Mechanism of the interaction of Mn tetraazaporphines with peracetic acid. The comparative reactivity of Mn(III) porphinoid complexes in the formation of Mn-oxenes

Article abstract of DOI:10.1016/S1381-1169(01)00189-3

The mechanism of peracetic acid interaction with Mn(III) complexes of tetra-R-tetra-tert-butyl-tetraazaporphines (RTAPMnCl, R = H, Br, PhSO₂, NO₂) in acetonotrile/acetic acid solutions has been studied. Analysis of the kinetic data of trans-stilbene epoxidation, naphthalene hydroxylation, 1,1-diphenyl-2-picrylhydrazine (DPPH), and tetra-4-tert-butyl-phthalocyanine zinc (PcZn) one-electron oxidations revealed the reversible formation of a two-center molecular catalyst-oxidant complex ligated with a molecule of acetic acid {A = [RTAPMn(AcOOH)(AcOH)](X)}. The subsequent irreversible transformation of A with rate constant k₂ leads to the formation of two high-valent oxometallo species, supposedly [RTAPMn(V)(O)(AcOH)](X) and [^·+RTAPMn(IV)(O)(AcOH)](X), which are in equilibrium and show distinct oxidation abilities towards olefin and naphthalene. The Hammett-type dependencies of k₂ and of the rate constant of A formation (k₁) have been analyzed and compared with those ones determined earlier for Mn(III) meso-tetra(2,6-dichloro-4-R-phenyl)porphyrins (RTDCPPMnCl). The enhanced sensibility of the acceptor properties of Mn ion to electronegative substitution in tetraazaporphine macrocycle is considered to be a reason of the highest catalytic oxidative activity of Mn-tetra-nitro-tetra-tert-butyltetraazaporphine within studied Mn porphinoids.

Full text of DOI:10.1016/S1381-1169(01)00189-3

Journal of Molecular Catalysis A: Chemical 174 (2001) 89–105
Mechanism of the interaction of Mn tetraazaporphines
with peracetic acid
The comparative reactivity of Mn(III) porphinoid complexes
in the formation of Mn-oxenes
Svetlana V. Barkanova∗, Elena A. Makarova
Organic Intermediates and Dyes Institute, B. Sadovaya 1/4, 103787 Moscow, Russia
Received 12 October 2000; accepted 27 March 2001
Abstract
The mechanism of peracetic acid interaction with Mn(III) complexes of tetra-R-tetra-tert-butyl-tetraazaporphines (RTAPM-
nCl, R = H, Br, PhSO2, NO2) in acetonotrile/acetic acid solutions has been studied. Analysis of the kinetic data of
trans-stilbene epoxidation, naphthalene hydroxylation, 1,1-diphenyl-2-picrylhydrazine (DPPH), and tetra-4-tert-butyl-phtha-
locyanine zinc (PcZn) one-electron oxidations revealed the reversible formation of a two-center molecular “catalyst–oxidant”
complex ligated with a molecule of acetic acid {A = [RTAPMn(AcOOH)(AcOH)](X)}. The subsequent irreversible transfor-
mation of A with rate constant k2 leads to the formation of two high-valent oxometallo species, supposedly [RTAPMn(V)(O)-
(AcOH)](X) and [•+RTAPMn(IV)(O)(AcOH)](X), which are in equilibrium and show distinct oxidation abilities towards
olefin and naphthalene. The Hammett-type dependencies of k2 and of the rate constant of A formation (k1) have been analyzed
and compared with those ones determined earlier for Mn(III) meso-tetra(2,6-dichloro-4-R-phenyl)porphyrins (RTDCPPM-
nCl). The enhanced sensibility of the acceptor properties of Mn ion to electronegative substitution in tetraazaporphine macro-
cycle is considered to be a reason of the highest catalytic oxidative activity of Mn-tetra-nitro-tetra-tert-butyltetraazaporphine
within studied Mn porphinoids. © 2001 Elsevier Science B.V. All rights reserved.
Keywords: Manganese tetraazaporphines; Peracetic acid; Oxidation; Mechanism
1. Introduction
[7,8], iodosylarenes [9], peracids [10–12], sodium
hypochlorite [13,14], potassium monopersulfate ([15]
and the references therein), amine N-oxides [16] and
others) to the substrate (alkenes [1], alkanes [1,2],
aromatics [15,17]) is fulfilled by reactive high-valent
oxo-complexes, M(IV)-oxo-porphyrin ␲-cation rad-
ical and M(V)-oxo-porphyrin ([•+PorM(IV)(O)](X)
and [PorM(V)(O)](X), M = Fe, Mn). The reactivity
of these moieties in the oxidation reactions signif-
icantly depends on the catalyst nature and on the
structure of organic substrate as well. Thus, in olefins
epoxidation catalyzed by Mn porphyrins, a species
Last 20 years cytochrome P-450 modeling with the
employment of synthetic metalloporphyrins, mostly
of iron and manganese complexes (PorM, M =
Mn(III), Fe), have been widely studied [1–5]. Now it
is commonly accepted that oxygen atom transfer from
the oxidant (hydrogen peroxide [6], hydroperoxides
∗ Corresponding author. Tel.: +7-95-2548877;
fax: +7-95-2541200.
E-mail address: rmeluk@cityline.ru (S.V. Barkanova).
1381-1169/01/$ – see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S1381-1169(01)00189-3

