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J. Motoyoshiya et al. / Spectrochimica Acta Part A 69 (2008) 167–173
(2.00 g, 3.15 mmol) in DMF (20 mL) and stirred for 30 min at
room temperature. To the slurry was added dropwise a solution
of 4-N-dimethylaminobenzaldehyde (0.78 g, 5.23 mmol) in
DMF (10 mL). After being stirred for 8 h at room temperature,
the solvent was removed by distillation under a reduced
pressure and then a saturated ammonium chloride solution was
added to the residue. The product was extracted with ether and
the organic phase was dried over anhydrous Na2SO4. After
removal of the solvent, the product was purified by column
chromatography on silica gel with benzene as an eluant to give
1 (0.62 g, 38%) as an oil. 1H NMR (400 MHz, CDCl3) δ 0.90t,
6H, J = 7.2 Hz, 0.99 (t, 6H, J = 7.2 Hz), 1.34–1.60 (m, 16H),
1.75–1.83 (m, 2H), 2.98 (s, 12H), 3.93 (d, 4H, J = 5.2 Hz),
6.72 (d, 4H, J = 8.4 Hz), 7.05 (d, 2H, J = 16 Hz), 7.09 (s, 4H),
7.29 (d, 2H, J = 16 Hz), 7.41 (d, 2H, J = 8.40 Hz). 13C NMR
(100 MHz, CDCl3) δ 11.82, 14.60, 23.43, 24.15, 30.33, 30.75,
38.05, 43.62, 77.12, 112.45, 113.08, 120.43, 124.42, 124.83,
126.21, 127.12, 143.76, 148.07.
Fig. 1. Structures of distyrylbenzene 1 and 2.
substances such as chloro, nitro and boronic compounds. Since
the azacrown moiety is known to act as a recognition site for a
suitable metal cation [26–28], the interaction of the distyrylben-
zenes with the azacrown moieties will form a chemosensor for a
suitable metal cation. We show that these types of distyrylben-
zenes have the possible potential of being used as chemosensors
for suitable substances.
2.3. Synthesis of (E,E)-2,5-bis(2ꢀ-ethylhexyloxy)-1,4-
bis[4ꢀꢀ-(N-monoaza-15-crown-5)-styryl]benzene (2)
This compound was prepared similarly to the procedure
described above using tert-BuOK (0.71 g, 6.33 mmol), 2,5-bis
(2ꢀ-ethylhexyloxy)-1,4-bis(diethylphosphonomethyl)benzene
(1.00 g, 1.57 mmol) and 4-(N-monoaza-15-crown-5)benzal-
2. Experimental
1
2.1. Reagents and apparatus
dehyde (0.75 g, 2.32 mmol) in 45% (0.51 g) yield. H NMR
(400 MHz, CDCl3) δ 0.88t, 6H, J = 7.3 Hz), 0.94 (t, 6H,
J = 7.3 Hz), 1.34–1.38 (m, 16H), 1.75–1.83 (m, 2H), 3.62–3.69
(m, 32H), 3.78 (t, 8H, J = 6.0 Hz), 3.93 (d, 4H, J = 5.2 Hz),
6.45 (d, 4H, J = 9.2 Hz), 7.02 (d, 2H, J = 16 Hz), 7.26 (s,
4H), 7.27 (d, 2H, J = 16 Hz), 7.38 (d, 2H, J = 8.40 Hz). 13C
NMR (100 MHz, CDCl3) δ 11.75, 14.54, 23.52, 24.66, 29.69,
31.33, 40.25, 52.98, 69.02, 70.59, 70.61, 71.73, 72.17, 110.24,
112.07, 119.51, 126.64, 127.17, 128.07, 128.53, 147.42,
151.29.
Solvents were purified and dried by the standard method. Two
distyrylbenzenes were synthesized as described bellow. Phenyl-
boronic acid was prepared according to the known method
[29]. Other chemicals were used as purchased. 1H and 13C
NMR spectra were recorded on a Bruker AVANCE-400 at
400 MHz and 100 MHz, respectively. The chemical shifts (δ)
are reported in ppm downfield from TMS as internal standard
or from the residual solvent peak. Coupling constants (J) are
reported in Hz. Analytical TLC was carried out on precoated
silica gel 60F-254 plates (E. Merck). Column chromatogra-
phy was performed on silica gel (E. Merck). Absorption and
fluorescence spectra were recorded on a U-3310 spectrom-
eter (Hitachi) and on a RF-5000 spectrometer (Shimadzu),
respectively. Fluorescence quantum yields were estimated using
9,10-diphenylanthracene (ΦF = 0.91 in benzene) as a standard.
Cyclic voltammetry was performed at room temperature with
a three-compartment cell in dry acetonitrile solution contain-
ing the substrate (ca. 10−4 M) and a supporting electrolyte
(0.1 M tetrabutylammonium perchlorate). Pt disk, Pt wire, and
saturated calomel electrode (SCE) were used as the working,
counter, andreferenceelectrodes, respectively. Thescanratewas
3. Result and discussion
3.1. Synthesis and spectra of distyrylbenzenes 1 and 2
The distyrylbenzenes 1 and 2 were prepared by a modi-
fication of the Wittig olefination reaction using a 1,4-
bis(diethylphosophonomethyl)benzene and the corresponding
aromatic aldehydes in the presence of tert-BuOK. Their geo-
metric structures were identified as all E-forms, and as shown
in Fig. 2a, they exhibit absorptions at 418 and 422 nm with
the large molecular extinction coefficients as log ε: 4.56 and
4.63 and intense fluorescence with the maximum emission
wavelengths located at 482 and 485 nm with the fluorescence
quantum yields of 0.48 and 0.51 for 1 and 2 in THF, respectively.
When comparing their spectra of the parent 4,4ꢀ-distyrylbenzene
without any substituent that has an absorption at 357 nm and
fluorescence at 414 nm (in dioxane) [30], those of 1 and 2
significantly shift to the long wavelength regions, which is
attributed to the presence of the terminal amino groups because
4,4ꢀ-bis(4ꢀꢀ-dimethylaminostyryl)benzene, lacking two alkoxy
100 mV s−1
.
2.2. Synthesis of (E,E)-2,5-bis(2ꢀ-ethylhexyloxy)-1,4-
bis(4ꢀꢀ-N-dimethylstyryl)benzene (1)
To a suspension of tert-BuOK (1.41 g, 12.60 mmol) in
DMF (10 mL) was added a solution (20 mL) of 2,5-bis
(2ꢀ-ethylhexyloxy)-1,4-bis(diethylphosphonomethyl)benzene