Synthesis and properties of β-brominated metal complexes of meso-triphenylcorrole

Article abstract of DOI:10.1134/S1070363214040239

Spectral properties and chemical stability of Mn(III), Mn(IV), Fe(III), Fe(IV), and Cu(III) complexes of β-octabromotriphenylcorrole [(β-Br)₈(ms-Ph)₃Cor], synthesized from β-unsubstituted compounds by their reaction with molecular br

Full text of DOI:10.1134/S1070363214040239

ISSN 1070-3632, Russian Journal of General Chemistry, 2014, Vol. 84, No. 4, pp. 737–744. © Pleiades Publishing, Ltd., 2014.
Original Russian Text © N.M. Berezina, Vu Thi Thao, D.R. Karimov, R.S. Kumeev, A.V. Kustov, M.I. Bazanov, D.B. Berezin, 2014, published in Zhurnal
Obshchei Khimii, 2014, Vol. 84, No. 4, pp. 661–669.
Synthesis and Properties of β-Brominated Metal Complexes
of meso-Triphenylcorrole
N. M. Berezinaa, Vu Thi Thaoa, D. R. Karimova, R. S. Kumeevb,
A. V. Kustovb, M. I. Bazanova, and D. B. Berezina
a Ivanovo State University of Chemistry and Technology, pr. Sheremetevskii 7, Ivanovo, 153000 Russia
е-mail: sky_berezina@rambler.ru
b G.A. Krestov Institute of Solution Chemistry, Russian Academy of Sciences, Ivanovo, Russia
Received May 14, 2013
Abstract—Spectral properties and chemical stability of Mn(III), Mn(IV), Fe(III), Fe(IV), and Cu(III)
complexes of β-octabromotriphenylcorrole [(β-Br)8(ms-Ph)3Cor], synthesized from β-unsubstituted compounds
by their reaction with molecular bromine, were studied. Cyclic voltammetry, electron microscopy, and X-ray
spectral microanalysis were used to obtain electrochemical characteristics of metal corroles M(β-Br)8(ms-Ph)3Cor
and gain insight into the surface texture of active catalysts on the basis of metal corroles. The electron-acceptor
β-bromine substitution in the MCor macrocycle shifts the equilibrium in electron-donor solvents to lower
oxidation states of the metals and also stabilizes manganese and destabilizes copper complexes in the proton-
donor medium НОАс–H2SO4. The electrocatalytic activity of the complexes in the reduction of molecular
oxygen depends on the nature of the ligand and increases in the order Mn ≤ Cu << Fe in the case of β-
octabrominated macrocycles. The character of distribution of active centers on the surface of the catalysts was
established for the first time.
Keywords: metal corrole, bromination, electrochemical reduction, catalytic activity
DOI: 10.1134/S1070363214040239
The structural and electronic features of corroles
H3Cor and their metal complexes MCor (compounds
I–VI) predetermine the versatile structures and high
reactivity of such macrocycles and their potential
efficiency as catalysts in redox reactions and chemical
sensors in molecular recognition of small molecules
[1]. The main interrelated characteristics of these
compounds, which determine their unique features,
including catalytic activity [1–3], are, first, ability of
macrocycles to stabilize metals having unusual
oxidation degrees in complexes with trianionic ligands,
and, second, formation of ligand-localized radicals
МCor due to the noninvolvement of ligand orbitals in
coordination (non-innocence effect), which results in a
certainly unclear oxidation state of metals in the re-
sulting complexes [4, 5]. The metals atoms in such
molecules are prone to redox reactions, and the
complexes in themselves exhibit a high catalytic ac-
tivity [1]. As previously shown [6, 7], exhaustive β-
bromination of tetra-meso-phenylporphyrins (Н2Р)
substantially enhances their catalytic and electro-
catalytic redox activity. Dodecasubstituted Н2Р macro-
ring experiences a strong out-of-plane distortion,
which [6], along with the electron-acceptor effect of
halogen substituents, was considered [6] as the main
reasons of the enhanced catalytic activity. Unlike Н2Р
and МР, metal corroles (H3Cor) are less sensitive
steric effects of β- and meso-substituents in undeca-
substituted molecules, both in crystal and in solution.
