Quantitative study of the quasiequilibrium in the system (hydroxo)oxo-(5,10,15,20-tetraphenylporphynato)-molybdenum(V)-piperidine in toluene medium

Article abstract of DOI:10.1134/S1070363213070220

The quasiequilibrium interaction of (hydroxo)oxo-(5,10,15,20- tetraphenylporphynato)molybdenum(V) and piperidine in the toluene medium has been studied by means of chemical kinetics and spectrophotometric titration. It has been revealed that the molecular

Full text of DOI:10.1134/S1070363213070220

ISSN 1070-3632, Russian Journal of General Chemistry, 2013, Vol. 83, No. 7, pp. 1435–1443. © Pleiades Publishing, Ltd., 2013.
Original Russian Text © E.V. Motorina, T.N. Lomova, 2013, published in Zhurnal Obshchei Khimii, 2013, Vol. 83, No. 7, pp. 1187–1196.
Quantitative Study of the Quasiequilibrium
in the System (Hydroxo)oxo-(5,10,15,20-tetraphenylporphynato)-
molybdenum(V)–Piperidine in Toluene Medium
E. V. Motorina and T. N. Lomova
Krestov Institute of Solution Chemistry, ul. Akademicheskaya 1, Ivanovo, 153045 Russia
e-mail: tnl@isc-ras.ru
Received June 28, 2012
Abstract—The quasiequilibrium interaction of (hydroxo)oxo-(5,10,15,20-tetraphenylporphynato)molybdenum(V)
and piperidine in the toluene medium has been studied by means of chemical kinetics and spectrophotometric
titration. It has been revealed that the molecular complex formation proceeds as slow irreversible salt formation
-
reaction. It is preceded by the stages of equilibrium substitution of the hydroxo group OH with piperidine, the
3
–1
outer sphere cationic complex formation [K (2.03±0.28)×10 M ]; and by the coordination of the second
1
–1
piperidine molecule to the cationic complex (K 1.76±0.39 M ). The complex formation has been completely
2
kinetically described: the rate equations and rate constants have been derived, and the rate limiting stage has
been identified. In addition, the physicochemical data on the intermediates and products are presented. The
prospects of application of the mixed porphyrin-containing complex as piperidine receptor,alkaloids and
pharmaceuticals building block, have been justified.
DOI: 10.1134/S1070363213070220
The steady interest to the molybdenum complexes
is mostly due to their functions in biological systems.
For example, some enzymes (nitrogenases, oxydases,
or hydrogenases of varied nature [1]) contain metal
atoms in the active sites. In its coordination com-
pounds, molybdenum can exist in the oxidation states
of 0 to +6, and can possess a coordination number of 4
to 8 [2]. The comparative analysis of molybdenum
complexes behavior in typical chemical reactions was
made in [3]. The equilibrium constants of the reaction
of molybdenum oxocomplexes with ethylenediamine-
tetraacetate were determined in [4, 5] by means of
potentiometric titration and temperature jump methods;
the obtained values were consistent with other
available data [6]. The coordination of porphyrin dianion
to molybdenum and Mo-porphyrin reactions with
organic bases were investigated using the model
systems containing (hydroxo)oxo-(5,10,15,20-tetra-
phenylporphynato)molybdenum(V) O=Mo(OH)TPP
and nitrogen bases (imidazole [7] or pyridine Py [8]),
and other analytical devices. Still, metalloporphyrins
reactions with piperidine Pip base, which is a building
block of many pharmaceuticals (analgesics, anes-
thetics) and natural alkaloids (piperine, lobeline, mor-
phine), have been poorly studied. For the molybdenum
complexes such data is absent, to the best of our
knowledge. In [10–12] the reactivity of tetraphenyl-
porphyrin complexes with cobalt, manganese, and zinc
towards piperidine coordination was studied. In the
case of cobalt, in the ethanol medium the reaction
resulted in the 1:1 (Pip)CoTPP complex. Zn-porphyrin
formed the same 1:1 donor-acceptor complex, as well
as the (Pip) ZnTPP molecular complex in the benzene
2
or CCl medium. The manganese(III) complex was
4
capable of complexing piperidine in the toluene
medium, simultaneously being reduced to manganese(II)
[12]. Even though the above-cited studies were
performed in different media, it followed from their
results that the piperidine coordination process was
strongly dependent on the nature of metal contained in
the metalloporphyrin.
