Structures and photochromic properties of fulgides based on naphtho[1,2-b]furan and benzo[g]indole

Article abstract of DOI:10.1007/s11172-010-0189-x

The novel heterocyclic fulgides, i.e. 3-isopropylidene-4-{1-[5-methoxy-1- (4-methoxy-phenyl)-2-methyl-1H-benzo[g]indol-3-yl]ethylidene}dihydrofuran-2, 5-dione and 3-isopropylidene-4-[1-(1-benzyl-5-methoxy-2-methyl-1H-benzo[g]indol- 3-yl)ethylidene]dihydro

Full text of DOI:10.1007/s11172-010-0189-x

Russian Chemical Bulletin, International Edition, Vol. 59, No. 5, pp. 954—959, May, 2010
954
Structures and photochromic properties of fulgides
based on naphtho[1,2ꢀb]furan and benzo[g]indole
S. K. Balenko,a N. I. Makarova,a V. P. Rybalkin,b E. N. Shepelenko,b L. L. Popova,a
V. V. Tkachev,c S. M. Aldoshin,c A. V. Metelitsa,a V. A. Bren´,a,b and V. I. Minkina,b
aInstitute of Physical and Organic Chemistry, Southern Federal University,
194/2 prosp. Stachki, 344090 RostovꢀonꢀDon, Russian Federation.
Eꢀmail: dubon@ipoc.rsu.ru
bSouthern Scientific Center of Russian Academy of Sciences,
41 ul. Chekhova, 344006 RostovꢀonꢀDon, Russian Federation
cInstitute of Problems of Chemical Physics, Russian Academy of Sciences,
1 prosp. Akad. Semenova, 142432 Chernogolovka, Moscow Region, Russian Federation.
Eꢀmail: sma@icp.ac.ru
The novel heterocyclic fulgides, i.e. 3ꢀisopropylideneꢀ4ꢀ{1ꢀ[5ꢀmethoxyꢀ1ꢀ(4ꢀmethoxyꢀ
phenyl)ꢀ2ꢀmethylꢀ1Hꢀbenzo[g]indolꢀ3ꢀyl]ethylidene}dihydrofuranꢀ2,5ꢀdione and 3ꢀisopropylꢀ
ideneꢀ4ꢀ[1ꢀ(1ꢀbenzylꢀ5ꢀmethoxyꢀ2ꢀmethylꢀ1Hꢀbenzo[g]indolꢀ3ꢀyl)ethylidene]dihydrofuranꢀ
2,5ꢀdione, were prepared and isolated as Eꢀisomers. Photochromism, Eꢀconfiguration, and
high resistance to photocoloration—photobleaching of solutions of these fulgides as well as
3ꢀisopropylideneꢀ4ꢀ[1ꢀ(5ꢀmethoxyꢀ2ꢀmethylnaphtho[1,2ꢀb]furanꢀ3ꢀyl)ethylidene]dihydroꢀ
furanꢀ2,5ꢀdione and 3ꢀisopropylideneꢀ4ꢀ[1ꢀ(5ꢀmethoxyꢀ2ꢀmethylꢀ1ꢀphenylꢀ1Hꢀbenzo[g]indolꢀ
3ꢀyl)ethylidene]dihydrofuranꢀ2,5ꢀdione synthesized previously were shown by Xꢀray diffracꢀ
tion analysis, 1H NMR spectroscopy and electronic absorption spectroscopy. The novel fulgides
show fluorescence and high thermal stability of photogenerated cyclic form. Repeated photoꢀ
coloration—photobleaching is accompanied by reversible photoinduced E—Z isomerization.
Benzo[g]indolyl fulgides are characterized by the longer wavelength absorption of both original
(E) and photoisomeric cyclic (C) forms as compared to naphthofuran fulgide.
Key words: fulgide, naphtho[1,2ꢀb]furan, benzo[g]indol, synthesis, structure, photocromism.
Previously3 we have reported on the photochromic propꢀ
Photochromic heterocyclic fulgides are typically charꢀ
erties and structure of novel Nꢀarylꢀ3ꢀindolylfulgides
giving fluorescent photogenerated isomers that is a necesꢀ
sary condition for applicability of a molecular system in
3D optical data storage materials.4—9 Preliminary results
on the synthesis and photochromism of fulgides 1a,b have
been presented elsewhere10 but will be summarized here.