This conclusion was based on the results of X-ray dif-
fraction (XRD) analysis [8, 9] and quantum-chemical
computations [4, 10, 11], as well as correlation of the
1
electronic absorption spectra (UV-vis) and Н NMR
spectra of β- (or meso-) and undecasubstituted (β-R =
CH3, Br, F) metal corroles (M = CoIII, MnIV, CuIII,
FeIV) [4, 12]. Thus, the fact that the spectra of poly-
substituted corroles differ from those of β- or meso-
substituted derivatives is likely to be largely explained
by the electronic effects of β-substituents.
In the present work, aimed at analyzing the effect
of β-substitution on the physicochemical properties of
737

738
BEREZINA et al.
Scheme 1.
R
Br
R
Br
R
R
Br
Br
R
R
Br
N
N
N
N
NH
N
N
OH
M
HN
Br
R
Br
R
Br
I_VI
VII
I: M = (DMF)MnIII; R = Н, II: M = (Cl)FeIV; R = Н, III: M = CuIII; R = Н, IV: M = (Py)MnIII; R = Br, V: M = (Cl)FeIV; R =
Br, VI: M = CuIII; R = Br.
macroheterocycles, we synthesized MnIII, FeIV, and
CuIII complexes of β-octabromo-meso-triphenylcorrole
(1) Br2, CHCl3
M(ms-Ph)3Cor
M(β-Br)8(ms-Ph)3Cor. (2)
(complexes IV–VI) and studied their spectral
characteristics, stability in proton-donor media, and
catalytic activity in the electrochemical reduction of
molecular oxygen. The resulting data were compared
with those for the corresponding β-unsubstituted
complexes I–III [2] (Scheme 1).
(2) Py
IV–VI
The UV-vis spectra of metal corroles I–VI in non-
coordinating media (C6H6, CHCl3) show a Soret band
(385–445 nm) and weak absorption bands in the
visible range. In electron-donor solvents (DMF, Py),
the visible spectra of the metal complexes show well-
defined Q bands at 535–670 nm for CuIII and MnIII
corroles and 560–570 nm for iron corroles. The Soret
and QI bands in the UV-vis spectra of undecasubstituted
complexes, except for FeIV complexes, are shifted red
with respect to those in the spectra of metal corroles I–
III by 3–34 and 7–25 nm, respectively (Table 1).
Unlike metal porphyrins (МР), corrole ligands
could not still be obtained from complexes by the
dissociation reaction (1); H3Cor could only be obtained
from certain manganese(IV), iron(IV), and copper(III)
complexes [11, 13]. This is associated with the fact
that corroles stabilize metals in high oxidation states
[14], and, therefore, MCor the dissociation can be
accompanied by the oxidation of ligands into phlorin-
type compounds (for example, isocorrole VII), or
other molecules by the released metal ion [13].
Based on the abundant evidence on the state of
metal porphyrins in coordinating solvents (Solv) [18,
19], it would be logical to suggest that the changes in
the UV-vis spectra are associated with additional coor-
dination of Solv with the metal atom [reaction (3)]. At
the same time, extra coordination of metal porphyrins
usually shifts their absorption maxima by no more than
5–20 nm, it gives rise to no electron transitions and
takes place at low Solv concentrations. In the case of
MCor, the structure of the absorption spectrum
changes essentially (Fig. 1, Table 1), and, for example,
when a noncoordinating solvent is replaced by an
electron-donor one, changes in the spectra of
manganese complexes I and IV are complete at the
concentration of the electron donor of about 6 M.
n+
Solv
Mn+Cor + 3H+Solv
H3Cor + M
.
(1)
Bromination of a meso-triphenyl-substituted ligand
H3Cor, too, does not lead to the desired result, yielding
isocorrole [9, 13]. Therefore, to synthesize undecasub-
stituted β-octabromotriphenylcorrole complexes IV–
VI, we made use of an approach involving bro-
mination of meso-triphenylcorrole complexes I–III by
molecular bromine [reaction (2)] [13]. The indi-
viduality and purity of complexes IV–VI was con-
1
firmed by UV-vis and Н NMR [4, 11, 15, 16] and X-
ray spectral microanalysis (Table 1, Figs. 1–3).
