Complex formation of 2,2-diphenyl-2H-benzo[f]chromene containing the aza-18-crown-6-ether fragment in the polymeric layer

Article abstract of DOI:10.1023/B:RUCB.0000019883.50477.cc

The synthesis of 2,2-diphenyl-2H-benzo[f]chromene containing the aza- 18-crown-6-ether fragment was described. Its complex formation with alkaline-earth metal ions in dibutyl phthalate and the polymeric gelatin film was investigated. The treatment of the

Full text of DOI:10.1023/B:RUCB.0000019883.50477.cc

Russian Chemical Bulletin, International Edition, Vol. 52, No. 12, pp. 2661—2667, December, 2003
2661
Complex formation of 2,2ꢀdiphenylꢀ2Hꢀbenzo[ f ]chromene containing
the azaꢀ18ꢀcrownꢀ6ꢀether fragment in the polymeric layer
V. B. Nazarov,aꢀ O. A. Fedorova,b S. B. Brichkin,a T. M. Nikolaeva,a
S. P. Gromov,b A. V. Chebun´kova,b and M. V. Alfimovb
aInstitute of Problems of Chemical Physics, Russian Academy of Sciences,
142432 Chernogolovka, Moscow Region, Russian Federation.
Eꢀmail: nazarov@icp.rssi.ru
bCenter of Photochemistry, Russian Academy of Sciences,
7a ul. Novatorov, 119421 Moscow, Russian Federation
The synthesis of 2,2ꢀdiphenylꢀ2Hꢀbenzo[ f ]chromene containing the azaꢀ18ꢀcrownꢀ6ꢀether
fragment was described. Its complex formation with alkalineꢀearth metal ions in dibutyl phthaꢀ
late and the polymeric gelatin film was investigated. The treatment of the layers containing the
ionophore mentioned with aqueous solutions of the corresponding salts in the presence of
NaBPh4 as the phase transfer catalyst results in the extraction of the metal cation into the
polymeric layer due to complex formation with crownꢀcontaining benzo[ f ]chromene. The
complex formation is accompanied by changes in the spectroscopic characteristics of chromene
in the closed and open forms and an increase in the lifetime of the merocyanine form. The
effects obtained depend on the metal cation concentration in a solution and the time of layer
treatment.
Key words: 2,2ꢀdiphenylꢀ2Hꢀbenzo[ f ]chromene, azaꢀ18ꢀcrownꢀ6 ether, complex formaꢀ
tion, alkalineꢀearth metal cations, gelatin, emulsion, polymeric layers.
Photochromic crown ethers demonstrate an optical
response to complex formation due to changes in the
structure caused by phototransformations.1—7 Systems
based on the latter are promising for use in various practiꢀ
cal applications (photoswitchable extractions of metal catꢀ
ions, molecular electronics, systems of optical recording
of information, and nonlinear optical devices).
Benzo[ f ]chromenes also comprise a promising class
of compounds.8—13 Intense works on the development of
new representatives of this series with a high coloration
level and stable upon introduction into polymeric matriꢀ
ces are evoked by their use in the production of photoꢀ
chromic lenses and coatings.
We have recently6,7 reported the synthesis of benꢀ
zo[ f ]chromene containing the azaꢀ15ꢀcrownꢀ5ꢀether
fragment as the substituent. It is shown that in an MeCN
solution this compound can react with alkalineꢀearth
metal cations, and complex formation is accompanied by
considerable spectral changes. The photoinduced formaꢀ
tion of the open form of benzo[ f ]chromene decreases the
ability of the ligand to bind metal cations.
The purpose of the present work is to study the comꢀ
plex formation of benzo[ f ]chromene containing the
crownꢀether fragment in the polymeric film with alkaꢀ
lineꢀearth metal cations in aqueous solutions of the corꢀ
responding salts. This process gives an optical response.
