T.-S. Hsiao et al. / Dyes and Pigments 103 (2014) 161e167
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heated at 80 ꢀC for 20 h. The products were then cooled in an ice-
water bath and the precipitate was filtered and exhaustively
washed with cold methanol. The crude product was purified by
column chromatography (CH2Cl2) to give Cz-Bz (1.41 g; 40%). Mp:
between an o-amino ketone and acetyl group is the main reaction
to construct the desired quinoline rings in TPA-3Qu and TPA-3QuCz.
Primarily, the key intermediate TPA-Ac was prepared from the
simple FriedeleCrafts acetylation of TPA in the presence of acetyl
chloride/AlCl3. Friedländer condensation between TPA and o-ami-
nobenzophene (AB) afforded the first target compound of TPA-Ac.
For the preparation of another target compound TPA-3QuCz, the
key intermediate Cz-Pm containing o-amino ketone needs to be
synthesized by a three-step reaction procedure. The most versatile
and useful method for synthesizing o-amino ketones was a route
via the generation of benzisoxazole from an aromatic nitro com-
pound, followed by reductive cleavage of the benzisoxazole.
Accordingly, Cz-NO2 with one nitro group was synthesized by the
nucleophilic addition of carbazole to 1-fluoro-4-nitrobenzene (FN).
The resultant Cz-NO2 was then subjected to the Stille process, in
which Cz-NO2 was further reacted with benzyl nitrile to generate
CzBz with benzisoxazole ring, followed by the reduction with iron
to obtain the desired Cz-Pm. Friedländer condensation between Cz-
Pm and TPA-Ac resulted in the second target compound of TPA-
3QuCz. The molecular structures of all intermediates and final
products were confirmed by 1H NMR spectroscopy, mass spec-
trometry and elemental analysis.
221 ꢀC; 1H NMR (500 MHz, CDCl3):
d
7.26e7.35 (2H, tt, J ¼ 14, 7 Hz),
7.85e7.87 (1H, d, J ¼ 9 Hz), 8.01e8.03 (2H, d, J ¼ 5 Hz), 8.06 (1H, s),
8.17e8.18 (2H, d, J ¼ 7.5 Hz); m/z (EI MS): Calcd for C25H16N2O,
360.13; Found, 360.25; Anal. Calcd for C25H16N2O: C, 83.31; H, 4.47;
N, 7.77. Found: C, 83.35; H, 4.54; N, 7.63.
2.2.5. (2-Amino-5-(9H-carbazol-9-yl)phenyl)(phenyl)methanone
(Cz-Pm)
Iron powder (4 g, 71.63 mmol) and water (4 mL) were added to a
stirred suspension of Cz-Bz (1.41 g, 3.91 mmol) in acetic acid
(100 mL). The reaction mixtures were then heated at 95 ꢀC for 24 h
before cooled to room temperature to remove the iron powder by
filtration. The filtrates were then poured into water (500 mL) and
the filtered precipitate was collected and purified by column
chromatography (EtOAc/hexane: v/v ¼ 1/5) to give Cz-Pm (1.27 g,
90%). Mp: 258 ꢀC; 1H NMR (500 MHz, CDCl3):
d 7.14e7.52 (12H, m),
7.64 (1H, s), 7.79e7.85 (1H, t, J ¼ 15 Hz), 8.17e8.22 (2H, dd, J ¼ 24,
4.5 Hz), 10.26 (2H, s); m/z (EI MS): Calcd for C25H18N2O, 362.14;
Found, 362.10; Anal. Calcd for C25H18N2O: C, 82.85; H,5.01; N, 7.73.
Found: C, 82.82; H, 5.10; N, 7.66.
3.2. TPA-3QuCz and TPA-3Qu solid-state fluorescence behavior
2.2.6. Tris(4-(6-(9H-carbazol-9-yl)-4-phenylquinolin-2-yl)phenyl)
amine (TPA-3QuCz)
All fluorescence responses of TPA-3QuCz and TPA-3Qu towards
pressure and solvent-fuming processes were illustrated in Fig. 1.
Grinding the TPA-3QuCz powder in a mortar readily changed its
fluorescence color from green to orange and higher pressure load
(10 MPa) by pressing TPA-3QuCz in a hydraulic presser further
switched the fluorescence color to red. Grinding and high-pressure
loading also caused the changes of sample colors from yellow to
pale brown and then from pale brown to orange, respectively. The
pressed TPA-3QuCz can be reversed back to the pristine state
(yellow color and green fluorescence) by fuming the sample in a
close chamber saturated with triethylamine (TEA) vapor. In
contrast to the highly-sensitive TPA-3QuCz, grinding caused no
change on the crystalline TPA-3Qu and a higher pressure load of
10 MPa was required to produce noticeable changes on the color
(from yellow to brown) and the fluorescence (from yellow to or-
ange). The pressed TPA-3Qu can be also reversed to the initial state
by TEA-fuming. The above-mentioned color and fluorescence
changes are so significant that one can easily distinguish them by
direct observation.