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SYNTHESIS AND PROPERTIES OF β-BROMINATED METAL COMPLEXES
739
Table 1. Electronic absorption spectra and X-ray spectral microanalysis data for complexes I–VI
Soret band, nm
λIII, nm
(log ε)
Br/M
ratio
Compound
Solvent
λII, nm (log ε)
λI, nm (log ε)
(log ε)
Cu(ms-Ph)3Cor (III) [17]
СНCl3
DMF
411 (4.92)
431
–
–
–
–
537 (3.74)
535, 576
619 (3.51)
607, 776 w
–
–
Mn(ms-Ph)3Cor (I) [17]
Fe(ms-Ph)3Cor (II) [17]
СНCl3
DMF
433 (4.57)
589 (3.54)
574 (3.84)
–
401 (4.42), 436
(4.48), 462 sh
(4.27), 494 (4.14)
652 (3.95)
СНCl3
401 (4.56)
397 (4.61)
445 (4.78)
437 (4.82)
–
602 w (3.99)
–
DMF
562 (4.19)
602 w (4.10) 728 w (3.92)
522 sh (4.19) 642 w (3.88)
Cu[(β-Br)8(ms-Ph)3Cor] (VI) СНCl3
–
–
10.9
DMF
537 w (4.12), 622 w (4.08)
587 (4.12)
Mn[(β-Br)8(ms-Ph)3Cor] (IV) СНCl3
386 (4.63), 419
(4.63)
–
–
–
–
614 sh (3.94), 660
sh (3.81), 757 w
(3.64)
9.8
8.0
DMF
392 (4.57), 440
(4.63); 464 w
(4.53), 497 (4.61)
556 w (4.31) 619 w (4.27), 669
(4.40)
Fe[(β-Br)8(ms-Ph)3Cor] (V)
СНCl3
386 (4.69)
397 (4.65)
560 w (3.95) 786 w (3.50)
DMF
546 w (4.22) 567 (4.23)
770 w (3.94)
MP + nSolv ⇄ (Solv)nMP.
(3)
[11, 20]. Complexes МIIICor with characteristic UV-vis
spectra (Fig. 1b) are usually formed during synthesis
via complex formation in electron-donor media
(Solv = DMF, Py; М = Mn, Fe, Cu). Treatment of iron
and manganese complexes with dilute solutions of
acids (HOAc, HCl) results in a fast shift of the
In the case of corrole complexes with metals
capable of undergoing redox reactions, formation of
extra complexes or their dissociation is accompanied
by a change in the valence state of the metal atom
А
А
(а)
(b)
λ, nm
λ, nm
Fig. 1. Electronic absorption spectra of (a) Cu(β-Br)8(ms-Ph)3Cor (VI) and (b) Mn(β-Br)8(ms-Ph)3Cor (IV) in (1) CHCl3 and
(2) DMF.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 84 No. 4 2014

740
BEREZINA et al.
(а)
(b)
β-H
β-H
δ, ppm
δ, ppm
Fig. 2. Aromatic proton resonance region in the 1Н NMR spectrum of (a) Cu(ms-Ph)3Cor (III) and (b) Cu(β-Br)8(ms-Ph)3Cor (VI)
in CDCl3, 298 K.
equilibrium (Solv)МIII → (X)MIV, where Х is the acid
an intramolecular redox reaction (non-innocence
effect) [4, 5] to form (Cl)FeIVCor–· already during
chloroform extraction of the product from the reaction
mixture [17]. The rate of this transformation is
strongly dependent on the charge on the metal atom
and is much lower in β-octabrominated complexes IV
and V than in compounds I and II. The reverse process
takes place in the course of titration of a solution of
(X)MIVCor–· in an inert solvent; in this case, the
equilibrium constant is difficult to determine, because
several processes occur concurrently. The mechanism
of the process is, too, unknown. Apparently, the first,
fast stage involves coordination of Solv, and then, at
the limiting stage, cleavage of the Х– anion takes place
[reaction (4)].