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S.V. Barkanova, E.A. Makarova / Journal of Molecular Catalysis A: Chemical 174 (2001) 89–105
Fig. 1. The structure of Mn(III) RTAPMnCl and Mn(III) RTDCPPMnCl.
of [PorMn(V)(O)](X)-type have been shown to be
an oxygen-transferring agent to the double bond of
olefin, producing cis-epoxide from the corresponding
olefin with very high stereospecificity [4]. In the same
reaction catalyzed by Fe porphyrins, both types of
high-valent oxo-complexes [•+PorFe(IV)(O)](X) and
[PorFe(V)(O)](X) can produce epoxide [5]. On the
other hand, the importance of the porphyrin ‘hole’
for affecting hydroxylation of organic substrates
has been theoretically founded for the active forms
of cytochrome P-450 and horseradish peroxidase
[HRP(I)], where Fe(IV) ion is complexed with por-
phyrin ␲-cation radical [18]. It seems that in the case
of Fe porphyrins [•+PorFe(IV)(O)](X)-type species
possess both hydroxylation and epoxidizing proper-
ties. It should be mentioned that the nature and the
reactivity of porphine-like Fe-oxo-complexes depend
strongly on the macrocycle structure, in particular
on meso-aza substitution. Thus, Fe complexes of
azapoprphine derivatives (phthalocyanines, tetraaza-
porphines; APFe), effective catalysts of aromatics
[15,17,19] and alkane [20] oxidation, are completely
inactive in the reaction of olefin epoxidation by both
peracetic acid [17] and KHSO5 [21]. The activity of
iron tetrasulfonatophthalocyanine in aromatics oxida-
tion by KHSO5 has been referred to the participation
of [•+APFe(IV)(O)](X)-type species [15], inactive in
olefin epoxidation [21]. Thus, the formation of the
epoxidizing [APFe(V)(O)](X)-type moiety seems to
be unlikely for aza analogs of Fe porphyrins.
both porphyrins and azaporphines. Recently [22], we
have came to the conclusion about distinct oxida-
tion ability towards the substrates of two porphyrin
Mn-oxo-complexes formed in the reaction of Mn(III)
meso-tetraarylporphyrins with peracetic acid, one of
which epoxidizes olefins and another one hydroxyl-
izes aromatics to naphthols both in competitive and
separate variants of oxidation procedures.
In our previous study, we have found that both Mn
porphyrins (RTDCPPMnCl, R = H, NO2) and their
aza analogs (APMnCl, AP: octa-3,5-nitrophthalocya-
nine, tetra-tert-butyl-tetraazaporphine (1, Fig. 1)) effi-
ciently catalyze olefins epoxidation by peracetic acid
[23,24], whereas in the oxidation of non-activated
aromatics to p-quinones nitro-substituted Mn azapor-
phines are much more reactive than their porphyrin
analog [17,19]. In order to understand the influence
of meso-N substitution in the macrocycle on the ox-
idative reactivity of Mn porphine-like complexes, we
have now studied the kinetics of substituted Mn(III)
tetra-R-tetra-tert-butyl-tetraazaporphines (RTAPM-
nCl) (Fig. 1) interaction with peracetic acid using
the approach developed earlier for Mn porphyrins
[22]. This approach includes the kinetic study of four
catalytic reactions carried out in acetonitrile/acetic
acid solution: (1) olefin epoxidation to the corre-
sponding epoxide; (2) naphthalene hydroxylation
to 1-naphthol; (3) 1,1-diphenyl-2-picrylhydrazine
(DPPH) one-electron oxidation to the corresponding
stable radical (DPP•); (4) tetra-4-tert-butyl-phthalo-
cyanine zinc (PcZn) one-electron oxidation to the
stable ␲-cation radical (•+PcZn). The investigations
of peracetic acid (AcOOH) interaction with Mn(III)
So far, to our knowledge, there are only few
data about comparative study of the reactivity of
high-valent oxo-species for manganese complexes of

S.V. Barkanova, E.A. Makarova / Journal of Molecular Catalysis A: Chemical 174 (2001) 89–105
91
Scheme 1.
meso-tetra(2,6-dichloro-4-R-phenyl)porphyrins (RT-
DCPPMnCl, R = MeO, H, Br, Cl, NO2; Fig. 1)
revealed that this reaction begins from the reversible
formation of a two-center donor–acceptor complex
of “catalyst–oxidant”-type ligated with a molecule of
acetic acid {A = [RTDCPPMn(AcOOH)(AcOH)](X)},
which further undergoes irreversible transformation
to the equilibrium mixture of Mn-oxo-complexes,
[•RTDCPPMn(V)(O)(AcOH)](X) and supposedly
integrator C1-100 (glass column, Apiezon L 2 m,
T col = T inj = 200◦C, or OV 225, 2 and 0.5 m,
T col = 130◦C, T inj = 150◦C, FID, He was used
as a carrier gas). High performance liquid chro-
matography analyses were fulfilled on chromatograph
“Milichrom-1A” supplied with computing integrator
C1-100 and UV detector (Silosorb C18 reverse-phase
column; mobile phase: (a) gradient 0–100% CH3CN
in aqueous 0.01 M KH2PO4 adjusted to pH 3 with
[
+RTDCPPMn(IV)(O)(AcOH)](X) (Scheme 1,
H3PO4, or (b) 10–100% aqueous CH3CN. λanal
=
P = porphyrin macrocycle). The cis-stilbene and
naphthalene were shown to be effective traps of
Mn-oxo-species [RTDCPPMn(V)(O)(AcOH)](X) and
230 and 280 nm for 1-naphthol and naphthalene,
respectively). Reaction products were identified by
coinjection of the reaction solution with the authentic
samples onto HPLC or GC columns. Substrate and
products quantitations were performed using standard
plots of the authentic samples. Visible spectra were
recorded with a fiber-optic spectrometer “LESA-7
Biospec”.
•
[
+RTDCPPMn(IV)(O)(AcOH)](X)], respectively;
DPPH and PcZn were used as the scavengers of the
first reaction intermediate A. The elementary rate
constants of A formation (k1) and of its further trans-
formation to porphyrin Mn-oxo-complexes (k2) have
been estimated and their Hammett-type dependen-
cies have been analyzed [22]. The main goal of the
investigations reported here is to establish similar
structure/activity relationships for Mn(III) tetraaza-
porphines and to compare them with those ones for
Mn(III) porphyrins.
2.2. Materials
Naphthalene, trans-stilbene and DPPH were com-
mercial products and used as received. 1,1-Diphenyl-2-
picrylhydrazyl (DPP) was obtained by DPPH
oxidation with CrO3 and reprecipitated two to three
times with octane from benzene solutions. Ace-
tonitrile (HPLC grade) was additionally purified
by 1 month storage with potassium permanganate
at room temperature, distillation under vacuum at
50–70◦C, then treatment 24 h by CaCl2 and 24 h
by BaO or Ba(OH)2. Solutions of peracetic acid
2. Experimental
2.1. Instrumentation
GC analyses were performed on a GC chro-
matograph “Tsvet-100” equipped with computing

