Synthesis and kinetics of photochemical reactions of novel bifunctional salicylideneiminospironaphthoxazines

Article abstract of DOI:10.1007/s11172-008-0341-z

A series of novel photochemically bifunctional compounds was synthesized. Their molecules combine the photochromic spironaphthoxazine fragment with a salicylideneimine fragment containing various substituents. The latter can undergo intramolecular proton transfer in the electron-excited state. Photolysis products of three types, namely, open merocyanine forms having an enol or cis-keto form of the salicylideneimine moiety and a trans-keto form with the closed spiro fragment, were detected using pulse photolysis technique in toluene and methanol solutions. The spectral kinetic characteristics of the photoproducts were studied, and their quantum yields were measured. The effects of substituents in the salicylideneimine fragment and the solvent nature were discussed.

Full text of DOI:10.1007/s11172-008-0341-z

Russian Chemical Bulletin, International Edition, Vol. 57, No. 11, pp. 2394—2401, November, 2008
2394
Synthesis and kinetics of photochemical reactions of novel
bifunctional salicylideneiminospironaphthoxazines
N. L. Zaichenko,a P. P. Levin,b I. R. Mardaleishvili,a A. I. Shienok,a
L. S. Kol´tsova,a O. Yu. Os´kina,a and A. S. Tatikolovb
aN. N. Semenov Institute of Chemical Physics, Russian Academy of Sciences,
4 ul. Kosygina, 119991 Moscow, Russian Federation.
Fax: +7 (495) 137 8284. Eꢀmail: zaina@polymer.chph.ras.ru
bN. M. Emanuel Institute of Biochemical Physics, Russian Academy of Sciences,
4 ul. Kosygina, 119991 Moscow, Russian Federation.
Fax: +7 (495) 137 4101. Eꢀmail: levinp@sky.chph.ras.ru
A series of novel photochemically bifunctional compounds was synthesized. Their molꢀ
ecules combine the photochromic spironaphthoxazine fragment with a salicylideneimine fragꢀ
ment containing various substituents. The latter can undergo intramolecular proton transfer in
the electronꢀexcited state. Photolysis products of three types, namely, open merocyanine forms
having an enol or cisꢀketo form of the salicylideneimine moiety and a transꢀketo form with the
closed spiro fragment, were detected using pulse photolysis technique in toluene and methanol
solutions. The spectral kinetic characteristics of the photoproducts were studied, and their
quantum yields were measured. The effects of substituents in the salicylideneimine fragment
and the solvent nature were discussed.
Key words: synthesis, photobifunctional compounds, photochromism, spironaphthoxazine,
proton transfer, pulse photolysis, NMR spectroscopy.
Photochromic compounds experiencing reversible
phototransformations, which are accompanied by changes
in color and other properties, attract considerable attenꢀ
tion because they can be used in diverse areas. These are
the creation of automated photomodulators,1 detecting
media for optical memory,2,3 molecular logical devices,4,5
protein activity photoswitchers,6 and others.
R1 = R2 = H (1); R1 = R2 = Cl (2); R1 = H, R2 = Br (3);
1 = H, R2 = NO2 (4); R1 = Br, R2 = NO2 (5)
Hybrid molecules containing different fragments, each
of which can undergo photochemical transformations
mainly related to ring opening,7—9 have recently been
synthesized in order to extend the functional properties of
photochromic compounds. In the photobifunctional comꢀ
pounds developed by us, the hybrid molecules contain
two functionally different fragments in which light can
induce two different photoprocesses, for example, photoꢀ
cyclization or ring photoꢀopening, proton transfer, lumiꢀ
nescence, charge transfer, etc.
For the purpose to investigate photochemistry of biꢀ
functional compounds,10,11 namely, to study the effects of
substituents and medium on the efficiency of formation
of various products and their decay, we synthesized for
the first time a series of new bifunctional compounds
1—5, whose molecules include the salicylideneimine
fragment with various substituents in addition to the
spironaphthoxazine fragment.
R
The photochromic process including the photodissoꢀ
ciation of the O—Cspiro bond in initial closed form A to
form intermediate cisꢀcisoid isomer X followed by cis—
transꢀisomerization to colored merocyanine form B
occurs in spironaphthoxazines upon irradiation. It has
earlier12 been found by femtosecond laser absorption
spectroscopy that cisꢀcisoid isomer X is formed in spiroꢀ
naphthoxazines within ~300 fs, whereas colored form B
is produced within 16 ps.
It is known13—17 that salicylideneanilines (SA) exist in
solution in two tautomeric forms: cisꢀketone and cisꢀenol.
The ratio of these tautomers depends on the temperature,
solvent, and nature of substituents in SA. The enol form
predominates in nonpolar solvents at room temperature,
whereas the presence of the cisꢀketo form is observed in
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2346—2352, November, 2008.
1066ꢀ5285/08/5711ꢀ2394 © 2008 Springer Science+Business Media, Inc.

Photochemically bifunctional compounds
Russ.Chem.Bull., Int.Ed., Vol. 57, No. 11, November, 2008 2395
Scheme 2
polar hydroxylꢀcontaining solvents (such as alcohols). The
introduction of electronꢀwithdrawing substituents into
the aniline part of the SA molecule shifts equilibrium
to the enol form in any solvent,15 whereas the same subꢀ
stituents introduced into the phenol part of the SA
molecules give an opposite effect.13
Photoirradiation of SA can induce reversible photoꢀ
chemical transformations, namely, transition from the
enol to keto form due to excited state intramolecular proꢀ
ton transfer (ESIPT). The primary ESIPT process occurs
within the time less than 80 fs to form intermediate forms,
which are further transformed into the relatively stable
transꢀisomer (AKt) through rotation of the fragments of
the molecule about the C(1″)—C(7) bond within ~11 ps
(see Refs 14 and 18). The quantum yield of the transꢀketo
form for 2ꢀhydroxynaphthylideneꢀ1´ꢀnaphthylamine in
methylcyclohexane17 and N,N´ꢀbis(salicylidene)ꢀpꢀpheꢀ
nylenediamine in acetonitrile16 is ~30%. It should be menꢀ
tioned that upon photoexcitation the cisꢀketo form is not
transformed into the transꢀketo form.13
and microsecond pulse photolysis technique. Unsubstiuted
spironaphthoxazine 6 was also studied as a model for
comparison.
