Photo- and thermochromic spirans 36.* Synthesis, structure and photochromic properties of 7′,7″-{1,4-phenylenedi(methylene)-bis(5- chloro-1,3,3-trimethyl-1,3-dihydrospiro-[indole-2,3′-pyrano[3,2-f] quinolinium])} diiodide

Article abstract of DOI:10.1007/s10593-012-1114-z

A synthesis is reported for a new photochromic indoline bisspiropyran salt containing a quinoline fragment. This compound exists as a racemic mixture. The photochromic properties of this symmetrical bisspiropyran were studied.

Full text of DOI:10.1007/s10593-012-1114-z

Chemistry of Heterocyclic Compounds, Vol. 48, No. 7, October, 2012 (Russian Original Vol. 48, No. 7, July, 2012)
PHOTO- AND THERMOCHROMIC SPIRANS
36.* SYNTHESIS, STRUCTURE AND PHOTOCHROMIC
PROPERTIES OF 7',7"-{1,4-PHENYLENEDI(METHYLENE)-
BIS(5-CHLORO-1,3,3-TRIMETHYL-1,3-DIHYDROSPIRO-
[INDOLE-2,3'-PYRANO[3,2-f]QUINOLINIUM])} DIIODIDE
K. N. Khalanskiy1, Yu. S. Alekseenko2, B. S. Lukyanov1**,
G. S. Borodkin1, and S. O. Bezuglyi2
A synthesis is reported for a new photochromic indoline bisspiropyran salt containing a quinoline
fragment. This compound exists as a racemic mixture. The photochromic properties of this symmetrical
bisspiropyran were studied.
Keywords: indoline bisspiropyran, quinoline, 2H-chromene fragment, photochrome.
The photochromic properties of spiropyrans are defined by the structure and substituents of the hetarene
part of the molecule and the 2H-chromene fragment [2]. In previous work [3], we studied the structure and
photochemical properties of a series of synthesized spiropyrans and their salt analogs containing a quinoline
fragment.
Spirocyclic compounds containing two 2H-chromene fragments in their structure have attracted
particular interest. Irradiation of solutions of these compounds with unfiltered light leads to opening of both
pyran rings [4]. Spiropyran salts [3], containing a chromoxalate complex as the anion, have photomagnetic
properties in the crystalline form [5].
We have synthesized a new symmetrical bisspiropyran salt 2 from previously prepared indoline
spiropyran 1 [6], containing a chlorine atom at C-5 of the indoline part of the molecule and a quinoline fragment
fused with the 2H-pyran ring, by introducing a para-xylene bridge connecting two spiropyran molecules
through the quinoline nitrogen atoms.
_______
*For Communication 35, see [1].
_______
**To whom correspondence should be addressed, e-mail: bluk@ipoc.sfedu.ru.
1Research Institute of Physical and Organic Chemistry, Southern Federal University, 194/2 Stachki Ave.,
344006 Rostov-on-the-Don, Russia.
2Southern Scientific Center, Russian Academy of Sciences, 41 Chekhov St., 344006 Rostov-on-the-Don,
Russia, e-mail: labs811@ipoc.sfedu.ru.
_________________________________________________________________________________________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 1172-1179, July, 2012. Original
article submitted May 5, 2011.
1090
0009-3122/12/4807-1090©2012 Springer Science+Business Media New York

Me
Me
4
7
2'
1'
10' 9'
Cl
3
5
6
8'
3'
CH2Br
+
I–
CH2
N
O
N
7'
Me
6'
5'
CH2Br
NaI, Me2CO
CH2
I–
Me
+
N
7''
O
N
Me
Me
O
Cl
3''
Cl
Me
Me
N
N
2
Me
1
CH2Cl
Me
Me
Cl
I–
+
N
O
N
NaI, Me2CO
C
Me
H2
3
The IR spectrum of iodide 2 has aromatic carbon bond stretching bands at 1580, 1603, and 1645 cm-1,
as well as νC=N bands for the 2H-pyran fragment at 1481 and 1537 cm-1, characteristic for indoline spiropyrans
[7]. The νC–N stretching bands of the indoline fragment appear at 1261 and 933 (C–O), while the νC–O bands of
the 2H-pyran ring appear at 1049 cm-1 and 1109 cm-1 (CAr–O), respectively.
Fig. 1. Two-dimensional 1H-1H COSY correlation spectrum of spiropyran 2.
1091