or sulfur-containing ligand H S [9]. In that works it
2
was demonstrated that the molybdenum complex was
capable of reversible coordination of the bases; this
property could be applied for construction of sensors
In this work the equilibrium states and rates of
elementary reactions comprising the O=Mo(OH)TPP
1
435

1
436
MOTORINA, LOMOVA
А
(a)
4
46 nm
А
А
(
461
463
(
3
с×10 , M
λ, nm
λ, nm
(
b)
Fig. 1. Electron absorption spectra of O=Mo(OH)TPP in
А
toluene medium in the presence of various piperidine
–
6
amounts. [O=Mo(OH)TPP] = 8.77×10 M; [Pip] = (1) 0,
А
–
2
(
2) 1.62×10 M, and (3) 8.43 M; λ, nm: (1) 463, (2) 461,
and (3) 446.
complex evolution in presence of piperidine in the
toluene medium were studied, and the composition and
spectral properties of the stepwise donor-acceptor
complex formation were evaluated. Finally, prospects
of application of the Mo-porphyrin complex as
piperidine receptor were discussed.
L
с , M
Electron absorption spectra (in the range of Soret
absorption band) of O=Mo(OH)TPP in the toluene
medium upon addition of various amounts of pipe-
ridine are shown in Fig. 1. The spectral changes ob-
served allowed to distinguish two stages of the reaction
and to collect the data for the titration curves (Fig. 2)
processing. In the first stage of the interaction, with
organic base concentration in the toluene–piperidine
λ, nm
Fig. 2. Differential electron absorption spectra and curves
of spectrophotometric titration of O=Mo(OH)TPP with
–
4
piperidine in the toluene medium. [Pip] = (a) 1.35×10 –
–
2
1
.62×10 M and (b) 0.27–8.43 M.
–4
mixtures increasing in the range of 1.35×10 –
.62×10–2 M, in the electronc absorption spectra of
О=Мо(ОН)ТРР an isobestic point was observed at λ =
75 nm (Fig. 2); this proved the existence of static
absence of drastic changes in the electron absorption
spectra (new bands appearance or significant band
shift) allowed concluding that the elementary reaction
in the first stage of the interaction proceeded without
1
4
equilibrium between metalloporphyrin and piperidine.
The system stability was proved by the spectra shape
and the invariance of the isobestic point position in
–
extension of the coordination sphere, as the OH ligand
substitution.
K
1
time. The calculation of the equilibrium constant K
1
+
–
O=Mo(OH)TPP + Pip ↔ [O=Mo(Pip)TPP] OH . (1)
and the titration curve are presented in Table 1 and in
Fig. 2. From the slope of the log [(A – A )/(A – A )] –
The second stage of the interaction proceeded at
higher piperidine concentrations, in the range of 0.27–
8.43 M. The reaction stoichiometry was 1:1 (Fig. 3b,
eq
o
∞
eq
logс plot (Fig. 3a, tan α = 1.18), in the first stage of
L
1
the reaction one piperidine molecule interacted with
each metalloporphyrin molecule. The equilibrium
tan α
almost thousand times (K
compared with that of the first stage. The shape of the
= 1.2). The equilibrium constant decreased by
2
3
–1
–1
constant K equaled (2.03±0.28)×10 M , thus being
2
1.76±0.39 M ) as
1
much larger than unity. This, in combination with
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 83 No. 7 2013

QUANTITATIVE STUDY OF THE QUASIEQUILIBRIUM
1437
Table 1. Example of the equilibrium constants calculation for the first and the second stages of О=Мо(ОН)ТРР interaction
with piperidine at 298 K
–4
–2
а
–1
b
[
Pip] = 1.35×10 –1.62×10 , M
[Pip] = 2.70×10 –8.43, M
4
, M–1
K
2
, M–1
[
Pip]×10 , M
А
eq
K
1
[Pip], M
0.27
А
eq
0
0.7756
0.7993
0.8030
0.8149
0.8120
0.8191
0.8251
0.8248
0.8266
0.8339
0.6529
0.5807
0.5199
0.4897
0.4617
0.4136
0.3861
0.3357
1
2
2
3
4
4
5
6
.35
.03
.70
.38
.05
.73
.40
.08
2370
1920
2480
1750
1970
2150
1860
1770
0.47
2.22
1.57
1.52
1.46
1.62
1.39
1.74
2.56
0.74
0.95
1.08
1.15
1.55
1.62
2.02
a
= (2.03±0.28)×10–3 M. K
b
K
1
± δK
1
2
2
± δK = 1.76±0.39 M.
electron absorption spectrum in the second stage of the
reaction changed more significantly (Fig. 1, curves 2, 3;
Fig. 2). The optical density at the absorption maximum
noticeably decreased, and the band became asym-
metric, with the shoulder appearing at the short wave-
length range, later transforming into an intensive band.
