The state of 5,10,15,20-tetraphenyl-21H,23H-porphine rhenium(V) complexes in solutions of acids

Article abstract of DOI:10.1134/S0036023613110223

The spectral properties (UV/Vis, IR, ¹H NMR) and stability of diverse forms of 5,10,15,20-tetraphenyl-21H,23H-porphine rhenium(V) complexes in neutral and protolytic solvents have been studied. Quantitative characteristics have been obtained for the reactions of formation and interconversion of the μ-oxo dimeric and monomeric rhenium(V) complex species in the benzene-AcOH system and dissociation at the coordination center of the H⁺- associated form of the monomeric rhenium(V) complex in mixed H ₂O-H₂SO₄ solvents in a wide range of component concentrations. It has been shown that the stability of the coordination center of the rhenium(V) complexes sharply depends on the nature of a second acido ligand, in addition to the coordinated porphyrin.

Full text of DOI:10.1134/S0036023613110223

ISSN 0036ꢀ0236, Russian Journal of Inorganic Chemistry, 2013, Vol. 58, No. 11, pp. 1366–1373. © Pleiades Publishing, Ltd., 2013.
Original Russian Text © E.Yu. Tyulyaeva, N.G. Bichan, T.N. Lomova, 2013, published in Zhurnal Neorganicheskoi Khimii, 2013, Vol. 58, No. 11, pp. 1522–1530.
PHYSICAL CHEMISTRY
OF SOLUTIONS
The State of 5,10,15,20ꢀTetraphenylꢀ21H,23Hꢀporphine
Rhenium(V) Complexes in Solutions of Acids
E. Yu. Tyulyaeva, N. G. Bichan, and T. N. Lomova
Krestov Institute of Solution Chemistry, Russian Academy of Sciences, ul. Akademicheskaya 1, Ivanovo, 153045 Russia
eꢀmail: teu@iscꢀras.ru
Received September 20, 2012
Abstract—The spectral properties (UV/Vis, IR, 1H NMR) and stability of diverse forms of 5,10,15,20ꢀtetꢀ
raphenylꢀ21
H
,23
H
ꢀporphine rhenium(V) complexes in neutral and protolytic solvents have been studied.
ꢀoxo
Quantitative characteristics have been obtained for the reactions of formation and interconversion of the
μ
dimeric and monomeric rhenium(V) complex species in the benzene–AcOH system and dissociation at the
coordination center of the H+ꢀassociated form of the monomeric rhenium(V) complex in mixed H2O–
H2SO4 solvents in a wide range of component concentrations. It has been shown that the stability of the coorꢀ
dination center of the rhenium(V) complexes sharply depends on the nature of a second acido ligand, in addiꢀ
tion to the coordinated porphyrin.
DOI: 10.1134/S0036023613110223
Porphyrin complexes of metals (MP) in the middle tion [12] were proved by thinꢀlayer chromatography
of inserted decades of the IUPAC Periodic table of the (TLC) on Silufol with the use of the CHCl3–2%
elements are distinguished by the diversity of strucꢀ C2H5OH solvent (Rf = 0.42).
tures, depending on the nature of the ligand and the
charge of the central ion. Rhenium, whose oxidation
state can change from –1 to +7, form a large number
of compounds with different structures with macrocyꢀ
clic ligands, in particular, with porphyrins and their
analogues [1–5]. Many of them have been used in
development of new materials for pharmacology [6, 7]
and catalysis [8]. Since the forms of complexes in
coordinating solvents are even more diverse, studying
their nature and structure is an important task. This
fully applies to metal porphyrins, with their high staꢀ
bility even in media with a high content of protons [9]
and the ease of formation of stable H+ꢀassociated and
oxidized forms [9–11]. Chemical reactions of metal
porphyrins with proton or electron transfer are little
understood, notwithstanding their tremendous role in
natural and some of the technical processes.
[O=ReTPP]2O
.
Yield, 75%. UV/Vis (CHCl3,
λmax, nm (log
ε
): 620 (sh), 582 (4.51), 461 (5.34), 333
(4.88).
