One-step synthesis of novel photochemically bifunctional compounds of the spiropyran class

Article abstract of DOI:10.1007/s11172-008-0348-5

The one-step reaction of 5-amino-1,3,3-trimethyl-2-methylideneindoline with two equivalents of different ortho-hydroxy-substituted aromatic aldehydes afforded novel photochemically bifunctional compounds. Molecules of these compounds include two functiona

Full text of DOI:10.1007/s11172-008-0348-5

Russian Chemical Bulletin, International Edition, Vol. 57, No. 11, pp. 2437—2439, November, 2008
2437
Brief Communications
Oneꢀstep synthesis of novel photochemically bifunctional compounds
of the spiropyran class
A. I. Shienok, N. A. Ivashina, L. S. Kol´tsova, and N. L. Zaichenko
N. N. Semenov Institute of Chemical Physics, Russian Academy of Sciences,
4 ul. Kosygina, 119991 Moscow, Russian Federation.
Fax: +7 (499) 137 8284. Eꢀmail: zaina@polymer.chph.ras.ru
The oneꢀstep reaction of 5ꢀaminoꢀ1,3,3ꢀtrimethylꢀ2ꢀmethylideneindoline with two
equivalents of different orthoꢀhydroxyꢀsubstituted aromatic aldehydes afforded novel photoꢀ
chemically bifunctional compounds. Molecules of these compounds include two functionally
different fragments: the substituted azomethine (salicylideneimine or hydroxynaphthylꢀ
methylideneimine) fragment in which intramolecular proton transfer can be induced by elecꢀ
tronic excitation and the spiropyran fragment in which the O—Cspiro bond can dissociate upon
UVꢀlight absorption to form the merocyanine form. No conjugation between the azomethine
and pyran fragments is observed in the initial state of the molecule. The compounds syntheꢀ
sized manifest the photochromic properties and luminescence.
Key words: spiropyrans, photobifunctional compounds, photochromism, luminescence,
1H NMR spectroscopy.
Photochromic compounds that undergo reversible
phototransformations accompanied by the change in color
and other properties are presently intensively investigated
due to their use in optical systems of information detecꢀ
tion and imaging, molecular switchers, transport systems,
dynamic chemisensors and biosensors, etc.1—6 Since posꢀ
sible applications of photochromic compounds are diverse,
the range of demands imposed on their characteristics is
also rather broad.
properties. A molecule of PBC includes two fragment of
different nature in which two different photoprocesses
can occur under irradiation.7—10
Continuing these works, we developed the oneꢀstep
method for synthesis of PBC, whose molecules include
the spiropyran and substituted azomethine fragments.
Molecules of these compounds are photochemically
bifunctional, because the excited state intramolecular
proton transfer (ESIPT) from the phenolic hydroxy group
to the nitrogen atom is possible in the salicylideneimine
or hydroxynaphthylmethylideneimine fragment, whereas
in the spiropyran fragment the O—Cspiro bond can disꢀ
We have recently synthesized for the first time photoꢀ
chemically bifunctional compounds (PBC) based on
spironaphthoxazines in order to extend their functional
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2387—2389, November, 2008.
1066ꢀ5285/08/5711ꢀ2437 © 2008 Springer Science+Business Media, Inc.

2438
Russ.Chem.Bull., Int.Ed., Vol. 57, No. 11, November, 2008
Shienok et al.
I (arb. units)
sociate to form the merocyanine form. In this case, no
conjugation is observed between the azomethine fragꢀ
ment introduced into the indoline part of the PBC molꢀ
ecules and the benzoꢀ or naphthopyran part in the ground
state of the molecule.