No new absorption bands appeared at long wavelength
Thus, the second stage of the reaction of O=Mo·
(OH)TPP with piperidine could be described as the
coordination of the second piperidine molecule to the
eighth coordination site of molybdenum [equation (2)].
The formation of molybdenum(V) complexes with the
coordination number of 8 is more favorable than of
seven-coordinated complexes. According to the extract
[2] of ten thousand structures of the coordination
range, to the right of the maximum at λ = 462 nm.
max
(
а)
(b)
log [(Aeq – A
o
)/(A – Aeq)]
∞
log [(Aeq – A
o
)/(A – Aeq)]
∞
log с
L
log с
L
Fig. 3. The log [(Aeq – A
o
)/(A
∞
L
– Aeq)] – log c dependence for the reaction of O=Mo(OH)TPP with piperidine in the toluene
–4 –2
medium, in the piperidine concentration range of 1.35×10 –1.62×10 M, (a) first stage and of 0.27–8.43 M, (b) second stage. R2
were 0.942 and 0.994, respectively.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 83 No. 7 2013

1
438
MOTORINA, LOMOVA
From the data presented in Table 2, the rate
А
constants for the studied reaction were calculated
Table 3), they were almost independent of the
piperidine concentration. The average rate constant k
(
ef
–
4
–1
was (1.63±0.29)×10 s , the reaction order with
respect to piperidine was close to zero (0.20). Thus, the
experimentally derived kinetic equation was as
follows.
–
d[О=Мо(ОН)ТРР]/dτ = k[О=Мо(ОН)ТРР]·[Pip]0. (3)
λ, nm
In order to kinetically describe the reaction of
O=Mo(OH)TPP with piperidine and to determine its
mechanism, we studied the properties of the inter-
mediates (products corresponding to the equivalence
points at the titration curves) and of the irreversible
reaction final product, at different piperidine con-
centration. The final product was the same at any
piperidine concentration, this was a substance with
Fig. 4. Electron absorption spectra of O=Mo(OH)TPP in
the system metalloporphyrin–piperidine–toluene at piperidine
concentration of 1.62 M in the freshly prepared mixture (1)
and after 24 hours incubation (2). Other curves correspond
to intermediate times.
absorption maxima at λ
419, 514, and 548 nm
max
compounds (as deduced from the X-ray diffraction
data) the population of Mo complexes with coordina-
V
[Table 4; Fig. 4 (band at λ = 548 nm not shown)].
max
tion numbers of 5, 6, 7, and 8 was 13, 32, 0, and 7,
respectively. However, the stability of the eight-
coordinated complex formed in the second stage is
three orders of magnitude lower than that of the seven-
IR spectra were recorded separately for the initial
O=Mo(OH)TPP and for products of different stages of
its interaction with piperidine. In the IR spectrum of
the first (reversible) stage product (Fig. 5, curve 2)
new maxima were revealed with the vibration
frequencies corresponding to that of piperidine [13], at
+
–
coordinated [O=Mo(Pip)TPP] OH formed according
to the reaction (1) in the first stage.
+
–
4
2
02, 548, 728, 785, 1044, 1317, 1496, 2805, 2859, and
[
O=Mo(Pip)TPP] OH + Pip
–1
921 cm ; they were absent in the spectrum of the
K
2
↔
+
–
[O=Mo(Pip)
2
TPP] OH .
(2)
initial complex. In the IR spectrum of the second
(
reversible) stage product, those maxima were revealed
In the second stage of the interaction, that is, at
higher piperidine concentration, the slow reaction was
observed in all the piperidine-containing mixtures.
However, the absence of the isobestic point in the
spectral time series at each piperidine concentration
even better. In the pure piperidine spectrum [13], the
corresponding bands are observed at 429 (446), 545
(
2
546), 741, 824, 1112, 1314, 1441, 2786, 2833, and
–
1
898 cm (two values were given in [13] for the first
two bands). The shift of the piperidine bands to the
lower frequencies in the low-frequency part of the
spectrum and to higher frequencies in its high-fre-
quency part indicated the coordinated piperidine state.