For this purpose, we synthesized benzo[ f ]chromene simiꢀ
lar in structure with the compound synthesized and obꢀ
tained previously14,15 but containing the azaꢀ18ꢀcrownꢀ
6ꢀether fragment as the ionophoric substituent with higher
binding constants with alkalineꢀearth metal cations comꢀ
pared to those of azaꢀ18ꢀcrownꢀ6 ether.16 Comparison of
the results of this study with the data obtained by us previꢀ
ously for MeCN solutions enables the analysis of proꢀ
cesses in the complicated system of gelatin layers.
Results and Discussion
Synthesis of 2,2ꢀdiphenylꢀ2Hꢀbenzo[ f ]chromene conꢀ
taining the azaꢀ18ꢀcrownꢀ6ꢀether fragment. The multistep
process of the synthesis of benzo[ f ]chromene 4 studied in
this work is presented in Scheme 1. Diaryl ketone 2 conꢀ
taining the azaꢀ18ꢀcrownꢀ6ꢀether fragment was syntheꢀ
sized by the acylation of benzanilide with phenylazaꢀ
18ꢀcrownꢀ6 ether (1) in the presence of POCl3 via
the Vilsmeier reaction.17 The corresponding propargyl
alcohol 3 was synthesized from diaryl ketone 2 using
the ethylenediamine complex of lithium acetylenide
LiC≡CH•NH2(CH2)2NH2. The reaction of compound 3
with 2ꢀnaphthol in the presence of TsOH in toluene afꢀ
forded crownꢀcontaining benzo[ f ]chromene 4 in 35%
yield.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2518—2524, December, 2003.
1066ꢀ5285/03/5212ꢀ2661 $25.00 © 2003 Plenum Publishing Corporation

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Russ.Chem.Bull., Int.Ed., Vol. 52, No. 12, December, 2003
Nazarov et al.
Scheme 1
Complex formation of chromene 4 in solutions of dibuꢀ
tyl phthalate. Since in the obtained polymeric layer (see
Experimental) chromene 4 exists as an emulsion of its
solution in dibutyl phthalate (DBP), complex formation
in pure DBP was preliminarily studied. The absorption
spectra of a solution of chromene 4 in DBP in the presꢀ
ence of the Ba2+ cations at different cation : chromene 4
molar ratios (curves 1—7) and the absorption spectrum of
the complex with the Mg2+ ion in a 20ꢀfold excess of the
latter (curve 8) are presented in Fig. 1. It is well seen that
an increase in the cation concentration results in systemꢀ
atic changes in the absorption spectrum, and the influꢀ
ence of the Mg2+ and Ba2+ cations is almost the same.
Scheme 2
A
1
7
0.6
0.4
0.2
1
7
8
9
320
340
360
λ/nm
Fig. 1. Absorption spectra of solutions of chromene 4 in DBP
(С = 7.62•10–5 mol L–1) at different Ba2+ : chromene molar
ratios: 0 (1), 0.1 (2), 0.2 (3), 0.4 (4), 1 (5), 5 (6), and 20 (7).
Curve 8 corresponds to the addition of 20ꢀfold Mg2+ excess to a
solution of chromene 4. Curve 9 is the absorption spectrum of
DBP in a cell with l = 1 cm.

Crownꢀcontaining 2,2ꢀdiphenylꢀ2Hꢀbenzo[ f ]chromene Russ.Chem.Bull., Int.Ed., Vol. 52, No. 12, December, 2003 2663
A
Therefore, only the barium cation was used in further
studies.
7
0.8
0.6
0.4
0.2
The changes observed in the absorption spectrum of
the closed form of benzo[ f ]chromene 4 in the presence
of metal cations are caused by complex formation involvꢀ
ing the crownꢀether fragment (Scheme 2). These spectral
changes are similar to those observed previously14,15 by
the study of the complex formation of azaꢀ15ꢀcrownꢀ5ꢀ
containing benzo[ f ]chromene with alkalineꢀearth metal
cations in a MeCN solution.
6
5
4
3
2
1
Irradiation of a solution of compound 4 results in the
formation of the photoinduced form 5 (Scheme 3).