In order to extend the family of such systems we have
prepared new fulgides of benzo[g]indol series, 1c,d, and
undertook the more detailed study of structure and photoꢀ
chromic properties of fulgides 1a—d.
acterized by thermal stability of a colored form and high
resistance of isomers to repeated photocoloration—photoꢀ
bleaching. These properties make fulgides (whose photoꢀ
chromic mechanism is based on the hexatriene/cycloꢀ
hexadiene interconversion) promising candidates for use
in optical memory devices and as molecular switches.1,2
Results and Discussion
Fulgides 1c,d were synthesized analogously to fulgide
1a (Scheme 1) by reacting diethyl isopropylidene sucꢀ
cinate with the appropriate ketones.10 Fulgide 1b was
obtained following the same scheme by a threeꢀstep proꢀ
cedure with isolation of fulgenate 2b and fulgenic acid 3b,
which provided increasing its yield to 60%.
1: X = O (a), NPh (b), NC6H4OMeꢀ4 (c), NCH2Ph (d)
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 932—938, May, 2010.
1066ꢀ5285/10/5905ꢀ0954 © 2010 Springer Science+Business Media, Inc.

Structures and photochromism of indolylfulgides
Russ.Chem.Bull., Int.Ed., Vol. 59, No. 5, May, 2010
955
Scheme 1
1—3: X = O (a), NPh (b), NC6H4OMeꢀ4 (c), NCH2Ph (d)
IR spectra of fulgides 1c,d as well as 1a,b exhibit charꢀ
acteristic bands at 1750—1800 cm–1 arising from vibraꢀ
tional modes of two exocyclic carbonyl groups of the
0.009, –0.059, 0.046; –0.025, –0.074, 0.061; –0.022,
–0.006, 0.003; –0.014, 0.032, 0.007; –0.024, 0.073,
–0.083 Å, respectively, with furandione and heterocyclic
moieties showing different geometric arrangements in
1a,b,d. In comparing the torsion angles defined by the
atom chain C(11)—C(10)—C(5)—C(4)—C(3)—C(7)—C(9)
(for 1b the latter is C(8)) in 1a,b,d it turns out that the
only angle substantially differing in 1a,b,d is the one
formed by C(10)—C(5) bond. In 1a it is 49.8(3)°, and in
1b,d –137.8(2) and –132.7(3)°, respectively. The arithꢀ
metical means (averaged over 1a,b,d) of the other torsion
1
anhydride ring. In the H NMR spectra of 1c,d, the sigꢀ
nals of ethylidene methyl group (δ 2.75—2.90) and those
originating from 1a,b appear roughly at the same places
thus indicating the Eꢀconfiguration of fulgides 1a—d,
which is spatialy ready for the cyclization process.3,10
The benzyl methylene protons of fulgide 1d are diaꢀ
stereotopic and appear in 1H NMR spectrum as a doublet
of doublets (ABꢀsystem), which is implicative of 1d
chirality.1 On heating the solution of 1d in deuteroꢀ
1
nitrobenzene to 180 °C, the H NMR spectrum shows
neither signal broadening nor coalescence. Hence, the
energy barrier to racemization exceeds 100 kJ mol–1 that
makes dynamic NMR time scale inapplicable for its evaꢀ
luation but allows preparative separation of enantiomers.
The structure of 1a,b,d molecules in the crystalline
state was examined by Xꢀray diffraction (Figs 1—3, reꢀ
spectively).
In molecules 1a,b,d, C(10), C(11), C(13), C(14),
C(15), C(17), C(18), C(19), C(20), C(21), C(22), and
C(23) atoms, as well as O(5) in 1a and N(1) in 1b,d are
displaced from their heterocycle planes by 0.040, –0.037,
0.064; –0.014, 0.020, –0.071; 0.019, –0.011, 0.085;
–0.017, –0.058, 0.035; –0.026, 0.004, –0.057; –0.006,
0.020, –0.037; 0.017, 0.062, –0.044; 0.035, 0.033, –0.010;
C(8)
C(7)
C(12)
O(5)
C(21)
C(23)
O(3)
C(2)
C(20)
C(19)
C(9)
C(11)
C(3)
C(22)
O(1)
C(1)
C(10)
C(13)
C(4)
C(5)
C(18)
C(17)
C(15)
C(14)
O(2)
C(6)
O(4)
C(16)
Fig. 1. Molecular structure of 1a.