92
S.V. Barkanova, E.A. Makarova / Journal of Molecular Catalysis A: Chemical 174 (2001) 89–105
in acetic acid (1.3–1.9 M) were prepared as pre-
viously reported [23]. Freshly prepared reagent
solutions in acetonitrile were employed in all
experiments.
2.4. General method for trans-stilbene epoxidation
The mother solutions of t-St, RTAPMnX, and
AcOOH in CH3CN were prepared with concentra-
tions three times those desired in reaction mixture. As
an example, the procedure for trans-stilbene oxidation
by 4 + AcOOH is reported. Acetonitrile solutions of
[t-St]in = 0.03 M (1 ml) and of [4]in = 6 × 10−7 M
(1 ml) were poured in a Schlenk tube, then 1 ml of
0.15 M solution of [AcOOH]in (1.31 M AcOOH in
AcOH diluted 8.75 times with CH3CN) was added
and the mixture was kept under stirring. In the case of
the reaction carried out at [AcOH]0 = constant initial
AcOOH solution in CH3CN was prepared with the
desired amount of AcOH (the AcOH concentration
injected with the oxidant is marked as [AcOH]ox).
Samples of 0.2 ml were withdrawn at fixed time, the
excess of AcOOH was quenched with KJ or tetra-
butylammonium iodide and the mixture was analyzed
by GC (OV 225 0.5 m column). In the case of KI
employment, the upper part of GC glass column was
cleaned with wet cotton after every 20 injections.
For complexes 2, 4 and 1 (at [1]0 ≤ 10−6 M) kinetic
curves of trans-stilbene disappearance and epox-
ide formation follow zero-order law up to 50–70%
2.3. Catalysts
Tetra-R-tetra-tert-butyl-tetraazaporpine Mn(III) ch-
lorides (1, 2, 4) were synthesized following reported
procedure [17,24]. The free-base tetra-phenylsulfonyl-
tetra-tert-butylporphyrazine (3a) was synthesized
from tetra-bromo-tetra-tert-butylporphyrazine [25]
by nucleophilic substitution of bromine atoms with
sodium phenylsulfinate. Tetra-bromo-tetra-tert-butyl-
porphyrazine (100 mg, 0.12 mmol) was refluxed
10 min in DMF (20 cm3); after cooling (70◦C), a
solution of NaSO2Ph·2H2O (400 mg, 2.0 mmol) in
DMF (5 cm3) was added and stirred for 10 min.
The reaction mixture was poured into ice–water
(50 cm3), the residue was filtered, washed with wa-
ter (3 × 25 cm3) and dried under vacuum. Column
chromatography on silica gel with chloroform af-
forded a minor amount of the starting stuff; further
elution with a mixture of chloroform:ethyl acetate
(10:1) afforded 3a (120 mg, 93%); Rf 0.77 (Silu-
fol, chloroform:ethyl acetate = 10:1); λmax (CHCl3)
(nm) (ε in dm3 mol−1 cm−1): 647 (7.08 × 104),
598 (6.20 × 104), 340 (6.77 × 104); m/z 1098
(M+, 100%) for C56H58N8O8S4; Anal. Calcd.
for C56H58N8O8S4: C, 61.18; H, 5.32; N, 10.19.
Found: C, 61.68; H, 5.56; N, 9.62. Mn complex 3
was prepared as follows: a solution of 3a (60 mg,
0.055 mmol) in DMSO (20 cm3) was stirred for
15 min at room temperature with Mn(OAc)2·4H2O
(67 mg, 0.27 mmol); the reaction mixture was poured
into water (50 cm3), the residue was filtered, washed
with water (2 × 15 cm3), 5% HCl (2 × 15 cm3) and
dried at ambient conditions. Two fractions were iso-
lated by column chromatography on silica-gel with
CHCl3:acetone (10:1); the second one (Rf 0.24;
substrate conversion, and the rates of trans-stilbene
obs
disappearance W
(equal to the rate of epoxide for-
ol
mation Weopbs) were calculated for the “initial” parts
of kinetic curves. At 0.06–0.6 M [AcOH]0, the re-
action rates occur to be independent on acetic acid
concentration. For all Mn complexes, the indepen-
obs
ol(ep)
dence of W
on olefin concentration was observed
at [t-St]0 ≥ 0.005 M. The values of kol were deter-
obs
mined as W
/[catalyst]0 at [AcOOH]0 ≥ 0.025 M
ol(ep)
for 1 and 2 and ≥0.015 M for 4, when the reaction
rates exhibit independence on oxidant concentration.
For complex 3, kol value was calculated from the
obs
dependence W
on [AcOOH]0 linearized in the
ol(ep)
obs
coordinates (1/W
) − (1/[AcOOH]0).
ol(ep)
silufol, chloroform:acetone
=
10:1) was identi-
2.5. General method for naphthalene hydroxylation
fied as 3 (24 mg, 42%); λmax (CHCl3) (nm) 650 (ε
in dm3 mol−1 cm−1: 3.20 × 104); m/z 1151 (M+,
100%) for [C56H56N8O8S4Mn]+. The first frac-
tion is supposedly a mixture of 3- and 2-substituted
Mn complexes (m/z 1014 (M+) and 873 (M+) for
[C50H52N8O6S3Mn]+ and [C44H48N8O4S2Mn]+,
respectively).
The kinetic measurements were carried out as de-
scribed for trans-stilbene epoxidation; naphthalene
disappearance was measured by GC (OV 225 2 m
column), quenching the AcOOH excess with KJ.
The concentration of formed 1-naphthol was mea-
sured by HPLC without AcOOH excess quenching;

S.V. Barkanova, E.A. Makarova / Journal of Molecular Catalysis A: Chemical 174 (2001) 89–105
93
at fixed time 5–10 ␮l of the reaction mixture was
substrates are oxidized without spectral changes
of Mn tetraazaporphines to DPP• and to +PcZn
•
injected directly into HPLC column. The indepen-
in
dence of W
on naphthalene concentration was
with maximal DPP• yield or PcZn conversion
NphOH
2[DPP•]max/[AcOOH]0).
•
observed at [Nph]0 ≥ 0.004 or 0.012 M for 1 and 3,
4, respectively. For low concentrations of complex 1
(<10−5 M), kinetic curves of naphthalene disappear-
ance obey zero-order law up to no more than 50%
substrate conversion through catalyst destruction. The
up to 100% (ηDPP
=
The stoichiometry of the reaction calculated as
[DPP•]maximal/[AcOOH]0 or [PcZn]reacted/[AcOOH]0
was found near to 2:1. The values of bimolecular
rate constant of DPP• formation and of PcZn bleach-
in
obs
Pc
rate of naphthalene disappearance (W ) determined
ing kgobs and k
obs
were calculated from the equation
Nph
for this “initial” part of the kinetic curve is equal to
the initial rate of 1-naphthol formation, thus evidenc-
ing that 1-naphthol is a single primary product of
naphthalene oxidation. The value of kNph for complex
k
= WDPP(Pc)/(2[RTAPMnCl]0 × [AcOOH]0).
g(Pc)
obs
Pc
The values of kgobs and k determined at the reaction
rate independence of [AcOH]0 are given as kg and kPc,
respectively. The values of equilibrium constant of A
dissociation (Kd) for catalysts 2 and 4 were calculated
from the equation Kd = (K[AcOH]0)1/2/(tan α ×k1);
the calculation of tan α is evident from Fig. 8b; the
dissociation constant of acetic acid in acetonitrile K
was assumed equal to 2.5 × 10−12 M [26].
in
1 was calculated as follows: the dependence of W
Nph
on the AcOOH concentration was plotted in the re-
in
Nph
ciprocal coordinates ((1/W ) − (1/[AcOOH]0));
the y intercept of this plot provides 1/(kNph × [1]0).
We were induced to use very low catalysts concen-
trations of high reactive complexes 3 and 4 (10−7
to 10−8 M) to make the reaction rates measurable,
and due to the catalyst deficiency (destruction) the
conversion of naphthalene was very low; thus, the
3. Results and discussion
in
in
Nph
comparison of W
with W
for 3 and 4 was
3.1. Kinetics of trans-stilbene epoxidation and
naphthalene hydroxylation
NphOH
not accomplished. For catalyst 3, exhibiting high
propensity to the side radical decomposition of an
oxidant, the kinetic curves of 1-naphthol formation
were measured at low [AcOOH]0 = 0.001–0.003 M,
and kNphOH value was evaluated from Eq. (1) using
K1 value, established in trans-stilbene oxidation. We
failed to estimate kNpfOH for complex 2 through its
elevated reactivity in further 1-naphthol oxidation.
Earlier it has been shown [24] that in contrary to
sterically hindered Mn meso-tetraarylporphyrins, Mn
azaporphines catalyze the epoxidation of both cis- and
trans-olefins quantitatively and stereospecifically, the
reaction rates being independent on the olefin struc-
ture. Hence, in this study trans-stilbene was used as
a trap of Mn(V)-oxo-moiety. Catalytic epoxidation of
trans-stilbene to trans-stilbene epoxide and naphtha-
lene hydroxylation to 1-naphthol were carried out with
peracetic acid solutions in acetic acid at the reagent
concentrations reported in Table 1. The determina-
tions of the reaction rates of trans-stilbene and naph-
thalene disappearance of trans-stilbene epoxide and
1-naphthol formations so as the method of the ob-
served rate constant values calculations are described
in Section 2.
2.6. The trans-stilbene oxidation in the presence of
1,1-diphenyl-2-picrylhydrazyl (DPP•) and complex 3
The mother solutions of trans-stilbene, DPP•, 3
and AcOOH in acetonitrile were prepared with con-
centrations four times those desired in reaction mix-
ture. The experiments were carried out as described
for trans-stilbene. The concentrations of trans-stilbene
and trans-stilbene epoxide were measured by GC with
AcOOH quenching by KJ.
Similar to Mn porphyrins, both the rate of olefin
disappearance (Woolbs) and the initial rate of 1-naphthol
in
formation 1 (W
) were determined in such a re-
2.7. 1,1-Diphenyl-2-picrylhydrazyn and
Zn-tetra-tert-butyl-phthalocyanine (PcZn) oxidation
NphOH
1 The intimate mechanism of oxygen atom transfer from oxene
6 to the molecule of naphthalene is now under study and will be
discussed later.
General methods of DPPH and PcZn oxidations
are described in [22]. At any used [AcOH]0, both

