Study of spectral and kinetic characteristics of products of photolysis of a trifunctional compound with light of different wavelengths

Article abstract of DOI:10.1134/S001814391204011X

Spectral and kinetic characteristics of intermediate products of photolysis of a novel phototrifunctional compound (PTC), whose molecule combines spironaphthoxazine, hydroxyazomethine, and azobenzene fragments, have been studied by microsecond flash photo

Full text of DOI:10.1134/S001814391204011X

ISSN 0018ꢀ1439, High Energy Chemistry, 2012, Vol. 46, No. 4, pp. 259–265. © Pleiades Publishing, Ltd., 2012.
Original Russian Text © P.P. Levin, A.S. Tatikolov, N.L. Zaichenko, A.I. Shienok, L.S. Kol’tsova, I.R. Mardaleishvili, L.D. Popov, S.I. Levchenkov, A.A. Berlin, 2012, published in
Khimiya Vysokikh Energii, 2012, Vol. 46, No. 4, pp. 307–313.
PHOTOCHEMISTRY
Study of Spectral and Kinetic Characteristics of Products
of Photolysis of a Trifunctional Compound with Light
of Different Wavelengths
a
a
b
b
b
P. P. Levin , A. S. Tatikolov , N. L. Zaichenko , A. I. Shienok , L. S. Kol’tsova ,
b
c
c
b
I. R. Mardaleishvili , L. D. Popov , S. I. Levchenkov , and A. A. Berlin
a
Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, ul. Kosygina 4, Moscow, 119334 Russia
eꢀmail: levinp@sky.chph.ras.ru
Semenov Institute of Chemical Physics, Russian Academy of Sciences, ul. Kosygina 4, Moscow, 119991 Russia
b
c
Faculty of Chemistry, Southern Federal University, Southern Scientific Center, Russian Academy of Sciences, ul. Zorge 7,
RostovꢀonꢀDon, 344090 Russia
Received November 24, 2011
Abstract—Spectral and kinetic characteristics of intermediate products of photolysis of a novel phototrifuncꢀ
tional compound (PTC), whose molecule combines spironaphthoxazine, hydroxyazomethine, and azobenꢀ
zene fragments, have been studied by microsecond flash photolysis with UV and visible light in toluene and
methanol solutions. Three products of PTC photolysis have been detected. It has been found that the effiꢀ
ciency of the photoprocesses substantially depends on the solvent and the wavelength of excitation light.
DOI: 10.1134/S001814391204011X
Works on design and study of the properties of phoꢀ example, photoinduced ring opening, proton transfer
tocontrolled hybrid photochromic systems are extenꢀ process, and luminescence. We found using nanosecꢀ
sively developing at present. On the one hand, of interꢀ ond flash photolysis that during photolysis of PBC, a
est are photochromic probes and labels, which permit, few photoproducts are observed, which differ in the
using light, monitoring the properties of a modified maximums of the absorption spectra and whose relaꢀ
object [1]. On the other hand, such compounds are tive yields depend on the medium and the wavelength
promising for creation, on their basis, of materials for of excitation light [4–6]. One of the compounds studꢀ
molecular electronics: optical switches, logical ied is a model of two allꢀphotonic logical devices [7].
devices, and others [2, 3].
To develop works on the photochemistry of hybrid
For this purpose, we studied the dynamics of phoꢀ multiaddressed compounds, we have synthesized a
toprocesses in a number of novel photobifunctional novel phototrifunctional compound (PTC), whose
compounds (PBC), whose molecule includes two molecule combines three different structural fragꢀ
structurally different fragments, in which two different ments, in which photoprocesses different in nature
processes can occur under the action of light, for can occur:
2
''' 3'''
3
'' 4''
4
'''
N
HO
N
6
''' 5'''
6
''
4
Me Me
10'
9'
2'
N
N CH
5
6
α
PTC
N O
Me
7'
7
5' 6'
Me Me
HO
N
N
N
N
N O
Me
1
2
3
259

260
LEVIN et al.
