Hydroxyoxo(5,10,15,20-tetraphenylporphinato)tungsten(V) as a receptor for foodstuff and drug components. Thermodynamics of supramolecular complexation

Article abstract of DOI:10.1134/S0036023610050116

The thermodynamics of stepwise reactions of hydroxyoxo(5,10,15,20- tetraphenylporphinato)tungsten(V) (O=W(OH)TPP) with biologically active base molecules was studied. For the reaction of O=W(OH)TPP with benzimidazole, four steps were found and studied; the equilibrium constants K_n were determined to be 2.55 × 10⁴, 1.87 × 10³ L/mol, 1.06 × 10⁶, 4.09 × 10⁴ L²/mol ². The reaction of O=W(OH)TPP with pyrazine was a one-step reversible process of Pyz coordination to the eighth coordination site (K = 399 L/mol). The correlation equations relating the stability of supramolecular complexes to pK of the bases were obtained. The thermodynamic data were used to demonstrate the prospects of applying the metal porphyrin as a receptor for N-bases in membranes, sensors, and analytical devices for quality control of foodstuffs, drugs, and gas mixtures for the content of VOCs. Pleiades Publishing, Ltd., 2010.

Full text of DOI:10.1134/S0036023610050116

ISSN 0036ꢀ0236, Russian Journal of Inorganic Chemistry, 2010, Vol. 55, No. 5, pp. 727–733. © Pleiades Publishing, Ltd., 2010.
Original Russian Text © E.V. Motorina, T.N. Lomova, 2010, published in Zhurnal Neorganicheskoi Khimii, 2010, Vol. 55, No. 5, pp. 781–787.
COORDINATION COMPOUNDS
Hydroxyoxo(5,10,15,20ꢀtetraphenylporphinato)tungsten(V)
as a Receptor for Foodstuff and Drug Components.
Thermodynamics of Supramolecular Complexation
E. V. Motorina and T. N. Lomova
Institute of Solution Chemistry, Russian Academy of Sciences, Akademicheskaya 1, Ivanovo, 153045 Russia
Received November 17, 2008
Abstract—The thermodynamics of stepwise reactions of hydroxyoxo(5,10,15,20ꢀtetraphenylporphiꢀ
nato)tungsten(V) (O=W(OH)TPP) with biologically active base molecules was studied. For the reaction of
O=W(OH)TPP with benzimidazole, four steps were found and studied; the equilibrium constants Kn were
determined to be 2.55
O=W(OH)TPP with pyrazine was a oneꢀstep reversible process of Pyz coordination to the eighth coordinaꢀ
tion site ( = 399 L/mol). The correlation equations relating the stability of supramolecular complexes to pK
× × × ×
104, 1.87 103 L/mol, 1.06 106, 4.09 104 L2/mol2. The reaction of
K
of the bases were obtained. The thermodynamic data were used to demonstrate the prospects of applying the
metal porphyrin as a receptor for Nꢀbases in membranes, sensors, and analytical devices for quality control
of foodstuffs, drugs, and gas mixtures for the content of VOCs.
DOI: 10.1134/S0036023610050116
Currently, coordination and ligand replacement (BzIm) and pyrazine (Pyz), i.e., heterocycles forming
reactions involving porphyrin complexes of highly the basis for many drugs and aromatic compounds in
charged metal cations (Х)n – 2MP (X is an acid residue, fried meat, potatoes, cocoa, coffee, and some sorts of
P is the 5,10,15,20ꢀtetraphenylporphine dianion,
n
=
cheese [14].
3 or more) are of considerable interest for the coordiꢀ
nation and applied chemistry. Being complexes with
mixed coordination sphere, they are distinguished by
diversity of possible coordination polyhedra, they have
a high effective charge on the central atom and vacanꢀ
cies in the first coordination sphere and thus remain
coordinatively unsaturated [1–5]. The formation of
supramolecular complexes with molecules of bases is
the most typical reaction of (Х)n – 2MP functioning in
different physical states in natural objects, engineering
devices, and molecular machines [6–10]. Studies of
the quantitative characteristics and the stoichiometry
of the molecular complexation reactions in solutions
provide conditions for targeted search for receptors for
biologically active bases and transporting agents for
small molecules or ions to be used as sensors and anaꢀ
lytical reagents in quality control and environmental
monitoring.
