Synthesis, electrochemical and spectroelectrochemical characterization of iron(III) tetraarylporphyrins containing four β, β ′-butano and β, β ′-benzo fused rings

Article abstract of DOI:10.1142/S1088424618500517

Six iron(III) tetraarylporphyrins containing four b,b?-butano or b,b?-benzo fused rings were synthesized and characterized by electrochemistry and spectroelectrochemistry in nonaqueous media. The examined compounds are represented as butano(TpYPP)FeCl and

Full text of DOI:10.1142/S1088424618500517

Journal of Porphyrins and Phthalocyanines
J. Porphyrins Phthalocyanines 2018; 22: 1–14
DOI: 10.1142/S1088424618500517
Published at http://www.worldscinet.com/jpp/
Synthesis, electrochemical and spectroelectrochemical
characterization of iron(III) tetraarylporphyrins containing
four b,b′-butano and b,b′-benzo fused rings
Weijie Xua, Yuanyuan Fanga, Zhongping Ou*a,b◊, Mingyuan Chena,b
and Karl M. Kadish*b◊
aSchool of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang, 212013, China
bDepartment of Chemistry, University of Houston, Houston, TX 77204-5003, USA
Received 20 March 2017
Accepted 11 April 2017
ABSTRACT: Six iron(III) tetraarylporphyrins containing four b,b′-butano or b,b′-benzo fused rings
were synthesized and characterized by electrochemistry and spectroelectrochemistry in nonaqueous
media. The examined compounds are represented as butano(TpYPP)FeCl and benzo(TpYPP)FeCl,
where TpYPP is a dianion of the meso-substituted porphyrin, Y is a CH3, H or Cl substituent on the
para-position of the four meso-phenyl rings and butano and benzo are the b,b′-substituents on each of
the four pyrrole rings of the compound. Up to three reductions are observed for each Fe(III) butano- and
benzoporphyrin in CH2Cl2 or pyridine containing 0.1 M TBAP, the first of which is assigned in each case
to a metal-centered electron transfer. The second reduction is also metal-centered in CH2Cl2 and leads to
formation of an Fe(I) porphyrin, but it is porphyrin ring-centered and gives an Fe(II) porphyrin p-anion
radical reduction product when pyridine is used as the solvent. The effects of the solvent and type of
fused ring system (butano or benzo) on the UV-vis spectra and electrochemical properties of the Fe(III)
porphyrins are discussed and comparisons are made to both the structurally related non-b,b′-substituted
iron porphyrins and earlier described butano- or benzotetraarylporphyrins containing Cu(II) or Co(II)
central metal ions.
KEYWORDS: synthesis, iron(III) tetrabutanoporphyrins, iron(III) tetrabenzoporphyrins, electro-
chemistry, spectroelectrochemistry, substituent effects.
and spectroscopic properties of these compounds in their
INTRODUCTION
neutral, reduced or oxidized forms are virtually unknown.
Iron porphyrins are some of the most studied
We recently reported the synthesis and electro-
metalloporphyrins, in part because of their biological
chemistry of tetraaryltetrabutano- and tetraaryltetra-
relevance and in part because they can be used as
benzoporphyrins containing Co(II) [50], Cu(II) [51]
catalysts in a variety of reactions [1–26]. A large number
or Pt(II) [52] central metal ions and have now turned
of iron porphyrins with different meso and/or b-pyrrole
our attention to derivatives of Fe(III) containing these
substituents have been synthesized and electrochemically
two porphyrin skeletal structures. The examined
characterizedoverthelastfourdecades[26–47]. However,
compounds are represented as butano(TpYPP)FeCl and
to the best of our knowledge, only a few b,b′ butano or
benzo(TpYPP)FeCl, where TpYPP is a dianion of the
b,b′ benzo substituted iron tetraarylporphyrins have been
meso-substitutedporphyrin,YisaCH3, HorClsubstituent
reported in the literature [48, 49] and the electrochemistry
on the para-position of the four meso-phenyl rings, and
butano and benzo are the b,b′-fused ring substituents
on each of the four pyrrole groups of the compound.
◊ SPP full member in good standing
The structures of the newly-investigated porphyrins are
shown in Chart 1 along with that of the parent iron(III)
*Correspondence to: Zhongping Ou, email: zpou2003@yahoo.
com or Karl M. Kadish, email: kkadish@uh.edu.
Copyright © 2018 World Scientific Publishing Company

2
W. XU ET AL.
literature [53]. The butano(TpYPP)FeCl
2a–2c complexes were synthesized via a
reaction between butano(TpYPP)H2 [49,
.
54] and Fe(Cl)2 4H2Oin DMF (Scheme 1a)
while the benzo(TpYPP)FeCl 3a–3c deriv-
atives were synthesized via the route shown
in Scheme 1b. The free-base benzopor-
phyrins were obtained by demetalation of
the corresponding copper benzoporphyrins
[51] in acid solution and then reacted
.
with FeCl2 4H2O in DMF to generate the
desired Fe(III) benzoporphyrins 3a–3c.
Chart 1. Structures of investigated iron(III) porphyrins
tetraarylporphyrin, represented as (TpYPP)FeCl. The
effects of solvent and type of fused ring structure on
the UV-vis spectra and electrochemical properties are
described and comparisons made to both structurally
related non-b,b′-substituted Fe(III) porphyrins and
earlier described butano- and benzoporphyrin derivatives
with Cu(II) or Co(II) central metal ions.
UV-vis spectra
The UV-vis spectra and redox properties of each
Fe(III) porphyrin in Chart 1 were measured in both the
non-binding solvent CH2Cl2 and the binding solvent
pyridine. Examples of the spectra are given in Fig. 1,
which compares the three types of porphyrins with
meso-PhCH3 groups (compounds 1a, 2a and 3a) in the
two solvents, while Fig. S1 illustrates spectra under the
same two solution conditions for the three series of iron
porphyrins with meso-Ph (1b, 2b and 3b) or meso-PhCl
substituents (1c, 2c and 3c).