In spironaphthoxazine 1, being a constituent of form A has an intense absorption band at 337 nm
the PTC molecule, a photochromic process occurs and does not practically absorb in the region of
under the action of light, which includes photodisꢀ 400–500 nm [8]. Photoexcitation of 1 with UV light
sociation of the C–O spiro bond in the initial closed leads to the formation of the open merocyanine
form A and subsequent cis–trans isomerization to form B with
λ
≈
600 nm and a sufficiently high
max
form the colored merocyanine form B. The closed quantum yield (about 0.2) [8].
Me Me
Me Me
N
N
h
ν
N
O
N
O
Me
Me
B
A
.
In salicylidenenaphthylamine 2, being the second
constituent of the PTC molecule, analogous to well fragments are combined in such a manner that conjuꢀ
studied salicylideneanilines [9–13], under the action gation exists between the
ꢀelectron systems of
of light, conversion of the cisꢀenol form to the trans
spironaphthoxazine, hydroxyazomethine, and
In the PTC molecule, the three aforementioned
π
ꢀ
keto form can occur as a result of electronically azobenzene fragments in the ground state of the molꢀ
excitedꢀstate intramolecular proton transfer (ESIPT) ecule.
conjugated with cis–trans isomerization:
Hence, in PTC we may expect the occurrence of all
HO
three described above photoisomerization processes of
different nature, which lead to the formation of specꢀ
trally different photoproducts. This peculiarity of PTC
can be useful regarding the possible application as
molecular switches, especially upon realization of
N
NH
t
E
K
O
An important property of salicylidenenaphthyꢀ selective photoexcitation of various processes by variꢀ
с
lamine 2 is that it occurs in the cisꢀenol form
Е
ation of the exciting light wavelength and the medium.
(
λ
= 360 nm) in toluene, whereas the presence of
max
c
cisꢀketone is noticeable
(
λ
= 460 nm) along with E
max
in MeOH solution [14].
EXPERIMENTAL
HO
N
O
To prepare solutions, methanol and toluene (UV
spectroscopic grade) were used.
NH
c
E
K
Absorption spectra in the UV and visible regions
were measured on a MultiSpecꢀ1501 spectrophotomꢀ
eter.
Azobenzene 3 was chosen as the third constituent
of the PTC molecule, because in this fragment the
occurrence of the process of trans–cis isomerization
about the N=N bond, occurring reversibly and with a
high quantum yield, was expected, which was well
The absorption spectra and the formation and
decay kinetics of the intermediate products were meaꢀ
sured in the time range
≥
1 s on a microsecond flash
μ
studied for azobenzenes [15–20]. The initial trans
ꢀ
photolysis apparatus with registration of the electronic
absorption [4]. Combinations of standard light filters
for photolyzing flash lamps were used, which transꢀ
mitted UV light with 300 ≤ λ ≤ 370 nm or visible light
with 400 ≤ λ ≤ 500 nm. The data presented in this work
are average values obtained as a result of analysis of at
least ten kinetic curves under the indicated conditions.
All measurements were carried out at room temperaꢀ
isomer has a broad absorption band with a maximum
at about 350 nm, whereas the cisꢀisomer exhibits an
absorption maximum at about 450 nm [15, 17]. The
cisꢀisomer of 3, as a rule, is characterized by a long
lifetime (with respect to the form B1).
N
1
ture. The H NMR spectra were recorded on a Bruker
N
N
N
t
c
WMꢀ400 spectrometer in CDCl at 25 С.
