
=
1697(s), 1690(sh) cm−1. The reaction mixture of the Schlenk flask
was dried under vacuum to give purple-red solid
[Fe(TMSPS2)(TMSPS2CH3)] (3, 0.071 g, 70 %). Diffusion of hexane
into a THF/CH2Cl2 (4:1, v/v) solution of 3 at room temperature
for one week led to dark-red crystals suitable for X-ray
crystallography. 1H NMR (toluene-d8, 20 C): δ = 10.85 (br), 9.52
(br), 7.55 (br), 6.31 (br), 6.16 (br), 4.67 (br), 0.02 (br), 0.20 (br).
UVvis (toluene): λmax (ε) = 470 nm (1715), 540 nm (1425), 700
nm (1560), 865 nm (1560). ESI MS calcd for [3]+, m/z = 1007.15.
windows was then irradiated with
a Xe lamp positioned
approximately 1 cm from the spacer. The interval for irradiating
the sample of 1 is 5 s (from black to blue traces) and 20 s (from
blue to red traces; Figure 2a), and the illumination was off during
IR data acquisition. The total irradiated time for this reaction is 3
min. After 3 min irradiation, the intensities of IR bands at 2219,
1823, and 1774 cm−1 show no significant changes for subsequent
photolysis. In the case of 2, the interval for irradiating the sample
of 2 is 5 s (from pink to green traces; Figure 2b) and the
illumination was off during IR data acquisition. The total
irradiated time for this reaction is 30 s.
Quantification of N2O upon Photolysis of 1. Quantitative
detection of N2O was based on gas chromatogram with retention
time at 6.52 min upon photolysis of 1 (0.0103 g dissolved in 3 mL
toluene loaded in 25-mL vial). A portion of the headspace above
the sample solution (3 mL) was pulled into a gas-tight glass
syringe (1 mL) and was then injected into the GC. An N2O
calibration curve (Figure S10) was constructed by injection of
various amounts of N2O(g) into a vial containing 3 mL toluene.106
The percent yield (15 %) of N2O was obtained.
Found: m/z
= 1007.15. Anal. Calcd for C49.5H62ClFeP2S4Si4
(3·0.5CH2Cl2): C, 56.58; H, 5.95. Found: C, 56.66; H, 6.05.
Preparation of [Fe(TMSPS2)2] (4). A CH2Cl2 solution (5 mL)
containing [FeNO(TMSPS2)(TMSPS2H)] (1, 0.0315 g, 0.03 mmol)
and [MnIII(TMSPS3)(DABCO)] (0.0222 g, 0.03 mmol) were loaded
into the Schlenk flask wrapped with aluminum foil and sealed
with a glass stopper. After the aluminum foil was removed, the
reaction flask was then irradiated with a Xe lamp for 10 min.
Analysis of the green-blue solution by IR and UVvis
spectroscopies revealed the formation of mixtures containing 4,
5− and 6. Calculations from UVvis spectrum deconvolution
revealed the formation of 4 (35 % yield based on  at 865 nm)
and 6 (30 % yield based on  at 970 nm), respectively. Diffusion
of hexane into a CH2Cl2 solution of mixtures at room temperature
for four days under N2 led to dark-blue crystals suitable for X-ray
crystallography (4, 0.0090 g, 30 %). 1H NMR (toluene-d8, 20 C):
δ = 21.18 (br), 16.51 (br), 14.34 (br), 14.19 (br), 10.86 (br), 6.63
(br), 0.42 (br), 0.11 (br). UVvis (CH2Cl2): λmax (ε) = 475 nm
(2100), 535nm (2155), 670 nm (4230), 865 nm (1545). ESI MS
calcd for [4]+, m/z = 992.13. Found: m/z = 992.13. Anal. calcd for
C49.5H61Cl3FeP2S4Si4 (4·1.5CH2Cl2): C, 53.05; H, 5.49. Found: C,
53.09; H, 5.43.
Photolysis
of
1
or
2
in
the
presence
of
[MnIII(TMSPS3)(DABCO)]. A 0.3 mL of CH2Cl2 solution (1 mL)
containing 1 (0.0153 g, 0.015 mmol) or 2 (0.0155, 0.015 mmol),
and [MnIII(TMSPS3)(DABCO)] (0.0148 g, 0.02 mmol) was loaded
into a sealed IR liquid cell composed of CaF2 windows with a 0.1
mm spacer in a glove box (N2 atmosphere). The IR cell was
inserted to the cell holder of FTIR spectrometer and the solution
of 1 or 2, and [MnIII(TMSPS3)(DABCO)] sandwiched between two
CaF2 windows was then irradiated with a Xe lamp positioned
approximately 1 cm from the spacer. The irradiated time for this
reaction of 1 in the presence of [MnIII(TMSPS3)(DABCO)] is 20 s
(from black to red traces; Figure 5a), and the illumination was off
during IR data acquisition. The NO at 1703 cm−1 is assigned as
[Mn(NO)(TMSPS3)]− (5−; 55 % yield, estimated by 15 mM of
[PPN][5] in CH2Cl2 which transmittance (%) is 60). The NO at
1778 cm−1 is assigned as [Mn(NO)(TMSPS3)] (6; 32 % yield,
estimated by 15 mM of 6 in CH2Cl2 which transmittance (%) is 55
). The irradiated time for this reaction of 2 in the presence of
[MnIII(TMSPS3)(DABCO)] is 20 s (from pink to green traces; Figure
5b), and the illumination was off during IR data acquisition. The
Preparation of [PPN][Mn(NO)(TMSPS3)] ([PPN][5]). A THF
solution (1.1 mL) of Li(C2H5)3BH (0.20 M) was added dropwise
to an THF solution (15 mL) of [Mn(NO)(TMSPS3)] (6; 0.2 mmol,
0.1320 g) at room temperature under N2. After the mixture was
stirred for 10 min, [PPN][Cl] (0.1150 g, 0.2 mmol) was added. The
resulting dark-red solution was reduced to 5 mL under vacuum
and hexane (25 mL) was added to precipitate dark-red solid,
[PPN][Mn(NO)(TMSPS3)] ([PPN][5]). Diffusion of diethyl ether
into a THF/CH3CN solution (5:1, v/v) of [PPN][5] at room
temperature for two days under N2 led to dark-red crystals
suitable for X-ray crystallography ([PPN][5]; 0.1910 g, 80 %). IR:
νNO = 1688 (s, KBr) cm−1; νNO = 1698 (s, CH2Cl2) cm−1. UVvis
(THF/CH3CN, 1:1 v/v): λmax (ε) = 480 nm (sh, 2060), 495 nm
(2150), 660 nm (740). ESI MS calcd for 5−, m/z = 656.04. Found:
m/z = 656.01. Anal. calcd for C63H66MnN2OP3S3Si3: C, 63.29; H,
5.56; N, 2.34. Found: C, 63.22; H, 5.62; N, 2.40.