IR (solid random layer,
ents—702, 754 (
ν
, cm–1): phenyl substituꢀ
(C–H)); 1072, 1179 ( (C–H));
1485, 1575, 1597 ( (C=C)); 2954, 3056 ( (C–H))
pyrrole groups—801 (C–H)); 1018 (C3–C4, (C–
N), (C–H)); 1341 ( (C–N)); 1440 ( (C=N)); coorꢀ
γ
δ
ν
ν
;
(
ν
γ
ν
δ
ν
dination center—468 (Re–N); 568, 630, 854 (Re–
O–Re); 961, 946 (Re=O).
For C88H56N8O3Re2 anal. calcd. (wt %): C, 64.22;
H, 3.41; N, 6.81.
Found (wt %): C, 63.14; H, 3.52; N, 5.59.
1H NMR (CDCl3,
= 7.6), 8.79 (s, 16H ), 8.01 (t, 8Hm,
δ
, ppm,
J
, Hz): 9.07 (d, 8Hо,
= 7.6), 7.60 (t,
J = 7.6), 7.04, 6.87 (t, t,
8Ho',
J
J
β
8Hp,
J
= 7.6), 7.47 (d,
In continuation of our ongoing studies in this field,
this work is aimed at studying the forms of existence and
stability of μꢀoxoꢀbis[(oxo)(5,10,13,20ꢀtetraphenylꢀ
J
= 7.6, J = 7.6).
8Hm',
1H NMR (CDCl3 + 0.38 M AcOH,
δ, ppm
J, Hz)
for O=Re(OH)TPP: 9.37 (s, 8H ), 8.42 (d, 4Hо,
7.32), 8.30 (d, 4Hо,
2.25 (s, 1H, –OH); for O=Re(OAc)TPP: 9.43 (s,
J
=
β
21H,23Hꢀporphinato)rhenium(V)] [O=ReTPP]2O in
J
= 7.32), 7.85 (m, 8Hm, 4Hp),
mixed solvents with different content of acids AcOH
and H2SO4 by spectroscopy, chemical kinetics, and
equilibrium methods. [O=ReTPP]2O has been syntheꢀ
sized previously by the reaction of chlororhenic acid with
⎯
8H , 8.17 (d, 8Hо,
J = 7.32), 7.49 (m, 8Hm, 4Hp), 1,25
β
(m, 3H, –CH3).
1H NMR (CDCl3+ 6 M AcOH,
δ, ppm) for
5,10,13,20ꢀtetraphenylꢀ21H,23Hꢀporphine (H2TPP) in
O=Re(OAc)TPP: 9.38 (s, 8H ), 8.38 (m, 4Hо), 8.24
boiling phenol [12].
β
(m, 4Hо), 7.8 (m, 8Hm, 4Hp), 1.25 (m, 3H, –CH3).
1H NMR (CD3COOD,
δ, ppm,
J, Hz) for
EXPERIMENTAL
O=Re(OAc)TPP: 9.51 (s, 8H ), 8.70 (d, 4Hо,
J
=
The identity and chromatographic purity of the 7.32), 8.37 (m, 4Hо,
[O=ReTPP]2O complex after synthesis and purificaꢀ 1.25 (m, 3H, –CH3).
J
= 7.32)β, 7.90 (m, 8Hm, 4Hp),
1366

THE STATE OF 5,10,15,20ꢀTETRAPHENYLꢀ21H,23HꢀPORPHINE RHENIUM(V)
1367
1H NMR (D2SO4,
O=Re(X)TPP: 9.76 (s, 8H ) 9.14 (m, 8Hо), 8.52 (m,
δ
, ppm) for monomeric
A
461
β
8Hm, 4Hp); for H2TPP: 8.8 (s, 8H ), 8.3 (m, 8Hо), 7.78
(t, 8Hm, 4Hp).
β
333
333
1
The UV/Vis spectra were recorded on Agilent 8453
UVꢀVis and Specord Mꢀ400 spectrophotometers. The
IR spectra were recorded on a VERTEX 80v spectroꢀ
photometer. The 1H NMR spectra were recorded on a
Bruker AVANCE III 500 spectrometer. Elemental
analysis was carried out on a Flash EA 1112 Series
CHNSꢀO analyzer. Solid layers for IR spectral study
were prepared by evaporation of the CHCl3 solvent
from a complex solution on a silica plate.