For photochemically bifunctional compounds (PBC)
1—5 studied in this work one can expect the both deꢀ
scribed above processes to occur: the photochromic proꢀ
cess with O—Cspiro bond cleavage followed by cis—transꢀ
isomerization in the spironaphthoxazine fragment of the
molecule (Scheme 1) and ESIPT in the salicylideneimine
fragment (Scheme 2).
The absorption spectra and decay kinetics of products
of the two described above processes that occur in the
PBC molecules, namely, in open form B, whose formaꢀ
tion completes the photochromic process in the spiroꢀ
naphthoxazine fragment, and transꢀketo form AKt
appeared due to the ESIPT in the salicylideneimine
fragment and its isomerization, were studied by nanoꢀ
The 1H NMR spectra (see Experimental) show that in
chloroform all compounds under study exist in enol form
AE (within the accuracy of the NMR method), and the
single enol form is observed in toluene for unsubstituted
PBC 1 and PBC 4 containing strong withdrawing subꢀ
stituents. This is indicated by the 1H NMR signal at
δ ≈ 9.3—14 from the OH group attached to the aromatic
ring, whereas the signal of protons of the amino group
(which should be observed in the 1H NMR spectrum
of the keto isomer) attached to the aromatic ring lies at
δ 2.5—5.0 (Ref. 19). The state of the substituent in posiꢀ
tion 2″ of the salicylideneimine fragment is indicated by
the chemical shift of the adjacent H(3″) proton. In the
case of the enol form, the electronꢀreleasing OH group
should exert the upfield shift of the signal of the H(3″)
proton compared to the signals of other proton of the
aromatic ring. In the case of the keto isomer, the keto
group, being itself a electronꢀwithdrawing substituent,
should produce a downfield shift for this signal. The
observed upfield (relatively to other aromatic protons)
shift of the signal of the H(3″) proton unambiguously
indicates the electronꢀdonor character of the adjacent
group and, hence, that the compounds exist in enol form
AE. Unfortunately, NMR spectroscopy does not allow
one to establish the form of these compounds in an
ethanolic solution because of too low solubility of the
latter in alcohols.
Scheme 1

2396
Russ.Chem.Bull., Int.Ed., Vol. 57, No. 11, November, 2008
Zaichenko et al.
А
it is relatively low even for the compounds containing
nitro groups.
0.7
1
Pulse photoexcitation of model compound 6 in toluꢀ
ene and methanol solutions in the time interval ≥10 ns
produces the only photoreaction product: merocyanine
form B possessing the characteristic absorption spectrum
with a maximum at ~600 nm. The decay kinetics for form
B obeys a monoexponential law. The obtained decay rate
constants of form B (kB) for compound 6 coincide with
known published data20 (Table 1).
0.6
0.5
0.4
0.3
0.2
Pulse photoexcitation of the PBC in toluene in the
time interval ≥10 ns produces two photoproducts (the
exception is compound 5). A shortꢀliving product (which
is not observed in the case of compound 5) also appears
in addition to the relatively longꢀliving merocyanine
form B with λmax = 600 nm analogous to form B for
compound 6. The spectrum of the shortꢀliving product
with λmax = 500 nm corresponds to the known absorption
spectra16,17 of transꢀketo form AKt.
0.1
0
2
300
400
500
λ/nm
Fig. 1. Absorption spectra of compound 4 in toluene (1) and
MeOH (2) (C = 5.6•10–5 mol L–1, l = 0.5 cm).
The absorption spectra of compound 4 in toluene and
MeOH are shown in Fig. 1. The absorption spectra of
other PBC in the region of wavelengths shorter than
400 nm resemble the spectrum of compound 4 and have
absorption band maxima at 320—370 nm. The exception
is the most informative (from the viewpoint of existence
of the cisꢀketo form) longwaveꢀlength part of the specꢀ
trum, because this is the region that allows one to judge
about keto—enol equilibrium in the salicylideneaniline
fragment of the molecule. It is known13—17 that in the
absorption spectra of SA the absorption band with a maxiꢀ
mum at 370 nm corresponds to the enol form and that
with a maximum at 450 nm belongs to the cisꢀketo form.
Almost no band at 450 nm is observed in the absorption
spectra of the PBC studied in toluene solutions. This
band is noticeable only in the spectra of nitroꢀcontaining
compounds 4 and 5 in MeOH, whereas it is nearly absent
from the spectra of other PBC in MeOH. Thus, in alcoꢀ
holic solutions the compounds studied mainly exist in
enol form AE, whereas the fraction of cisꢀketo form AKc
grows with an increase in the acceptor properties of
the substituents in the SA fragment of the molecule, but
The quantum yield of form B (ϕB) for PBC 1 is subꢀ
stantially lower than that for compound 6 because of the
efficient competition with ESIPT (Table 2). The quanꢀ
tum yield of form AKt for PBC 1 is somewhat lower than
ϕB. It should be mentioned that the total quantum yield
of two colored forms (ϕ + ϕB) for 1 is close to ϕB for
Kt
model compound 6 (seeATable 2).
The introduction of halogen atoms into the phenyl
ring of the salicylideneimine fragment (compounds 2
and 3) exerts almost no effect on the yield of forms B
and AKt in toluene, whereas the introduction of the nitro
group (compounds 4 and 5) increases the total yield
of form B due to its stabilization. In this case, the yield of
A
Kt decreases sharply (see Table 2). It is known20 that the
introduction of electronegative substituents into the naphꢀ
thalene fragment of compound 6 increases the quantum
yield of form B due to its stabilization. On the contrary,
electronegative substituents in the phenyl ring of SA
prevent the formation of the “twisted” keto state or the
chargeꢀtransfer state, which is the precursor of AKt
(see Ref. 21).