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S.V. Barkanova, E.A. Makarova / Journal of Molecular Catalysis A: Chemical 174 (2001) 89–105
Table 1
The trans-stilbene and naphthalene oxidation with peracetic acid catalyzed by RTAPMnCl (CH3CN + AcOH, 20◦C)a
[RTAPMnCl]0 (M)b
[t-St]0 (M)b
[Nph]0 (M)b
[AcOOH]0 (M)b,c
K1 (dm3 mol−1
)
kol (s−1
)
kNph (s−1
)
1: (0.8–10) × 10−6
2: (0.51–5.0) × 10−6
3: (0.02–3.3) × 10−6
4: (0.5–2.0) × 10−7
0.005–0.01
0.005–0.02
0.005–0.01
0.01
0.002–0.008
–
0.012–0.025
0.004–0.025
0.005–0.06
0.01–0.05
0.005–0.05d; 0.001–0.01e
0.005–0.05
50d; 45e
40
30
3.0
3.2
140
1.4
–
∼80f
120
1070
550
a Reagent concentrations, K1, kol (k2), kNph, and K2 values.
b Several measurements were done within shown concentration intervals; experimental errors in the rate constant values determination
and in K1 estimation are 20% ( 10) and 50% ( 25) relative, respectively.
c Reaction solutions contain acetic acid injected with “mother” solution of AcOOH ([AcOH]ox
10[AcOOH]0); some experiments
∼
=
(Fig. 2a) were done at [AcOH]0 = const = [AcOH]ox + [AcOH]added; calculated for 1, 2, and 4, kol, kep, and K1 values were found to be
independent of acetic acid concentration at [AcOH]0 ≥ 0.06 M; all experiments were done for [RTAPMn(III)(AcOH)](X) coordination state.
d Determined in trans-stilbene epoxidation.
e Determined in naphthalene hydroxylation.
f Calculated from equation kNph = WNphOH/{K1[3]0 × [AcOOH]0} with accuracy 40%.
gion of substrate concentration, where the reaction
rates are independent on the last, i.e. when olefin
and naphthalene act as traps of high-valent catalyst
species. Both of them are first order in [RTAPMnCl]0
and exhibit Michaelis–Menten-type dependence on
[AcOOH]0 (Figs. 2–4, Eq. (1)).
formed in the side-oxidant decomposition during the
trans-stilbene epoxidation catalyzed by complex 3.
In a good agreement with the supposition, in the
presence of DPP•, the trans-stilbene epoxide yield
becomes quantitative at every point of the reaction
(Fig. 5). Moreover, in this case the maximal olefin
conversion increases, apparently due to the catalyst
protection from oxidative degradation by AcO• and/or
kol(Nph)K1[RTAPMnX]0[AcOOH]0
Wol(NphOH)
=
•
1 + K1[AcOOH]0
AcO2 , which in turn leads to the enhanced catalyst
(1)
turnover number (TN = [substrate]reacted/[catalyst]0).
The values of monomolecular rate constants kol
and kNpfOH were calculated from Eq. (1a) for such
a region of [AcOOH]0, where the reaction rates are
independent on the oxidant concentration. For com-
plexes 1, 3 and 4, kNpfOH values occur to be two times
less than that of kol (Table 1). Furthermore, the value
of the equilibrium constant K1 calculated in naphtha-
lene hydroxylation using Eq. (1) and data reported in
Fig. 6 is similar to one determined in trans-stilbene
epoxidation (Table 1), indicating the formation of
the same first intermediate A in both reactions. The
reported data are similar to those observed earlier
[22] for Mn tetraarylporphyrins (Table 2), thus evi-
dencing that the reaction of peracetic acid interaction
both with the porphyrin and tetraazaporphine Mn(III)
complexes is described by one and the same reaction
mechanism (Scheme 1). Calculated from Scheme 1,
equations for epoxide and 1-naphthol formations in
olefin and naphthalene oxidation are identical to the
experimentally determined Eq. (1) at kol = k2 and
kNph = k2K2/(1 + K2)
Wol(NphOH) = kol(Nph) [RTAPMnX]0,
at K1 [AcOOH]0 > 1
(1a)
It is worth noting that at the elevated oxidant con-
centration ([AcOOH]0 > 0.05 M for 1, 2 and 4 or
>0.025 M for 3), the epoxide yield determined at every
point of the reaction as [epoxide]formed/[olefin]reacted
is less than 100%. In the case of Mn porphyrins,
similar effect was explained by possible compet-
itive radical decomposition of peracid excess fol-
lowed by non-selective olefin oxidation [24]. To
clarify whether this hypothesis comes true for Mn
tetraazaporphines, we have employed stable rad-
ical 1,1-diphenyl-2-picrylhydrazyl (DPP•) as
a
trap 2 of AcO• and AcO2 , presumably efficiently
•
2 Well-known radical traps (e.g. 2,6-di-tert-butylphenol) cannot
be used in the reactions catalyzed by Mn azaporphines because
of their oxidation to p-quinones, e.g. in the presence of APMnX
2,3,6-trimethylphenol-1 is quickly and quantitatively converted to
2,3,6-trimethyl-1,4-benzoquinone at two times AcOOH excess.