3
°
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STUDY OF SPECTRAL AND KINETIC CHARACTERISTICS OF PRODUCTS
261
1
,3ꢀDihydroꢀ8'ꢀ(2ꢀhydroxyꢀ5ꢀ
A
1.0
phenylazobenzylidenimino)ꢀ1,3,3ꢀtrimethylspiro[2Hꢀ
indolꢀ2,3'ꢀ[3H]naphtho[2,1ꢀb][1,4]oxazine] (PTC)
1
2
To a hot solution of 1,3ꢀdihydroꢀ8’ꢀaminoꢀ1,3,3ꢀ
trimethylspiro[2Hꢀindolꢀ2,3’ꢀ[3H]naphtho[2,1ꢀ
b][1,4]oxazine] (0.5 g, 1.45 mmol), which was
obtained according to the procedure described in [21],
in absolute ethanol (20 ml), a hot solution of 5ꢀphenyꢀ
lazosalicylic aldehyde (0.338 g, 1.49 mmol), which
was synthesized according to [22], in absolute ethanol
0.5
(
15 ml) was added and refluxed for 2 h. Then, the mixꢀ
ture was cooled to room temperature, and the precipꢀ
itate was filtered off and recrystallized from acetoniꢀ
trile. Orangeꢀred powder (0.4 g, 50%) with mp 225–
0
3
00
400
, nm
500
λ
2
27 C was obtained, whose purity was checked by eleꢀ
°
1
mental analysis, H NMR spectrum, and thinꢀlayer
chromatography. Found: C, 76.11; H, 5.35; N, 12.76.
Calculated for C H N O : C, 76.20; H, 5.30; N,
Fig. 1. Absorption spectra of PTC (5
methanol and ( ) toluene.
×
10–5 mol L–1) in (
1
)
2
35
29
5
2
12.70. Rf = 0.52 (with chloroform eluent and SiO2
TLC plates (Merck)).
1
observed in the H NMR spectrum of the keto isomer)
bound to an aromatic core is located in the region of
2
1H NMR (400 MHz, CDCl3,
J
/Hz), /ppm: 1.37,
δ
1
6
.38 (both s, 3 H each, С(СН ) ); 2.79 (s, 3Н, NCH );
3 2 3
.5–5.0 ppm. The broadening of the OHꢀgroup signal
at 14 ppm indicates the presence of an intramolecular
.60 (d, 1 H, H(7), 3J6, 7 = 7.8); 6.93 (t, 1 H, H(5),
3
3J4, 5 = 3J5, 6 = 7.4); 7.08 (d, 1 H, H(3''), J3'',4'' = 9.0); hydrogen bond, that is, that the initial state of the PTC
3
E
7
.10 (d, 1 H, H(4), J4, 5 = 7.4); 7.18 (d, 1 H, H(5), molecule in toluene is
A
. Since it is known that the
ground state of azobenzenes (and, hence, the correꢀ
sponding fragment in the PTC molecule) is the trans
isomer (with respect to the N=N bond), the complete
description of the initial state of the PTC molecule in
3
3
3
J5, 6 = 8.8); 7.24 (dd, 1 H, H(6), J5, 6 = 8.8
,
J6, 7
=
3
ꢀ
8
.8); 7.47 (d, 1 H, H(4''), J4'',3'' = 9.1); 7.53 (dd, 2 H,
3
3
H(3'''), H(5'''), J2''',3' ''
= J3''',4''' = 7.7); 7.65 (d, 1 H,
3
4
E
t
H(9’), J9',10' = 8.9, J7',9' = 3.2); 7.70 (d, 1 H, H(7’),
toluene can be A . Here and below we use the followꢀ
4
3
ing notation to describe the states of all three constitꢀ
uent fragments in the PTC molecule. The letters A and
B denote the state of the spirocyclic fragment; the
superscript and the subscript denote the states of the
hydroxyazomethine and azobenzene fragments,
respectively. Unfortunately, it is impossible to deterꢀ
mine, using the method of NMR spectroscopy, in
which form these compounds occur in an alcoholic
solution due to very low solubility of them in alcohols.
J7',9' = 3.2); 7.72 (1 H, H(6’), J5',6' = 8.9); 7.79 (s,
3
3
1
7
H, H(2')); 7.90 (d, 2 H, H(2''), H(6''),
J
J5'',6''
= =
'',3''
2
4
3
.7); 8.06 (dd, 1 H, H(4''), J4'',3'' = 8.9, J4'',6'' = 2.3);
4
8
.11 (1 H, H(6''), J4'',6'' = 2.3); 8.64 (d, 1 H, H(10'),
3
J9',10' = 9.0); 8.92 (s, 1H, Н ). 14.08 (broadened s,
α
1
H, OH).