Table 1. Rate constants for decay of the colored forms
Comꢀ
pound
B
AKt
Toluene
MeOH
Toluene
MeOH
AKt
A
AKt
A
kBE
kBE
kBK
k1,
k2, Kt•109
k1,
kq, Kt•109
/s–1
/L mol–1 s–1
/s–1
/L mol–1 s–1
s–1
1
2
3
4
5
6
1.6
0.57
1.2
0.74
0.51
0.54
0.54
0.38
0.54
0.78
0.58
0.67
15
16
17
16
14
—
4000
1000
3500
520
—
3.5
1.5
1.8
0.98
—
8800
28000
14000
93000
—
0.04
0.36
0.31
0.87
—
—
—
—
—

Photochemically bifunctional compounds
Russ.Chem.Bull., Int.Ed., Vol. 57, No. 11, November, 2008 2397
Table 2. Quantum yields (ϕ) of the colored forms
Comꢀ
pound
B
AKt
Total yield of colored forms
Toluene
MeOH
Toluene
MeOH
Toluene
MeOH
ϕBE
ϕBE
ϕBK
ϕAKt
ϕAKt
ϕBE + ϕAKt
ϕBE + ϕBK + ϕAKt
1
2
3
4
5
6
0.076
0.071
0.076
0.28
0.28
0.23
0.040
0.025
0.040
0.055
0.068
0.051
—
0.10
0.096
0.11
0.021
—
0.12
0.082
0.097
0.013
—
0.18
0.17
0.19
0.30
0.28
0.23
0.18
0.13
0.16
0.09
0.054
0.19
0.0063
0.0097
0.0076
0.0029
0.19
—
—
The decay kinetics of form B in the case of PBC 1
obeys a monoexponential law (Fig. 2), and the kB value
for form B of compound 1 (see Table 1) is appreciably
higher than the corresponding value for model compound
6, which can be due to the weak electronꢀdonor character
of the salicylideneimine substituent in the spironaphthoxꢀ
azine fragment.20
The introduction of electronegative substituents into
the salicylideneimine fragment elongates the lifetime (deꢀ
creases the decay rate constants) of form B in toluene
solutions, indicating a decrease in the electronꢀdonor
properties of this fragment.
The lifetime of form AKt in toluene is substantially (by
three orders of magnitude) shorter than that of form B.
The lifetimes about 1 ms are typical of the colored forms
of salicylideneanilines and related compounds in both
solutions and crystalline state.22—24 The decay kinetics of
AKt (Fig. 3) obeys a law of the mixed first and second
orders, because two processes occur: cis—transꢀisomerꢀ
ization followed by intramolecular backward proton transꢀ
fer and bimolecular proton exchange between AKt, which
finally results (with some probability depending, most
likely, on the ratio of acidꢀbase properties of the fragꢀ
ments containing the N and O atoms) in the formation of
the transꢀenol forms. The corresponding rate constants of
the first and second order (k1,A and k2,AKt) are listed in
Kt
Table 1 (the k2,A value was calculated from the experiꢀ
Kt
mental k2,AKt/εl values, where l is the optical path length
equal to 1 mm, and ε is the molar absorption coefficient
of AKt accepted to be 1.5•104 L mol–1 cm–1 at the band
maximum about 500 nm).25 The k2,AKt value for 1 is close
to the rate constant of a diffusionally controlled reaction
(kd = 8RT/3η ≈ 1•1010 L mol–1 cm–1, where η is viscosity),
as should be expected for the proton exchange reaction.
The introduction of electronegative substituents into the
salicylideneimine fragment is accompanied by a decrease
in the decay rate constants for AKt via both routes due to
the stabilization of the protonꢀtransferred forms.
The pulse photoexcitation of PBC 1 in methanol in
the time interval ≥10 ns produces three photoproducts
with λmax = 500, 600, and 620 nm (Fig. 4). A considerably
shorterꢀliving merocyanine form BKc (the corresponding
rate constants k
and k
are given in Table 1) is
BE
BK
observed in addition to longꢀliving form B analogous in
spectral kinetic characteristics to form B in toluene with
λmax = 600 nm (merocyanine form with the enol saliꢀ
cylideneimine fragment BE). This BKc form has a substanꢀ
tially broader absorption spectrum shifted to the longꢀ
A
A
0.1
0.08
0.04
0.05
1
2
1
2
0
2
4
t/s
100
200
300
400
τ/μs
Fig. 2. Decay kinetics of the intermediate products detected at
600 nm under the conditions of laser pulse photolysis of comꢀ
pound 1 (1•10–4 mol L–1) in toluene (1) and MeOH (2).
Fig. 3. Decay kinetics of the intermediate products detected at
500 nm under the conditions of laser pulse photolysis of comꢀ
pound 1 (1•10–5 mol L–1) in toluene (1) and MeOH (2).

2398
Russ.Chem.Bull., Int.Ed., Vol. 57, No. 11, November, 2008
Zaichenko et al.
the sharp increase in the quantum yield of BKc upon the
introduction of electronegative substituents into the
salicylideneimine fragment suggest that in BKc saliꢀ
cylideneimine fragment exists as cisꢀketone or in the
zwitterionic form.
D
0.1
1
Another argument in favor of the aforesaid is the
fact that the absorption spectrum of BKc contains bands in
the region of 450 nm characteristic of the absorption
of the cisꢀketo form of SA,14—17 which is not observed in
the absorption spectra of BE.
0.05
It should be mentioned that the source of BKc can be
not only closed form AKc, which exists in a minor amount
in methanol and can transform into BKc upon the absorpꢀ
tion of a photon. The relatively high quantum yield of BKc
even for PBC 2 and 3, which exist in a methanolic soluꢀ
tion exclusively in the enol form, indicates, most likely,
that BKc is also formed due to the photoexcitation of the
enol form of the PBC. It can be assumed that BKc is
formed due to phototropic processes, being a variety
of thermodynamic relaxation of the common precursor of
forms B. Therefore, the total yield of two forms B is
almost independent of substituents.