Compounds 1—3 were synthesized by the oneꢀstep
reaction of 5ꢀaminoꢀ1,3,3ꢀtrimethylꢀ2ꢀmethylideneꢀ
indoline (4), obtained by an earlier descried procedure,11
with 5ꢀbromoꢀ and 5ꢀnitrosalicylaldehydes (5 and 6) and
1ꢀhydroxyꢀ2ꢀnaphthaldehyde (7), respectively, at the
reactant ratio 1 : 2 (Schemes 1 and 2). This reaction
involves the double condensation of orthoꢀhydroxyꢀsubꢀ
stituted aromatic aldehydes at the enamine group and
the amino group of synthone 4.
2
1.0
0.8
0.6
0.4
3
1
6
5
4
0.2
0
330
380
430
480
530
580
630 680 λ/nm
Fig. 1. Absorption spectra of compounds 1—3 (1—3) and the
open form of compound 2 (4) at 20 °C and the luminescence
spectra of the initial form of compounds 1 (5) and 2, 3 (6) at
Scheme 1
λ
exc = 400 nm in toluene.
The structures of the synthesized compounds were
determined by elemental analysis, NMR spectra, and mass
spectra (see Experimental). Signals in the 1H NMR specꢀ
tra were assigned by comparing the data on the products
and starting aldehydes, as well as the earlier synthesized
PBC.7,10
The absorption spectra of compounds 1—3 in toluene
are shown in Fig. 1. The spectrum of compound 3 is
shifted to the longꢀwavelength region compared to the
spectra of compounds 1 and 2 due to the substitution of
the benzo fragment for the naphtho moiety.
Unlike compounds 1 and 3, compound 2 exhibits the
photochromic properties in toluene solutions at room temꢀ
perature (see Fig. 1), which is due to the stabilization of
the merocyanine form by the nitro group (which is a
strong electron acceptor) in position 6.12 In addition, at
room temperature in toluene solutions compounds 1—3
fluoresce (see Fig. 1): fluorescence with a maximum
at 520—540 nm is observed upon excitation in the region
of 400 nm. The fluorescence excitation spectrum of all
compounds coincides with the longꢀwavelength part of
the absorption spectrum.
R = Br (1), NO (2)
2
Scheme 2
Further the dynamics of the photoprocesses in these
compounds will be studied in detail.
Experimental
NMR spectra were detected on a Bruker WMꢀ400 spectroꢀ
meter at 25 °C in CDCl3. Absorption spectra were recorded on a
Genesysꢀ2 spectrophotometer followed by digital processing.
samples were irradiated with the light from a DRShꢀ1000 lamp
through an interferentional light filter with transmission at 365 nm.
Luminescence spectra were obtained on a Jobin Yvon JY 3
spectrofluorimeter. Mass spectra were measured on a Finnigan
MAT INCOS 50 mass spectrometer.

Spiropyran photobifunctional compounds
Russ.Chem.Bull., Int.Ed., Vol. 57, No. 11, November, 2008 2439
6ꢀBromoꢀ5´ꢀ(5ꢀbromoꢀ2ꢀhydroxybenzylideneimino)ꢀ
1´,3´,3´ꢀtrimethylꢀ1´,3´ꢀdihydrospiro[(2H)ꢀ1ꢀbenzopyranꢀ
2,2´ꢀ(2H)ꢀindole] (1). 5ꢀBromosalicylaldehyde (5) (0.9 g,
4.48 mmol) was added to a solution of 5ꢀaminoꢀ2ꢀmethylideneꢀ
1,3,3ꢀtrimethylindoline (4) (0.4 g, 2.1 mmol) in toluene
(60 mL), and the mixture was refluxed for 4 h with azeotropic
distillation of water. The precipitate was filtered off and washed
with petroleum ether (10 mL). The product was isolated by
chromatography on the plate coated with silica gel using a
chloroform—acetone (19 : 1) mixture as eluent. Compound 1
was obtained (0.96 g, 82%) as brightly yellow crystals with
m.p. 176—177 °C. 1H NMR, δ: 1.20; 1.33 (both s, 3 H each,
C(CH3)2); 2.76 (s, 3 H, NCH3); 5.73 (d, 1 H, H(3); 3J3,4 = 10.2 Hz);
(chloroform—acetone (9 : 1) mixture as eluent), m.p. 206—207 °C.
