Crown-containing spironaphthoxazines and spiropyrans. 2. Influence of metal cations on the photochromic properties of spironaphthoxazines linked with aza-15(18)-crown-5(6) ethers

Article abstract of DOI:10.1023/A:1015001527963

Spironaphthoxazines linked with aza-15(18)-crown-5(6) fragments were synthesized and studied for the first time. Addition of alkaline-earth cations to solutions of crown-containing spironaphthoxazines causes a hypsochromic shift of the absorption band of the spiro form and a bathochromic shift of the absorption band of the merocyanine form, shifts the equilibrium to the merocyanine form, and changes the lifetime of the photoexcited merocyanine form. The spectral and kinetic data were used to propose a mechanism of complexation and calculate the stability constants of the resulting complexes. The complexation involves the crown fragment and the merocyanine oxygen atom. The type of the complex is determined by the cation nature and size.

Full text of DOI:10.1023/A:1015001527963

58
Russian Chemical Bulletin, International Edition, Vol. 51, No. 1, pp. 58—66, January, 2002
Crownꢀcontaining spironaphthoxazines and spiropyrans.
2*. Influence of metal cations on the photochromic properties of
spironaphthoxazines linked with azaꢀ15(18)ꢀcrownꢀ5(6) ethers
a
a
a
a
Yu. P. Strokach,a O. A. Fedorova,a S. P. Gromov, A. V. Koshkin, T. M. Valova, V. A. Barachevsky,

M. V. Alfimov,a V. A. Lokshin,b A. Samat,b and R. Guglielmettib
aCenter of Photochemistry, N. N. Semenov United Institute of Chemical Physics, Russian Academy of Sciences,
7A ul. Novatorov, 117421 Moscow, Russian Federation.
Fax: +7 (095) 936 1255. Eꢀmail: fedorova@photonics.ru
bDepartment of Natural Sciences, Mediterranian University, Luminy,
UMR6114CNRS Marseille, France.**
Fax: +33 (91) 82 9301. Eꢀmail: samat@luminy.univꢀmrs.fr
Spironaphthoxazines linked with azaꢀ15(18)ꢀcrownꢀ5(6) fragments were synthesized and
studied for the first time. Addition of alkalineꢀearth cations to solutions of crownꢀcontaining
spironaphthoxazines causes a hypsochromic shift of the absorption band of the spiro form and a
bathochromic shift of the absorption band of the merocyanine form, shifts the equilibrium to the
merocyanine form, and changes the lifetime of the photoexcited merocyanine form. The spectral
and kinetic data were used to propose a mechanism of complexation and calculate the stability
constants of the resulting complexes. The complexation involves the crown fragment and the
merocyanine oxygen atom. The type of the complex is determined by the cation nature and size.
Key words: crownꢀcontaining spironaphthoxazines, synthesis, photochromic properties,
metal ions, complexation.
Photochromic compounds possess two or more stable
possible interaction of the O atom of the merocyanine
form with the metal cation located in the crown cavity.
When the length of the methylene bridge is optimum, the
merocyanine form of spironaphthoxazine is stabilized by
effective coordination of the merocyanine O atom to the
"crowned" metal cation.
To obtain spironaphthoxazine systems that would be
more sensitive to the presence of metal cations in solution
than the known analogs, we synthesized and studied for
the first time spironaphthoxazines with azacrown fragꢀ
ments (CSN). For comparison, spironaphthoxazine conꢀ
taining no crown fragment (SN) was also tested.
states; a transition between these states is followed by a
change in their spectral characteristics.2—4 An equilibꢀ
rium state in such systems can be changed either by irraꢀ
diation with UV or visible light or by changing the paramꢀ
eters of the surrounding medium. Photochromic comꢀ
pounds containing a complexꢀforming fragment can inꢀ
teract with metal ions, which occasionally changes the
spectral characteristics of the ligands.5—9 Such compounds
make it possible to detect, even visually, the presence of
metal ions in solutions and are of considerable interest for
creation of efficient ionophores for selective determinaꢀ
tion of the metal ions.