498
2
619
582
In the thermodynamic and kinetic experiments for
studying the stability of the ꢀoxo dimer [O=ReTPP]2O
µ
at different proton concentrations and for determining
the dissociation rates of the monomeric complex form
in protonꢀcontaining solvents at different temperaꢀ
tures, the absorptivities of solutions for absorption
band maxima at, respectively, 461 and 690 nm were
measured. Measurements were performed in cells with
a pathlength of 1 cm, placed in a special thermostated
chamber in the cell compartment of the spectrophoꢀ
tometer. The error in temperature determination was
0.1 K. The UV/Vis spectra were recorded as graphs
and tables for subsequent mathematical processing. Sulꢀ
furic acid of high concentrations was prepared from
chemically pure H2SO4 and 100% H2SO4 obtained from
chemically pure oleum with potentiometric monitorꢀ
ing of the water content [13]. 100% acetic acid was
prepared by fractional thawing of glacial acetic acid
(water content, 0.015%). The concentration of aqueꢀ
ous sulfuric acid was determined by acid–base titraꢀ
tion with an error no more than 0.15%.
λ
, nm
Fig. 1. UV/Vis spectra of [O=ReTPP] O in (1) chloroform
2
and (2) 100% AcOH.
formed by the leastꢀsquares method with the
Microsoft Excel program. The activation energies and
and S ) of the reaction were determined
from the temperature dependence of rate constants.
≠
entropies (
E
Δ
RESULTS AND DISCUSSION
To determine complex species in solutions, we first
carried our comparative analysis of their UV/Vis specꢀ
tra in solvents with different acidity. The spectra of
[O=ReTPP]2O in an aprotic solvent and AcOH (Fig. 1)
are rather different: the absorption maxima in the visꢀ
ible range of the spectrum are bathochromically
shifted by ~40 nm, and the absorption near 330 nm is
enhanced. Since such a spectral pattern is observed for
monomeric MV porphyrin complexes, in particular,
for МоV and WV [14], we believe that this fact confirms
the constancy of the charge of the ReV central cation
in the complex with AcOH. Extraction of the complex
from an acetic acid solution into CHCl3 has experiꢀ
mentally demonstrated the reversibility of the complex
transformation. On the basis of data in [15], we may
To a 10–4 M solution of [O=ReTPP]2O in CDCl3
,
a calculated volume containing a specified AcOH
concentration was added, and a spectrum was
recorded.
The MP dimer–monomer equilibrium constants
were determined from Eq. (1) by the leastꢀsquares
method using the Microsoft Excel program.
Ap − Ao
A∞ − Ao
Ap − Ao
1
(1)
K =
,
assume that reversible cleavage of the ꢀoxo bridge
µ
n
Ap − Ao
A∞ − Ao
⎛
⎞
CL − CM0 P
occurs in a solution of the [O=ReTPP]2O in AcOH. To
quantify the equilibrium, the reaction of
[O=ReTPP]2O with AcOH was carried out in benꢀ
zene. Benzene, a nonpolar solvent, poorly solvates the
metalloporphyrin molecule at the coordination cenꢀ
ter. This enables to study the thermodynamics of equiꢀ
librium systems, ignoring the effect of the solvent.
1 −
⎜
⎝
⎟
⎠
A∞ − Ao
0
where
and C are the initial concentrations of,
L
CMP,
respectively, MP and AcOH in benzene; Ао, Ар, and А
∞
are the absorptivities at the working wavelength for
solutions of the dimer, the equilibrium mixture at a
definite AcOH concentration, and the resulting
monomeric complex. The relative error of determinaꢀ
The reaction of [O=ReTPP]2O with AcOH in benꢀ
zene was studied at 298 K in a wide range of AcOH
tion of
K was no more than 15%.
concentrations (2.92
×
10–4–2.92 mol/L). Figures 2
The optimization of the numerical values of MP and 3 show the UV/Vis spectra of [O=ReTPP]2O in
dissociation constants, activation energy, and reaction benzene as a function of AcOH additions and the corꢀ
order in proton (keff, E, and n, respectively) and deterꢀ responding titration curves. The spectrum of
mination of rootꢀmeanꢀsquare deviations were perꢀ [O=ReTPP]2O in benzene is a line with the highest
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 58 No. 11 2013

1368
TYULYAEVA et al.