1H NMR, δ: 1.29; 1.41 (both s, 3 H each, C(CH3)2); 2.79 (s,
3 H, NCH3); 5.82 (d, 1 H, H(3´); 3J3´,4´ = 10.4 Hz); 6.59 (d, 1 H,
3
3
H(7); J6,7 = 8.2 Hz); 7.01 (d, 1 H, H(10´), J9´,10´ = 8.9 Hz);
3
7.13 (d, 1 H, H(3″), J3 ,4 = 9.1 Hz); 7.19 (d, 1 H, H(4),
″
″
4J4,6 = 2.2 Hz); 7.27 (dd, 1 H, H(6), 3J6,7 = 8.2 Hz; 4J4,6 = 2.2 Hz);
3
3
7.33 (ddd, 1 H, H(6´) J5´,6´ = 8.4 Hz; J6´,7´ = 6.9 Hz,
4J6´,8´ = 1.1 Hz); 7.35 (m, 1H, H(6″)); 7.52 (ddd, 1 H, H(7´))
3J7´,8´ = 8.4 Hz; 3J6´,7´ = 6.9 Hz; J5´,7´ = 1.1 Hz; 7.52 (m, 1 H,
3
3
H(7″)); 7.64 (d, 1 H, H(4´); J3´,4´ = 10.4 Hz); 7.65 (d, 1 H,
3
3
H(9´), J9´,10´ = 8.9 Hz); 7.73 (d, 1 H, H(8´), J7´,8´ = 8.3 Hz);
7.78 (dd, 1 H, H(4″), 3J3 ,4″ = 9.1 Hz); 9.34 (s, 1 H, H(α)); 8.05
″
(d, 1 H, H(5´), 3J5´,6´ = 8.4 Hz, 4J5´,7´ = 1.3 Hz); 8.05 (dd, 1 H,
3
3
4
6.61 (d, 1 H, H(8), J7,8 = 9.3 Hz); 6.82 (d, 1 H, H(4);
H(5″), J5 ,6 = 8.1 Hz; J
= 1.3 Hz); 8.12 (dd, 1 H, H(8″),
″
5 ,7
″
″
″
3J3,4 = 10.2 Hz); 7.20 (m, 2 H, H(5), H(7);) 6.54 (d, 1 H, H(7´);
3J7 ,8 = 8.4 Hz; J6 ,8 = 1.1 Hz); 15.97 (br.s, 1 H, OH). MS,
4
3J6´,7´ = 8.1 Hz); 6.90 (d, 1 H, H(3″), J3 ,4″ = 8.8 Hz); 7.11 (d,
m/″z: ″496 [M]+. Fou″nd (%): C, 80.36; H, 5.38; N, 5.50.
″
3
″
1 H, H(4´), 4J4´,6´ = 2.0 Hz); 7.20 (dd, 1 H, H(6´), 3J6´,7´ = 8.1 Hz;
C34H28N2O2. Calculated (%): C, 82.23; H, 5.68; N, 5.64.
4J4´,6´ = 2.0 Hz); 7.39 (dd, 1 H, H(4″), J3 ,4 = 8.8 Hz;
3
″
4J4 ,6 = 2.3 Hz); 7.49 (d, 1 H, H(6´), 4J
= 2.3 ″Hz); 8.56 (s,
This work was financially supported by the Presidium
of the Russian Academy of Sciences (Program No. 8).
″
″
″
″
4 ,6
1 H, H(α)); 13.7 (br.s, 1 H, OH). MS, m/z: 554 [M]+. Found (%):
C, 55.38; H, 3.74; N, 4.91. C26H22Br2N2O2. Calculated (%): C,
56.35; H, 4.00; N, 5.06.