Earlier,10—13 photochromic ionophores with crown
ether fragments attached to the spironaphthoxazine frameꢀ
work in different positions through methylene bridges of
different lengths were synthesized and studied. It was
shown that the influence of metal ions on the spectral and
photochemical properties of these compounds is due to a
Results and Discussion
Synthesis. Crownꢀcontaining spironaphthoxazines
1a,b were synthesized as described earlier14 for 6´ꢀaminoꢀ
substituted spironaphthoxazines, which can be obtained by
condensation of 2ꢀmethylideneindolenine with 4ꢀaminoꢀ
substituted 1ꢀnitrosoꢀ2ꢀnaphthol. The latter compound
can be prepared either by nucleophilic substitution of a
secondary amine for the H(4) atom in 1ꢀnitrosoꢀ2ꢀnaphꢀ
thol or in two steps from sodium 1,2ꢀnaphthoquinoneꢀ4ꢀ
sulfonate.
* For Part 1, see Ref. 1.
** Université de la Méditerranée, Faculté des Sciences Naturelles
de Luminy, Case 901—163, Avenue de Luminy, Cedex 9,
UMR6114CNRS Marseille, France.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 56—64, January, 2002.
1066ꢀ5285/02/5101ꢀ58 $27.00 © 2002 Plenum Publishing Corporation

Spironaphthoxazines linked with azacrown ethers
Russ.Chem.Bull., Int.Ed., Vol. 51, No. 1, January, 2002
59
Scheme 1
We tried out both methods for the synthesis of CSNs
1a,b (Scheme 1). The reactions of 1ꢀnitrosoꢀ2ꢀnaphthol
with azaꢀ15(18)ꢀcrownꢀ5(6) ethers and the subsequent
reactions with indolenine were carried out in ethanol in
the presence of Et3N (method A). The yields of comꢀ
pounds 1a and 1b were low (5 and 3%, respectively); they
could not be increased by varying the reaction conditions
(reaction time and temperature and a ratio of the reꢀ
agents). The major product was nonsubstituted SN 2.
While following method B, we isolated a 1,2ꢀnaphꢀ
thoquinone derivative 3 at the first stage; however, the
proper conditions for its reaction with hydroxylamine to
give crownꢀcontaining 1ꢀnitrosoꢀ2ꢀnaphthol (4) were not
found.
ues of these parameters for unsubstituted SN 2 (Table 1).
A slight shift of the equilibrium to the MF indicates
that this form of the dye is stabilized by the azacrown
Scheme 2
Spectral and photochemical properties of CSNs 1a,b.
When irradiated with UV light, the original spiro form
(SF) of CSNs 1a,b, like the corresponding nonsubstituted
SN 2, reversibly isomerizes into colored merocyanine
forms (MF) which are able to return spontaneously to the
original state (Scheme 2).
Introduction of an azacrown fragment into position
6´ of the naphthalene ring (CSNs 1a,b) results in a
bathochromic shift of the absorption band of the spiro
form (∼13 nm) and in a hypsochromic shift of the absorpꢀ
tion band of the merocyanine form (∼28 nm), gives rise to
some absorption by the starting solutions in the visible
region, and causes a sixfold increase in the thermal relaxꢀ
ation constants of the colored form compared to the valꢀ
R =
(1a),
(1b); H (2)

60
Russ.Chem.Bull., Int.Ed., Vol. 51, No. 1, January, 2002
Strokach et al.
Table 1. Photochromic characteristics of spironaphthoxazines 1a,b and 2 and their complexes with alkali (Li+) and
alkalineꢀearth (Mg2+, Ca2+, Sr2+, and Ba2+) ions in MeCN
c
d
Comꢀ
pound
λ
a/nm
∆εSF•10–4 b
λ
a/nm
∆λ
/nm
∆ε b•10–4
kMF→SF
/s–1
SF
MF
MF
MF
(εSF•10–4
/L mol–1 cm–1
(εMF•10–4
/L mol–1 cm–1
/L mol–1 cm–1
)
/L mol–1 cm–1
)
1a
368 (1.17)
565 (∼0.02)
580
9.7
7.7
1a•Li+
1a•Mg2+
1a•Ca2+
1a•Sr2+
1a•Ba2+
1b
—
—
—
—
–0.07
–0.04
–0.21
–0.12
–0.09
—
15
40
20
17
10
—
12
41
30
27
25
—
0.01
0.40
0.08
0.03
0.01
—
0.01
0.09
0.036
0.020
0.012
—
605
585
582
575
1.20
1.19
3.35
5.12
9.4
—
368 (1.20)
565 (∼0.02)
587
1b•Li+
1b•Mg2+
1b•Ca2+
1b•Sr2+
1b•Ba2+
2
—
—
—
—
—
–
8.7
–0.01
–0.27
–0.60
–0.57
606
595
592
590
0.83
2.16
0.80
0.79
1.6
355 (0.56)
593
a
λ
SF(εSF) and λMF(εMF) are the positions (extinction coefficients) of the longꢀwavelength absorption bands of the
SF, the MF, and their complexes.
