Features of photolytic transformation of [4-(2-methyl-5-t-butyl- cyclohexadiene-1,5-dion-3,4-yl)-3-methyl-6-tert-butyl-catecholato] triphenylantimony(V)

Article abstract of DOI:10.1134/S1070363209070123

Photolysis of [4-(2-methyl-5-tert-butyl-cyclohexadiene-1,5-dion-3,4-yl)-3- methyl-6-t-butyl-catecholato] triphenylantimony(V) in toluene by irradiation with the light of wavelength 546 nm leads to excitation of the molecule of parent compound which reacts

Full text of DOI:10.1134/S1070363209070123

ISSN 1070-3632, Russian Journal of General Chemistry, 2009, Vol. 79, No. 7, pp. 1483–1486. © Pleiades Publishing, Ltd., 2009.
Original Russian Text © E.V. Ilyakina, O.G. Mishchenko, A.I. Poddel’skii, S.V. Maslennikov, I.V. Spirina, 2009, published in Zhurnal Obshchei Khimii,
2009, Vol. 79, No. 7, pp. 1126–1129.
Features of Photolytic Transformation
of [4-(2-Methyl-5-t-butyl-cyclohexadiene-1,5-dion-3,4-yl)-3-
methyl-6-tert-butyl-catecholato]triphenylantimony(V)
E. V. Ilyakinaa, O. G. Mishchenkoa, A. I. Poddel’skiib,
S. V. Maslennikova, and I. V. Spirinaa
a Chemical Research Institute, Lobachevskii Nizhnii Novgorogd State University
pr. Gagarina, 23, korp. 5, Nizhnii Novgorod, 603950 Russia
e-mail: spirina@ichem.unn.ru
b Razuvaev Institute of Organometallic Chemistry, Russian Academy of Sciences, Nizhnii Novgorod, Russia
Received October 16, 2008
Abstract—Photolysis of [4-(2-methyl-5-tert-butyl-cyclohexadiene-1,5-dion-3,4-yl)-3-methyl-6-t-butyl-cate-
cholato]triphenylantimony(V) in toluene by irradiation with the light of wavelength 546 nm leads to excitation
of the molecule of parent compound which reacts with a molecule of Ph3SbCatQ affording 4,4'-di-(3-methyl-6-
tert-butyl-o-benzoquinone) and 4,4'-di[(3-methyl-6-tert-butyl-catecholato)triphenylantimony(V)]. The formed
compounds react with each other returning the system into the initial state. Action of light of wavelength 313
and 405 nm on the initial reaction mixture leads to the formation of carbon monoxide, Ph3SbCatCatSbPh3 and
the products of photolytic transformation of 4,4'-di(3-methyl-6-tert-butyl-o-benzoquinone).
DOI: 10.1134/S1070363209070123
Among the methods of synthesis of [4-(2-methyl-5-
tert-butyl-cyclohexadiene-1,5-dion-3,4-yl)-3-methyl-6-
tert-butyl-catecholato]triphenylantimony(V) (Ph3SbCat–
Q) there is a reaction between 4,4'-di-(3-methyl-6-tert-
butyl-о-benzoquinone) (Q–Q) and 4,4'-di-[(3-methyl-
6-tert-butyl-catecholato)triphenylantimony(V)] (Ph3SbCat–
CatSbPh3) [1]:
Electron absorption spectra of equimolar mixture of
Q–Q and Ph3SbCat–CatSbPh3 registered in the course
of the reaction process are characterized by the
presence of an isobestic point at the λ = 350 nm and
undergo changes with the appearance of absorption
bands at 410 and 505 nm (Fig. 1а). The first maximum
corresponds to π–π* transition in the carbonyl group of
the quinone fragment [2]. The second corresponds to
the charge transfer complex [1]:
Ph3SbCat–CatSbPh3 + Q–Q → 2 Ph3SbCat–Q.
(1)
Ph
O
O
Ph
O
O
Ph Sb
Ph Sb
O−
O
+
O
O
Ph
Ph
e−
Ph3SbCat–Q
Ground state
Excited state
In the course of the photolysis of Ph3SbCat–Q the
electron absorption spectra have an isobestic point at
the wavelength 350 nm, and the changes in the optical
density are just opposite to the observed in the course
of the reaction (1). Upon irradiation of the initial
compound in toluene by the light of wavelength 546 nm
the optical density of the reaction mixture at 505 nm
decreases by no more than 30–40% of its initial value
1483