←
anion. The dissociation of extra complex
(Solv)МnIIICor in weakly or noncoordination solvents,
especially if the solvent is an acid and the medium
contains its anions (CHCl3), is a slow process, whereas
Fe(III) complexes lose extra ligand Solv and undergo
I, V
(X–)MIVCor– · + Solv ⇄ (X–)(Solv)MIVCor– ·
–X–
⇄ (Solv)MIIICor.
(4)
On solvent change, equilibrium (5) in complexes
CuIIICor [4, 14] shifts only slightly, as evidenced by
minor changes in the EAS spectrum of complex III
(Table 1). With compound VI, the spectral pattern
changes more essentially (Fig. 1a), and, therewith, eight
electron-acceptor substituents stabilize the lowest valence
state of the metal ions and the radical cation state of
the ligand (non-innocence effect) [equilibrium (5)]
[4, 5, 17]. It is unlikely that the spectral changes are
associated with Solv extra coordination, because
0.4 0.2 0.0 –0.2 –0.4 –0.6 –0.8 –1.0 –1.2 –1.4
Е, V
Fig. 3. Current−voltage curve for the electrode coated with
(Cl)FeIV(β-Br)8(ms-Ph)3Cor–· (V) in 0.1 М KОН (аrgon).
Scan rate 0.02 V/s.
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SYNTHESIS AND PROPERTIES OF β-BROMINATED METAL COMPLEXES
741
copper(II) does not tend to form octahedral complexes
[7].
[reaction (1)]. Unlike what proved possible with most
МРs, in the case of MCor we could measure dis-
sociation kinetics for Mn(IV) compounds which are
rapidly formed, when (Solv)MnIIICor are dissolved in
acid mixtures [reaction (6)]. With CuIIICor, equilib-
rium (1) is shifted to its formation, and, therefore,
dissociation normally takes place only in highly acidic
media, and the complex can be formed again, when the
acid solution is diluted with the aim to isolate products
[13]. The state of iron corroles in acid solutions is still
an open problem, and it is to be solved in separate
research.
MIIICor ⇄ МIICor– ·.
(5)
The spectral (1H NMR) characteristics of corrole
complexes I–VI were detected in CDCl3 which
stabilizes higher oxidation states of metals (MnIV, FeIV,
and CuIII; MnIV is formed only after prolonged storage
1
of the solution). The H NMR spectrum of copper
complex III shows signals at 7.36–8.03 ppm in the
region of phenyl and β-pyrrole proton resonance. The
diamagnetism of compound III is evidence showing
that the oxidation state of the metal is +3. At the same
time, the corresponding copper(II) complexes with
porphyrins are paramagnetic [7, 17]. The equilibrium
between CuIIICor and CuIICor+· in CDCl3 at room
temperature is almost completely shifted to CuIIICor,
which agrees with published data [4, 13]. β-Octa-
bromine substitution in copper meso-triphenyl-corrole
complex III results in disappearance of the β-proton
signals, while the meso-phenyl proton signals at 7.46–
7.74 ppm are preserved (Fig. 2).
(Solv)MIIICor + HX ⇄ (X)MIVCor– · + Solv + H+.
(6)
The spectral kinetic study of the dissociation of
Mn(IV) and Cu(III) meso-phenyl-substituted corrole
complexes I and III in HOAc–H2SO4 mixtures showed
that the Cu(III) complex is more stable than the
Mn(IV) complex. The H2SO4 concentration required
for dissociation of CuIIICor in the HOAc–H2SO4
medium in the case of the more electron-donor
macrocycle III increases: 11.5 (III) > 5.0 (VI). No
selective formation of protonated ligands H4Cor+ or
(H4CorH)2+ from copper(III) complexes takes place
under the action of acids. Evidence for this conclusion
comes from the fact that the EAS spectra of the
reaction products do not coincide with the spectra of
corrole mono- and dications and are assignable to
hydroxyphlorin structures VII formed by side oxida-
tion reactions of the complexes [13].