The 1H NMR signals for the two 3-Me groups of the indoline fragment in iodide 2 are seen at 1.16 and
1.21 ppm, which confirms the presence of an asymmetric carbon atom and, therefore, a spirocyclic structure for
this molecule. The obtained spiropyran 2, which contains an asymmetric spirocarbon atom, exists as a racemic
mixture. This fact was supported by an X-ray diffraction structural investigation of a previously prepared
spiro[1,1,3-trimethylbenzo[e]indolino-2,3'-[3H]pyrano[3,2-f]quinoline], which contains two asymmetric
spiropyran molecules in the crystal, according to X-ray structural analysis [8].
Fig. 2. Heteronuclear single-quantum 1H-13C HSQC correlation spectrum of spiropyran 2.
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The six-proton singlet of the 1-CH3 methyl groups is seen at 2.65 ppm, while the four-proton singlet for
the methylene groups at the quinoline N-7' nitrogen atom is found at 6.27 ppm, which indicates a salt
component in the molecule. The signals for the H-1' and H-2' protons appear as one-proton doublets at 8.00 and
6.15 ppm, respectively (J = 10.7 Hz), which indicates a cis structure for this vinyl fragment of the 2H-pyran
ring. The singlet of the four aromatic protons of the para-xylene bridge at 7.30 ppm confirms the symmetrical
arrangement of the two spirocyclic components in the molecular structure.
Two-dimensional 1H-1H COSY correlation spectrum was recorded (Fig. 1) to confirm the assignment of
the signals in the one-dimensional 1H NMR spectrum.
13
The one-dimensional C NMR spectrum was also recorded, and its signals were assigned on the basis
of the single-quantum 1H-13C heteronuclear HSQC correlation spectrum (Fig. 2). The 13C signals of the methyl
13
groups at C-3 are seen in the C NMR spectrum at 19.5 and 25.1 ppm, the signals for the C-1' and C-2' atoms
are seen at 124.0 and 121.1 ppm, while the signals for the carbon atoms of the methylene bridges at the charged
nitrogen atom and benzene ring connecting the spiropyran fragments are seen at 59.6 and 127.6 ppm,
respectively. These signals perfectly match the signals of the corresponding protons upon their extrapolation in
the 1H-13C HSQC spectrum.
Fig. 3. Distant bond 1H-13C HMBC heteronuclear correlation spectrum of spiropyran 2.
1
1H-13C HMBC (Fig. 3) and H-15N HMBC spectra (Fig. 4) for the heteronuclear correlation of distant
bonds were used to determine the chemical shifts of the carbon atoms not bound to hydrogen atoms and the
nitrogen atoms. The distant bond correlation spectra completely confirmed the structure of the bis-compound
obtained. All the spiropyran atoms not bound to hydrogen atoms were assigned using these spectra. Thus, we
13
found that the C-2,3' spiroatom appearing in the C NMR spectrum at 105.6 ppm has a two-bond correlation
with H-2' and a three-bond correlation with H-1'.
The nitrogen atoms of the indoline and quinoline fragments in the 15N NMR spectrum give signals at 95.6
and 198.2 ppm, respectively. The following picture is observed upon extrapolation of the 1H and 15N NMR spectra
of spiropyran 2 in the distant bond heteronuclear 1H-15N HMBC correlation spectrum (Fig. 4): nitrogen atom N-1
has three-bond correlation with protons H-7 and H-2' and a two-bond correlation with protons of the 1-CH3
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Fig. 4. Distant bond 1H-15N HMBC heteronuclear correlation spectrum of spiropyran 2.
Fig. 5. Photoinduced spectral changes of a solution of spiropyran 2 in acetonitrile upon irradiation with -light
using a UFS-1 light filter (1.5 sec interval). The insert gives an enlargement of the part of the spectrum
undergoing change upon irradiation.
1094