RESULTS AND DISCUSSION
Figure 1 shows the electronic absorption spectra of
PTC. Their longꢀwavelength edge is bathochromically
shifted with respect to the spectra of the constituent
fragments. The absorption spectrum of PTC in a toluꢀ
ene solution also indicates the existence of PTC in the
E
Absorption Spectra of PTC
1
It follows from the H NMR spectra (see Experiꢀ
mental) that the compound of interest in a chloroform
solution occurs in the closed form of the spirocyclic
fragment with the enol form of the salicylidenimine A t form, because the shoulder at about 470 nm charꢀ
Е
1
fragment, that is,
А
(within the accuracy of the H acteristic of the cisꢀketone is absent [6, 11].
NMR method); only the enol form of the salicylidenꢀ
imine fragment is also observed in a toluene solution of
PTC, analogously to PBC studied earlier, including
those containing such electronꢀwithdrawing groups as
The presence of a weak absorption band in the
region of about 470 nm in the absorption spectrum of
PTC in methanol indicates the noticeable presence,
E
Kc
a nitro group [4]. This is indicated by the presence in along with A t , of the cisꢀketo form A t
.
This is in
1
the H NMR spectra of the signal of a hydroxy group accordance with the known fact that the azo group is
bound to an aromatic core with δ ≈ 14 ppm, whereas an electronꢀwithdrawing substituent with the strength
the signal of protons of an amino group (should be being between NO and NO groups [24] and, hence,
2
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262
LEVIN et al.
favors the shift of the thermal keto–enol equilibrium B. The absorption spectrum of this product is characꢀ
toward the cisꢀketone.
terized by a band with a maximum at about 450 nm
Fig. 2, spectrum ), which corresponds to absorbance
of the cisꢀisomer of the fragment
(
2
3.
Intermediate Products of PTC Photolysis in Toluene
In the case of visible light photolysis, the relative
yield of the cisꢀisomer of the fragment is significantly
UV light flash photoexcitation of PTC in toluene
solutions leads immediately after the flash to an
appearance of the merocyanine form B of the fragꢀ
ment 1, which possesses a characteristic absorption
spectrum with a maximum at about 600 nm (Fig. 2,
3
higher (Fig. 3). This intermediate product is formed
within the time of a light flash, as well as B.
Hence, upon photolysis of PTC in toluene, at least
spectrum 1
) [4, 5, 8]. The decay kinetics of the absorꢀ two processes occur, (1) spiro cycle opening in the
bance of the form B in the region of λ ≥ 600 nm is fragment 1 to form the deeply colored merocyanine
described by the firstꢀorder rate law with a rate conꢀ form (Scheme 1) and (2) trans–cis isomerization of
stant of 0.56 s–1, which coincides with the data for the the azobenzene fragment 3 leading to the formation of
Е
form
В
of PBC studied in our earlier works [4, 5].
the cisꢀphotoisomer, which has a much longer lifetime
and absorbs in the visible region (Scheme 2).
However, in the shorter wavelength region, a relaꢀ
tively weak absorbance of an intermediate with a much
The relative yields of these intermediate products
longer lifetime (with a firstꢀorder rate constant of significantly depend on the wavelength of excitation
0
.036 s–1) is observed after disappearance of the form light.
N
HO
N
N
N
HO
N
N
Me Me
Me Me
N
N
N O
Me
N
O
Me
E
t
E
t
A
B
Scheme 1. The process of spiro cycle opening in PTC yielding the merocyanine form.
N
HO
N
N
Me Me
Me Me
N
N
HO
N
N
O
N
O
Me
Me
N N
E
t
E
A
A
c
Scheme 2. Trans–cis isomerization in the PTC molecule.
Note that for PTC in toluene in the time range studied, ESIPT in the fragment 2 of the molecule, that is, relatively
Kt
the formation of photoproducts appearing as a result of shortꢀlived A t (Scheme 3), is not observed.