EXPERIMENTAL
Hydroxyoxo(5,10,15,20ꢀtetraphenylporphinato)
tungsten(V) O=W(OH)TPP. The complex was preꢀ
pared by a reported procedure [15]: 5,10,15,20ꢀtetꢀ
raphenylporphin (H2TPP) (0.1 g, 0.16 mmol) was
refluxed with WCl6 (0.2 g, 0.53 mmol) in phenol
(0.8 g) at a temperature of 454 K for 4 h. The synthesis
was terminated when the UV/Vis spectrum of a samꢀ
ple from the reaction mixture in chloroform no longer
contained bands for H2TPP (λmax, nm: 648.0, 592.0,
551.0, 516.0, 485.0, 420.0). The complex was isolated
in the solid state by vacuum evaporation of phenol,
dissolved in CHCl3, and applied onto a column with
Al2O3. Chromatographic purification using CHCl3
was repeated twice. The yield of the complex was 60%.
UV/Vis (chloroform, λmax, nm
585.0 (3.11), 449.0 (4.25). IR (400–1700 cm–1, KBr),
, cm–1: benzene ring vibrations 708, 758 (
(C–H));
1075, 1180 ( (C–H)); 1485, 1610 ( (C=C)); pyrrole ring
vibrations 805 ( (C–H)); 1020 ((C3–C4), (C–N),
(C–H)); 1335 ( (C–N)); 1445 ( (C=N)); 1540
( logε )): 621.0 (2.85),
Previously [11–13], data on the thermodynamics
and kinetics of reactions of hydroxyoxo(5,10,15,20ꢀ
tetraphenylporphinato)tungsten(V) (O=W(OH)TPP)
with organic bases, imidazole (Im) and pyridine (Py),
and with hydrogen sulfide in toluene were reported. In
view of the results of these studies, the tungsten comꢀ
plex was used as the membrane activating agent for gas
separation and as a component of selective velocityꢀ
type sensor for H2S [11]. The present communication
ν
γ
δ
ν
γ
ν
δ
ν
ν
(skeletal vibrations of the pyrrole ring); W–N, 447;
W–O, 630; W=O, 940.
Thermodynamics
of
the
reactions
of
reports a quantitative investigation of the equilibrium O=W(OH)TPP with Pyz and BzIm was studied by
in reactions of O=W(OH)TPP with benzimidazole spectrophotometric
727
titration.
Solutions
of

728
MOTORINA, LOMOVA
Table 1. Calculation data of thermodynamic parameters for the reaction of O=W(OH)TPP with Pyz, the reliability of approximation
(ρ) is 0.95
–1
T
, K
1/T
×
10–3, K
K
, mol–1
L
–ln
K
Δ
H0
,
kJ/mol
19
Δ
S0
,
J/mol K
113
298
303
313
318
343
353
3.356
3.3
399
474
5.99
6.16
6.20
6.26
7.08
7.11
3.195
3.145
2.915
2.833
493
524
1182
1217
O=W(OH)TPP, BzIm, and Pyz in freshly distilled toluꢀ
The UV/Vis spectra of solutions were recorded on
ene were prepared immediately before use to avoid the Agilent 8453 UV/Vis and Specord M40 spectrophoꢀ
formation of peroxides in the solvent and their reacꢀ tometers; the absorbance at the working wavelength
tions with the complex. The absorbances for a series of was measured on an SFꢀ26 spectrophotometer, and
solutions with the constant concentration cO=W(OH)TPP the IR spectrum was recorded on an Avatar 360 FTꢀIR
4.0
× ×
10–6 mol/L for BzIm and 4.8 10⎯6 mol/L for ESP spectrometer.