NO at 1778 cm−1 is assigned as [Mn(NO)(TMSPS3)] (6; 90 % yield,
estimated by 15 mM of 6 in CH2Cl2 which transmittance is 55).
Physical Measurements. The magnetic data of the micro-
crystalline samples of 3, 4, [PPN][5] and 6 were recorded on a
SQUID magnetometer (SQUID-VSM or MPMS3, Quantum Design)
under an external magnetic field (0.5 Tesla) in the temperature
range of 2–300 K. For 4, crystalline solid sample was placed in a
polycarbonate capsule and covered with a few drops of a low
viscosity inert oil (Fomblin Y45); the use of an oil prevents
orientation of the crystals in the magnetic field at low
Preparation of [Mn(NO)(TMSPS3)] (6).
A
portion of
[MnIII(TMSPS3)(DABCO)] (0.2220 g, 0.3 mmol) was dissolved in
30 mL of THF and the bright red solution was purged by NO(g) (90
% N2 + 10 % NO) for 3 min at 0 C. Upon exposure to NO gas, the
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 10 of 14
temperatures. Experimental susceptibility data were corrected
Performance Computing Service of Academia Sinica
for the diamagnetic contribution of the capsule, the sample
holder and the oil using experimentally obtained gram
susceptibilities. Molar susceptibility data were corrected for
diamagnetic contributions using the Pascal constants107 and the
increment method according to Haberditzl.108 Magnetic
properties were simulated using the julX_2s program.109 A Bruker
1
2
3
4
5
6
7
8
Computer Center (ASCC) and National Center for High-
Performance Computing (NCHC) for computing resources.
REFERENCES
1.
Culotta, E.; Koshland, D. E., NO News Is Good News.
EMXnano and EMXplus spectrometers equipped with
a
Science 1992, 258, 1862-1865.
continuous-flow he-lium/nitrogen variable-temperature unit
were used. Spectral analysis and simulations were performed
using the EasySpin program. 57Fe Mössbauer spectra were
recorded with a 57Co source in a Rh matrix using an alternating
constant acceleration Wissel Mößbauer spectrometer operated in
the transmission mode and equipped with a Janis closed-cycle
helium cryostat. Isomer shifts are given relative to iron metal at
ambient temperature. Experimental data were simulated using
the Mfit software.110 The X-ray single crystal crystallographic
data collections were carried out at 150 K for 1, 3, 4 and 6, and at
200 K for 2 and [PPN][5] with a Bruker D8 Venture X-ray Single-
Crystal Diffractometer equipped with Oxford cryostream 800+. A
summary of the crystallographic parameters for the complexes 1,
2, 3, 4, [PPN][5] and 6 was shown in Table S4. The structures
were solved by the direct method and refined by least-squares
cycles. All non-hydrogen atoms were refined anisotropically and
all hydrogen atoms were placed in geometrically calculated
positions. Four carbons (C17, C18, C41, C42 and C17', C18', C41',
C42': occupancy factor 0.807(14) and 0.193(14)) of
trimethylsilyl groups (Si2, and Si4) of 1 and one oxygen (O1 and
O1': occupancy factor 0.721(6) and 0.279(6)) of nitrosyl group of
[PPN][5] are found at disordered positions.
2.
Fukuto, J. M.; Switzer, C. H.; Miranda, K. M.; Wink, D. A.,
NITROXYL (HNO): Chemistry, Biochemistry, and Pharmacology.
Annu. Rev. Pharmacol. Toxicol. 2005, 45, 355-55.
9
3.
Szaciłowski, K.; Chmura, A.; Stasicka, Z., Interplay
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
between iron complexes, nitric oxide and sulfur ligands:
Structure, (photo)reactivity and biological importance. Coord.
Chem. Rev. 2005, 249, 2408-2436.
4.
Ford, P. C.; Lorkovic, I. M., Mechanistic Aspects of the
Reactions of Nitric Oxide with Transition-Metal Complexes.
Chem. Rev. 2002, 102, 993-1017.
5.
Miranda, K. M.; Paolocci, N.; Katori, T.; Thomas, D. D.;
Ford, E.; Bartberger, M. D.; Espey, M. G.; Kass, D. A.; Feelisch, M.;
Fukuto, J. M.; Wink, D. A., A biochemical rationale for the
discrete behavior of nitroxyl and nitric oxide in the
cardiovascular system. Proc. Natl. Acad. Sci. U. S. A. 2003, 100,
9196-9201.
6.
Burstyn, J. N.; Yu, A. E.; Dierks, E. A.; Hawkins, B. K.;
Dawson, J. H., Studies of the Heme Coordination and Ligand
Binding Properties of Soluble Guanylyl Cyclase (sGC):
Characterization of Fe(II)sGC and Fe(II)sGC(CO) by Electronic
Absorption and Magnetic Circular Dichroism Spectroscopies
and Failure of CO To Activate the Enzyme. Biochemistry 1995,
34, 5896-5903.
7.