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STUDY OF SPECTRAL AND KINETIC CHARACTERISTICS OF PRODUCTS
263
A
.10
A
0.02
0
1
1
0.05
0.01
2
2
0
4
0
4
00
500
600
700
00
500
600
700
λ
, nm
λ
, nm
Fig. 2. Absorption spectra of the intermediate products
Fig. 3. Absorption spectra of the intermediate products
obtained upon UV light flash photolysis of PTC in toluene
obtained upon visible light flash photolysis of PTC in toluꢀ
(1) immediately and (2) within 10 s after a light flash.
ene (1) immediately and (2) within 10 s after a light flash.
N
O
N
N
HO
N
N
HC
NH
Me Me
Me Me
N
N
N O
Me
N
O
Me
E
t
Kt
A
A
t
Scheme 3. ESIPT in the PTC molecule.
In analogous PBC and model compounds studied
UV light flash photoexcitation of PTC in methanol
by us earlier, the corresponding lifetimes of the form solutions leads immediately after flash to the appearꢀ
Kt
A
were no less than 10 s [4, 5]. For PBC containing
µ
ance of the only photoproduct, the merocyanine form
an NO2 group in the SA fragment, the yield of the form
with ESIPT drastically dropped as compared with
other compounds, and in the case of PBC Brꢀ and
NO2ꢀsubstituted in the SA fragment, the formation of
the form
pose that for PTC these forms are characterized by
short lifetimes ( s).
E
of the fragment 1 – B , which possesses a characterisꢀ
t
tic absorption spectrum with a maximum at about 600
nm [4, 5, 8]. The decay kinetics of the absorbance of
Kt
E
A
was not observed at all [4]. We may supꢀ the form
is described by the firstꢀorder equation
Bt
–1
with the rate constant of 0.48 s
.
≤1 µ
Upon visible light photolysis of PTC in methanol
solutions, the formation of three photoproducts is
observed. The shortestꢀlived photoproduct (with the
decay rate constant of 24 s ) is characterized by an
absorption spectrum with a maximum in the longꢀ
Intermediate Products of PTC Photolysis in MeOH
–1
The initial state of PTC molecules in methanol is a
E
predominance of the form A t with a small amount of wavelength region at about 650 nm and a noticeable
Kc
absorbance in the region of 450–500 nm (Fig. 4, specꢀ
trum ). We observed earlier the analogous photoprodꢀ
uct upon photolysis in methanol solutions of analoꢀ
gous PBC containing only fragments and [4]. It
was identified as the merocyanine form B of the fragꢀ
the form A t
.
1
N
1
2
O
N
Me Me
H
N
Kc
N
ment
1 bound to the cisꢀketo form of 2, that is, B .
t
The analogous form is apparently formed also upon
N
O
Kc
Me
visible light photolysis of PTC from the form
methanol solutions (Scheme 4).
A
t
in
Kc
t
A
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264
LEVIN et al.
N
O
N
NH
N
N
Me Me
O
N
Me Me
H
N
N
N
O
Me
N
O
Me
Kc
t
Kc
A
B
t
Scheme 4. Spiro cycle opening process in A Kt c to form the merocyanine form.
Kc
Note that a source of Bt can be not only the closed
The substantial increase in the rate constant of cis–
trans isomerization on passing from toluene to methaꢀ
nol (25 times) is due to solvation effects and is typical
on passing to alcohols [25].
Kc
form A t present in methanol in a small amount,
Kc
which can convert to Bt upon absorption of a light
quantum. It is very probable that in PTC, analogously
Kc
The third photoproduct, which has the longest lifeꢀ
time, is completely analogous to that observed upon
UV flash photoexcitation of PTC in methanol soluꢀ
tions and represents PTC with the merocyanine form
to PBC studied earlier [4], Bt also appears upon phoꢀ
toexcitation of the enol form of PTC. We may suppose
Kc
that Bt is formed as a result of occurrence of photoꢀ
tropic processes being variation of thermodynamic
relaxation of the common precursor of the B forms.
B of the fragment
1, in which no changes occur in
E
other fragments, namely, Вt (Fig. 4, spectrum
2).