Pyz, and different concentrations of the base were
measured at working wavelengths of 452 and 446 nm
for reactions with BzIm and Pyz, respectively. The
equilibria were studied over broad ranges of base conꢀ
RESULTS AND DISCUSSION
According to published data [16], in the complexes
O=M(OH)TPP, the oxo and hydroxy ligands О2– and
ОН– occur in trans positions relative to the macrocyꢀ
cle plane. The results of investigations of the stability
of the coordination sphere [15] attests to weaker bindꢀ
ing of these ligands to tungsten as compared with the
macrocyclic porphyrin dianion, which is not ionized
even in hot sulfuric acid or in superacids. These propꢀ
erties can be clearly seen in the reactions of
O=W(OH)TPP with bases; However, as can be seen
from the subsequent discussion, these reactions occur
only with excess of a base as ligand displacement proꢀ
cesses along with additional coordination processes.
centrations:
×
c
×
BzIm = 7.5
× × cPyz = 2.23
10–6–6.9 10–3,
10–4–8.91
10–3 mol/L. The solutions were mainꢀ
tained at constant temperature in closed optical cells
in a special compartment of the spectrophotometer.
The temperature was maintained to within 0.1 K.
The equilibrium constants of the reactions were
determined from relation (1) derived using the mass
action law and the Bouguer–Lambert–Beer law; the
latter was applied to mixtures of two colored comꢀ
pounds: the tungsten complex and the molecular comꢀ
plex of metal porphyrin (MP) with the base.
Аe − Ао
Figure
1
shows the UV/Vis spectra of
А∞ − Ао
Аe − Ао
1
,
(1)
K =
n
O=W(OH)TPP in toluene with different added
amounts of BzIm in the Soret band region. The specꢀ
trum of O=W(OH)TPP in pure toluene (Fig. 1, curve
1) is a line with a maximum at 453 nm. During the
spectrophotometric titration, the absorption intensity
at the maximum increases at base concentrations of
⎛
⎞
Аe − Ао
cL − cMо P
1 −
⎜
⎟
А∞ − Ао
А − А
⎝
⎠
∞
о
о
where
,
and cL are the initial concentrations of MP
and the base in the solution in toluene, respectively;
Ао Аe and А∞ are the absorbances at the working
wavelength for solutions of MP, equilibrium mixture at
a particular ligand concentration, and the reaction
cMP
10–6–1.25
×
10–4 mol/L (Fig. 2, curve
10–4–7.15 10–4 mol/L
1), then
,
,
7.5
decreases for cBzIm 1.25
(curve ), and again first increases and then decreases
in the BzIm concentration ranges of 7.15
10–4–2.49
10–3 and 2.49 10–3–6.90 10–3 mol/L, respectively
(curves and ). The form of the absorption curve
×
×
×
2
product;
modynamic characteristics of the reactions of
O=W(OH)TPP with bases,
H0 and S0, were deterꢀ
mined from the temperature dependence of (2). The
n is the number of attached ligands. The therꢀ
×
×
×
4
×
Δ
Δ
3
K
markedly changes: at intermediate concentrations of
BzIm, the band becomes asymmetric, and both secꢀ
tions of increasing intensity exhibit a minor (less than
1 nm) bathochromic shift of the absorption maximum.
The absorption maximum (at 455 nm) recorded at the
greatest amount of the base added is located most
bathochromically. At higher BzIm concentrations
mathematical processing of the linear dependences
was carried out using the leastꢀsquares method and
Microsoft Excel software. The relative error in deterꢀ
K did not exceed 10%. An example of calꢀ
culation of thermodynamic parameters is presented in
Table 1.
mination of
(above 7 ×
10–3 mol/L), the reaction cannot be studied
ΔH0 1 ΔS0
due to insufficient solubility of the base. The construcꢀ
tion of the spectrophotometric titration curves (Fig. 2)
–lnK = ꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀ – ꢀꢀꢀꢀꢀꢀꢀ.