Kim, S.; Deinum, G.; Gardner, M. T.; Marletta, M. A.;
ASSOCIATED CONTENT
Babcock, G. T., Distal Pocket Polarity in the Unusual Ligand
Binding Site of Soluble Guanylate Cyclase: Implications for the
Control of ·NO Binding. J. Am. Chem. Soc. 1996, 118, 8769-8770.
SUPPORTING INFORMATION
8.
Paolocci, N.; Saavedra, W. F.; Miranda, K. M.;
Spectroscopic data (UVvis, FTIR, NMR, ESI-MS, EPR, SQUID
and 57Fe Mössbauer), DFT calculations with computational
detail, crystallographic parameters (PDF) and X-ray data
(CIF). This material is available free of charge via the Internet
at http://pubs.acs.org.
Martignani, C.; Isoda, T.; Hare, J. M.; Espey, M. G.; Fukuto, J. M.;
Feelisch, M.; Wink, D. A.; Kass, D. A., Nitroxyl anion exerts redox-
sensitive positive cardiac inotropy in vivo by calcitonin gene-
related peptide signaling. Proc. Natl. Acad. Sci. U. S. A. 2001, 98,
10463-10468.
9.
Paolocci, N.; Katori, T.; Champion, H. C.; John, M. E. S.;
Miranda, K. M.; Fukuto, J. M.; Wink, D. A.; Kass, D. A., Positive
inotropic and lusitropic effects of HNO/NO− in failing hearts:
Independence from b-adrenergic signaling. Proc. Natl. Acad. Sci.
U. S. A. 2003, 100, 5537-5542.
AUTHOR INFORMATION
Corresponding Author
*E-mail: cmlee@nttu.edu.tw
*E-mail: mhchiang@chem.sinica.edu.tw
*E-mail: mltsai@mail.nsysu.edu.tw
10.
Fry, N. L.; Mascharak, P. K., Photoactive Ruthenium
Nitrosyls as NO Donors: How To Sensitize Them toward Visible
Light. Acc. Chem. Res. 2011, 44, 289-298.
11.
Lu, T.-T.; Wang, Y.-M.; Hung, C.-H.; Chiou, S.-J.; Liaw,
W.-F., Bioinorganic Chemistry of the Natural [Fe(NO)2] Motif:
Evolution of a Functional Model for NO-Related Biomedical
Application and Revolutionary Development of a Translational
Model. Inorg. Chem. 2018, 57, 12425-12443.
Author Contributions
#These authors contributed equally.
12.
Biology. Chem. Rev. 2004, 104, 403-418.
13. Rhine, M. A.; Sanders, B. C.; Patra, A. K.; Harrop, T. C.,
McCleverty, J. A., Chemistry of Nitric Oxide Relevant to
NOTES
The authors declare no competing financial interest.
Overview and New Insights into the Thiol Reactivity of
Coordinated NO in {MNO}6/7/8 (M = Fe, Co) Complexes. Inorg.
Chem. 2015, 54, 9351-9366.
ACKNOWLEDGMENT
Authors thank the supports from the Ministry of Science and
Technology of Taiwan (Grant 107-2113-M-143-001 for C.-M
Lee; Grant 106-2113-M-110-011-MY2 and 108-2113-M-110-
008 for M.-L Tsai; 107-2113-M-001-012-MY3 for M.-H.
Chiang) and Academia Sinica (AS-iMATE-109-22 and AS-SS-
108-02-1 for M.-H. Chiang). The authors gratefully
acknowledge the use of Electron Paramagnetic Resonance
spectrometer belonging to the High Valued Instrument
Center of National Sun Yat-sen University. We also thank High
14.
Lehnert, N.; Fujisawa, K.; Camarena, S.; Dong, H. T.;
White, C. J., Activation of Non-Heme Iron-Nitrosyl Complexes:
Turning Up the Heat. ACS Catal. 2019, 9, 10499-10518.
15.
Confer, A. M.; Vilbert, A. C.; Dey, A.; Lancaster, K. M.;
Goldberg, D. P., A Mononuclear, Nonheme FeII-Piloty's Acid
(PhSO2NHOH) Adduct: An Intermediate in the Production of
{FeNO}7/8 Complexes from Piloty's Acid. J. Am. Chem. Soc. 2019,
141, 7046-7055.
ACS Paragon Plus Environment

Page 11 of 14
Journal of the American Chemical Society
16.
Tseng, Y.-T.; Chen, C.-H.; Lin, J.-Y.; Li, B.-H.; Lu, Y.-H.;
{FeNO}7 and {FeNO}8 Analogues. Angew. Chem. Int. Ed. 2018, 57,
13465-13469.
Lin, C.-H.; Chen, H.-T.; Weng, T.-C.; Sokaras, D.; Chen, H.-Y.; Soo,
1
2
3
4
5
6
7
8
Y.-L.; Lu, T.-T., To Transfer or Not to Transfer? Development of a
Dinitrosyl Iron Complex as a Nitroxyl Donor for the
Nitroxylation of an FeIII–Porphyrin Center. Chem. Eur. J. 2015,
21, 17570-17573.
32.
Shin, S.; Choe, J.; Park, Y.; Jeong, D.; Song, H.; You, Y.;
Seo, D.; Cho, J., Artificial Control of Cell Signaling Using a
Photocleavable Cobalt(III)–Nitrosyl Complex. Angew. Chem. Int.
Ed. 2019, 58, 10126-10131.
17.
Montenegro, A. C.; Bari, S. E.; Olabe, J. A., Reactivity of
33.
Enemark, J. H.; Feltham, R. D., Principles of structure,
iron(II)-bound nitrosyl hydride (HNO, nitroxyl) in aqueous
solution. J. Inorg. Biochem. 2013, 118, 108-114.
bonding, and reactivity for metal nitrosyl complexes. Coord.
Chem. Rev. 1974, 13, 339-406.
18.
Filipovic, M. R.; Eberhardt, M.; Prokopovic, V.;
34.
