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W. Chen et al. / Dyes and Pigments 95 (2012) 365e372
2.2. Route
stirred for 2 h at 80 ꢀC. Then the solution of 1-Bromobutane or 1-
Bromooctane (0.003 mol) in 10 mL DMF was added dropwise
with stirring. The mixture was heated to 125 ꢀC and reacted for 4 h.
The solvent was removed through vacuum evaporation and the
obtained mixture was purified by chromatographed on a silica gel
column to give yellow powder.
The synthesis routes are shown in Fig. 1.
2.2.1. Preparation of azo intermediate
1-Aminonaphthalene (2.86 g, 0.02 mol), water (8 mL) and
concentrated hydrochloric acid (8 g, 0.08 mol) were mixed in
100 mL flask with stirring, and heated to 80 ꢀC for 30 min. Then the
mixture was put into an ice-salt bath and stirred rapidly to
precipitate the hydrochloride salt as fine crystals. Keeping the
temperature at 0e5 ꢀC and the solution of sodium nitrite
(0.024 mol) in 10 mL water was added dropwise into the mixture
with stirring. After 30 min, urea (5 mg) was added to consume the
residual sodium nitrite and confirmed by the starch-iodide paper.
Then filtered and the diazonium salt solution was obtained. 8-
Hydroxyquinoline (2.90 g, 0.02 mol) and NaOH (2 g, 0.05 mol)
were dissolved in 200 mL water and the solution was kept at
0e5 ꢀC. The solution of the diazonium salt was slowly added and
reacted for 30 min, after adjusting pH to 7e8 and continue reaction
for 4 h, then the solution was filtered, and dried at 80 ꢀC under
vacuum at 10ꢁ3 Torr overnight. The obtained mixture was recrys-
tallized from ethanol to give yellow powder (yield 74.5%). 1H NMR
(Compound 2 yield 90%). 1H NMR (300 MHz, CDCl3)
d 9.43 (dd,
J ¼ 8.5, 1.5 Hz, 1H), 9.16e8.92 (m, 2H), 8.15 (d, J ¼ 8.6 Hz, 1H),
8.05e7.88 (m, 3H), 7.73e7.55 (m, 4H), 7.21 (d, J ¼ 8.7 Hz,1H), 4.33 (t,
J ¼ 7.0 Hz, 2H), 2.20e2.04 (m, 2H), 1.16 (t, J ¼ 7.4 Hz, 3H).
(Compound 3 yield 84%). 1H NMR (400 MHz, CDCl3)
d 9.47 (d,
J ¼ 8.6 Hz,1H), 9.11 (d, J ¼ 4.0 Hz,1H), 9.00 (d, J ¼ 8.4 Hz,1H), 8.16 (d,
J ¼ 8.6 Hz, 1H), 8.00 (d, J ¼ 8.1 Hz, 1H), 7.94 (t, J ¼ 7.6 Hz, 2H), 7.64
(ddd, J ¼ 22.8, 13.4, 7.3 Hz, 5H), 7.22 (d, J ¼ 8.7 Hz, 1H), 4.36 (t,
J ¼ 7.1 Hz, 2H), 2.17e2.04 (m, 2H), 1.63e1.52 (m, 2H), 1.39 (ddd,
J ¼ 32.6, 19.7, 10.5 Hz, 8H), 0.89 (t, J ¼ 6.6 Hz, 3H).
2.2.4. Preparation of compound 4
The synthesis of compound 4 is similar to compound 2 to give
compound 4 (orange powder, yield 79%). 1H NMR (400 MHz, CDCl3)
d
9.06 (dd, J ¼ 13.6, 8.5 Hz, 2H), 8.38 (d, J ¼ 8.4 Hz, 1H), 8.14 (dd,
J ¼ 8.3, 3.9 Hz, 1H), 8.03e7.92 (m, 3H), 7.74e7.56 (m, 5H), 6.96 (d,
J ¼ 8.5 Hz, 1H), 4.27 (t, J ¼ 6.4 Hz, 2H), 2.02e1.93 (m, 2H), 1.71e1.59
(m, 2H), 1.06 (t, J ¼ 7.4 Hz, 3H).
(400 MHz, DMSO)
8.68 (s,1H), 8.26 (d, J ¼ 9.1 Hz,1H), 7.96 (d, J ¼ 8.0 Hz, 1H), 7.91e7.80
(m, 2H), 7.60 (dt, J ¼ 14.8, 7.4 Hz, 4H), 6.68 (d, J ¼ 9.0 Hz, 1H).
d
9.28 (d, J ¼ 8.3 Hz, 1H), 8.93 (d, J ¼ 8.1 Hz, 1H),
2.3. Instruments
2.2.2. Preparation of compound 1
1H NMR spectrum was obtained on an Inova 400 MHz (or
300 MHz) FT-NMR spectrometer. UVevis absorption spectra were
recorded by a PerkineElmer Lambda-17 spectrophotometer at
room temperature. SEM images were taken on a Hitachi S-4700
scanning electron microscope. X-ray diffraction (XRD) analysis was
performed on film using a Shimadzu XRD-6000 spectrometer with
a Cu KR monochromatic radiation source at 40 kV and 30 mA. The
Azo intermediate (0.60 g, 0.002 mol) and potassium carbonate
anhydrous (0.414 g, 0.003 mol) were dissolved in 50 mL DMF, and
stirred for 2 h at 80 ꢀC. Then the solution of p-Toluenesulfonic Acid
Methyl Ester (0.56 g, 0.003 mol) in 10 mL DMF was added drop-
wise with stirring. The mixture was heated to 125 ꢀC and reacted
for 4 h. The solvent was removed through vacuum evaporation
and the obtained mixture was purified by chromatography on
a silica gel column to give yellow powder (yield 78%). 1H NMR
2q
angle was scanned from 5ꢀ to 30ꢀ.
(400 MHz, DMSO)
d
9.38 (d, J ¼ 8.6 Hz, 1H), 9.06e8.93 (m, 2H),
8.18 (dd, J ¼ 20.3, 8.3 Hz, 2H), 8.09 (d, J ¼ 7.9 Hz, 1H), 8.01 (d,
J ¼ 7.3 Hz, 1H), 7.73 (ddd, J ¼ 25.6, 14.0, 5.6 Hz, 4H), 7.43 (d,
J ¼ 8.6 Hz, 1H), 4.12 (s, 3H).
2.4. Fabrication and measurement of the memory devices
The indium-tin-oxide (ITO) glass was pre-cleaned with water,
acetone, and alcohol, in that order, in an ultrasonic bath for
30 min. The active organic film was deposited under high vacuum
about 10ꢁ6 Torr. The film thickness was about 80 nm. A layer of Al,
about 80 nm in thickness was thermally evaporated and deposited
2.2.3. Preparation of compounds 2 and 3
Azo intermediate (0.60 g, 0.002 mol) and potassium carbonate
anhydrous (0.414 g, 0.003 mol) were dissolved in 50 mL DMF, and
Fig. 1. The synthetic route of the Azo.