S.V. Barkanova, E.A. Makarova / Journal of Molecular Catalysis A: Chemical 174 (2001) 89–105
95
obs
Fig. 2. The dependence of partial rates (k
= Wol(ep)/[RTAPMnCl]0) of trans-stilbene disappearance and trans-stilbene epoxide formation
ol(ep)
on [AcOOH]0 in the reaction catalyzed by 1, 2, and 4: (a) [1]0 = 1.6×10−6 M, [t-St]0 = 0.005 M, [AcOH]0 = 0.6 M; (b) [2]0 = 5×10−6 M,
[t-St]0 = (0.5–1) × 10−2 M, [AcOH]ox = 0.1–0.6 M; (c) [4]0 = 1 × 10−7 M, [t-St]0 = 0.01 M, [AcOH]ox = 0.05–0.6 M.
(Eqs. (2) and (3)):
should be considered. Indeed, molecular complexes of
PorFe and PorMnX with H2O2 [6], alkyl hydroperox-
ides [27,28] and amine N-oxides [16] were kinetically
detected as primary intermediates; they were also
suggested in PorMn interaction with NaOCl [29] and
iodosylbenzene [30–32]. On the other hand, peracids
interaction with Fe and Mn porphyrins was postulated
to occur with ‘persalts’ (PorMOOCOR) formation as
precursors of high-valent metalloxo-species [33–36].
If the last comes true in the reported catalytic sys-
tems, theoretically calculated equations for the rates
of trans-stilbene and naphthalene oxidation would
fit with experimentally determined Eq. (1) at kol and
kNph expressed by Eqs. (4) and (5):
kol = k2
(2)
(3)
k2K2
kNph
=
1 + K2
Thus, with this approach the value of the rate con-
stant k2, a criterion of RTAPMnCl reactivity in
Mn(V)-oxo-complex formation, could be easily deter-
mined from the experiment as kol value. 3 Scheme 1
though disregards the possibility of A dissociation and
Mn-oxo-species formation from peroxoacetates A−,
whereas both variants of the reaction are feasible and
3 In [22], rate constant kol for Mn porphyrins was erroneously
attributed as k2/(1 + K2).
kol = k2ꢀ Kd
(4)

96
S.V. Barkanova, E.A. Makarova / Journal of Molecular Catalysis A: Chemical 174 (2001) 89–105
obs
Fig. 3. (a) The dependence of partial rate of trans-stilbene dis-
appearance (koolbs) and trans-stilbene epoxide formation (keopbs) on
[AcOOH]0 in the reaction catalyzed by 3; (b) linearization of the
Fig. 4. (a) The dependence of partial rate (k
= WNph
/
Nph
[RTAPMnCl]0) of naphthalene disappearance on [AcOOH]0 in the
reaction catalyzed by 1; (b) linearization of the dependence (a).
[1]0 = 1 × 10−5 M, [Nph]0 = 0.0025 M, [AcOH]0 = 0.55 M.
dependence (a). [3]0 = 3.3 × 10−6 M, [t-St]0 = 0.005–0.01 M,
obs
[AcOH]0 = 0.5 M. At [AcOOH]0 = 0.05 M, k
was deter-
ol(ep)
mined in the presence of DPP• (data from Fig. 5).
k2ꢀ K2Kd
kNph
=
,
at 1 > Kd
(5)
1 + K2
where k2ꢀ is the rate constant of A− transformation to
Mn(V)-oxo-complex.
To clarify this problem, we have used two different
compounds, DPPH and PcZn as scavengers of the first
intermediate A and have investigated the influence of
acetic acid on the kinetics of their one-electron oxi-
dation to the corresponding stable radical (DPP•) and
stable ␲-cation radical (•+PcZn, λmax = 510, 725 nm
[37]), respectively. If the equilibrium A ↔ A− + H+
does exist, the rates of DPPH and PcZn oxidation
should depend on acid addition, supposing that the
oxidation activities of A and A− are different.
Fig. 5. Kinetic curves of trans-stilbene disappearance (ᮀ, ᭛)
and trans-stilbene epoxide formation (᭺, ᭝) in trans-stilbene
oxidation by peracetic acid catalyzed by
3 in the pres-
ence of 1,1-diphenyl-2-picrylhydrazyl ([DPP•]0 = 0.025 M; ᮀ,
᭺) and without hydrazyl (᭛, ᭝). [3]0
[AcOOH]0 = 0.05 M, [AcOH]ox = 0.56 M.
=
3.3 × 10−6 M,

S.V. Barkanova, E.A. Makarova / Journal of Molecular Catalysis A: Chemical 174 (2001) 89–105
97
Fig. 6. Visible spectra changes in the reaction of PcZn oxidation by peracetic acid catalyzed by complex 1. [1]0 = 0.5 × 10−7 M,
[PcZn]0 = 3 × 10−5 M (ε674 nm = 2.2 × 105), [AcOOH]0 = 0.5 × 10−4 M, [AcOH]0 = 0.2 M, l = 0.2 cm, time intervals 30 s.
3.2. 1,1-Diphenyl-2-picrylhydrazine and
Zn-tetra-tert-butyl-phthalocyanine oxidation: the
influence of acetic acid
first reaction stage in Scheme 1 becomes irreversible
and the rates WDPP (WPc) and A (or A−) formation
are equal taking into account the stoichiometric coef-
ficient 2.
Previously, we have shown that UV–VIS spectra
of Mn tetraazaporphines acetonitrile solutions (10−6
to 10−4 M) obey Lambert–Beer’s law and do not
change at 0.001–0.5 M acetic acid addition. The high-
est AcOH content was limited by the protonation of
both DPPH and PcZn, noticeable at [AcOH]0 > 0.1
and >0.5 M, respectively. The used concentrations of
catalysts and substrates are indicated in Table 3.
For the reactions of DPPH oxidation as well as of
PcZn discoloration (Fig. 6), we have measured the
reaction rates of DPP• formation (WDPP) or PcZn
bleaching (WPc) at several concentrations of acetic
acid. At every [AcOH]0, the rate of DPP• formation
so that the rate of PcZn bleaching was found to be first
order both in [AcOOH]0 and [RTAPMnX]0 and inde-
pendent on the substrate concentration at [DPPH]0 ≥
10−3 M in DPPH oxidation and at [PcZn]0 ≥ 1 ×
10−5 M in PcZn oxidation. The kinetic curves of both
reactions obey zero-order law up to 75% maximal con-
centration of formed DPP• and up to 90% PcZn con-
version. Thus, the used substrates DPPH and PcZn
act as real traps for the oxidative intermediate, i.e. the
As it turned out, the rates of both reactions de-
pend strongly on the concentration of added acetic
acid (Figs. 7 and 8 exemplify the acidic depen-
dencies for complexes 1 and 4, respectively). The
first phase of the observed acidic dependencies can
Table 2
The values of kol (k2), kNph
,
and k1 for acidic
adducts of Mn(III) meso-tetra(2,6-dichloro-4-R-phenyl)porphyrins
{[RTDCPPMn(AcOH)](X),
X
= Cl, AcO} determined in
cis-stilbene, naphthalene, 1,1-diphenyl-2-picrylhydrazine, and
Zn-tetra-4-tert-buthylphthalocyanine catalytic oxidation by per-
acetic acida
[RTDCPPMnCl]0 kol
(s−1
kNph
(s−1
k1
)
)
(dm3 mol−1 s−1
)
H
MeO
Br
Cl
NO2
0.85
1.0
1.8
2.0
4.3
0.38
0.51
0.94
0.85
3.65
200
210
260
220
230
a CH3CN + AcOH, 20◦C; [AcOH]0:[RTDCPPMnCl]0
≥
1000:1 (from [22]).