(
Fig. 4) indicated the complexity of the chemical
process. The fact that the absorption spectrum at τ = 0
was not consistent with the other spectra in the time
series, indicated the probability of the fast irreversible
stage or the fast-established pre-equilibrium; the latter
possibility was confirmed by other experimental data.
In Fig. 2b the reversible changes of the electronic
spectra at τ = 0 with increasing piperidine concentra-
tion are shown (the reversibility was proved by
tracking the spectral changes upon dilution of the
mixtures). In the spectral series the isobestic point was
clearly revealed at λ = 453 nm. After the pre-
equilibrium had been established, the slow reaction
was observed at τ ≠ 0, this reaction was accompanied
by changes in the electron absorption spectra with
nicely revealed isobestic points (Fig. 4).
The state of IR signals at 659 and 928 cm–1 that
originated from the Mo–O and Mo=O vibrations,
respectively, in O=Mo(OH)TPP, reflected the changes
of ligand surrounding of Mo upon interaction with
–1
piperidine. The sharp band at 659 cm (Fig. 5, curve 1)
disappeared from the spectra of the products of the
first and the second stages (Fig 5, curves 2, 3). The
–
1
high-frequency absorption band (928 cm ) was
observed in all the spectra; however, its relative
intensity significantly decreased in the products spec-
tra, as so did that of many other bands. The coordina-
tion center in the initial O=Mo(OH)TPP had the С
4
v
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 83 No. 7 2013

QUANTITATIVE STUDY OF THE QUASIEQUILIBRIUM
1439
Table 2. Optical density of the O=Mo(OH)TPP–piperidine reaction mixtures А
time
s
as functions of piperidine concentration and
τ, min
[
Pip],
M
0
5
10
15
20
25
30
35
40
45
50
55
0
.27
.47
.74
.95
.08
.15
.55
.62
0.8056
0.4066
0.3745
0.2883
0.2450
0.2022
0.1315
0.1989
0.7889 0.7829
0.3999 0.3918
0.3661 0.3582
0.2789 0.2712
0.2365 0.2296
0.1958 0.1886
0.7693
0.3835
0.3498
0.2647
0.2235
0.1827
0.7607
0.3759
0.3421
0.2585
0.2175
0.1759
0.1044
0.1534
0.7571
0.3701
0.3358
0.2527
0.2115
0.1701
0.0986
0.1443
0
0
0
1
1
1
1
0.3636
0.3301
0.2468
0.2056
0.1650
0.0932
0.1367
0.3570
0.3241
0.2417
0.2010
0.1589
0.0877
0.1288
0.3513 0.3463 0.3408
0.3179 0.3134 0.3076
0.2371 0.2318 0.2271
0.1962 0.1915 0.1869
0.1532 0.1480 0.1430
0.0828 0.0785 0.0745
0.1215 0.1149 0.1077
0.3354
0.3022
0.2227
0.1825
0.1377
0.0713
0.1012
0.1244 0.11682 0.1105
0.1851 0.1749
0.1653
75
τ, min
[
Pip],
M
6
0
65
70
80
85
90
95
100
105
110
115
0
.27
.47
.74
.95
.08
.15
.55
.62
0
0
0
1
1
1
1
0.3313
0.2976
0.2184
0.1784
0.1329
0.0682
0.0948
0.3263 0.3221
0.2922 0.2874
0.2141
0.3178
0.2811
0.2064
0.3135
0.2727
0.2024
0.3099
0.2664
0.1985
0.3059
0.2601
0.1953
0.3022
0.2532
0.1917
0.2985 0.2952 0.2922
0.2478 0.2423 0.2379
0.1889 0.1855 0.1814
0.2899
0.2326
0.1777
0.1283
0.0661
0.0891
0.1179
0.0794
0.1132
0.0748
0.1096
0.1053
0.1014
0.0982 0.0950 0.0924
0.0902
symmetry, and the Mo atom was displaced out of the
plane of four coordinated N atoms towards the double
bound O atom, by approximately half of angstrom
of the first and the second interaction stages (those
produced in the respective с ranges at τ = 0)
contained coordinated piperidine molecule(s), and the
stoichiometry of the metalloporphyrin–piperidine com-
plexes was 1:1 and 1:2, respectively. Taking into
account the changes in the electronic spectra in the
course of the donor-acceptor complex formation
Pip
[
14]. It was suggested that the resolution of the
metalloporphyrin IR spectrum increased upon its
interaction with piperidine, due to the formation of
more planar coordination node [15]. Thus, the products
(
Table 4) and non-ionizing character of the solvent, the
Table 3. Effective rate constants kef of the reactions in the
system O=Мо(OH)TPP–piperidine–toluene at 298 K as
function of piperidine concentration (0.27–8.43 M)
respective products could be as follows: [O=Mo(Pip)·
+
–
+
–
TPP] OH and [O=Mo(Pip) TPP] OH . Data in Table 4
demonstrate the noticeable difference in the molar
absorptivity of those complexes.