methyl group; the nitrogen atom N-7' has a three-bond correlation with protons H-6' and H-9' as well as two-
bond correlations with proton H-8' and the protons of the methylene bridge –CH2–. The correlations of these
atoms confirm the assignment of the signals in the spectra both for the nitrogen and hydrogen atoms. Thus, the
1H-15N HMBC spectrum completely confirmed the upfield position of the indoline nitrogen atom signal and the
downfield position of the quinoline nitrogen atom, which, in turn, confirms the salt structure of spiropyran 2
with positive charge on the N-7' nitrogen atom.
Thus, all the employed NMR methods allowed a precise establishment of the molecular structure of the
product through a complete assignment of all the carbon, nitrogen, and hydrogen atoms and their extrapolation
relative to each other.
The photochemical data obtained for the bisspiropyran 2 (Fig. 5) differ significantly from such data for
its precursor, spiropyran 1 (Table 1).
The maximum of the long-wavelength absorption band of the open form of spiropyran 2 is shifted
bathochromically, and its lifetime exceeds that of the spiropyran 1 by an order of magnitude. Similar, although
less pronounced behavior is observed when comparing the UV spectra of spiropyran 2 with those of the alkyl-
substituted analog 4 [8] and the benzyl-substituted spiropyran salt 3 (Table 1).
The results of the conducted studies allow to suggest that the symmetrical charged bisspiropyran
synthesized from an indoline spiropyran may be used as a component of photocontrolled salt-forming magnetics
by analogy to 1,3,3,7'-tetramethyl-1,3-dihydrospiro[indole-2,3'-pyrano[3,2-f]quinolinium] iodide [5], which
makes this system worthy of further investigation.
EXPERIMENTAL
The IR spectra were recorded on a Varian Excalibur 3100 FT-IR spectrometer by the frustrated total
1
13
internal reflection method. The H and C NMR spectra were recorded on a Bruker Avance 600 spectrometer
(600 and 150 MHz, respectively) relative to the solvent residual proton signals. The elemental analysis was
carried out by classical microanalysis [9]. The melting points were determined on a Fisher Scientific Fisher-
Johns instrument. The electronic absorption spectra were recorded on an Agilent 8453 spectrophotometer. The
irradiation source was a Newport 200 W mercury lamp using an UFS-1 optical filter.
TABLE 1. Spectral and Kinetic Properties of Compounds 1-4
Compound
Amax, nm
•Amax, M-1cm-1
Bmax, nm
B24, sec
~0.2
6.5
1
289
301
350
272
335
401
247
272
335
401
270
334
397
10140
9650
4480
88250
8640
7340
32430
28130
2480
2120
46430
4520
3810
~530
564
2
3
574
573
5.9
Me
Me
Cl
~538
570
+
N
5.3
I–
N
O
Me
Me
4
1095

