Structural modification and kinetic stability of octaethylporphyne complexes with palladium (II)

Article abstract of DOI:10.1134/S0036024411060215

The influence of gradual meso-phenyl substitution in 2,3,7,8,12,13,17,18- octaethyl-21H,23H-porphyne (H₂OEP) on the stability of its complexes with Pd(II) in comparison to the meso-tetraphenylporphyne complex with unsubstituted C_β atoms is investigated by means of the chemical kinetics and physicochemical analysis. Using the spectral methods, the states and reactions of complexes in the AcOH-H₂SO₄ mixures is studied for the wide range of compositions. It is found that, the coordination centers are stable in mixtures with compositions of up to 100% of H ₂SO₄. Whether in the molecular state or in association with a proton (PdOEP and its mono-meso-phenyl derivative), the complexes undergo transformations that are investigated by chemical kinetics. It is shown that instead of the usual dissociation of the coordination center, single-electron oxidation in the macrocycle of complexes takes place. A multistage mechanism is revealed that involves the kinetically significant equilibrium between the formation of H-associated complex and irreversible coordination of molecular oxygen, followed by the acid-assisted transfer of an electron from the aromatic system to this oxygen. The oxidation stability of complexes is determined, and the relation between the structure of macrocyclic ligand and the electronic structure of coordination center is discussed.

Full text of DOI:10.1134/S0036024411060215

ISSN 0036ꢀ0244, Russian Journal of Physical Chemistry A, 2011, Vol. 85, No. 6, pp. 926–933. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © T.N. Lomova, M.E. Klyueva, E.Yu. Tyulyaeva, 2011, published in Zhurnal Fizicheskoi Khimii, 2011, Vol. 85, No. 6, pp. 1020–1027.
PHYSICAL CHEMISTRY
OF SOLUTIONS
Structural Modification and Kinetic Stability
of Octaethylporphyne Complexes with Palladium (II)
T. N. Lomovaa, M. E. Klyuevab, and E. Yu. Tyulyaevaa
a Institute of Solution Chemistry, Russian Academy of Sciences, Ivanovo, 153045 Russia
b Ivanovo State University of Chemistry and Technology, Ivanovo, 153460 Russia
eꢀmail: teu@iscꢀras.ru
Received December 1, 2009
Abstract—The influence of gradual mesoꢀphenyl substitution in 2,3,7,8,12,13,17,18ꢀoctaethylꢀ21H,23Hꢀ
porphyne (H2OEP) on the stability of its complexes with Pd(II) in comparison to the mesoꢀtetraphenylporꢀ
phyne complex with unsubstituted
C atoms is investigated by means of the chemical kinetics and physicoꢀ
chemical analysis. Using the spectralβmethods, the states and reactions of complexes in the AcOH–H2SO4
mixures is studied for the wide range of compositions. It is found that, the coordination centers are stable in
mixtures with compositions of up to100% of H2SO4. Whether in the molecular state or in association with a
proton (PdOEP and its monoꢀmesoꢀphenyl derivative), the complexes undergo transformations that are
investigated by chemical kinetics. It is shown that instead of the usual dissociation of the coordination center,
singleꢀelectron oxidation in the macrocycle of complexes takes place. A multistage mechanism is revealed
that involves the kinetically significant equilibrium between the formation of Hꢀassociated complex and irreꢀ
versible coordination of molecular oxygen, followed by the acidꢀassisted transfer of an electron from the aroꢀ
matic system to this oxygen. The oxidation stability of complexes is determined, and the relation between the
structure of macrocyclic ligand and the electronic structure of coordination center is discussed.
Keywords: chemical kinetics, physicochemical analysis, spectral methods, complexes, octaethylporphyne,
palladium.
DOI: 10.1134/S0036024411060215
INTRODUCTION
PdTetPOEP (TetPOEP is 5,10,15,20ꢀtetraphenylꢀ
2,3,7,8,12,13,17,18ꢀoctaethylꢀ21H,23Hꢀporphyne
dianion) complexes in H2SO4 [13] and of H2TPP
complexes with Ru(IV) and Os(II) in AcOH–H2SO4
at temperatures above 340 K [14]. In contrast to the
dissociation reaction of metalloporphyrins, neither
the new singleꢀelectron oxidation reaction nor the
chemical oxidation reaction of MPs has been studied.
The parameters of complex oxidation’s stability and
the stability constants of their coordination centers are
important for the chemistry of materials based on metꢀ
Due to their unique aromatic structure, palladium
porphyrin complexes are widely used in photoꢀ and
electroactive materials [1, 2], optical sensors of oxygen
[3, 4], as doping agents [5] and synthetic catalases [6].
