Synthesis, photochromism, and complex-forming ability of ρ-tosylaminobenzylideneaminospironaphthooxazine

Article abstract of DOI:10.1007/s11172-009-0126-z

New hybrid spirooxazine was synthesized from the 8′-amino-substituted spironaphtho-oxazine and 2-(ρ-tosylamino)benzaldehyde. Photochromism and the complex-forming ability toward Mg2+, Ba2+, La3+, and Tb3+ ions of the synthesized compound and initial 8′-amino- spironaphthooxazine were studied in comparison. The spectral kinetic differences in the photochromism and complex formation of these compounds were revealed.

Full text of DOI:10.1007/s11172-009-0126-z

Russian Chemical Bulletin, International Edition, Vol. 58, No. 5, pp. 974—977, May, 2009
974
Synthesis, photochromism, and complexꢀforming ability
of pꢀtosylaminobenzylideneaminospironaphthooxazine
L. D. Popov,a I. N. Shcherbakov,a V. A. Kogan,a O. I. Kobeleva,b T. M. Valova,b
V. A. Barachevsky,b A. I. Shienok,c L. S. Kol´tsova,c O. Yu. Os´kina,c and N. L. Zaichenkoc
aSouthern Federal University,
105 ul. B. Sadovaya, 344104 RostovꢀonꢀDon, Russian Federation.
Eꢀmail: shcherbakov@rsu.ru
bPhotochemistry Center, Russian Academy of Sciences,
7a ul. Novatorov, 119421 Moscow, Russian Federation.
Eꢀmail: barva@photonics.ru
cN. N. Semenov Institute of Chemical Physics, Russian Academy of Sciences,
4 ul. Kosygina, 119991 Moscow, Russian Federation.
Eꢀmail: zaina@polymer.chph.ras.ru
New hybrid spirooxazine was synthesized from the 8´ꢀaminoꢀsubstituted spironaphthoꢀ
oxazine and 2ꢀ(pꢀtosylamino)benzaldehyde. Photochromism and the complexꢀforming ability
toward Mg2+, Ba2+, La3+, and Tb3+ ions of the synthesized compound and initial 8´ꢀaminoꢀ
spironaphthooxazine were studied in comparison. The spectral kinetic differences in the
photochromism and complex formation of these compounds were revealed.
Key words: photochromism, spirooxazine, azomethine, absorption spectra, kinetics of
phototransformations, complex formation with metal ions.
Interest in studying hybrid photochromic compounds
The present work is devoted to the comparative specꢀ
has increased in the recent years due to the search for
ways of extension of functional potentialities of photoꢀ
chromic systems.
tral kinetic study of the photochromism and complexꢀ
forming ability toward selected metal ions of 8´ꢀaminoꢀ
Scheme 1
We have previously1—4 synthesized the spironaphthoꢀ
oxazine derivatives containing the salicylideneamine fragꢀ
ment capable of the photoinduced intramolecular proton
transfer in the excited state and complex formation. The
complex formation of the photoinduced merocyanine
form of this compound was shown to increase the lifetime
of this form, and the efficiency of complex formation of
both the initial and merocyanine forms of this compound
depends on the electrostatic properties of the metal cations.4
The intramolecular processes were studied by femtosecond
laser spectroscopy.5 It was found that photon absorption
results in two independent photochemical processes:
intramolecular proton transfer in the excited state in the
salicylidene fragment with the formation of the keto
tautomer and photochromic transformations including
С
spiro—О bond photodissociation in the oxazine fragment
of the spiropyran system followed by the thermal formaꢀ
tion of the colored transꢀisomer of the merocyanine form.
The coherent effects were also found, and a possibility of
coherent control of the yield of photoreaction products
by the change in the phase modulation of the exciting
pulse was demonstrated.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 950—953, May, 2009.
1066ꢀ5285/09/5805ꢀ0974 © 2009 Springer Science+Business Media, Inc.