b
∆ε
= ε
(complex) – ε
(dye) is the change in the extinction coefficient of the SF (MF) upon
SF(MF)
SF(MF)
SF(MF)
complexation.
c
∆λMF = λMF (complex) – λMF (dye) is the shift of the absorption band of the MF upon complexation.
d kMF→SF is the thermal relaxation constant of the MF and its complexes (CL = 2•10–4 mol L–1, CM/CL = 100, 24
°C).
fragment somewhat better than the SF. The observed
changes in the spectral and kinetic parameters of CSNs
1a,b are due to the electronꢀdonor influence of the
azacrown substituent conjugated with the πꢀelectron sysꢀ
tem of the molecule. Analogous spectral changes were
noted earlier15 for 6´ꢀmorpholino(or ꢀpiperidino)spiroꢀ
naphthoxazines.
Spectral properties of complexes formed by CSNs 1a,b.
It is known3 that the SF and the MF of spironaphthoxazine
are in equilibrium in solution (see Scheme 2). The abꢀ
sorption spectra of solutions of CSNs 1a,b in the absence
of metal salts virtually do not contain bands of the MF
(see Table 1). This confirms that the groundꢀstate energy
levels of the SF and MF of 1a,b are so mutually arranged
that appreciable thermal population of the S0 state of the
merocyanine form is impossible.
Appearance of the absorption bands in the visible reꢀ
gion upon addition of alkalineꢀearth cations to solutions
of CSNs 1a,b in MeCN (see Table 1) suggests that the
complexation stabilizes the MFs of these compounds,
as well.
In the most general case, the thermodynamic equilibꢀ
rium in the system crownꢀcontaining spironaphthoxaꢀ
zine—metal cation in solutions can be represented by
Scheme 3.
Low concentrations of the MF of CSNs 1a,b obtained
after the Li+, Ba2+, Sr2+, or Ca2+ cation was added to
ε•10–4/L mol–1 cm–1
0.1
In the presence of alkali and alkalineꢀearth cations,
the spectral pattern for solutions of crownꢀfree SN 2 reꢀ
mains virtually unchanged. When the same metal salts are
added in the same concentration to solutions of CSNs
1a,b in MeCN, the absorption band of their spiro forms
experiences a hypsochromic shift to the UV region
(Fig. 1), while their merocyanine forms begin to absorb in
the visible region (Fig. 2). The shift of the band of the SF
is due to coordination of its crown fragment to the metal
ions. The resulting N...M coordination bond significantly
reduces the conjugation of the N atom with the chroꢀ
mophore system of the molecule, which shortens its chroꢀ
mophore chain and hence causes a hypsochromic shift of
the absorption band of the SF.
0
1
2
–0.1
3
4
5
6
7
8
–0.2
–0.3
300
350
400
450
λ/nm
Fig. 1. Absorption spectra of solutions of CSN 1a in MeCN in
the presence of Li(ClO4)2 for CM/CL = (1) 0.5, (2) 1, (3) 2, (4) 5,
(5) 10, (6) 20, (7) 50, and (8) 100.

Spironaphthoxazines linked with azacrown ethers
Russ.Chem.Bull., Int.Ed., Vol. 51, No. 1, January, 2002
61
ε•10–4/L mol–1 cm–1
Complexation constants for the SF of CSNs 1a,b were
calculated from the spectrophotometric data using the
following complexation model:
14
13
12
11
10
9
8
7
6
5
4
3
2
1
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
L + M
LM, KLM = [LM]/([L][M]),
(1)
where [L], [M], and [LM] are the concentrations of the
free ligand, the free metal ion, and the complex, respecꢀ
tively.
In this case, the dependence of the complexation deꢀ
gree (α) on the concentration of metal ions in solution is
determined by the equation16:
α = (A – A0)/(A∞ – A0) = (CL + CM +1/KLM) ×
× [1 – (1 – 4CLCM/(CL + CM + 1/KLM)2)1/2]/2CL,
(2)
300 350 400 450 500 550 600 650
λ/nm
Fig. 2. Absorption spectra of solutions of CSN 1a in MeCN in
the presence of Mg(ClO4)2 for CM/CL = (1) 0, (2) 0.5, (3) 1, (4)
2, (5) 5, (6) 10, (7) 20, (8) 50, (9) 100, (10) 200, (11) 500, (12)
1000, (13) 2000, and (14) 4000.
where A0, A, and A∞ are the optical absorption densities of
the solutions in the absence and in the presence of metal
cations with the concentration CM and with a concenꢀ
tration required for complete complexation, respecꢀ
tively; CL and CM are the concentrations of the ligand
and the metal cation; and KLM is the complexation
constant.