450
500
550
600
650 λ/nm
Scheme 3
Fig. 2. Photostationary absorption spectra of a solution of comꢀ
pound 5 (С = 7.5•10–5 mol L–1) in DBP at different [Ba2+] : [4]
molar ratios: 0 (1), 0.1 (2), 0.25 (3), 0.8 (4), 1.25 (5), 5 (6), and
10 (7). To obtain a solution of compound 5, sample 4 was
excited with the light from a DRShꢀ1000 mercury lamp through
the UFSꢀ6 light filter in a cell with l = 1 cm.
formation: the crownꢀether fragment and O atom of the
merocyanine form.
As shown by our studies, in the case of benzo[ f ]chroꢀ
mene containing the azaꢀ15ꢀcrownꢀ5 fragment, in a
MeCN solution the formation of a metal cation complex
to the crownꢀether fragment is accompanied by the hypsoꢀ
chromic shift of the longꢀwave absorption band, whereas
the coordination of the cation with the O atom, on the
contrary, results in the bathochromic shift in the absorpꢀ
tion spectrum of the merocyanine form.15 These spectral
changes can be explained if the molecule of the open
form of benzochromene can be presented as consisting of
two moieties (Scheme 4): donor (crownꢀether) and acꢀ
ceptor. The absorption spectrum of the compound is a
characteristic of the charge transfer from the donor to the
acceptor moiety. Complex formation to the crownꢀether
fragment should prevent the electron density transfer, reꢀ
The photostationary absorption spectrum of comꢀ
pound 5 also changes in the presence of the Ba2+ cations
(Fig. 2). The open form 5, unlike starting benzo[ f ]chroꢀ
mene 4, has two coordination sites capable of complex
Scheme 4

2664
Russ.Chem.Bull., Int.Ed., Vol. 52, No. 12, December, 2003
Nazarov et al.
sulting in the hypsochromic shift. By contrast, the coorꢀ
dination of the O atom with the cation enhances the
withdrawing properties of this part of the molecule faciliꢀ
tating the easier charge transfer and, as a consequence, it
is accompanied by the bathochromic shift of the longꢀ
wave absorption band.15
The observed considerable hypsochromic shift in the
UV spectrum of the open form 5 in a DBP solution in the
presence of the Ba+ cations indicates that the formation
of the 5•Ba2+ complex involving the crownꢀether fragꢀ
ment of the compound is the main process. The stability
of this complex is higher than that of the complex formed
by the coordination of the O atom of the merocyanine
form with the metal cation, because the macrocycle conꢀ
tains several heteroatoms for binding with the metal catꢀ
ion due to the soꢀcalled "macrocyclic effect." 14,15
Coordination with the metal cation results in the elecꢀ
tron density redistribution along the whole conjugation
chain, which increases considerably the lifetime of the
open form 5. This is confirmed by the data presented in
Fig. 3: the lifetime of the open form increases signifiꢀ
cantly with an increase in the cation concentration. Howꢀ
ever, this dependence is explicitly nonlinear with some
induction period (see Fig. 3). At the [Ba2+] : [5] ratios
from 0 to 0.5, the influence is very low followed by the
region of efficient response ([Ba2+] : [5] = 0.5—1.5) and,
finally, the saturation region is observed, which also can
be considered linear but with much lower sensitivity to
changes in the Ba2+ ion concentration. Most likely, sharp
changes in the spectra correspond to the formation of the
5•Ba2+ complex, and the subsequent smooth changes
correspond to the formation of the 5•(Ba2+)2 complex. It
is known15 that the stability of the complex with the
О—Ba2+ coordination is insignificant, and its formation
requires high cation excess.