2
4
–1
[Pip], M
(kef ± δkef)×10 , s
0
0
0
0
1
1
1
1
.27
.47
.74
.95
.08
.15
.55
.62
1.4±0.10
1.5±0.10
1.4±0.10
1.4±0.10
1.5±0.10
1.4±0.10
2.2±0.17
2.2±0.10
In the spectra of solid molecular complexes of the
1
:1 and 1:2 composition, as well as in that of the final
product in the chaotic layer and in KBr (Figs. 6, 7), the
shift of the maxima of the coordinated piperidine
bands as compared with the free base (see above) were
less significant than that in the case of the solution
–1
spectra (Fig. 5). The exception was a signal at 1412 cm
as a sharp distinct band in the solid layer, absent in the
case of the initial complex spectrum.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 83 No. 7 2013

1
440
MOTORINA, LOMOVA
Table 4. Parameters of electron absorption spectra of O=Mo(OH)TPP and its reaction with piperidine in the toluene medium,
–
4
–2
at piperidine concentration of 1.35×10 –1.62×10 M and 0.27–8.43 M
λ
max, nm (log ε)
II
Complex
O=Mo(OH)TPP
[Pip], M
I
III
–
634 (3.86)
634 (3.94)
618 (3.17)
548
590 (4.01)
587 (4.10)
578 (3.78)
514
463 (4.95)
461 (4.98)
446 (5.23)
419
+
–
1.62×10–2
[
O=Mo(Piр)TPP] OH
+
–
[O=Mo(Piр)
2
TPP] OH
8.43
Irreversible reaction product
8.43
+
–
[
O=Mo(Pip)
2
TPP] OH , solution
402
410
548
785
1317
1496
1412
2859–2921
2854–2929
2849–2926
Final product, KBr
618
619
1121
1380
1274
Final product, chaotic layer
As far as the final product of O=Mo(OH)TPP–
piperidine interaction (at high concentrations of base)
is concerned, the most differences from the two
intermediate complexes were to be observed in the
electron absorption spectra (Table 4). Upon inter-
action, the spectrum became similar to the absorption
spectra of the Mo(+4) complexes with porphyrin
ν, cm–1
Fig. 5. IR spectra of (1) O=Mo(OH)TPP, (2) [O=Mo(Piр)·
+
–
–4
2
TPP] OH (2) ([Pip] = 4.73×10 M), and (3) [O=Mo(Pip) ·
+
–
–1
ν, cm–1
TPP] OH ([Pip] = 7.43×10 M) in toluene. Signals cor-
responding to the coordinated piperidine vibrations are
marked with vertical lines; signals partially overlapping
with the porphyrin macrocycle vibration signals are marked
with asterix.
Fig. 6. IR spectra of (1) O=Mo(OH)TPP and molecular
+
–
complexes (2) [O=Mo(Piр)TPP] OH and (3) О=Мо(Pip)
2
·
ТРР in the solid chaotic layer at the silicon plate.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 83 No. 7 2013

QUANTITATIVE STUDY OF THE QUASIEQUILIBRIUM
1441
IV
(
O=Mo P) [16]. However, as piperidine is known not
(AcO)MnTPP [12] and 2.2 times higher than that of
ZnTPP [17].
to be a reducer, the structure of the slow irreversible
reaction product that is formed at high piperidine
concentration, after the fast-established equilibriums (1)
and (2), should be that of the piperidine salt of the
donor-acceptor complex [O=Mo(Pip) TPP] OH , iso-
electronic to the structure of Mo (O=Mo TPP)
complex.
3
–1
3
Py[K
1
(9.1±1.2)×10 M ] > Pip [(2.03±0.28)×10 ]
Im[(1.85±0.11)×103].