(2)
R T
R
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 55 No. 5 2010

HYDROXYOXO(5,10,15,20ꢀTETRAPHENYLPORPHINATO)TUNGSTEN
729
the equilibrium constant K1 equals 2.55
×
104 L/mol.
A
The fourth positive order of magnitude of the conꢀ
stant, the increase in the intensity, and the noticeable
bathochromic shift of the absorption maximum in the
UV/Vis spectra of O=W(OH)TPP attest to some
counterbalancing of the positive charge on the W atom
in metal porphyrin, which is possible only upon coorꢀ
dination of one BzIm molecule (the stoichiometry of
the first step is 1 : 1 (Fig. 3)) to the eighth coordination
site (equation (3)). It is known that the formation of
tungsten(V) complexes with CN 8 is more probable
than the formation of heptacoordinated complexes
[17]. According to a critical database sampling of ten
thousand compounds with structures known from Xꢀ
ray diffraction analysis, the distribution of tungsten(V)
complexes with CN 5, 6, 7, and 8 is as follows: 2, 12,
0, and 1. The probability of existence of octacoordiꢀ
nated complexes was reported [17] to increase for
tungsten(IV) where this distribution is 6, 31, 1, and 8.
However, for porphyrin complexes, “catastrophic”
changes in the UV/Vis spectra are known to occur
on reduction of tungsten(V) to tungsten(IV) where
the hyper type spectrum switches to a hypso type
spectrum [18].
2
4
5
3
1
0.3
0.2
0.1
400
420
440
460
480
, nm
λ
Fig. 1. UV/Vis spectrum of O=W(OH)TPP at about the
Soret band in toluene vs. concentration of BzIm.
–6
c
= 4.0
×
10 mol/l,
–4
c
, mol/L: (1) 0, (2)
O=W(OH)TPP
–5
BzIm
–3
–3
7.5 × 10 , (3) 7.15 × 10 , (4) 2.49 × 10 , (5) 6.9 × 10 .
indicates that the reaction of O=W(OH)TPP with
BzIm has four steps. All of these are equilibrium proꢀ
cesses, which is confirmed experimentally by recordꢀ
ing the UV/Vis spectra on dilution the reaction mixꢀ
tures with respect to the base.
For BzIm concentrations of 7.5
× ×
10–6–1.25
O=W(OH)TPP + BzIm
10⎯4 mol/L, one base molecule participates in the first
equilibrium step of the reaction (Fig. 3, tanα1 = 1.09),
(3)
K1
←⎯→O=W(OH)(BzIm)TPP.
A
0.30
1
A
0.30
2
0.25
0.25
0
0.5
cL
1.0
0
2
4
6
104, mol/L
×
104, mol/L
cL
×
A
A
0.30
3
0.30
4
0.25
0.25
2
4
×
6
1.0
1.5
2.0
cL
103, mol/L
cL
×
103, mol/L
–6
Fig. 2. Curves of spectrophotometric titration of O=W(OH)TPP with benzimidazole in toluene.
c
, mol/L: (
1)
7.5
× 10 –
BzIm
–3
–4
–4
–4
–4
–3
–3
1.25
452 nm.
× 10 , (2) 1.25 × 10 –7.15 × 10 , (3) 7.15 × 10 –2.49 × 10 , (4) 2.49 × 10 –6.90 × 10 . The working wavelength is
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 55 No. 5 2010

730
MOTORINA, LOMOVA
nar and induces a bathochromic shift (instead of the
expected hypsochromic shift) of the band in the
UV/Vis spectrum to 455 nm.
Ae
A∞
–
–
Aо
Ae
log
The equilibrium constant К4 for the fourth step is
4.09
0.5
×
105 L2/mol2; the reaction involves two moleꢀ
cules of the base (Fig. 3, tanα4 = 1.96). Since in the
complex formed by reaction (5), the CN has reached
the maximum, the trimolecular reaction occurring in
the final step should be ascribed to another reaction
site. Owing to the conjugation system in the base molꢀ
0
–0.5
–1.0
–5.5
–4.5
–3.5
–2.5 logcL
3
ecule, the
πꢀsystem of the coordinated porphyrin
2
1
macrocycle can serve as such reaction site. Probably,
this is the case where the spectrophotometric titration
method is sensitive to the intermolecular π–π interacꢀ
4
tion. This type of result was obtained for the first time
for the reaction of (Cl)InTPP with pyridine [19] for
which the equilibrium constant was much lower
(4.1 L2 mol–2) but
n
was still equal to two.
