Synthesis and photoluminescent properties of conjugated aryl-vinyl dioctyl 2,6-dimethylbenzofuro[5,6-b]furan-3,7-dicarboxylate derivatives

Article abstract of DOI:10.1016/j.dyepig.2013.07.006

The synthesis of highly fluorescent conjugated benzodifuran aryl-vinyl systems, containing four double bonds and at least four phenyl rings, is described. The ethyl groups of diethyl 2,6-dimethylbenzofuro[5,6-b]furan-3,7- dicarboxylate, obtained by the Michael type condensation of p-benzoquinone and ethyl acetoacetate, were replaced by octyl groups via the transesterification reaction to improve the desired product solubility in common organic solvents. The dioctyl ester was brominated and used for the Wittig reaction with stilbene aldehydes, obtained by the Heck reaction of 4-bromobenzaldehyde and an appropriate styrene. The products, obtained in 48-92% yield, exhibit the UV-Vis fluorescence with high quantum yields, 58-69%.

Full text of DOI:10.1016/j.dyepig.2013.07.006

Dyes and Pigments 99 (2013) 803e811
Contents lists available at ScienceDirect
Dyes and Pigments
journal homepage: www.elsevier.com/locate/dyepig
Synthesis and photoluminescent properties of conjugated arylevinyl
dioctyl 2,6-dimethylbenzofuro[5,6-b]furan-3,7-dicarboxylate
derivatives
,
a
a
a
Mariusz J. Bosiak a , Marcin Rakowiecki , Katarzyna J. Or1owska , Dariusz Ke˛dziera ,
*
Jörg Adams b
a
ꢀ
Faculty of Chemistry, Nicolaus Copernicus University, 7 Gagarin Street, 87-100 Torun, Poland
b Institute of Physical Chemistry, Clausthal University of Technology, Arnold-Sommerfeld-Str. 4, 38678 Clausthal-Zellerfeld, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
The synthesis of highly fluorescent conjugated benzodifuran arylevinyl systems, containing four double
bonds and at least four phenyl rings, is described. The ethyl groups of diethyl 2,6-dimethylbenzofuro[5,6-
b]furan-3,7-dicarboxylate, obtained by the Michael type condensation of p-benzoquinone and ethyl
acetoacetate, were replaced by octyl groups via the transesterification reaction to improve the desired
product solubility in common organic solvents. The dioctyl ester was brominated and used for the Wittig
reaction with stilbene aldehydes, obtained by the Heck reaction of 4-bromobenzaldehyde and an
appropriate styrene. The products, obtained in 48e92% yield, exhibit the UVeVis fluorescence with high
quantum yields, 58e69%.
Received 3 May 2013
Received in revised form
4 July 2013
Accepted 5 July 2013
Available online 16 July 2013
Keywords:
Benzodifuran
Fluorescence
Ó 2013 Elsevier Ltd. All rights reserved.
The Heck reaction
The Wittig reaction
Heteroaryl compounds
OLED
1. Introduction
2. Experimental
Fluorescent compounds have attracted much interest because of
their potential applications in flat panel displays [1e4] and solid
state lighting [5e8]. The main advantages of organic light-emitting
diodes (OLEDs) based on fluorescent materials are their low-power
consumption, high brightness and high contrast of full color flat
panel displays. Among the small molecule fluorescent materials,
the most efficient emitters are distyrylarylenes [9e18] and oligo-
phenyl vinyl compounds [19e24]. Benzodifuran (BDF) derivatives,
due to their fluorescent properties, represent an important and
little explored group of heterocyclic compounds that can be used
for OLED applications. Recently, the first examples of benzodifuran
small molecule materials [25e32], and polymers [33,34] have been
reported. We also described arylevinyl benzodifuran systems of
excellent fluorescent quantum yields [35,36]. Herein, the synthesis
and fluorescence characterization of highly fluorescent benzodi-
furans containing an extended arylevinyl system are described.
2.1. Materials and general methods
Experiments with air and moisture sensitive materials were
carried under argon atmosphere. Glassware was oven dried for
several hours, assembled hot, and cooled in a stream of argon. Silica
gel 60, Merck 230e400 mesh, was used for preparative column
flash chromatography. Analytical TLC was performed using Merck
TLC Silica gel 60 F254 0.2 mm plates. Reagents were commercially
available from SigmaeAldrich, Merck or Fluorochem and were used
without further purification. Diethyl 2,6-dimethylbenzofuro[5,6-b]
furan-3,7-dicarboxylate (2) [35] and montmorillonite-supported
PdCl2 catalyst [37] were prepared according to literature pro-
cedures. Solvents were purchased from POCh Gliwice, Poland and
SigmaeAldrich. Toluene and p-xylene were distilled from sodium
benzophenone ketyl prior to use, carbon tetrachloride, dichloro-
methane, chloroform, diethyl ether, and 2-propanol were used
without further purification. 1H and 13C NMR spectra were recorded
on a Bruker Advance III 400 MHz or Bruker Advance III 700 MHz
instrument at ambient temperature. Chemical shifts are reported in
* Corresponding author. Tel.: þ48 512038649; fax: þ48 56 6542477.
E-mail address: bosiu@chem.umk.pl (M.J. Bosiak).
parts per million (d scale), coupling constants (J values) are listed in
0143-7208/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.dyepig.2013.07.006

804
M.J. Bosiak et al. / Dyes and Pigments 99 (2013) 803e811
Hertz. IR spectra were recorded on Mattson FTIR Genesis II spec-
trometer with ATR attachment. Melting points were determined
with a Büchi SMP 32 and Barnstead-Thermolyne Mel-Temp II
apparatus in open capillaries and are uncorrected. Elemental ana-
lyses were performed at Elementary Analysensysteme GmbH Var-
ioMACRO CHN analyzer.
distilled off, methanol (200 mL) was added and the mixture was
cooled to ꢁ20 ꢂC, and left at this temperature for 72 h. The yellow
precipitate was collected by filtration and crystallized from
chloroform: methanol (3:2) to afford 4 (13.33 g, 58%) as a pale
yellow solid. mp ¼ 132e136 ꢂC. 1H NMR (CDCl3, 700 MHz);
d
ppm: 0.87 (t, J ¼ 7.0 Hz, 6H, 2 ꢀ CH3), 1.26e1.35 (m, 12H,
6 ꢀ CH2), 1.36e1.40 (m, 4H, 2 ꢀ CH2), 1.46e1.51 (m, 4H, 2 ꢀ CH2),
1.84 (dt, J ¼ 15.4 Hz, J ¼ 7.0 Hz, 4H, 2 ꢀ CH2), 4.40 (t, J ¼ 7.0 Hz, 4H,
2 ꢀ CH2), 4.98 (s, 4H, 2 ꢀ CH2), 8.08 (s, 2H, 2 ꢀ CHAr). 13C NMR
2.1.1. Spectroscopic measurements
Dichloromethane (spectrometric grade from Aldrich) was
employed as solvent for absorption and fluorescence measure-
ments. UV/Vis absorption spectra were recorded on a UNICAM
(CDCl3, 100 MHz);
d
ppm: 14.03 (2 ꢀ CH3), 21.25 (2 ꢀ CH2), 22.61
(2 ꢀ CH2), 26.10 (2 ꢀ CH2), 28.68 (2 ꢀ CH2), 29.15 (2 ꢀ CH2), 29.21
(2 ꢀ CH2), 31.75 (2 ꢀ CH2), 65.32 (2 ꢀ CH2), 104.33 (2 ꢀ CH), 111.10
(2 ꢀ C), 124.84 (2 ꢀ C), 151.84 (2 ꢀ C), 160.48 (2 ꢀ C), 163.14
(2 ꢀ C). IR (ATR)nmax cmꢁ1: 2951, 2920, 2850, 1707, 1596, 1464,
1420, 1397, 1351, 1259, 1186, 1086, 1050, 935, 880, 826, 786, 722,
703. Anal. Calcd. for C30H40Br2O6: C, 54.89; H, 6.14. Found: C,
55.12; H, 6.11.
Helios-a spectrophotometer in a 1-cm quartz cell, in comparison to
solvent blank. Emission spectra were obtained on a Hitachi F-7000
Fluorescence Spectrophotometer and on a JASCO FP-8500 spec-
trometer. The quantum yield was determined using fluorescein in
0.1 M NaOH as reference. Excitation wavelength for all materials
was 460 nm. The concentration of fluorescein and the analyzed
substances were set in a way that the absorbance at 460 nm was
low enough to avoid the inner filter effect. A reference value of
0.9 for the fluorescein quantum yield was used. The fluorescence
lifetime was determined using a time-correlated single-photon
counting setup with a Maestro spectrum analyzer (EG&G Ortec, Oak
Ridge, USA) and a pulsed LED (376 nm, PicoQuant GmbH, Berlin,
Germany) with a pulse width of less than 1.5 ns (FWHM). All
fluorescence light above 406 nm was detected using a low-pass
filter. The decay traces were analyzed assuming a single exponen-
tial decay function.
2.2.3. (3,7-Bis(octyloxycarbonyl)benzofuro[5,6-b]furan-2,6-diyl)
bis(methylene)bis(triphenylphosphonium) bromide (5)
Dioctyl
2,6-bis(bromomethyl)benzo[1,2-b:4,5-b0]difuran-3,7-
dicarboxylate (4) (12.47 g, 19.0 mmol) and triphenylphosphine
(14.93 g, 57.0 mmol) were refluxed in toluene (200 mL) for 30 min.