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Balenko et al.
O(3)
Table 1. Absorption and fluorescence spectral characteristics of
photoisomers of fulgides 1a—d in toluene at 293 K
C(9)
C(16)
O(4)
C(2)
O(1)
Comꢀ Form
pound
Absorption
Fluorescence, λmax/nm
C(7)
C(3)
λ
ε
Excitaꢀ
tion
Emisꢀ
sion
max
C(15)
/nm /L mol–1 cm–1
C(18)
C(8)
C(1)
C(4)
C(14)
C(13)
1a
1b
1с
1d
Е
С
344
546
10100
—
—
—
648
O(2)
C(17)
C(22)
C(19)
C(20)
340 (S0→S2)
542 (S0→S1)
—
370 (S0→S2)
640 (S0→S1)
—
380 (S0→S2)
650 (S0→S1)
—
375 (S0→S2)
670 (S0→S1)
C(5)
C(10)
Е
С
373
643
10800
—
—
791
C(23)
N(1)
C(6)
C(21)
C(11)
C(24)
Е
С
375
651
11200
—
—
796
C(25)
C(12)
C(26)
Е
С
376
667
10500
—
—
802
C(29)
C(28)
C(27)
Fig. 2. Molecular structure of 1b.
The other bond distances and torsion angles in molꢀ
ecules 1a,b,d are within the range of values normally found
for such compounds.
O(3)
The electron absorption spectra of toluene solutions
of fulgides 1a—d in E form have longꢀwavelength maxima
in the 344 to 376 nm region with molar extinction coefꢀ
ficients at the maxima of 10100—11200 L mol–1 cm–1
(Table 1). With a switch from naphthofuran fulgide (1a)
to benzoindol fulgides (1b—d), the longꢀwavelength maxiꢀ
mum due to E isomer is bathochromically shifted by
29—32 nm. The effect of substituents at benzoindol nitroꢀ
gen on the absorbance of 1b—d Eꢀisomers is insignificant.
The open ring Eꢀconfigured fulgides 1a—d are not
fluorescing in toluene at 293 K.
Irradiation of solutions of 1a—d at the wavelengths
of Eꢀisomer absorption causes their coloration with the
attendant appearance in the absorption spectra of bands
at 450—750 nm which are characteristic of the closed
C forms (Scheme 2 and Fig. 4; see also Table 1)11.
Photogenerated cyclic C form of naphthofuran fulgide
1a has the longꢀwavelength maximum at 546 nm, whereas
C isomers of benzoindolyl fulgides 1b—d are absorbing at
longer wavelengths (see Table 1). In the substituted
fulgides, the longꢀwavelength band shows a progressive
bathochromic shift as the electron donating ability of subꢀ
stituents at benzoindol nitrogen is increased in the series
Ph, C6H4OMeꢀ4, CH2Ph.
C(2)
O(1)
C(8)
C(1)
C(3)
C(16)
O(4)
C(7)
O(2)
C(4)
C(9)
C(15)
C(17)
C(22)
C(18)
C(19)
C(14)
C(13)
C(23)
C(5)
C(6)
C(10)
C(11)
C(20)
C(21)
N(1)
C(25)
C(24)
C(12)
Fig. 3. Molecular structure of 1d.
angles in this structural fragment are 10.0 (0.6), 40.7 (1.2),
1.5 (1.6)° (parentheses are maximum deviation values).
The observed structural similarity is apparently due to
that furandione (including C(7), C(5), and C(6) atoms)
and benzoindol (including O(4), C(16), C(12)) moieties
are both conjugated so that the only possible rotation is
about C(10)—C(5) bond. Interatomic distance between
C(7) and C(11) carbons which form chemical bond on
photocyclization is 3.54, 4.38, and 4.22 Å for crystalline
1a,b,d, respectively.
The closed ring C fulgides 1a—d demonstrate high
thermal stability: the reverse dark reaction C→E in
toluene does not occur within 72 h at 293 K.
Irradiation of colored solutions of 1a—d with visible
light (at 546 nm for 1a and at 578 nm for 1b—d) results in
their bleaching, with the decrease in absorbance of C form
being not accompanied by the recovery of original (before
UVꢀirradiation) absorption spectrum (see Fig. 4, curve 3).

