Investigation of the azacrown-ether substituted naphtopyranes

Article abstract of DOI:10.1080/15421400590946181

The study of the complexation of 3,3-diphenyl-3H-benzo[f]chromenes containing an aza-15-crown-5-ether or morpholine units with Mg²⁺, Ba²⁺ and Pb²⁺ in acetonitrile are reported. The spectroscopic and kinetic behaviour of th

Full text of DOI:10.1080/15421400590946181

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Investigation of the
Azacrown-Ether Substituted
Naphtopyranes
a
a
a
A. V. Chebun'kova , S. P. Gromov , T. M. Valova
,
a
a
b
Yu. P. Strokach , M. V. Alfimov , O. A. Fedorova
b
b
,
a
V. Lokshin & A. Samat
Faculte des Sciences de Luminy, Universite de la
Mediterranee, Marseille, France
b
Photochemistry Center of RAS, Moscow, Russia
Version of record first published: 31 Aug 2006.
To cite this article: A. V. Chebun'kova , S. P. Gromov , T. M. Valova , Yu. P. Strokach ,
M. V. Alfimov , O. A. Fedorova , V. Lokshin & A. Samat (2005): Investigation of the
Azacrown-Ether Substituted Naphtopyranes, Molecular Crystals and Liquid Crystals,
430:1, 67-73
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Mol. Cryst. Liq. Cryst., Vol. 430, pp. 67–73, 2005
Copyright # Taylor & Francis Inc.
ISSN: 1542-1406 print=1563-5287 online
DOI: 10.1080/15421400590946181
Investigation of the Azacrown-Ether Substituted
Naphtopyranes
A. V. Chebun’kova
S. P. Gromov
Yu. P. Strokach
T. M. Valova
M. V. Alfimov
Faculte des Sciences de Luminy, Universite de la Mediterranee,
Marseille, France
O. A. Fedorova
V. Lokshin
A. Samat
Photochemistry Center of RAS, Moscow, Russia
The study of the complexation of 3,3-diphenyl-3H-benzo[f]chromenes containing
2þ
2þ
2þ
an aza-15-crown-5-ether or morpholine units with Mg , Ba and Pb in aceto-
nitrile are reported. The spectroscopic and kinetic behaviour of the photomerocya-
nine isomers of these chromenes is strongly affected by complexation with metal
cations. In order to interpret the experimental data, a formation of anion-‘‘capped’’
complexes was supposed.
Keywords: anion-‘‘capped’’ complex; aza-18-crown-6 ether; complex formation; 3,3-
diphenyl-3H-benzo[f]chromene; photochromic behaviour
INTRODUCTION
Photochromic compounds have received great interest in the last
years due to their application such as ophthalmic lens, transparencies,
plastic films, promising materials for the information imaging and
This work was supported by the Russian Foundation for Basic Research (Projects 02-
0
3-33058, 03-03-32888) and program ‘‘Integration’’ of the Russian Ministry of Sciences,
Technology and Education.
Address correspondence to O. A. Fedorova, Photochemistry Center of RAS, Novatorov
str., 7a, Moscow, 119421, Russia. E-mail: fedorova@photonics.ru
67

6
8
V. Lokshin et al.
storage, etc [1]. The development of these photochromic systems is
aimed at the improved photostability, to obtain higher sensitivity, a
wide choice of operating wavelengths and amplification capability.
Incorporation of a crown ether moiety which is able to bind metal
ions into the naphthopyrans skeleton can be explored to tune the
photochromic properties by using complexing process [2].
RESULTS AND DISCUSSION
Here we present the results of the spectral and kinetic investigations
2
þ
2þ
of the benzochromenes 1a–c and their complexes with Mg , Ba and
2þ
Pb . The compounds were synthesized according to the three-step
procedure [3,4] represented in Scheme 1. The structures attributed
to 1a–c were confirmed by H NMR spectroscopy data, mass-
1
spectrometry and elemental analysis (see Experimental part).
Compounds 1a–c in MeCN exhibited very similar UV=Vis absorp-
2þ
2þ
2þ
tion spectra. The addition of Mg , Ba and Pb cations to a solution
of 1b,c led to the small hypsothochromic shift up to 5–10 nm of the
long wavelength band, indicating that metal cation is bound by the
macrocyclic unit of 1b,c (Scheme 2). In contrast, the absorption spec-
trum of 1a was affected only at a high metal cation concentration
ꢀ
3
(
0.1 mol dm ).
SCHEME 1

