Preparation, photochromism, and complex formation with metal ions of pyrazolylazomethine derivative of spirooxazine

Article abstract of DOI:10.1134/S1070363214050259

New hybrid spirooxazine has been prepared, based on amino-substituted spironaphthoxazine and pyrazolone. Photochromism and photoinduced complex formation with metal ions of the prepared compound has been studied. The effects of solvent polarity and the me

Full text of DOI:10.1134/S1070363214050259

ISSN 1070-3632, Russian Journal of General Chemistry, 2014, Vol. 84, No. 5, pp. 934–938. © Pleiades Publishing, Ltd., 2014.
Original Russian Text © L.D. Popov, N.L. Zaichenko, O.V. Venidiktova, T.M. Valova, V.A. Barachevskii, A.I. Shienok, L.S. Kol’tsova, S.I. Levchenkov,
V.A. Kogan, 2014, published in Zhurnal Obshchei Khimii, 2014, Vol. 84, No. 5, pp. 843–847.
Preparation, Photochromism, and Complex Formation
with Metal Ions of Pyrazolylazomethine Derivative
of Spirooxazine
L. D. Popova, N. L. Zaichenkob, O. V. Venidiktovac, T. M. Valovac, V. A. Barachevskiic,
A. I. Shienokb, L. S. Kol’tsovab, S. I. Levchenkovd, and V. A. Kogana
a Southern Federal University, ul. Zorge 7, Rostov-on-Don, 344090 Russia
e-mail: ldpopov@mail.ru
b Semenov Institute of Chemical Physics, Russian Academy of Sciences, Moscow, Russia
c Center of Photochemistry, Russian Academy of Sciences, Moscow, Russia
d Southern Scientific Center, Russian Academy of Sciences, Rostov-on-Don, Russia
Received July 29, 2013
Abstract—New hybrid spirooxazine has been prepared, based on amino-substituted spironaphthoxazine and
pyrazolone. Photochromism and photoinduced complex formation with metal ions of the prepared compound
has been studied. The effects of solvent polarity and the metal ion nature on the spirooxazine photochromism
and the complex formation ability have been elucidated.
Keywords: spirooxazine, photochromism, complex formation, UV spectroscopy
DOI: 10.1134/S1070363214050259
Requirements for new functional photochromic system
determine the recently emerged interest to hybrid
photochromic compounds [1–4]. Previously we re-
ported on preparation and properties of spirooxazine
derivatives containing salicylidenimine [5], 2-tosyl-
aminobenzylidenimine [6], and azobenzenesalicyl-
idenimine [7] fragments. We have demonstrated that
complex formation of metal ions with the merocyanine
form increases lifetime of the latter, and the complex
formation efficiency is affected by electrostatic
properties of the metal cation, in the cases of both the
initial and the merocyanine form [5]. Extending these
studies, herein we report on preparation and properties
(photochromism and complex formation) of the
pyrazolylmethine derivative of spirooxazine, prepared
for the first time.
Compound I was prepared via condensation of 4-
formyl-5-hydroxy-3-methyl-1-phenyl-1Н-pyrazole with
8'-amino-1,3,3-trimethylspiro (2H-indole-2,3'-3Н-na-
phtho[2,1-b][1,4]oxazine) [8] (Scheme 1).
1
Structure of compound I was elucidated from Н
NMR data. Namely, molecules of I in СDCl3 existed
in the form of spirocyclic compound with hydroxy-
azomethine fragment in the enol form.
Photoinduced changes of absorption spectrum of
compound I in the low-polar toluene are illustrated by
Fig. 1 and described in Table 1.
Scheme 1.
Me
HO
Me
Me
O
4
7
N
N
10'
6'
9'
N
5
6
2''
N
3''
4''
N
7'
6''
5'
Me
5''
I
934