The theoretical dependences α(CM) in logα vs.
log(CM/CL) coordinates, which were calculated using
Eq. (2), are consistent with the titration data for solutions
of CSNs 1a,b (Fig. 3). This confirms the formation of
solutions enable one to ignore the cationꢀinduced formaꢀ
tion of the MF while studying the equilibrium in the
spironaphthoxazine—metal system. In this case, the
main equilibriumꢀdetermining process is the equilibrium
A
D between the starting form A and its complex D
(see Scheme 3).
Scheme 3

62
Russ.Chem.Bull., Int.Ed., Vol. 51, No. 1, January, 2002
Strokach et al.
∆D/∆D0
Table 2. Stability constants of the complexes of spiroꢀ
naphthoxazines 1a,b and 2 with alkali and alkalineꢀearth
cations in acetonitrile
1
Cationn+
d/Å
2
1a
1b
logKC logKD logKF logKD logKF
Li+
1.36
1.32
1.98
2.24
2.68
—
—
2.2
—
3.28
—
3.65
3.22
3.10
—
—
2.4
—
—
2.2
4.6
—
—
—
2.3
—
0.1
Mg2+
Ca2+
Sr2+
Ba2+
1
4
3
—
—
5.6
—
5
7
6
2
Note. The stability constants of the complexes were deterꢀ
mined with a measurement error of approximately 0.1.
0.1
1
10
100
CM/CL
Fig. 3. Effect of the concentration of (3) Ca2+, (4) Li+, (5) Sr2+
,
and (6) Ba2+ perchlorates in solutions of CSN 1a and of the
concentration of (1) Ba2+, (2) Ca2+, and (7) Mg2+ perchlorates
in solutions of CSN 1b in MeCN on the relative change in
absorption at 380 nm (the experimental and theoretical curves
are indicated by dotted and solid lines, respectively).
CSN 1a with Li+ (1.36 Å) and CSN 1b with Mg2+
are low since the diameters of these cations are too
small for efficient complexation with crown ethers of a
given size.
Unlike the complexation involving Li+, Ba2+, Sr2+
,
1 : 1 complexes of the SF with the Li+, Ba2+, Sr2+, and
Ca2+ cations.
The complexation constants obtained for the spiro
forms of CSNs 1a,b (KD) and Li+, Ca2+, Sr2+, and Ba2+
cations in acetonitrile17 and the cation diameters (d) necꢀ
essary for analysis of the experimental data are given in
Table 2.
The hypsochromic shifts upon complexation (see
Table 1) and the stability constants of the complexes of
CSN 1a with alkalineꢀearth cations (see Table 2) increase
(Ba2+ < Sr2+ < Ca2+) with a decrease in the cation radius;
this is probably due to the better fit of the Ca2+ size
(1.98 Å) to the azaꢀ15ꢀcrownꢀ5 cavity (1.7—2.2 Å).18 For
the same reason, complexes of CSN 1a with Ca2+ and
Ba2+ are substantially more stable than those of CSN 1b
(see Table 2). The stability constants of complexes of
and Ca2+ cations, the complexation between CSN 1a and
Mg2+ significantly shifts the equilibrium toward the colꢀ
ored form (see Fig. 2). In this case, UV spectral changes
are due to both the formation of the SF complexes and, to
a large extent, the absorption of the MF. These effects
cannot be separated, which makes it impossible to use the
aforesaid procedure for estimation of the complexation
constants for the spiro form of CSN 1a and Mg2+ cations.