RESULTS AND DISCUSSION
Synthesis
As seen in the two figures, quite different spectra are
obtained for the three series of Fe(III) porphyrins with
different macrocycles. The difference in UV-vis spectra
Non-b,b′-substituted iron(III) porphyrins, (TpYPP)FeCl
1a–1c, were synthesized according to a procedure in the
(a) Fe(III) butanoporphyrins 2a-2c
Y
Y
N
HN
N
N
N
FeCl2⋅4H2O
Y
Y
Y
Y
Fe
NH
DMF, N2, reflux
N
N
Cl
2a, 2b, 2c
Y
Y
(b) Fe(III) benzoporphyrins 3a-3c
Y
Y
Y
N
N
N
N
H2SO4
FeCl2⋅4H2O
N
HN
N
N
N
N
Y
Y
Y
Cu
Y
Y
Y
Fe
Cl
rt, 5 min
DMF, N2, reflux
N
NH
3a, 3b, 3c
Y
Y
Y
Scheme 1. Synthesis routes for preparing the Fe(III) (a) butanoporphyrins 2a–2c and (b) benzoporphyrins 3a–3c
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SYNTHESIS, ELECTROCHEMICAL AND SPECTROELECTROCHEMICAL CHARACTERIZATION OF IRON(III)
3
Fig. 1. UV-vis spectra of (TpCH3PP)FeCl 1a, butano(TpCH3PP)FeCl 2a and benzo(TpCH3PP)FeCl 3a in (a) CH2Cl2 and (b) pyridine.
The spectrum of 3a in pyridine was measured at least 5 min after dissolving the compound in solution
between CH2Cl2 and pyridine can be accounted for
in each case by the presence or absence of two bound
pyridine molecules on the Fe(III) center of the porphyrin,
giving the six-coordinate bis-pyridine adducts in
pyridine, compared to the related five-coordinate chloro-
derivatives in CH2Cl2. This is consistent with what was
previously reported for other Fe(III) porphyrins with
substituted TPP or OEP skeletal structures [34, 41, 43,
45, 55]. In addition, a red shift in the Soret and Q bands
is seen upon going from the parent porphyrins 1a, 1b or
1c to the corresponding butanoporphyrins 2a, 2b or 2c,
and a further red shift in these bands occurs upon going
from the butanoporphyrins to the benzoporphyrins 3a,
3b or 3c, the latter of which have enhanced intensity
Q-band absorptions in the two solvents. The 614–618 nm
Q band of the three benzoporphyrins in pyridine has a
relatively high intensity compared to the single Q band
of compounds in other two solvents which are weak and
located at 529–539 for [(TpYPP)Fe(Py)2]+ and 561–
563 nm for [butano(TpYPP)Fe(Py)2]+, respectively. This
result is consistent with what was earlier reported for
tetraaryltetrabenzoporphyrins containing other central
metal ions under the same solution conditions [48, 50–54].
Electrochemistry
The electrochemistry of each Fe(III) porphyrin was
carried out in both CH2Cl2 and pyridine containing 0.1 M
TBAP. The reduction and oxidation potentials are given
in Table 1, and the results are described below for the
three porphyrins in each series, first for the tetraarylpor-
phyrins, then for the butanoporphyrins and finally for the
benzoporphyrins.
Tetraarylporphyrins. The electrochemistry of iron(III)
porphyrins with TPP skeletal structures is well-
documented in the literature [37, 45]. In general, up
to three reductions are observed for these types of
compounds within the solvent potential limit of CH2Cl2
containing 0.1 M TBAP, the first of which involves,
in every case, a conversion of the Fe(III) porphyrin
to its Fe(II) form. In the current study this process is
irreversible for the (TpYPP)FeIIICl derivatives 1a–1c
when examined by cyclic voltammetry which showed a
cathodic to anodic peak separation of about 410 mV for
all three compounds at a scan rate of 0.1V/s. The cathodic
reduction peak is located at Epc = -0.29 to -0.38 V for a
scan rate of 0.1 V/s, the exact value depending upon the
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W. XU ET AL.
Table 1. Half-wave potentials (V vs. SCE) of (TpYPP)FeCl, butano(TpYPP)FeCl and
benzo(TpYPP)FeCl in CH2Cl2 and pyridine containing 0.1 M TBAP
solvent
CH2Cl2
b,b-sub
Y
oxidation
reduction
none
CH3
H
1.36a
1.42a
1.43a
1.20a
1.23a
1.26a
0.94
1.13a
1.20a
1.28a
0.62
0.67
0.76
0.67
0.69
0.76
-0.38a
-0.36a
-0.29a
-0.72a
-0.72a
-0.68a
0.07, -0.25a
0.15, -0.19
0.19, -0.16a
0.14
-1.30a
-1.20a
-1.16a
-1.28
-1.27
-1.20
-1.72a
-1.65a
-1.64a
-1.62a
-1.57a
-1.50a
-1.81a
-1.78a
-1.70a
-1.60
-1.59
-1.48a
-1.82a
-1.80a
-1.70a
-1.68a
-1.68a
Cl
butano
benzo
none
CH3
H
Cl
CH3
H
1.13
1.13
0.93
Cl
0.96
Pyridine
CH3
H
-1.75
-1.73
-1.68
-1.91
-1.89
-1.80
0.17
Cl
0.23
butano
benzo
CH3
H
0.92a
0.94a
0.96a
0.76
0.79
0.83
-0.14
-0.12
Cl
-0.04
CH3
H
0.20
0.22
Cl
0.30
-1.64
a Irreversible peak potential at a scan rate of 0.10 V/s.
specific meso-substituent, and this one-electron addition
leads to the initial generation of [(TpYPP)FeIICl]- which
then loses the bound Cl- counterion, giving (TpYPP)FeII
as a final product which is re-oxidized at Epa = 0.12 to
0.03 V on the return sweep of the cyclic voltammograms
(see Fig. 2). The second reduction of the three parent
porphyrins is also irreversible in CH2Cl2, and the cathodic
peak for this process is located at Epc = -1.30 to -1.16 V
for a scan rate of 0.10 V/s. These reductions are proposed
to generate an Fe(I) porphyrin, which then reacts with
the CH2Cl2 solvent to give a transient s-bonded complex
which is described as (TpYPP)Fe(CH2Cl) [45, 56–58].
Three reductions of 1a–1c are also observed in pyridine
as shown in Fig. 3. The first one-electron addition is
reversible and located at E1/2 = 0.14 to 0.23V. This process
is assigned as a conversion of [(TpYPP)FeIII(Py)2]+ to
(TpYPP)FeII(Py)2. The second reduction has non-coupled
reduction and re-oxidation peaks which are separated
by 140 mV in all three compounds. Earlier mechanistic
studies on related compounds showed that the two bound
pyridine molecules dissociate following electron transfer,
giving [(TpYPP)FeII]-. as the final reduction product in
the current study, and this four-coordinate species is then
re-oxidized at a more positive potential of Epa = -1.36 to
-1.48 V on the return potential sweep.
