M. Tian et al.
2h: White crystal (yield 63%) m.p. >300°C; 1H-NMR (400 MHz,
DMSO, TMS) δ: 7.12~7.16 (m, 8H), 7.39 (t, J =7.2 Hz, 4H),
7.64~7.66 (m, 2H), 7.73(d, J = 8.0 Hz 2H), 8.20 (d, J =8.8 Hz, 2H),
8.52 (d, J = 8.0 Hz, 2H), 8.86 (dd, J1 = 8.4Hz, J2 = 8.8 Hz, 2H);
MS (ESI) m/z: 462.4 (M++1). Anal.calcd for C33H23N3: C 85.87, H
5.02, N 9.11; found C 85.85, H 5.07, N 9.08.
(s, 1H); MS (ESI) m/z: 413.2 (M++1). Anal.calcd for C28H20N4: C
81.53, H 4.89, N 13.58; found C 81.52, H 4.86, N 13.62.
8: Compound 8 was prepared with the same procedures as 6
by reacting 0.44 g of 1,2-diaminobenzene (4 mmol) reacted with
1.29 g of 2 h (4 mmol). After regular work-up, a yellow crystal
was obtained (yield 61%). m.p. >300°C; 1H-NMR (400 MHz,
DMSO, TMS) δ: 7.26 (d, J = 5.2 Hz, 2H), 7.68~7.79 (m, 6H), 8.42
(d, J = 8.4, 2H), 8.51 (d, J = 8.4 Hz 2H), 8.63 (dd, J1 = 8.4 Hz, J2
= 16 Hz 2H), 8.89 (t, J = 7.6 Hz, 2H), 13.11 (s, 1H), 13.63 (s, 1H);
MS (ESI) m/z: 411.2 (M++1). Anal.calcd for C28H18N4: C 81.93, H
4.42, N 13.65; found C 81.98, H 4.40, N 13.62.
3: In a 100 mL round-bottomed flask fitted with an efficient
reflux condenser were placed 1.26 g of benzil (6 mmol), 0.27 g
of 1,4-benzenedicarboxaldehyde (2 mmol), 2.46 g of ammo-
nium acetate and 30 mL acetic acid. The reactants were mag-
netically stirred and refluxed for 6 h. The reaction was
monitored by the thin-layer chromatogaphy analysis. After
the reaction was complete, the mixture was poured into ice
water and solid precipitated out, which was filtered, washed
with water and ether, dried under reduced pressure. The
crude was purified by flash column chromatography on silica
gel and eluted with ethyl acetate/dichloromethane (1 : 10) to
give a yellow crystal (yield 71%). m.p. >300°C; 1H-NMR (400
MHz, DMSO, TMS) δ: 7.33 (t, J = 7.2 Hz, 4H), 7.44~7.48 (m,
8H), 7.52 (d, J = 7.2 Hz, 4H), 7.57 (d, J = 7.2 Hz, 8H), ,12.75
(s, 2H); MS (ESI) m/z: 515.2 (M++1). Anal.calcd for C36H26N4: C
84.02, H 5.09, N 10.89; found C 84.04, H 5.10, N 10.86.
4: Compound 4 was prepared with the same procedures as 3
by reacting 6 mmol of phenanthraquinone with 2 mmol of 1,4-
benzenedicarboxaldehyde. Yellow crystal (yield 60%). m.p.
>300°C; 1H-NMR (400 MHz, DMSO, TMS) δ: 7.67~7.78 (m, 8H),
8.52 (t, J = 7.2Hz, 4H), 8.60 (d, J = 7.9 Hz, 4H), 8.90 (d, J = 8.2
Hz 4H), 10.59 (s, 2H); MS (ESI) m/z: 510.2 (M++1). Anal.calcd
for C36H22N4: C 84.68, H 4.34, N 10.98; found C 84.62, H 4.37,
N 11.01.
10: In a 250 mL round-bottomed flask with a reflux condenser,
0.7 g of carbazole (4 mmol), 1.1 g of potassium tert-butoxide (10
mmol) and 100 mL dry DMF were placed. The reactants were
magnetically stirred and heated to 110°C for half an hour. Then
0.5 g of 4-fluoro-benzaldehyde was added to the mixture. The
reaction continued for 36 h and then the mixture was poured
into ice water, and extracted with dichloromethane. The crude
was purified by flash column chromatography on silica gel,
and eluted with dichloromethane/n-hexane (1 : 2) to obtain
the 4-N-carbazolylbenzaldehyde (yield 84%). Yellow crystal, m.