Complexation of CSN 1a was also studied by NMR
spectroscopy. Addition of alkalineꢀearth perchlorates to a
solution of CSN 1a resulted in downfield shifts of signals
from protons (Table 3). Signals from the benzene protons
in the indoline part experience no substantial shifts and
are not given in Table 3. The greatest effect was observed
for the methylene protons in the crown fragment and the
protons of the naphthalene ring. It is known3 that the
1
Table 3. H NMR signals for CSN 1a in CD3CN and their shifts (in parentheses) upon complexation with Mg(ClO4)2, Sr(ClO4)2,
and Ba(ClO4)2
Comꢀ
pound
1H NMR (CD3CN), δ
a
a
C(Me)2
N—Me H(2´) H(10´) H(9´)
H(8´)
H(7´)
H(5´) N—CH2
OCH2
CSN 1a
1.34
1.30
(–0.04)
—
1.36, 1.38
(0.02)
1.34, 1.36
(0.02)
2.74
2.80
(0.04)
5.44
7.70
7.74
(0.04)
9.93
8.52
8.53
(0.01)
—
8.69
(0.17)
8.65
7.55
7.59
(0.04)
—
7.66
(0.11)
7.65
7.39
7.44
(0.05)
—
8.30
8.32
(0.02) (–0.39)
—
8.13
6.88
6.49
3.40
3.45
(0.05)
—
3.50
(0.10)
3.50
3.52—3.62
3.60—3.75
CSN 1a + Mg2+b (SF)
CSN 1a + Mg2+b (MF)
CSN 1a + Sr2+с
—
6.92
(∼0.1)
3.60—3.75
(∼0.1)
3.60—3.75
(∼0.1)
2.70
7.88
7.52
(–0.04) (0.18)
2.70 7.82
(–0.04) (0.12)
(0.13) (–0.17) (0.04)
7.54 8.15 6.92
(0.15) (–0.15) (0.04)
CSN 1a +Ba2+с
(0.13)
(0.10)
(0.10)
a Crown ether
b A 100ꢀfold excess of the salt.
c A tenfold excess of the salt.

Spironaphthoxazines linked with azacrown ethers
Russ.Chem.Bull., Int.Ed., Vol. 51, No. 1, January, 2002
63
indoline and naphthoxazine fragments are nearly perpenꢀ
dicular to each other in the molecule. This accounts for
spatial limitations of the complexation.
1a in the presence of magnesium perchlorate in different
concentrations (see Fig. 3) show that an increase in the
concentration of Mg2+ in the range CM/CL < 10 intensiꢀ
fies the absorption of the MF complex and shifts its band
to the longꢀwavelength region so that its position virtually
coincides with that for the MF of SN 2. Aparently, in this
range of salt concentrations, complex E is formed in soluꢀ
tion, in which the crown N atom has no donor effect
because of its involvement in coordination with the metal
cation.
At higher metal concentrations, nothing but the inꢀ
tensity of the absorption band of the complex changes.
The absorption bands of the complexes of CSNs 1a,b with
alkalineꢀearth cations in the visible region become less
intense in order of decreasing charge density on the metal
cation: Mg2+ > Ca2+ > Sr2+ > Ba2+ (see Table 1). The low
selectivity of the cationꢀinduced isomerization of CSNs
1a,b is evidence that the main process determining the
shift of the equilibrium to the MF is the interaction of
metal cations with the O atom of this form (the formation
of complex F, see Scheme 3).
Thus, the much stronger coordination of the metal
cations with the azacrown fragment than with the O atom
of the merocyanine form accounts for the order of the
formation of different complexes in solution as the metal
concentration increases: A→D→E→F. The high efficiency
of interaction of the metal cations with the azacrown
fragment in CSNs 1a,b makes the formation of comꢀ
plex C highly improbable.
Photoisomerization of CSNs 1a,b and their complexes.
The photoisomerization of SN 2 is characterized by a
monotonic decrease in the thermal relaxation constants
of the MF (kMF→SF) with an increase in the metal conꢀ
centration (Fig. 4, curves 1, 4). In the case of CSNs 1a,b,
this parameter is reduced more significantly for the conꢀ
centrations of Ca2+ and Ba2+ in the range CM/CL = 1—100
(see Fig. 4, curves 2, 3, 5, 6). At higher concentration
ratios (CM/CL > 100), the character of the observed
changes in this parameter does not depend on whether
the molecule contains the crown fragment or not.
A relative change in kMF→SF correlates with the stabilꢀ
ity of the resulting complexes (cf. Table 1 and Fig. 4).
Thus, in the presence of Ca2+ and Ba2+, kMF→SF of CSN
1b changes more substantially than that of CSN 1a, in
accordance with their complexation constants.
Signals from the methylene protons in the crown fragꢀ
ment and from the aromatic protons are shifted more
significantly for complexes with Sr2+ and Ba2+. Complexꢀ
ation with Sr2+ shifts signals from the aromatic protons
more strongly than that with Ba2+, which correlates
with the higher complexation constants of Sr2+ (cf.