The dissociation of (X)MnIVCor–· complexes I and
IV in the HOAc–H2SO4 system results in selective
formation of the dication H4CorH2+. Dissociation of
meso-substituted manganese corroles, unlike what is
characteristic of copper(III) complexes, is accelerated
by electron-donor substituents. Comparison of the
apparent rate constants of reaction (1), obtained by the
extrapolation of their concentration dependence to
c(H2SO4) 4 M, provides evidence showing that
1
The H NMR signals of paramagnetic Mn(IV) and
Fe(IV) complexes I and II appear in a wide range of
chemical shifts: from –42.3 to +33.9 ppm (I) and
from–41.1 to +25.2 ppm (II). Usually the signals of
complexes (X)FeIVCor–· with highly negative chemical
shifts are assignable to β protons of the electron-
excessive α,α-dipyrrole fragment and the signals with
positive chemical shifts, to the ortho (and para)
protons of the meso-phenyl rings. The 1Н NMR spectra
of manganese complexes were not assigned completely
[11]. β-Bromination of the macrorings results in
disappearance of the pyrrole proton signals at –43.28
and 34 ppm in the spectrum of complex IV and of the
upfield signals (δ < –10 ppm) in the spectrum of
compound V.
Further evidence for the composition of complexes
IV–VI, in particular, with the aim of establish their β-
bromination degree, we performed X-ray spectral
measurements of active mixtures of catalysts [2] on the
basis of these metal corroles. The results, even though
the measurement error was fairly high (about 25%),
showed that the М/Br ratio was ≥ 8 in all the com-
plexes (Table 1).
electron-acceptor β-octabromine substitution in
298
manganese corrole IV (k 0.252 × 10–3 s–1) makes the
app
metal complex about 7.5 times more stable than un-
substituted compound I. The same effect of sub-
stituents on stability was also observed in Mn(III) H2P
complexes [7, 21].
The high chemical and heat resistance of metal
corroles [17], along with unique structural features,
favor use of these compounds in catalysis. We estimated
the electronic effect of multiple β substituents (R = Br)
in metal corroles on their redox potential and activity
Corrole complexes with p and d elements, like
complexes with other macrocyclic aromatic ligands,
show a high kinetic stability to dissociation [7] and
dissociate exclusively in strongly proton-donor media
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742
BEREZINA et al.
Table 2. Potentials of redox reactions (Е1/2, V) on electrodes coated with Н2Р, Н3Cor, their β-octabromo derivatives, and
metal complexes I–VI at the scan rate of 0.02 V/s
Process I M4+ ↔ M3+ Process II M3+ ↔ M2+
Process III L ↔ L–
EIII EIII EIII
,
red/ox
Reeren-
ces
II
II
II
EIcat,
V
EIan, EIred/ox
,
E
,
E ,
E
,
,
cat
,
an
Compound
H2(ms-Ph)4P
E1/2(O2)
cat
an
red/ox
V
–
V
–
V
–
V
–
V
–
V
V
V
–
–1.081 –0.968 –1.025 –0.275 [22]
Co(ms-Ph)4P
0.130 0.260 0.200 –0.580 –0.480 –0.530 –1.210 –1.000 –1.110 –0.230 [22]
0.130 0.370 0.250 –0.870 –0.500 –0.690 –1.150 –0.920 –1.040 –0.160 [22]
Co(β-Br)8(ms-Ph)4P
H3(ms-Ph)3Cor
–
–
–
–
–
–
–1.088 –0.606 –0.847 –0.257
[2]
[2]
[2]
[2]
–
(DMF)MnIII(ms-Ph)3Cor (I)
(Cl)FeIV(ms-Ph)3Cor– · (II)
CuIII(ms-Ph)3Cor (III)
–0.333 0.118 –0.108 –0.668 –0.569 –0.619 –1.095 –0.969 –1.033 –0.160
–0.160 –0.075 –0.117 –0.875 –0.785 –0.830 –1.057 –0.605 –0.831 –0.122
–
–
–
–0.468 –0.309 –0.389 –1.106
–
–
–0.250
(Py)MnIII(β-Br8)(ms-Ph)3Cor (IV) 0.292 0.410 0.351 –0.528 –0.481 –0.505 –1.048 –0.604 –0.826 –0.236
(Cl)FeIV(β-Br)8(ms-Ph)3Cor– · (V) –0.008 0.003 –0.005 –0.842 –0.743 –0.793 –1.029 –0.610 –0.820 –0.130
–
–
CuIII(β-Br)8(ms-Ph)3Cor (VI)
–
–
–
–
–
–
–1.044 –0.602 –0.823 –0.226
in the electrochemical reduction of oxygen (Table 2)
[23].