1
p. 278~281°C, H-NMR (400 MHz, DMSO, TMS) δ: 7.25 (m, 4H),
7.49 (m, 4H), 7.72 (d, J = 7.2 Hz, 2H), 7.85 (d, J = 8.8 Hz, 2H),
8.28 (d, J = 7.6 Hz, 2H) 8.48 (d, J = 8.4 Hz, 2H); 13.14 (s, 1H) MS
(ESI) m/z: 360 (M++1). Anal.calcd for C25H17N3: C 83.18, H 5.161,
N 11.73; found C 83.54, H 4.77, N 11.69.
Spectra measurements
5: Method A: Compound 5 was prepared by refluxing 4 mmol
of phenanthraquinone with 2 mmol of 1 h and 2.46 g of ammo-
nium acetate in 30 mL acetic acid for 6 h (yield 67%). Method B:
Compound 5 was prepared by refluxing 4 mmol benzil with 2
mmol of 2 h and 2.46 g of ammonium acetate in 30 mL acetic
acid for 6 h (yield 72%). Yellow crystal m.p. >300°C; 1H-NMR
(400 MHz, DMSO, TMS) δ: 7.33~7.43 (m, 6H), 7.48 (t, J = 7.6 Hz,
2H) 7.55 (d, J = 6.8 Hz, 2H), 7.59 (d, J = 7.6 Hz, 2H), 7.67 (t, J =
7.6, 2H), 7.78 (t, J = 7.8, 2H), 8.31 (d, J = 8.4, 2H), 8.42 (d, J =
8.4, 2H), 8.88 (dd, J1 = 8.4 Hz, J2 = 8.0 Hz, 2H); MS (ESI) m/z:
513.2 (M++1). Anal.Calcd for C36H24N4: C 84.35, H 4.72, N 10.93;
found C 84.29, H 4.74, N 13.97.
The fluorescence quantum yield was measured by a simple
method. One μg/mL quinine sulfate was dissolved in 0.05 mol/L
H2SO4 solution as the standard solution (Фfstd = 0.55), the sample
concentration was 2 × 10–6 mol/L.
The fluorescence quantum yield can be calculated in accordance
with the following formula:
n2
Fx Astd
ꢀ ꢀΦfstd
Fstd Ax
x
Φfx
¼
ꢀ
n2
std
where n is the refractive index of the solution, F is a fluorescent
integral area, A is the absorbance; nx is 1.44 as chloroform, nstd using
1.34 as the literature values (37). As the fluorescence excitation
wavelength is the cross-point of the UV-vis absorption curves
of the sample solution and standard solution, Astd and Ax can
be ignored.
6: In a 250 mL round-bottomed flask fitted with an efficient
reflux condenser were placed 0.44 g of 1,2-diaminobenzene
(4 mmol), 1.09 g of 4-(diphenylamino)benzaldehyde (4 mmol)
and 100 mL methanol. The reactants were magnetically stirred
and refluxed overnight. Then the mixture was poured into ice
water, and solid precipitated out, which was filtered, washed with
water and ether, dried under reduce pressure. The crude was
purified by flash column chromatography on silica gel and eluted
with ethyl acetate/dichloromethane (1 : 3) to give a white crystal
Results and discussion
Synthesis
1
(yield 77%). m.p. 278~280°C; H-NMR (400 MHz, DMSO, TMS) δ:
The condensation o-dicarbonyl compounds with aldehydes and
ammonia or ammonium acetate in acetic acid is commonly used
for the formation of the imidazole ring (9), we chose this strategy
for the preparation of the 19 imidazoles. Benzil and benzalde-
hydes were condensed to provide multi-aryl imidazoles 1a–1h
in good yields. As for the phenanthroimidazole derivatives, we
substituted benzil with phenanthraquinone, and using the same
procedure, the multi-aryl imidazoles 2a–2h were obtained
(Fig. 2).
7.06 (d, J = 7.6, 2H), 7.15 (m, 8H), 7.36 (t, J = 8 Hz, 4H), 7.56 (s,
2H), 8.07 (d, 2H), 12.78 (s, 1H); MS (ESI) m/z: 362.3 (M++1). Anal.
calcd for C25H19N3: C 83.07, H 5.30, N 11.63; found C 83.10, H
5.26, N 11.64.
7: Compound 7 was prepared with the same procedures as 6
by reacting 0.44 g of 1,2-diaminobenzene (4 mmol) with 1.30 g
of 1 h (4 mmol). After regular work-up, a yellow crystal was
obtained (yield 68%). m.p. >300°C; 1H-NMR (400 MHz, DMSO,
TMS) δ: 7.23 (dd, J1 = 2.8 Hz, J2 = 3.2 Hz, 2H), 7.75 (m, 6H), 7.59
(m, 6H), 8.31 (dd, J1 =8.4 Hz, J2 =12.4 Hz, 4H), 12.9 (s, 1H), 13.0
However, the reaction of benzil with 1,4-benzenedicarboxaldehyde
under the standard reaction condition afforded a mixture of
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Luminescence 2014; 29: 540–548