A
A
461
A
(а)
461
1.5
(b)
A
1.3
1.2
(а)
340
1.0
0.5
(b)
498
500
1.0
1.0
0.5
0
340
0
0.005
0.010
CAcOH, mol/L
0.5
0
0
1
2 CAcOH, mol/L
λ
, nm
λ
, nm
400
600
300
400
500
600
Fig. 2. (a) UV/Vis spectra of [O=ReTPP] O in the benꢀ
2
Fig. 3. (a) UV/Vis spectra of [O=ReTPP] O in the benꢀ
2
zene–acetic acid solvent as a function of the AcOH conꢀ
centration and (b) the titration curve at the first stage.
zene–acetic acid solvent as a function of the AcOH conꢀ
centration and (b) the titration curve at the second stage.
–6
–4
–6
–2
= 8.3
×
10 mol/L;
С
= 2.92
×
10 –
С
[O=ReTPP]2O
–2
AcOH
= 8.3
×
10 mol/L;
С
= 1.30
×
10 –
С
[O=ReTPP]2O
AcOH
1.30
×
10 mol/L.
2.92 mol/L.
maximum at 461 nm. As follows from Figs. 2 and 3,
the band at 340 nm becomes stronger and the band at
461 nm becomes weaker and broader and is bathoꢀ
chromically shifted by about 40 nm as the AcOH conꢀ
centration in solution increases. There are two families
of spectral curves in which isosbestic points are retained
at, respectively, 425, 480 nm and 424, 604 nm. The first
family represents a series of bands with increasing
absorptivity near 333 nm and decreasing absorptivity at
The second equilibrium stage is observed at AcOH
concentrations 1.30
10–2–2.92 mol/L and is characꢀ
×
terized by a considerably lower constant K2
= (3.5
Ap − Ao
log
0.7)
×
101. The tan
β
of the
versus logCAcOH
A∞ − Ap
2). It is evident that one
plot is nearly 2 (1.9) (Fig. 4,
AcOH molecule is spent on protonation of the
hydroxy ligand, whereas the second molecule is only
involved in extra coordination in the molecular form:
λmax = 461 nm (CAcOH = 2.92
×
10–4–1.30 10–2 mol/L)
×
(Fig. 1). The second family of spectral curves is a series
of bands with increasing absorptivity at λmax = 333 nm
and the bathochromic shift of the band at 461 to
O=Re(AcO)TPP + O=Re(OH)TPP
498 nm (CAcOH = 1.30
×
10–2–2.92 mol/L) (Fig. 3).
Ap – Ao
logꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀ
A∞ – Ap
The existence of isosbestic points in both series of
curves and the results of spectrophotometric titration
within the limits of each series, together with the
trends in the UV/Vis spectra with a decrease in the
AcOH concentration, show that the reaction of
[O=ReTPP]2O with AcOH proceeds in two reversible
steps. It has been experimentally shown that the sysꢀ
tem is equilibrated in about 5 min.
2
1
1
Ap − Ao
0
log
Analysis of the
versus logCAcOH plots
β
A∞ − Ap
α
(Fig. 4) allows us to determine the number of AcOH
molecules involved in equilibrium. At low AcOH conꢀ
tan
α
= 1
tanβ = 2
–1
–2
centrations (2.92
ichiometric ratio complex : acid = 1 : 1 (Fig. 4,
×
10–4–1.30
×
10–2 mol/L), the stoꢀ
1
(tan
1.0)
α
= 1.2)) and the equilibrium constant K1
= (5.4
×
102 were determined for the first equilibrium
stage. This allows us to write down the leftꢀhand side
of equilibrium (2). The rightꢀhand side is written with
taking into account the dynamics of UV/Vis spectra in
the course of titration and the data in [15] concerning
the stability of the μꢀoxo bridge:
–3
–2
–1
0
logCAcOH
Ap − Ao
A∞ − Ap
log
Fig. 4. Dependence
–log
C
for the reacꢀ
AcOH
[O=ReTPP]2O + AcOH
tion of [O=ReTPP] O with AcOH in benzene at (1) first
(2)
2
K1
←⎯⎯→
and (
2) second stages ( = 0.99).
ρ
O=Re(OH)TPP + O=Re(AcO)TPP.