7',7"-{1,4-Phenylenedi(methylene)bis(5-chloro-1,3,3-trimethyl-1,3-dihydrospiro[indole-2,3'-pyrano-
[3,2-f]quinolinium])} Diiodide (2). Spiropyran 1 [8] (0.300 g, 0.827 mmol) and 1,4-di(bromomethyl)benzene
(0.109 g, 0.413 mmol) was dissolved in absolute acetone (15 ml) in the presence of sodium iodide (1.24 g, 8.26
mmol), heated at reflux for 4.5 h, and then cooled. The precipitate formed was filtered off and recrystallized
from chloroform. Yield 0.127 g (28%); mp 233-235°С. IR spectrum, , cm-1: 933 (C–O); 1049, 1109 (CAr–О);
1261 (С–N); 1481, 1537 (C=N); 1580, 1603, 1645 (С=С). 1Н NMR spectrum (DMSO-d6), δ, ppm (J, Hz): 1.16
(6H, s, 2(3-CH3)); 1.21 (6H, s, 2(3-CH3)); 2.65 (6H, s, 2(1-CH3)); 6.15 (2H, d, J = 10.7, H-2'); 6.27 (4H, s,
2СН2); 6.63 (2Н, d, J = 8.2, H-7); 7.17 (2H, dd, J = 8.2, J = 2.0, Н-6); 7.22 (2H, s, H-4); 7.30 (4H, s, H Ar);
7.66 (2H, d, J = 9.1, H-10'); 8.00 (2H, d, J = 10.7, H-1'); 8.20 (2H, dd, J = 6.3, J = 9.1, Н-9'); 8.23 (2H, d,
J = 10.0, H-6'); 9.51 (2H, d, J = 6.3, H-8'); 9.62 (2H, d, J = 10.0, H-5'). 13С NMR spectrum (DMSO-d6), δ, ppm:
19.5 (3-CH3); 25.1 (3-CH3); 28.6 (1-CH3); 52.0 (C-3); 59.6 (CH2); 105.6 (C-2,3'); 108.2 (C-7); 113.0 (C-10b');
120.8 (C-9'); 121.1 (C-2'); 122.0 (C-4); 122.6 (C-6'); 123.1 (C-3a); 124.0 (C-1'); 125.9 (C-10'); 127.2 (C-10a');
127.3 (C-6); 127.6 (C-12'); 133.0 (C-6a'); 134.4 (C-11'); 138.0 (C-5); 141.7 (C-5'); 146.1 (C-7a); 147.5 (C-8');
153.4 (C-4a'). 15N NMR spectrum, δ, ppm: 95.6 (N-1); 198.2 (N-7'). Found, %: C 57.68; H 4.28; N 5.26.
C52H46Cl2I2N4O2. Calculated, %: С 57.63; H 4.28; N 5.17.
7'-Benzyl-5-chloro-1,3,3-trimethyl-1,3-dihydrospiro[indole-2,3'-pyrano[3,2-f]quinolinium] Iodide
(3). A solution of the spiropyran 1 [8] (0.06 g, 0.165 mmol) and benzyl chloride (0.02 ml, 0.174 mmol) in
absolute acetone (15 ml) in the presence of sodium iodide (0.52 g, 3.48 mmol) was heated at reflux for 3.5 h
with protection from atmospheric moisture. The reaction mixture was left for 48 h, and the precipitate formed
was filtered off. The desired spiropyran salt 3 was then extracted from the precipitate with acetone (5×10 ml).
The extract was evaporated, and the residue was recrystallized from chloroform. Yield 0.063 g (35%); mp
1
202-205°С. IR spectrum, ν, cm–1: 1100 (CAr–О); 1620, 1600, 1576 (С=С). H NMR spectrum (CDCl3), δ, ppm
(J, Hz): 1.20 (3H, s, 3-CH3); 1.25 (3H, s, 3-CH3); 2.67 (3H, s, 1-CH3); 6.04 (1H, d, J = 10.7, H-2'); 6.44 (2Н, s,
СН2); 7.02 (1Н, d, J = 2.1, Н-7); 7.14 (1Н, d, J = 2.1, Н-6); 7.24 (1Н, s, Н-4); 7.33 (5Н, м, H Ph); 7.46 (1H, d,
J = 9.6, H-6'); 7.75 (1H, d, J = 10.7, H-1'); 8.12 (1H, d, J = 9.6, H-5'); 8.22 (1H, dd, J = 5.7, J = 8.9, H-9'); 9.44
(1H, d, J = 8.9, H-10'); 10.12 (1H, d, J = 5.7, H-8'). Found, %: C 60.07; H 4.40; N 4.73. C29H26СlIN2O.
Calculated, %: C 59.96; H 4.51; N 4.82.
This work was carried out with the financial support of the Russian Foundation for Basic Research
(grant 12-03-90018-Bel-a) and the Grants Council of the President of the Russian Federation (grant NSh
927.2012.3).
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