98
S.V. Barkanova, E.A. Makarova / Journal of Molecular Catalysis A: Chemical 174 (2001) 89–105
Table 3
Reagent concentrations and k1 values determined in the reactions of DPPH and PcZn oxidation by peracetic acid catalyzed by RTAPMnCla
[RTAPMnCl]0 (M)b
[DPPH]0 (M)b
[PcZn]0
[AcOOH]0
[AcOH]0 (M)b
k1 (dm3 mol−1 s−1
)
× 105 (M)b
× 105 (M)b
c
d
d
1: (0.5–1) × 10−6
(0.17–1) × 10−7
;
(1–2) × 10−3
1.2–3.0
1.0–3.0
1.0–3.0
2.5–6.0c
0.001–0.1 c; 0.1–0.3
4.5 × 103 c,e; 5.0 × 103
d
2: (0.1–1.0) × 10−7
3: (1.0–2.5) × 10−7
4: (0.5–1.0) × 10−9
2.5–10.0
4.0
5–10.0
0.01–0.05
0.06–0.1
0.02–0.06
1.5 × 104
d
(1–2) × 10−3
8.0 × 104
c
d
2.7 × 105
a CH3CN + AcOH, 20◦C.
b Several measurements were done within shown concentration intervals; the rate of base-line DPPH oxidation by AcOOH (∼10% from
the catalytic one) was subtracted from the summary rate of DPP• formation in the catalytic reaction; the rate of base-line PcZn oxidation
by AcOOH was less than 2% from the catalytic one; the values of k1 were calculated with accuracy 20% ( 10) relative; for the reaction
of PcZn oxidation within indicated [AcOH]0, the rate of PcZn bleaching does not depend on [AcOH]0.
c Calculated for [RTAPMn(AcOH)](X) in DPPH oxidation.
d Calculated for [RTAPMn(AcOH)](X) in PcZn oxidation.
e The value k1 = 48 dm3 mol−1 s−1 for 1 published earlier [24] was calculated for the mixture of [TAPMn(CH3CN)](X) and
[TAPMn(AcOH)](X) adducts.
be explained by the formation of acetic adduct
[RTAPMn(AcOOH)(AcOH)](X) instead of acetoni-
trilic one, possessing the enhanced reactivity in DPPH
and PcZn oxidations; in Mn tetraarylporphyrins study,
we have came to the same conclusion [22]. Recently,
the significant influence of axial ligand nature (acids,
solvent molecules, etc.) on the oxidative properties
of oxygen-containing intermediates has been reported
for substituted metalloporphyrins [5,38]. The inde-
pendence of WDPP and WPc on the acetic acid content
on the second phase of acidic dependencies (Figs. 7
and 8) evidences that in this [AcOH]0 region, the
Fig. 8. (a) The dependence of partial rate of PcZn bleaching
obs
Fig. 7. The AcOH dependence of partial rate {kgobs = WDPP
/
{k = WPc/(2[4]0 × [AcOOH]0)} on [AcOH]0 for complex 4;
Pc
(2[1]0 × [AcOOH]0)} of DPP• formation in DPPH oxidation by
peracetic acid catalyzed by complex 1. [DPPH]0 = 2 × 10−3 M,
[1]0 = 1 × 10−6 M, [AcOOH]0 = 0.5 × 10−4 M.
(b) linearization of the dependence (a) at [AcOH]0 = 0.06–0.4 M.
[4]0
=
(0.3–1) × 10−9 M, [AcOOH]0
=
(0.5–1) × 10−4 M,
[PcZn]0 = (1–3) × 10−5 M.

S.V. Barkanova, E.A. Makarova / Journal of Molecular Catalysis A: Chemical 174 (2001) 89–105
99
Scheme 2.
equilibrium between acetonitrilic and acidic catalyst
adducts is fully shifted to the formation of acidic
ones. In this case, bimolecular rate constant values
of DPP• formation or of PcZn bleaching (kg and
kPc) should be referred to the Mn tetraazaporphines
acidic adducts [RTAPMn(AcOOH)(AcOH)](X). For
complex 1, the kPc value determined on the second
phase of acidic dependence at [PcZn]0 ≥ 1 × 10−5 M
is very close to kg values obtained in DPPH oxida-
tion at [DPPH]0 ≥ 10−3 M (Table 3), thus evidencing
that PcZn and DPPH trap one and the same catalytic
intermediate.
The decrease of the reaction rate in the third phase of
acidic dependencies for less basic PcZn points strongly
that molecular complex A undergoes dissociation and
that the reactivity of the formed peroxoacetate A−
in one-electron oxidation is higher than that of A.
Scheme 2 represents the simplest mechanism of DPPH
(as well as PcZn) oxidation; theoretically calculated
from Scheme 2, equations for the reaction rates of the
third phase fit well with the experimental one at kg(Pc)
expressed by Eq. (6).
and 4 (∼0.6×10−6 and ∼0.3×10−6 M, respectively;
the calculations are described in Section 2).
3.3. The nature of Mn-oxenes precursor: the
comparison of the Mn tetraazaporphines and Mn
tetraarylporphyrins reactivity in their interaction
with peracetic acid
Although, the dissociation of molecular complex
A under the reaction conditions seems to be proved,
the exact nature of Mn-oxo-complexes precursor is
still questioned. Really, if Mn-oxo-species are formed
with the rate constant k2ꢀ from peracetate A−, unknown
Kd value in Eqs. (4) and (5) and derived from them
Eq. (7)
KdR
KdH
(k2ꢀ )R
(k2ꢀ )H
(ln k2ꢀ )rel = ln
(7)
rel
= ln k − ln
ol
complicates the k2ꢀ calculation, hence, the establish-
ing of catalyst structure/activity relationship. Never-
theless, slight changes in Kd values, together with the
sharply expressed dependence of kol on the substituent
nature (for 2 and 4 kol and Kd values differ 300 and
2 times, respectively) allow to disregard the second
member in Eq. (7) as compared to the first one and con-
sider ln (k2ꢀ )rel = ln korell. Hence, if Mn-oxo-moieties
are produced from the dissociated form A−, the ex-
WDPP(Pc)
kg(Pc)
=
=
2[RTAPMnX]0[AcOOH]0
k1Kd
(6)
(K[AcOH]0)0.5 + Kd
Satisfactory linearization of the third phase of acidic
perimentally determined relative rate constant kol
=
dependencies in the coordinates (1/k )−[AcOH]00.5
koRl/koHl can be used as correct criterion of RTAPMnCl
relative reactivity in the Mn(V)-oxo-complex forma-
tion.
obs
Pc
(Fig. 8b) is in a good agreement with the proposed
Scheme 2 and Eq. (6). According to this equation,
at the reaction rate independence of [AcOH]0, i.e.
at Kd > (K[AcOH]0)0.5, experimentally determined
kg(Pc) values are equal to the elementary rate constant
k1 (Table 3). From Eq. (6), we have also estimated the
values of Kd for molecular complexes A of catalysts 2
For Mn tetraazaporphines, non-linear correlation of
ln korell in the coordinates of Hammett equation (Fig. 9)
is similar to one found earlier [22] for Mn tetraarylpor-
phyrins. The character of both dependencies indicates
that for all studied Mn porphine-like complexes, the