Speelman, A. L.; Lehnert, N., Heme versus Non-Heme
Mijuskovic, A.; Orescanin-Dusic, Z.; Reeh, P.; Ivanovic-
Burmazovic, I., Beyond H2S and NO Interplay: Hydrogen Sulfide
and Nitroprusside React Directly to Give Nitroxyl (HNO). A New
Pharmacological Source of HNO. J. Med. Chem. 2013, 56, 1499-
1508.
Iron-Nitroxyl {FeN(H)O}8 Complexes: Electronic Structure and
Biologically Relevant Reactivity. Acc. Chem. Res. 2014, 47, 1106-
1116.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
35.
Hauser, C.; Glaser, T.; Bill, E.; Weyhermüller, T.;
Wieghardt, K., The Electronic Structures of an Isostructural
Series of Octahedral Nitrosyliron Complexes {Fe-NO}6,7,8
Elucidated by Mössbauer Spectroscopy. J. Am. Chem. Soc. 2000,
122, 4352-4365.
19.
implications in biology. Coord. Chem. Rev. 2005, 249, 433-455.
20. Sousa, E. H. S.; Ridnour, L. A.; Florencio S. Gouveia, J.;
Miranda, K. M., The chemistry of nitroxyl (HNO) and
Silva, C. D. S. d.; Wink, D. A.; Lopes, L. G. d. F.; Sadler, P. J., Thiol-
Activated HNO Release from a Ruthenium Antiangiogenesis
Complex and HIF-1α Inhibition for Cancer Therapy. ACS Chem.
Biol. 2016, 11, 2057-2065.
36.
Serres, R. G.; Grapperhaus, C. A.; Bothe, E.; Bill, E.;
Weyhermüller, T.; Neese, F.; Wieghardt, K., Structural,
Spectroscopic, and Computational Study of an Octahedral, Non-
Heme {Fe-NO}6−8 Series: [Fe(NO)(cyclam-ac)]2+/+/0. J. Am. Chem.
Soc. 2004, 126, 5138-5153.
21.
Wang, P. G.; Xian, M.; Tang, X.; Wu, X.; Wen, Z.; Cai, T.;
Janczuk, A. J., Nitric Oxide Donors: Chemical Activities and
Biological Applications. Chem. Rev. 2002, 102, 1091-1134.
37.
Montenegro, A. C.; Amorebieta, V. T.; Slep, L. D.;
Martín, D. F.; Roncaroli, F.; Murgida, D. H.; Bari, S. E.; Olabe, J. A.,
Three Redox States of Nitrosyl: NO+, NO·, and NO−/HNO
Interconvert Reversibly on the Same Pentacyanoferrate(II)
Platform. Angew. Chem. Int. Ed. 2009, 48, 4213-4216.
22.
Patra, A. K.; Afshar, R.; Olmstead, M. M.; Mascharak, P.
K., The First Non-Heme Iron(III) Complex with a Ligated
Carboxamido Group That Exhibits Photolability of a Bound NO
Ligand. Angew. Chem. Int. Ed. 2002, 41, 2512-2515.
38.
Patra, A. K.; Dube, K. S.; Sanders, B. C.; Papaefthymiou,
23.
Kovacs, J. A., Synthetic Analogues of Cysteinate-
G. C.; Conradie, J.; Ghosh, A.; Harrop, T. C., A thermally stable
{FeNO}8 complex: properties and biological reactivity of
reduced MNO systems. Chem. Sci. 2012, 3, 364-369.
Ligated Non-Heme Iron and Non-Corrinoid Cobalt Enzymes.
Chem. Rev. 2004, 104, 825-848.
24.
Harrop, T. C.; Mascharak, P. K., Fe(III) and Co(III)
39.
Speelman, A. L.; Lehnert, N., Characterization of a
Centers with Carboxamido Nitrogen and Modified Sulfur
Coordination: Lessons Learned from Nitrile Hydratase. Acc.
Chem. Res. 2004, 37, 253-260.
High-Spin Non-Heme {FeNO}8 Complex: Implications for the
Reactivity of Iron Nitroxyl Species in Biology. Angew. Chem. Int.
Ed. 2013, 52, 12283-12287.
25.
Eroy-Reveles, A. A.; Leung, Y.; Beavers, C. M.;
40.
Kupper, C.; Schober, A.; Demeshko, S.; Bergner, M.;
Olmstead, M. M.; Mascharak, P. K., Near-Infrared Light Activated
Release of Nitric Oxide from Designed Photoactive Manganese
Nitrosyls: Strategy, Design, and Potential as NO Donors. J. Am.
Chem. Soc. 2008, 130, 4447-4458.
Meyer, F., An Exclusively Organometallic {FeNO}7 Complex with
Tetracarbene Ligation and a Linear FeNO Unit. Inorg. Chem.
2015, 54, 3096-3098.
41.
Speelman, A. L.; Zhang, B.; Krebs, C.; Lehnert, N.,
26.
Hsieh, C.-H.; Darensbourg, M. Y., A {Fe(NO)3}10
Structural and Spectroscopic Characterization of a High-Spin
{FeNO}6 Complex with an Iron(IV)-NO- Electronic Structure.
Angew. Chem. Int. Ed. 2016, 55, 6685-6688.
Trinitrosyliron Complex Stabilized by an N-Heterocyclic
Carbene and the Cationic and Neutral {Fe(NO)2}9/10 Products of
Its NO Release. J. Am. Chem. Soc. 2010, 132, 14118-14125.
42.
Kupper, C.; Rees, J. A.; Dechert, S.; DeBeer, S.; Meyer, F.,
27.
McQuilken, A. C.; Ha, Y.; Sutherlin, K. D.; Siegler, M. A.;
Complete Series of {FeNO}8, {FeNO}7, and {FeNO}6 Complexes
Stabilized by a Tetracarbene Macrocycle. J. Am. Chem. Soc. 2016,
138, 7888-7898.