The mixture was cooled to room temperature, precipitated salt was
collected by filtration, washed with diethyl ether (4 ꢀ 60 mL) and
dried in vacuum to afford 5 (22.30 g, 99%) as a green-yellow
powder. mp ¼ 88e90 ꢂC. 1H NMR (CDCl3, 700 MHz);
d ppm: 0.88
(t, J ¼ 7.0 Hz, 6H, 2 ꢀ CH3), 1.28e1.32 (m, 20H, 10 ꢀ CH2), 1.64 (t,
J ¼ 7.0 Hz, 4H, 2 ꢀ CH2), 4.09 (t, J ¼ 7.0 Hz, 4H, 2 ꢀ CH2), 6.49 (d,
J ¼ 15.4 Hz, 4H, 2 ꢀ CH2), 7.59e7.61 (m, 14H, 14 ꢀ CHAr), 7.74 (t,
J ¼ 7.0 Hz, 6H, 6 ꢀ CHAr), 7.82e7.86 (m, 12H, 12 ꢀ CHAr). 13C NMR
2.2. Synthesis of the compounds
2.2.1. Dioctyl 2,6-dimethylbenzo[1,2-b:4,5-b0]difuran-3,7-
dicarboxylate (3)
(CDCl3, 100 MHz);
d
ppm: 14.12 (2 ꢀ CH3), 22.64 (2 ꢀ CH2), 25.87
2,6-Dimethylbenzofuro[5,6-b]furan-3,7-dicarboxylate
(2)
(2 ꢀ CH2), 26.43 (2 ꢀ CH2), 28.55 (2 ꢀ CH2), 29.13 (2 ꢀ CH2), 29.17
(2 ꢀ CH2), 31.82 (2 ꢀ CH2), 65.31 (2 ꢀ CH2), 104.18 (2 ꢀ CH), 113.60
(C), 113.68 (C), 117.20 (2 ꢀ C), 117.70 (2 ꢀ C), 123.35 (2 ꢀ C), 130.11
(6 ꢀ CH), 130.25 (6 ꢀ CH), 134.06 (6 ꢀ CH), 134.17 (6 ꢀ CH), 135.24
(6 ꢀ CH), 151.71 (2 ꢀ C), 154.79 (2 ꢀ C), 154.91 (2 ꢀ C), 163.03
(2 ꢀ C). 2953, 2924, 2852, 1709, 1676, 1599, 1435, 1425, 1398, 1256,
1181, 1148, 1107, 1073, 1055, 997, 961, 858, 782, 742, 728, 705, 687.
Anal. Calcd. for C66H70Br2O6P2: C, 67.12; H, 5.97. Found: C, 66.71; H,
5.92.
(16.52 g, 50.0 mmol), 1-octanol (150 mL), anhydrous potassium
phosphate (10.61 g, 50.0 mmol) and tert-butylammonium bromide
(2.0 g, 6.2 mmol) were refluxed in DeaneStark apparatus for 9 h.
The mixture was cooled to room temperature, dichloromethane
(200 mL) and water (400 mL) were added and the layers were
separated. The aqueous layer was extracted with dichloromethane
(3 ꢀ 50 mL), combined organic layers were dried over anhydrous
magnesium sulfate and the solvent was removed on a rotary
evaporator. Methanol (200 mL) was added and the mixture was left
at ꢁ20 ꢂC for 16 h. The precipitated product was filtered and
crystallized from methanol: ethyl acetate (1:1), yielding 19.45 g
(78%), of white powder. mp ¼ 84e86 ꢂC. 1H NMR (CDCl3, 700 MHz);
2.3. General procedure for styrenes
A mixture of methyltriphenylphosphonium iodide (20.0 mmol)
in dry THF (150 mL) was cooled to ꢁ78 ꢂC and n-butyllithium
(2.5 M in hexanes) (8 mL, 20.0 mmol) was added dropwise. The
mixture was allowed to worm to room temperature, stirred for
additional 30 min and cooled again to ꢁ78 ꢂC. Aldehyde
(20.0 mmol) in THF (10 mL) was added dropwise, mixture was
allowed to worm to room temperature and stirred at this tem-
perature for 2 h. Resulting precipitate was filtered off on a sintered
funnel, TBME (350 mL) was added to the filtrate, and the mixture
was stirred for additional 10 min and filtered again. The solvent
was removed on rotary evaporator and the product was purified
by flash chromatography.
d
ppm: 0.87 (t, J ¼ 7.0 Hz, 6H, 2 ꢀ CH3), 1.25e1.33 (m, 12H, 6 ꢀ CH2),
1.34e1.39 (m, 4H, 2 ꢀ CH2), 1.45e1.49 (m, 4H, 2 ꢀ CH2), 1.81 (dt,
J ¼ 14.7 Hz, J ¼ 7.0 Hz, 4H, 2 ꢀ CH2), 2.78 (s, 6H, 2 ꢀ CH3), 4.35 (t,
J ¼ 7.0 Hz, 4H, 2 ꢀ CH2), 7.93 (s, 2H, 2 ꢀ CHAr). 13C NMR (CDCl3,
175 MHz);
d
ppm: 14.07 (2 ꢀ CH3), 14.74 (2 ꢀ CH3), 22.64 (2 ꢀ CH2),
26.15 (2 ꢀ CH2), 28.81 (2 ꢀ CH2), 29.18 (2 ꢀ CH2), 29.24 (2 ꢀ CH2),
31.78 (2 ꢀ CH2), 65.54 (2 ꢀ CH2), 102.81 (2 ꢀ CH), 109.14 (2 ꢀ C),
123.92 (2 ꢀ C),151.20 (2 ꢀ C), 164.51 (2 ꢀ C),164.57 (2 ꢀ C). IR (ATR)
nmax cmꢁ1: 2953, 2923, 2853, 1709, 1674, 1599, 1422, 1399, 1337,
1255, 1181, 1148, 1073, 1003, 961, 857, 801, 781, 706, 634. Anal.
Calcd. for C30H42O6: C, 72.26; H, 8.49. Found: C, 72.54; H, 8.52.
2.2.2. Dioctyl 2,6-bis(bromomethyl)benzo[1,2-b:4,5-b0]difuran-3,7-
dicarboxylate (4)
2.3.1. 1-Fluoro-4-vinylbenzene
Prepared from 4-fluorobenzaldehyde and purified by flash
chromatography, acetone: petroleum ether (2:8). Pale yellow oil,
To a solution of 3 (18.43 g, 35 mmol) in carbon tetrachloride
(250 mL), N-bromosuccinimide (7.46 g, 41.8 mmol) and AIBN
(0.5 g) were added and the mixture was refluxed for 4 h. Another
portion of N-bromosuccinimide (7.46 g, 41.8 mmol) and AIBN
(0.5 g) were added and the mixture was stirred under reflux for
an additional 20 h. Most of the carbon tetrachloride (200 mL) was
56%. 1H NMR (CDCl3, 400 MHz);
d ppm: 5.18e5.21 (m, 1H, CH),
5.62e5.67 (m, 1H, CH), 6.66 (dd, J ¼ 10.8 Hz, J ¼ 17.2 Hz, 1H, CH),
6.97e7.01 (m, 2H, 2 ꢀ CHAr), 7.33e7.37 (m, 2H, 2 ꢀ CHAr). 13C NMR
(CDCl3, 100 MHz);
d ppm: 113.50 (CH2), 115.28 (CH), 115.49 (CH),
127.68 (CH), 127.76 (CH), 132.91 (C), 135.68 (CH), 161.23 (C).

M.J. Bosiak et al. / Dyes and Pigments 99 (2013) 803e811
805
2.3.2. 1-Nitro-4-vinylbenzene
dried with anhydrous magnesium sulfate. The solvent was
removed on a rotary evaporator and the crude product was
vacuum dried.
Prepared from 4-nitrobenzaldehyde and purified by flash
chromatography, ethyl acetate: petroleum ether (1:1). Colorless
oil, 46%. 1H NMR (CDCl3, 400 MHz);
d
ppm: 5.47 (d, J ¼ 11.2 Hz,
1H, CH), 5.90 (dd, J ¼ 17.6 Hz, J ¼ 0.8 Hz, 1H, CH), 6.75 (dd,
J ¼ 17.6 Hz, J ¼ 10.8 Hz, 1H, CH), 7.49e7.52 (m, 2H, 2 ꢀ CHAr),
2.4.1. (E)-4-Styrylbenzaldehyde (6)
Prepared from styrene (0.69 g, 6.5 mmol) and crystallized from
8.14e8.17 (m, 2H, 2 ꢀ CHAr). 13C NMR (CDCl3, 100 MHz);
d
ppm:
toluene. 1.08 g (96%) of a white microcrystalline product,
119.58 (CH2), 124.95 (2 ꢀ CH), 127.81 (2 ꢀ CH), 135.99 (CH), 144.82
mp ¼ 108e110 ꢂC, lit. [38] mp ¼ 107e109 ꢂC. 1H NMR (CDCl3,
(C), 148.21 (C).
400 MHz);
d
ppm: 7.13 (d, J ¼ 16.4 Hz, 1H, CH), 7.25 (d, J ¼ 16.4 Hz,
1H, CH), 7.30e7.32 (m, 1H, CHAr), 7.35e7.39 (m, 2H, 2 ꢀ CHAr), 7.53
(d, J ¼ 7.2 Hz, 2H, 2 ꢀ CHAr), 7.64 (d, J ¼ 8.4 Hz, 2H, 2 ꢀ CHAr), 7.85 (d,
J ¼ 8.4 Hz, 2H, 2 ꢀ CHAr), 9.98 (s, 1H, CHO). 13C NMR (CDCl3,
2.3.3. 1-(Trifluoromethyl)-4-vinylbenzene
Prepared from 4-(trifluoromethyl)benzaldehyde and purified by
flash chromatography, acetone: petroleum ether (2:8). Pale yellow
100 MHz);
d
ppm: 126.93 (3 ꢀ CH), 127.34 (CH), 128.51 (CH), 128.84
oil, 37%. 1H NMR (CDCl3, 700 MHz);
d
ppm: 5.37 (d, J ¼ 10.5 Hz, 1H,
(2 ꢀ CH), 130.25 (2 ꢀ CH), 132.21 (2 ꢀ CH), 135.34 (C), 136.56 (C),
CH), 5.83 (d, J ¼ 17.5 Hz, 1H, CH), 6.73 (dd, J ¼ 10.5 Hz, J ¼ 17.5 Hz,
1H, CH), 7.48 (d, J ¼ 8.4 Hz, 2H, 2 ꢀ CHAr), 7.56 (d, J ¼ 8.4 Hz, 2H,
143.44 (C), 191.62 (CHO).
2 ꢀ CHAr). 13C NMR (CDCl3, 175 MHz);
d
ppm: 116.54 (CH2), 122.44
2.4.2. (E)-4-(4-Nitrostyryl)benzaldehyde (7)
(C), 125.55 (CH), 125.65 (CH), 126.48 (2 ꢀ CH), 129.74 (C), 135.72
Prepared from 1-nitro-4-vinylbenzene (0.500 g, 3.35 mmol),
yielding 0.84 g (99%), of an orange crystalline product. Crystallized
from toluene, mp ¼ 195e197 ꢂC, lit. [39] mp ¼ 211e212 ꢂC. 1H NMR
(CH), 141.02 (C).