the properties of chromene 4 in the gelatin layer, the
prepared samples were treated with aqueous solutions of
the corresponding metal perchlorates in the presence of
NaBPh4 used as a phase transfer catalyst, which accelerꢀ
ates the ion equilibration, after which the layer was rinsed
with water and dried under standard conditions. Referꢀ
ence experiments showed that the treatment of the layers
with water and aqueous solutions of the SVꢀ81 surfactant
exerted no effect on the spectroscopic and photochromic
properties of chromene, whereas the treatment with aqueꢀ
ous solutions containing the Ba2+ ion results in effects
similar to those observed in solutions. However, note that
the solubility of alkalineꢀearth metal perchlorates in waꢀ
ter exceeds their solubility in DBP, and the volume of the
organic phase (DBP) in the film is much smaller than the
water volume in the treating solution. Therefore, only a
very small portion of the Ba2+ ions can diffuse into DBP
microdrops from an aqueous solution. For this reason the
absorption spectrum changes insignificantly. The photoꢀ
stationary absorption spectra and plots of the lifetime of
the open form are much more sensitive. The photoꢀ
stationary absorption spectra of the layer treated with an
aqueous solution of Ba(ClO4)2 for 5 h (curve 1) and the
reference layer stored in water for 5 h (curve 2) are preꢀ
sented in Fig. 4. For clarity, curve 3 represents the differꢀ
ential spectrum of curves 1 and 2, which is analogous to
the photostationary spectra obtained in DBP solutions at
high Ba2+ cation excess (see Fig. 2).
The plot of the lifetime of the merocyanine form 5 vs.
duration of treatment of the sample with a solution of
Ba(ClO4)2 is presented in Fig. 5. The lifetime increases
almost threefold at longer duration of treatment and is a
very sensitive parameter indicating the presence of the
Ba2+ cation in an aqueous solution.
Study of complex formation of chromene 4 in gelatin
layers. In order to study the influence of metal cations on
A
0.6
τ/s
0.5
1
12
10
8
0.4
0.3
0.2
0.1
1
2
6
2
4
3
1
2
3
4
5
6
[Ba2+] : [5]
500
600
λ/nm
Fig. 3. Changes in the lifetime (τ) of the open chromene form
with an increase in the concentration of the Ba2+ cations in
DBP: λ = 550 (1) and 440 nm (2) (cell with l = 1 cm, chromene
concentration 7.5•10–5 mol L–1; the sample was excited with
the light from a DRShꢀ1000 mercury lamp through the UFSꢀ6
light filter).
Fig. 4. Photostationary absorption spectra of the film sample
treated with an aqueous solution containing the Ва2+ cations (1)
and with water (2) and the differential photostationary spectrum
of compounds 4 and 5 (multiplied by the coefficient 2.5 for
clarity). The layer was excited with the light from a DRShꢀ1000
mercury lamp through the UFSꢀ6 and BSꢀ7 light filters.

Crownꢀcontaining 2,2ꢀdiphenylꢀ2Hꢀbenzo[ f ]chromene Russ.Chem.Bull., Int.Ed., Vol. 52, No. 12, December, 2003 2665
τ/s
SVꢀ81, and DBP (Reakhim) purified by double vacuum distillaꢀ
tion. Absorption spectra were recorded on Specord M40 and
Perkin—Elmer Lambda EZ210 spectrophotometers. Photoꢀ
stationary absorption spectra and lifetimes of the open form
were measured on an original laboratory setup. Emulgation was
carried out with an UZDNꢀA ultrasonic dispergator. Gelatin
films were supported using a special spray stage, whose temperaꢀ
ture was maintained constant and the horizontal position of the
surface was controlled.
6
4
2
1
2
[4ꢀ(1,4,7,10,13ꢀPentaoxaꢀ16ꢀazacyclooctadecꢀ16ꢀyl)pheꢀ
nyl]phenylmethanone (2). A mixture of benzanilide (0.2 g,
1 mmol) and phenylazaꢀ18ꢀcrownꢀ6 ether (1) (0.7 g, 2 mmol)
was heated with stirring to melting and then cooled to ∼20 °C.
POCl3 (0.3 g, 2 mmol) was added dropwise to the mixture along
with cooling with ice. Then the mixture was stored at 100 °С for
4 h in an oil bath and dissolved in 15% HCl on heating (∼30 °C).