The second intermediate product is characterized
by an absorption spectrum with a maximum at about
4
Hence, three processes occur upon photolysis of
PTC in methanol: (1) spiro cycle opening in the fragꢀ
50 nm and the decay rate constant of 0.89 s–1 (Fig. 4,
ment
without changing configuration of other fragments;
2) trans–cis isomerization of the azobenzene fragꢀ
ment leading to an appearance of the corresponding
1 to form the deeply colored merocyanine form,
spectrum
2). We may suppose that this is the form of
PTC with the cisꢀisomer of the fragment
3
, namely,
(
E
A , because all B forms absorb in much longerꢀwaveꢀ
c
3
length spectral region.
cisꢀisomer absorbing in the near visible region, withꢀ
out changing configuration of other fragments; (3)
Kc
spiro cycle opening in PTC in the form A t to form
A
.02
the deeply colored merocyanine form, but a portion of
this product is possibly formed also as a result of paralꢀ
lel cis–trans isomerization with proton transfer in the
0
1
fragment
2.
2
0.01
The kinetic data obtained indicate that the forms
E
t
Kc
E
В , В , and Ac are not converted to one another, but
t
E
Kc
3
return to the initial forms At and A t during the
course of the dark reaction. Hence, the photoproꢀ
cesses observed, on the one hand, occur in parallel,
but, on the other hand, the formation of the final form
Kc
0
4
00
500
600
700
λ
, nm
В
in methanol can also involve the proton transfer
t
Fig. 4. Absorption spectra of the intermediate products
obtained upon visible light flash photolysis of PTC in
methanol (
after a light flash.
process. The relative yields of these intermediate prodꢀ
ucts substantially depend on the wavelength of excitaꢀ
tion light.
1) immediately and within (2) 0.2 and (3) 2 s
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STUDY OF SPECTRAL AND KINETIC CHARACTERISTICS OF PRODUCTS
265
CONCLUSIONS
8. Lokshin, V., Sama, A., and Metelitsa, A.V., Usp. Khim.
002, vol. 71, p. 1015.
. Dudek, G.O. and Dudek, E.P., J. Am. Chem. Soc.
966, vol. 88, p. 2407.
0. Fabian, W.M.F., Antonov, L., Nedeltcheva, D.,
Kamounah, F.S., and Taylor, P.J., J. Phys. Chem. A
004, vol. 108, p. 7603.
,
2
A photochromic phototrifunctional compound
that is colored by the action of not only UV, but also
visible light has been synthesized. The relationship
among the efficiencies of the photoprocesses occurꢀ
ring in this compound substantially depends on the
wavelength of excitation light. The initial and intermeꢀ
diate absorption spectra, as well as the kinetic behavior
of the system, essentially depend on the solvent
nature, which, along with the wavelength of photolyzꢀ
ing light, provides additional possibilities to control
photochromism.
9
,
1
1
,
2
1
1. Ziotek, M., Kubicki, J., Naskrecki, R., and
Grabowska, A., J. Chem. Phys., 2006, vol. 124,
p. 124518.
1
2. Pita, P., Lusina, E., Radzewicz, Cz., and Grabowska, A.,
J. Chem. Phys., 2006, vol. 125, p. 184508.
1
1
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3. Gostev, F.E., Petrukhin, A.N., Titov, A.A., Nadꢀ
tochenko, V.A., Sarkisov, O.M., Metelitsa, A.V., and
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ACKNOWLEDGMENTS
This work was supported by the Ministry of Science
and Education, State Contract no. 02.740.11.0815 at
4.04.2010, and the Russian Academy of Sciences
2
5. Rau, H., in Photoreactive Organic Thin Films
Sekkat, Z., Knoll, W, Eds., Amsterdam: Academic,
002, p. 3.
,
under Presidium program no. 7.
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6. Gilbert, A. and Baggott, J., Essentials of Organic Photoꢀ
chemistry, Oxford: Blackwell, 1990.
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HIGH ENERGY CHEMISTRY
Vol. 46
No. 4
2012