2.3.4. 1,2,3-Trimethoxy-5-vinylbenzene
(CDCl3, 700 MHz); d ppm: 7.28 (s, 1H, CH), 7.28 (s, 1H, CH), 7.66 (d,
Prepared from 3,4,5-trimethoxybenzaldehyde and purified by
flash chromatography, acetone: petroleum ether (1:9). Colorless oil,
J ¼ 8.4 Hz, 2H, 2 ꢀ CHAr), 7.69 (d, J ¼ 8.4 Hz, 2H, 2 ꢀ CHAr), 7.90 (d,
J ¼ 8.4 Hz, 2H, 2 ꢀ CHAr), 8.24 (d, 2H, J ¼ 8.4 Hz, 2 ꢀ CHAr), 10.01 (s,
59%. 1H NMR (CDCl3, 700 MHz);
d
ppm: 3.83 (s, 3H, CH3), 3.86 (s, 6H,
1H, CHO). 13C NMR (CDCl3, 100 MHz);
127.33 (2 ꢀ CH), 127.47 (2 ꢀ CH), 129.56 (CH), 130.30 (2 ꢀ CH),
131.79 (CH), 136.16 (C), 142.05 (C), 142.94 (C), 147.32 (C), 191.47
(CHO).
d
ppm: 124.23 (2 ꢀ CH),
2 ꢀ CH3), 5.19 (d, J ¼ 10.5 Hz, 1H, CH), 5.64 (dd, J ¼ 17.5 Hz,
J ¼ 0.7 Hz, 1H, CH), 6.62 (dd, J ¼ 17.5 Hz, J ¼ 10.5 Hz, 1H, CH), 6.62 (s,
2H, 2 ꢀ CHAr). 13C NMR (CDCl3, 175 MHz);
d
ppm: 55.93 (2 ꢀ CH3),
60.75 (CH3), 103.12 (2 ꢀ CH), 113.16 (CH2), 133.29 (C), 136.63 (CH),
137.94 (C), 153.21 (2 ꢀ C).
2.4.3. (E)-4-(4-Methylstyryl)benzaldehyde (8)
Prepared from 1-methyl-4-vinylbenzene (1.20 g, 10.2 mmol)
and crystallized from toluene, yielding 2.05 g (90%) of pale yellow,
crystalline product, mp ¼ 189e193 ꢂC, lit. [40] mp ¼ 182.1e182.8 ꢂC.
2.3.5. Methyl(4-vinylphenyl)sulfane
Prepared from 4-(methylthio)benzaldehyde and purified by
flash chromatography, acetone: petroleum ether (2:8). Colorless oil,
1H NMR (CDCl3, 700 MHz);
d ppm: 2.36 (s, 3H, CH3), 7.08 (d,
42%. 1H NMR (CDCl3, 400 MHz);
d
ppm: 2.47 (s, 3H, CH3), 5.19 (dd,
J ¼ 16.1 Hz, 1H, CH), 7.18 (d, J ¼ 7.0 Hz, 2H, 2 ꢀ CHAr), 7.22 (d,
J ¼ 16.8 Hz, 1H, CH), 7.43 (d, J ¼ 7.0 Hz, 2H, 2 ꢀ CHAr), 7.62 (d,
J ¼ 7.0 Hz, 2H, 2 ꢀ CHAr), 7.84 (d, J ¼ 7.7 Hz, 2H, 2 ꢀ CHAr), 9.97 (s,1H,
J ¼ 10.9 Hz, J ¼ 0.9 Hz, 1H, CH), 5.69 (dd, J ¼ 17.6 Hz, J ¼ 0.8 Hz, 1H,
CH), 6.65 (dd, J ¼ 17.6 Hz, J ¼ 10.8 Hz, 1H, CH), 7.18e7.20 (m, 2H,
2 ꢀ CHAr), 7.30e7.32 (m, 2H, 2 ꢀ CHAr). 13C NMR (CDCl3, 100 MHz);
CHO). 13C NMR (CDCl3, 400 MHz);
d ppm: 21.36 (CH3), 126.34 (CH),
d
ppm: 16.86 (CH3), 113.22 (CH2), 126.62 (4 ꢀ CH), 134.57 (C), 136.20
126.79 (2 ꢀ CH), 126.87 (2 ꢀ CH), 129.59 (2 ꢀ CH), 130.26 (2 ꢀ CH),
132.19 (CH), 133.80 (C), 135.17 (C), 138.64 (C), 143.69 (C), 191.67
(CHO).
(CH), 137.99 (C).
2.3.6. 2-Vinylnaphthalene
Prepared from 2-naphthaldehyde and purified by flash chro-
matography, acetone: petroleum ether (1:9). White powder, 80%,
2.4.4. (E)-4-(4-Methoxystyryl)benzaldehyde (9)
Prepared from 1-methoxy-4-vinylbenzene (1.61 g, 12.0 mmol)
and crystallized from toluene, yielding 1.34 g (47%), of pale yellow
crystalline product, mp ¼ 148e150 ꢂC, lit. [41] mp ¼ 146e148 ꢂC.
mp ¼ 60e63 ꢂC. 1H NMR (CDCl3, 400 MHz);
d ppm: 5.32 (dd,
J ¼ 10.8 Hz, J ¼ 0.8 Hz, 1H, CH), 5.86 (dd, J ¼ 17.6 Hz, J ¼ 0.8 Hz, 1H,
CH), 6.87 (dd, J ¼ 17.6 Hz, J ¼ 10.8 Hz, 1H, CH), 7.41e7.46 (m, 2H,
2 ꢀ CHAr), 7.62 (dd, J ¼ 8.4 Hz, J ¼ 1.6 Hz,1H, CHAr), 7.73 (s,1H, CHAr),
1H NMR (CDCl3, 400 MHz);
d ppm: 3.83 (s, 3H, CH3), 6.90 (d,
J ¼ 8.4 Hz, 2H, 2 ꢀ CHAr), 6.99 (d, J ¼ 16.0 Hz, 1H, CH), 7.20 (d,
J ¼ 16.0 Hz, 1H, CH), 7.47 (d, J ¼ 8.4 Hz, 2H, 2 ꢀ CHAr), 7.61 (d,
J ¼ 8.0 Hz, 2H, 2 ꢀ CHAr), 7.84 (d, J ¼ 8.0 Hz, 2H, 2 ꢀ CHAr), 9.96 (s,
7.78e7.80 (m, 3H, 3 ꢀ CHAr). 13C NMR (CDCl3, 100 MHz);
d ppm:
114.21 (CH2), 123.23 (CH), 125.95 (CH), 126.28 (CH), 126.42 (CH),
127.71 (CH), 128.10 (CH), 128.20 (CH), 133.21 (C), 133.61 (C), 135.07
(C), 136.99 (CH).
1H, CHO). 13C NMR (CDCl3, 100 MHz);
d ppm: 55.34 (CH3), 114.30
(2 ꢀ CH), 125.17 (CH), 126.60 (2 ꢀ CH), 128.26 (2 ꢀ CH), 129.34 (C),
130.26 (2 ꢀ CH), 131.79 (CH), 135.00 (C), 143.86 (C), 160.01 (C),
191.61 (CHO).
2.4. General procedure for stilbene aldehydes (6e15)
In a Schlenk flask, equipped with a reflux condenser and
flushed with argon, montmorillonite-supported PdCl2 catalyst
[37] (0.01 g for every 5 mmol of 4-bromobenzaldehyde), 4-
bromobenzaldehyde (1 equiv.), sodium acetate (2 equiv.) and
DMF (2 mL for every 1 mmol of 4-bromobenzaldehyde) were
stirred for 5 min under argon atmosphere. An appropriate
styrene (1 equiv.) in DMF (1 mL for every 5 mmol) was added in
one portion and mixture was refluxed until substrates dis-
appeared on TLC (w3 h). The mixture was cooled to room
temperature, poured into water and extracted with dichloro-
methane. Combined organic layers were washed with brine and
2.4.5. (E)-4-(4-Fluorostyryl)benzaldehyde (10)
Prepared from 1-fluoro-4-vinylbenzene (1.46 g, 12.0 mmol),
yielding 1.11 g (41%) of a creamy-white powder, mp ¼ 120e122 ꢂC,
lit. [38] mp ¼ 119.9e120.6 ꢂC. 1H NMR (CDCl3, 400 MHz);
d ppm:
7.02e7.08 (m, 3H, 2 ꢀ CHAr, CH), 7.20 (d, J ¼ 16.4 Hz, 1H, CH), 7.50
(dd, J ¼ 8.4 Hz, J ¼ 5.2 Hz, 2H, 2 ꢀ CHAr), 7.62 (d, J ¼ 8.4 Hz, 2H,
2 ꢀ CHAr), 7.85 (d, J ¼ 8.4 Hz, 2H, 2 ꢀ CHAr), 10.01 (s, 1H, CHO). 13
C
NMR (CDCl3, 100 MHz);
d ppm: 115.84 (CH), 116.07 (CH), 126.94
(CH), 127.14 (2 ꢀ CH), 128.56 (2 ꢀ CH), 130.32 (CH), 130.92 (C),
132.84 (2 ꢀ CH), 135.47 (C), 143.34 (C), 162.91 (C, d, J ¼ 248.8 Hz),
191.65 (CHO).

806
M.J. Bosiak et al. / Dyes and Pigments 99 (2013) 803e811
2.4.6. (E)-4-(4-Chlorostyryl)benzaldehyde (11)
were stirred for 10 min at rt. An appropriate aldehyde (2 mmol) was
added and the mixture was refluxed for 3e5 h (TLC). After cooling
the mixture was diluted with water (30 mL) and extracted with
dichloromethane (3 ꢀ 50 mL). The combined organic layers were
washed with brine (2 ꢀ 30 mL) and dried with anhydrous mag-
nesium sulfate. The solvent was removed on a rotary evaporator
and the crude product was vacuum dried and purified using flash
chromatography (dichloromethane). The obtained E/Z mixture of
isomers was refluxed for 3 h in p-xylene (5 mL) with a small crystal
of iodine. Cooled, filtered, washed with diethyl ether (2 ꢀ 5 mL),
and dried under vacuum.