Novel hybrid spironaphthooxazine
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009
975
Table 1. Spectral kinetic characteristics of the photochromic
transformations of spironaphthooxazines 1 and 3
substituted spironaphthooxazine 1 and Schiff base 3, which
was synthesized for the first time from compound 1 and
2ꢀ(pꢀtosylamino)benzaldehyde (2) (Scheme 1).
Aminoꢀsubstituted spironaphthooxazine 1 was syntheꢀ
sized using a known procedure,6 and 2ꢀ(pꢀtosylamino)ꢀ
benzaldehyde (2) was synthesized by a described proceꢀ
dure.7 The structure of compound 3 was determined by
IR spectroscopy, NMR spectroscopy, and elemental
analysis (see Experimental).
We recorded the absorption spectra of the initial and
photoinduced forms of compounds 1 and 3 in toluene
and acetonitrile (Table 1, Figs 1 and 2). It was found that
the both compounds manifest the photochromic properꢀ
ties, i.e., undergo the photochromic transformations beꢀ
tween the initial spiropyran (A) and photoinduced meroꢀ
cyanine (B) forms (Scheme 2).
max
max
phd
Solvent Metal
ion
λ
λ
B
ΔDph kddc T0.5
A
/s–1
/s
nm
Spironaphthooxazine 1
Toluene
MeCN
MeCN
MeCN
MeCN
—
—
Mg2+
La3+
Tb3+
328, 390
325, 390
615
625
640
625
625
0.8
0.850
73.5
0.25 1.400 614
—
—
—
—
—
—
—
—
—
—
—
—
Spironaphthooxazine 3
Toluene
MeCN
MeCN
MeCN
MeCN
MeCN
—
—
324, 390
318, 390
590
623
622
620
615
605
0.1
0.5
0.7
0.9
1.2
1.2
0.620 510
1.570 151
0.650 176
0.300 160
Ва2+ 318, 390
Mg2+ 318, 390
La3+ 316, 390
Tb3+ 316, 390
0.018
0.003
53.3
36.4
Scheme 2
max
max
Note: λ
and λ
are the wavelengths of the absorption
band mAaxima of the initial (А) and photoinduced (В) forms;
ΔDph is the photoinduced change in the absorbance at the
absorption band maximum of the form B in the equilibrium
state; kddc is the rate constant of spontaneous decoloration of
the form В measured by the change in the absorbance in the
dark at the maximum of the absorption band of the form B at
25 °С; T0.5phd is the time during which the photoinduced absorꢀ
bance at the absorption band maximum of the form B is halved
upon the irradiation with the nonfiltered light of an LCꢀ4 source
(Hamamatsu).
B
is due to the introduction of the 2ꢀtosylaminobenzylꢀ
ideneamine fragment into the molecule.
A comparison of the data presented in Table 1 shows
that the merocyanine form B of these compounds has
the quinoid character, because the absorption band of the
photoinduced merocyanine form exhibits the bathoꢀ
chromic shift upon the replacement of weakly polar
toluene by polar acetonitrile.8 Accordingly, the rate of
spontaneous decoloration in the dark increases. The
photoinduced absorbance at the absorption band maxiꢀ
mum of the merocyanine form shows that the efficiency
The absorption spectra of the initial form А of spiroꢀ
naphthooxazine 3 exhibit a sharp increase in the intensity
of the bands in the longꢀwavelength part of the spectrum
compared to the spectra of spironaphthooxazine 1, which
A
1.6
A
1.4
1.6
1.2
1.0
1.2
0.8
0.8
0.6
2
0.4
0.2
2
1
0.4
1
350
450
550
650
750 λ/nm
350
450
550
650
750 λ/nm
Fig. 1. Absorption spectra of a solution of compound 1 in MeCN
before (1) and after (2) irradiation with the light with λ = 365 nm.
Fig. 2. Absorption spectra of a solution of compound 3 in MeCN
before (1) and after (2) irradiation with the light with λ = 365 nm.