Hodgson, K. O.; Hedman, B.; Solomon, E. I.; Jameson, G. N. L.;
Goldberg, D. P., Preparation of Non-heme {FeNO}7 Models of
Cysteine Dioxygenase: Sulfur versus Nitrogen Ligation and
Photorelease of Nitric Oxide. J. Am. Chem. Soc. 2013, 135, 14024-
14027.
43.
Chalkley, M. J.; Peters, J. C., A Triad of Highly Reduced,
Linear Iron Nitrosyl Complexes: {FeNO}8–10. Angew. Chem. Int.
Ed. 2016, 55, 11995-11998.
28.
Jiang, Y.; Hayashi, T.; Matsumura, H.; Do, L. H.;
44.
Li, F.; Meyer, R. L.; Carpenter, S. H.; VanGelder, L. E.;
Majumdar, A.; Lippard, S. J.; Moënne-Loccoz, P., Light-Induced
N2O Production from a Non-heme Iron-Nitrosyl Dimer. J. Am.
Chem. Soc. 2014, 136, 12524-12527.
Nichols, A. W.; Machan, C. W.; Neidig, M. L.; Matson, E. M., Nitric
Oxide activation facilitated by cooperative multimetallic
electron transfer within an iron-functionalized
polyoxovanadate-alkoxide cluster. Chem. Sci. 2018, 9, 6379-
6389.
29.
McQuilken, A. C.; Matsumura, H.; Dürr, M.; Confer, A.
M.; Sheckelton, J. P.; Siegler, M. A.; McQueen, T. M.; Ivanović-
Burmazović, I.; Moënne-Loccoz, P.; Goldberg, D. P.,
Photoinitiated Reactivity of a Thiolate-Ligated, Spin-Crossover
Nonheme {FeNO}7 Complex with Dioxygen. J. Am. Chem. Soc.
2016, 138, 3107-3117.
45.
Speelman, A. L.; White, C. J.; Zhang, B.; Alp, E. E.; Zhao,
J.; Hu, M.; Krebs, C.; Penner-Hahn, J.; Lehnert, N., Non-heme
High-Spin {FeNO}6−8 Complexes: One Ligand Platform Can Do It
All. J. Am. Chem. Soc. 2018, 140, 11341-11359.
30.
Ke, C.-H.; Chen, C.-H.; Tsai, M.-L.; Wang, H.-C.; Tsai, F.-
46.
Fujisawa, K.; Soma, S.; Kurihara, H.; Ohta, A.; Dong, H.
T.; Chiang, Y.-W.; Shih, W.-C.; Bohle, D. S.; Liaw, W.-F., {Fe(NO)2}9
Dinitrosyl Iron Complex Acting as a Vehicle for the NO Radical. J.
Am. Chem. Soc. 2017, 139, 67-70.
T.; Minakawa, Y.; Zhao, J.; Alp, E. E.; Hu, M. Y.; Lehnert, N., Stable
Ferrous Mononitroxyl {FeNO}8 Complex with a Hindered
Hydrotris(pyrazolyl)borate Coligand: Structure, Spectroscopic
Characterization, and Reactivity Toward NO and O2. Inorg.
Chem. 2019, 58, 4059-4062.
31.
Dey, A.; Confer, A. M.; Vilbert, A. C.; Moënne-Loccoz, P.;
Lancaster, K. M.; Goldberg, D. P., A Nonheme Sulfur-Ligated
{FeNO}6 Complex and Comparison with Redox-Interconvertible
47.
Confer, A. M.; Sabuncu, S.; Siegler, M. A.; Moënne-
Loccoz, P.; Goldberg, D. P., Mononuclear, Nonheme, High-Spin
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 12 of 14
{FeNO}7/8 Complexes Supported by a Sterically Encumbered
N4S-Thioether Ligand. Inorg. Chem. 2019, 58, 9576-9580.
48. Keilwerth, M.; Hohenberger, J.; Heinemann, F. W.;
Sutter, J. r.; Scheurer, A.; Fang, H.; Bill, E.; Neese, F.; Ye, S.; Meyer,
K., A Series of Iron Nitrosyl Complexes {Fe-NO}6−9 and a Fleeting
{Fe-NO}10 Intermediate en Route to a Metalacyclic Iron
Nitrosoalkane. J. Am. Chem. Soc. 2019, 141, 17217-17235.
Intramolecular S-H Proton Interacting with Both Sulfur and
Nickel: Relevance to the [NiFe]/[NiFeSe] Hydrogenases. J. Am.
Chem. Soc. 2004, 126, 8406-8412.
1
2
3
4
5
6
7
8
67.
Lee, C.-M.; Chuo, C.-H.; Chen, C.-H.; Hu, C.-C.; Chiang,
M.-H.; Tseng, Y.-J.; Hu, C.-H.; Lee, G.-H., Structural and
Spectroscopic Characterization of a Monomeric Side-On
Manganese(IV) Peroxo Complex. Angew. Chem. Int. Ed. 2012, 51,
49.
Choi, I.-K.; Liu, Y.; Feng, D.; Paeng, K.-J.; Ryan, M. D.,
5427-5430.
Electrochemical and Spectroscopic Studies of Iron Porphyrin
Nitrosyls and Their Reduction Products. Inorg. Chem. 1991, 30,
1832-1839.
68.
Chang, H.-C.; Hsu, Y.-C.; Chen, C.-H.; Kuo, T.-S.; Lee, W.-
Z., Thioiminium and thiaphospholanium derived from
acetonitrile via nickel(II)-(2-mercaptophenyl)-phosphine
complexation. Dalton Trans. 2015, 44, 20808-20811.
9
50.
Chiang, C.-Y.; Darensbourg, M. Y., Iron nitrosyl
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
complexes as models for biological nitric oxide transfer
reagents. J. Biol. Inorg. Chem. 2006, 11, 359-370.
69.
Yan, J.-A.; Chen, Y.-S.; Chang, Y.-H.; Tsai, C.-Y.; Lyu, C.-
L.; Luo, C.-G.; Lee, G.-H.; Hsu, H.-F., Redox Interconversion of
Non-Oxido Vanadium Complexes Accompanied by Acid-Base
Chemistry of Thiol and Thiolate. Inorg. Chem. 2017, 56, 9055-
9063.