The reaction of O=W(OH)TPP with Pyz, which is
a weaker base than BzIm ( КL are 0.65 and 5.53,
A −A
e
o
log
Fig. 3. Dependence
– logcL for the reaction of
A∞ −A
e
O=W(OH)TPP with BzIm in toluene in the (
second, ( ) third, and ( ) fourth steps ( = 0.95, 0.97, 0.96,
0.96, respectively).
1
) first, (2)
р
3
4
ρ
respectively [14, 20]), is a oneꢀstep process. The
UV/Vis spectrum of O=W(OH)TPP in toluene does not
undergo shifts of absorption bands in the 350–750 nm
The 1 : 1 molecular ratio is also retained for the secꢀ range upon titration with pyrazine. However, the
ond step of the reaction of O=W(OH)TPP with BzIm absorption intensity at the maximum of the 445.4 nm
(Fig. 3, tanα2 = 1.3). The numerical value of the conꢀ band first slightly increases and than decreases more
stant K2
probably imples that coordination of the base moleꢀ icant (for cO=W(OH)TPP
cule requires the displacement of ОН– from the coorꢀ density at 445.4 nm changes by 0.027), which preꢀ
(1.87 ×
103 l/mol) is smaller than К1, which
rapidly. The initial increase in the intensity is insignifꢀ
=
4.8
×
10–6 mol/L, the optical
dination sphere (equation (4)).
cludes spectrophotometric titration. Apparently, this
change in the UV/Vis spectrum is caused by the hyperꢀ
chromic effect of passing from pure toluene to a toluꢀ
ene mixture with Pyz. The equilibrium can be studied
O=W(OH)(BzIm)TPP + BzIm
(4)
+
−
K 2
←⎯→[O=W(BzIm)2TPP] ⋅ OH .
quantitatively at Pyz concentrations of 2.23
8.91
10–3 mol/L (Fig. 4) above which the spectrum
remains invariable. The equilibrium constant of the
only step of the reaction with Pyz is 3.99
102 L/mol,
the number of the reacting Pyz molecules is 1 (Fig. 4b,
tan = 0.91). The value is approximately two orders
×
10–4–
The displacement of the ligand with an integer negꢀ
ative charge to the second coordination sphere results,
as expected, in opposite changes in the charge of the W
atom and the intensity of the band in the UV/Vis specꢀ
tra (Fig. 1).
×
×
α
K
The third step of the reaction of O=W(OH)TPP
of magnitude lower for the reaction with Pyz than for
the reaction with BzIm. In view of the 1 : 1 stoichioꢀ
metry and low basicity of Pyz, the reaction can be
regarded as coordination of a Pyz molecule to the
eighth coordination site (equation (6)).
with BzIm occurs at BzIm concentration of 7.15
2.49
10–3 mol/L. The equilibrium constant К3
1.06
106 L2/mol2 refers to the complex with the stoꢀ
×
10–4–
×
×
=
ichiometric ratio O=W(OH)TPP : BzIm = 1 : 2 (Fig. 3,
tanα3 = 2.3). The sharp growth of the equilibrium
constant by almost three orders of magnitude may be
attributed to the fact that this is, in essence, the overall
constant for two equilibria, namely, coordination of
one BzIm molecule as a result of cleavage of one bond
with the oxo group and replacement of the oxygen
ligand by the second base molecule (equation (5)).
O=W(OH)TPP + Pyz
(6)
K1
←⎯→O=W(OH)(Pyz)TPP.
Thus, the reaction of O=W(OH)TPP with Pyz,
which is less basic than BzIm, does not affect the
bonds of MP with the OH– and O2– ligands. In addiꢀ
tion, this reaction is endothermic (Table 2), unlike the
similar step of the reaction with BzIm.
Generally, the thermodynamic parameters of the
stepwise reactions of O=W(OH)TPP with the bases
[O=W(BzIm)2TPP]+ ⋅ OH− + 2BzIm
(5)
−
3+
−
K3
←⎯→[W(BzIm)3(BzIm )TPP] ⋅ (OH )2.