Fig. 2. Cyclic voltammograms showing the reduction of
(a) (TpCH3PP)FeCl 1a, (b) (TPP)FeCl 1b and (c) (TpClPP)FeCl
1c in CH2Cl2 containing 0.1 M TBAP at a scan rate of 0.10 V/s
A number of structurally related meso- and/or
b-pyrrole substituted iron(III) tetraarylporphyrins have
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SYNTHESIS, ELECTROCHEMICAL AND SPECTROELECTROCHEMICAL CHARACTERIZATION OF IRON(III)
5
also been examined as to their spectroscopic properties
after electroreduction in nonaqueous media [32, 35, 46,
55, 59–61]. As mentioned above, the first one-electron
reduction is invariably metal-centered to give an Fe(II)
porphyrin. The addition of a second electron may
also involve a metal-centered reaction to give an Fe(I)
porphyrin with an unreduced macrocycle, but this is not
always the case and an Fe(II) porphyrin p-anion radical
may also be formed, depending upon the type and number
of meso and/or b-pyrrole substituents, the type and
number of axial ligands and the specific electrochemical
solvent utilized [37, 45].
Figure 4 shows the spectroelectrochemical data for the
first two reductions of (TpCH3PP)FeIIICl 1a in CH2Cl2
and pyridine containing 0.1 M TBAP. In both solvents,
the spectral changes during the first reduction are similar
to what has been reported for other structurally related
Fe(III) tetraarylporphyrins and are consistent with the
Fig. 3. Cyclic voltammograms showing the reduction of
(a) (TpCH3PP)FeCl 1a, (b) (TPP)FeCl 1b and (c) (TpClPP)FeCl
1c in pyridine 0.1 M TBAP at a scan rate of 0.10 V/s
generation of a four-coordinate Fe(II) porphyrin in
CH2Cl2 and a six-coordinate bis-pyridine derivative in
Fig. 4. Cyclic voltammograms and UV-vis spectral changes of (TpCH3PP)FeCl 1a obtained during the first two controlled potential
reductions in (a) CH2Cl2 and (b) pyridine containing 0.1 M TBAP
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W. XU ET AL.
Fig. 5. Cyclic voltammograms of (a) butano(TpCH3PP)FeCl 2a, (b) butano(TPP)FeCl 2b and (c) butano(TpClPP)FeCl 2c in CH2Cl2
containing 0.1 M TBAP
pyridine [45, 46]. The final spectra, after completion of
the second reduction, are also consistent with what has
been reported for structurally related porphyrins giving
an unstable [FeIII(CH2Cl)] s-bonded porphyrin product
in CH2Cl2 and an Fe(II) porphyrin p-anion radical in
pyridine. Compared to (TpCH3PP)FeIIICl 1a, similar
spectral changes are observed for (TPP)FeIIICl 1b and
(TpClPP)FeIIICl 1c during the first two controlled
potential reductions in CH2Cl2 (Fig. S2), indicating that
the same reduction mechanism can be proposed for
compounds 1a–1c under the given solution conditions.
The large separation in cathodic and anodic peaks for
the second reduction of 1a in pyridine are similar to what
was previously reported upon reduction of (F20DPP)FeCl
(F20DPP = the dianion of 2,3,7,8,12,13,17,18-octaphenyl-
5,10,15,20-tetra(pentafluorophenyl)porphyrin) in PhCN or
pyridine [55]. In both of these solvents, the first reduction
was assigned as metal-centered to give an Fe(II) porphyrin,
while the second reduction was assigned as a ring-centered
process to give an Fe(II) porphyrin p-anion radical as the
main product. Little to no difference is seen in the UV-vis
spectral changes obtained during reduction of compounds
1b or 1c in pyridine (Fig. S3), and the assignments of
electron transfer sites should be the same as all three
porphyrins in the (TpYPP)FeCl series.
Butanoporphyrins. The three butano(TpYPP)FeCl
complexes 2a–2c exhibit mainly ill-defined reductions
in CH2Cl2 (Fig. 5). The first reduction peak is located at
Epc = -0.72 V for 2a, -0.74 V for 2b and -0.68 V for 2c
at a scan rate of 0.10 V/s and a re-oxidation peak is then
observed at Epa values between 0.06 and 0.18 V when
the potential scan direction is reversed. The separation
between Epc and Epa ranges from 780 to 860 mV
compared to the (TpYPP)FeCl complexes, where DEp
is equal to 410 mV as mentioned earlier and shown in
Fig. 2. The strong binding of Cl- to the Fe(III) form of the
butanoporphyrins leads to a larger negative shift in the
cathodic peak potential for the first reduction compared
to the three TPP derivatives, but far smaller shifts are
seen in the re-oxidation peaks, where the difference in
Epa values between the two series of compounds amounts
to only 30–70 mV.
The second reduction of the butanoporphyrins is
quasi-reversible and located at E1/2 values of -1.28 V (2a)
to -1.20 V (2c) in CH2Cl2. The cathodic peak potentials
for these reductions are quite similar to the cathodic
peak potentials for the irreversible reduction of the
corresponding derivatives 1a–1c, thus indicating only a
small effect of the butano groups on this redox reaction
involving the four-coordinate Fe(II) porphyrins.
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SYNTHESIS, ELECTROCHEMICAL AND SPECTROELECTROCHEMICAL CHARACTERIZATION OF IRON(III)
7
Fig. 6. Cyclic voltammogram and UV-vis spectral changes of butano(TpClPP)FeCl 2c during the reductions at -0.8 and -1.5 V, and
the oxidations at 0.9 and 1.4 V in CH2Cl2 containing 0.1 M TBAP
Two oxidations are observed for three butanopor-
phyrins, the first of which is reversible and located
at E1/2 = 0.62 V for 2a, 0.67 V for 2b and 0.76 V for
2c, respectively (Fig. 5). The cyclic voltammetric data
indicates the lack of a chemical reaction coupled to the
first electron abstraction in CH2Cl2 containing 0.1 M
TBAP, but this is not the case for the second oxidation
where an irreversible process is observed as indicated by
the lack of a re-reduction peak after generation of the
Fe(III) porphyrin dication.
Figure 6 illustrates the UV-vis spectral changes
obtained during the first two controlled potential reduc-
tions and oxidations of butano(TpClPP)FeCl 2c in CH2Cl2
containing 0.1 M TBAP. During the first controlled
potential reduction at -0.8 V, the 394 nm Soret band of
the neutral porphyrin decreases in intensity as a new Soret
band associated with the Fe(II) porphyrin grows in at
429 nm. This Fe(II) porphyrin Soret band then decreases
in intensity during the second reduction at -1.5 V and a
split band for the doubly reduced porphyrin appears at 436
and 463 nm. The result is consistent with a metal-centered
reaction to give the Fe(I) porphyrin, as was reported for
other structurally related iron porphyrins under similar
solution conditions [46, 62].
