Synthesis and optical properties of 6,10-dihydrofluoreno[2,3-d:6,7- d′]diimidazole derivatives

Article abstract of DOI:10.1016/j.dyepig.2012.03.004

A series of 10,10-dioctyl-3,6-dihydrofluoreno[2,3-d:6,7-d′] diimidazole derivatives were conveniently synthesized by condensation of the key intermediate 2,3,6,7-tetraamino-9,9-dioctylfluorene (TADOF) with aldehydes under very mild conditions. All of the target compounds were characterized using ¹H NMR, ¹³C NMR, and elemental analysis. The crystal structure of 3,6-dibenzyl-10,10-dioctyl-2,7-diphenyl-6,10-dihydro-3H-fluoreno[2, 3-d:6,7-d′]diimidazole was determined as triclinic, space group P-1 type, using single X-ray crystallography. For seventeen samples, UV-visible absorption maximum wavelength (λ_max), fluorescence excitation wavelength (λ_ex), fluorescence emission wavelength (λ _em) and fluorescence quantum yield (φ_FL) were measured in dilute dichloromethane solution and in the solid state. These compounds possess a medium strong blue fluorescence-emitting ability with φ_FL values in the region of 0.30-0.89 and structure-optical behavior characteristics were discussed.

Full text of DOI:10.1016/j.dyepig.2012.03.004

Dyes and Pigments 94 (2012) 583e591
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Dyes and Pigments
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Synthesis and optical properties of 6,10-dihydrofluoreno[2,3-d:6,7-d0]diimidazole
derivatives
*
**
Hong-Fang Chen, Yong-Mei Cui , Jian-Guang Guo, Hai-Xia Lin
Department of Chemistry, College of Sciences, Shanghai University, 99 Shangda Road, Baoshan District, Shanghai 200444, PR China
a r t i c l e i n f o
a b s t r a c t
A series of 10,10-dioctyl-3,6-dihydrofluoreno[2,3-d:6,7-d0]diimidazole derivatives were conveniently
synthesized by condensation of the key intermediate 2,3,6,7-tetraamino-9,9-dioctylfluorene (TADOF)
with aldehydes under very mild conditions. All of the target compounds were characterized using 1H
NMR, 13C NMR, and elemental analysis. The crystal structure of 3,6-dibenzyl-10,10-dioctyl-2,7-diphenyl-
6,10-dihydro-3H-fluoreno[2,3-d:6,7-d0]diimidazole was determined as triclinic, space group P-1 type,
using single X-ray crystallography. For seventeen samples, UVevisible absorption maximum wavelength
Article history:
Received 5 January 2012
Received in revised form
22 February 2012
Accepted 5 March 2012
Available online 21 March 2012
(
lmax), fluorescence excitation wavelength (lex), fluorescence emission wavelength (lem) and fluores-
Keywords:
Synthesis
Fluorene
cence quantum yield (4FL) were measured in dilute dichloromethane solution and in the solid state.
These compounds possess a medium strong blue fluorescence-emitting ability with 4 values in the
FL
region of 0.30e0.89 and structure-optical behavior characteristics were discussed.
Ó 2012 Elsevier Ltd. All rights reserved.
Imidazole
Synthesis
UV absorption
Fluorescence
1. Introduction
and polymer fields, fluorescent whitening agents and photo-
conducting materials [36e38]. Imidazole derivatives are impor-
Since the reports by C. W. Tang [1] and J. H. Burroughes [2],
organic and polymer light-emitting diode (LED) materials have
received considerable attention due to their potential application
in various displays [3e8], and enormous efforts have been made
toward the development of new high-performance materials with
desirable properties [9e23]. Due to their rigid planarized oligo-
phenyl unit within the backbone as well as the possibility of facile
functionalization at the methylene bridge, fluorene-based deriv-
atives, including polymers and oligomers, exhibit unique photo-
luminescent properties and have been widely used as lumin
escent materials [24e28], as well as carrier transport materials
for filed effect transistors (FETs) [29e31]. However, small-
molecule fluorene derivatives with good thermal stability and
high photoluminescence (PL) efficiency have been little reported
[32e35]. Fluorescent heterocyclic compounds are of interest in
many areas such as emitters for electroluminescence devices,
molecular probes for biochemical research, in traditional textile
tant five-membered nitrogen-containing electron-accepting
heterocyclic compounds with broad spectrum of biological
activities and have potential applications in electrical and optical
materials. Fluorescent characteristics rely largely on molecular
structure and molecular assembly. Changes in the substitutional
groups and substitution pattern, conjugation, and molecular
electronic structure can bring about very different optical and
physical properties for such materials. There is presently great
interest to increase the structural or spatial dimensions of
p-
conjugated molecules in order to tune and acquire more favorable
physical properties.
We recently presented detailed structureeproperty relationship
investigations into new fluorene derivatives based on 3,9-dihydro-
9,9-dioctylfluoreno[3,2-d]imidazole (DOFI) and found that their
electronic absorption and emission profiles exhibited sensitivity to
functional group substitution pattern [39]. As an expanded
continuation of our studies related to the synthesis and optical
properties of heterocycle-based chromophores, in this paper, we
present the initial synthesis and characterization of a series of novel
6,10-dihydrofluoreno[2,3-d:6,7-d0]diimidazole derivatives. It is
envisioned that the fusion of another aryl-imidazole unit into the
skeleton can improve their photo-electric properties. Similarly, two
octyl groups were introduced to the C-9 position of the fluorene
* Corresponding author. Tel.: þ86 21 66132190; fax: þ86 21 66134594.
** Corresponding author. Tel.: þ86 21 66136050; fax: þ86 21 66133039.
E-mail addresses: ymcui80@gmail.com, ymcui@shu.edu.cn (Y.-M. Cui),
haixialin@staff.shu.edu.cn (H.-X. Lin).
0143-7208/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
doi:10.1016/j.dyepig.2012.03.004