The first stage is characterized by a high degree of
reversibility (Fig. 3). With Mn(β-Br)8(ms-Ph)3Cor in
an alkaline solution (Table 2), we observed two
reversible maxima corresponding the reductions MnIV–
MnIII (Ecat 0.351 V) and MnIII–MnII (Ecat –0.505 V). In
the case of CuIII(β-Br)8(ms-Ph)3Cor, no Cu(III)–Cu(II)
reduction was detected, even though in the β-
unsubstituted copper(III) complex it is observed
–0.389 V [2].
The electrochemical characteristics of undecasub-
stituted complexes IV–VI, as measured in 0.1 М
aqueous KОН under argon, differ from those of β-
unsubstituted compounds I–III. The potentials of
[M(β-Br)8(ms-Ph)3Cor] in all the observed redox
processes are shifted to positive values with respect to
those for β-unsubstituted metal meso-triрhenylcorroles
[2] and β-octabromotetrphenylporphyrin complexes
(Table 2) [22]. At the same time, β-octabromination in
Co(ms-Ph)4P, unlike what takes place in corroles,
decreases the potentials of those redox processes that
involve the ligand and not the metal (Table 2) [22],
which may be associated with the spatial distortion of
the macrocycle. The electrochemical reduction potential
of metal corroles IV–VI is lower by 220–285 mV
compared to structurally similar Н2Р complexes (Table 2).
The electrochemical reduction order of metals
(МIII–МII) in β-unsubstituted complexes I–III parallels
the order of dissociation rates of the complexes in the
presence of the reducer SnCl2 (Cu > Mn > Fe) [24, 25].
Upon saturation of the aqueous alkaline solution
with molecular oxygen, the I, E-curves demonstrate a
considerable rise of current in the potential range
–(0.1–0.4) V, which is associated with the
electrochemical reduction of O2 on the catalyst-
modified electrode surface (Table 2). The electro-
catalytic activity of a sample is judged about by the
half-wave reduction potential of molecular oxygen
E1/2(О2) [2, 22] (Table 2).Analysis of the E1/2(О2)
values for compounds I–V allows us to conclude that
the β-bromination of complexes I–III to form undeca-
substituted macrocycles does not always positively
In terms of the metal complex electrocatalysis, the
most important redox processes are those occurring at
low potentials and involving catalyst metal centers
[23]. Metal-centered redox processes were observed in
Fe(β-Br)8(ms-Ph)3Cor (V) at Ered/ox –0.005 V (FeIV–
FeIII reduction) and Ered/ox –0.793 V (FeIII–FeII
reduction), like in unsubstituted complex II (Table 2).
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SYNTHESIS AND PROPERTIES OF β-BROMINATED METAL COMPLEXES
743
(a)
(b)
20
15
10
5
0
10 μm
Distance, μm
Fig. 4. (a) Microscopic image of the surface of the active catalytic mass on the basis of (Cl)FeIV(β-Br)8(ms-Ph)3Cor–· (V) and
(b) scanning of its atomic composition along the line shown in the image: (on a dark backround) Fe signal and (on a light
background) Br signal.
affect the electrocatalytic activity, unlike what occurs
in МРs with a similar type of functional substitution
(Table 2), which is consistent with the electron-
acceptor properties of bromine substituents in the
absence of the macrocycle distortion effect [2]. β-
Bromination strongly increases the electrochemical
reduction potential of oxygen E1/2(О2) only in copper
complex VI; in iron complex V, the E1/2(О2) value
remains unchanged, whereas in manganese complex
IV, it, by contrast, strongly decreases. Thus, the electro-
catalytic activity of tetrapyrroles IV–VI increases in
the order Mn ≤ Cu < Fe. As previously mentioned, the
activity order of metals in the electrochemical reduce-
tion of oxygen varies depending on the nature of the
ligand [23], which, indeed, was observed in the
experiment.