976
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009
Popov et al.
of photochromic transformations and photodegradation
of compound 1 in toluene is higher than that in acetoꢀ
nitrile. An inverse dependence is observed in the case of
spironaphthooxazine 3. However, in the both cases, the
higher the efficiency of the photodegradation, the higher
the photoinduced change in the absorbance. This fact and
the data of previous studies of photochromic spirooxazines9
suggest that the photoinduced merocyanine form is charꢀ
acterized by the most efficient photodecomposition.
The complex formation processes of compounds 1
and 3 with the Mg2+, Ba2+, La3+, and Tb3+ ions (see Table 1)
were compared. No changes were observed in the absorpꢀ
tion spectra of solutions of the initial form А after the
metal salts were added, indicating that almost no complex
formation occurs, unlike the earlier studied4 spironaphthoꢀ
oxazine containing the salicylideneamine fragment.
The photoinduced merocyanine form B of the studied
compounds participates in complex formation in different
manners. In the case of compound 1, at the low concenꢀ
tration of the photoinduced merocyanine form an insigꢀ
nificant bathochromic shift of the absorption band is
observed, which increases, however, to 650 nm with the
further UVꢀirradiation of a solution of spironaphthoꢀ
oxazine 1 in acetonitrile in the presence of the Tb3+ ions
(Fig. 3). This phenomenon can be explained by the formaꢀ
tion of a complex of the metal ion with the monomolecular
merocyanine form at small exposures to the UV light
followed by the aggregation of the merocyanine form.10
In the case of compound 3, the absorption band
maximum of the merocyanine form exhibits the hypsoꢀ
chromic shift, whose value depends on the metal nature
(see Table 1, Fig. 4).
The rate constant of dark decoloration decreases siꢀ
multaneously (see Table 1). The metal cation with a higher
electric charge density, in particular, Tb3+, induces a more
considerable hypsochromic shift of the absorption band
of the photoinduced merocyanine form and inhibition of
the thermal relaxation rate of the complexes of the
merocyanine form compared with the cations with the lower
charge density.
It should be mentioned that the metal ions affect the
photodegradation process in the case of compound 3.
The Mg2+ and Ba2+ ions favor an insignificant increase
in the stability of molecules 3 toward photodegradation,
in spite of the increase in the photoinduced absorbance at
the absorption band maximum of the photoinduced
merocyanine form. This possibly indicates that these ions
form complexes with molecules 3 and thus exert a positive
effect on the stability of the photochromic systems toward
irreversible photochemical transformations. The presence
of the La3+ and Tb3+ ions decreases the photostability
of compound 3. At the same time, these ions sharply
enhance the efficiency of photoaggregation of photochroꢀ
mic molecules. To reveal reasons for this phenomenon,
further we are planning to study in more detail the
complex formation processes of molecules 3 with the La3+
and Tb3+ ions.
A
1.4
1.0
0.6
0.2
Based on the data obtained, we can assume that the
chelate complex formation in the case of the Mg2+ and
Ba2+ ions occurs through the azomethinic N atom
and phenoxide O atom of the photoinduced merocyanine
form, decreasing the rate of dark cyclization to produce
the spiro form.
350
450
550
650
750 λ/nm
Fig. 3. Absorption spectra of a solution of compound 1 in MeCN
in the presence of the Tb3+ ions with an increase in the UV
radiation exposure.
A
3
0.6
2
0.4
0.2
Thus, the spectral kinetic study of synthesized spiroꢀ
naphthooxazine 3 showed that this compound has the
photochromic properties, which depend on the solvent
nature and the presence of metal ions. It was found for the
first time that, unlike solutions of the compounds conꢀ
taining no metal ions, the efficiency of photodegradation
is determined by the nature of ions present in the solution
rather than by the photoinduced absorbance value.
4
1
400
500
600
700 λ/nm
Fig. 4. Absorption spectra of a solution of compound 3 in MeCN
in the presence of Tb3+ before (1) and after the consecutive
UV irradiation (2, 3) and dark relaxation (4).