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 58 No. 11 2013

THE STATE OF 5,10,15,20ꢀTETRAPHENYLꢀ21H,23HꢀPORPHINE RHENIUM(V)
1369
A
(а)
1
0
0.1
λ
, nm
(b)
300
400
500
600
A
0.1
0.5
0
λ
, nm
(c)
300
A
400
500
600
0.1
0.5
0
λ
, nm
300
400
500
600
Fig. 5. (a) UV/Vis spectra of [O=ReTPP] O in the benzene with additions of AcOH (solid lines) and obtained by decomposition
2
–6
–4
of experimental spectra into Gaussian peaks.
14.5 mol/L. 293 K.
= 8.3
×
10 mol/L;
C
: (a) 2.92
×
10 , (b) 0.29, and (c)
С
[O=ReTPP]2O
AcOH
––– [O=ReTPP] O;
–
⋅
–
⋅
–
O=Re(OH)TPP; –⋅ ⋅
–
⋅⋅ O=Re(AcO)TPP.
2
K2
The existence of equilibria (2) and (3) was conꢀ
firmed by NMR. According to the calculated relative
intensities, the H NMR spectrum of [O=ReTPP]2O
+ 2AcOH
O=Re(AcO)(AcOH)TPP (3)
←⎯⎯→
1
+ O=Re(AcO)(H2O)TPP.
in CDCl3 with addition of 0.38 mol/L of AcOH shows
the signals of the protons of the O=Re(OH)TPP and
O=Re(OAc)TPP compounds (see Experimental) in the
Thus, the direct reaction of equilibrium (3) yields a
heptacoordinated complex in which one coordination
site is occupied by an acyclic molecular ligand.
5 : 1 ratio. We assigned the signal with = –2.25 ppm to
δ
Figure 5 shows the UV/Vis spectra obtained by
decomposition of experimental spectra at different
reagent ratios into Gaussian peaks. These data point to
the existence of three species of the rhenium comꢀ
pound with H2TPP (molecular ligands are not shown)
in a wide range of solvent compositions: the dimeric
[O=ReTPP]2O species and two monomeric species,
O=Re(OH)TPP and O=Re(OAc)TPP. An increase in
the AcOH concentration (>12 mol/L) does not lead to
changes in the UV/Vis spectrum, which is almost
coincident with the spectrum of the rhenium(V) comꢀ
plex in 100% AcOH (Fig. 3).
the proton of the hydroxy ligand in the coordination
sphere of one of the compounds, O=Re(OH)TPP.
The upfield position of the signal of the coordinated
ОН– as compared with the signals of free H2O
(1.56 ppm) and C2H5OH (1.32 ppm) [16] is due to the
effect of the ring current of the porphyrin ring. For
example, the chemical shifts for the protons of this
kind are
⎯
2.54 and –9.4 ppm in the spectra of RuII(Tꢀ
and
[RuIV(OEP)(OH)]2O
nꢀPrP)(CO)(EtOH)
,
respectively [17]. The disappearance of the OH group
1
proton signals in the H NMR spectrum of the final
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 58 No. 11 2013

1370
TYULYAEVA et al.
690 nm. This spectrum differs from the spectrum of
A
the complex in glacial acetic acid (Fig. 6). Accordꢀ
ing to the data in [18], such electronic spectra are
characteristic of H+ꢀassociates of metalloporphyꢀ
rins Xn – 2MP…H+…R (R is an acid anion or an acid or
solvent molecule) formed in strong acids by complexes
with enhanced electron density in the macrocycle. At
standard temperature and on heating to 338 K, the
spectrum of the complex smoothly transforms, with
retention of isosbestic points, to the spectrum of the
H4TPP2+ dication with λmax = 437 and 650 nm. Howꢀ
ever, the spectrum of the dication of free porphyrin
shows an uncharacteristic absorption at 490 nm,
which builds up as the solution is kept at constant temꢀ
perature. The UV/vis spectrum of the products of conꢀ
version in sulfuric acid extracted into CHCl3 sows the
bands of free H2TPP and a monomeric rhenium(V)
compound analogous to the above O=Re(AcO)TPP
compound (Fig. 7).
On the basis of these data, we suggested the scheme
of reactions (4)–(7) for the conversion of the
[O=ReTPP]2O dimer in sulfuric acid. The scheme
contains slow (5) and fast (6) and (7) stages and it has
been confirmed by 1H NMR.