The resulting solution was filtered to remove an orange insoluble
precipitate, and a 10% solution of NaOH was added to the
filtrate until an alkali reaction was shown by litmus paper. The
reaction mixture was extracted with benzene, the extract was
washed with water, and the solvent was evaporated. The product
was purified by column chromatography on silica gel (silica gel
L 40—100 µm (Chemapol) using a benzene—MeOH (from 20 : 1
to 10 : 1) mixture as eluent or Kieselgel 60 (Merck) using a
heptane—AcOEt (from 2 : 1 to 1 : 3) mixture as eluent). The
yield of ketone 2 was 0.053 g (12%, oil). 1H NMR, δ: 3.67 (br.s,
16 H, 8 СH2О); 3.74 (m, 8 H, 4 СH2О); 6.70 (d, 2 H, H(3),
H(5), J = 9.0 Hz); 7.46 (t, 2 H, H(3´), H(5´), J = 7.6 Hz); 7.53
(t, 1 H, H(4´), J = 7.4 Hz); 7.73 (d, 2 H, H(2´), H(6´), J = 7.3
Hz); 7.78 (d, 2 H, H(2), H(6), J = 9.0 Hz). Mass spectrum,
m/z (Irel (%)): 443 [M]+ (100), 267 (28), 266 (34), 254 (40), 224
(53), 210 (65), 209 (48), 132 (62), 105 (74), 76 (48). Highꢀ
resolution mass spectrum, found: m/z 443.2301 [M]+.
C25H33NO6. Calculated: M = 443.2307.
1ꢀ[4ꢀ(1,4,7,10,13ꢀPentaoxaꢀ16ꢀazacyclooctadecꢀ16ꢀyl)pheꢀ
nyl]ꢀ1ꢀphenylpropꢀ2ꢀynꢀ1ꢀol (3). A solution of diaryl ketone 2
(0.44 g, 1 mmol) in anhydrous THF (25 mL) was added dropwise
to a suspension of LiC≡CH•NH2(CH2)2NH2 (0.46 g, 5 mmol)
in anhydrous THF (25 mL) for 1 h at 60 °С with stirring. The
reaction mixture was stirred for 2 h at 60 °С, then water was
added, and the product was extracted with AcOEt. The organic
fraction was washed with water to the neutral reaction by litmus
paper, and the solvent was evaporated. The residue was exꢀ
tracted with hot hexane, and a light yellow product was precipiꢀ
tated on cooling. The yield of compound 3 was 0.42 g (90%, oil).
1H NMR, δ: 2.67 (s, 1 H, ОH); 2.85 (s, 1 H, С≡H); 3.65 (br.s,
24 H, 12 СH2О); 6.63 (д, 2 H, H(3), H(5), J = 8.8 Hz); 7.27 (m,
1 H, H(4´)); 7.34 (m, 2 H, H(3´), H(5´)); 7.39 (d, 2 H, H(2),
H(6), J = 8.7 Hz); 7.63 (d, 2 H, H(2´), H(6´), J = 7.0 Hz). Mass
spectrum, m/z (Irel (%)): 469 [M]+ (7), 443 (40), 266 (35), 254
(32), 236 (30), 224 (56), 210 (65), 132 (52), 105 (100), 77 (19).
Highꢀresolution mass spectrum, found: m/z 469.2457 [M]+.
C27H35NO6. Calculated: M = 469.2464.
50
100
150
200
t/min
Fig. 5. Plots of the lifetime (τ) of the open form of chromene 4
in the film vs. time of treatment of the sample (t) with an
aqueous solution of Ba(ClO4)2 in the presence of NaBPh4 (С =
4.87•10–4 mol L–1): λ = 550 (1) and 440 nm (2).
