238
P.-X. Liang et al. / Chinese Chemical Letters 25 (2014) 237–242
O
solution of triethylamine (6.00 mL) and THF (10.0 mL) under argon.
O
While stirring, the reaction mixture was heated to 70 8C, and
trimethylsiliconeacetylene (0.300 g, 3.00 mmol) was injected. After
15 min of stirring at 70 8C, the reaction was heated to 80 8C and
stirred overnight under argon atmosphere. The cooled reaction
mixture was diluted with CH2Cl2 and extracted with water. The
organic phase was dried over MgSO4, and the solvent was removed
under reduced pressure. The crude product was purified by column
chromatography (silica gel, petroleummether) to afford L1 (0.481 g,
88%). Hept-2-yne (0.270 g, 3.00 mmol), 1-ethynyl-4-pentylbenzene
(0.510 mg, 3.00 mmol), or 1-ethynyl-4-dipentylbenzene (0.735 g,
3.00 mmol) was injected correspondingly and with the same
procedure to afford L2 (0.371 g, 85%), L3 (0.616 mg, 82%), L4
(0.826 mg, 86%), respectively.
Br
a
b
Br
Br
R
R
O
Si
L1: R=
L2: R=
L3: R=
c
Phenyl(3,6,8-tris(trimethylsilylethynyl)pyren-1-yl)methanone
C5H11
(L1): 1H NMR (400 MHz, CDCl3):
d 0.37 (m, 27H, CH3), 7.50 (t, 2H,
benzene), 7.64 (t, 1H, benzene), 7.88 (d, 2H, J = 7.2 Hz, pyrene), 8.21
(s, 1H, pyrene), 8.28 (d, 1H, J = 9.2 Hz, pyrene), 8.35 (1H, s, pyrene),
8.53 (d, 1H, J = 9.2 Hz, pyrene), 8.71 (d, 2H, J = 7.2 Hz, pyrene). FT-IR
C5H11
L4: R=
R
(KBr, cmꢀ1):
n 2960, 2154, 1658, 1247, 854. MALDI-TOF-MS
Scheme 1. Structures of L1–L4 and the synthetic routes. (a) Benzoyl chloride, AlCl3,
CH2Cl2, 0 8C, 10 h; (b) Br2, nitrobenzene, 120 8C, 12 h; (c) Ethynyl, Pd(PPh3)2Cl2,
PPh3, CuI, NEt3, THF, 80 8C, 12 h.
(dithranol) (m/z): calcd. for C38H38Si3O: 598.8, found: 599.1
[M+1]+.
Phenyl(3,6,8-tris(butylethynyl)pyren-1-yl)methanone (L2): 1H
NMR (400 MHz, CDCl3):
d 1.02 (m, 9H, CH3), 1.60 (m, 6H, CH2),
ability of pyrene [10]. Meanwhile, through the introduction of
single carbonyl groups, an asymmtrical structure will be achieved.
We also expect that the long chain alkyl group will give better
solubility, excellent thermal stability, and a low tendency to
crystallize in devices.
1.76 (m, 6H, CH2), 2.64 (m, 6H, CH2), 7.48 (t, 2H, benzene), 7.62 (t,
1H, benzene), 7.68 (d, 2H, J = 7.2 Hz, benzene), 8.13 (s, 1H, pyrene),
8.19 (s, 1H, pyrene), 8.24 (d, 1H, J = 9.2 Hz, pyrene), 8.49 (d, 1H,
J = 9.2 Hz, pyrene), 8.63 (d, 1H, J = 9.2 Hz, pyrene), 8.62 (d, 1H,
J = 9.2 Hz, pyrene). FT-IR (KBr, cmꢀ1):
n 2941, 2219, 1658, 1228,
The target molecules were synthesized in three steps, including
the Friedel–Crafts acylation procedure [13] (a), the general
bromination procedure (b) and the Hagihara–Sonogashira cross-
coupling procedure [14] (c), as shown in Scheme 1. The final
asymmetrical pyrene derivatives L1–L4 were all characterized by
1H NMR, FT-IR and MS.
835, 686. MALDI-TOF-MS (dithranol) (m/z): calcd. for C41H38O:
550.6, found: 551.1 [M+1]+.