Structures and photochromism of indolylfulgides
Russ.Chem.Bull., Int.Ed., Vol. 59, No. 5, May, 2010
957
Scheme 2
At the same time, the following repeated colorationꢀ
bleaching cycles characteristically reproduce spectral patꢀ
terns of colored and colorless forms. Such spectral transꢀ
formations are due to the presence in irradiated solutions
of 1a—d of Z isomers as evidenced by H NMR spectra
of fulgides 1b,d in deuterotoluene recorded after conꢀ
1b,d, involving reversible E—Z photoisomerization and
E—C photocyclization.
The prolonged irradiation of fulgides 1a—d in soluꢀ
tions was found not to result in their complete conversion
to a colored state. This is apparently due to overlapping of
absorbance bands corresponding to S0→S2 transitions of
C isomers and the bands originating from S0→S1 transiꢀ
tions of E and Z isomers. Under conditions affording the
reverse C→E photoreaction and E→Z photoisomerization
characteristic of fulgides, UVꢀirradiation transforms the
system into photostationary mixture containing E, Z, and
C isomeric forms at a ratio determined, in particular, by
the wavelength of UVꢀexcitation. The following complete
bleaching of solution on visibleꢀlight irradiation leads to
a binary mixture of E and Z isomers.
Fulgides 1a—d are resistant to photocoloration—photoꢀ
bleaching cycling. Ten cycles have not led to decrease in
the optical density of solution at 640 nm as exemplified by
the cyclic changing of the optical density of fulgide 1b
in toluene (Fig. 5) at the longꢀwavelength maximum of
absorption of C isomer under consecutive photoexcitation
at 365 and 578 nm. As can be seen, while approaching
1
secutive irradiations at 365 and 578 nm.
1
The H NMR spectra of starting fulgides 1b,d display
the set of signals characteristic of E isomers. Their irraꢀ
diation with visible light at 365 nm results in a photoꢀ
stationary state so that the spectrum of irradiated soluꢀ
tions contains methyl proton resonances produced by all
three isomeric forms, namely open (E and Z) and closed
(C); the aromatic proton signals of these isomers are also
observed in the weak field. After further visibleꢀlight irraꢀ
diation (578 nm) of fulgides 1b,d in solutions, their
1H NMR spectra showed proton signals from only open
ring E and Z isomers, with the content of E isomers enꢀ
hanced by the value equal to the loss of C isomer in the
ternary mixture. Thus, the features of 1H NMR and
electron absorption spectra compare favorably with the
aboveꢀproposed photoinduction mechanism for fulgides
A
A
1.4
0.20
578 nm
1.2
1.0
0.8
0.18
0.16
0.14
0.12
0.10
0.08
0.06
0.04
0.02
0.6
3
0.4
2
1
0.2
365 nm
1
0
0
2
3
4
5
6
7
Number of cycles
300
400
500
600
700
800 λ/nm
Fig. 4. Absorption spectra of fulgide 1b in toluene (4•10–5 mol L–1
before irradiation (1), in photostationary state under visibleꢀ
light irradiation at 365 nm (2), and after further irradiation at
578 nm (3).
)
Fig. 5. Optical density dynamics of fulgide 1b in toluene
(2.8•10–5 mol L–1, 273 K) at λ
= 640 nm (the absorbꢀ
obs
ance maximum of C isomer) under coloration (λ = 365 nm,
irr
τ = 10 min)—bleaching (λirr = 578 nm, τ = 10 min) cycling.

958
Russ.Chem.Bull., Int.Ed., Vol. 59, No. 5, May, 2010
Balenko et al.
(20 mL). The reaction mixture was stirred for 5 h at 30 °C. The
solvent was removed in vacuo (waterꢀjet pump). The residue was
treated with 10% hydrochloric acid (30 mL), precipitated
monoethyl ether 2b was filtered off and recrystallized from
toluene. Yield 3.1 g (63%), colorless crystals, m.p. 222—223 °C.
Found (%): C, 74.94; H, 6.42; N, 2.70. C31H31NO5. Calculated
(%): C, 74.83; H, 6.28; N, 2.81. IR, ν/cm–1: 1760; 1790 (C=О).