Developing approaches to the directed structural
modification of complexes aimed at yielding specific
properties without reducing the stability of substances
is of great interest. In order to determine the stability
of metalloporphyrins (MP), the parameters of their
chemical reactions with acids leading to the dissociaꢀ
tion of coordination centers are normally used. It is alloporphyrins. The stable form of metalloporphyrins
known that in the mediums with high concentrations
of protons, porphyrin complexes of transition metals
can decompose into metal cation and ligands [7]; can
be protonated in different reaction centers, thereby
forming stable compounds; or can be oxidized in an
in acid solutions is radical complexes, which is why the
parameters of the oxidation reaction in fact characterꢀ
1
ize the stability of complexes.
In the present work, (2,3,7,8,12,13,17,18ꢀoctaethꢀ
ylporphynato)palladium (II) complex (1) and its
5ꢀphenylꢀ5,15ꢀdiphenylꢀ, and 5,10,15,20ꢀtetraphenylꢀ
aromatic macrocycle to
π
ꢀcation radicals without
detaching metal cations [8, 9].
The following reactions have been already investiꢀ
gated: those of the dissociation of PdTPP (TPP is
5,10,15,20ꢀtetraphenylꢀ21H,23Hꢀporphyne dianion)
in an AcOH–(6–8 M) H2SO4 mixture [10]; those of
1
Unfortunately, in the work of T.N. Lomova et al. (Journal of
Physical Chemistry, 2009, vol. 83, no. 6, pp. 1046–1053), there
are several mistakes. On p. 1047 (in the last paragraph on the
–6
–7
left), it should read 1.733
or 413 instead of 560 or 559. In p. 1052 (the second line on the
right), it should read 413 instead of 559.
× 10 instead of 0.86 × 10 , and 414
H2TPP complexes with AgII
,
AuIII [11], PtII, PtIV [12]
in H2SO4; and those of the oxidation of PdTPP and
926

STRUCTURAL MODIFICATION AND KINETIC STABILITY
927
substituted mesoꢀderivatives (2–4) were investigated in an AcOH–H2SO4 mixture over a wide range of mixture
compositions:
R1
Et
Et
Et
Et
R2
Et
R1 = R2 = R3 = R4 = H (PdOEP,
R1 = Ph, R2 = R3 = R4 = H (PdMPOEP,
R1 = R3 = Ph, R2 = R4 = H (Pd5,15DPOEP,
R1 = R2 = R3 = R4 = Ph (PdTetPOEP, ).
1),
N
N
N
2
),
3
Pd
R3
R4
),
N
4
Et
Et
Et
EXPERIMENTAL
6H, CH3, J = 14.5, 14.75). Composition, %, is as folꢀ
lows: the obtained values are 70.60 (C), 6.79 (H),
7.72 (N); the calculated values for С42H48N4Pd are
70.53 (C), 6.76 (H), 7.83 (N). The mass spectrum is
Complexes 1–4 were obtained by the reaction of
PdCl2 with corresponding porphyrin in boiling DMFA
in accordance with the technique described in [15],
after which they were extracted into chloroform and
purified by chromatography on a column filled with
Al2O3 (Brockmann activity grade II) using CHCl3. The
complexes were identified by means of spectral methꢀ
ods.
m/z
= 714.91 (M+), and the calculated value for
С42H48N4Pd is 715.28.
(2,3,7,8,12,13,17,18ꢀOctaethylꢀ5,15ꢀdiphenylpoꢀ
rphynato)palladium (II), Pd5,15DPOEP
.
The EAS in
), is 549 (4.47), 517 (4.28),
403 (5.25). The IR spectrum in KBr,
, cm–1 is as folꢀ
lows: the vibrations of the benzene rings are at 705, 764
C–H); 1091, 1173 ( C–H); 1444, 1600 ( C=C);
3020, 3056 ( C–H); the vibrations of the pyrrole
rings are at 784 ( C–H); 1003, 1020 (C3–C4, C–N,
C–H); 1317 ( C–N); 1450, 1465 ( C=N); 1498,
1632 (skeletal vibrations of the pyrrole ring); the vibraꢀ
tions of ethyl substituents are at 842 ( C–H of methyl
CHCl3, λmax, nm ( log
ε
(2,3,7,8,12,13,17,18ꢀOctaethylporphynato)palꢀ
ladium (II), PdPOEP. The electronic absorption specꢀ
ν
trum (EAS) in CHCl3, λmax, nm
511 (4.35), 392 (5.31). The IR spectrum in KBr,
, cm–1 is as follows: the vibrations of the pyrrole rings
are at 796 ( C–H); 994, 1020 (C3–C4 C–N, C–H);
1305, 1317 ( C–N); 1451, 1464 ( C=N); 1554,
1602, 1632 (skeletal vibrations of the pyrrole ring); the
vibrations of ethyl substituents are at 835, 837 ( C–H
of methyl groups); 1273 ( C–H of methyl groups);
2869, 2963 ( CH3); 2929 ( CH2); the Pd–N vibrations
are at 484. The 1H NMR spectrum (CDCl3,
, ppm;
Hz) is 10.12 (s, 4Hmeso); 4.08 (m, 16H, CH2 = 14);
1.92 (t, 24H, CH3, = 8).