λ
, nm
450
550
650
Fig. 6. Evolution of the UV/Vis spectrum of
[O=ReTPP] O in 17.20 M H SO at 328 K. = 0–11000 s.
τ
2
2
4
[O=ReTPP]2O + 2H2SO4
product (Eq. (3)) (in CDCl3 + 6 M AcOH) indicates
the lack of the hydroxy ion in its inner coordination
sphere. At the same time, the presence of the proton
signals of the acetate ion (1.25 ppm) supports the
occurrence of reaction (3). In addition, comparative
analysis of 1H NMR spectra of solutions with different
AcOH concentrations demonstrates increasingly sigꢀ
nificant splitting of the signals of orthoꢀprotons closest
to the axial ligands with an increase in CAcOH. In
accord with Eq. (3), this can be due to the coordinaꢀ
tion of nonionized AcOH molecules as an additional
ligand. The shift of the coordination equilibrium to the
right is manifested as signal splitting increasing with
K1
O=Re(HSO )TPP
4
(4)
←⎯⎯→
−
+ O=Re(OH)TPP…H+…
O=Re(OH)TPP…H+…
HSO4,
−
HSO4
k2
+ H2SO4
H TPP
2
(5)
(6)
⎯⎯⎯→
−
+ O=Re(OH)2+
+
2HSO4,
−
H2TPP + 2H2SO4
O=Re(OH)2++ H2SO4
→
H4TPP2–
+
2HSO4,
→
O=Re(HSO4)2+ + H2O.(7)
By analogy with the previously studied reaction of
[O=ReTPP]2O with AcOH, the ꢀoxo dimer
CAcOH
.
µ
[O=ReTPP]2O in an H2SO4 medium decomposes into
O=Re(OH)TPP and O=Re(HSO4)TPP. However,
The UV/Vis spectrum of [O=ReTPP]2O dissolved
in 16.785–17.33 M aqueous sulfuric acid shows two
broad bands in the visible range at λmax = 538 and the O=Re(OH)TPP complex containing the πꢀelecꢀ
A
335
418
461
505
500
2
584
1
3 (A×3)
517
333
λ
, nm
Fig. 7. UV/Vis spectra of the products of the reaction of [O=ReTPP] O with 17.2 M H SO in CHCl (1) before and (2) after
3
2
2
4
separation by TLC on Silufol plates.
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 58 No. 11 2013

THE STATE OF 5,10,15,20ꢀTETRAPHENYLꢀ21H,23HꢀPORPHINE RHENIUM(V)
1371
tronꢀdonor hydroxo ligand forms with the solvent the
–logkeff
−
H+ꢀassociated species O=Re(OH)TPP…H+…
HSO4,
4
and the spectral transformation pattern corresponds to
the ionization of the macrocyclic ligand in this species
(Fig. 6). The O=Re(HSO4)TPP species stable in the
acid persists in the solution to the end of the transforꢀ
mation in the equilibrium concentration.
3
3.5
2
The 1H NMR spectrum of [O=ReTPP]2O in deuꢀ
terated sulfuric acid shows the signals of the protons of
the monomeric rhenium(V) complex (analogously to
the signals in the H NMR spectrum of a solution in
CD3COOD) and free H2TPP. In particular, the
1
4.0
1
α
, tanα = 3
observed signals with = 8.8, 8.5, and 7.78 ppm arise
δ
from the H , Hо, and Hm,p protons of the phenyl subꢀ
β
stituents in H2TPP (in CDCl3, the respective shifts are
8.77, 8.33, and 7.78 ppm). The singlet at 9.76 ppm, the
multiplet at 9.14 ppm, and the triplet at 8.2 ppm
attributed to the monomeric rhenium(V) complex are
not additionally split and are shifted downfield as
0.95
1.00
log[H2SO4]
Fig. 8. log
k
vs log[H SO ] for the reaction of
eff 2 4
[O=ReTPP] O in H SO at
T
(
1
) 308, (
) 338 K. The correlation coefficient
0.98, and 0.97, respectively.
2
) 318, (
3) 328,
is 0.99, 0.99,
2
2
4
and (
4
ρ
compared with the signals in the 1H NMR spectrum of
[O=ReTPP]2O in deuterated chloroform. Such a shift
−
is caused by the presence of the
ligand, which
HSO4
[O=Re(OH)TPP...H+...HSO4–]
decreases
cycle since the sulfur atom has energetically accessible
vacant orbitals.