PREPARATION, PHOTOCHROMISM, AND COMPLEX FORMATION
935
D
D
t, s
λ, nm
Fig. 2. Kinetic curves of coloration under UV irradiation
through the UFS-1 filter and of spontaneous dark relaxation
of compound I in toluene. Absorbance at 625 nm was
monitored.
Fig. 1. Absorption spectra of solutions of compound I in
toluene: initial state (1) under UV irradiation through the
UFS-1 filter (2).
From the collected data it is to be seen that,
similarly to the majority of spirooxazines, UV spec-
trum of compound I in toluene revealed absorption
bands at 325 and 363 nm (Fig. 1, curve 1). Upon UV
irradiation, intensity of those bands went down, and a
new absorption band appeared in the visible spectral
range, at 625 nm (Fig. 1, curve 2).
When the polar solvent (acetonitrile) was used
instead of the low-polar toluene, no significant changes
in the absorption spectra of the cyclic (A) and the
merocyanine (B) forms of the compound I were
revealed (Table 1); the sensitivity towards irradiation
was the same as well (the irradiation sensitivity could
be estimated, for instance, as ratio of the photoinduced
absorbance change at the merocyanine absorption
maximum to absorbance of the cyclic form at the long-
wave maximum, (∆DBmax/DАmax). However, in the polar
solvent, spontaneous discoloration of the merocyanine
form was faster, and the stability of compound I with
respect to the irreversible photoinduced transformation
was enhanced (Scheme 2).
The compound I color change upon UV irradiation
was reversible (Fig. 2). However, the repeated irradia-
tion cycles led to decrease of the photoinduced absorp-
tion amplitude, thus pointing at steady degradation of
the photochromic properties.
Such photochromism is typical of spirooxazines [5].
Table 1. Spectral and kinetic parameters of photochromic transformations of the hybrid spirooxazine Ia
Растворитель
λАmax, nm
εА, L mol–1 cm–1
λBmax, nm
∆DBmax/DАmax
kdd, s–1
t0.5, s
Toluene
325
363
245
322
363
27000
31250
20200
14000
16000
625
0.2
0.58
25
Acetonitrile
625
0.2
1.16
59
a
λАmax and λBmax, maximum of absorption bands of the initial cyclic form and of the photoinduced merocyanine form, respectively; ε, molar
absorptivity of the initial cyclic isomer; DАmax and ∆DBmax, absorbance at the maximum of the absorption band of the initial cyclic form
and the photoinduced change of absorbance at maximum of the absorption band of the merocyanine form, respectively; kdd, rate constant
of dark discoloration of the photoinduced merocyanine form at 25ºС; t0.5, time of two-fold irreversible decrease of DBmax under irradiation
with non-filtered light.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 84 No. 5 2014

936
POPOV et al.
Scheme 2.
R
Me
Me
O
Me
Me
N
N
hν1
R
hν2, kT
N
N
O
Me
Me
A
B
Kinetic study of the photoinduced complex
formation of I with metal ions by means of spectro-
photometry (Table 2 and Fig. 3) demonstrated that in
the cases of some ions the complex formation was
accompanied with red shift of absorption band of the
photoinduced merocyanine form.
I to UV irradiation (Table 2), its stability with respect
to irreversible photoinduced changes being enhanced
as well. Hence, magnesium ions likely formed the
complex with the merocyanine form of compound I.
Addition of Zn2+ to the solution slowed down the
dark discoloration of the merocyanine form; at the
same time, red shift of its absorption band (by 8 nm)
was observed (Fig. 2 and Table 2). The more efficient
complex formation led to the enhanced photoinduced
degradation (Table 2).
The almost equal rate constants of the dark
discoloration and the close characteristic times of
photodegradation of compound I in acetonitrile
without any ions and in the presence of Sr2+ (Tables 1
and 2) demonstrated that Sr2+ did not form complex
with compound I.
The most efficient interaction was observed
between compound I and Tb3+ ions, being reflected in
the more significant red shift of the merocyanine form
absorption (by 20 nm) as well as sharply slowing down
Addition of Mg2+ to the solution slowed down the
dark discoloration, enhancing sensitivity of compound
Table 2. Spectral and kinetic parameters of photochromic transformations of the hybrid spirooxazine I in acetonitrile in the
presence of metal ions
Cation
Sr2+
λАmax, nm
λBmax, nm
∆DBmax/DАmax
kdd, s–1
t0.5, s
244
322
364
242
320
364
359
625
0.2
1.25
51
Mg2+
625
0.6
0.22
73
Zn2+
Tb3+
617
605
0.6
0.6
0.32
0.04
33
1
320
363
362
Ni2+
540
587
619
0.3
0.04
–
21
68
Cu2+
326
462
~620
<0.005
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 84 No. 5 2014