Thus, benzo[ f ]chromene 4 introduced into the gelaꢀ
tin layer as an emulsion of microdrops of its solution in
DBP retains the photochromic properties. UV irradiation
in the absorption region of the closed form induces the
merocyanine isomer with the characteristic absorption
band at λ = 550 nm and a lifetime of ∼2 s. The treatment
of such layers with aqueous solutions of alkalineꢀearth
metal salts in the presence of the phase transfer catalyst
(NaBPh4) changes both the spectroscopic characteristics
of chromene in the closed and open forms and the lifeꢀ
time of the merocyanine form, increasing the latter by
almost three times depending on the metal cation conꢀ
centration in a solution and duration of the layer treatꢀ
ment. These changes are qualitatively the same as those
occurred in homogeneous solutions of chromene in DBP
when alkalineꢀearth metal perchlorates are added. The
main conclusion is that chromene in the polymeric layer
reacts to the presence of metal cations in the aqueous
phase as in the case of homogeneous solutions. Reactions
of the future sensor polymeric layer can easily be simuꢀ
lated using this property.
Experimental
1
H NMR spectra were recorded on a Bruker DRXꢀ500 specꢀ
trometer (working frequency 500.13 MHz) in CDCl3. Chemical
shifts were measured with an accuracy of 0.01 ppm, and the
accuracy of measuring spinꢀspin coupling constants was 0.1 Hz.
Mass spectra were obtained on a Varian MAT 311A instrument.
Highꢀresolution mass spectra were obtained on a Finnigan
MAT 8430 instrument (ionization energy 70 eV, direct injection
of the sample into the ionization region). The course of the
reaction was monitored by TLC on 25 DCꢀAlufolien Kieselgel
60 F254 and DCꢀAlufolien Aluminiumoxid 60 F254 neutral
(Typ E, Merck) plates. Commercial reagents and solvents
(Merck) were used in the syntheses of compounds 2—4.
16ꢀ[4ꢀ(2ꢀPhenylꢀ2Hꢀbenzo[ f ]chromenꢀ2ꢀyl)phenyl]ꢀ
1,4,7,10,13ꢀpentaoxaꢀ16ꢀazacyclooctadecane (4). A mixture of
alcohol 3 (0.47 g, 1 mmol) and 2ꢀnaphthol (0.15 g, 1 mmol) in
anhydrous toluene (10 mL) was prepared on stirring and heating
(to 60—80 °С). TsOH•H2O (0.02 g, 0.1 mmol) was added, and
the mixture was stirred for 3 h. Then water was added to the
mixture, the solvent was evaporated, and the residue was puriꢀ
fied by column chromatography on Al2O3 (Aluminiumoxid
The following reagents were used for the preparation of gelaꢀ
tin layers with benzo[ f ]chromene 4: distilled water, NaBPh4
(Aldrich), photoinert bone gelatin (trade mark A), surfactant

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Russ.Chem.Bull., Int.Ed., Vol. 52, No. 12, December, 2003
Nazarov et al.
aktiviert basisch (Typ 5016A, Merck), benzene—AcOEt (3 : 1)
mixture as eluent). The yield of chromene 4 was 0.21 g (35%),
m.p. 78—80 °С (from hexane). Found (%): C, 74.48; H, 6.98;
N, 2.31. C37H41NO6. Calculated (%): C, 74.60; H, 6.94; N, 2.35.
1H NMR, δ: 3.52 (m, 4 H, 2 СH2О); 3.54 (m, 8 H, 4 СH2О);
3.56 (br.s, 8 H, 4 СH2О); 3.60 (m, 4 H, 2 СH2О); 6.25 (d, 1 H,
H(3´), J = 10.0 Hz); 6.66 (d, 2 H, H(2), H(6), J = 8.9 Hz); 7.22
(d, 1 H, H(10´), J = 8.8 Hz); 7.26 (m, 2 H, H(3), H(5)); 7.27
(m, 1 H, H(4″)); 7.37 (m, 4 H, H(3″), H(5″), H(7´), H(4´));
7.52 (m, 1 H, H(6´)); 7.53 (d, 2 H, H(2″), H(6″), J = 8.9 Hz);
7.74 (d, 1 H, H(9´), J = 8.9 Hz); 7.79 (d, 1 H, H(8´), J =
8.0 Hz); 8.04 (d, 1 H, H(5´), J = 8.5 Hz). Mass spectrum,
m/z (Irel (%)): 595 [M]+ (100), 257 (57), 168 (26), 105 (22), 100
(24), 87 (28), 82 (29), 77 (26), 71 (40), 69 (37).