(
log
ε
), is 545 (4.75),
(γ
δ
ν
ν
ν
γ
ν
γ
,
ν
δ
δ
ν
ν
ν
ν
γ
γ
groups); 1261, 1279 (
δ
C–H of methyl groups), 2870,
CH2); the Pd–N vibrations are
δ
2963 (ν CH3); 2929 (
ν
at 486. The 1H NMR spectrum (CDCl3,
δ
, ppm;
= 7);
= 15); 3.88
= 15.25); 2.61 (q, 8H, CH2,
= 22.25); 1.75 (m, 12H, CH3); 0.98 (t, 12H, CH3,
= 15). Composition, %, is as follows: the obtained
ν
ν
δ
J,
J
, Hz) is 9.98 (s, 2Hmeso); 8.14 (d, 4H,
7.62, 7.69 (td, 6H, ꢀPh; = 14.75,
(q, 8H, CH2, = 15.25,
оꢀPh, J
,
J
m
,
p
J
J
J
J
J
J
J
(2,3,7,8,12,13,17,18ꢀOctaethylꢀ5ꢀmonophenylꢀ
porphynato)palladium (II), PdMPOEP. The EAS in
values are 71.97 (C), 6.65 (H), 7.445 (N); the calcuꢀ
CHCl3, λmax, nm
(5.30). The IR spectrum in KBr,
the vibrations of the benzene rings are at 710, 763 (
C–H); 1088, 1167 ( C–H); 1599 ( C=C); 3020,
3057 ( C–H); the vibrations of the pyrrole rings are
at 781 ( C–H); 1003, 1020 (C3–C4 C–N, C–H); phenylporphynato)palladium (II), PdTetPOEP. The
1317 ( C–N); 1450, 1465 ( C=N);1500, 1631 (skelꢀ
etal vibrations of the pyrrole ring); the vibrations of
ethyl substituents are at 840 ( C–H of methyl
(
log
ε
)
, is 550 (4.59), 516 (4.34), 400
lated values for С48H52N4Pd are 72.85 (C), 6.62 (H),
ν
, cm–1 is as follows:
7.08 (N). The mass spectrum is
and the calculated value for С48H52N4Pd is 791.38.
2,3,7,8,12,13,17,18 Octaethylꢀ5,10,15,20ꢀtetraꢀ
m/z ,
= 790.81 (M+)
γ
δ
ν
ν
ꢀ
γ
,
ν
δ
ν
ν
EAS in CHCl3, λmax, nm
(4.21), 433 (5.27). The IR spectrum in KBr,
as follows: the vibrations of the benzene rings are at
702, 760 ( C–H); 1085 ( C–H); 1443, 1598
C=C); 3021, 3057 ( C–H); the vibrations of the
pyrrole rings are at 802 ( C–H); 1003 (C3–C4 C–N,
C–H); 1317, 1329 ( C–N); 1462 ( C=N);1501,
1632 (skeletal vibrations of the pyrrole ring); the vibraꢀ
tions of ethyl substituents are at 860, 879 ( C–H of
methyl groups); 1261 ( C–H of methyl groups);
(
log
ε
)
, is 580 (3.92), 544
ν
, cm–1 is
γ
groups); 1259, 1278 (
2969 (ν CH3); 2929 (
at 486. The 1H NMR spectrum (CDCl3,
, Hz) is 10.00, 10.10 (dd, 3Hmeso
8.17 (d, 2H,
1H, ꢀPh;
δ
C–H of methyl groups); 2870,
CH2); the Pd–N vibrations are
γ
δ
ν
(
ν
ν
δ
, ppm;
γ
,
ν
J
;
J
= 5.5,
= 6.75); 7.63, 7.79 (tt, 2H,
= 15), 3.97 (m, 12 H, CH2); 2.65
J = 2.5);
δ
ν
ν
o
ꢀPh,
J
J
mꢀPh,
p
J = 15,
γ
(m, 4 H, CH2); 1.84 (m, 18 H, CH3); 1.12, 1.00 (tt,
δ
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A
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928
LOMOVA et al.
(a)
545
A
548
548
514
511
515
λ
, nm
(b)
A
3
'
2
'
3
2
1
500
600
700
λ
, nm
5,15
Fig. 1. Electronic absorption spectra of (
1
) PdOEP, (
2
) PdMPOEP, and (3) Pd DPOEP in (a) AcOH in (b) AcOH–H SO
2
≠
4
mixtures at the beginning of the reaction (
2
',
3'
) and after the reaction ends (
1–
3);
C
const.
MP
T
rate constants
and the rate constants
k
at a given
keff
2870, 2969 (
tions are at 486. The 1H NMR spectrum (CDCl3,
ppm; , Hz) is 8.22 (d, 8H, ꢀPh, = 4); 7.68 (m, 8H,
ꢀPh, 4H, ꢀPh), 4.2, 2.4 (dd, 16H, CH2, = 24,
23); 0.5, 1.95 (dd, 24H, CH3, = 7, = 7).