PREPARATION, PHOTOCHROMISM, AND COMPLEX FORMATION
937
Ifl, r.u.
D
D
λ, nm
λ, nm
Fig. 3. Absorbance spectra of the solution of the photo-
induced form of the hybrid spirooxazine I in toluene
without metal ions (1) and in the presence of salt: magne-
sium perchlorate (2), strontium perchlorate (3), terbium
nitrate (4), zinc chloride (5), and nickel perchlorate (6).
Fig. 4. Absorbance spectra (1, 2) and fluorescence (excita-
tion at 465 nm) spectra (3, 4) of solutions of the hybrid
spirooxazine I in acetonitrile in the presence of Cu2+ ions
before (1, 3) and after (2, 4) UV irradiation.
of its dark discoloration (Table 2). Such a strong
interaction accelerated the photoinduced degradation
of compound I (Table 2).
Addition of Ni2+ to the solution led to red shift of
the photoinduced form absorption, decrease of rate
constant of its dark discoloration, and enhancement of
the photoinduced degradation efficiency. On top of
that, new bands appeared in the photoinduced
absorption spectrum, at 587 and 540 nm.
various metal ions can be explained by the complex
formation via the two complexing sites: phenolic
oxygen of the photoinduced merocyanine form and
pyrazolylazomethine fragment.
D/D0max
In contrast to the above-discussed complexes reveal-
ing certain photochromism, the colored complexes
with Cu2+ were formed immediately after the ions
addition to the solution (Fig. 4); in particular, new
absorption band appeared in the spectrum, at 465 nm.
The photochromic transformation efficiency was
simultaneously decreased. However, UV irradiation
significantly enhanced the fluorescence excited by
light with wavelength corresponding to the new com-
plex absorption band.
Figure 5 displays the normalized kinetic curves of
photoinduced degradation of compound I in its
individual solutions and in the presence of metal ions.
t, s
Fig. 5. Normalized kinetic curves of photoinduced
degradation of spirooxazine I in toluene (1), in acetonitrile
(2); in acetonitrile in the presence of salts: magnesium
perchlorate (3), strontium perchlorate (4), terbium nitrate
(5), nickel perchlorate (6), and zinc chloride (7) under
irradiation with non-filtered light. The absorbance was
followed at 605 nm (5), 620 nm (6), or in the absorption
maximum of the merocyanine form (1–4, 7).
From Fig. 5 and Table 1 it is to be seen that pure
compound I in acetonitrile and its complex with Mg2+
were the most stable with respect to irreversible changes.
The observed difference in the spectral and kinetic
properties of compound I and its complexes with
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938
POPOV et al.
To conclude, the prepared hybrid compound I
filtered off and washed with hot ethanol. Yield 0.4 g
revealed photochromic properties typical of spiro-
oxazines. Its spectral and kinetic properties were
sensitive to the solvent nature as well as to the
introduced metal ions, making it promising for
determination of metal ions in their solutions.
(76%), mp 269–271°C, Rf 0.67 (chloroform–acetone
9 : 1). H NMR spectrum (400 MHz, CDCl3), δ, ppm
1
(J, Hz): 1.36 s [3H, С(СН3)2], 1.37 s [3Н, С(СН3)2],
2.38 s (3Н, СН3), 2.78 s (3Н, NCH3), 6.60 d (1H, H7, J
7.4), 6.92 t (1H, H5, J 7.3), 7.05 d (1H, H6', J 9.1), 7.08
d (1H, H4, J 7.4), 7.18 t (1H, H6, J 7.4), 7.24 m (1H,
H4''), 7.43 t (2H, H3'', Н5'', J 7.9), 7.49 d.d (1H, H9', J1
9.0, J2 2.0), 7.55 d (1H, H7', J 2.0), 7.64 d (1H, H5', J
9.1), 7.78 s (1H, CН=N), 8.03 d (2H, H2'', H6'', J 8.0),
8.08 s (1H, CН=N), 8.63 d (1H, H10', J 9.2), 11.77 br.s
(1H, OH). Found, %: C 75.04; H 5.60; N 13.06.
C33H29N5O2. Calculated, %: C 75.12; H 5.54; N 13.27.
EXPERIMENTAL
Acetonitrile (99.9%) and toluene (99.8%) (Aldrich)
were used as solvents. 1,3-Dihydro-8'-amino-1,3,3-
trimethylspiro {2H-indlole-2,3'-(3H)-naphtho[2,1-b]-
[1,4]oxazine} was prepared as described elsewhere [4].
The complex formation was studied in the presence
of the following salts: Mg(ClO4)2, Sr(ClO4)2, Ni(ClO4)2,
and Tb(NO3)3 (ratio of I to the metal ion of 1 : 200) as
well as Cu(NO3)2 and ZnCl2 (1 : 20).
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