The spectral changes during controlled potential
oxidation of compound 2c in CH2Cl2 containing 0.1 M
TBAP are also shown in Fig. 6 and are consistent with two
stepwise porphyrin ring-centered electron abstractions
giving an Fe(III) porphyrin p-cation radical and dication,
respectively, in this solvent.
Similar to (TpYPP)FeCl 1a–1c and (F20DPP)FeCl
[55], the butano(TpYPP)FeCl derivatives 2a–2c also
undergo three reductions in pyridine containing 0.1 M
TBAP, with the first and third being reversible as shown
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W. XU ET AL.
Fig. 7. Cyclic voltammograms of (a) butano(TpCH3PP)FeCl
2a, (b) butano(TPP)FeCl 2b and (c) butano(TpClPP)FeCl 2c in
pyridine containing 0.1 M TBAP at a scan rate of 0.10 V/s
by the cyclic voltammograms of these compounds in
Fig. 7. The peak potentials for the second irreversible
reduction are located at Epc = -1.81 V (2a), -1.79 V (2b)
and -1.70 V (2c) at a scan rate of 0.10 V/s, and in each
case these processes are coupled with re-oxidation peaks
at Epa = -1.40 V (2a), -1.38 V for (2b) or -1.30 V (2c).
The hardest reduction (most negative potential) is seen
for 2a which contains an electron-donating CH3 group
on each meso-phenyl ring of the compound, while the
easiest reduction (most positive E1/2) is seen for 2c which
contains an electron-withdrawing Cl group on the four
meso-phenyl rings of the porphyrin macrocycle.
Fig. 8. Cyclic voltammogram and UV-vis spectral changes of
butano(TpClPP)FeCl 2c obtained during the first two controlled
potential reductions in pyridine containing 0.1 M TBAP
ThesedataareshowninFigsS4(CH2Cl2)andS5(pyridine).
The electrochemical and spectroelectrochemical data are
thus self-consistent in the two solvents. The proposed
reduction mechanisms in CH2Cl2 and pyridine are
illustrated in Scheme 2.
In summary, the first one-electron reduction of each
butano(TpYPP)FeIIICl complex is metal-centered to initi-
allygivethe[butano(TpYPP)FeIICl]- formoftheporphyrin
in CH2Cl2. This electron transfer is then followed by
chloride dissociation to generate butano(TpYPP)FeII,
which can then be further reduced to an Fe(I) porphyrin
anion at more negative potentials or re-oxidized to give
the original Fe(III) porphyrin at more positive potentials,
as shown in Scheme 2a.
The reduction mechanism in pyridine (Scheme 2b)
differs from that in CH2Cl2 for the same compound. The
initial form of the butanoporphyrin is given as [butano-
(TpYPP)FeIII(Py)2]+ which undergoes two stepwise one-
electron reductions, leadingtobutano(TpYPP)FeII(Py)2 and
[butano(TpYPP)FeII(Py)2]-, respectively. The two pyridine
axial ligands dissociate after generation of doubly reduced
[butano(TpYPP)FeII(Py)2]- to give [butano(TpYPP)FeII]-,
which can be reversibly reduced at more negative potentials
The first reduction of butano(TpClPP)FeIIICl 2c
in pyridine is assigned as generating an Fe(II) por-
phyrin on the basis of the spectral changes shown in
Fig. 8, where the initial Soret band at 429 nm is red
shifted to 439 nm and slightly increased in intensity.
This contrasts with the second controlled potential
reduction where the 439 nm Soret band of the Fe(II)
porphyrin is significantly decreased in intensity upon
electroreduction. There is also a new weak band for
the doubly reduced porphyrin at 374 nm as shown
in the figure. The final spectrum obtained after the
second reduction suggests that an Fe(II) porphyrin
p-anion radical is the main reduction product in the
second electron addition, as was previously reported
for (CN)4(TPP)FeCl [35] and FxDPPFeCl [55], where
DPP = the dianion of dodecaphenylporphyrin and x is
the number of fluorine groups on the four meso-phenyl
rings of the macrocycle.
Similar UV-vis spectral changes as described above
were obtained during controlled potential reduction of the
Fe(III) butanoporphyrins 2a and 2b in the two solvents.
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SYNTHESIS, ELECTROCHEMICAL AND SPECTROELECTROCHEMICAL CHARACTERIZATION OF IRON(III)
9
(a) in CH2Cl2
+e
PorFeIIICl
+Cl-
[PorFeIICl]-
-Cl-
-0.68 V
+e
0.18V
-e
[PorFeIII +
]
PorFeII
[PorFeI]-
-1.20 V
(b) in pyridine
+e
-0.04 V
+e
[PorFeIII(Py)2]+
PorFeII(Py)2
+2Py
[PorFeII(Py)2]-
-2Py
-1.70 V
-1.30 V
-e
+e
-1.80 V
PorFeII
[PorFeII]-
[PorFeI]2-
Por = butano(TpYPP)
Scheme 2. Proposed reduction mechanism of butano(TpYPP)FeCl in (a) CH2Cl2 and (b) pyridine containing 0.1 M TBAP. The listed
potentials are for compound 2c
Fig. 9. Cyclic voltammograms of benzo(TpCH3PP)FeCl 3a and benzo(TpClPP)FeCl 3c in (a) CH2Cl2 and (b) pyridine containing
0.1 M TBAP at a scan rate of 0.10 V/s
leading to [butano(TpYPP)FeI]2- or re-oxidized to give
back butano(TpYPP)FeII, prior to re-association of the two
pyridine molecules.
Benzoporphyrins. Cyclic voltammograms of the
Fe(III) benzoporphyrins in CH2Cl2 and pyridine contai-
ning 0.1 M TBAP are shown in Fig. 9 and Figs. S6–S7.
Two reductions are observed for each porphyrin between
four-coordinate Fe(II) product, benzo(TpYPP)FeII, is
then re-oxidized at Epa = 0.10 V for 3a and 0.22 V for
3c upon reversing the potential scan, as shown in Fig. 9.
The Fe(II) porphyrin can also be further reduced at more
negative potentials, but this process is ill-defined as
shown in Figs S6 and S7.
The three benzoporphyrins all exhibit reversible Fe(III)/
Fe(II) processes when pyridine is used as the solvent. As
seen in Fig. 9b, the first one-electron oxidation of 3a and
3c is also reversible. The one-electron addition to the
benzoporphyrin gives benzo(TpYPP)FeII(Py)2 and the
one-electron abstraction gives [benzo(TpYPP)FeIII(Py)2]2+.