Table 2).
Attention should be given to the upfield shifts of sigꢀ
nals from the HC(5´) proton in a complex with Mg2+ and
from the HC(7´) proton in complexes with Sr2+ and Ba2+
.
This effect can be a result of two processes during comꢀ
plexation, namely, (a) a decrease in the conjugation of
the lone electron pair of the N atom with the chromophore
system owing to its involvement in coordination with the
metal cation and (b) conformational reorganization of
the crown macrocycle, which can change the conformaꢀ
tion of the naphthoxazine fragment. Xꢀray diffraction
data3 showed that the conformation of the naphthoxazine
fragment is very labile, being determined by steric factors
even more greatly than by the electron influence of the
substituents. Apparently, the chemical shifts for Mg2+
complexes differ from those for Sr2+ and Ba2+ complexes
because the latter cations mainly coordinate to the crown
macrocycle, while the Mg2+ cation located in the crown
cavity coordinates the oxazine O atom. With a large exꢀ
cess of the metal, this results in the cationꢀinduced forꢀ
mation of the MF.
For the most part, the NMR and UV data are fully
consistent. Complexation between CSN 1a and Ba2+ or
Sr2+ involves the crown fragment, and addition of magꢀ
nesium salts shifts the equilibrium toward the colored
merocyanine form. This shift correlates with appearance
1
of additional signals in the H NMR spectrum, in parꢀ
As demonstarted above, metal cations in low concenꢀ
trations mostly coordinate the azacrown fragment. The
overall scheme of thermal relaxation can be written as
E → D → A (see Scheme 3). In this case, the rateꢀlimiting
stage of thermal decolorization is the isomerization of
merocyanine complex E into spiro complex D.
At higher concentrations of metal ions in solutions of
CSNs 1a,b (CM/CL > 100), the thermal relaxation conꢀ
stants of the merocyanine form decrease with an increase
ticular, from the azomethine proton at δ 9.9 and from the
N—Me group of the betaine structure of the merocyanine
isomer at δ 5.44.19
Cationꢀinduced isomerization of CSNs 1a,b. The inꢀ
tensities of the absorption bands in the visible region for
complexes of the MF of CSNs 1a,b depend on the nature
of the metal cation and their concentration in solution
(see Table 1). The illustrative absorption spectra of CSN

64
Russ.Chem.Bull., Int.Ed., Vol. 51, No. 1, January, 2002
Strokach et al.
kMMF→SF/k0
ions with the azacrown fragment of the SF and with the
oxygen atom of the MF. For this reason, the kinetic data
can be analyzed using the following kinetic model:
MF→SF
1
1
a
2
3
E
D,
(3)
F
E + M, KF = [F]/([E][M]).
(4)
The experimental deactivation rate constant of comꢀ
plex F is determined by
0.1
k = (k1 + k2KF[M])/(1 + KF[M]),
(5)
where k1 and k2 are the deactivation rate constants of
forms E and F, respectively, and KF is the equilibrium
constant of the process (4).
1
10
100
1000 CM/CL
This scheme is close to that proposed previously20 for
the complexation of spiro compound containing no crown
fragment and allows one, within the scope of our assumpꢀ
tions, to describe the complexation of CSNs 1a,b at high
metal concentrations. However, the theoretical curves
based on Eq. (5) fit the experimental deactivation rate
constants of photoexcited complexes only for Ca2+ catꢀ
ions. The constants of complexation involving the oxyꢀ
gen atom of the MF of compounds 1a,b and 2 with
Ca2+ are close (logK = 2.2—2.4), being significantly
lower than the corresponding constants of complexation
through the azacrown fragment of the spiro form (see
Table 2).
kMMF→SF/k0
MF→SF
1
4
b
5
6
0.1
It should be noted that the experimental dependences
of the thermal relaxation constants of the colored form on
the concentration of Mg2+ and Ba2+ cations in solution
satisfy the proposed model, which can be associated with
the probable formation of LM2 (for Mg2+) and L2M (for
Ba2+) complexes.
1
10
100
1000 CM/CL
Fig. 4. Effect of the concentration of (a) Ca2+ and (b) Ba2+
perchlorates on the relative thermal relaxation constant of the
MF (kMMF→SF/k0MF→SF) for 2 (1, 4), 1a (2, 5), and 1b (3, 6).