References
5´ꢀ(2ꢀHydroxyꢀ5ꢀnitrobenzylideneimino)ꢀ1´,3´,3´ꢀtrimethylꢀ
6ꢀnitroꢀ1´,3´ꢀdihydrospiro[(2H)ꢀ1ꢀbenzopyranꢀ2,2´ꢀ(2H)ꢀindole]
(2). 5ꢀNitrosalicylaldehyde (6) (1.086 g, 6.5 mmol) was added
to a solution of 5ꢀaminoꢀ2ꢀmethylideneꢀ1,3,3ꢀtrimethylindoline
(4) (0.4 g, 2.1 mmol) in toluene (60 mL), and the mixture was
refluxed for 4 h with azeotropic distillation of water. The
precipitate was filtered off and washed with petroleum ether
(10 mL). The product was isolated by chromatography on the
plate coated with silica gel using a chloroform—acetone (19 : 1)
mixture as eluent. Compound 2 was obtained in a yield of 0.85 g
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1
(80%) as a brickꢀred powder with m.p. 232—233 °C. H NMR,
δ: 1.25; 1.35 (both s, 3 H each, C(CH3)2); 2.80 (s, 3 H, NCH3);
3
5.87 (d, 1 H, H(3); J3,4 = 10.3 Hz); 6.61 (d, 1 H, H(7´);
3
3J6´,7´ = 8.3 Hz); 6.79 (d, 1 H, H(8), J7,8 = 8.5 Hz); 7.06 (d,
1 H, H(4); 3J3,4 = 10.3 Hz); 7.07 (d, 1 H, H(3″), 3J3 ,4″ = 9.2 Hz);
″
4
7.17 (d, 1 H, H(4´), J4´,6´ = 2.2 Hz); 7.26 (dd, 1 H, H(6´),
3J6´,7´ = 8.3 Hz; 4J4´,6´ = 2.2 Hz); 8.02 (d, 1 H, H(5) 4J5,7 = 2.7 Hz);
3
4
8.05 (dd, 1 H, H(7); J7,8 = 8.5 Hz; J5,7 = 2.7 Hz); 8.22 (dd,
1 H, H(4″), 3J3 ,4″ = 9.2 Hz; 4J ″ = 2.7 Hz); 8.37 (d, 1 H, H(6″),
″
″
4 ,6
4J4 ,6 = 2.7 Hz); 8.73 (s, 1 H, H(α)); 14.98 (br.s, 1 H, OH).
MS, ″m/z: 486 [M]+. Found (%): C, 63.87; H, 4.49; N, 11.20.
C26H22N4O6. Calculated (%): C, 64.19; H, 4.56; N, 11.52.
5ꢀ(2ꢀHydroxyꢀ1ꢀnaphthylmethylideneimino)ꢀ1,3,3ꢀtrimethylꢀ
1,3ꢀdihydrospiro[(2H)ꢀindoleꢀ2,2´ꢀ(3H)ꢀnaphtho[2,1ꢀb]pyran]
(3). 1ꢀFormylꢀ2ꢀnaphthol (7) (1.1 g, 6.4 mmol) was added to a
solution of 5ꢀaminoꢀ1,3,3ꢀtrimethylꢀ2ꢀmethylideneindoline (4)
(0.4 g, 2.1 mmol) in toluene (60 mL), and the mixture was
refluxed for 4 h with azeotropic distillation of water. The
precipitate was filtered off and washed with benzene (10 mL)
and petroleum ether (10 mL). The product was isolated by
″
11. D. J. Gale, J. F. K. Wilshire, J. Soc. Dyer. Color., 1971, 581.
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271 [Russ. Chem. Rev., 2005, 74 (Engl. Transl.)].
chromatography on the plate coated with silica gel using
a
chloroform—acetone (19 : 1) mixture as eluent. Compound 3
was obtained in a yield of 0.81 g (78%) as orange crystals, Rf 0.85
Received February 15, 2008;
in revised form May 23, 2008