It is well-known that meso-phenyl substituents can
significantly shift the redox potentials of iron porphyrins
[45], and this also the case for the currently examined
+0.20 and -0.25 V in CH2Cl2. The first is located at E1/2
=
0.07 V for 3a and 0.19 V for 3c as seen in Fig. 9a and is
assigned as a one-electron addition to the benzoporphyrin
with a dissociated Cl- axial ligand, i.e. [benzo(TpYPP)
FeIII]+. The second reduction is also assigned as Fe(III)/
Fe(II) process, in this case involving the conversion
of benzo(TpYPP))4FeIIICl to [benzo(TpYPP)FeIICl]-
which then rapidly losses the axial Cl- ligand. The
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W. XU ET AL.
Fig. 10. Thin-layer UV-vis spectral changes of benzo(TpYPP)FeCl 3a–3c obtained during the first controlled potential reduction in
(a) CH2Cl2 and (b) pyridine containing 0.1 M TBAP
benzoporphyrins. As seen in Fig. 9a, the first oxidation
and first reduction of compound 3c, which has four
electron-withdrawing Cl substituents on the four meso-
phenyl rings, are shifted positively by 90 mV in CH2Cl2
as compared to potentials for the same redox reaction
of compound 3a, which has four electron-donating CH3
substituents on the macrocycle. A 70–100 mV difference
in E1/2 values is also seen for the first oxidation and first
reduction of the same two porphyrins in pyridine (Fig. 9b).
The first reduction of the three benzoporphyrins 3a–3c
was examined by thin-layer spectroelectrochemistry in
CH2Cl2 and pyridine containing 0.1 M TBAP, and the
spectral changes obtained during the controlled potential
reduction are shown in Fig. 10. As seen in Fig. 10a, the
Soret and Q bands of the Fe(III) porphyrins which are
located at 434–438 and 565–607 nm in CH2Cl2 decrease in
intensity, while two new bands of the Fe(II) porphyrin grow
in at 470–478 and 650–657 nm upon the first reduction.
Figure 10b shows the spectral changes of 3a–3c
during the first controlled potential reduction in pyridine,
0.1 M TBAP. The split Soret band at 399–402 and 461–
463 nm, as well as the major Q band at 614–618 nm of
the initial six-coordinate compounds, benzo(TpYPP)
Fe(Py)2]+ all decrease in intensity, while two new
absorption bands grow in at 439–441 and 649–655 nm.
The original spectrum of the Fe(III) benzoporphyrin
could be recovered when the controlled potential was set
back to 0.0 V, and this behavior is consistent with the
reversible reductions observed by cyclic voltammetry of
the compounds in the same solvent (see Fig. 9b).
Copyright © 2018 World Scientific Publishing Company
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SYNTHESIS, ELECTROCHEMICAL AND SPECTROELECTROCHEMICAL CHARACTERIZATION OF IRON(III)
11
has a significant effect on the individual reduc-
tion and oxidation potentials of cobalt [50]
and copper [51] tetraarylporphyrins, and this
is also the case for the currently investigated
Fe(III) butanoporphyrins and benzoporphyrins.
This is shown by the cyclic voltammograms
of (TpClPP)FeCl 1c, butano(TpClPP)FeCl 2c
and benzo(TpClPP)FeCl 3c in Fig. 11 where
the measurements were carried out in pyridine
containing 0.1 M TBAP.
All three reductions of butano(TpClPP)FeCl
2c are negatively shifted by 120–270 mV com-
pared to potentials for the same redox reactions
of (TpClPP)FeCl 1c in pyridine (Fig. 11). This
is consistent with the fact that b,b′-butano is
an electron-donating substituent, which leads
to harder reductions compared to the corres-
ponding porphyrins without butano substituents.
A 220–260 mV positive shift is seen for the first
two reductions of the benzo(TpClPP)FeCl 3c
compared to the same electron transfer process
of butano(TpClPP)FeCl 2c in pyridine (Fig. 11).
Fig.11.Cyclicvoltammogramsof(a)(TpClPP)FeCl1c,(b)butano(TpClPP)
FeCl 2c and (c) benzo(TpClPP)FeCl 3c in pyridine containing 0.1 M TBAP
This positive shift results from the extended
p-system of the benzoporphyrins and distortion
of the macrocycle [63, 64].
A comparison between potentials for the first
reduction and first oxidation of (TpCH3PP)FeCl
1a, butano(TpCH3PP)FeCl 2a and benzo-
(TpCH3PP)FeCl 3a in pyridine is shown in Fig.12.
The first reduction of butano(TpCH3PP)FeCl
2a is negatively shifted by 340 mV compared
to the same electrode reactions of 1a, while the
first oxidation is negatively shifted by 510 mV.
The first reduction and first oxidation of 3a are
also positively shifted compared to the related
redox reactions of 2a, with the magnitude of the
shift being 50 mV for oxidation and 470 mV for
reduction.
Effect of central metal ions
Table 2 lists potentials for the first oxidation
and first reduction of (TPP)M, butano(TPP)M
and benzo(TPP)M (M = FeIIICl, CoII or CuII)
in CH2Cl2. The site of electron transfer is
given in parenthesis as M or R to indicate a
metal or ring-centered electron transfer. The
values of DEox1 and DEred1 shown in the table
are the potential differences between the first
oxidations and first reductions of butano(TPP)M
or benzo(TPP)M and (TPP)M. As seen from the
table, all the DEox1 values are negative for the
butano(TPP)M and benzo(TPP)M derivatives,
Fig. 12. Cyclic voltammograms showing the first reduction and first
oxidation of (a) (TpCH3PP)FeCl 1a, (b) butano(TpCH3PP)FeCl 2a and
(c) benzo(TpCH3PP)FeCl 3a in CH2Cl2 containing 0.1 M TBAP
indicating that the butano and benzo groups
Effect of the butano- and benzo-substituents
both lead to an easier oxidation of the porphyrins
compared to (TPP)M. The DEred1 values are also
negative for butano(TPP)M and consistent with harder
It was earlier demonstrated that adding fused b,b′-
butano or b,b′-benzo groups on a porphyrin macrocycle
Copyright © 2018 World Scientific Publishing Company
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W. XU ET AL.
Table 2. Comparisons of potentials (V vs. SCE) for the first oxidation
and reduction between the (TPP)M, butano(TPP)M and benzo(TPP)M
(M = FeIIICl, CoII or CuII) in CH2Cl2 containing 0.1 M TBAP
prepared according to procedures in the literature
[49–51] and are described below. MS spectra of the
porphyrins are shown in Supporting information
(see Figs S8–S10).