>
(9)
+
–
2
The (9) series did not correspond to the order of the
change of the molecular ligand basicity; the ligands
IV
IV
pK were 5.23 [18], 11.25 [19], and 7.03 [20],
a
respectively. Moreover, the order of the ligands in the
series according to their complexes stability, similar to
the (9) series, changed in the case of different
complexing metal atoms (for example, change to
ZnTPP), or in different medium (benzene, carbon
tetrachloride) [17]. The low selectivity of complex
formation [the (9) series] was compensated with the
significant increase in the stability of O=Mo(OH)TPP
complexes with N-bases as compared with complexes
of other metals. Due to the reversibility of the pro-
cesses, this could be applied to constructing of the
sensors and other analytical systems. The molecular
complexes thus formed were characterized by
moderately high stability, distinct spectral response
developing within seconds, and by high sensitivity of
+NH
Pip
Pip
Pip
(4)
_
_
k1
Mo+
O
Mo
O
OH
OH
Indeed, from the system of Eqs. (1), (2), and (4) the
rate equation could be deduced corresponding to the
experimentally obtained kinetic equation (3).
In Eq. (5), the rate of the slow stage (2) and the
+
–
concentration of [O=Mo(Pip) TPP] OH could be
2
expressed taking into account equilibriums (1) and (2).
+
–
–
=
dc([O=Mo(Pip)
2
TPP] )OH /dτ
the reaction to the nature of base coordinating atom
+
–
k
1
c([O=Mo(Pip)
2
TPP] )OH ,
(5)
–1
(
K of the reaction with H S was 83 M [21]). The
1
2
+
–
+
–
noticeable optical response in the range of Soret band
in the electron absorption spectra was observed at
c([O=Mo(Pip)
2
TPP] )OH = K
2
c([O=Mo(Pip)TPP]) OH ·[Pip]
c([O=Mo(Pip)TPP] )OH ·const,
+
–
=
K
2
(6)
(7)
–4
piperidine concentration of 10 to 1 M. The nature of
the effect (hyperchromic or hypochromic shift) was
dependent on the base concentration; this might be
+
–
c([O=Mo(Pip)TPP]) OH = K
c[O=Mo(OH)TPP]·[Pip]
c[O=Mo(OH)TPP]·const,
1
c[O=Mo(OH)TPP]·[Pip]
=
K
1
K
=
1
+
–
–
dc([O=Mo(Pip)
–dc([O=Mo(Pip)TPP] )OH /dt
–dc[O=Mo(ОН)TPP]/dt = k
2
TPP] )OH /dτ
+ –
=
=
1
,
K
2
K
1
[O=Mo(ОН)TPP]·const = k [O=Mo(ОН)TPP]. (8)
2
In these expressions const was the concentration of
piperidine which was in large excess as compared with
the equilibrium one, [Pip]. From comparison of Eqs. (8)
and (3) it followed that k = k = k K K . Thus, the
2
1
2
1
experimental rate constant k incorporated two equilib-
rium constants K and K ; their values determined in
1
2
this work allowed to calculate the rate constant of the
limiting stage k .
1
Comparative analysis of the data regarding the
O=Mo(OH)TPP reactions with various bases, as well
as the reactions of piperidine with various metallopor-
phyrins revealed that the stability of O=Mo(OH)TPP
ν, cm–1
1
:1 complexes with N-bases changed only slightly in
the (9) series, whereas the O=Mo(OH)TPP–piperidine
complex stability was 455 times higher than that of
Fig. 7. IR spectra of O=Mo(OH)TPP in KBr tablets (1)
before and (2) after the treatment with piperidine.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 83 No. 7 2013

1
442
MOTORINA, LOMOVA
applied for the semi-quantitative mixture analysis.
Calculation of the numerical value of the optical
response [22] revealed that O=Mo(OH)TPP was
effective as piperidine receptor. For instance, with
δ(C–H)], 1336 (C–N), 1441 (C=N), 441 (Мо–N), 659
(Мо–O), 928 (Мо=O).
Reaction of O=Мо(OH)TPP with piperidine was
studied by spectrophotometry (molar ratios and
excessive concentration methods). Solutions of O=Мо
–
4
piperidine concentration in the range of 1.35×10 –
–
2
1
.62×10 M at 298 K the relative optical response A
opt
(
OH)TPP and piperidine in freshly distilled toluene
equaled 0.1, comparable to the other optical sensors
based on porphyrins and phthalocyanines described in
the literature. At piperidine concentration of 0.27–
were prepared directly before the experiment to avoid
peroxides formation. Optical density of the solutions
series with the constant O=Мо(OH)TPP concentration
(
8
.43 M, A equaled 0.65, much higher than that of
–6
opt
8.77×10 M) and the base concentration in the range
other available systems [22].