ν
CH3); 2929 ( CH2); the Pd–N vibraꢀ
ν
temperature
density of the reaction mixture at the working waveꢀ
length and at different concentrations of acid, optiꢀ
Т were determined in terms of optical
δ,
A
J
o
J
m
p
J
J =
mizing the log(A0 – A )/(A – A )
and logkTeff
logC0H SO relations, respectively, by the least squares
–τ
–
J
J
∞
τ
∞
The spectra were measured using the following
instruments: an Agilent 8453 UVꢀVis, a Specord Mꢀ40,
an SFꢀ26 (UV/Vis spectra), a Specord M80, a Bruker
Tensor 27 (IRꢀspectra), a Bruker (200 MHz, HMDS)
and a Bruker AC 250 (1H NMR), and an
MS(MALDIꢀTOF) Bruker Autoflex (mass spectra).
Elemental analysis was performed using a Euro EA
3000 analyzer.
2
4
method. The activation energy
optimizing the linear logkTeff –1/
Е
T
was determined by
relation by the least
≠
squares method. The entropy of activation, S was
calculated according to the following formula:
Δ
= 19.1 logkT
+ E/T – 19.1 logT – 205. (1)
≠
ΔS
H2SO4 solutions were prepared gravimetrically
from 100% AcOH and H2SO4 monohydrate. 100%
AcOH was obtained from frozen AcOH (chemically
pure grade) by stagewise defrosting; sulfuric acid
monohydrate was prepared from oleum (chemically
pure grade) and H2SO4 with potentiometric control
over the concentration [16]. The reaction kinetics
were studied spectrophotometrically: the solutions
were thermostated in the cell of the spectrophotomeꢀ
ter chamber, and the error was 0.1 K. The effective
RESULTS AND DISCUSSION
The obtained data reliably characterize the strucꢀ
tures of complexes 1–4. The EASes of complexes in
100% AcOH (Fig. 1) are similar to the spectra in chloꢀ
roform. They do not change over time or upon heating
to 373 K. A transformation with a change in EAS is
observed for complexes 1–3 in the AcOH–H2SO4
mixtures with
= 0.6–8.0 mol/l upon heating
C
H2SO4
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STRUCTURAL MODIFICATION AND KINETIC STABILITY
929
A
A
551
548
602
686
603
687
2
3
1
2
λ
, nm
Fig. 3. Electronic absorption spectra of the oxidation reacꢀ
tion products of PdOEP ( ), PdMPOEP ( ) and
3
1
1
2
5,15
Pd DPOEP (3) in CHCl .
3
500
600
700
λ
, nm
Complexes
1–3 are oxidized in concentrated
Fig. 2. Electronic adsorption spectra of PdTetPOEP in
chloroform ( ), of PdTetPOEP ( ) and H TetPOEP ) in
the AcOH–H SO mixtures; = 298 K.
H2SO4 as they dissolve, as we can see from the electron
1
2
2
(3
2
absorption spectra. Complex
4 and PdTPP react
T
4
slowly; the rate constant is 10–7 s–1 in 17.5–18.2 M
H2SO4 at 298 K. The corresponding constant for
(333–363 K), and for complex
4
in the AcOH–H2SO4
0
PdTPP is ~10–6 s–1 at
= 16.3–17.4 mol/l [13].
C
H2SO4
0
mixtures with
from 0.1 to 1.0 mol/l even at
C
H2SO4
The oxidation rates of complexes
AcOH–H2SO4 mixtures were investigated experimenꢀ
tally. The ln(C0 and values are proportional,
1–3 in the
298 K. In the spectra of the products (Figs. 1 and 2,
curve ), the absorption bands are bathochromically
2
/C
)
τ
τ
shifted relative to the EAS in AcOH; the background
absorption also grows, and new absorption bands
appear in the nearꢀUV, visible, and nearꢀinfrared
regions. The electronic absorption spectra of the prodꢀ
ucts of transformations (Figs. 1–3) do not coincide
with the spectra of H2P porphyrins (Fig. 4). The backꢀ
ground and the absorption spectra with additional
bands, which are similar to the spectra shown in
which follows from the accuracy of the effective rate
constants of the first order (keff) for metalloporphyrins
T
(Table 1). In logarithmical coordinates, the
value
keff
correlates linearly (
ρ
= 0.98–0.99) with the concenꢀ
0
tration,
(Table 2). The order in terms of acid
C
H2SO4
(n), which was found by the line slope in the given
coordinates for PdOEP and PdMPOEP is close to 2
Figs. 1–3, were described in [9, 17] for ꢀcation radiꢀ
π
and to 1 for Pd5,15DPOEP. The reaction is thus
cal forms of metalloporphyrins obtained by chemical
and electrochemical oxidation. According to the data
from electronic spectroscopy, complexes 1–4 thus
undergo electronic oxidation under the conditions
described in the beginning of this section.