M
b–b′-sub
1st oxa
DEox1 (V)b
1st reda
DEred1 (V)b
Fe(III)
none
1.20 (R)
0.67 (R)
0.69 (R)
0.70 (M)
0.39 (R)
0.44 (M)
1.04 (R)
0.49 (R)
0.55 (R)
-0.36 (M)
-0.72 (M)
-0.19 (M)
-0.88 (M)
-1.02 (M)
-0.61 (M)
-1.28 (R)
-1.55 (R)
-1.22 (R)
Synthesis of (TpYPP)FeCl 1a–1c [53]
butano
benzo
none
-0.53
-0.51
-0.36
.
(TpYPP)H2(0.075mmol)andexcessFeCl2 4H2O
+0.17
(0.75 mmol) were refluxed in N,N-dimethyl-
formamide under nitrogen as the progress of the
reaction was monitored by UV-vis spectroscopy.
After 1h, the resulting solution was washed with HCl
(4.7 wt%, 200 mL) and H2O (200 mL), extracted
with CH2Cl2 and then dried over Na2SO4. The solvent
was removed under vacuum. The raw product was
chromatographed with a silica gel column using a
mixture of ethyl acetate/dichloromethane as eluent
(v/v = 1/2). The brown fraction was collected and
roto-evaporated to dryness.
Co(II)c
Cu(II)d
butano
benzo
none
-0.31
-0.26
-0.14
+0.27
butano
benzo
-0.55
-0.49
-0.27
+0.06
a M and R represent a metal-centered and porphyrin ring-centered electron
transfer process, respectively.
b Potential shifts from corresponding reactions of the non-b–b′-substituted
compound.
(TpCH3PP)FeCl 1a. Yield, 47.2 mg, 83%;
UV-vis (CH2Cl2), lmax = 381, 418, 511 nm; MS
(MALDI-TOF), m/z calcd for [M – Cl]+ 724.23;
found 724.43.
c Data taken from Ref. 50.
d Data taken from Ref. 51.
(TPP)FeCl 1b. Yield, 46.0 mg, 87%; UV-vis
(CH2Cl2), lmax = 378, 417, 508 nm; MS (MALDI-
TOF), m/z calcd for [M – Cl]+ 668.17; found 668.29.
(TpClPP)FeCl 1c. Yield, 54.0 mg, 86%; UV-vis
(CH2Cl2), lmax = 380, 415, 510 nm; MS (MALDI-TOF),
m/z calcd for [M – Cl]+ 804.01; found 806.22.
reductions occurring for the Fe(III), Co(II) and Cu(II)
butanoporphyrins. However, positive DEred1 values are
seen for all the benzo(TPP)M derivatives, indicating that
these compounds are easier to reduce in CH2Cl2 than the
non-b,b′-substituted porphyrins (TPP)M under the same
solution conditions.
Synthesis of butano(TpYPP)FeCl 2a–2c [49, 54]
The results discussed above indicate that the effect of
butano and benzo groups on the first oxidation and first
reductionfollowthesametrendasalltheFe(III),Co(II)and
Cu(II) porphyrins. However, the magnitude of the effect
varieswiththecentralmetalions. Forexample, Cu(II)por-
phyrins have almost the same DEox1 values (-0.55 V for
butano(TPP)Cu and -0.49 V for benzo(TPP)Cu) as that
of Fe(III) derivatives (DEox1 = -0.53 for butano(TPP)FeCl
and -0.51V for benzo(TPP)FeCl).This is probably because
the site of electron transfer for the first oxidation is the
same on the porphyrin macrocycle for all the Fe(III) and
Cu(II) porphyrins. In the case of Co(II) porphyrins, the
DEox1 values are smaller (-0.31 for the butano(TPP)Co
and -0.26 V for benzo(TPP)Co) than that of Fe(III) and
Cu(II) porphyrins, which may be due to the fact that the
oxidation sites of the cobalt(II) derivatives differ from the
Fe(III) and Cu(II) porphyrins.
.
Excess FeCl2 4H2O (0.3 mmol) was added into a
N,N-dimethylformamide solution which contained
butano(TpYPP)H2 (0.03 mmol). The reaction solution
was refluxed under nitrogen for 2 h and then washed with
HCl (4.7 wt%, 200 mL) and H2O (200 mL). The mixture
was extracted with CH2Cl2 and dried over Na2SO4.
After the solvent was evaporated under vacuum, the raw
product was purified on a neutral alumina column using
CH2Cl2 as eluent. The brown fraction was collected and
evaporated under vacuum to dryness.
Butano(TpCH3PP)FeCl 2a. Yield, 16.7 mg, 57%;
UV-vis (CH2Cl2), lmax = 399, 431 nm; MS (MALDI-
TOF), m/z calcd for [M – Cl]+ 941.06; found 941.13.
Butano(TPP)FeCl 2b. Yield, 10.2 mg, 37%; UV-vis
(CH2Cl2), lmax = 396, 429 nm; MS (MALDI-TOF), m/z
calcd for [M – Cl]+ 884.95; found 885.05.
Butano(TpClPP)FeCl 2c.Yield, 7.9 mg, 25%; UV-vis
(CH2Cl2), lmax = 394, 430 nm; MS (MALDI-TOF), m/z
calcd for [M – Cl]+ 1022.72; found 1022.92.
EXPERIMENTAL
Chemicals
Synthesis of benzo(TpYPP)FeCl 3a–3c [49, 54]
.
Dichloromethane (CH2Cl2, ≥99.8%), pyridine (Py,
≥99.9%) and tetra-n-butylammonium perchlorate (TBAP,
≥99.0%) were purchased from Sigma-Aldrich and used
as received. The investigated Fe(III) porphyrins were
Excess FeCl2 4H2O (0.3 mmol) was added into
a solution of benzo(TpYPP)H2 (0.03 mmol) in N,N-
dimethylformamide. The mixture was refluxed under
nitrogen for 2 h and then cooled to room temperature.
Copyright © 2018 World Scientific Publishing Company
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SYNTHESIS, ELECTROCHEMICAL AND SPECTROELECTROCHEMICAL CHARACTERIZATION OF IRON(III)
13
The reaction solution was diluted with CHCl3 and
and 21071067), the Jiangsu University Foundation (Grants
15JDG131 and 05JDG051), the China Postdoctoral Sci-
ence Foundation (Grant 2017M611707) and the Robert
A. Welch Foundation (K.M.K., Grant E-680).
washed with HCl (4.7 wt%, 200 mL) and H2O (200 mL).