The displacement of the oxo group from the first (Fig. 5, Table 2) are consistent with the transformaꢀ
coordination sphere in the third step of the reaction to tions proposed above. The reaction of O=W(OH)TPP
give a complex with symmetrical coordination sphere with Pyz is endothermic with positive Δ
S0. For reacꢀ
evidently makes the coordination unit WN4 more plaꢀ tion (6) in the gas phase, one could expect a negative
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 55 No. 5 2010

HYDROXYOXO(5,10,15,20ꢀTETRAPHENYLPORPHINATO)TUNGSTEN
731
Ae
A∞
–
–
Aо
Ae
(а)
(b)
log
A
0.4
0.6
0
–0.4
–0.8
–4.0 –3.5
–3.0
–2.5 logcL
0.5
0.4
0
2
4
6
8
cL ×
103, mol/L
–4
–3
Fig. 4. (a) Curve of spectrophotometric titration of O=W(OH)TPP with pyrazine in toluene (
c
= 2.23 × 10 –8.91 × 10 )
Pyz
Ae − Ao
log
and (b) corresponding dependence
–logcL for the second step (ρ = 0.993). The working wavelength is 446 nm.
A∞ − Ae
Δ
S0. In solution, the desolvation of two reactants cules, [O=W(L)2TPP]+ · OH–, is more stable in the
results in the increase in the entropy of molecular case of Py (Table 3). On going from the first step of the
complexation. The latter is also valid for the two first supramolecular formation reaction to the second step,
steps of the reaction with BzIm. The reactions of the electrophilic attack of the reagent L switches to the
O=W(OH)TPP with the stronger base, BzIm, are exoꢀ nucleophilic attack (the replacement of OH–), which
thermic in the first and second steps (Table 2). The is reflected as the change of the sign of the coefficient
third and fourth steps are endothermic and characterꢀ at
ized by large positive entropy changes. The endotherꢀ
mic character of the third step (equation (5)) and the
pKL (equation (8)).
In three of the five cases (Py, H2S, and BzIm comꢀ
plexes), the formation of supramolecules during the
reaction is accompanied by a bathochromic shift of the
maximum of the Soret band. For BzIm, this shift is
hardly visible (Table 3). The specific nature of comꢀ
plexes with Py and H2S is manifested not only in the
change in the UV/Vis spectrum but also in better comꢀ
patibility of two Py in [O=W(L)2TPP]+ · OH– as comꢀ
pared with Im or BzIm (containing additional
N atoms) and also in the fact that in the reaction with
H2S, the OH– anion is replaced by another anion
sharp increase in the positive Δ
S0 point respectively to
the occurrence of energyꢀconsuming cleavage of the
W=O double bond in the reacting molecule
[O=W(BzIm)2TPP]+ · OH– and to desolvation of the
three initial species. In the fourth energyꢀconsuming
step, the entropy again increases (three solvated speꢀ
cies react to give one species), leaving Δ
S0 to be still a
positive although a lower value (Table 2).
Using the above and previously reported [6] data
(Table 3), correlations (Fig. 6) and correlation equaꢀ
tions (7) and (8), which relate the stability of comꢀ
plexes to protonation constants of bases, were derived
for supramolecular complexation reactions of
O=W(OH)TPP.
(
SH–) rather than by the H2S molecule.
Thus, in solutions, O=W(OH)TPP reversibly
forms supramolecular complexes with bases (see reacꢀ
tions (3)–(6)), their stepwise equilibrium constants
are highly sensitive to the nature of the base (equations
(7) and (8)). Their values for nitrogenꢀcontaining
molecules differ from unity by several orders of magniꢀ
tude. A noticeable optical response at about the Soret
pK
1 = –0.4039 p
K
L – 2.2522,
L – 7.0379.