Phenyl(3,6,8-tris((4-pentylphenyl)-ethynyl)pyren-1-yl)metha-
none (L3): 1H NMR (400 MHz, CDCl3):
d 0.91 (m, 9H, CH3), 1.36 (m,
12H, CH2), 1.65 (6H, m, CH2), 2.65 (6H, m, CH2), 7.24 (m, 7H,
benzene), 7.50 (t, 2H, benzene), 7.62 (m, 6H, benzene), 7.92 (d, 2H,
J = 7.2 Hz, benzene), 8.16 (s, 1H, pyrene), 8.18 (d, 1H, J = 8.0 Hz,
pyrene), 8.26 (s, 1H, pyrene), 8.32 (d, 1H, J = 9.2 Hz, pyrene), 8.80
2.1.1. Synthesis of phenylpyren-1-yl-methanone (procedure a)
Pyrene (7.00 g, 34.8 mmol) and benzoyl chloride (5.40 g,
38.3 mmol) were dissolved in carbon disulfide (40 mL), the
mixture was cooled to 0 8C. After the gradual addition of AlCl3
(6.97 g, 52.2 mmol), the mixture was heated under reflux
overnight, then poured into ice water. The resulting mixture
was stirred until the color of the organic phase turned from red to
yellow. The layers were then separated. The aqueous phase was
extracted with dichloromethane. The combined organic phases
were dried with MgSO4, and the solvent was evaporated. The
residue was purified by column chromatography to yield phenyl-
pyren-1-yl-methanone (7.24 g, 68%).
(d, 2H, J = 9.2 Hz, pyrene). FT-IR (KBr, cmꢀ1):
1519, 1247, 827. MALDI-TOF-MS (dithranol) (m/z): calcd. for
62H56O: 822.8, found: 822.6 [M+1]+.
Phenyl
(3,6,1-tris((40-pentyldiphenyl-4-yl)ethynyl)pyren-1-yl)
methanone (L4): 1H NMR (400 MHz, CDCl3):
0.92 (m, 9H, CH3)
n 2931, 2192, 1658,
C
d
1.36 (m, 12H, CH2), 1.53 (m, 6H, CH2), 2.65 (m, 6H, CH2), 7.28 (m,
4H, benzene), 7.56 (m, 8H, benzene), 7.68 (m, 9H, benzene), 7.76
(m, 4H, benzene), 7.80 (d, 2H, J = 8.0 Hz, benzene), 7.94 (d, 2H,
J = 7.2 Hz, benzen), 8.32 (s, 1H, pyrene), 8.37 (d, 1H, J = 8.0 Hz,
pyrene), 8.52 (s, 1H, pyrene), 8.73 (d, 1H, J = 7.2 Hz, pyrene), 8.93
(m, 2H, pyrene). FT-IR (KBr, cmꢀ1):
n 2916, 2189, 1667, 1598, 1504,
1248, 820. MALDI-TOF-MS (dithranol) (m/z): calcd. for C80H68O:
1052.3, found: 1053.4 [M+1]+.
Compounds L1–L4 have good solubility in all common organic
solvents and relatively high melting points. For L2–L4, the melting
point increased from 83 8C to 203 8C with increasing lengths of the
rigid side chains.
2.1.2. Synthesis of phenyl-(3,6,8-tribromopyren-1-yl)-methanone
(procedure b)
Phenylpyren-1-yl-methanone (6.12 g, 20.0 mmol, 1 equiv.) was
dissolved in nitrobenzene. Under vigorous stirring, bromine
(3.00 mL, 60.0 mmol, 3 equiv.) was added slowly. After complete
addition, the temperature was increased to 160 8C and maintained
for 8 h. The cooled reaction suspension was poured into acetone,
and the precipitate filtered off. Further drying of the precipitate in
high vacuum gave the crude product phenyl-(3,6,8-tribromo-
pyren-1-yl)-methanone (9.34 g, 86%), which was used without
further purification. FT-IR (KBr, cmꢀ1): 1658, 1595, 1466, 1328,
1246, 1120, 1007, 953, 814, 697.
2.2. Self-assembly
Molecules L1–L4 with unbranched alkyl solubilizing groups
were found to dissolve in solvents, such as tetrahydrofuran
(THF), that have an affinity for alkyl and conjugated moieties
and can also accept hydrogen bonds to compete with that
molecule’s self-assembly. Micro-ribbon self-assembly of L4
molecules was achieved through the solvent-exchange method
in the solution phase, which involves transferring the molecule
from a good solvent (THF) into a poor solvent (ethanol, 25 mL).
2.1.3. Synthesis of the final compounds L1–L4 (procedure c)
Phenyl-(3,6,8-tribromopyren-1-yl)methanone (0.500 mg, 0.921
mmol), Pd(PPh3)2Cl2 (18.9 mg, 0.0270 mmol), CuI (5.16 mg, 0.0270
mmol), and PPh3 (16.2 mg, 0.0600 mmol) were added to a degassed
We drop cast 10
mL of the L4 solution onto a clean glass