After drying with Na2SO4, the solution was evaporated
with vacuum to remove the solvent. The raw product
was purified on a neutral alumina column using CHCl3
as eluent. The green fraction was collected and roto-
evaporated to dryness.
Benzo(TpCH3PP)FeCl 3a. Yield, 4.0 mg, 14%;
UV-vis (CH2Cl2), lmax = 436, 606 nm; MS (MALDI-
TOF), m/z calcd for [M – Cl]+ 924.93; found 924.88.
Benzo(TPP)FeCl 3b. Yield, 16.3 mg, 60%; UV-vis
(CH2Cl2), lmax = 430, 606 nm; MS (MALDI-TOF): m/z
calcd for [M – Cl]+ 868.23; found 868.68.
Supporting information
Figures S1–S10 are given as supplementary material.
This material is available free of charge via the internet at
http://www.worldscinet.com/jpp/jpp.shtml.
REFERENCES
Benzo(TpClPP)FeCl 3c.Yield, 16.2 mg, 52%; UV-vis
(CH2Cl2), lmax = 434, 607 nm; MS (MALDI-TOF), m/z
calcd for [M – Cl]+ 1006.59; found 1006.65.
1. Rao H, Schmidt LC, Bonin J and Robert M. Nature
2017; 548: 74–77.
2. Zhang W, Lai W and Cao R. Chem. Rev. 2017; 117:
3717–3797.
Instrumentation
3. Chatterjee S, Sengupta K, Mondal B, Dey S and
Dey A. Acc. Chem. Res. 2017; 50: 1744–1753.
4. Ascenzi P and Brunori M. J. Porphyrins Phthalo-
cyanines 2016; 20: 134–149.
5. Costentin C, Robert M and Saveant JM. Acc. Chem.
Res. 2015; 48: 2996–3006.
6. Samanta S, Das PK, Chatterjee S and Dey A. J. Por-
phyrins Phthalocyanines 2015; 19: 92–108.
7. Manbeck GF and Fujita E. J. Porphyrins Phthalo-
cyanines 2015; 19: 45–64.
8. Oszajca M, Franke A, Brindell M, Stochel G and
Eldik R. Coord. Chem. Rev. 2016; 306 (Part 2):
483–509.
9. Boehm P and Groeger H. ChemCatChem 2015; 7:
22–28.
10. Oohora K and Hayashi T. Curr. Opin. Chem. Biol.
2014; 19: 154–161.
11. Zhu WH, Ni C, Liang LL, Li JW, Li MZ, Ou ZP and
Kadish KM. J. Porphyrins Phthalocyanines 2014;
18: 519–527.
Cyclic voltammetry was carried out at 298 K using
an EG&G Princeton Applied Research (PAR) 173
potentiostat/galvanostat. A homemade three-electrode
cell was used for cyclic voltammetric measurements and
consisted of a glassy carbon working electrode, a platinum
counter electrode and a homemade saturated calomel
reference electrode (SCE). The SCE was separated
from the bulk of the solution by a fritted glass bridge
of low porosity, which contained the solvent/supporting
electrolyte mixture.
Thin-layer UV-vis spectroelectrochemical experi-
ments were performed using a home-built thin-layer
cell, which had a transparent platinum net working
electrode. Potentials were applied and monitored with
an EG&G PAR Model 173 potentiostat. High purity N2
from Trigas was used to deoxygenate the solution and
kept over the solution during each electrochemical and
spectroelectrochemical experiment.
12. Zhang Y, Shen W, Ou ZP, Zhu WH, Fang YY and
Kadish KM. Electroanalysis 2013; 25: 1513–1518.
13. Azcarate I, Costentin C, Robert M and Saveant JM.
J. Am. Chem. Soc. 2016; 138: 16639–16644.
14. Sengupta K, Chatterjee S and Dey A. ACS Catalysis
2016; 6: 6838–6852.
15. Choi J, Benedetti TM, Jalili R, Walker A, Wallace
GG and Officer DL. Chem. —Eur. J. 2016; 22:
14158–14161.
16. Römelt C, Song J, Tarrago M, Rees JA, Gastel M,
Weyhermüller T, DeBeer S, Bill E, Neese F and Ye
S. Inorg. Chem. 2017; 56: 4745–4750.
17. Mihara N, Yamada Y, Takaya H, Kitagawa Y,
Aoyama S, Igawa K, Tomooka K and Tanaka K.
Chem. —Eur. J. 2017; 23: 7508–7514.
CONCLUSION
b,b′-butano and b,b′-benzo substituted Fe(III) tetra-
arylporphyrins were synthesized and the electrochemical
and spectroelectrochemical properties of the porphyrin
characterized in CH2Cl2 and pyridine containing 0.1 M
TBAP. The Fe(III) porphyrins can be singly, doubly or
triply reduced to generate Fe(II), Fe(II) porphyrin p-anion
radicals or Fe(I) anions and dianions with the exact form of
thegeneratedreductionproductdependinguponthesolvent
utilized and the potential applied during electroreduction.
The b,b′-butano and b,b′-benzo substituents of Fe(III)
porphyrins have a significant effect on the UV-vis spectra
and the reduction/oxidation potentials.
18. Rana A, Mondal B, Sen P, Dey S and Dey A. Inorg.
Chem. 2017; 56: 1783–1793.
19. Ambre RB, Daniel Q, Fan T, Chen H, Zhang B,
Wang L, Ahlquist MSG, Duan L and Sun L. Chem.
Commun. 2016; 52: 14478–14481.
Acknowledgments
We gratefully acknowledge support from the National
Natural Science Foundation of China (Grants 21501070
Copyright © 2018 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2018; 22: 13–14

14
W. XU ET AL.
20. Azcarate I, Costentin C, Robert M and Saveant JM.
J. Phys. Chem. C 2016; 120: 28951–28960.
21. Kim S and Kim H. Catalysis Today 2017; 295:
119–124.
22. Elhamifar D, Badin P and Karimipoor G. J. Colloid
Interface Sci. 2017; 499: 120–127.
23. Zhao R, Wang J, Zhang D, Sun Y, Han B, Tang N,
Wang N and Li K. Appl. Cat., A2017; 532: 26–31.
24. Deng X, Fang Y, Lin S, Cheng Q, Liu Q and Zhang
X. ACS Appl. Mater Interfaces 2017; 9: 3514–3523.
25. Zanatta LD, Barbosa IA, Zanardi FB, de Sousa
Filho PC, Bolzon LB, Ramos AP, Serra OA and
Iamamoto Y. RSC Adv. 2016; 6: 104886–104896.