100
S.V. Barkanova, E.A. Makarova / Journal of Molecular Catalysis A: Chemical 174 (2001) 89–105
rel
ol
rel
rel
ol
Fig. 9. The Hammett-type correlations of k (᭺), k1 (᭿) for Mn(III) tetraazaporphines 1–4 and of k for RTDCPPMnCl (᭝).
∼
reaction of Mn-oxo-species formation is determined
by both acceptor properties of Mn ion and donor ones
of the macrocycle. It means that there is a two-centered
and two-component donor–acceptor bond, which links
catalyst and oxidant molecules in the species produc-
ing Mn(V)-oxo-complex; therefore, it cannot be the
salt-like peracetate RTAPMnOOAc, and a molecular
complex A should be considered as a precursor of
Mn(V)-oxo-species.
One of the main characteristics of molecular com-
plex A is the degree of electron density transfer
from a molecule-donor to a molecule-acceptor. The
increase of the last should lead to magnification of
O–O bond polarization in the molecule of coordinated
peracetic acid, thus facilitating Mn(V)-oxo-complex
formation. As known, complete charge transfer in
donor–acceptor complex should be followed by
UV–VIS spectra changes. Interestingly, that in the
course of olefin and naphthalene oxidation in the
conditions, when the high excess of peracid with re-
spect to the catalyst allows mainly the presence of
the associated form ([A] [catalyst] ) and electronic
=
0
spectra should be referred to A, the spectral changes
of Mn(III) porphyrins and Mn(III) tetraazaporphines
are different. Really, in the reaction of cis-stilbene
epoxidation catalyzed by RTDCPPMnCl (R = H,
NO2), we have not observed spectral changes of Mn
porphyrins in the visible region until full conversion
of olefin (Fig. 10). 4 This indicates that electron trans-
fer between Mn porphyrin and peracetic acid in the
intermediate APor is not complete. If the same reac-
tion is catalyzed by Mn tetraazaporphine 1, its visible
spectrum is drastically changed at the very beginning
of the reaction (Fig. 11a); similar phenomena was
also observed in naphthalene oxidation (Fig. 11b).
The observed spectral changes can be explained by
complete electron transfer from the tetraazaporphine
macrocycle to the coordinated AcOOH molecule in
4 TDCPPMnX oxidative degradation becomes noticeable after
the exhaustive olefin oxidation (20 min in the conditions shown in
Fig. 10).

S.V. Barkanova, E.A. Makarova / Journal of Molecular Catalysis A: Chemical 174 (2001) 89–105
101
Fig. 10. (a) Visible spectra changes in the oxidation of cis-stilbene (0.01 M) by peracetic acid (0.05 M) catalyzed by Mn(III)
meso-tetra(2,6-dichlirophenyl)porphyrin (1 × 10−5 M), [AcOH]ox = 0.5 M, l = 1 cm; (b) monitoring of the reaction solution at λ = 474 nm
(under the same conditions the total time of cis-stilbene exhaustive oxidation is 20 min).
the corresponding molecular complex (ATAP ). Hence,
we believe that ATAP is a complex of Mn(III) por-
phyrazine ␲-cation radical with deeply polarized
AcOOH molecule (Fig. 12). Indeed, one of the pri-
mary products of azaporphines oxidative degradation
is known to be a product of nucleophilic addition to
the C␣-pyrrole atom [39], thus confirming the local-
ization of donor component d. If our explanation of
these experimental observations is correct, the corre-
sponding porphyrin’s intermediate (APor) should be
more strong acids than ATAP . Really, the rate of PcZn
bleaching in the Mn porphyrins-depending reaction
was not changed at [AcOH]0 = 0.1–0.4 M [22],
whereas the RTAPMnCl-catalyzed reaction exhibits
such dependence (Fig. 8). According to Eq. (6), it
means that KdPor > KdTAP 5
.
So, two lines of experiments are described by the
same hypothesis, the key point of which is that co-
ordinated peracetic acid is more strongly polarized
being complexed with Mn tetraazaporphines than
with Mn porphyrins, the former thus should be more
active in Mn-oxo-moieties generation than the latter.
5 Slight variation of Kd on the substituent nature in Mn tetraaza-
porphines evidences that the degree of electron density transfer
between Mn tetraazaporphine and coordinated peracetic acid is
about not influenced by the substituent nature, possibly due to a
mechanism of charge-transfer between Mn ion, tetraazaporphine
macrocycle, and a molecule of coordinated peracid.