Prepared from 1-chloro-4-vinylbenzene (1.41 g, 10.2 mmol),
yielding 2.45 g (99%) of a pale yellow crystalline product. Crystal-
lized from toluene, mp ¼ 108e110 ꢂC. 1H NMR (CDCl3, 700 MHz);
d
ppm: 7.10 (d, J ¼ 16.1 Hz, 1H, CH), 7.19 (d, J ¼ 16.1 Hz, 1H, CH), 7.34
(d, J ¼ 8.0 Hz, 2H, 2 ꢀ CHAr), 7.46 (d, J ¼ 8.0 Hz, 2H, 2 ꢀ CHAr), 7.63 (d,
J ¼ 8.0 Hz, 2H, 2 ꢀ CHAr), 7.86 (d, J ¼ 8.0 Hz, 2H, 2 ꢀ CHAr), 9.98 (s,1H,
CHO). 13C NMR (CDCl3, 100 MHz);
d
ppm: 126.98 (2 ꢀ CH), 127.94
(CH), 128.06 (2 ꢀ CH), 129.06 (2 ꢀ CH), 130.29 (2 ꢀ CH),130.82 (CH),
134.18 (C), 135.07 (C), 135.51 (C), 143.04 (C), 191.57 (CHO). Anal.
Calcd. for C15H11ClO: C, 74.23; H, 4.57. Found: C, 74.52; H, 4.60.
2.4.7. (E)-4-(4-(Trifluoromethyl)styryl)benzaldehyde (12)
2.5.1. Dioctyl 2,6-bis((E)-4-((E)-styryl)styryl)benzo[1,2-b:4,5-b0]
difuran-3,7-dicarboxylate (16)
Prepared from 1-(trifluoromethyl)-4-vinylbenzene (1.72 g,
10.0 mmol), and crystallized from toluene, yielding 1.08 g (39%) of a
yellow crystalline product, mp ¼ 119e121 ꢂC, lit. [42] mp ¼ 128e
Prepared from aldehyde 6, 0.75 g (86%) of an orange solid,
mp ¼ 204e206 ꢂC. 1H NMR (CDCl3, 700 MHz);
d ppm: 0.88 (t,
130 ꢂC.1HNMR (CDCl3, 400 MHz);
d
ppm: 7.20 (d, J ¼ 16.4 Hz,1H, CH),
J ¼ 7.0 Hz, 6H, 2 ꢀ CH3), 1.31e1.32 (m, 8H, 4 ꢀ CH2), 1.35e1.38 (m,
4H, 2 ꢀ CH2), 1.44 (m, 4H, 2 ꢀ CH2), 1.56 (m, 4H, 2 ꢀ CH2), 1.91 (m,
4H, 2 ꢀ CH2), 4.44 (t, J ¼ 7.0 Hz, 4H, 2 ꢀ CH2), 7.10 (d, J ¼ 16.2 Hz,
2H, 2 ꢀ CH), 7.15 (d, J ¼ 16.2 Hz, 2H, 2 ꢀ CH), 7.25e7.27 (m, 2H,
2 ꢀ CHAr), 7.34e7.37 (m, 4H, 4 ꢀ CHAr), 7.51e7.53 (m, 8H,
8 ꢀ CHAr), 7.59e7.61 (m, 6H, 4 ꢀ CHAr, 2 ꢀ CH), 7.91 (d, J ¼ 16.2 Hz,
2H, 2 ꢀ CH), 8.01 (s, 2H, 2 ꢀ CHAr). 13C NMR (CDCl3, 100 MHz);
7.26 (d, J ¼ 16.4 Hz,1H, CH), 7.62 (s, 4H, 4 ꢀ CHAr), 7.66 (d, J ¼ 8.4 Hz,
2H, 2 ꢀ CHAr), 7.88 (d, J ¼ 8.4 Hz, 2H, 2 ꢀ CHAr), 10.0 (s, 1H, CHO). 13
C
NMR (CDCl3,100 MHz);
(2 ꢀ CH), 127.21 (2 ꢀ CH), 129.83 (CH), 129.94 (C), 130.27 (2 ꢀ CH),
130.49 (CH), 135.82 (C), 139.99 (2 ꢀ C), 142.59 (C), 191.53 (CHO).
d
ppm: 125.79 (q, J ¼ 3.8 Hz, 2 ꢀ CH),126.99
2.4.8. (E)-4-(4-(Methylthio)styryl)benzaldehyde (13)
d
ppm: 14.13 (2 ꢀ CH3), 22.70 (2 ꢀ CH2), 26.34 (2 ꢀ CH2), 28.91
Prepared
from
methyl(4-vinylphenyl)sulfane
(1.50
g,
(2 ꢀ CH2), 29.28 (2 ꢀ CH2), 29.37 (2 ꢀ CH2), 31.86 (2 ꢀ CH2), 64.89
(2 ꢀ CH2), 103.14 (2 ꢀ CH), 109.25 (2 ꢀ C), 115.33 (2 ꢀ CH), 125.64
(2 ꢀ C), 126.65 (4 ꢀ CH), 126.99 (4 ꢀ CH), 127.90 (2 ꢀ CH), 127.99
(4 ꢀ CH), 128.01 (2 ꢀ CH), 128.76 (4 ꢀ CH), 129.54 (2 ꢀ CH), 135.26
(2 ꢀ CH), 135.39 (2 ꢀ C), 135.45 (2 ꢀ C), 137.14 (2 ꢀ C), 138.35
(2 ꢀ C), 151.73 (2 ꢀ C), 160.94 (2 ꢀ C). IR (ATR)nmax cmꢁ1: 3026,
2948, 2920, 2849, 1697, 1622, 1596, 1565, 1549, 1448, 1417, 1397,
1375, 1354, 1281, 1248, 1206, 1193, 1154, 1058, 961, 857, 812, 749,
720, 703, 688. Anal. Calcd. for C60H62O6: C, 81.97; H, 7.11. Found: C,
82.50; H, 7.05.
10.0 mmol) and crystallized from toluene, yielding 1.22 g (48%), of a
creamy-white crystalline product, mp ¼ 148e150 ꢂC. 1H NMR
(CDCl3, 700 MHz);
d
ppm: 2.50 (s, 3H, CH3), 7.08 (d, J ¼ 16.1 Hz, 1H,
CH), 7.20 (d, J ¼ 16.8 Hz, 1H, CH), 7.23 (d, J ¼ 8.4 Hz, 2H, 2 ꢀ CHAr),
7.45 (d, J ¼ 8.4 Hz, 2H, 2 ꢀ CHAr), 7.62 (d, J ¼ 8.4 Hz, 2H, 2 ꢀ CH), 7.85
(d, J ¼ 8.4 Hz, 2H, 2 ꢀ CHAr), 9.97 (s, 1H, CHO). 13C NMR 15.94 (CH3),
126.83 (2 ꢀ CH), 126.97 (CH), 127.06 (2 ꢀ CH), 127.71 (2 ꢀ CH),
130.26 (2 ꢀ CH), 131.79 (CH), 133.58 (C), 135.46 (C), 139.62 (C),
143.73 (C), 191.91 (CHO).
2.4.9. (E)-4-(3,4,5-Trimethoxystyryl)benzaldehyde (14)
2.5.2. Dioctyl 2,6-bis((E)-4-((E)-4-nitrostyryl)styryl)benzo[1,2-
b:4,5-b0]difuran-3,7-dicarboxylate (17)
Prepared from 1,2,3-trimethoxy-5-vinylbenzene (1.94 g,
10.0 mmol) and crystallized from toluene, yielding 1.37 g (46%), of a
creamy-yellow powder, mp ¼ 158e160 ꢂC. 1H NMR (CDCl3,
Prepared from aldehyde 7, 0.89 g (92%) of a red solid, mp ¼ 210e
212 ꢂC. 1H NMR (CDCl3, 700 MHz),
d
ppm: 0.88 (t, J ¼ 7.0 Hz, 6H,
400 MHz);
d
ppm: 3.86 (s, 3H, CH3), 3.91 (s, 6H, 2 ꢀ CH3), 6.75 (s, 2H,
2 ꢀ CH3), 1.32e1.38 (m, 8H, 4 ꢀ CH2), 1.44e1.45 (m, 4H, 2 ꢀ CH2),
1.52e1.57 (m, 4H, 2 ꢀ CH2), 1.90e1.94 (m, 4H, 2 ꢀ CH2), 4.45 (t,
J ¼ 7.0 Hz, 4H, 2 ꢀ CH2), 7.15 (d, J ¼ 16.3 Hz, 2H, 2 ꢀ CH), 7.23 (d,
J ¼ 16.3 Hz, 2H, 2 ꢀ CH), 7.54 (d, J ¼ 8.0 Hz, 4H, 4 ꢀ CHAr), 7.57 (d,
J ¼ 16.2 Hz, 2H, 2 ꢀ CH), 7.61 (d, J ¼ 14.0 Hz, 8H, 8 ꢀ CHAr), 7.92 (d,
J ¼ 16.2 Hz, 2H, 2 ꢀ CH), 8.01 (s, 2H, 2 ꢀ CHAr), 8.20 (d, J ¼ 8.4 Hz,
2 ꢀ CHAr), 7.02 (d, J ¼ 16.0 Hz, 1H, CH), 7.17 (d, J ¼ 16.0 Hz, 1H, CH),
7.63 (d, J ¼ 8.0 Hz, 2H, 2 ꢀ CHAr), 7.85 (d, J ¼ 8.0 Hz, 2H, 2 ꢀ CHAr),
9.98 (s, 1H, CHO). 13C NMR (CDCl3, 100 MHz);
d ppm: 56.19
(2 ꢀ CH3), 61.00 (CH3), 104.10 (2 ꢀ CH), 126.77 (CH), 126.80
(2 ꢀ CH), 130.26 (2 ꢀ CH), 132.16 (CH), 132.24 (C), 135.30 (C), 138.76
(C), 143.34 (C), 153.51 (2 ꢀ C), 191.56 (CHO). Anal. Calcd. for
4H, 4 ꢀ CHAr). 13C NMR (CDCl3, 100 MHz);
d
ppm: 14.14 (2 ꢀ CH3),
C
18H18O4: C, 72.47; H, 6.08. Found: C, 72.58; H, 6.05.