–4
of 1.35×10 to 8.43 M was measured at 462 nm at τ =
, and in the time series. The solutions temperature
298 K) was controlled in the special closed
spectrophotometer quartz cell with the accuracy of
0.1 K.
0
(
EXPERIMENTAL
Electron absorption spectra of the solutions were
recorded on a UV-Vis Agilent 8453 (with software for
automatic metrological evaluation of the system and
for quantitative analysis) and Specord M40 spec-
trophotometers; IR solutions spectra were recorded on
a VERTEX 80v spectrometer. IR spectra (on the KBr
±
Rate constants at different piperidine concentrations
were calculated according to the formal first-order
kinetic equation, at the condition of piperidine excess
with respect to the metalloporphyrin (10).
–
1
glasses, 300–3500 cm ) of O=Mo(OH)TPP in toluene
1
A
0
– A
∞
–
4
k = — ln –——— .
(10)
ef
and in toluene–piperidine mixtures ([Pip] = 4.73×10 ,
τ
A
τ
– A
∞
7
.43×10–1 M) were obtained as differential spectra.
The spectrum of toluene, or that of the toluene–
piperidine mixture with the concentration of the latter
corresponding to the equivalence point at the titration
curve (with the part coordinated by metalloporphyrin
subtracted) were considered as the baseline. IR spectra
in the chaotic layer were obtained by the liquid
evaporation from the O=Mo(OH)TPP toluene or
toluene–piperidine ([Pip] = 4.73×10 , 7.43×10 M)
solutions. Final products of the reversible and
irreversible reactions of O=Mo(OH)TPP with piperi-
dine for IR spectra recording from KBr tablet were
isolated in solid form from the incubated O=Mo(OH)
TPP piperidine solution after distillation of the latter.
In this expression А , А , А are the optical densities
0
τ
∞
of the reaction mixture at times zero, τ, and after
reaction was complete.
Equilibrium constants of the formation reactions of
the reversible donor-acceptor complexes were
determined according to Eq. (11), based on the law of
mass action and Bouguer–Lambert–Beer law, the latter
being applied to two colored substances: O=Мо(OH)
–
4
–1
·
TPP and its molecular complex with piperidine.
A – A
eq
0
—
———
A
∞
– A
0
1
K = —––——— · ————————– .
(11)
n
A
eq – A
0
A
eq – A
0
1
– ———–
c
L
– c 0M P ———–
A – A
(
Hydroxo)oxo-(5,10,15,20-tetraphenylporphi-
nato)molybdenum(V) [O=Mo(OH)TPP] [23]. 0.1 g
∞
A – A
0
∞
0
(
(
0.16 mmol) of H TPP was boiled with 0.076 g
2
0
In this equation с , с are initial concentrations of
MР
L
0.53 mmol) of МоО in 0.8 g of phenol at 454 K
3
O=Мо(OH)TPP and piperidine, respectively; А , А ,
А are optical densities (τ = 0) of the O=Мо(OH)TPP
0
eq
during 4 h. The complex was isolated in solid form by
∞
vacuum distillation of phenol, dissolution in CHCl ,
3
solution, of the equilibrium mixture at certain con-
centration of piperidine, and of the final coordination
product, respectively; n was the number of the
coordinated piperidine molecules.
and double elution with CHCl through the Al O
3
2
3
column. Two elution zones were obtained, of pink (un-
reacted porphyrin) and green (complex) colors. Yield
6
0%. Electron absorption spectrum (in chloroform),
λ
, nm (log ε): 620.0 (2.94), 584.0 (2.92), 456.0
The optimization of K and k and the determination
max
ef
–
1
(
3.78). IR spectrum (KBr), ν, cm : 701, 752 [γ(C–H),
of the standard deviation were performed by the least
squares method in Microsoft Excel software. The
benzene], 1070, 1177 [δ(C–H), benzene], 1484, 1596
C=C), 800 [γ(C–H), pyrrole], 1018 [C –C , C–N,
(
relative error of K and k determination did not exceed
3
4
ef
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 83 No. 7 2013

QUANTITATIVE STUDY OF THE QUASIEQUILIBRIUM
1443
2
3 and 7%, respectively. The sample calculation of K
–2
10. Guseva, L.Zh., Pukhovskaya, S.G., Semeikin, A.S., and
Golubchikov, O.A., Rus. J. Coord. Chem., 2007, vol. 33,
no. 2, pp. 116–119
–4
at piperidine concentration in the 1.35×10 –1.62×10
M and 0.27–8.43 M ranges is given in Table 1.