1H NMR (CDCl3), δ: 0.67 (t, 3 H, Me, J = 7.1 Hz); 1.98, 2.11,
2.19, 2.21 (all s, 3 H each, Me); 3.73—3.94 (m, 2 H, CH2); 4.00
(s, 3 H, OMe); 6.85 (s, 1 H, Ar); 6.97—7.67 (m, 8 H, Ar); 8.30
(d, 1 H, Ar, J = 8.4 Hz); 11.24 (br.s, 1 H, OH).
2ꢀ[1ꢀ(5ꢀMethoxyꢀ2ꢀmethylꢀ1ꢀphenylꢀ1Hꢀbenzo[g]indolꢀ
3ꢀyl)ethylidene]ꢀ3ꢀ(1ꢀmethylethylidene)butanedioic acid (3b).
Ester 2 (3.1 g) was placed in a flask fitted with a reflux condenser
and treated with 10% methanolic KOH (10 mL). The mixture
was refluxed for 4 h, cooled, diluted with water and acidified
with 10% HCl (30 mL). Precipitated dicarboxylic acid was
filtered off and airꢀdried. Yield 3 g (98%), colorless crystals,
m.p. 245—246 °C. Found (%): C, 72.45; H, 6.22; N, 3.45.
C27H29NO5. Calculated (%): C, 71.58; H, 6.01; N, 3.34.
IR, ν/cm–1: 1750; 1780 (C=O). 1H NMR (CDCl3), δ: 1.98,
2.07, 2.10, 2.24 (all s, 3 H each, Me); 3.95 (s, 3 H, OMe); 6.80—
photostationary state, the system shows no tendency for
photodegradation over 10 cycles.
The fact that is highly important for practical use of
fulgides has been established, namely, photogenerated
closed ring C isomers of fulgides 1a—d are fluorescent.
The maximum absorption of the C form is in the 648 to
802 nm region. Electron donating substituents at nitrogen
atom shift the absorption spectra of C form of 1b—d to the
longer wavelengths (see Table 1). Fluorescence excitation
spectra are well consistent with the absorption of C isoꢀ
mers (see Table 1). Apart from assistance in assignment of
the observed fluorescence to C form, excitation spectra
provide useful information on the location of individual
absorption bands corresponding to S0→S2 transitions of
closed ring isomers. Photochromic efficiency is relatively
low with the quantum yields not exceeding 0.01, which is
largely due to existence of a competing quenching chanꢀ
nel desactivating electron excitation through C→E photoꢀ
isomerization.
Both original (fulgide solution) and irradiated mateꢀ
rial (subjected to up to 10 photocolorationꢀphotobleaching
7.70 (m,
9 H, Ar); 8.16 (d, 1 H, Ar, J = 8.4 Hz);
11.60—11.80 (br.s, 2 H, ОH).
1
cycles) contained no impurities detectable by H NMR,
(3E)ꢀIsopropylideneꢀ4ꢀ[1ꢀ(5ꢀmethoxyꢀ2ꢀmethylꢀ1ꢀphenylꢀ
1Hꢀbenzo[g]indolꢀ3ꢀyl)ethylidene]dihydrofuranꢀ2,5ꢀdione (Eꢀ1b).
Diacid 3b (3 g) was dissolved in acetyl chloride (1.5 mL) with
stirring. The solvent was removed in vacuo. Yield 2.9 g (98%),
yellow crystals, m.p.. 182—184 °C (from MeCN). Found (%):
C, 77.01; H, 5.29; N, 3.01. C29H25NO4. Calculated (%):
C, 77.14; H, 5.58; N, 3.10. IR, ν/cm–1: 1800; 1750. 1H NMR
(tolueneꢀd7), δ: 0.80, 1.69, 1.95, 2.87 (all s, 3 H each, Me); 3.66
(s, 3 H, OMe); 6.67 (s, 1 H, Ar); 6.77—7.23 (m, 8 H, Ar); 8.55
(d, 1 H, Ar, J = 8.4 Hz).
(3Z)ꢀIsopropylideneꢀ4ꢀ[1ꢀ(5ꢀmethoxyꢀ2ꢀmethylꢀ1ꢀphenylꢀ
1Hꢀbenzo[g]indolꢀ3ꢀyl)ethylidene]dihydrofuranꢀ2,5ꢀdione (Zꢀ1b).