A comparison of the electronic absorption spectra
for the initial complexes in the reaction media (Fig. 1,
described by the following equation for complexes
and
1
2:
2
−dCMP /dτ = kCMP(CH0 SO
)
4
(3)
2
and for complex 3 by:
–dCPd5,15DPOEP/dτ = kCPd5,15DPOEPCH0 SO
.
4
(4)
curve
720–725 nm that appeared in the spectra of comꢀ
pounds and , and its absence in the spectrum of
compound . According to [13, 14, 18], this kind of
2'–3') shows the absorption band in the range of
2
Taking into account the spectral data, according to
which the final form of PdP is cation radicals, PdP+•
1
2
,
3
and the known [19] oxidizing properties of H2SO4 in
the presence of atmospheric oxygen, the overall reacꢀ
tion equation for PdP oxidation in the AcOH–H2SO4
mixtures can be written as:
spectrum indicates the presence of an Hꢀassociate of
PdP (PdP···H+···R, where R is an acid anion or a molꢀ
ecule of acid or solvent) or of other metalloporphyrins
that forms in acid mediums from complexes with a
high electron density in the macrocycle. It is now clear
PdP···H+···R + О2 + Н+
→
PdP+• + HO•2
why complex
nyl substituents, does not produce this form, in conꢀ
trast to complexes and , which participate in the
3, which has two electronꢀacceptor pheꢀ
(5)
+ H+···R, complex
1
и
2,
1
2
i
PdP + О2 + Н+
→
PdP+•
+
,
complex
3, (6)
HO2
following equilibrium:
K
−
PdP + H+···R
PdP···H+···R.
(2) where R =
.
HSO4
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930
LOMOVA et al.
503
560
508
548
533
499
A
572
574
621
567
592
620
571
537
541
1
2
4
624
3
5
6
λ
, nm
Fig. 4. Electronic absorption spectra in chloroform (1–3) and in AcOH–H SO (4–6) of H OEP (1, 4), H MPOEP (2, 5), and
2 4 2 2
5,15
H
DPOEP (3, 6); T = 298 K.
2
It is obvious that, prior to the process of electron
–dCPdP/dτ = –dC(O )PdP/dτ = kslowC(O )PdPCH SO
2 2 4
2
transfer from macrocyclic complex to oxygen, the folꢀ
lowing equilibria of ionization (7) and O2 coordinaꢀ
tion on PdP are attained:
2
=
kslowKa–1CPdPCH+···RCH SO = kslowK–a1CPdP(C0H SO ) ,
(10)
2
4
2
4
H2SO4 + AcOH ↔ AcOH+2 + HSO4–;
Ka = [AcOH+2 ][HSO4–]/[H2SO4],
–dCPd5,15
/dτ = –dC(O )PdP/dτ
2
DPOEP
(7)
(11)
=
kslow
C ,
(O )PdPCH SO = kslowCPd5,15DPOEPCH0 SO
2 2 4 2 4
PdP + O2
↔
(O2)PdP,
(8)
where
is the equilibrium concentration,
C
H2SO4
[
H2SO4].
The rate constants
of reactions for complexes
where Ka is the ionization constant of H2SO4 in the
k
and the activation parameters
, calculated with allowꢀ
AcOH medium, according to [20] and [21], and Ka =
p
1–3
4.3 and 4.5. Equilibrium (8) is most likely shifted right
due to the excess amount of oxygen in comparison to
the PdP amounts. It is clear that in the reaction for
ance for the orders according to components, are
listed in Table 2. Like (3), the third order equation was
obtained for the oxidation reaction of PdTetPOEP
and PdTPP in H2SO4 earlier [13]. The equilibrium
concentration of [H2SO4] in water, which differs
sharply from its initial concentration, is found in the
kinetic equation in the second degree, and PdP enters
into the reaction in its Hꢀassociated form, despite the
presence of four phenyl substituents [22]. As was menꢀ
complexes
1 and 2, the coordination of the O2 moleꢀ
cule is accompanied by the decomposition of Hꢀaccoꢀ
siate, PdP···H+···R. Slow singleꢀelectron oxidation
occurs upon the influence of H2SO4 molecules, the
particles with the highest concentration in the reacꢀ
tion medium:
tioned above, complexes
1–3 yield radical forms
immediately after dissolving in H2SO4, preventing us
from measuring the formation of Hꢀassociated forms
by spectral methods.
It is possible to analyze the dependence of keff on
the total acidity (h0) of AcOH–H2SO4 at 298 K using
the known [23] values of the acidity function H0. The
order of the oxidation reaction by H+ found from the
(O2)PdP + H2SO4 → PdP+• + HO2•
(9)
+
HSO–4 , slowly.