Thus, the spironaphthoxazines linked with the azaꢀ
15(18)ꢀcrownꢀ5(6) fragments were synthesized and studꢀ
ied in this work for the first time. It was shown that the
introduction of an azacrown fragment into the spiroꢀ
naphthoxazine molecule changes its spectral and photoꢀ
chemical properties. These changes are analogous to those
produced by an electronꢀdonor substituent (e.g., the
morpholine or piperidine residue) in the same position.
Addition of alkalineꢀearth cations to solutions of CSNs
1a,b results in a hypsochromic shift of the absorption
band of the SF, shifts the equilibrium toward the MF, and
changes the thermal relaxation rate of the MF. Based on
the spectral and kinetic data, we proposed the scheme of
complexation and calculated the stability constants of the
resulting complexes. According to the data obtained, the
complexation involves two centers, namely, the crown
fragment and the merocyanine O atom. The complexꢀ
ation via both centers depends on the surface charge denꢀ
sity of the metal cation; with the crown fragment as a
in the metal concentration (see Fig. 3), as in the case of
SN 2 containing no crown fragment. The equal slopes
of the curves of logkMMF→SF/k0
(kM
and
MF→SF
MF→SF
k0
are the thermal relaxation constants of CSNs
MF→SF
1a,b and SN 2, respectively) vs. the concentration of the
metal ions proves that the same anionic center of the
molecule, namely, the oxygen atom of the MF, is inꢀ
volved in complexation in this concentration range. Thus,
at high metal concentrations, the overall scheme of therꢀ
mal relaxation can be represented by F → E → D (see
Scheme 3). In this case, the rateꢀlimiting stage is the
cleavage of the coordination bond between the metal catꢀ
ion and the oxygen atom of the MF (F → E).
The complexation constants for the MF of the M2B
type were obtained with consideration of a large differꢀ
ence in efficiency between the interactions of metal catꢀ

Spironaphthoxazines linked with azacrown ethers
Russ.Chem.Bull., Int.Ed., Vol. 51, No. 1, January, 2002
65
1,3,3ꢀTrimethylꢀ6´ꢀ(1,4,7,10,13ꢀpentaoxaꢀ17ꢀazacycloꢀ
hexadodecꢀ17ꢀyl)spiro[indolinoꢀ2,3´ꢀ[3H]naphth[2,1ꢀb]oxazine]
(1b) was obtained analogously from azaꢀ18ꢀcrownꢀ6 as a viscous
complexation center, the size of the metal cation should
fit the crown cavity. Crown ether—metal complexes are
more stable than complexes involving the merocyanine O
atom. Investigations of these compounds are imporꢀ
tant in a search for new types of photochromic maꢀ
terials that are highly sensitive to metal cations in soꢀ
lutions.
1
oil. The yield of compound 1b was 3%. H NMR (DMSOꢀd6),
δ: 1.34 (s, 6 H, 2 Me); 2.74 (s, 3 H, N—Me); 3.52 (m, 20 H,
2 NCH2 + 4 OCH2); 6.63 (d, 1 H, H(4), J = 7.6 Hz); 6.88 (m,
2 H, H(2´) + H(6)); 7.13 (d, 1 H, H(7), J = 7.2 Hz); 7.20 (t,
1 H, H(5), J1 = 7.7 Hz, J2 = 7.1 Hz); 7.41 (t, 1 H, H(8´),
J1 = 8.6 Hz, J2 = 7.2 Hz); 7.56 (t, 1 H, H(9´), J1 = 7.6 Hz,
J2 = 7.0 Hz); 7.71 (s, 1 H, H(5)); 8.31 (d, 1 H, H(7´), J = 8.3 Hz);
8.51 (d, 1 H, H(7´), J = 8.3 Hz). Found (%): C, 68.44; H, 6.64;
N, 6.72. C34H43N3O6×0.5 MeOH. Calculated (%): C, 68.40;
H, 7.48; N, 6.93.