2
3
0
450
550
650
750
λ/nm
Fig. 4. Absorption spectra of the intermediate products obtained by
the laser pulse photolysis of PBC 1 in methanol (1•10–4 mol L–1
0.5 μs (1), 0.5 ms (2), and 0.5 s (3) after a laser pulse.
)
wavelength region with λmax = 620 nm. It should be
mentioned that two open forms decay independently of
each other.
The quantum yields of two forms B (ϕB and ϕ
)
K
The signal at λmax = 500 nm in methanol, as in the
case of the solution in toluene, was ascribed to form AKt.
In both methanol and toluene solutions, the yield of form
E
calculated on the basis of assumption about equalityBof
the corresponding molar absorption coefficients are given
in Table 2. The total quantum yield of two forms B in the
case of PBC 1 in methanol is close to ϕB in toluene, as
the total quantum yield of photocoloring (see Table 2).
Unlike the process in toluene, in methanol the introꢀ
duction of electronegative substituents into the salicylideneꢀ
imine fragment exerts a weak effect on the total yield of
A
Kt decreases for the compounds with the electronegative
substituents in the salicylideneimine fragment (comꢀ
pounds 2—5). As in toluene, the electronegative substituꢀ
ents in the phenyl ring of SA prevent the formation of the
“twisted” keto state or the chargeꢀtransfer state,21 which
is the precursor of AKt.
The decay kinetics of AKt in methanol obeys a firstꢀ
order law with the rate constant that depends linearly on
the concentration of the PBC due to two processes:
intramolecular backward proton transfer and bimolecular
proton exchange between AKt and molecules of the initial
form, which finally results in the formation of the starting
PBC. The corresponding rate constants of the first and
merocyanine form B (ϕB + ϕ K). However, in this case,
E
the yield of BE drops sharply Band that of BKc increases.
Unlike the kinetic behavior of BE in toluene, in methanol
the introduction of electronegative substituents into
the salicylideneimine fragment weakly affects the decay
kinetics of the both forms of B.
It seems hardly probable that two forms of B are two
different isomers of open form B, which differ only by
the conformation of the merocyanine fragment.26 Relaꢀ
tively high decay rate constant indicates that for BKc with
λmax = 620 nm the salicylideneimine fragment has proꢀ
nounced electronꢀdonor properties. This fact and
second order (k
and kq,AKt) are listed in Table 1 (the
Kt
kq,A value was1,cAalculated from the slope of the correꢀ
Kt
sponding linear dependences). The k
value is by
Kt
two orders of magnitude lower than theq,rAate constant of
the diffusionally controlled reaction (~1•1010 L mol–1 s–1
in methanol).
The compounds with the electronegative substituents
exhibit acceleration of the both channels of AKt decay
rather than retardation as in toluene, which is explained,
most likely, by an increase in lability of the corresponding
protons.
The obtained kinetic data indicate unambiguously that
forms AKt, BE, and BKc are not transformed into each
other but return to the initial form AE during the dark
reaction. Thus, two photoprocesses, viz., ring opening
in the spironaphthoxazine fragment and proton transfer in
the salicylideneimine fragment, occur, on the one hand,

Photochemically bifunctional compounds
Russ.Chem.Bull., Int.Ed., Vol. 57, No. 11, November, 2008 2399
and purified by chromatography on a column packed with silica
gel (45—70 μm (Aldrich), benzene with gradual addition of 0.5,
1, 2, 5, and 10% acetone as eluent). The fractions containing the
yellowꢀorange Schiff base with Rf 0.66 (chloroform—acetone
(19 : 1) mixture) were collected, evaporated on a rotary
evaporator, and crystallized from a benzene—hexane (3 : 1)
mixture. Lemonꢀyellow crystals with m.p.. 171—174 °C were
obtained in a yield of 0.16 g (32%). Found (%): C, 77.81;
H, 5.44; N, 9.39. C29H25N3O2. Calculated (%): C, 77.83; H,
5.63; N, 9.39. 1H NMR (CDCl3), δ: 1.38, 1.39 (both s, 3 H each,
CMe2); 2.79 (s, 3 H, NMe); 6.61 (d, 1 H, H(7), 3J6,7 = 7.8 Hz);
6.92 (t, 1 H, H(5), 3J4,5 = 3J5,6 = 7.3 Hz); 6.98 (td, 1 H, H(4″),
independently of each other, but on the other hand, in
methanol the formation of the final form B can also
include the proton transfer process. It was shown that the
solvent exerts the decisive influence on the number of
observed photoproducts, kinetics, and mechanism of their
transformation into the initial forms of the PBC. The
substituents in the salicylideneimine fragment of the PBC
molecules affect the ratio of the photoreaction routes, but
this effect is weaker than that of the solvent.
Experimental
3
4
3J3 ,4 = J
= 7.5 Hz, J
= 1.8 Hz); 7.06 (d, 2 H, H(5´),
″
4 ,6
″
″
″
″
″
4 ,5
The 1H NMR spectra were recorded on a Bruker WMꢀ400
spectrometer at 25 °C.
The UVꢀVis absorption spectra were recorded on Specord
UVꢀVis and MultiSpecꢀ1501 spectrophotometers.