Product Zꢀ1b was prepared in a NMR tube as a mixture with
Eꢀ1b and Cꢀ1b isomers by irradiation of a solution of fulgide
Eꢀ1b in deuterotoluene (2.4•10–2 mol L–1) with light at 365 nm
for 4 h. 1H NMR (tolueneꢀd7), δ: 1.43, 2.12, 2.15, 2.17 (all s,
3 H each, Me); 3.64 (s, 3 H, OMe); 6.67—7.28 (m, 9 H, Ar);
8.61 (d, 1 H, Ar, J = 8.4 Hz).
UV, and luminescence spectroscopy.
In conclusion, new photochromic benzo[g]indolꢀ3ꢀyl
fulgides have been synthesized, which possess resistance
to photocoloration—photobleaching cycling and high
thermal stability of photogenerated cyclic form. Repeated
photocoloration—photobleaching is accompanied by reꢀ
versible photoinduced E to Z isomerization. Both original
(E) and cyclic (C) forms of benzoindolyl fulgides 1b—d
absorb at longer wavelengths compared to the naphthoꢀ
furan fulgide 1a. The channels of decay of the excitation
energy of cyclic isomers C include radiative decay.
Experimental
Electron absorption spectra were recorded on a Cary 100
(Varian) spectrophotometer, and fluorescence spectra on a
Varian Eclipce spectrofluorometer. The solutions were irradiated
using a DRShꢀ250 mercury lamp equipped with a set of
interference filters for isolating the lines of mercury spectrum.
Irradiation intensity at 365 and 578 nm was 2.9•1016 and
2.6•1016 quantum s–1, respectively. IR spectra were measured
from compound suspensions in the Nujol on a Specord 75 IR
spectrometer, and 1H NMR spectra were recorded with a Varian
Unityꢀ300 instrument (300 MHz) using HMDS as an external
standard.
(3E)ꢀIsopropylideneꢀ4ꢀ[1ꢀ(5ꢀmethoxyꢀ2ꢀmethylnaphthoꢀ
[1,2ꢀb]furanꢀ3ꢀyl)ethylidene]dihydrofuranꢀ2,5ꢀdione (1a) was
prepared by the known procedure.10 Yield 32%, m.p. 199—200 °C.
2ꢀ[1ꢀ(5ꢀMethoxyꢀ2ꢀmethylꢀ1ꢀphenylꢀ1Hꢀbenzo[g]ꢀ
indolꢀ3ꢀyl)ethylidene]ꢀ3ꢀ(1ꢀmethylethylidene)butanedioic acid
1ꢀmonoethyl ester (2b). A suspension of NaH (0.7 g, 0.03 mol)
in THF (10 mL) was stirred at room temperature while adding a
solution of 3ꢀacetylꢀ5ꢀmethoxyꢀ2ꢀmethylꢀ1ꢀphenylbenzo[g]ꢀ
indol (2.8 g, 0.01 mol), isopropylidene diethyl succinate (2.8 g,
0.013 mol), and diisopropylamine (1.4 mL, 0.01 mol) in THF
5ꢀMethoxyꢀ7,11,11,11aꢀtetramethylꢀ12ꢀphenylꢀ11a,12ꢀ
dihydroꢀ8Hꢀbenzo[a]furo[3,4ꢀh]carbazoleꢀ8,10(11H)ꢀdione
(Cꢀ1b). Prepared in a NMR tube as a mixture with Eꢀ1b and
Zꢀ1b isomers by irradiation of a solution of fulgide Eꢀ1b in
deuterotoluene (2.4•10–2 mol L–1) with light (λ = 365 nm)
irr
for 6 h followed by purification from isomers using preparative
column chromatography (Silpearl, chloroform). M.p. 241—243
°C. 1H NMR (tolueneꢀd8), δ: 1.05, 1.36, 1.42, 2.49 (all s, 3 H
each, Me); 3.53 (s, 3 H, OMe); 6.67—7.28 (m, 9 H, Ar); 8.32 (d,
1 H, Ar, J = 8.4 Hz).
4ꢀ[1ꢀ(1ꢀBenzylꢀ5ꢀmethoxyꢀ2ꢀmethylꢀ1Hꢀbenzo[g]indolꢀ
3ꢀyl)ethylidene]ꢀ(3E)ꢀisopropylidenedihydrofuranꢀ2,5ꢀdione
(Eꢀ1d). Prepared according to the literature procedure10 from
3ꢀacetylꢀ1ꢀbenzylꢀ5ꢀmethoxyꢀ2ꢀmethylbenzo[g]indol (4 g,
0.012 mol). Yield 28%, yellowꢀbrown crystals, m.p.. 231—233 °C
(from toluene). Found (%): C, 76.61; H, 6.12; N, 3.19.