51.
Pellegrino, J.; Bari, S. E.; Bikiel, D. n. E.; Doctorovich, F.,
Successful Stabilization of the Elusive Species {FeNO}8 in a
Heme Model. J. Am. Chem. Soc. 2010, 132, 989-995.
52.
Goodrich, L. E.; Roy, S.; Alp, E. E.; Zhao, J.; Hu, M. Y.;
70.
Chang, H.-C.; Lin, S.-H.; Hsu, Y.-C.; Jen, S.-W.; Lee, W.-Z.,
Lehnert, N., Electronic Structure and Biologically Relevant
Reactivity of Low-Spin {FeNO}8 Porphyrin Model Complexes:
New Insight from a Bis-Picket Fence Porphyrin. Inorg. Chem.
2013, 52, 7766-7780.
Nickel(III)-mediated oxidative cascades from a thiol-bearing
nickel(II) precursor to the nickel(IV) product. Dalton Trans.
2018, 47, 3796-3802.
71.
Pal, N.; Majumdar, A., Controlling the Reactivity of
53.
Confer, A. M.; McQuilken, A. C.; Matsumura, H.;
Bifunctional Ligands: Carboxylate-Bridged Nonheme Diiron(II)
Complexes Bearing Free Thiol Groups. Inorg. Chem. 2016, 55,
3181-3191.
Moënne-Loccoz, P.; Goldberg, D. P., A Nonheme, High-Spin
{FeNO}8 Complex that Spontaneously Generates N2O. J. Am.
Chem. Soc. 2017, 139, 10621-10624.
72.
Jana, M.; Majumdar, A., C-S Bond Cleavage, Redox
54.
Rahman, M. H.; Ryan, M. D., Redox and Spectroscopic
Reactions, and Dioxygen Activation by Nonheme Dicobalt(II)
Complexes. Inorg. Chem. 2018, 57, 617-632.
Properties of Iron Porphyrin Nitroxyl in the Presence of Weak
Acids. Inorg. Chem. 2017, 56, 3302-3309.
73.
Block, E.; Ofori-Okai, G.; Zubieta, J., 2-Phosphino- and
55.
Rahman, M. H.; Liu, Y.; Ryan, M. D., Proton Transfer
2-Phosphinylbenzenethiols: New Ligand Types. J. Am. Chem. Soc.
1989, 111, 2327-2329.
versus Hydrogen Bonding in a Reduced Iron Porphyrin Nitrosyl
Complex. Inorg. Chem. 2019, 58, 13788-13795.
74.
Grapperhaus, C. A.; Patra, A. K.; Mashuta, M. S., First
56.
Palanisamy, S.; Wang, Y.-L.; Chen, Y.-J.; Chen, C.-Y.;
{Fe-NO}6 Complex with an N2S3Fe-NO Core as a Model of NO-
Inactivated Iron-Containing Nitrile Hydratase. Are Thiolates and
Thioethers Equivalent Donors in Low-Spin Iron Complexes?
Inorg. Chem. 2002, 41, 1039-1041.
Tsai, F.-T.; Liaw, W.-F.; Wang, Y.-M., In Vitro and in Vivo Imaging
of Nitroxyl with Copper Fluorescent Probe in Living Cells and
Zebrafish. Molecules 2018, 23, 2551.
57.
Rhine, M. A.; Rodrigues, A. V.; Urbauer, R. J. B.;
75.
Lee, C.-M.; Hsieh, C.-H.; Dutta, A.; Lee, G.-H.; Liaw, W.-
Urbauer, J. L.; Stemmler, T. L.; Harrop, T. C., Proton-Induced
Reactivity of NO- from a {CoNO}8 Complex. J. Am. Chem. Soc.
2014, 136, 12560-12563.
F., Oxygen Binding to Sulfur in Nitrosylated Iron-Thiolate
Complexes: Relevance to the Fe-Containing Nitrile Hydratases. J.
Am. Chem. Soc. 2003, 125, 11492-11493.
58.
Walter, M. R.; Dzul, S. P.; Rodrigues, A. V.; Stemmler, T.
76.
Conradie, J.; Duncan A. Quarless, J.; Hsu, H.-F.; Harrop,
L.; Telser, J.; Conradie, J.; Ghosh, A.; Harrop, T. C., Synthesis of
CoII-NO- Complexes and Their Reactivity as a Source of Nitroxyl.
J. Am. Chem. Soc. 2016, 138, 12459-12471.
T. C.; Lippard, S. J.; Koch, S. A.; Ghosh, A., Electronic Structure
and FeNO Conformation of Nonheme Iron-Thiolate-NO
Complexes: An Experimental and DFT Study. J. Am. Chem. Soc.
2007, 129, 10446-10456.
59.
Doctorovich, F.; Bikiel, D.; Pellegrino, J.; Suárez, S. A.;
Larsen, A.; Martí, M. A., Nitroxyl (azanone) trapping by
metalloporphyrins. Coord. Chem. Rev. 2011, 255, 2764-2784.
77.
Rose, M. J.; Betterley, N. M.; Mascharak, P. K., Thiolate
S-Oxygenation Controls Nitric Oxide (NO) Photolability of a
Synthetic Iron Nitrile Hydratase (Fe-NHase) Model Derived
from Mixed Carboxamide/Thiolate Ligand. J. Am. Chem. Soc.
2009, 131, 8340-8341.
60.
Rivera-Fuentes, P.; Lippard, S. J., Metal-Based Optical
Probes for Live Cell Imaging of Nitroxyl (HNO). Acc. Chem. Res.
2015, 48, 2927-2934.
61.
Carrone, G.; Pellegrino, J.; Doctorovich, F., Rapid
78.
Coordination saturation might prevent the metal
generation of HNO induced by visible light. Chem. Commun.