H(6´), 3J5´,6´ = 8.8 Hz); 7.11 (d, 1 H, H(4), 3J4,5 = 7.3 Hz); 7.25
(ddd, 1 H, H(6), 3J5,6 = 7.3 Hz, 3J6,7 = 7.8 Hz, 4J4,6 = 1.0 Hz);
3
3
7.40 (ddd, 1 H, H(5″), J4 ,5 = 7.5 Hz, J5 ,6 = 8.9 Hz,
″ ″ ″ ″
4J3 ,5 = 1.3 Hz); 7.44 (dd, 1 H, H(3″), J3 ,4 = 7.5 Hz,
3
″
″
″ ″
3
The absorption spectra and the kinetics of formation and
decay of intermediate products in concentrated solutions
(≥1•10–4 mol L–1) were measured on a nanosecond laser
photolysis technique with detection of electronic absorption.27,28
A nitrogen laser operating in the frequency mode of 10 Hz was
used as the excitation source (PRA LN 1000, pulse duration
1 ns, radiation wavelength 337 nm). Accumulation and averaging
of kinetic curves (16—128 laser pulses per each curve) were
carried out using a UF.258 highꢀperformance analogꢀtoꢀdigital
converter (Sweden) attached to a personal computer based on
the Pentium 4 processor. Depending on the duration of the
process, each kinetic curve contained from 4096 to 16 384 points
remote at the distance from 4 to 400 ns. The data presented in
the work are average values obtained by the processing of at least
10 kinetic curves for the indicated conditions. The absorption
spectra and the decay kinetics of intermediate products in dilute
solutions (≤1•10–5 mol L–1) were also detected on a microꢀ
second pulse photolysis setup with detection of electronic
absorption.29
4J3 ,5 = 1.3 Hz); 7.60 (dd, 1 H, H(9´), J9´,10´ = 8.9 Hz,
″ ″
4J7´,9´ = 2.0 Hz); 7.65 (d, 1 H, H(7´) J7´,9´ = 2.0 Hz); 7.67 (d,
4
1 H, H(6″), 4J4 ,6″ = 1.8 Hz); 7.79 (s, 1 H, H(2´)); 8.62 (d, 1 H,
″
3
H(10´), J9´,10´ = 8.9 Hz); 8.79 (s, 1 H, H(7″)); 13.5 (br.s, 1 H,
OH´). 1H NMR (tolueneꢀd8), δ: 1.09, 1.24 (both s, 3 H each,
CMe2); 2.46 (s, 3 H, NMe); 6.31 (d, 1 H, H(7), 3J6,7 = 7.8 Hz);
6.73 (ddd, 1 H, H(5), 3J4,5 = 7.5 Hz, 3J5,6 = 7.2 Hz, 4J5,7 = 1.0 Hz);
3
6.72 (d, 1 H, H(5´), J5´,6´ = 8.8 Hz); 6.83 (ddd, 1 H, H(6),
3
4
3J5,6 = 7.2 Hz, J6,7 = 7.8 Hz, J4,6 = 2.0 Hz); 6.86 (dd, 1 H,
3
4
H(4), J4,5 = 7.5 Hz, J4,6 = 2.5 Hz); 6.97 (dd, 1 H, H(3″),
4
3J3 ,4 = 7.5 Hz, J3 ,5 = 1.4 Hz); 7.01—7.11 (m, 3 H, H(4″),
″
″
″ ″
4
H(5″), H(6″)); 7.22 (d, 1 H, H(7´), J7´,9´ = 2.2 Hz); 7.25 (dd,
3
4
1 H, H(9´), J9´,10´ = 8.9 Hz, J7´,9´ = 2.2 Hz); 7.26 (d, 2 H,
H(6´), 3J5´,6´ = 8.8 Hz); 7.61 (s, 1 H, H(2´)); 8.16 (s, 1 H, H(7″));
3
8.93 (d, 1 H, H(10´), J9´,10´ = 8.9 Hz); 13.61 (s, 1 H, OH).
8´ꢀ(2ꢀHydroxyꢀ3,5ꢀdichlorobenzylideneimino)ꢀ1,3,3ꢀtrimethylꢀ
1,3ꢀdihydrospiro[2Hꢀindoleꢀ2,3´ꢀ[3H]naphtho[2,1ꢀb][1,4]ꢀ
oxazine] (2). A mixture of compound 7 (0.17 g, 0.49 mmol) and
3,5ꢀdichlorosalicylaldehyde (0.1 g, 0.53 mmol) in anhydrous
toluene (40 mL) was refluxed for 3 h slowly distilling off 30—35 mL
of toluene. The remained amount of the solvent was distilled off
on a rotary evaporator. The residue was chromatographed on a
column packed with silica gel (45—70 μm (Aldrich), benzene
as eluent). The fractions with Rf 0.77 (chloroform—acetone
(18 : 1) mixture) were collected, the eluent was evaporated on
a rotary evaporator, and the residue was recrystallized from a
benzene—hexane (3 : 1) mixture. Compound 4 (0.1 g, 27%) was
obtained as orange crystals with m.p. 229—230 °C. Found (%):
C, 67.27; H, 4.53; Cl, 13.94; N, 7.91. C29H23Cl2N3O2. Calcuꢀ
lated (%): C, 67.45; H, 4.49; Cl, 13.73; N, 8.14. 1H NMR
(CDCl3), δ: 1.37, 1.38 (both s, each 3 H, CMe2); 2.78 (s, 3 H,
Solutions of PBC with the same absorbance (D = 1) at the
exciting light wavelength with λ = 337 nm were used in
determination of the quantum yield of photoproducts. The ϕ
B
values were measured by comparing with model compound 6
assuming that the molar absorption coefficients of the correꢀ
sponding forms B are equal and ϕ = 0.23 and 0.19 for compound
V
6 in toluene and MeOH (see Ref. 20), respectively.
The ϕ Kt values were measured by comparing the absorption
of AKt at tAhe absorption maximum at 500 nm with allowance for
the absorption of B at this wavelength with the absorption of B
at the band maximum at 600 nm, and it was assumed that the
ratio of the corresponding molar absorption coefficients of B
and AKt at the maximum is 3 (see Refs 25 and 30).
8´ꢀAminoꢀ1,3,3ꢀtrimethylspiro[2Hꢀindoleꢀ2,3´ꢀ[3H]naphthoꢀ
[2,1ꢀb][1,4]oxazine] (7), which is the starting compound for the
synthesis of bifunctional compounds, was obtained according to
an earlier described procedure.31
8´ꢀ(2ꢀHydroxybenzylideneimino)ꢀ1,3,3ꢀtrimethylꢀ1,3ꢀdihydroꢀ
spiro[2Hꢀindoleꢀ2,3´ꢀ[3H]naphtho[2,1ꢀb][1,4]oxazine] (1).