Investigation of the Azacrown-Ether Substituted Naphtopyranes
69
SCHEME 2
UV irradiation of 1a–c in MeCN resulted in the appearance of a
broad absorption band in the visible region, which was assigned to
the merocyanine isomer. The dark ring-closure reaction for merocya-
nine isomer of 1a–c occurred with a rate constant k of about 0.11–
d
ꢀ1
0
.14 s and resulted in the initial chromene. The presence of the metal
cations in the solution of photomerocyane form led to a significant
change in the dark lifetime of photomerocyanines 1a–c and caused
strong shifts in their absorption spectra, indicating that these com-
pounds were able to bind metal cations (Fig. 1, Table 1).
In the merocyanine form of benzochromenes 1a–c there are two
places for the coordination of metal cations: crown ether fragment
(
or heteroatoms of nmorpholine residue) and carbonyl oxygen atom [5].
ꢀ
1
The small changes of k =s observed for the 1a in the presence of
d
2
þ
2þ
Ba , Pb cations at relationship ligand:metal cation ¼ 1:1 indicates
that in this condition the concentration of complex between 1a and
metal cations is insignificant. The formation of a 1:1 complex between
open form of 1a–c and Mg leads to an increase in the rate constant
for the dark ring-closure reaction of 1a–c (Scheme 2). The effect does
not depend on the presence of crown ether fragment in molecule. The
Mg ion is not able to the effective coordination with crown ether
fragment, because it has got the cation radii substantially smaller
then size of 18-crown-6 ether cavity. Otherwise, the Mg cation can
2
þ
2
þ
2
þ

7
0
V. Lokshin et al.
SCHEME 2 (Continued).
bind with carbonyl oxygen atom due to high charge density. The
results of the formation of MgꢀO coordination should lead to the
increase of the polarity of molecule (Scheme 2). In the polar form the
dark ring –closure reaction will occur more easily.
2þ
The formation of a 1:1 complex between open form of 1b,c and Ba ,
2
þ
Pb leads to a large bathosochromic effect and the decrease in the
rate constant for dark ring-closure reaction. The effect is explained
the formation of the anion-‘‘capped’’ complex of metal cation located
FIGURE 1 UV=V is spectrum of 1b in acetonitrile (1) free 1b; (2) in the
presence of Mg(ClO ) ; (3) in the presence of Ba(ClO ) ; (4) in the presence
4
2
4 2
of Pb(ClO
4
)
2
, prepared by irradiation of solution with light at 365 nm;
] ¼ 2 ꢁ 10 m=l.
2
þ
ꢀ4
[
C
L
] ¼ [C
M

Investigation of the Azacrown-Ether Substituted Naphtopyranes
71
2
þ
2 þ
2 þ
and Pb Presence on the Rate Constant
TABLE 1 Effect of the Mg , Ba
ꢀ1
k
d
=s of Dark Ring-Closure Reaction, Relationship Ligand:Metal
Cations ¼ 1:1
2
þ
2 þ
2 þ
Pb
—
Mg
Ba
1a
1b
1c
0.11
0.11
0.15
0.44
0.49
0.19
0.18
0.0016
0.00034
0.12
0.00035
0.00054
in crown ether cavity with carbonyl oxygen atom (Scheme 2). The
effect depends on the nature of metal cations; in case of 1b, it is larger
2
þ
2þ
for Pb
magnitude of k =s (Table 1) was obtained for the complexes of
then for Ba . Substantial difference in the changes of
ꢀ1
d
2þ
mono- and bischromene 1b,c with Ba . The difference is due to in
the complex of 1c with Ba the carbonyl atoms of both chomene units
2
þ
participate in the formation of anion-‘‘capped’’ complex, whereas, the
2
þ
anion- ‘‘capped’’ complex between 1b and Ba is formed by formation
of one coordination bond (Scheme 2). In contrast, for the complexes of
2
þ
ꢀ 1
mono- (1b) and bischromenes (1c) with Pb the magnitudes of k =s
d
are closed to each other, what means the participation of only one
chromene unit of 1c in the formation of anion- ‘‘capped’’ complex with
2
þ
Pb (Scheme 2).
Thus, the study demonstrates that the spectroscopic and kinetic
behaviour of the photomerocyanine isomers of the chromenes 1a–c
is strongly affected by complexation with metal cations. In the photo-
merocyanine form of compounds 1b,c the formation of anion-‘‘capped’’
2
þ
2þ
complexes with Ba and Pb was found.
EXPERIMENTAL
General Remarks
1
H NMR spectra were recorded on Bruker DRX-500 spectrometer
ꢂ
(
working frequency 500.13 MHz, 25 C) using TMS as an internal stan-
dard and CDCl as a solvent. The chemical shifts and the spin-spin
3
coupling constants were determined with an accuracy of 0.01 ppm
and 0.1 Hz, respectively. Mass spectra were obtained using a
Varian MAT 311 A instrument with an ionisation energy of 70 eV.
5
-Bromomethylchromene was prepared according [3], 16-
(
3,3-diphenyl-3H-benzo[f]chromen-5-ylmethyl)-1,4,7,10,13-pentaoxa-16-
aza-cyclooctadecane (1b) was obtained according [4], aza-18-crown-6 and
diaza-18-crown-6 ethers and morpholine were used as received.