The spectral responses towards compression were then moni-
tored. As illustrated in Fig. 2A, the PL emission spectrum of the
initial TPA-3QuCz showed only one broad band located at 500 nm
and grinding caused the emergence of a new band at 612 nm. High-
pressure (10 MPa) loading completely transformed all emission
bands into a new one located at a longer wavelength of 627 nm and
the resultant emission intensity is actually larger than the initial
and the ground samples. Subsequent TEA-fuming transformed the
pressed TPA-3QuCz into the pristine state in view that the TEA-
fumed sample emitted similarly with the initial sample. For TPA-
3Qu, a high-pressure load of 10 MPa was required to cause a
small bathochromic shift of 32 nm (Fig. 2B) in the emission spectra
and TEA-fuming also successfully transformed the pressed sample
to the original one as evidenced by the corresponding emission
spectra. For TPA-3QuCz and TPA-3Qu, the wavelength changes
caused by compression/TEA-fuming cycle can be repeated several
times without noticeable fatigue, which suggests the excellent
reversibility of both samples.
A solution of P2O5 (5 g, 20 mmol) in m-cresol (5 mL) was heated
at 135 ꢀC for 2 h. After cooling to room temperatures, Cz-Pm (1.27 g,
3.5 mmol) and TPA-Ac (0.43 g, 1.17 mmol) were added and the
whole mixture was heated at 135 ꢀC for another 12 h. After cooled
to room temperature, the products were precipitated from a trie-
thylamine/ethanol (v/v ¼ 1/9; 150 mL) solution to give TPA-3QuCz
(0.93 g, yield 60%). Tg: 200 ꢀC; FT-IR (KBr, cmꢁ1): 748, 836, 1178,
1228, 1282, 1314, 1330, 1360, 1394, 1448, 1492, 1510, 1542, 1588,
1620, 2351, 2852, 2924, 2952, 3043; 1H NMR (500 MHz, CDCl3):
d
7.30e7.33 (6H, t, J ¼ 5 Hz), 7.39e7.41 (6H, d, J ¼ 10 Hz), 7.44e7.71
(21H, m), 7.75e7.76 (6H, d, J ¼ 20 Hz), 7.94 (3H, d, J ¼ 20 Hz), 8.08e
8.1( 3H, d, J ¼ 10 Hz), 8.19 (6H, s), 8.25e8.26 (6H, d, J ¼ 5 Hz), 8.43e
8.45 (3H, d, J ¼ 10 Hz), 8.46e8.48 (3H, d, J ¼ 10 Hz); m/z (EI MS):
Calcd for C99H63N7, 1350.52; Found, 1350.50. Anal. Calcd for
C
99H63N7: C, 88.04 H, 4.7 N, 7.26. Found: C, 87.84, N, 4.81, H, 7.35.
2.2.7. Tris(4-(4-phenylquinolin-2-yl)phenyl)amine (TPA-3Qu)
A solution of P2O5 (15 g, 59.95 mmol) in m-cresol (15 mL) was
heated at 135 ꢀC for 2 h. After cooling to room temperatures, 2-
aminobenzophenone (2.31 g, 11.7 mmol) and TPA-Ac (1.45 g,
3.9 mmol) were added. The whole mixture was heated to 135 ꢀC for
another 12 h. The products after cooling were then precipitated
from a triethylamine/ethanol (v/v ¼ 10/90; 150 mL) solution to give
TPA-3Qu (2 g, yield 60%). Mp: 208 ꢀC; FT-IR (KBr, cmꢁ1): 701, 770,
840, 1151, 1177, 1237, 1285, 1319, 1357, 1455, 1488, 1509, 1539, 1590,
3030, 3055; 1H NMR (500 MHz, CDCl3):
d 7.34-7.36 (6H, d,
J ¼ 8.5 Hz), 7.45e7.59 (18H, m), 7.71e7.74 (3H, t, J ¼ 9 Hz), 7.8 (3H, s),
7.89e7.9 (3H, d, J ¼ 4.5 Hz), 8.12e8.14 (6H, d, J ¼ 8.5 Hz), 8.22e8.24
(3H, d, J ¼ 5 Hz); MS m/z: Calcd for C63H42N4, 854.34; Found, 854.24
(Mþ). Anal. Calcd for C63H42N4:C, 88.50; H, 4.95; N, 6.55. Found: C,
88.45 H, 4.90; N, 6.65.
3. Results and discussion
3.1. Synthesis and characterization
To clarify the possible molecular transformation modes during
compression, wide-angle X-ray diffraction (WAXD) analysis was
conducted. As expected, the initial TPA-3QuCz powders are
The target compounds TPA-3QuCz and TPA-3Qu were synthe-
sized according to Scheme 1, in which Friedländer condensation