A solution of compound 7 (0.373 g, 1.0 mmol) and salicylꢀ
aldehyde (0.12 g, 1.0 mmol) in a mixture of toluene (30 mL) and
ethanol (20 mL) was refluxed for 2 h with the Dean—Stark
receiver slowly distilling off ~40 mL of the solvent. Then toluene
(20 mL) was added, and ~20 mL of the solvent was distilled off
during 1 h. The residue was evaporated on a rotary evaporator
3
NMe); 6.60 (d, 1 H, H(7), J6,7 = 7.8 Hz); 6.92 (dd, 1 H,
3
3
H(5), J4,5 = 7.1 Hz, J5,6 = 7.4 Hz); 7.09 (d, 1 H, H(5´),
3J5´,6´ = 8.9 Hz); 7.10 (d, 1 H, H(4), 3J4,5 = 7.1 Hz); 7.24 (dd,
1 H, H(6), J5,6 = 7.4 Hz, J6,7 = 7.8 Hz); 7.36 (d, 1 H, H(6″),
4J4 ,6″ = 2.4 Hz); 7.47 (d, 1 H, H(4″), 4J ″ = 2.4 Hz); 7.60 (dd,
3
3
″
″
4 ,6
3
4
1 H, H(9´), J9´,10´ = 9.0 Hz, J7´,9´ = 1.8 Hz); 7.67 (d, 1 H,
4
3
H(7´), J7´,9´ = 1.8 Hz); 7.70 (d, 1 H, H(6´), J5´,6´ = 8.9 Hz);
3
7.78 (s, 1 H, H(2´)); 8.63 (d, 1 H, H(10´), J9´,10´ = 9.0 Hz);
8.73 (s, 1 H, H(7″)); 14.0 (br.s, 1 H, OH).
8´ꢀ(5ꢀBromoꢀ2ꢀhydroxybenzylideneimino)ꢀ1,3,3ꢀtrimethylꢀ
1,3ꢀdihydrospiro[2Hꢀindoleꢀ2,3´ꢀ[3H]naphtho[2,1ꢀb][1,4]ꢀ
oxazine] (3). A solution of compound 7 (0.114 g, 0.33 mmol)
and 5ꢀbromosalicylaldehyde (0.067 g, 0.33 mmol) in a mixture

2400
Russ.Chem.Bull., Int.Ed., Vol. 57, No. 11, November, 2008
Zaichenko et al.
3
of toluene (20 mL) and ethanol (10 mL) was refluxed for 2 h
with the Dean—Stark receiver slowly distilling ~20 mL of the
solvent. Then toluene (20 mL) was added, and ~20 mL of
the solvent was distilled off for 2 h. The residue was evaporated
on a rotary evaporator and purified by chromatography on a
column packed with silica gel (45—70 μm (Aldrich), benzene
with the gradual addition of 0.5, 1, 2, 5, and 10% acetone as
eluent). The fractions containing the yellowꢀorange Schiff base
were collected, evaporated on a rotary evaporator, and crystalꢀ
lized from a benzene—hexane (3 : 1) mixture. Yellowꢀorange
crystals with m.p. 210—215 °C were obtained (0.06 g, 35%), Rf
0.67 (chloroform—acetone, 19 : 1). Found (%): C, 66.41; H,
4.92; N, 7.49. C29H24BrN3O2. Calculated (%): C, 66.17; H,
4.60; N, 7.98. 1H NMR (CDCl3), δ: 1.37, 1.38 (both s, 3 H each,
CMe2); 2.78 (s, 3 H, NMe); 6.59 (d, 1 H, H(7), 3J6,7 = 7.7 Hz);
4J4 ,6 = 2.8 Hz); 7.83 (dd, 1 H, H(4″), J3 ,4 = 9.0 Hz,
″
″
″ ″
4J4 ,6″ = 2.8 Hz); 14.0 (s, 1 H, OH).
″ 8´ꢀ(3ꢀBromoꢀ2ꢀhydroxyꢀ5ꢀnitrobenzylideneimino)ꢀ1,3,3ꢀ
trimethylꢀ1,3ꢀdihydrospiro[2Hꢀindoleꢀ2,3´ꢀ[3H]naphthoꢀ
[2,1ꢀb][1,4]oxazine] (5). A solution of compound 7 (0.12 g,
0.35 mmol) and 3ꢀbromoꢀ5ꢀnitrosalicylaldehyde (0.09 g,
0.37 mmol) in a mixture of toluene (15 mL) and ethanol
(15 mL) was refluxed for 2 h slowing distilling off 20 mL of the
solvent with the Dean—Stark receiver. Then toluene (20 mL)
was added, and the solvent was again distilled off slowly for 2 h.
After the solvent was completely removed on a rotary evaporator,
the precipitate was refluxed in benzene and filtered off. Comꢀ
pound 5 (0.11 g, 55%) was obtained as a brickꢀred powder with
m.p. 247—248 °C, Rf 0.79 (chloroform—acetone (18 : 1) mixture).
Found (%): C, 59.07; H, 4.00; N, 9.34. C29H23BrN4O4•H2O.