22.70 (2 ꢀ CH2), 26.34 (2 ꢀ CH2), 28.91 (2 ꢀ CH2), 29.28 (2 ꢀ CH2),
29.36 (2 ꢀ CH2), 31.86 (2 ꢀ CH2), 64.95 (2 ꢀ CH2), 103.24 (2 ꢀ CH),
109.61 (2 ꢀ C), 115.99 (2 ꢀ CH), 124.20 (4 ꢀ CH), 125.68 (2 ꢀ C),
126.92 (2 ꢀ CH), 126.95 (4 ꢀ CH), 127.50 (4 ꢀ CH), 128.04 (4 ꢀ CH),
132.49 (2 ꢀ CH), 134.82 (2 ꢀ CH), 136.55 (2 ꢀ C), 137.02 (2 ꢀ C),
143.59 (2 ꢀ C), 146.87 (2 ꢀ C), 151.77 (2 ꢀ C), 160.82 (2 ꢀ C), 164.13
(2 ꢀ C). IR (ATR)nmax cmꢁ1: 2952, 2918, 2847,1704,1623,1586,1565,
1511, 1342, 1208, 1194, 1108, 1082, 1049, 964, 853, 839, 809, 748,
722, 703, 685. Anal. Calcd. for C60H60N2O10: C, 74.36; H, 6.24; N,
2.89. Found: C, 74.55; H, 6.40; N, 3.04.
2.4.10. (E)-4-(2-(Naphthalen-2-yl)vinyl)benzaldehyde (15)
Prepared from 2-vinylnaphthalene (1.54 g, 10.0 mmol) and
crystallized from toluene, yielding 1.52 g (59%), of a creamy-white
crystalline product, mp ¼ 162e164 ꢂC. 1H NMR (CDCl3, 400 MHz);
d
ppm: 6.68 (d, J ¼ 12.2 Hz, 1H, CH), 6.90 (d, J ¼ 12.2 Hz, 1H, CH),
7.40e7.50 (m, 3H, CHAr, 2 ꢀ CH), 7.64e7.75 (m, 4H, 4 ꢀ CHAr), 7.80e
7.89 (m, 4H, 4 ꢀ CHAr), 9.99 (s, 1H, CHO). 13C NMR (CDCl3, 100 MHz);
d
ppm: 123.36 (CH), 126.43 (CH), 126.57 (CH), 126.93 (2 ꢀ CH),
127.62 (CH), 127.63 (CH), 127.77 (CH), 128.18 (CH), 128.56 (CH),
130.30 (2 ꢀ CH), 132.30 (CH), 133.42 (C), 133.61 (C), 134.04 (C),
135.36 (C), 143.47 (C), 191.62 (CHO). Anal. Calcd. for C19H14O: C,
88.34; H, 5.46. Found: C, 88.50; H, 5.50.
2.5.3. Dioctyl 2,6-bis((E)-4-((E)-4-methylstyryl)styryl)benzo[1,2-
b:4,5-b0]difuran-3,7-dicarboxylate (18)
Prepared from aldehyde 8, 0.63 g (70%) of an orange solid,
mp ¼ 248e250 ꢂC. 1H NMR (CDCl3, 700 MHz),
d ppm: 0.88 (t,
2.5. General procedure for arylevinyl benzodifurans (16e25)
J ¼ 7.0 Hz, 6H, 2 ꢀ CH3), 1.23e1.37 (m, 8H, 4 ꢀ CH2), 1.42e1.49 (m,
4H, 2 ꢀ CH2), 1.52e1.56 (m, 4H, 2 ꢀ CH2), 1.91 (t, J ¼ 7.0 Hz, 4H,
2 ꢀ CH2), 4.44 (t, J ¼ 7.0 Hz, 4H, 2 ꢀ CH2), 7.06 (d, J ¼ 17.5 Hz, 2H,
2 ꢀ CH), 7.14 (d, J ¼ 16.1 Hz, 2H, 2 ꢀ CH), 7.17 (d, J ¼ 7.7 Hz, 4H,
Triphenylphosphonium salt (5) (1.18 g, 1 mmol) and lithium
hydroxide monohydrate (0.11 g, 2.7 mmol) in 2-propanol (4 mL)

M.J. Bosiak et al. / Dyes and Pigments 99 (2013) 803e811
807
2.5.5. Dioctyl 2,6-bis((E)-4-((E)-4-fluorostyryl)styryl)benzo[1,2-
b:4,5-b0]difuran-3,7-dicarboxylate (20)
Prepared from aldehyde 10, 0.58 g (63%) of an orange solid,
mp ¼ 235e237 ꢂC. 1H NMR (CDCl3, 400 MHz),
d ppm: 0.88 (t,
J ¼ 7.2 Hz, 6H, 2 ꢀ CH3), 1.31e1.42 (m, 16H, 8 ꢀ CH2), 1.49e1.60 (m,
4H, 2 ꢀ CH2), 1.85e1.95 (m, 4H, 2 ꢀ CH2), 4.44 (t, J ¼ 7.2 Hz, 4H,
2 ꢀ CH2), 6.98e7.07 (m, 6H, 4 ꢀ CHAr, 2 ꢀ CH), 7.12 (d, J ¼ 16.0 Hz,
2H, 2 ꢀ CH), 7.47e7.53 (m, 8H, 8 ꢀ CHAr), 7.61e7.65 (m, 6H, 4 ꢀ CHAr
,
2 ꢀ CH), 7.94 (d, 2H, J ¼ 16.4 Hz, 2 ꢀ CH), 8.02 (s, 2H, 2 ꢀ CHAr).
Solubility too low for 13C NMR. IR (ATR)nmax cmꢁ1: 2949, 2920,
2845, 1703, 1564, 1549, 1509, 1462, 1454, 1421, 1399, 1355, 1283,
1230, 1207, 1196, 1155,1081,1048, 966, 853, 825, 781, 721, 703. Anal.
Calcd. for C60H60F2O6: C, 78.75; H, 6.61. Found: C, 78.51; H, 6.63.
2.5.6. Dioctyl 2,6-bis((E)-4-((E)-4-chlorostyryl)styryl)benzo[1,2-
b:4,5-b0]difuran-3,7-dicarboxylate (21)
Prepared from aldehyde 11, 0.49 g (52%) of an orange solid,
Fig. 1. Molecular structure of the prepared arylevinyl BDFs.
mp ¼ 248e250 ꢂC. 1H NMR (CDCl3, 700 MHz),
d ppm: 0.88 (t,
J ¼ 7.0 Hz, 6H, 2 ꢀ CH3), 1.23e1.39 (m, 8H, 4 ꢀ CH2), 1.42e1.46 (m,
4H, 2 ꢀ CH2), 1.54e1.58 (m, 4H, 2 ꢀ CH2), 1.91 (t, J ¼ 7.0 Hz, 4H,
2 ꢀ CH2), 4.44 (t, J ¼ 7.0 Hz, 4H, 2 ꢀ CH2), 7.06 (d, J ¼ 16.8 Hz, 2H,
2 ꢀ CH), 7.10 (d, J ¼ 16.8 Hz, 2H, 2 ꢀ CH), 7.51e7.54 (m, 4H,
4 ꢀ CHAr), 7.60e7.66 (m, 6H, 4 ꢀ CHAr, 2 ꢀ CH), 7.93 (d, 2H,
4 ꢀ CHAr), 7.42 (d, J ¼ 7.7 Hz, 4H, 4 ꢀ CHAr), 7.52 (d, J ¼ 7.7 Hz, 4H,
4 ꢀ CHAr), 7.60e7.64 (m, 6H, 4 ꢀ CHAr, 2 ꢀ CH), 7.93 (d, J ¼ 16.8 Hz,
2H, 2 ꢀ CH), 8.03 (s, 2H, 2 ꢀ CHAr). Solubility too low for 13C NMR. IR
(ATR)nmax cmꢁ1: 3021, 2950, 2916, 2849, 1703, 1622, 1590, 1562,
1547,1513,1452,1420,1398,1354,1282,1251,1265,1194, 1150, 1081,
1048, 963, 853, 818, 801, 781, 721, 704. Anal. Calcd. for C62H66O6: C,
82.09; H, 7.33. Found: C, 82.52; H, 7.31.
J ¼ 16.1 Hz, 2 ꢀ CH), 8.02 (s, 2H, 2 ꢀ CHAr). Solubility too low for 13
C
NMR. IR (ATR)nmax cmꢁ1: 2922, 2846, 1703, 1561, 1487, 1354, 1279,
1194, 1150, 1115, 1087, 1055, 1011, 962, 855, 824, 799, 782, 723, 703,
663. Anal. Calcd. for C60H60Cl2O6: C, 76.02; H, 6.38. Found: C, 76.34;
H, 6.33.
2.5.4. Dioctyl 2,6-bis((E)-4-((E)-4-methoxystyryl)styryl)benzo[1,2-
b:4,5-b0]difuran-3,7-dicarboxylate (19)
2.5.7. Dioctyl 2,6-bis((E)-4-((E)-4-(trifluoromethyl)styryl)styryl)
benzo[1,2-b:4,5-b0]difuran-3,7-dicarboxylate (22)
Prepared from aldehyde 9, 0.62 g (66%) of an orange solid,
mp ¼ 218e220 ꢂC. 1H NMR (CDCl3, 700 MHz),
d ppm: 0.88 (t,
Prepared from aldehyde 12, 0.53 g (52%) of an orange solid,
J ¼ 7.0 Hz, 6H, 2 ꢀ CH3), 1.30e1.32 (m, 8H, 4 ꢀ CH2), 1.37 (m, 4H,
2 ꢀ CH2), 1.44 (m, 4H, 2 ꢀ CH2), 1.54e1.58 (m, 4H, 2 ꢀ CH2), 1.91 (m,
4H, 2 ꢀ CH2), 3.82 (s, 6H, 2 ꢀ CH3), 4.44 (t, J ¼ 7.0 Hz, 4H, 2 ꢀ CH2),
6.89 (d, J ¼ 9.1 Hz, 4H, 4 ꢀ CHAr), 6.96 (d, J ¼ 16.1 Hz, 2H, 2 ꢀ CH),
7.11 (d, J ¼ 16.1 Hz, 2H, 2 ꢀ CH), 7.59e7.62 (m, 6H, 4 ꢀ CHAr, 2 ꢀ CH),
7.90 (d, J ¼ 16.1 Hz, 2H, 2 ꢀ CH), 8.01 (s, 2H, 2 ꢀ CHAr). Solubility too
low for 13C NMR. IR (ATR)nmax cmꢁ1: 2926, 2916, 2848, 1703, 1603,
1590, 1563, 1511, 1354, 1302, 1251, 1206, 1194, 1172, 1150, 1079, 1051,
1032, 967, 855, 826, 803, 782. Anal. Calcd. for C62H66O8: C, 79.29; H,
7.08. Found: C, 78.82; H, 7.03.
mp ¼ 242e244 ꢂC. 1H NMR (CDCl3, 700 MHz),
d ppm: 0.88 (t,
J ¼ 7.0 Hz, 6H, 2 ꢀ CH3), 1.30e1.34 (m, 8H, 4 ꢀ CH2), 1.36e1.41 (m,
4H, 2 ꢀ CH2), 1.44 (m, 4H, 2 ꢀ CH2), 1.55e1.58 (m, 4H, 2 ꢀ CH2), 1.91
(m, 4H, 2 ꢀ CH2), 4.45 (t, J ¼ 7.0 Hz, 4H, 2 ꢀ CH2), 7.15 (d, J ¼ 16.1 Hz,
2H, 2 ꢀ CH), 7.18 (d, J ¼ 16.1 Hz, 2H, 2 ꢀ CH), 7.54 (d, J ¼ 7.7 Hz, 4H,
4 ꢀ CH), 7.60e7.63 (m, 14H, 14 ꢀ CHAr), 7.93 (d, 4H, J ¼ 16.1 Hz,
2 ꢀ CH), 8.02 (s, 2H, 2 ꢀ CHAr). Solubility too low for 13C NMR. IR
(ATR)nmax cmꢁ1: 2952, 2921, 2849, 1704, 1611, 1420, 1328, 1284,
1264, 1187, 1157, 1108, 1066, 1056, 1015, 1015, 961, 853, 830, 802,
Scheme 1. Synthesis of extended arylevinyl BDFs.