d/µm
0.70
0.65
0.60
0.55
0.50
0.45
0.40
1
2
3
Preparation of gelatin layers with benzo[ f ]chromene 4. Since
the chromene content in the polymeric layer permissible for
aqueous solutions of metal cations should remain constant durꢀ
ing treatment and chromene 4 is soluble in both organic solvents
and water, to prepare the working sample, we used a procedure,
according to which benzo[ f ]chromene 4 was first dissolved in
the organic hydrophobic solvent DBP and then emulgated in an
aqueous solution of the natural polymer gelatin. The drop size
was determined on a CAPAꢀ500 analyzer of particle size. The
resulting emulsion was supported on a glass support. A similar
procedure is widely used in the production of colored photoꢀ
graphic materials to introduce protected colorꢀforming compoꢀ
nents into layers and provides reliable, well reproducible results.18
In order to obtain layers with the optimum characteristics
(absorption, thickness, transparency), we studied the depenꢀ
dences of the size of emulsion drops on the ratio of the hydroꢀ
phobic and aqueous phases, amount and concentration of a
surfactant, gelatin concentration, and duration of ultrasonication
of the emulsion. The results are presented in Figs. 6 and 7,
which show that at concentrations of gelatin of 5% and SVꢀ81
surfactant ≥6% the average drop size remains unchanged during
sonication of the emulsion for 10 min and longer.
5
6
7
8
9
C (%)
Fig. 7. Plots of the average diameter of microdrops (d) of the
DBP emulsion in a 5% solution of gelatin vs. concentration of
the SVꢀ81 surfactant (C) at different times of sonication: 5 (1),
10 (2), and 15 min (3).
Frequency volume distribution (%)
40
30
20
10
0.4
0.6
0.8
1.0
d/µm
Fig. 8. Particle volume distribution of DBP microdrops in the
emulsion (d is the diameter of microdrops).
Taking into account the data obtained, we formulated the
following procedure of layer preparation: a solution (0.8 mL) of
benzo[ f ]chromene 4 in DBP (C = 1.6•10–2 mol L–1) and a 6.5%
solution (0.48 mL) of the SVꢀ81 surfactant in an EtOH—water
(1 : 1) mixture was added to a 5% (wt.%) aqueous solution
(5.12 mL) of gelatin. The mixture was sonicated for 10 min. As a
result, an emulsion with the average diameter of microdrops
d = 0.4 µm and a rather narrow particle volume distribution
(Fig. 8) was obtained with a good reproducibility.
d/µm
0.70
The prepared emulsion was supported at 40 °С onto a glass
support on a horizontal spray stage and dried at ∼20 °C. A soluꢀ
tion of benzo[ f ]chromene 4 in DBP with a concentration of
1.6•10–2 mol L–1 should be used to prepare the layer with the
absorption A = 0.5 at λ = 347 nm (when a noticeable effect of
the solvent (DBP) absorption is absent). The surface area of the
supports was 20 cm2, and the emulsion volume on the plate
was 1 cm3. Under these conditions of supporting, the total thickꢀ
ness of the dry layer was ∼85 µm. The prepared layers sustain a
prolonged treatment (at least 8 h) in aqueous solutions of metal
salts without layer decomposition and without losses of introꢀ
duced chromene. The NaBPh4 phase transfer catalyst (C =
4.87•10–4 mol L–1) was added to a solution containing metal
ions to accelerate the penetration of the metal cations from the
aqueous phase into the DBP microdrops.
0.65
0.60
1
0.55
0.50
2
0.45
3
0.40
6
8
10
12
14
t/min
Fig. 6. Plots of the average diameter of microdrops (d) of the
DBP emulsion in a 5% solution of gelatin vs. time of sonicaꢀ
tion (t) at different concentrations of the SVꢀ81 surfactant: 5 (1),
6 (2), and 10% (3).
This work was financially supported by the Internaꢀ
tional Association of Assistance for Cooperation with Sciꢀ

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Received July 18, 2003