Calculated (%): C, 59.09; H, 4.28; N, 9.58. 1H NMR (CDCl3),
δ: 1.37, 1.39 (both s, 3 H each, CMe2); 2.78 (s, 3 H, NMe); 6.60
(d, 1 H, H(7), 3J6,7 = 7.7 Hz); 6.93 (dd, 1 H, H(5), 3J4,5 = 7.1 Hz,
3J5,6 = 7.7 Hz); 7.10 (d, 1 H, H(4), 3J4,5 = 7.1 Hz); 7.11 (d, 1 H,
H(5´), 3J5´,6´ = 8.9 Hz); 7.24 (t, 1 H, H(6), 3J5,6 = 3J6,7 = 7.7 Hz);
7.65 (dd, 1 H, H(9´), 3J9´,10´ = 9.0 Hz, 4J7´,9´ = 2.0 Hz); 7.72 (d,
1 H, H(6´), 3J5´,6´ = 8.9 Hz); 7.76 (d, 1 H, H(7´), 4J7´,9´ = 2.0 Hz);
3
3
6.91 (t, 1 H, H(5), J4,5 = J5,6 = 7.3 Hz); 6.95 (d, 1 H, H(5´),
3J5´,6´ = 8.8 Hz); 7.06 (d, 1 H, H(6´), 3J5´,6´ = 8.8 Hz); 7.10 (dd,
3
4
1 H, H(4), J4,5 = 7.3 Hz, J4,6 = 1.2 Hz); 7.22 (td, 1 H, H(6),
3J5,6
=
3J6,7 = 7.3 Hz, J4,6 = 1.2 Hz); 7.45 (dd, 1 H, H(4″),
4
3J ″ = 8.9 Hz, 4J ″ = 2.5 Hz); 7.56 (d, 1 H, H(6″), 4J ″ = 2.5 Hz);
″
″
″
7.359,4(dd, 1 H, H(9´), 3J9´,10´ = 8.0 Hz, 4J7´,9´ = 2.04H,6z); 7.64 (d,
4 ,6
1 H, H(7´), 4J7´,9´ = 2.0 Hz); 7.69 (d, 1 H, H(3″), 3J ″ = 8.9 Hz);
″
7.78 (s, 1 H, H(2´)); 8.62 (d, 1 H, H(10´), J9´,130,´4 = 8.0 Hz);
7.79 (s, 1 H, H(2´)); 8.40 (d, 1 H, H(4″), J4 ,6 = 2.6 Hz);
3
4
″
″
4
8.71 (s, 1 H, H(7″)); 14.2 (br.s, 1 H, OH).
8.59 (dd, 1 H, H(6″), J4 ,6 = 2.6 Hz); 8.69 (d, 1 H, H(10´),
8´ꢀ(2ꢀHydroxyꢀ5ꢀnitrobenzylideneimino)ꢀ1,3,3ꢀtrimethylꢀ
1,3ꢀdihydrospiro[2Hꢀindoleꢀ2,3´ꢀ[3H]naphtho[2,1ꢀb][1,4]ꢀ
oxazine] (4). A solution of compound 7 (0.2 g, 0.58 mmol)
and 5ꢀnitrosalicylaldehyde (0.11 g, 0.66 mmol) in a mixture of
toluene (15 mL) and ethanol (15 mL) was refluxed for 2 h slowly
distilling off the solvent (20 mL) with the Dean—Stark receiver.
Then toluene (20 mL) was added, and the solvent was again
distilled off slowly for 2 h. After the solvent was completely
removed on a rotary evaporator, the precipitate was refluxed in
petroleum ether and then filtered off. The precipitate was
chromatographed on a column with silica gel (35—70 μm,
Aldrich), eluting first with benzene and then with a benzene—
acetone (100 : 1) mixture. Orange fractions with Rf 0.60
(chloroform—acetone (18 : 1) mixture) were collected, the eluent
was evaporated on a rotary evaporator, and the residue was
recrystallized from benzene and washed with petroleum ether.
Orange crystals with m.p. 236—238 °C were obtained (0.09 g,
30%). Found (%): C, 70.50; H, 4.95; N, 11.31. C29H24N4O4.
Calculated (%): C, 70.72; H, 4.91; N, 11.38. 1H NMR (CDCl3),
δ: 1.37, 1.38 (both s, 3 H each, CMe2); 2.79 (s, 3 H, NMe); 6.60 (d,
1 H, H(7), 3J6,7 = 7.7 Hz); 6.92 (t, 1 H, H(5), 3J4,5 = 3J5,6 = 7.3 Hz);
3J9´,10´ = 9.0 Hz); 8.85 (s,″1 ″H, H(7″)); 14.5 (br.s, 1 H, OH).
The authors are grateful to V. N. Voznesenskii for
recording NMR spectra and T. M. Andrianova for help
in synthesis of compounds 3 and 4.
This work was financially supported by the Presidium
of the Russian Academy of Sciences (Program No. 8)
and the Russian Foundation for Basic Research (Project
Nos 05ꢀ03ꢀ32197a, 05ꢀ03ꢀ32775a, and 07ꢀ03ꢀ00948a).
References
1. V. A. Barachevskii, Zh. Nauchn. Prikl. Fotografii [Journal of
Scientific and Applied Photography], 1998, 43, 79 (in Russian).
2. G. Berkovic, V. Krongauz, V. Weiss, Chem. Rev., 2000, 100,
1741.
3. M. Irie, Chem. Rev., 2000, 100, 1685.
4. M. Figoli, G. H. Mehl, Angew. Chem., Int. Ed., 2005, 44, 5048.
5. G. J. Brown, A. P. De Silva, S. Pagliari, Chem. Commun.,
2002, 2461.
6. S. Kobatake, M. Irie, Tetrahedron, 2003, 59, 8359.
7. B. Z. Chen, M. Z Wang, Q. F. Luo, H. Tian, Synth. Met.,
2003, 137, 985.
8. A. J. Myles, T. J. Wigglesworth, N. R. Branda, Adv. Mater.,
2003, 745.
9. K. Yagi, M. Irie, Chem. Lett., 2003, 32, 848.
10. A. I. Shienok, N. L. Zaichenko, L. S. Kol´tsova, V. S.
Marevtsev, Izv. Akad. Nauk, Ser. Khim., 2003, 2169 [Russ.
Chem. Bull., Int. Ed., 2003, 52, 2294].
11. A. K. Frolov, F. E. Gostev, I. V. Shelaev, A. I. Shienok,
N. L. Zaichenko, L. S. Kol´tsova, V. A. Barachevskii, O. M.
Sarkisov, Khim. Fiz. [Chemical Physics], 2007, 26, 1021 (in
Russian).
12. S. A. Antipin, A. N. Petrukhin, F. E. Gostev, V. S. Marevtsev,
A. A. Titov, V. A. Barachevskii, Yu. P. Strokach, O. M. Sarkisov,
Khim. Fiz. [Chemical Physics], 2002, 21, 10 (in Russian).