π
ꢀelectron density at Re and in the macroꢀ
(10)
2
d
=
K1[[O=ReTPP]2O][H2SO4] /(1/2C0[OReTPP] O).
2
The kinetics of transformation by reactions (4)–(7)
can be adequately described by the quasiꢀequilibrium
method, and the experimentally derived kinetic equaꢀ
tion completely confirms the adequacy of a similar
transformation scheme. The result obtained is disꢀ
cussed below.
Since the decreases in the concentrations of the
reacting form of the complex and initial dimer are
equal to each other (Eq. (4)), the substitution of the
expression for this concentration into Eq. (9) leads to
the theoretical equation of reaction rate analogous to
the experimental one (Eq. (8)):
The effective parameters of the reaction of formally
the first order in [O=ReTPP]2O, found by leastꢀ
−dCO OH ReTPP…H …HSO dτ = −dC[OReTPP] O dτ
+
−
2
(
)
4
T
squares processing of the ln(C0
/
C
)–
τ
and
–1/T
logkeff
0
τ
=
k2K1[O=ReTPP] O]2(
)–1)[H2SO4]3 (11)
C[OReTPP] O
2
2
linear dependences, are presented in Table 1.
=
k
'[[O=ReTPP]2O][H2SO4]3.
The reaction rate linearly increases with an
increase in the equilibrium concentration of nonionꢀ
ized H2SO4 in concentrated sulfuric acid (Table 1, Fig. 8).
Table 2 presents the rate constants and activation
parameters of the reaction under consideration found
by processing the dependence in coordinates of Fig. 8.
As follows from comparison of experimental kinetic
equation (8) with the theoretical equation (Eq. (11)),
As follows from Fig. 8, the reaction order (
n) in
[H2SO4] is 3. Thus, the experimental kinetic equation is
−dC[OReTPP] O dτ = kC[OReTPP] O ⋅[H2SO4]3.
(8)
As follows from Table 1, the effective activation
2
2
the rate constant
k
contains several constants:
0
k
= 2k2K1
/
(12)
C
.
energy and entropy are almost independent on the
composition of a medium, like the dissociation reacꢀ
tions of other metalloporphyrins under the action of
acids [20].
[OReTPP]2O
Equation (12) enables the determination of the rate
constant of limiting stage (5) provided that the
[O=ReTPP]2O dissociation equilibrium in concenꢀ
trated sulfuric acid is quantifies as it has been
described above for the reaction with AcOH.
Experimental proof of the stability of the second
monomeric complex formed by reaction (4),
O=Re(HSO4)TPP, was provided by studying the
behavior of the complex in mixed solvents AcOH–
H2SO4. When H2SO4 is added in amounts from 5 to
The theoretical kinetic equation of rateꢀlimiting
stage (5) can be written as Eq. (9), in which
[
O(OH)ReTPP…H+…
−] can be described with
HSO4
taking into account equilibrium (4) and with the use of
the material balance equation (Eq. (10)).
−dCO OH ReTPP…H …HSO dτ
+
−
(
)
4
(9)
10 mol/L to an acetic acid solution of [O=ReTPP]2O
its UV/Vis spectrum smoothly changes in time with
,
+
−
⎡
⎣
⎤
[
⎦
= k2 O=Re(OH)TPP…H …HSO4 ⋅ H SO ,
]
2
4
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 58 No. 11 2013

1372
TYULYAEVA et al.
Table 1. Effective kinetic parameter of the reaction of [O=ReTPP]2O with H2SO4
0
ΔSe#ff
,
– J/(mol K)
% (mol/L) [H2SO4], mol/L
,
T
, K
keff
×
104, s–1
Eeff, kJ/mol
C
H2SO4
90.57 (16.785)
91.72 (17.05)
92.39 (17.20)
7.61
8.045
8.26
298a
318
328
338
298a
318
328
338
298a
308
318
328
338
298a
308
318
328
338
298a
308
318
328
338
0.27 0.01
0.74 0.05
1.15 0.05
1.82 0.08
0.41 0.04
1.20 0.07
1.90 0.08
3.11 0.14
0.51 0.06
0.79 0.07
1.41 0.05
2.15 0.11
3.45 0.24
0.60 0.05
0.86 0.08
1.59 0.24
2.33 0.16
3.80 0.31
0.69 0.04
0.94 0.08
1.84 0.19
2.75 0.21
4.20 0.29
40
42
40
2
2
3
205
195
201
7
5
7
8.41
8.84
9.29
9.49
9.59
9.61
9.83
10.03
10.22
10.30
9.93
92.70 (17.26)
92.97 (17.33)
39
38
4
1
203 12
10.14
10.33
10.51
10.59
10.31
10.51
10.69
10.86
10.92
203
5
a
Found by extrapolation of the log
k –1/T dependence.