808
M.J. Bosiak et al. / Dyes and Pigments 99 (2013) 803e811
Table 1
Solubility of 2,6-dimethylbenzofuro[5,6-b]furan-3,7-dicarboxylate esters in common solvents.
R3
Reaction Solubility at 20ꢂC/at bp [
yield [%]
mmol/mL]
H2O
Et2O
MeOH
EtOH
Acetone
Ethyl acetate THF
CH2Cl2
CHCl3
Toluene
PE
C2H5
C5H11
C8H17
e
<0.1/1.0
<0.1/1.8
24/140 <0.1/31
28/500 <0.1/20
<0.1/5.1
0.15/27
5.4/33
16/650
9.0/>1000
0.7/190
<0.1/<0.1
N
11/160
25/>1000
27/>1000
2.2/>1000
<0.1/64
N
38/270
145/317
260/>1000 23/>1000 <0.1/1.5
60
78
61
76
5
<0.1/<0.1
<0.1/<0.1
<0.1/<0.1
0.12/>1000
0.1/>1000
<0.1/630
217/>1000 620/>1000 >1000/>1000 120/>1000
270/>1000 680/>1000 >1000/>1000 158/>1000
70/>1000 170/>1000
<0.1/450
N
1.0/13
3.2/210
1.1/41
C
C
10H21
18H37
7.2/54
<0.1/1.8
255/>1000 125/>1000
6/384
<0.1/<0.1 <0.1/<0.1 <0.1/<0.1 <0.1/<0.1
N
0.5/23
N
0.5/>1000 <0.1/<0.1
N <0.1/<0.1
mPEG 500
N
N
N
N
Table 2
8H, 4 ꢀ CH2), 1.91 (t, J ¼ 7.0 Hz, 4H, 2 ꢀ CH2), 2.50 (s, 6H, 2 ꢀ CH3),
4.44 (t, J ¼ 7.0 Hz, 4H, 2 ꢀ CH2), 7.05 (d, J ¼ 16.1 Hz, 2H, 2 ꢀ CH), 7.10
(d, J ¼ 15.4 Hz, 2H, 2 ꢀ CH), 7.22e7.24 (m, 2H, 2 ꢀ CHAr), 7.43 (d,
J ¼ 8.4 Hz, 4H, 4 ꢀ CHAr), 7.50 (d, J ¼ 8.4 Hz, 6H, 6 ꢀ CHAr), 7.59e7.61
(m, 6H, 4 ꢀ CHAr, 2 ꢀ CH), 7.91 (d, J ¼ 16.1 Hz, 2H, 2 ꢀ CH), 8.01 (s,
Synthesis of stilbene aldehydes using montmorillonite-supported palladium cata-
lyst (12% wt.).
2H, 2 ꢀ CHAr). Solubility too low for 13C NMR. IR (ATR)nmax cmꢁ1
:
2951, 2918, 2850, 1701, 1420, 1354, 1206, 1192, 1085, 1051, 961, 856,
819, 798, 782, 702. Anal. Calcd. for C62H66O6S2: C, 76.67; H, 6.85.
Found: C, 76.88; H, 6.89.
2.5.9. Dioctyl 2,6-bis((E)-4-((E)-3,4,5-trimethoxystyryl)styryl)
benzo[1,2-b:4,5-b0]difuran-3,7-dicarboxylate (24)
Ar
Product
Yield, %
C6H5
6
7
8
96
99
90
47
41
99
39
48
46
59
Prepared from aldehyde 14, 0.61 g (58%) of an orange solid,
mp ¼ 182e184 ꢂC. 1H NMR (CDCl3, 700 MHz),
d ppm: 0.88 (t,
4-NO2-C6H4
4-CH3-C6H4
4-OCH3-C6H4
4-F-C6H4
J ¼ 7.0 Hz, 6H, 2 ꢀ CH3), 1.29e1.32 (m, 8H, 4 ꢀ CH2), 1.36e1.39 (m,
4H, 2 ꢀ CH2), 1.41e1.46 (m, 4H, 2 ꢀ CH2), 1.91 (m, 4H, 2 ꢀ CH2),
3.87 (s, 6H, 2 ꢀ CH3), 3.92 (s, 12H, 4 ꢀ CH3), 4.44 (t, J ¼ 7.0 Hz, 4H,
2 ꢀ CH2), 6.75 (s, 4H, 4 ꢀ CHAr), 7.01 (d, J ¼ 16.1 Hz, 2H, 2 ꢀ CH),
7.09 (d, J ¼ 16.1 Hz, 2H, 2 ꢀ CH), 7.52e7.54 (m, 4H, 2 ꢀ CH), 7.62e
7.64 (m, 6H, 4 ꢀ CHAr, 2 ꢀ CH), 7.94 (d, J ¼ 16.1 Hz, 2H, 2 ꢀ CH),
9
10
11
12
13
14
15
4-Cl-C6H4
4-CF3-C6H4
4-SMe-C6H4
3,4,5-OCH3-C6H2
2-Naphthyl
8.04 (s, 2H, 2 ꢀ CHAr). 13C NMR (CDCl3, 100 MHz);
d ppm: 15.03
(2 ꢀ CH3), 23.64 (2 ꢀ CH2), 27.31 (2 ꢀ CH2), 29.93 (2 ꢀ CH2), 30.23
(2 ꢀ CH2), 30.33 (2 ꢀ CH2), 32.82 (2 ꢀ CH2), 57.22 (4 ꢀ CH3), 61.92
(2 ꢀ CH3), 65.83 (2 ꢀ CH2), 104.12 (2 ꢀ CH), 105.09 (4 ꢀ CH),
110.29 (2 ꢀ C), 116.36 (2 ꢀ CH), 126.66 (2 ꢀ C), 127.86 (4 ꢀ CH),
128.50 (2 ꢀ CH), 128.95 (4 ꢀ CH), 130.53 (2 ꢀ CH), 133.86 (2 ꢀ C),
136.16 (2 ꢀ CH), 136.42 (2 ꢀ C), 139.27 (2 ꢀ C), 139.56 (2 ꢀ C),
152.76 (2 ꢀ C), 154.52 (4 ꢀ C), 161.89 (2 ꢀ C), 165.11 (2 ꢀ C). IR
(ATR)nmax cmꢁ1: 2926, 2853, 1697, 1580, 1564, 1508, 1463, 1455,
1420, 1397, 1377, 1347, 1321, 1282, 1246, 1219, 1189, 1135, 1047, 999,
783, 703. Anal. Calcd. for C62H60F6O6: C, 73.36; H, 5.96. Found: C,
73.55; H, 5.99.
2.5.8. Dioctyl 2,6-bis((E)-4-((E)-4-(methylthio)styryl)styryl)benzo
[1,2-b:4,5-b0]difuran-3,7-dicarboxylate (23)
Prepared from aldehyde 13, 0.47 g (48%) of an orange solid,
mp ¼ 210e212 ꢂC. 1H NMR (CDCl3, 700 MHz),
d ppm: 0.90 (t,
J ¼ 7.0 Hz, 6H, 2 ꢀ CH3), 1.23e1.37 (m, 8H, 4 ꢀ CH2), 1.44e1.56 (m,
Table 3
The Wittig reaction of BDF salt 5 with stilbene aldehydes.
Stilbene aldehyde
Ar
Product
Yield, %
6
7
8
9
10
11
12
13
14
15
C6H5
16
17
18
19
20
21
22
23
24
25
86
92
70
66
63
52
52
48
58
73
4-NO2-C6H4
4-CH3-C6H4
4-OCH3-C6H4
4-F-C6H4
4-Cl-C6H4
4-CF3-C6H4
4-SMe-C6H4
3,4,5-OCH3-C6H2
2-Naphthyl

M.J. Bosiak et al. / Dyes and Pigments 99 (2013) 803e811
809
Table 4
Physical properties of BDFs 16e25.
Compound
Dichloromethane solution
Solid state
HOMOc (eV)
LUMOc (eV)
Eg (eV)
lem(nm)
a
b
labs (nm)
ε
lem (nm)
qF
sF (ns)
Mꢁ1 cmꢁ1
16
17
18
19
20
21
22
23
445
455
447
450
445
446
446
452
119,600
123,200
110,000
113,200
101,200
94,400
495
495
498
503
494
495
494
504
0.62
<0.01
0.61
0.58
0.64
0.66
0.69
0.61
1.40
0.64
1.10
1.15
1.23
1.30
1.31
1.12
ꢁ4.986
ꢁ5.347
ꢁ4.929
ꢁ4.836
ꢁ5.024
ꢁ5.094
ꢁ5.184
ꢁ4.895
ꢁ2.345
ꢁ2.880
ꢁ2.299
ꢁ2.236
ꢁ2.386
ꢁ2.464
ꢁ2.559
ꢁ2.312
2.641
2.468
2.630
2.600
2.638
2.630
2.625
2.583
560
589
570
570
560
570
560
570
599
570
570
566
118,800
106,400
24
25
1
451
452
432
98,800
128,000
37,100
500
501
478
0.61
0.61
1.00
1.17
1.17
1.4
ꢁ4.920
ꢁ4.966
ꢁ5.584
ꢁ2.309
ꢁ2.358
ꢁ2.603
2.611
2.607
2.981
a
Quantum yield measured with a JASCO FP-8500 spectrometer against fluorescein in 0.1 M NaOH as reference at lex ¼ 460 nm. A reference value of 0.9 for the fluorescein
quantum yield was used for the calculation of qF. Absorbance of the dye solution between 0.041 and 0.099 at labs ¼ 460 nm.
b
Fluorescence lifetime determined by time-correlated single-photon counting (TCSPC) with a PicoQuant (Germany) pulsed LED at lex ¼ 376 nm as light source. The same
solution as that described above was used.
c
Calculated using the B3LYP/6-31G(d,p).