(7)
(8)
p
K
2 = +0.6339 p
K
For the complex with H2S, the first and the second
steps of the reaction include replacement of the OH–
ligand by SH– and coordination of the second SH–
group through cleavage of one of the two bonds in
W=O. For other bases, coordination of one molecular
ligand and replacement of OH– by the molecular
ligand take place. Therefore, correlations (7) and (8)
cover the bases presented in Table 3 except for H2S and
Pyz. It follows from equation (7) that the higher the
basicity of L molecule, the more stable the complex
O=W(OH)(L)TPP; this implies the absence of a conꢀ
Table 2. Thermodynamic parameters ΔH0 and ΔS0 for the
reactions of O=W(OH)TPP with BzIm and Pyz
BzIm
Pyz
Step
0
0
0
0
Δ
H
,
Δ
S
,
Δ
H
,
ΔS ,
kJ/mol
J/mol K
kJ/mol
J/mol K
1
2
3
4
–6.8
–4.3
4.0
58.2
47.9
129
19
113
tribution of the
πꢀorbitals of the bases to the stability.
7.4
113
The supramolecular complex with two base moleꢀ
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 55 No. 5 2010

732
–ln
MOTORINA, LOMOVA
K
pK
–2.5
–5
5
2
2
–3.0
1
–3.5
–4.0
–4.5
–5.0
1
4
–10
3
0
2
4
6
pKL
–15
Fig. 6. Stability constants of supramolecular complexes:
+
(1) O=W(OH)(L)TPP (ρ = 0.97), (2) [O=W(L) TPP] ·
1 2
–
OH (
ρ = 0.84) pK vs. protonation constants of bases pK .
2
L
T
)
×
10–3, K–1
2.6
2.8
3.0
3.2
(1/
Fig. 5. –ln
K
vs. 1/
T
for the reaction of O=W(OH)TPP
) first, ( ) second, ( ) third, and (
= 0.96, 0.96, 0.92, and 0.90, respectively)
) with Pyz ( = 0.95) in toluene.
been noted, above a critical concentration of the base,
the UV/Vis spectra of metal porphyrin–base mixtures
become invariable but the spectra are not identical for
different bases (Table 3 [6]) and can be used for idenꢀ
tification. These features of O=W(OH)TPP, together
with the response time and the circulation time (the
time required for establishing the equilibrium of the
reaction with the base and return to the initial state
upon dilution) equal to several seconds, and superstaꢀ
bility of W–N coordination bonds make it possible to
use metal porphyrin as the Nꢀbase receptor in memꢀ
with BzIm in the (
fourth steps (
and (
1
2
3
4)
ρ
5
ρ
band is observed for base concentrations from 10–6–
10–4 to 10–3–10 mol/L (the data of this work and
reported work [6]). For example, for BzIm present in
concentrations of 7.5
relative optical response is 0.47 fractions, which is not
inferior to the values reported [7] for film sensors
× ×
10–6–1.25 10–4 mol/L, the
based on zinc(II) phthalocyanines. As has already branes, sensors, and analytical devices for quality conꢀ
Table 3. Physicochemical parameters of the formation of supramolecular complexes of O=W(OH)TPP (m is the number of steps, Δλmax
is the overall bathochromic shift of the Soret band with respect to pure toluene, K1, K2) and pKL of molecular ligands [14, 20–22]
K1
L/mol
×
102,
K2 ×
102,
L/mol
Molecular ligand
m
Δλmax
рK , (25°C)
L
Im*
BzIm
2
4
3
2
2
0.8
2.0
2055
254
133
–
7.47
18.7
84
7.03
5.53
5.23
0.65
7.1
Py*
12.0
0
Pyz
3.99
1.0
H2S*
12.5
1.76
* Published data [6].
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 55 No. 5 2010

HYDROXYOXO(5,10,15,20ꢀTETRAPHENYLPORPHINATO)TUNGSTEN
733
8. G. Ciccerella, J. Spadavecchia, R. Rella, et al., Biosenꢀ
sors Bioelectronics B 22, 412 (2007).
9. C. Bariain, I. R. Matias, C. FernandezꢀValdivielso,
trol of foodstuffs, drugs, and gas mixtures for the conꢀ
tent of VOCs.
et al., Sen. Actuators B 93, 153.
10. E. N. Ushakov, M. V. Alfimov, and S. P. Gromov, Usp.
ACKNOWLEDGMENTS
Khim. 77 (1), 38 (2008).