eff
retention of isosbestic points (Fig. 9). The hypsochroꢀ absorption at 450 and 700–800 nm are observed. Such
mic shift, the decrease in the intensity of the bands
with λmax = 500 and 620 nm, and the growth of the
a pattern is typical of the reaction of formation of
chemically generated metalloporphyrins with the oneꢀ
electron oxidized macrocycle [21].
The spectra of the products of the reaction in chloꢀ
roform are analogous to those for the reaction of
[O=ReTPP]2O in aqueous sulfuric acid (Fig. 7) and
show the bands of H2TPP and a monomeric Re(V)
compound. H2TPP is formed in the course of dissociꢀ
ation of the O=Re(Ac)TPP complex and the Re(V)
compound, by oneꢀelectron oxidation of the
O=Re(HSO4)TPP complex with a stable coordination
center. In a solution in the mixed AcOH–H2SO4 solꢀ
vent, these species are at equilibrium with each other.
In presence of atmospheric oxygen, H2SO4 acts as a
oneꢀelectron oxidant of MP:
Table 2. Kinetic parameter of the reaction of [O=ReTPP]2O
with H2SO4
k
×
107,
mol–3 L3 s–1
– ,
S#
J/(mol K)
Δ
T
, K
E
, kJ/mol
37
308
318
328
338
298a
1
0.01
8
268 24
1.16 0.01
2.03 0.02
2.68 0.03
0.48
О=Re(HSO4)TPP + О2 + Н+
(13)
a
О=Re(HSO4)TPP+• + HO•2.
Found by extrapolation of the log
k –1/T dependence.
eff
→
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 58 No. 11 2013

THE STATE OF 5,10,15,20ꢀTETRAPHENYLꢀ21H,23HꢀPORPHINE RHENIUM(V)
1373
6. K. J. C. van Bommel, W. Verboom, H. Kooijman, et al.,
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zhong Luo Eur, J. Nucl. Med. Mol. Imaging 35, 734
(2008).
0.10
0.05
8. I. P. Beletskaya, V. S. Tyurin, A. Yu. Tsivadze, et al.,
Chem. Rev. 109, 1659 (2009).
9. T. N. Lomova, E. Yu. Tyulyaeva, and M. Yu. Tipugina, in
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lubchikov (NII khimii SPbGU, St. Petersburg, 2004),
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10. N. Carnieri and A. Harriman, Inorg. Chim. Acta 62
,
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400
500
600
700
λ, nm
Fig. 9. Evolution of the UV/Vis spectrum of
[O=ReTPP] O in a AcOH–6 M H SO at 298 K. = 0–
25000 s.
13. R. J. Gillespie and E. A. Robinson, in NonꢀAqueous
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τ
2
2
4
14. T. N. Lomova, in Progress in the Chemistry of Porphyꢀ
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St. Petersburg, 2001) vol. 3, p. 233 [in Russian].
Similar reactions have been well studied for many
metalloporphyrins by the authors of [22]. Quantitative
study of reaction (13) is hindered by the exotherm that
accompanies mixing of sulfuric acid with an acetic
acid solution of the complex. Dissolving the solid
[O=ReTPP]2O in a cooled AcOH–H2SO4 mixture
with different additions of the latter (5–10 mol/L)
does not lead to the formation of the oxidized form of
the Re(V) compound, presumably, because of a signifꢀ
icant energy barrier to this reaction.
15. P. A. Stuzhin, Doctoral Dissertation in Chemistry
(Ivanovo, 2004).
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(10), 2317 (1989).
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Translated by G. Kirakosyan
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RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 58 No. 11 2013