The difference between equations (3) and (4),
however, indicates the absence of a single mechanism
of oxidation. The difference between the mechanisms
is the participation of different forms of complexes in
298
slopes of log
–
f
(
H0
)
is close to 2 for PdOEP
= 0.98), to 1 for PdMPOEP
keff
(log 298 = 2.3H0 – 12.9,
ρ
the reaction: for complexes 1, 2, it is Hꢀassociates; for
keff
complex
3
, it is the molecular form. If we assume that
298
keff
(log
= 0.9H0 – 10.2,
Pd5,15DPOEP (log 298 = 0.3
ρ
= 0.997), and to 1/2 for
0 – 6.5, = 0.99). As we
0
+
in the expression
[H SO ] + [
2
], the
AcOH2
CH SO
=
4
4
2
H
ρ
keff
second component is negligible due to the low value of
can see, only in diluted H2SO4 solutions is the order of
0
p
Ka and [H SO ] ~
, the rates of reactions (5)
H2SO4
C
2
4
the reaction by the total concentration of protons simꢀ
and (6) limited by stage (9) for complexes
1
and
2 and
0
ilar to the order with
(3). For complexes 2 and
C
H2SO4
for complex
tions:
3 can be expressed by the following equaꢀ
3, the order decreases, but there is a linear logkeff –
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A
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STRUCTURAL MODIFICATION AND KINETIC STABILITY
931
Table 1. Effective kinetic parameters of PdP oxidation in AcOH–H2SO4 mixtures
keTff
×
105, s–1
–ΔS#eff
, J/(mol K)
0
T, K
Eeff, kJ/mol
, mol/l
C
H2SO4
PdOEP
0.07 0.003
7.7 0.2
11.3 0.6
15.2 0.6
0.15 0.05
0.893
298
353
358
363
298
353
358
363
298
353
358
363
298
353
358
363
76
69
6
4
117 17
132 13
1.07
1.25
1.43
11.0
15
21
1
1
1
0.26 0.05
16.0 1.5
63
58
6
4
148 17
158 13
21
29
2
3
0.7 0.03
20
27.0 1.5
35
2
3
PdMPOEP
0.0146 0.003
1.60 0.15
2.3 0.2
2.79
3.22
3.65
4.07
4.50
2.40
3.08
3.43
4.11
298
348
353
358
298
348
353
358
298
348
353
358
298
348
353
358
298
348
353
81
79
75
75
4
6
4
2
111 13
115 20
124 13
3.5 0.3
0.021 0.007
2.0 0.2
2.8 0.2
4.28 0.40
0.035 0.007
2.7 0.1
3.8 0.3
5.6 0.7
0.0425 0.0045
3.3 0.2
4.7 0.3
124
7
6.85 0.60
0.075 0.006
3.9 0.3
68
141
5.4 0.3
Pd5, 15DPOEP
0.507 0.080
1.63 0.10
1.93 0.15
2.18 0.20
0.683 0.080
2.12 0.20
2.5 0.15
2.8 0.2
298
333
338
343
298
333
338
343
298
333
338
343
298
333
338
343
28
27
4
3
260 13
260 10
0.81 0.04
2.54 0.24
2.95 0.20
3.4 0.3
27
23
1
2
259
269
3
7
1.2 0.1
3.15 0.20
3.60 0.2
4.03 0.35
Note: The rate constants at 298 K were found by extrapolating the keTff –1/T relation.
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A Vol. 85 No. 6 2011

932
LOMOVA et al.
PdOEP > Pd5,15DPOEP > PdMPOEP, in which they
are apparently found in order of the rise in their oxidaꢀ
tion potentials and the degree of HOMO stabilization.
The potentials of the singleꢀelectron electroreduction
of H25,15DPOMP and H2OMP are Е1/2 = –0.51 and
–0.75 eV, and ЕHOMO = 6.8826 and –6.8256 eV [25],
respectively. The analogous potentials for PdP ligands
were unfortunately not measured; for CuOEP and
CuTPP, they are –1.46 and –1.20 eV, respectively. As
we can see from the data, the ligands that include
Table 2. Rate constants (k) and activation parameters (E,
Δ
S#) of the PdP reaction in AcOH–H2SO4 mixtures
k
×
106,
mol–2 l2 s–1
E
,
–
Δ
S#,
J/(mol K)
T, K
kJ/mol
PdOEP
298
353
358
363
1.15
100
70
1
7
5
131
3
138
191
β
ꢀalkyl substituents are reduced more than mesoꢀpheꢀ
PdMPOEP
0.008 91
nylꢀsubstituted derivatives in both the free and coordiꢀ
nated states. The process of singleꢀelectron oxidation
is characterized by inverse relationships: the Е0(ox) valꢀ
ues for CuOEP and CuTPP are +0.79 and +0.90 eV,
respectively, in DMSO and in butyronitrile and
DMSO [25].