2017, 53, 5314-5317.
center from O2 attack. The second possible reason is that the
nitrosonium character of the Fe-bound NO in 1 might decrease
the tendency toward reactions with O2. At this stage, other
possibilities cannot be excluded. Definite answers to the high
stability of 1 under aerobic conditions are not available.
62.
Lee, C.-M.; Wu, W.-Y.; Chiang, M.-H.; Bohle, D. S.; Lee,
G.-H., Generation of a Mn(IV)-Peroxo or Mn(III)-Oxo-Mn(III)
Species upon Oxygenation of Mono- and Binuclear Thiolate-
Ligated Mn(II) Complexes. Inorg. Chem. 2017, 56, 10559-10569.
79.
Southern, J. S.; Hillhouse, G. L., Preparation of a
63.
Schweitzer, D.; Ellison, J. J.; Shoner, S. C.; Lovell, S.;
Nitroxyl (HN=O) Complex of Rhenium by Selective Oxidation of
Coordinated Hydroxylamine. J. Am. Chem. Soc. 1997, 119,
12406-12407.
Kovacs, J. A., A Synthetic Model for the NO-Inactivated Form of
Nitrile Hydratase. J. Am. Chem. Soc. 1998, 120, 10996-10997.
64.
Xu, N.; Goodrich, L. E.; Lehnert, N.; Powell, D. R.;
80.
Lin, R.; Farmer, P. J., The HNO Adduct of Myoglobin:
Richter-Addo, G. B., Preparation of the Elusive [(por)Fe(NO)(O-
ligand)] Complex by Diffusion of Nitric Oxide into a Crystal of
the Precursor. Angew. Chem. Int. Ed. 2013, 52, 3896-3900.
Synthesis and Characterization. J. Am. Chem. Soc. 2000, 122,
2393-2394.
81.
Ling, Y.; Mills, C.; Weber, R.; Yang, L.; Zhang, Y., NMR,
65.
Hunt, A. P.; Lehnert, N., The Thiolate Trans Effect in
IR/Raman, and Structural Properties in HNO and RNO (R = Alkyl
and Aryl) Metalloporphyrins with Implication for the HNO-
Myoglobin Complex. J. Am. Chem. Soc. 2010, 132, 1583-1591.
Heme {FeNO}6 Complexes and Beyond: Insight into the Nature
of the Push Effect. Inorg. Chem. 2019, 58, 11317-11332.
66.
Lee, C.-M.; Chen, C.-H.; Ke, S.-C.; Lee, G.-H.; Liaw, W.-F.,
82.
Abucayon, E. G.; Khade, R. L.; Powell, D. R.; Zhang, Y.;
Mononuclear Nickel(III) and Nickel(II) Thiolate Complexes with
Richter-Addo, G. B., Hydride Attack on a Coordinated Ferric
ACS Paragon Plus Environment

Page 13 of 14
Journal of the American Chemical Society
Nitrosyl: Experimental and DFT Evidence for the Formation of a
Heme Model-HNO Derivative. J. Am. Chem. Soc. 2016, 138, 104-
96.
Dobmeier, K. P.; Riccio, D. A.; Schoenfisch, M. H.,
Xerogel Optical Sensor Films for Quantitative Detection of
Nitroxyl. Anal. Chem. 2008, 80, 1247-1254.
97.
Discrimination of Nitroxyl and Nitric Oxide by Water-Soluble
Mn(III) Porphyrins. J. Am. Chem. Soc. 2005, 127, 4680-4684.
98.
1
2
3
4
5
6
7
8
107.
83.
Greene, S. N.; Chang, C. H.; Richards, N. G. J., The role of
Martı´, M. A.; Bari, S. E.; Estrin, D. o. A.; Doctorovich, F.,
post-translational modification in the photoregulation of Fe-
type nitrile hydratase. Chem. Commun. 2002, 2386-2387.
84.
Greene, S. N.; Richards, N. G. J., Theoretical
To evaluate the trapping ability of
Investigations of the Electronic Structure and Spectroscopy of
[MnIII(TMSPS3)(DABCO)], we use Angeli's salt (Na2ONNO2), a
classical nitroxyl donor, for the test. Reaction of Angeli's salt
with [MnIII(TMSPS3)(DABCO)] yields [Mn(NO)(TMSPS3)]− (5−, νNO
= 1700 cm−1, KBr pellet, Figure S24). The result suggests that
[MnIII(TMSPS3)(DABCO)] is suitable for the application of the
HNO trapping.
Mononuclear, Non-Heme {Fe-NO}6 Complexes. Inorg. Chem.
2004, 43, 7030-7041.
-
85.
Sanders, B. C.; Hassan, S. M.; Harrop, T. C., NO2
9
Activation and Reduction to NO by a Nonheme Fe(NO2)2
Complex. J. Am. Chem. Soc. 2014, 136, 10230-10233.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
86.
Richter-Addo, G. B.; Hodge, S. J.; Yi, G.-B.; Khan, M. A.;
99.
Lin, C.-H.; Chen, C.-G.; Tsai, M.-L.; Lee, G.-H.; Liaw, W.-
Ma, T.; Caemelbecke, E. V.; Guo, N.; Kadish, K. M., Synthesis,
Characterization, and Spectroelectrochemistry of Cobalt
Porphyrins Containing Axially Bound Nitric Oxide. Inorg. Chem.
1996, 35, 6530-6538.
F., Monoanionic {Mn(NO)}5 and Dianionic {Mn(NO)}6
Thiolatonitrosylmanganese Complexes: [(NO)Mn(L)2]- and
[(NO)Mn(L)2]2− (LH2 = 1,2-Benzenedithiol and Toluene-3,4-
dithiol). Inorg. Chem. 2008, 47, 11435-11443.
87.
Lu, T.-T.; Chen, C.-H.; Liaw, W.-F., Formation of the
100.