7
2
V. Lokshin et al.
Synthesis of Chromenes. General Procedure
Under nitrogen, aza-substituted crown ether or morpholine
(
0.2 mmol), 5-bromomethylchromene (80 mg, 0.2 mmol, for diaza-
crown ether: 160 mg, 0.4 mmol), triethylamine (60 mg, 0.6 mmol, for
diaza-crown ether: 120 mg, 1.2 mmol), and dry THF (25 mL) were
placed into a three-necked flask, and the reaction mixture was
refluxed for 6 h. The product obtained by solvent evaporation was pur-
ified by column chromatography on SiO , eluent benzen-MeOH (10:1)
2
or CH Cl -MeOH (9:1).
2
2
4-(3,3-Diphenyl-3H-Benzo[f]Chromen-5-ylmethyl)-
Morpholine (1a)
ꢂ
1
Yield 57%; mp 150–152 C; H NMR (DMSO-d ): d ¼ 3.3 (m, 4 H,
3
NCH ), 3.62 (m, 4 H, OCH ), 3.74 (s, 2 H, PhCH ), 6.61 (d, J ¼ 9.7 Hz,
2
2
2
1
H, CHA), 7.24 (m, 2 H, ArH), 7.34 (m, 5 H, ArH), 7.47 (m, 2 H, ArH,
CHA), 7.6 (m, 4 H, ArH), 7.75 (s, 1 H, ArH), 7.8 (d, J ¼ 8.0 Hz, 1 H,
þ
ArH), 8.06 (d, J ¼ 8.5 Hz, 1 H, ArH) ppm. MS: m=z ¼ 433 [M ]
(
22%), 348 (37%), 266 (100%), 191 (33%), 165 (23%), 115 (22%),
1
03 (26%), 87 (65%), 69 (51%), 55 (67%). C H NO : calcd. C 83.11,
30 27 2
H 6.28, N 3.23; found C 83.18, H 6.32, N 3.19.
7
1
,16-Bis-(3,3-Diphenyl-3H-Benzo[f]Chromen-5-ylmethyl)-
,4,10,13-Tetraoxa-7,16-Diaza-Cyclooctadecane (1c)
ꢂ
1
Yield 30%; mp 178–182 C; H NMR: d ¼ 2.95 (t, J ¼ 5.8 Hz, 8 H,
NCH ), 3.58 (s, 8 H, OCH ), 3.67 (t, J ¼ 5.8 Hz, 8 H, OCH ), 3.98 (s,
2
2
2
2
7
H, PhCH ), 6.25 (d, J ¼ 10.1 Hz, 1 H, CHA), 7.25 (m, 2 H, ArH),
2
.31–7.37 (m, 6 H, ArH, CHA), 7.44 (m, 1 H, ArH), 7.55 (m, 4 H,
ArH), 7.74 (d, J ¼ 7.8 Hz, 1 H, ArH), 7.85 (s, 1 H, ArH), 7.95 (d,
J ¼ 8.4 Hz, 1 H, ArH) ppm. C H N O -2H O: calcd. C 77.55, H
6
4
62
2
6
2
6
.71, N 2.83; found C 77.48, H 6.55, N 2.69.
UV/Vis Spectroscopy and Kinetic Measurements
UV=Vis absorption spectra were recorded with a Specord ‘‘USB2000’’
of ‘‘Ocean Optics’’ and a Specord ‘‘Cary 50’’. The dark lifetimes of
photomerocyanines of 1a–c were measured using an experimental
setup with a mercury flash lamp. The time resolution was less than
1
ms. The photostationary absorption spectra of merocyanine isomers
were measured with the same setup upon steady-state irradiation of
solutions with glass-filtered 365 nm light of a DRSh-250 high-pressure

Investigation of the Azacrown-Ether Substituted Naphtopyranes
73
mercury lamp. The range of scanning was 400–750 nm with 1 nm
increment.
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(
(
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