1484
ILYAKINA et al.
(a)
(b)
D
1.0
0.9
0.8
D
0.9
0.8
0.7
1
0.7
0.6
0.5
0.4
0.3
0.2
0.1
1
2
0.6
0.5
3
3
4
5
0.4
0.3
0.2
0.1
6
7
2
300
350
400
450
λ, nm
500
550
600
300
350
400
450
λ, nm
500
550
600
Fig. 1. (а) Electron absorption spectra of compounds (1) Q–Q and (2) Ph3SbCat–CatSbPh3, and (3) changes in the spectra of their
equimolar reaction mixture in the process of the synthesis of Ph3SbCat–Q, recorded each 3 min. С(Q–Q) = C(Ph3SbCat–CatSbPh3) =
2×10–4 mol l–1, T = 298 K; (b) The spectra of reaction mixture at the photolysis of Ph3SbCat–Q in toluene with the light of λ = 546 nm.
C(СPh3SbCat–Q) = 2.3×10–4 mol l–1, I0,spec = 9.8×1017 quant s–1 l–1, T = 298 K, l = 0.71cm. (1) 0; (2) 2.5; (3) 5; (4) 9; (5) 15; (6) 25;
and (7) 50 min.
(Fig.1b). By the method of TLC compounds Q–Q and
Ph3SbCat-CatSbPh3 were detected in the reaction
mixture obtained at the photolysis of Ph3SbCat–Q. In
the course of the photolysis no formation of carbon
monoxide was observed.
Ph3SbCat–Q + hν → Ph3SbCat–Q*,
(2)
(3)
Ph3SbCat–Q* + Ph3SbCat–Q
→ Ph3SbCat–CatSbPh3 + Q–Q.
As far as the decrease in the optical density at the
photolysis of Ph3SbCat–Q by the light with the
wavelength 546 nm is only 40% or less, and
compounds Q–Q and Ph3SbCat–CatSbPh3 do not
absorb the initiating irradiation, the most probable
pathway of transformation of the products formed in
reaction (3) is the reaction between these compounds
along Eq. (1). In this case the optical density at the
wavelength 505 nm should fall to the limit when the
rate of photolysis of Ph3SbCat–Q is the same as the
rate of reaction between Q–Q and Ph3SbCat–
CatSbPh3. Therewith, the concentrations of the system
components correspond to the steady state. As a
consequence, both the positions of absorption bands
and the optical densities at the band maxima in the
spectra of the reaction mixture in UV and visible
regions remain unchanged.
The scope of these observations allows an
assumption that photolytic transformation of Ph3SbCat–Q
can proceed along the following scheme:
D
0.65
0.60
0.55
0.50
3
2
1
0.45
0.40
0
50
100
150
200
250
A complementary evidence of this hypothesis is
given by the following two sets of experiments. At the
illumination of Ph3SbCat–Q in toluene by the light λ =
546 nm of different intensity occurs a change in the
initial rate constant of the photolytic transformation of
this compound. Moreover, the lesser intensity of the
t, min
Fig. 2. Changes in the optical density in the course of
photolysis of Ph3SbCat–Q in toluene at λ = 505 nm at
varied intensity of incident illumination. C(Ph3SbCat–Q) =
2.3×10–4 mol l–1, λphot = 546 nm, T = 298 K. (1) 9.8×1017,
(2) 7.8×1017, and (3) 2×1017 quant s–1 l–1.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 79 No. 7 2009