1
1
1
1. Bains, M.S. and Davis, D.G., Inorg. Chim. Acta., 1979,
ACKNOWLEDGMENTS
vol. 37, pp. 53–60.
2. Karmanova, T.V., Koifman, O.I., and Berezin, B.D.,
This work was performed in the frames of
Programs of fundamental investigations of the
Presidium of the Russian Academy of Sciences no. 7
Koord. Khim., 1983, vol. 9, no. 7, p. 919.
3. Bol’shakov, G.F. and Glebovskaya, E.A., Tablitsy
chastot infrakrasnykh spektrov geteroorganicheskikh
soedinenii (Tables of Infrared Spectra Frequencies of
Heteroorganic Compounds), Leningrad: Khimiya, 1968.
(
2011) and no. 8 (2012), Federal targeted program
Scientific and scientific-pedagogical staff of
innovative Russia” for 2009–2012 (State contract no.
“
1
1
4. Buchler, J.W. and Rohbock, K., Inorg. Nucl. Chem.
0
2.740.11.0106), and of Ministry of Education and
Lett., 1972, vol. 8, no. 12, pp. 1073–1076.
Science Program “Development of the high school
scientific potential” no. 2.2.1.1/2820 (2011).
5. Lomova, T.N. and Berezin, B.D., Rus. J. Coord. Chem.,
2
001, vol. 27, no. 2, pp. 85-104.
REFERENCES
16. Buchler, J.W., Kokisch, W., and Smith, P.D., Structure
and Bonding, 1978, vol. 34, p. 79.
1
2
. Stiefel, E.I., Prog. Inorg. Chem., 1977, vol. 22, p. 1.
1
1
7. Lebedeva, N.Sh., Dr.Sci (Chem.) Dissertation, Ivanovo,
007.
. Solov’ev, V.P., Stuklova, M.S., Koltunova, E.V., and
Kochanova, N.N., Rus. J. Coord. Chem., 2003, vol. 29,
no. 9, pp. 660–668.
. Dement’ev, I.A., Kozin, A.O., Kondrat’ev, Yu.V.,
Korol’kov, D.V., and Proyavkin, A.A., Rus. J. Gen.
Chem., 2007, vol. 77, no. 5, pp. 822–843
. Pecsok, R.I. and Sawyer, D.T., J. Am. Chem. Soc., 1956,
vol. 78, no. 21, pp. 5496–5500.
. Honig, D.S. and Kustin, K., J. Am. Chem. Soc., 1973,
vol. 95, no. 21, pp. 5525–5528.
. Nazarova, M., Podlahova, J., and Podlaha, J., Coll.
Czech. Chem. Commun., 1968, vol. 33, pp. 1991–2003.
. Tipugina, M.Yu., Motorina, E.V., and Lomova, T.N.,
Rus. J. Inorg. Chem., 2007, vol. 52, no. 3, pp. 394–397.
. Tipugina, M.Yu., Lomova, T.N., and Motorina, E.V.,
Rus. J. Coord. Chem., 2005, vol. 31, no. 5, pp. 357–363.
. Lomova, T.J., Porphyrins & Phthalocyanines, 2006,
vol. 10, nos. 4–6, p. 750.
2
8. Obshchaya organicheskaya khimiya (General Organic
Chemistry), Samms, P.G., Ed., Moscow: Khimiya,
3
1
985, vol. 8.
1
2
9. Khimicheskaya enciklopediya (Chemistry Encyclo-
pedia), Knunyanc, I.L., Ed., Moscow: Sovetskaya
Encyclopediya, 1992, vol. 3, p. 1029.
0. Khimicheskaya enciklopediya (Chemistry Encyclo-
pedia), Knunyanc, I.L., Ed., Moscow: Sovetskaya
Encyclopediya, 1990, vol. 2, p. 411.
4
5
6
7
8
9
21. Lomova, T.N., Motorina, E. V., Ovchenkova, E.N., and
Klyueva, M.E., Bul. Rus. Acad. Sci. Chem., 2007, no. 4,
p. 636.
22. Saeed Shahrokhian, Abdollah Taghani, Ali Hamzehloei,
and Reza Mousawi, S., Talanta, 2004, vol. 63, pp. 371–
3
76.
2
3. Lomova, T.N., Volkova, N.I., and Berezin, B.D., Zh.
Neorg. Khim. 1985, vol. 30, no. 3, p. 626.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 83 No. 7 2013