EXPERIMENTAL
1
The H NMR spectra were run on an Avance-500
spectrometer (Bruker) at 500 MHz and 303 K. The
electronic absorption spectra and kinetics of reac-
tion (1) were measured on a Shimadzu UV1800
instrument. The microscopic images were obtained and
analysis of surface composition of active catalytic
masses was performed on a LEO 1455 VP scanning
electron microscope (Carl Zeiss, Germany) with a SiLi
detector for X-ray spectral microanalysis.
Manganese(III), iron(IV), and copper(III) β-octa-
bromotriphenylcorroles IV–VI were synthesized by
the procedure in [13]. To a solution of 55 mg
(0.094 mmol) of complex I, II, or III in 25 mL of
CHCl3, a 30-fold excess of bromine in the solvent was
added (10 mL). The reaction mixture was stirred for
1 h and 298 K, a solution of 3.4 mmol of pyridine in
10 mL of CHCl3 was added and stirring was continued
for an additional 1–2. The mixture was washed with
sodium sulfite and water, the organic layer was
separated, the solvent was evaporated, and the reaction
product was purified by column chromatography on
silica (eluent chloroform). Yield ca. 25%.
We performed the first joint electron microscopy
and X-ray spectral microanalysis study of active
catalytic masses on the basis of metal corroles I–VI to
show that the catalyst surface is non-uniform in atomic
composition (Fig. 4). This is well seen in the
microscopic image of the active mass of complex V
(Fig. 4a). X-Ray spectral microanalysis, including
scanning of the atomic structure of the surface along
the line shown in the figure, showed that the metal
corrole is primarily localized in granules 1–5 µm in
diameter, that contain the most part of active catalytic
centers, and the concentration of metal atoms between
such centers is very low (Fig. 4b).
The dissociation kinetics of complex IV in the
НОАс–H2SO4 medium [reaction (1)] was followed by
spectrophotometry according to the procedure in [26].
The active catalytic masses on the basis of complexes
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744
BEREZINA et al.
vol. 91, p. 423.
IV–VI were prepared, and their electrochemical and
electrocatalytic study by cyclic voltammetry in 0.1 М
KOH (chemical grade) was performed as described in
[2]. The redox potentials [Еred/ox = (Еcat + Еan)/2] were
averaged over 5–6 runs, the relative error in the
resulting values was no more than 3%.
11. Steene, E., Wondimagegn, T., and Ghosh, A., J. Phys.
Chem. (B), 2001, vol. 105, no. 46, p. 11406.
12. Paolesse, R., Licoccia, S., Fanciullo, M., Morgante, E.,
and Boschi, T., Inorg. Chim. Acta, 1993, vol. 203,
p. 107.
13. Mandoj, F., Nardis, S., Pomarico, G., and Paolesse, R.,
Organic solvents [СHCl3 (chemical grade), DMF
and Py (analytical grade), and НОАс (pure grade)] and
water were purified according to [27]. Anhydrous
sulfuric acid was prepared from commercial H2SO4
(chemical grade) and 15% oleum with conductometric
and densimetric (ρ 1.8384) concentration control.
J. Porph. Phthaloc., 2008, vol. 12, p. 19.
14. The Porphyrin Handbook, Kadish, K.M., Smith, K.M.,
and Guilard, R., Eds., New York: Acad. Press, 2000,
vol. 2, p. 235.
15. Cai, Sh., Licoccia, S., D’Ottavi, C., Paolesse, R.,
Nardis, S., Bulach, V., Zimmer, B., Shokhireva, T.Kh.,
and Walker, F.A., Inorg. Chim. Acta, 2002, p. 171.
ACKNOWLEDGMENTS
16. Steene, E., Dey, A., and Ghosh, A., J. Am. Chem. Soc.,
The work was financially supported by the Russian
Foundation for Basic Research (project no. 12-03-
97542-r_tsentr_a) and Optec LLC (Carl Zeiss).
2003, vol. 125, no. 52, p. 16300.
17. Karimov, D.R., Candidate Sci. (Chem.) Dissertation,
Ivanovo, 2011.
18. Karmanova, T.V., Koifman, O.I., and Berezin, B.D.,
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