FEATURES OF PHOTOLYTIC TRANSFORMATION
18
1485
D
0.36
(b)
2
16
14
12
10
(a)
0.34
0.32
5
4
3
2
8
6
0.30
0.28
1
1
4
2
0
0
20
40
t, min
60
80
100
Fig. 3. (а) Effect of Ph3SbCat–CatSbPh3 additive on the
rate of photo-transformation of Ph3SbCat–Q at λ = 546 nm
0
200
400
600
t, min
800 1000
in toluene. C(Ph3SbCat–Q) = 1.85×10–4 mol l–1, I0,spec
=
9.8×1017 quant s–1 l–1, T = 298 K. Concentration of
Ph3SbCat–CatSbPh3 in the reaction mixture before the
photolysis: (1) 0, (2) 1.28×10–5, (3) 5.28×10–5, (4) 1.06×
10–4, and (5) 1.74×10–4 mol l–1; (b) Restoration of optical
density of the reaction mixtures at the wavelength 505 nm
after ceasing illumination.
Fig. 4. Accumulation of carbon monoxide in the course of
photolysis of Ph3SbCat–Q in toluene. T = 298 K,
C(Ph3SbCat–Q) = 2.30×10–4 mol l–1. (1) l = 313 nm, I0,spec
=
2.25×1017 quant s–1 l–1, (2) 405 nm, I0,spec = 5.10×
1018 quant s–1 l–1.
light consumed by the reaction system, the lesser
conversion is required for attaining the steady state by
the system. The steady state is characterized by a
plateau on the kinetic curve of the change in optical
density (Fig. 2). In the second set of the experiments
the initial concentration of Ph3SbCat–Q and intensity
of the absorbed light were kept constant, but prior to
the photolysis Ph3SbCat–CatSbPh3 was added to the
reaction mixture to various concentrations. The higher
was the concentration of the added Ph3SbCat–
CatSbPh3 component, the faster was achieved the
steady state (Fig. 3а). After ceasing the light action on
the system, the optical density of the latter on the
wavelength 505 nm returned to its initial value (Fig. 3b).
decomposition at the action of light of the wavelength
λ 313 and 405 nm, that proceeds with liberation of
carbon monoxide. Eventually, in the reaction mixture
after the photoplysis of Ph3SbCat–Q were detected by
TLC Ph3SbCat-CatSbPh3, 6-tert-butyl-4-(4'-tert-butyl-
2'-methyl-3'-oxocyclopenta-1',4'-dienyl)-3-methyl-1,2-
pyrocatechol, 3,3'-di(2-methyl-5-tert-butylcyclopenta-
2,4-dienone) and 5,5'-di-tert-butyl-3,3'-dihydroxy-2,2'-
dimethylbicyclohexylidene-2,5,2',5'-tetraene-4,4'-dione.
EXPERIMENTAL
The compounds Ph3SbCat–Q and Ph3SbCat-
CatSbPh3 were synthesized along the procedure in [1].
Hexane and nonane of “chemicaly pure” grade were
dried according to commonly used procedures [4] and
then were distilled collecting the fractions 68.6–69.0°С
and 150–151°С respectively.
Illumination of Ph3SbCat–Q solution in toluene
with the light of shorter wavelengths destroys the
steady state of the system and leads to complete
expenditure of the initial compound. One product of
the photolytic decomposition of Ph3SbCat–Q dissolved
in a hydrocarbon by the light of λ 313 or 405 nm is
carbon monoxide, its yield is, respectively, 0.5 and
1 mole of СО per one mole of transformed compound
(Fig. 4). The kinetic curves of СО accumulation
include induction period that points to the gas
formation in the secondary processes. The 4,4'-di(3-
methyl-6-tert-butyl-о-benzoquinone) appearing at the
photolysis of Ph3SbCat–Q by the data of [3] undergoes
The construction of photolytic installation and
procedures for measuring intensity of incident beam
have been described in [5].
The amount of carbon monoxide was measured by
chromatography on a Tsvet-104 instrument, glass
column 1500×2.5 mm filled with active charcoal STK
with granule size 0.2–0.4 mm, temperature of the oven
and detector 70°С, katharometer bridge current 250 mА,
carrier gas (helium) flow rate 25 ml min–1.
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1486
ILYAKINA et al.
Abakumov, G.A., Organomet. Chem., 2005, vol. 690,
The IR spectra of the products of photolysis were
registered on a Shimadzu IR Prestige-21 instrument
from KBr pellets.
p. 1273.
2. El’tsov, A.V., Studzinskii, O.P., and Grebenkina, V.M.,
Usp. Khim., 1977, vol. 46, no. 2, p. 185.
The TLC analysis of the products of photolysis [4]
was carried out on silica gel plates Silufol UV 254, a
mixture of hexane–diethyl ether (4:1) was used as eluent.
The elution was carried out in a closed chamber, under
the atmosphere saturated with the eluent vapor.
3. Mishchenko, O.G., Maslennikov, S.V., Spirina, I.V.,
Druzhkov, N.O., Kurskii, Yu.A., and Maslennikov, V.P.,
Zh. Obshch. Khim., 2007, vol. 77, no. 12, p. 1997.
4. Spravochnik khimika (Chemist’s Handbook), Nikol’-
skii, B.P., Moscow: Khimiya, 1964, vol. 2.
5. Klement’eva, S.V., Mishchenko, O.G., Kurskii, Yu.A.,
Faerman, V.I., Maslennikov, S.V., Spirina, I.V., Fu-
kin, G.K., and Druzhkov, N.O., Zh. Obshch. Khim.,
2007, vol. 77, no. 6, p. 967.
REFERENCES
1. Cherkasov, V.K., Grunova, E.V., Poddel’sky, A.I.,
Fukin, G.K., Kurskii, Yu.A., Abakumova, L.G., and
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 79 No. 7 2009