26. Rebelo SLH, Silva AMN, Medforth CJ and Freire
C. Molecules 2016; 21: 481/1–481/12.
27. Nakamura M, Ohgo Y and Ikezaki A. In Handbook
of Porphyrin Science, Vol. 7, Kadish KM, Smith
KM and Guilard R. (Eds.), World Scientific: New
Jersey, 2010, pp. 1–146.
43. Kadish KM, Bottomley LA and Beroiz D. Inorg.
Chem. 1978; 17: 1124–1129.
44. Kadish KM, D’Souza F, Villard A, Van Caemel-
becke E, Bianco P, Antonini A and Tagliatesta P.
Inorg. Chem. 1994; 33: 5169–5170.
45. Kadish KM, Van Caemelbecke E and Royal G.
In The Porphyrin Handbook, Vol. 8, Kadish KM,
Smith KM and Guilard R (Eds.) Academic Press:
San Diego, 2000; pp. 1–144.
46. Yang SB, Sun B, Ou ZP, Meng DY, Lu GF, FangYY
and Kadish KM. J. Porphyrins Phthalocyanines
2013; 17: 857–869.
47. Rahman MH and Ryan MD. Inorg. Chem. 2017;
56: 3302–3309.
48. Carvalho CMB, Brocksom TJ and de Oliveira KT.
Chem. Soc. Rev. 2013; 42: 3302–3317.
49. Ikeue T, Handa M, Chamberlin A, Ghosh A, Ongayi
O, Vicente MGH, Ikezaki A and Nakamura M.
Inorg. Chem. 2011; 50: 3567–3581.
28. Mittra K, Singha A and Dey A. Dalton Transactions
2016; 45: 18796–18802.
50. Ye L, Ou Z, Fang Y, Xue S and Kadish KM. Inorg.
Chem. 2017; 57: 13613–13626.
29. Weiss R, Gold A, Trautwein AX and Terner J. In
The Porphyrin Handbook, Vol. 4. Kadish KM,
Smith KM and Guilard R. (Eds.), Academic Press:
San Diego, 2000; pp. 65–96.
30. Fukuzumi S, Nakanishi I, Tanaka K, Suenobu T,
Tabard A, Guilard R, Van Caemelbecke E and
Kadish KM. J. Am. Chem. Soc. 1999; 121: 785–790.
31. Kadish KM, Autret M, Ou ZP, Tagliatesta P, Boschi
T and Fares V. Inorg. Chem. 1997; 36: 204–207.
32. Kadish KM, Van Caemelbecke E, D’Souza F, Med-
forth CJ, Smith KM, TabardA and Guilard R. Inorg.
Chem. 1995; 34: 2984–2989.
33. Kadish KM, D’Souza F, Van Caemelbecke E, Vil-
lard A, Lee JD, Tabard A and Guilard R. Inorg.
Chem. 1993; 32: 4179–4185.
34. Kadish KM, Tabard A, Lee W, Liu YH, Ratti C and
Guilard, R. Inorg. Chem. 1991; 30: 1542–1549.
35. Kadish KM, Boisselier-Cocolios B, Simonet B,
Chang D, Ledon H and Cocolios P. Inorg. Chem.
1985; 24: 2148–2156.
36. Bottomley LA, Olson L and Kadish KM. Adv.
Chem. Ser. 1982; 201: 279–311.
37. Kadish KM. In Iron Porphyrins, Part 2. Lever ABP
and Gray HB (Eds.) Addison-Wesley Publishing
Co: London, 1983; pp. 161–249.
38. Bottomley LA and Kadish KM. Inorg. Chem. 1981;
20: 1348–1357.
39. Kadish KM and Bottomley LA. Inorg. Chem. 1980;
19: 832–836.
51. Ye L, Ou Z, FangY, Xue S, SongY, Wang L, Wang M
and Kadish KM. RSC Adv. 2015; 5: 77088–77096.
52. Chen P, Finikova OS, Ou Z, Vinogradov SA and
Kadish KM. Inorg. Chem. 2012; 52: 6200–6210.
53. Lindsey JS. In The Porphyrin Handbook, Vol. 1,
Kadish KM, Smith KM and Guilard R. (Eds.), Aca-
demic Press: San Diego, 2000; pp. 62–65.
54. Finikova OS, Cheprakov AV, Beletskaya IP, Carroll
PJ and Vinogradov SA. J. Org. Chem. 2004; 69:
522–535.
55. Kadish KM, Van Caemelbecke E, D’Souza F, Lin
M, Nurco DJ, Medforth CJ, Forsyth TP, Krat-
tinger B, Smith KM, Fukuzumi S, Nakanishi I and
Shelnutt JA. Inorg. Chem. 1999; 38: 2188–2198.
56. Lexa D, Mispelter J and Saveant J-M. J. Am. Chem.
Soc. 1981; 103: 6806–6812.
57. Gueutin C, Lexa D, Momenteau M and Saveant
J-M. J. Am. Chem. Soc. 1990; 112: 1874–1880.
58. ZhangY, Shen W, Ou Z, Zhu W, FangY and Kadish
KM. Electroanalysis 2013; 25: 1513–1518.
59. Tagliatesta P, Li J, Autret M, Van Caemelbecke E,
VillardA, D’Souza F and Kadish KM. Inorg. Chem.
1996; 35: 5570–5576.
60. Pellegrino J, Hübner R, Doctorovich F and Kaim
W. Chem. —Eur. J. 2011; 17: 7868–7874.
61. Kadish KM, Shao J, Ou Z, Zhan R, Burdet F, Barbe
JM, Gros CP and Guilard R. Inorg. Chem. 2005; 44:
9023–9038.
62. Kadish KM, Larson G, Lexa D and Momenteau M.
J. Am. Chem. Soc. 1975; 97: 282–288.
63. Finikova OS, Cheprakov AV, Carroll PJ, Dalosto
S and Vinogradov SA. Inorg. Chem. 2002; 41:
6944–6946.
40. Kadish KM and Larson G. Bioinorg. Chem. 1977;
7: 95–105.
41. Kadish KM and Bottomley LA. J. Am. Chem. Soc.
1977; 99: 2380–2382.
42. Kadish KM, Morrison MM, Constant LA, Dick-
ens L and Davis DG. J. Am. Chem. Soc. 1976; 98:
8387–8390.
64. Cheng RJ, Chen YR, Wang SL and Cheng C. Y.
Polyhedron 1993; 12: 1353–1360.
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