Gütlich, P.; Bill, E.; Trautwein, A. X., Mössbauer
Distinct Redox-Interrelated Forms of Nitric Oxide from Reaction
of Dinitrosyl Iron Complexes (DNICs) and Substitution Ligands.
Chem. Eur. J. 2010, 16, 8088-8095.
Spectroscopy and Transition Metal Chemistry. Springer:
Heidelberg, 2011.
101.
o-Dithiolene and o-aminothiolate chemistry of iron: Synthesis,
structure and reactivity. Coord. Chem. Rev. 2010, 254, 1358–
1382.
Sproules, S.; Wieghardt, K., Sproules, S.; Wieghardt, K.,
88.
Chuang, C.-H.; Liaw, W.-F.; Hung, C.-H., Conversion of
Nitric Oxide into Nitrous Oxide as Triggered by the Polarization
of Coordinated NO by Hydrogen Bonding. Angew. Chem. Int. Ed.
2016, 55, 5190-5194.
102.
Ray, K.; Bill, E.; Weyhermüller, T.; Wieghardt, K.,
89.
Wijeratne, G. B.; Bhadra, M.; Siegler, M. A.; Karlin, K. D.,
Redox-Noninnocence of the S,S′-Coordinated Ligands in
Bis(benzene-1,2-dithiolato)iron Complexes. J. Am. Chem. Soc.
2005, 127, 5641-5654.
Copper(I) Complex Mediated Nitric Oxide Reductive Coupling:
Ligand Hydrogen Bonding Derived Proton Transfer Promotes
N2O(g) Release. J. Am. Chem. Soc. 2019, 141, 17962-17967.
103.
Sellmann, D.; Geck, M.; Knoch, F.; Ritter, G.; Dengler, J.,
90.
Suarez, S. n. A.; Neuman, N. s. I.; Muñoz, M.; Álvarez, L.
Transition-Metal Complexes with Sulfur Ligands. 57.
Stabilization of High-Valent Fe(IV) Centers and Vacant
Coordination Sites by Sulfur -Donation: Syntheses, X-ray
Structures, and Properties of [Fe(“S2”)2(PMe3)n] (n = 1, 2) and
(NMe4)[Fe(“S2”)2(PMe3)2]∙CH3OH (“S2”2− = 1,2-
Benzenedithiolate(2-)). J. Am. Chem. Soc. 1991, 113, 3819-3828.
104.
Oxide Promoted by a Mn Tropocoronand. J. Am. Chem. Soc.
1998, 120, 9034-9040.
105.
Nitrosyltricarbonylferrat, [Fe(CO)3NO]. Z. Anorg. Allg. Chem.
1963, 320, 101-111.
a.; Bikiel, D. n. E.; Brondino, C. D.; Ivanović-Burmazović, I.;
Miljkovic, J. L.; Filipovic, M. R.; Martí, M. A.; Doctorovich, F.,
Nitric Oxide Is Reduced to HNO by Proton-Coupled Nucleophilic
Attack by Ascorbate, Tyrosine, and Other Alcohols. A New Route
to HNO in Biological Media? J. Am. Chem. Soc. 2015, 137, 4720-
4727.
Franz, K. J.; Lippard, S. J., Disproportionation of Nitric
91.
Hamer, M.; Suarez, S. A.; Neuman, N. s. I.; Alvarez, L.;
Muñoz, M.; Marti, M. A.; Doctorovich, F., Discussing Endogenous
NO•/HNO Interconversion Aided by Phenolic Drugs and
Vitamins. Inorg. Chem. 2015, 54, 9342-9350.
Hieber, W.; Beutner, H., Über
92.
Suarez, S. A.; Muñoz, M.; Alvarez, L.; Venâncio, M. F.;
Rocha, W. R.; Bikiel, D. E.; Marti, M. A.; Doctorovich, F., HNO Is
Produced by the Reaction of NO with Thiols. J. Am. Chem. Soc.
2017, 139, 14483-14487.
106.
Wu, W.-Y.; Hsu, C.-N.; Hsieh, C.-H.; Chiou, T.-W.; Tsai,
M.-L.; Chiang, M.-H.; Liaw, W.-F., NO-to-[N2O2]2−-to-N2O
Conversion Triggered by {Fe(NO)2}10-{Fe(NO)2}9 Dinuclear
Dinitrosyl Iron Complex. Inorg. Chem. 2019, 58, 9586-9591.
93.
Ivanovic-Burmazovic, I.; Filipovic, M. R., Saying NO to
H2S: A Story of HNO, HSNO, and SSNO. Inorg. Chem. 2019, 58,
4039-4051.
94.
aqueous solutions: Spin states, protic equilibria, and reactivities
toward oxygen and nitric oxide. Proc. Natl. Acad. Sci. U. S. A.
2002, 99, 7340-7345.
107.
Pascal's Constants. J. Chem. Educ. 2008, 85, 532-536.
108. Haberditzl, W., Advances in Molecular Diamagnetism.
Angew. Chem. Int. Ed. 1966, 5, 288-298.
Bain, G. A.; Berry, J. F., Diamagnetic Corrections and
Shafirovich, V.; Lymar, S. V., Nitroxyl and its anion in
109.
Bill, E. julX_2s, Max-Planck Institute for Chemical
Energy Conversion, Mülheim/Ruhr, Germany, 2014.
110.
Conversion, Mülheim/Ruhr, Germany, 2008.
95.
Lymar, S. V.; Shafirovich, V.; Poskrebyshev, G. A., One-
Bill, E. Mfit, Max-Planck Institute for Chemical Energy
Electron Reduction of Aqueous Nitric Oxide: A Mechanistic
Revision. Inorg. Chem. 2005, 44, 5212-5221.
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 14 of 14
Table of Contents
1
2
3
4
5
R
R
Ph
Ph
P
S
S
Me
P
H
6
7
8
9
R
R
R
ON
S
NO
S
HNO
Fe
Fe
S
S
S
S
R
R
R
P
P
Ph
Ph
{FeNO}6
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
{FeNO}6
Me+
14
ACS Paragon Plus Environment