298
348
353
358
102 23
2.2
3.3
5.3
PdD5, 15POEP
298
333
338
343
1.2 33
254 16
The absence of any effect from a growing degree of
substitution indicates the overlap of two competing proꢀ
cesses: the formation of Hꢀassociate and a functional
substitution that changes the oxidation potential. The
5.5
6.8
7.8
stability of Ni and Pt complexes with ꢀalkylꢀsubstiꢀ
β
Note: The rate constants at 298 K were found by extrapolating the
tuted porphyrins was not studied, but we can compare
complexes with cations of the same charge. The PdP
complexes are more stable than partially mesoꢀphenyl–
substituted CuIIP complexes [24, 26]. These complexes
do not dissociate in the AcOH–H2SO4 media in which
the kinetics of CuP dissociation was studied. The stabilꢀ
5,15
k – 1/T relation. In the case of PdD POEP, the k value has
–1 –1
the dimension mol l s
.
f
(
H0
) correlation, most likely because there is proporꢀ
0
tionality between the
and H0 values in the soluꢀ
C
H2SO4
ity of PdII complexes with
ened, due most likely to the contribution from the
dative Pd ꢀbond that occurs because of the lowꢀ
spin state of Pd in PdP with antibinding orbital, in
4
d8 configuration is heightꢀ
tion composition range of 2–4 M H2SO4 in AcOH [24].
A variable order of for different PdP in AcOH–
H2SO4 of the same composition and at different valꢀ
n
→
N
π
T
dx2 −y2
ues is not in agreement with the dissociation behavior
of metalloporphyrins [7]. This indicates yet another
addition to stabilization by the formation of Pd
←
N πꢀ
bonds (dxz and dyz orbitals).
nature of the PdP transformation in AcOH–H2SO4
In accordance with the oxidation rate, PdP are
arranged in the following sequence: PdTetPOEP > and the specific electronic configuration of CuII (3d9
.
Due to the increasing distortion of the macrocycle
)
E, eV
d
2
x
2
d
2
x
2
−
−
y
y
−
9
eg
(π)
−10
−11
−
12
1
π
π
(Q)
2
d
d
dxy
d
d
dxy
2
2
z
z
π
π
a2
a1
u
u
Fig. 5. Energies of the NiP boundary orbitals according to the IEH model, and a schematic representation of the reasons why the
hypsochromic shift ( ) of Q bands appears in the EAS.
1, 2
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A
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No. 6 2011

STRUCTURAL MODIFICATION AND KINETIC STABILITY
933
7. B. D. Berezin and T. N. Lomova, Reactions of Dissociaꢀ
tion of Complex Compounds (Nauka, Moscow, 2007) [in
Russian].
8. T. N. Lomova, S. V. Zaitseva, O. V. Molodkina, and
T. A. Ageeva, Koord. Khim. 25, 424 (1999) [Russ. J.
Coord. Chem. 25, 397 (1999)].
in CuP, there is no contribution from dative
to the stability of complexes. The presence of the
vacant
orbital in PdP is well illustrated by the 1H
NMR spectra (see above) that are typical for diamagꢀ
netic metalloporphyrins, and by hypsochromic shift of
Q and B bands in the electronic absorption spectra of
PdP, as compared to the normal spectra of ZnP [27,
28]. The maxima of Q(0, 0), Q(0, 1) and B(0, 0) bands
π
ꢀbonds
dx2 −y2
9. N. Carnieri and A. Harriman, Inorg. Chim. Acta 62
,
103 (1982).
10. T. N. Lomova, N. I. Volkova, and B. D. Berezin, Zh.
for complex 1 are thus at 553.5, 519, and 385 nm, and
Neorg. Khim. 32, 969 (1987).
at 572.0, 535.0, and 385.5 nm for ZnOEP [28]. The
similar maxima for NiOEP (558.0, 522.0, and
384.5 nm) take the middle position. The HOMO–
LUMO energies for NiP were calculated in [29] by
means of an extended Hückel method that employed
11. E. Yu. Tyulyaeva and T. N. Lomova, Koord. Khim. 27
,
465 (2001) [Russ. J. Coord. Chem. 27, 433 (2001)].
12. E. Yu. Tyulyaeva, T. N. Lomova, and L. G. Andrianova,
Zh. Neorg. Khim. 46, 432 (2001) [Russ. J. Inorg.
Chem. 46, 371 (2001)].
13. E. Yu. Tyulyaeva, O. V. Kosareva, M. E. Klyueva, and
T. N. Lomova, Zh. Neorg. Khim. 53, 1504 (2008)
[Russ. J. Inorg. Chem. 53, 1405 (2008)].
the fourꢀorbital method. The formation of
with the partial transfer of electron density from metal
to macrocycle and vice versa in complexes (anaꢀ
π
ꢀbonds
1–4
logs of NiP) is shown in Fig. 5, which presents data
from [29, 30]. The consequence of both effects is a
hypsochromic shift of Q bands, due to the destabilizaꢀ
tion of the eg orbital (Fig. 5, transition 1) and the staꢀ
bilization of the a2u orbital (Fig. 5, transition 2).
14. T. N. Lomova, E. Yu. Tyulyaeva, and M. Yu. Tipugina,
Achievements of Porphyrine Chemistry, Vol. 4, Ed. by
O. A. Golubchikov (NII khimii SPbGU, St. Petersꢀ
burg, 2004) [in Russian].