C29H27NO4. Calculated (%): C, 76.80; H, 6.00; N, 3.09.
1
IR, ν/cm–1: 1800; 1750 (C=О). H NMR (C6D5NO2), δ: 1.20,
2.27, 2.43, 3.11 (all s, 3 H each, Me); 4.21 (s, 3 H, OMe); 5.91,

Structures and photochromism of indolylfulgides
Russ.Chem.Bull., Int.Ed., Vol. 59, No. 5, May, 2010
959
Table 2. Crystallographic data and Xꢀray diffraction experiment
parameters for compounds 1a,b,d
Xꢀray diffraction analysis. 3D set of intensities further used
to obtain cell parameters for crystals 1a,b,d was measured on
a Bruker Pꢀ4 automated diffractometer (MoꢀKαꢀradiation,
graphite monochromator). Details of crystal data, data collection
and structure refinement are listed in Table 2. The structures
were solved by the direct method (SHELXSꢀ97)12 and refined
using the fullꢀmatrix leastꢀsquares on F2 (SHELXLꢀ97)12 in
anisotropic approximation for nonꢀhydrogen atoms. The hydroꢀ
gen atoms were located in a difference Fourier maps. Coordinates
and isotropic thermal parameters for H atoms were obtained by
leastꢀsquares refinement in the riding mode.12
Parameter
1a
1b
1d
Molecular formula
C23H20O5 C29H25NO4 С30H27NO4
M
376–.39
P1
7.1200(16)
11.580(2)
12.927(3)
451–.50
465–.53
Space group
a/Å
b/Å
P1
P1
9.625(2) 10.4470(25)
9.970(2) 10.7750(25)
13.255(3) 11.6720(31)
c/Å
α/deg
β/deg
γ/deg
65.460(21) 70.380(15) 78.250(28)
89.530(24) 87.280(16) 72.410(29)
81.630(30) 83.400(16) 75.590(31)
This work was financially supported by the Federal
Targeted Programme “Scientific and ScientificꢀPedagogiꢀ
cal Personnel of the Innovative Russia in 2009ꢀ2013”,
(Contract No. 02.740.11.0456), the Russian Foundation
for Basic Research (Project No. 06ꢀ03ꢀ32988), and the
Foundation of the President of the Russian Federation
(Federal Program for the Support of Leading Scientific
Schools, Grant NShꢀ3233.2010.3).
3
V/Å
Z
957.6(4)
2
1190.1(4)
2
1201.3(6)
2
dcalc/g cm–3
1.305
0.092
1.413
0.084
1.287
0.085
μ/cm–1
θ range/deg
Number of measured
reflections
Number of reflections
with I ≥ 2σ(I)
Number of refined
parameters
R1 (I ≥ 2σ(I))
R
1.96—25.00 1.16—23.05 1.85—25.00
3190
2452
253
3727
3278
308
3752
2664
317
References
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Izv. Akad. Nauk, Ser. Khim., 2008, 1409 [Russ. Chem. Bull.,
Int. Ed., 2008, 57, 1435].
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molecules, 2002, 35, 9377.
5. Y. C. Liang, A. S. Dvornikov, P. M. Rentzepis, Res. Chem.
Intermed., 1998, 24, 905.
6. A. V. Metelitsa, O. T. Lyashik, S. M. Aldoshin, O. A. Kozina,
N. V. Volbushko, E. A. Medyantseva, M. I. Knyazhanskii,
V. I. Minkin, L. O. Atovmyan, Khim. Geterotsikl. Soedin.,
1990, 33 [Chem. Heterocycl. Compd. (Engl. Transl.), 1990,
26, 28].
7. Y. Yokoyama, T. Tanaka, T. Yamane, Y. Kurita, Chem.
Lett., 1991, 20, 1125.
8. Y. C. Liang, A. S. Dvornikov, P. M. Rentzepis, Opt.
Commun., 2003, 223, 61.