Experimental
1
H NMR spectra were recorded on Bruker AMXꢀ400 and
4ꢀ(1,4,7,10ꢀTetraoxaꢀ13ꢀazacyclopentadecꢀ13ꢀyl)ꢀ1,2ꢀ
naphthoquinone (3). B. A solution of sodium 1,2ꢀnaphthoꢀ
quinoneꢀ4ꢀsulfonate (1 g, 4 mmol) and azaꢀ15ꢀcrownꢀ5 (1 g,
4.6 mmol) in 30 mL of water was stirred at ∼20 °C for 6 h. After
the reaction was completed, the products were extracted with
chloroform. The solvent was removed, and the residue was reꢀ
crystallized from ether. The yield of compound 3 was 0.46 g
(31%), m.p. 131—146 °C. 1H NMR (CD3CNꢀd3), δ: 2.80—2.96
(m, 4 H, N(CH2)2); 3.05—3.25 (m, 8 H, 4 OCH2); 3.28 (t, 2 H,
OCH2); 3.90 (t, 2 H, OCH2); 6.1 (s, 1 H, H(3)); 7.50 (t, 1 H,
H(6), J = 7.7 Hz); 7.6 (t, 1 H, H(7), J1 = 7.5 Hz, J2 = 7.8 Hz);
7.83 (d, 1 H, H(5), J = 7.8 Hz); 8.08 (d, 1 H, H(8), J = 7.8 Hz).
MS, m/z (Irel (%)): 377 [M]+ (7); 216 (59); 173 (100);
172 (87); 171 (41); 159 (83); 158 (85); 145 (37); 129 (62);
115 (42).
Bruker DRXꢀ500 spectrometers in CD3CN with Me4Si as the
internal standard. Chemical shifts were measured with an accuꢀ
racy up to 0.01 ppm, and spinꢀspin coupling constant with an
accuracy up to 0.1 Hz. Mass spectra were recorded on a Varian
MATꢀ311A instrument (70 eV, direct inlet of the sample into
the ionization chamber). The course of the reactions was moniꢀ
tored by TLC on DCꢀAlufolien Kieselgel 60 F254 plates (Merck).
Column chromatography was carried out on Silica gel 60 silica
gel (0.063—0.200 mm).
Crownꢀcontaining spironaphthoxazines were synthesized
from 1,3,3ꢀtrimethylꢀ2ꢀmethylideneindoline (Fluka); azaꢀ15ꢀ
crownꢀ5 and azaꢀ18ꢀcrownꢀ6 (Merck); and 1ꢀnitrosoꢀ2ꢀnaphꢀ
thol, sodium 1,2ꢀnaphthoquinoneꢀ4ꢀsulfonate, and methanol
(all Aldrich). The starting compounds were used without addiꢀ
tional purification.
Electronic absorption spectra were recorded on a Shimadzu
UVꢀ3100 spectrophotometer. The electronic absorption spectra
of the colored form were recorded on a spectrophotometer while
continuously irradiating samples with light with λ = 365 nm
from a DRShꢀ250 mercury lamp. The thermal relaxation kinetꢀ
ics of the colored form was studied on a kinetic setup in the time
range 0.001—1000 s (photoexcitation with UV radiation genꢀ
erated by a pulse xenon lamp). Measurements were perꢀ
formed in solutions with the concentration of compounds CL =
2•10–4 mol L–1 at ∼20 °C. Acetonitrile (Aldrich, water content
0.005%) was used as a solvent. Complexing agents were Li, Mg,
Ca, Sr, and Ba perchlorates.
This work was financially supported by the Rusꢀ
sian Foundation for Basic Research (Project Nos. 99ꢀ
03ꢀ33064, 99ꢀ03ꢀ088072, and 01ꢀ03ꢀ06024), the
Program of International Scientific Cooperation
(PISC) (les Programmes Internationaux de Coopération
Scientifique) (Grant 705), and the International Associaꢀ
tion for the promotion of cooperation with scientists from
the New Independent States of the former Soviet Union
(INTAS, Grant No. 97ꢀ31193).
1,3,3ꢀTrimethylꢀ6´ꢀ(1,4,7,10ꢀtetraoxaꢀ13ꢀazacyclopentaꢀ
decꢀ13ꢀyl)spiro[indolinoꢀ2,3´ꢀ[3H]naphth[2,1ꢀb]oxazine] (1a).20
A. 1ꢀNitrosoꢀ2ꢀnaphthol (0.393 g, 2.25 mmol) was added to a
solution of azaꢀ15ꢀcrownꢀ5 (1 g, 4.5 mmol) in 5 mL of MeOH.
The reaction mixture was heated in an atmosphere of argon at
80 °C for 6 h, and then a solution of 1,3,3ꢀtrimethylꢀ2ꢀ
methylideneindoline (0.4 mL, 2.25 mmol) in 10 mL of MeOH
was added. The reaction mixture was kept at 80 °C for 2.5 h,
cooled, and concentrated. Double column chromatography gave
compound 2 20 (0.43 g, 47%) and compound 1a (26 mg, 5%) as a
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Received March 21, 2001;
in revised form June 6, 2001