102
S.V. Barkanova, E.A. Makarova / Journal of Molecular Catalysis A: Chemical 174 (2001) 89–105
Fig. 11. Visible spectra changes in the oxidation of 0.01 M cis-stilbene (a) and 0.005 M naphthalene (b) by 0.05 M AcOOH catalyzed by
complex 1 (1 × 10−5 M) at [AcOH]0 = 0.5 M, l = 1 cm — (a) 1: before AcOOH adding; 2, 3 and further: spectra scanning every 5 s
(under the same conditions the total time of cis-stilbene exhaustive oxidation is 5 min); (b) 1: before AcOOH adding; 2: after 5 s reaction;
3–9: spectra scanning every 20 s (under the same conditions maximal naphthalene conversion is achieved at the reaction time of 8 min).
Really, for all Mn tetraazaporphines, especially for
nitro-derivatives, k2 values are higher than that ones
for their porphyrins analogs (Tables 1 and 2). The more
expressive Hammett-type correlation of k2 for Mn
tetraazaporphines could be explained by closer dis-
position of the substituent to the reaction center (Mn
ion) in Mn tetraazaporphines (β-position of pyrrole
ring) than in Mn meso-tetraarylporphyrins (p-position
of phenyl ring). Recently, the enhanced reactivity in
the epoxidation and hydroxylation reactions of Mn
β-octafluoro-meso-tetra(2,6-dichlorophenyl)porphyrin
as compared with Mn meso-tetra(2,3,4,5,6-pentafluo-
rophenyl)porphyrin has been demonstrated [40].
This explanation, though, is not suitable for the
interpretation of different dependence of k1 values on
the substituent nature for the studied Mn porphine-like
complexes. Indeed, whereas the values of k1 for all
Mn porphyrins are nearly identical (Table 2), the
linear free energy relationships between ln k1rel with
positive ρ value is observed for Mn tetraazaporphines
(Table 3, Fig. 9). For Mn porphyrins, the indepen-
dence of k1 on the substituent nature was explained

S.V. Barkanova, E.A. Makarova / Journal of Molecular Catalysis A: Chemical 174 (2001) 89–105
103
ionization potential of the central nitrogen is much
more sensitive to electronegative substitution in a
porphyrazine molecule than in a porphyrin one. It
was concluded that electron-withdrawing peripheral
substituents in porphyrazines should cause drastic
shifts in the ionization potentials of the central ni-
trogens, which in turn results in an additional mag-
nification of an oxidation potential of complexed
metal ion. According to these predictions, acceptor
properties of metal ion in Mn porphyrazines (espe-
cially in nitro-derivatives) should be increased in a
dramatic fashion in comparison with the porphyrin
analog both by meso-tetraaza substitution and by
peripheral electron-withdrawing substituents. These
theoretical predictions are in full agreement with the
reported here k1 dependence in Hammett’s coordi-
nates and with the considerably increased values of
k1 for nitro-substituted Mn tetraazaporphine as com-
pared with analogous Mn porphyrin (2.7 × 105 and
2.3×102 dm3 mol−1 s−1 for 4 and NO2TDCPPMnCl,
respectively).
Whereas the first stage of peracetic acid interac-
tion with Mn porphine-like complexes is determined
by the ability of porphine-like molecule to bind
peracid molecule, the efficiency of A transformation
to Mn-oxo-complexes, as we have already mentioned,
should depend on the degree of the coordinated O–O
bond polarization. The last can be enhanced by both
electron donation from a macrocycle to O–O bond
and electron withdrawing from it by Mn ion. Thus,
we believe that donor component a plays significant
role in the second stage of the discussed reaction,
giving rise to non-linear Hammett-type dependence
of k2 both for porphyrazine and porphyrin manganese
complexes. The enhanced degree of O–O polarization
(so k2 = kol) in ATAP at electronegative substitu-
tion should be considerably higher than in porphyrin
analogs through both complete electron transfer along
the donor component a and the extremely increased
acceptor properties of Mn ion. Indeed, kol value for
4 is 250 times higher than for the corresponding Mn
porphyrin (Tables 1 and 2). For H-substituted 1 or for
complex 2 with the substituent of moderate strength
(bromine), the acceptor properties of Mn ion, though
enhanced by aza substitution, are not additionally af-
fected by peripheral one. As a result, kol values of 1
and 2 slightly differ from those of their carbo-analogs
(3.5 and 1.8 times, respectively; Tables 1 and 2).
Fig. 12. The proposed structure of the intermediate ATAP (the
substituents in β-positions of pyrrole rings are omitted for the
simplicity).
[22] by full compensation in energy of donor and
acceptor components on the stage of donor–acceptor
complex APor formation. This phenomena reveals
the mechanism of electron density transfer from
the periphery of the macrocycle to Mn(III) ion,
experimentally observed for Mn(II) (and Mn(III))
phthalocyanines [41] and theoretically calculated
for numerous porphine-like systems [42]. Similar
K2 values of the equilibrium RTAPMn(V)(O) ↔
•+RTAPMn(IV)(O) calculated from Eqs. (2) and (3)
for complexes 1, 3, and 4 (0.875, 1.33, 1.06) support
this hypothesis.
For Mn porphyrazines, the growth of k1 values at
electronegative substitution evidences that acceptor
properties of Mn(III) ion and donor ones of aza macro-
cycle vary in a significantly different degree at the pe-
ripheral substituent variation. This conclusion agrees
with theoretical predictions. Really, all-electron ab
initio Hartree–Fock self-consistent field calculations
of the orbital energies of non-metallic porphine-like
compounds [42] evidence that meso-tetraaza sub-
stitution in the porphyrine macrocycle results in a
significant increase both in the first ionization po-
tential of porphyrazine (tetraazaporphine) and in
the core ionization potentials of the central nitrogen
atoms. The last should give rise to a significantly
higher oxidation potential of metal ion complexed
to a porphyrazine than to an analogous porphyrin.
Furthermore, the calculations revealed that the core

104
S.V. Barkanova, E.A. Makarova / Journal of Molecular Catalysis A: Chemical 174 (2001) 89–105
4. Conclusions
could be the reason of the highest reactivity of
nitro-substituted Mn porphyrazine in the studied re-
actions and in the aromatics oxidation to p-quinones
as well [19].
Mechanism of peracetic acid interaction with Mn
complexes of substituted tetra-R-tetra-tert-butyltetra-
azaporphines (R = H, Br, PhSO2, NO2) in ace-
tonitrile/acetic acid solutions has been studied and
compared with the established earlier for Mn-
(III) meso-tetra(o,oꢀ-dichloro-p-R-phenyl)porphyrins
(R = MeO, H, Br, Cl, NO2). The trans-stilbene,
naphthalene, 1,1-diphenyl-2-picrylhydrazine, and
tetra-4-tert-butyl-phthalocyanine zinc have been used
as scavengers of high-reactive catalyst intermediates.
In the presence of acetic acid excess, an acidic adduct
[RTAPMn(AcOH)](X) interacts with peracetic acid
via the formation of donor–acceptor complex A =
[RTAPMn(AcOOH)(AcOH)](X) with complete elec-
tron transfer from tetraazaporphine macrocycle to the
coordinated AcOOH molecule, donor and acceptor
components being localized on the macrocycle and
Mn ion, respectively. A linear Hammett-type depen-
dence of the elementary rate constant of A formation
k1 with positive ρ value reveals the dominant role of
acceptor properties of Mn ion on the first stage of the
reaction.
Acknowledgements
This work was supported by the Russian Foundation
for Basic Research (grant 00-03-32017).
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•
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rel
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