3
4
7.09 (dd, 1 H, H(4), J4,5 = 7.4 Hz, J4,6 = 1.1 Hz); 7.10
(d, 1 H, H(5´)); 7.11 (m, 1 H, H(3″)); 7.24 (ddd, 1 H, H(6),
3
4
3J5,6 = 7.3 Hz, J6,7 = 7.7 Hz, J4,6 = 1.1 Hz); 7.63 (dd, 1 H,
3
4
H(9´), J9´,10´ = 8.7 Hz, J7´,9´ = 2.0 Hz); 7.70 (d, 1 H, H(7´),
4J7´,9´ = 2.0 Hz); 7.71 (d, 1 H, H(6´)); 7.79 (s, 1 H, H(2´)); 8.28
(dd, 1 H, H(4″), 3J3 ,4″ = 8.9 Hz, 4J ″ = 1.9 Hz); 8.44 (d, 1 H,
″
″
4 ,6
H(6″), 4J4 ,6″ = 1.9 Hz); 8.65 (d, 1 H, H(10´)), 3J9´,10´ = 8.7 Hz);
″
8.88 (s, 1 H, H(7″)); 14.7 (br.s, 1 H, OH). 1H NMR (tolueneꢀd8)
δ: 1.10, 1.24 (both s, 3 H each, CMe2); 2.47 (s, 3 H, NMe); 6.32
(d, 1 H, H(7), 3J6,7 = 7.8); 6.68 (d, 1 H, H(3″), 3J3 ,4″ = 9.0 Hz);
″
3
6.77 (d, 1 H, H(5´), J5´,6´ = 8.8 Hz); 6.84 (m, 1 H, H(5),
3J5,6 = 7.3 Hz); 6.86 (m, 1 H, H(4)); 6.99 (d, 1 H, H(7´),
4J7´,9´ = 2.2 Hz); 7.10 (ddd, 1 H, H(6), 3J5,6 = 6.7 Hz, 3J6,7 = 7.8 Hz,
4J4,6 = 2.0 Hz); 7.21 (dd, 1 H, H(9´), J9´,10´ = 8.8 Hz,
3
4J7´,9´ = 2.2 Hz); 7.30 (d, 1 H, H(6´), J5´,6´ = 8.8 Hz); 7.63
3
(s, 1 H, H(2)); 7.71 (s, 1 H, H(7″)); 7.80 (d, 1 H, H(6″),

Photochemically bifunctional compounds
Russ.Chem.Bull., Int.Ed., Vol. 57, No. 11, November, 2008 2401
13. R. S. Becker, W. F. Richey, J. Am. Chem. Soc., 1967, 89,
1298.
24. F. Bayrakceken, P. C. Sevinc, Spectrochim. Acta A: Mol.
Biomol. Spectrosc., 2007, 66, 184.
14. M. Z. Zgierski, A. Grabowska, J. Chem. Phys., 2000, 112,
6329.
25. G. O. Dudek, E. P. Dudek, J. Am. Chem. Soc., 1966, 88,
2407.
15. W. V. F. Fabian, L. Antonov, D. Nedeltcheva, F. S.
Kamounah, P. J. Taylor, J. Phys. Chem. A, 2004, 108, 7603.
16. M. Ziotek, J. Kubicki, R. Naskrecki, A. Grabowska, J. Chem.
Phys., 2006, 124, 124518.
17. P. Fita, E. Lusina, Cz. Radzewicz, A. Grabowska, J. Chem.
Phys., 2006, 125, 184508.
18. F. E Gostev, A. N. Petrukhin, A. A. Titov, V. A. Nadtochenko,
O. M. Sarkisov, A. V. Metelitsa, V. I. Minkin, Khim. Fiz.
[Chemical Physics], 2004, 23, 3 (in Russian).
19. Tables of Spectral Data for Structure Determination of Organic
Compounds, Ed. W. Fresenius, J. F. K. Huber, E. Pungor,
G. A. Rechnitz, W. Simon, Th. S. West, SpringerꢀVerlag,
Berlin—Heidelberg—New York—London—Paris—Tokio—
Hong Kong, 1989, 426 pp.
20. V. Lokshin, A. Sama, A. V. Metelitsa, Usp. Khim., 2002, 71,
1015 [Russ. Chem. Rev., 2002, 71 (Engl. Transl.)].
21. V. Vargas C., J. Phys. Chem. A, 2004, 108, 281.
22. J. S. Stephan, A. Mordzinski, C. Rios Rodriguez, K. H.
Grellmann, Chem. Phys. Lett., 1994, 229, 541.
23. A. Grabowska, K. Kownacki, J. Karpiuk, S. Dobrin,
L. Kaczmarek, Chem. Phys. Lett., 1997, 267, 132.
26. R. N. Christie, C. K. Agyako, K. Mitchell, Dyes and Pigments,
1995, 29, 241.
27. P. P. Levin, N. B. Sul´timova, O. N. Chaikovskaya, Izv.
Akad. Nauk, Ser. Khim., 2005, 1391 [Russ. Chem. Bull., Int.
Ed., 2005, 54, 1433].
28. N. B. Sul´timova, P. P. Levin, O. N. Chaikovskaya, Izv.
Akad. Nauk, Ser. Khim., 2005, 1397 [Russ. Chem. Bull., Int.
Ed., 2005, 54, 1439].
29. A. S. Tatikolov, S. M. B. Costa, J. Photochem. Photobiol. A:
Chem., 2001, 140, 147.
30. J.ꢀL. Pozzo, A. Samat, R. Guglielmetti, D. De Keukeleire,
J. Chem. Soc., Perkin Trans. 2, 1993, 1327.
31. V. Yu. Nedoshivin, N. L. Zaichenko, N. N. Glagolev, V. S.
Marevtsev, Izv. Akad. Nauk, Ser. Khim., 1996, 1243 [Russ.
Chem. Bull., 1996, 45, 1182 (Engl. Transl.)].
Received February 12, 2008;
in revised form May 21, 2008