Novel hybrid spironaphthooxazine
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009
977
Experimental
This work was financially supported by the Southern
Federal University (Internal Development Grant) and
the Russian Foundation for Basic Research (Project
No. 08ꢀ03ꢀ00660).
Acetonitrile and toluene (Aldrich) were used as solvents.
Complex formation processes in solutions were studied in
the presence of the metal salts Mg(ClO4)2, Ba(ClO4)2, La(NO3)3,
and Tb(NO3)3 at the ligand to metal ratio 1 : 100.
The spectrophotometric study (photostationary spectra) of
the studied compounds in solutions was carried out using a Cary
50 bio spectrophotometer (Varian). The kinetics of thermal
decoloration and photodegradation, as well as the photoinduced
change in the absorbance, were recorded with a USB2000 fiberꢀ
optical spectrometer (Ocean Optics).
The working concentration in solutions was 2•10–4 mol L–1
A quartz cell 0.2 cm thick was used for measurements. Irraꢀ
diation was performed with the nonfiltered and filtered light
from DRShꢀ250 and LCꢀ4 lamps (Hamamatsu).
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.
1Н NMR spectra were recorded on a Varianꢀ300 instrument
(300 MHz) at 25 °С using DMSOꢀd6 as the solvent. IR spectra
of the substances in Nujol were measured on a Varian Scimitar
1000 spectrometer. Elemental analyses to C, N, and H were
carried out on a Perkin—Elmer 2400 automated CHNꢀanalyzer.
1,3,3ꢀTrimethylꢀ8´ꢀ[2ꢀ(pꢀtosylamino)benzylideneamino]ꢀ
1,3ꢀdihydrospiro[2Hꢀindoleꢀ2,3´ꢀ[3H]naphtho[2,1ꢀb][1,4]ꢀ
oxazine] (3). Aminospirooxazine 1 (343 mg, 1 mmol) in EtOH
(50 mL) was added to a hot solution of 2ꢀ(pꢀtosylamino)ꢀ
benzaldehyde7 2 (275 mg, 1 mmol) in EtOH (50 mL). The
resulting solution was refluxed for 4 h. A light green precipitate
formed 24 h after was filtered off, washed with EtOH, and
recrystallized from an EtOH—dioxane (2 : 1) mixture. The gray
crystalline substance was obtained in a yield of 370 mg (62%),
m.p. 217—219 °С. Found (%): С, 71.80; H, 5.10; N, 9.50.
C36H32N4O3S. Calculated (%): С, 71.98; H, 5.37; N, 9.33.
IR, ν/cm–1: 3366 (w, br, ν(N—H)), 1631 (m, ν(С=N), spiroꢀ
oxazine), 1605 (s, ν(С=С) arom.), 1595 (s, ν(С=N), azoꢀ
methine), 1571 (m), 1343 (s, ν(С—N)), 1270 (m, ν (S=O)),
1156 (vs, ν (S=O)), 1090 (s), 1082 (s), 1021 (s), 757 (sa)s, 658 (s),
s
563 (s). 1H NMR, δ: 1.33, 1.36 (both s, 3 H each, СMe2);
2.35 (s, 3 H, СMe); 2.77 (s, 3 H, NMe); 6.58 (d, 1 H, H(7),
3
3
3J6,7 = 7.44 Hz); 6.81 (t, 1 H, H(5), J5,6 = J4,5 = 7.1 Hz);
7.00—7.20 (m, 4 H); 7.25 (d, 2 H, H(8″), 3J7 ,8″ = 8.3 Hz); 7.38
(dd, 1 H, H(6), J6,7 = 7.44 Hz, J5,6 = 7.1 Hz); 7.52 (d, 1 H,
H(6´), J5´,6´ = 8.6 Hz); 7.60—7.86 (m, 7 H); 8.56 (d,
1 H, H(10´), J9´,10´ = 9.2 Hz); 8.88 (s, 1 H, CH=N); 12.77
″
3
3
3
3
Received June 25, 2008
(s, 1 H, NH).