15. A. S. Semeikin, in Proceedings of the 29th Sci. Session of
Russian Seminar on Chemistry of Porphyrine and their
Analogue (Ivanovo, 2006), p. 19.
16. R. J. Gillespie and E. A. Robinson, in Nonaqueous Solꢀ
vent Systems, Ed. by T. C. Waddington (Academic
Press, New York, 1965; Khimiya, Moscow, 1971).
CONCLUSIONS
The high stability of PdP to acids and oxygen is due to
firm σπꢀbinding of Pd. The modification of mesoꢀposiꢀ
tions of ligand can be considered as one way to change 17. G. H. Brown, F. R. Hopf, T. J. Meuer, and D. G. Whitꢀ
ten, J. Am. Chem. Soc. 97, 5358 (1975).
erties are exhibited in oxidation reactions and in the reacꢀ 18. T. N. Lomova, E. G. Mozhzhukhina, L. P. Shorꢀ
the electronꢀdonor properties of complexes. These propꢀ
manova, and B. D. Berezin, Zh. Obshch. Khim. 59
,
tions of partial proton transfer from a medium.
2317 (1989).
19. G. Rozovskii, O. Gal’dikene, Kh. Zhelis, and
Z. Motskus, Zh. Neorg. Khim. 41, 53 (1996) [Russ. J.
Inorg. Chem. 41, 48 (1996)].
20. Yu. A. Fialkov, Solvent as an Agent of Chemical Process
Control, Ser. Khimiya (Znanie, Moscow, 1988), No. 6
[in Russian].
ACKNOWLEDGMENTS
This work was supported by the Presidium of Rusꢀ
sian Academy of Sciences, project no. 18; by the Rusꢀ
sian Foundation for Basic Research, project nos. 07ꢀ
03ꢀ00639, 09ꢀ03ꢀ97556; by the federal target program
Scientific and Scientific–Pedagogical Personnel of an
Innovative Russia for 2009–2013, state contract
no. 02.740.11.0106; and the analytical departmental
target program Developing the Scientific Potential of
Higher Education, no. 2.2.1.1/2820. The authors thank
Prof. A.S. Semeikin (Ivanovo State University of Chemꢀ
istry and Technology) for synthesizing the complexes.
21. A. M. Shkodin and L. I. Karkuzaki, Zh. Fiz. Khim. 33
2795 (1959).
22. M. E. Klyueva, T. N. Lomova, and B. D. Berezin, Zh.
Fiz. Khim. 76, 692 (2002) [Russ. J. Phys. Chem. A 76
603 (2002)].
,
,
23. R. J. Motekaitis, X. B. Cox, P. Taylor, et al., Can. J.
Chem. 60, 1207 (1982).
24. M. E. Klyueva, E. E. Suslova, and T. N. Lomova, Zh.
Obshch. Khim. 73, 1377 (2003) [Russ. J. Gen. Chem.
73, 1303 (2003)].
25. M. I. Bazanov and A. V. Petrov, Organic Complexes with
Metals: Electrochemistry, Electrocatalysis, Thermochemisꢀ
try (IvI GPS MChS Rossii, Ivanovo, 2007) [in Russian].
26. O. V. Kosareva, Extended Abstract of Candidate’s Disꢀ
sertation in Chemistry (Ivanovo, 2007).
27. T. N. Lomova and B. D. Berezin, Koord. Khim. 27, 96
(2001) [Russ. J. Coord. Chem. 27, 85 (2001)].
REFERENCES
1. C. G. Claessens, D. GonzalezꢀRodriguez, Ya. Rio,
et al., J. Porphyr. Phthalocyan. 10 (4–6), 248 (2006).
2. A. A. Lobanovskaya, V. V. Vasil’ev, and I. A. Blinova, in
Proceedings of the 24th Intern. Chugaev Conference on
Coordination Chemistry (St.ꢀPetersburg, 2009), p. 311.
3. I. Okura, J. Porphyr. Phthalocyan. 10 (4–6), 361 (2006).
4. T. Huakutake, H. Taguchi, H. Sakaue, and H. Nishide,
J. Porphyr. Phthalocyan. 10 (4–6), 670 (2006).
28. L. J. Boucher, Coord. Chem. Rev.
29. M. Gouterman, in The Porphyrins (Academic, San
Francisco, London, New York, 1978), Vol. 3, p. 1.
7, 289 (1972).
5. Yu. S. Avlasevich, S. Baluschev, J. Jacob, et al., J. Porꢀ
phyr. Phthalocyan. 10 (4–6), 425 (2006).
6. M. E. Klyueva, O. V. Kosareva, T. N. Lomova, and
M. V. Kluyev, J. Porphyr. Phthalocyan. 10 (4–6), 714 30. M. Zerner and M. Gouterman, Theor. Chim. Acta 4,
(2006).
44 (1960).
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