This work was partially supported by basic research
program no. 8 of the Presidium of the RAS, by the
Russian Foundation for Basic Research project
no. 06ꢀ03ꢀ96343, and by the Analytical Departmental
Target Program “Development of the Higher School
Scientific Potential Project no. RNP 2.2.1.1.7181.”
11. O. A. Golubchikov, T. N. Lomova, and M. Yu. Tipuꢀ
gina, Abstracts of Papers, AllꢀUnion Symposium
“Bioengineering and Chemical Methods of Environmenꢀ
tal Protection, Samarkand, 1988, p. 112.
12. M. Yu. Tipugina and T. N. Lomova, Zh. Neorg. Khim.
49 (8), 1285 (2004) [Russ. J. Inorg. Chem. 49 (8), 1180
(2004)].
13. M. Yu. Tipugina, Candidate’s Dissertation in Chemisꢀ
try (IKhR RAN, Ivanovo, 2000).
14. General Organic Chemistry, Ed. by P. G. Samms
(Khimiya, Moscow, 1981).
15. T. N. Lomova, N. I. Volkova, and B. D. Berezin, Zh.
Neorg. Khim. 30 (3), 626 (1985).
16. W. R. Scheidt, The Porphyrins, Ed. by D. N. Y. Dolphin
REFERENCES
1. M. Yu. Tipugina, E. V. Motorina, and T. N. Lomova,
Zh. Neorg. Khim. 52 (3), 444 (2007) [Russ. J. Inorg.
Chem. 52 (3), 394 (2007)].
2. M. Yu. Tipugina, E. V. Motorina, and T. N. Lomova,
Zh. Fiz. Khim. 79, Suppl. 1, 39 (2005) [Russ. J. Phys.
Chem. 79, Suppl. 1, 39 (2005)].
(Academic, San Francisco, London, 1978), p. 463.
3. M. Yu. Tipugina and T. N. Lomova, Zh. Neorg. Khim.
49 (8), 1285 (2004) [Russ. J. Inorg. Chem. 49 (8), 1180
(2004)].
17. Solov’ev V P., M. S. Stuklova, E. V. Kotlunova, and
N. N. Kochanova, Koord. Khim., 29 (9), 711 (2003)
[Russ. J. Coord. Chem. 29 (9), 660 (2003)].
4. T. N. Lomova, E. V. Motorina, E. Yu. Tyulyaeva, et al.,
Advances in Porphyrin Chemistry, Ed. by O. A. Golubꢀ
chikov (NII khimii SPbGU, St. Petersburg, 2007),
Vol. 5 [in Russian].
18. T. N. Lomova and B. D. Berezin, Koord. Khim. 27 (2),
96 (2001) [Russ. J. Coord. Chem. 27 (2), 85 (2001)].
19. T. N. Lomova, M. E. Malov, and M. V. Klyuev, Zh. Fiz.
Khim. 83 (6), 1046 (2009) [Russ. J. Phys. Chem. 83 (6)
(2009)].
20. Khimicheskaya entsiklopediya, Ed. by I. L. Knunyants
(Sovetskaya Entsiklopediya, Moscow, 1980), vol. 1 [in
Russian].
5. E. V. Motorina and T. N. Lomova, Abstracts of Papers,
XXIX Scientific Session of the Russian Seminar on the
Chemistry of Porphyrins and Their Analogues, Ivanovo,
2006, p. 80 [in Russian].
6. T. N. Lomova, E. V. Motorina, E. N. Ovchenkova, and
M. E. Klyueva, Izv. Ross. Akad. Nauk, Ser. Khim.,
No. 4, 636 (2007).
21. Khimicheskaya entsiklopediya, Ed. by I. L. Knunyants
(Sovetskaya Entsiklopediya, Moscow, 1980), vol. 2 [in
Russian].
7. J. Spadavecchia, G. Ciccerella, and R. Rella, Sen. 22. R. Bell, Proton in Chemistry (Chapman and Hall, Lonꢀ
Actuators B 106, 212 (2005). don, 1973; Mir, Moscow, 1977).
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 55 No. 5 2010