9. Y. Yokoyama, M. J. Kose, Photochem. Photobiol. A: Chem.,
2004, 166, 9.
10. S. K. Balenko, V. P. Rybalkin, E. N. Shepelenko, L. L.
Popova, N. I. Makarova, A. V. Metelitsa, V. A. Bren´,
V. I. Minkin, Zh. Organ. Khim., 2006, 42, 1869 [Russ. J.
Org. Chem. (Engl. Transl.), 2006, 42, 1861].
11. A. Santiago, R. S. Becker, J. Am. Chem. Soc., 1968, 3654.
12. G. M. Sheldrick, SHELXLꢀ97, Program for Refinement of
Crystal Structures, University of Göttingen (Germany), 1997.
0.0438
0.0612
1.059
0.0397
0.0451
1.042
0.0570
0.0851
1.080
wR2
GOF
6.40 (ABꢀsystem, 2 H, CH2, JA,B = 18.2 Hz); 7.11 (s, 1 H, Ar);
7.24—8.58 (m, 9 H, Ar).
(3Z)ꢀ[1ꢀ(1ꢀBenzylꢀ5ꢀmethoxyꢀ2ꢀmethylꢀ1Hꢀbenzo[g]indolꢀ
3ꢀyl)ethylidene]ꢀ4ꢀisopropylidenedihydrofuranꢀ2,5ꢀdione
(Zꢀ1d). Prepared in a NMR tube as a mixture with Eꢀ1d and
Cꢀ1d isomers under irradiation of a solution of fulgide Eꢀ1d
in deuteronitrobenzene (2.4•10–2 mol L–1) with visible light
(λ = 365 nm) over 4 h with heating. 1H NMR (C6D5NO2,
irr
tolueneꢀd8), δ: 2.19, 2.59, 2.67, 2.68 (all s, 3 H each, Me);
4.18 (s, 3 H, OMe); 5.90—6.20 (m, 2 H, CH2); 7.07—8.52 (m,
10 H, Ar).
12ꢀBenzylꢀ5ꢀmethoxyꢀ7,11,11,11aꢀtetramethylꢀ11a,12ꢀ
dihydroꢀ8Hꢀbenzo[a]furo[3,4ꢀh]carbazoleꢀ8,10(11H)ꢀdione
(Cꢀ1d). Prepared in a NMR tube as a mixture with Eꢀ1d and
Zꢀ1d isomers under irradiation of a solution of fulgide Eꢀ1d
in deuteroꢀnitrobenzene (2.4•10–2 mol L–1
) with light
(λ = 365 nm) over 6 h. 1H NMR (C6D5NO2), δ: 1.35, 1.63,
irr
1.80, 2.78 (all s, 3 H each, Me); 4.14 (s, 3 H, OMe); 5.91,
6.40 (ABꢀsystem, 2 H, CH2, JA,B = 19.0 Hz); 7.07—8.52 (m,
10 H, Ar).
(3E)ꢀIsopropylideneꢀ4ꢀ{1ꢀ[5ꢀmethoxyꢀ1ꢀ(4ꢀmethoxyphenyl)ꢀ
2ꢀmethylꢀ1Hꢀbenzo[g]indolꢀ3ꢀyl]ethylidene}dihydrofuranꢀ
2,5ꢀdione (Eꢀ1c). Prepared by the known procedure10 from
3ꢀacetylꢀ5ꢀmethoxyꢀ1ꢀ(4ꢀmethoxyphenyl)2ꢀmethylbenzo[g]ꢀ
indol (4 g, 0.012 mol). Yield 43%, yellow crystals, m.p. 202—
203 °C (from toluene). Found (%): C, 76.61; H, 6.12; N, 3.19.
C29H27NO5. Calculated (%): C, 76.80; H, 6.00; N, 3.09.
IR, ν/cm–1: 1800; 1750. 1H NMR (CDCl3), δ: 1.10, 2.05, 2.19,
2.88 (all s, 3 H each, Me); 3.96, 3.98 (both s, 3 H each, OMe);
6.66 (s, 1 H, Ar); 7.00—7.40 (m, 7 H, Ar); 8.32 (d, 1 H, CH,
J = 8.35 Hz).
Received August 15, 2008;
in revised form November 13, 2009