969, 952, 848, 820, 797, 620. Anal. Calcd. for C66H74O12: C, 74.83;
H, 7.04. Found: C, 75.10; H, 7.16.
The transesterification with alcohols proceeded in good yields
whereas the mPEG 5000 ester could not been obtained using this
procedure, and the mPEG 500 ester was obtained only in 5% yield.
The best transesterification yield and good product solubility were
achieved with 1-octanol and this derivative has been chosen for
further transformations. Bromination of dioctyl 2,6-dimethylbenzo
[1,2-b:4,5-b0]difuran-3,7-dicarboxylate (3) with NBS (2.4 equiv.) in
the presence of catalytic amounts of AIBN, gave the 2,6-dibromo
derivative (4) in 58% yield. The reaction of 4 with triphenylphos-
phine in boiling toluene produced the corresponding salt 5 in
quantitative yield (Scheme 1).
2.5.10. Dioctyl 2,6-bis((E)-4-((E)-2-(naphthalen-2-yl)vinyl)styryl)
benzo[1,2-b:4,5-b0]difuran-3,7-dicarboxylate (25)
Prepared from aldehyde 15, 0.71 g (73%) of an orange solid,
mp ¼ 234e236 ꢂC. 1H NMR (CDCl3, 400 MHz),
d ppm: 0.81e0.89
(m, 6H, 2 ꢀ CH3), 1.20e1.26 (m, 8H, 4 ꢀ CH2), 1.32e1.58 (m, 8H,
4 ꢀ CH2), 1.73e1.90 (m, 8H, 4 ꢀ CH2), 4.33e4.44 (m, 4H, 2 ꢀ CH2),
7.29e7.68 (m, 32H, 24 ꢀ CHAr, 8 ꢀ CH). Solubility too low for 13C
NMR. IR (ATR)nmax cmꢁ1: 3053, 3024, 2951, 2926, 2915, 2864,
2856, 1704, 1623, 1565, 1548, 1500, 1453, 1417, 1399, 1356, 1287,
1249, 1208, 1197, 1152, 1059, 961, 854, 818, 782, 746, 722, 703.
Anal. Calcd. for C68H66O6: C, 83.40; H, 6.79. Found: C, 83.85; H,
6.83.
Stilbene aldehydes 6e15 for the Wittig reaction were obtained
from 4-bromobenzaldehyde and appropriate styrenes via the Heck
coupling reaction. Commercially unavailable or expensive styrenes
(4-nitrostyrene,
4-trifluoromethylstyrene,
1-(methylthio)-4-
vinylbenzene, 3,4,5-trimethoxystyrene, and 2-vinylnaphthalene)
were obtained via the Wittig reaction of an appropriate aldehyde
and methyltriphenylphosphonium iodide.
3. Results and discussion
The Heck coupling reaction of 4-bromobenzaldehyde and sty-
rene, catalyzed by palladium acetate according to the Yao [44]
method, gave in our hands the desired product only in 65% yield.
The aim of this work was the development and fluorescence
characterization of new conjugated BDF arylevinyl systems
containing four double bonds and at least four phenyl rings 16e
25, and their comparison with previously obtained arylevinyl
BDFs, containing only two double bonds and two phenyl rings 1
(Fig. 1).
It was obvious that the emission wavelength of such extended
systems would be shifted toward higher values in comparison to 1,
and it was interesting to know how the elongation of the conju-
gated system affects the fluorescence intensity. Separation of the
substituted phenyl ring and BDF core with 1,4-divinylphenylene
moiety would show more clearly the influence of arylevinyl sub-
stituents on the fluorescence of compounds represented by general
formula, Fig. 1.
Their synthesis started from diethyl 2,6-dimethylbenzofuro[5,6-
b]furan-3,7-dicarboxylate (2), Scheme 1, which was prepared in
21% yield from easily available p-benzoquinone and ethyl acetoa-
cetate using earlier described method [42]. Ethyl groups of 2 were
replaced by alkyl or methoxypoly(ethylene glycol) groups via the
transesterification reaction to improve the desired conjugated
system solubility in common organic solvents. The process was
carried out according to the Cepanec [43] method, using anhydrous
potassium phosphate and tert-butylammonium bromide, as a
phase transfer catalyst, in alcohol or toluene (Table 1).
Fig. 2. Emission spectra of 16e25 in dichloromethane. Excitation wavelength
lex ¼ 460 nm. Concentration set to an absorbance value between 0.04 and 0.10 to avoid
the inner filter effect. The spectra are normalized to the maximal intensity. For com-
parison, the spectrum of 1 is also depicted (lex ¼ 366 nm).

810
M.J. Bosiak et al. / Dyes and Pigments 99 (2013) 803e811
Fig. 3. HOMO and LUMO orbitals of 16 calculated within the B3LYP/6-31G(d,p) approach.
Better yields (96%), were obtained using the montmorillonite-
supported palladium catalyst [45], and this catalytic system has
been used for further research. The desired stilbene aldehydes were
obtained in moderate to excellent yields (Table 2).
The Wittig reaction of stilbene aldehydes with BDF salt 5, using
lithium hydroxide monohydrate in isopropanol [45], monitored by
TLC, was continued until the starting aldehyde faded (2e5 h). The
products are shown in Table 3.
The products 16e25 were mixtures of E/Z isomers. The E/Z
ratio assignment is based on the 1H NMR coupling constants
between hydrogen atoms at the double bonds. Pure E isomers
were obtained by heating the mixture with a small amount of
iodine in p-xylene for 2 h. The products were obtained in mod-
erate to good yields, as amorphous orange to red solids. Unfor-
tunately in some cases solubility was too low for recording 13C
NMR spectra.
Among the products 16e25, the compound 25, containing the 2-
naphthyl group, exhibited the highest fluorescence intensity in
dichloromethane solution, taken as a combination of the molar
extinction coefficient and fluorescence quantum yield (Table 4). The
fluorescence of other compounds is similar except 4-nitrophenyl
derivative which exhibits no fluorescence. The nitroaromatics are
effective fluorescence quenchers of most fluorophores [46]. This
phenomenon is attributed to the photo-induced electron transfer
(PET) process.
This may suggest that the further separation of the substituted aryl
end group from the benzodifuran core, the smaller is its impact on
the wavelength of light emitted by the system. This leads to the
conclusion that modification of the fluorophore structure should be
made close to the benzodifuran core to affect the color of the
emitted light.
An insight into the electronic structure of the investigated
molecules was gained by the QM calculations within the B3LYP/6-
31G(d,p). The calculations were performed with Gaussian 09 pro-
gram package [47].
Fig. 3 presents the HOMO and LUMO orbitals of 16 which is
representative of the 2,6-substituted benzodifurans. Visualization
of the HOMO and LUMO molecular orbitals does not suggest any
significant charge transfer during an electron excitation. The non-
planar structure of desired compounds can effectively hinder
intermolecular aggregation preventing strict packing of molecules
and improving luminescence.
4. Conclusion
In summary, ten new arylevinyl BDFs containing four double
bonds and at least four aromatic rings were obtained by a four step
synthesis, involving the Heck and the Wittig reactions, with good
overall yields. All of the new BDFs, except 4-nitrophenyl derivative,
exhibit high fluorescence and quantum yields. Their comparison
with previously obtained arylevinyl BDFs, containing only two
double bonds and two phenyl rings, revealed similar fluorescence
intensity despite a slightly lower quantum yields, due to higher
molar extinction coefficient. The emission spectra of the new BDFs
exhibit almost identical profiles and emission maxima, which are
shifted to longer wavelengths in comparison to less conjugated
arylevinyl BDFs.
In the solid state, compound 20 (4-fluorophenyl), was the
most fluorescent. The fluorescence of compounds 22 (4-
trifluoromethylphenyl), 25 (2-naphthyl), 18 (4-methylphenyl), 16
(phenyl), was lower. Weaker fluorescence was observed for
compounds 19 (4-methoxyphenyl), 21 (4-chlorophenyl), 23 (4-
methylthiophenyl), and 24 (3,4,5-trimethoxyphenyl), whereas
compound 17 (4-nitrophenyl) revealed no fluorescence. The
emission spectra of 16e25 are shown in Fig. 2.
The results were compared to the previously obtained diethyl
2,6-di((E)-styryl)benzo[1,2-b:4,5-b0]difuran-3,7-dicarboxylate (1).
It was found that elongation of the arylevinyl substituents of
benzodifuran has no appreciable effect on the fluorescence in-
tensity. Although the fluorescence quantum yield decreased in
comparison to the mono arylevinyl system, the molar absorptivity
increased significantly and resulted in equalization of the fluores-
cence intensity. The emission profiles and fluorescence maxima for
all new arylevinyl benzodifuran derivatives are almost identical.
Acknowledgments
Financial support from the Nicolaus Copernicus University,
ꢀ
Torun, Wydzia1 Chemii, Grant Dziekana 1094-Ch, is acknowledged.
The authors gratefully acknowledge Wroclaw Networking and
Supercomputing Center (WCSS) and Academic Computer Center
Cyfronet AGH for a generous allotment of computer time. Mariusz
Bosiak gratefully acknowledge Prof. Marek Zaidlewicz and
Dr. Marzanna Kurzawa for help.

M.J. Bosiak et al. / Dyes and Pigments 99 (2013) 803e811
811
[26] Tsuji H, Mitsui C, Ilies L, Sato Y, Nakamura E. Synthesis and properties of
2,3,6,7-tetraarylbenzo[1,2-b:4,5-b0]difurans as hole-transporting material.
J Am Chem Soc 2007;129:11902e3.
[27] Hayashi N, Saito Y, Higuchi H, Suzuki K. Comparative studies on electronic
spectra and redox behaviors of isomeric benzo[1,2-b:4,5-b0]difurans and
benzo[1,2-b:5,4-b0]difurans. J Phys Chem A 2009;113:5342e7.
References
[1] Hilsum C. Flat-panel electronic displays: a triumph of physics, chemistry and
engineering. Philos Transact A Math Phys Eng Sci 2010;368:1027e82.
[2] Park JW, Shin DC, Park SH. Large-area OLED lightings and their applications.
Semicond Sci Technol 2011;26. 034002 [9 pp].
[3] Szyszka B, Dewald W, Gurram SK, Pflug A, Schulz C, Siemers M, et al.
Recent developments in the field of transparent conductive oxide films for
spectral selective coatings, electronics and photovoltaics. Curr Appl Phys
2012;12:S2e11.
[28] Moussallem C, Gohier F, Mallet C, Allain M, Frère P. Extended benzodifurane
furan derivatives as example of
p-conjugated materials obtained from sus-
tainable approach. Tetrahedron 2012;68:8617e21.
[29] Ch Yi, Blum C, Lehmann M, Keller S, Liu S, Frei G, et al. Versatile strategy to
access fully functionalized benzodifurans: redox-active chromophores for the
construction of extended p-conjugated materials. J Org Chem 2010;75:3350e7.
[30] Caruso U, Panunzi B, Roviello GN, Roviello G, Tingoli M, Tuzi A. Synthesis,
[4] Park JS, Maeng WJ, Kim HS, Park JS. Review of recent developments in
amorphous oxide semiconductor thin-film transistor devices. Thin Solid Films
2012;520:1679e93.
structure and reactivity of amino-benzodifurane derivatives.
C R Chim
[5] So F, Kido J, Burrows P. MRS Bull 2008;33:663e9.
2009;12:622e34.
[6] Lafont U, Zeijl H, Zwaag S. Increasing the reliability of solid state lighting
systems via self-healing approaches: a review. Microelectron Reliab 2012;52:
71e89.
[7] Kalyania TN, Dhoble SJ. Organic light emitting diodes: energy saving lighting
technology e a review. Renev Sust Energ Rev 2012;6:2696e723.
[8] Duagal AR, Heller CM, Shiang JJ, Liu J, Lewis LN. Solution-processed organic
light-emitting diodes for lighting. J Display Technol 2007;3:184e92.
[9] Hosokawa C, Higashi H, Nakamura H, Kusumoto T. Highly efficient blue
electroluminescence from a distyrylarylene emitting layer with a new dopant.
Appl Phys Lett 1995;67:3853e5.
[10] Strukeji M, Jordan RH, Dodabalapur A. Organic multilayer white light emitting
diodes. J Am Chem Soc 1996;118:1213e4.
[11] Gao ZQ, Lee CS, Bello I, Lee ST. Bright-blue electroluminescence from a silyl-
substituted ter-(phenyleneevinylene) derivative. Appl Phys Lett 1999;74:
865e7.
[12] Hosokawa C, Tokailin H, Higashi H, Kusumoto T. Efficient electroluminescence
of distyrylarylene with hole transporting ability. J Appl Phys 1995;78:5831e3.
[13] Tao XT, Suzuk H, Wada T, Sasabe H, Miyata S. Lithium tetra-(8-hydroxy-qui-
nolinato) boron for blue electroluminescent applications. Appl Phys Lett
1999;75:1655e8.
[14] Mi BX, Gao ZQ, Lee CS, Lee ST. Reduction of molecular aggregation and its
application to the high-performance blue perylene-doped organic electrolu-
minescent device. Appl Phys Lett 1999;75:4055e7.
[15] Yu WL, Cao Y, Pei J, Huang W, Heeger AJ. Blue polymer light-emitting diodes
from poly(9,9-dihexylfluorene-alt-co-2,5-didecyloxy-para-phenylene). Appl
Phys Lett 1999;75:3270e2.
[16] Jiang XZ, Liu S, Ma H. High-performance blue light-emitting diode based on a
binaphthyl-containing polyfluorene. Appl Phys Lett 2000;76:1813e5.
[17] Lee CW, Rhee HW, Kim C, Gong MS. Chemiluminescent properties of fluorene-
and carbazole-containing polymeric fluorophores. Bull Korean Chem Soc
2000;21:701e4.
[18] Seong NC, Jeon YM, Lim TH, Kim JW, Lee CW, Lee EJ, et al. Organic light-
emitting device using new distyrylarylene host materials. Synth Met
2007;157:421e6.
[19] Mullen K, Wegner G. Electronic materials: the oligomer approach. Weinheim,
Germany: Wiley-VCH; 1998.
[20] Mullen K, Scherf U. Organic-light emitting devices: synthesis, properties and
applications. Weinheim, Germany: Wiley-VCH; 2006.
[21] Li Z, Meng H. Organic light-emitting materials and devices. Boca Raton, Lon-
don, New York: Taylor & Francis; 2007.
[22] Guerlin A, Dumur F, Dumas E, Miomandre F, Wantz G, Mayer CR. Tunable
optical properties of chromophores derived from oligo(p-phenylene vinyl-
ene). Org Lett 2010;12:2382e5.
[23] Babu SS, Praveen VK, Prasanthkumar S, Ajayaghoshi A. Self-assembly of
oligo(para-phenylenevinylene)s through arenedperfluoroarene interactions:
[31] Shukla R, Wadumethrige SH, Lindeman SV, Rathore R. Synthesis, electronic
properties, and X-ray structural characterization of tetraarylbenzo[1,2-b: 4,5-
b0]difuran cation radicals. Org Lett 2008;10:3587e90.
[32] Santos-Pérez J, Crespo-Hernández CE, Reichardt C, Cabrera CR, Feliciano-
Ramos I, Arroyo-Ramírez L, et al. Synthesis, optical characterization, and
electrochemical properties of isomeric tetraphenylbenzodifurans containing
electron acceptor groups. J Phys Chem A 2011;115:4157e68.
[33] Liu H, Jiang P, Yi C, Liu SX, Tan S, Zhao B, et al. Benzodifuran-based
p-con-
jugated copolymers for bulk heterojunction solar cells. Macromolecules
2010;43:8058e62.
[34] Yi C, Blum C, Lehmann M, Keller S, Liu SX, Frei G, et al. Versatile strategy to access
fully functionalized benzodifurans: redox-active chromophores for the con-
struction of extended pi-conjugated materials. J Org Chem 2010;75:3350e7.
ꢀ
[35] Bosiak MJ, Jakubowska JA, Aleksandrzak KB, Kaminski S, Kaczmarek-
Ke˛dziera A, Ziegler-Borowska M, et al. Synthesis of a new class of highly
fluorescent aryl-vinyl benzo[1,2-b:4,5-b0]difuran derivatives. Tetrahedron Lett
2012;53:3923e6.
[36] Kadac K, Bosiak MJ, Nowaczyk J. Synthesis and AC impedance studies of 2,6-
distyrylbenzofuro[5,6-b]furan based new organic semiconductor. Synth Met
2012;162:1981e6.
[37] Ottanà R, Maccari R, Giglio M, Del Corso A, Cappiello M, Mura U, et al. Iden-
tification of 5-arylidene-4-thiazolidinone derivatives endowed with dual ac-
tivity as aldose reductase inhibitors and antioxidant agents for the treatment
of diabetic complications. Eur J Med Chem 2011;46:2797e806.
[38] Kim BR, Lee HG, Kim EJ, Lee SG, Yoon YJ. Conversion of oximes to carbonyl
compounds with 2-Nitro-4,5-dichloropyridazin-3(2H)-one.
J Org Chem
2010;75:484e6.
[39] Schiemenz GP, Thobe J. Aromatische Phosphine mit Substituenten zweiter
Ordnung, III. Eine neue Variante der Wittig-Reaktion. Chem Ber 1966;99:
2663e8.
[40] Xu HJ, Zhao YQ, Zhou XF. Palladium-catalyzed Heck reaction of aryl chlorides
under mild conditions promoted by organic ionic bases. J Org Chem 2011;76:
8036e41.
[41] Manecke G, Luettke S. Über Synthesen einiger oligomerer substituierter
Arylenvinylene. Chem Ber 1970;103:700e7.
[42] Wu X, Davis AP, Fry AJ. Electrocatalytic oxidative cleavage of electron-
deficient substituted stilbenes in acetonitrile-water employing a new high
oxidation potential electrocatalyst. An electrochemical equivalent of ozonol-
ysis. Org Lett 2007;9:5633e6.
ꢁ
ꢀ
ꢁ ꢀ
ꢁ
ꢀ
ꢁ
[43] Cepanec I, Zivkovic A, Bartolincic A, Mikuldas H, Litvic M, Merkas S. Potassium
phosphate/benzyltriethylammonium chloride as efficient catalytic system for
transesterification. Croat Chem Acta 2008;81:519e23.
[44] Yao Q, Kinney EP, Yang Z. Ligand-free Heck reaction: Pd(OAc)2 as an active
catalyst revisited. J Org Chem 2003;68:7528e31.
[45] Antonioletti R, Bonadies F, Ciammaichella A, Viglianti A. Lithium hydroxide as
base in the Wittig reaction. A simple method for olefin synthesis. Tetrahedron
2008;64:4644e8.
[46] Glazier S, Barron JA, Morales N, Ruschak AM, Houston PL, Abrun HD.
Quenching dynamics of the photoluminescence of [Ru(bpy)3]2þ-pendant
PAMAM dendrimers by nitro aromatics and other materials. Macromole-
cules 2003;36:1272e8.
[47] Frisch MJ, Trucks GW, Schlegel HB, Scuseria GE, Robb MA, Cheeseman JR, et al.
Gaussian 09, revision A.02. Wallingford CT: Gaussian, Inc.; 2009.
p
gels with longitudinally controlled fiber growth and supramolecular
exciplex-mediated enhanced emission. Chem Eur J 2008;14:9577e84.
[24] Chaieb A, Vignau L, Brown R, Wantz G, Huby N, Francois J, et al. PL and EL
properties of oligo(p-phenylene vinylene) (OPPV) derivatives and their
applications in organic light-emitting diodes (OLED). Opt Mater 2008;31:
68e74.
[25] Tsuji H, Mitsui C, Sato Y, Nakamura E. Bis(carbazolyl)benzodifuran: a high-
mobility ambipolar material for homojunction organic light-emitting diode
devices. Adv Mater 2009;21:3776e9.