584
H.-F. Chen et al. / Dyes and Pigments 94 (2012) 583e591
moiety to increase solubility as well as to release intermolecular
p-
2.2. Synthesis
p
stacking. And we focused our attention on 10,10-dioctyl-3,6-
dihydrofluoreno[2,3-d:6,7-d0]diimidazoles (DOFDIs) with different
terminal aryl ring to investigate their UVevisible absorption and
fluorescence characters. The synthetic pathway and the structures
of the target molecules are shown in Figs. 1 and 2.
2.2.1. General procedure for the synthesis of 3a-o
To a suspension of 3,6-dinitro-9,9-dioctylfluorene-2,7-diamine
[40] (230 mg, 0.45 mmol) in ethanol (30 mL) was added Pd(OH)2
(50 mg, 0.16 mmol). The reaction mixture was heated to 90 ꢀC with
stirring, and then hydrazine hydrate (1.32 g, 26.4 mmol) was added
dropwise. The reaction mixture was stirred at 90 ꢀC for 20 min, and
then cooled, filtered and the mixture was extracted with AcOEt for
three times. The combined organic layer was washed with brine,
dried over Na2SO4, filtered, and then the solvent was evaporated in
vacuum. The obtained yellow residue 2,3,6,7-tetraamino-9,9-
dioctylfluorene 2a was directly used for next step without further
purification.
A mixture of the corresponding aldehyde (0.889 mmol) and 2a
obtained above in 1,4-dioxane was refluxed for about 10 h. The
solvent was removed under vacuum and the residue was purified
by flash column chromatography using petroleum ether/ethyl
acetate as eluent to afford the desired compounds 3a-o in 20e75%
yields for two steps.
2. Experimental
2.1. Reagents and instruments
Commercially available reagents were purchased and were used
without further purification unless otherwise mentioned. 1H NMR
and 13C NMR spectra were recorded on a Bruker Avance (500 MHz)
spectrometer in CDCl3 or DMSO-d6, unless otherwise noted.
Chemical shifts are reported in parts per million (ppm) and
coupling constants (J) are reported in Hertz (Hz). Coupling patterns
are described by abbreviations: s (singlet), d (doublet), t (triplet), m
(multiplet), br (broad). Chemical shifts were reported in the scale
relative to CHCl3 (7.26 ppm) or DMSO-d6 (2.50 ppm) for 1H NMR,
and to CDCl3 (77.16 ppm) or DMSO-d6 (39.70 ppm) for 13C NMR, as
internal references. The center line of the multiplets of DMSO-d6
was defined as 2.50 for 1H NMR. Silica gel plate GF254 was used for
thin layer chromatography (TLC) and silica gel 300e400 mesh was
used for flash column chromatography. Melting points were
measured on a Digital Melting Point Apparatus without correction.
Yields are shown in terms of those isolated pure materials. The
absorption and fluorescence spectra were recorded using a UV-
2501Pc spectrophotometer and an RF-5301 fluorescence spectro-
photometer. Elemental analysis was performed on an Elementary
Vario EL (Germany) instrument. MS were taken with an Agilent
LCMS-1100.
2.2.1.1. 10,10-Dioctyl-2,7-diphenyl-6,10-dihydro-3H-fluoreno[2,3-
d:6,7-d0]diimidazole (3a). White powder, yield 60%. Mp 189e190 ꢀC
1H NMR (500 MHz, DMSO-d6):
d ppm 0.55 (m, 4H), 0.71 (t,
J ¼ 7.1 Hz, 6H), 0.97e1.07 (m, 20H), 2.06 (m, 4H), 7.45 (m, 1H),
7.48e7.51 (m, 2H), 7.55e7.58 (m, 4H), 7.62 (m, 1H), 7.89 (d,
J ¼ 11.1 Hz, 1H), 8.11e8.15 (m, 1H), 8.17e8.20 (m, 4H), 12.81e12.92
(m, 2H). 13C NMR (125 MHz, DMSO-d6):
d ppm 13.9, 22.1, 23.7, 28.7,
28.9, 29.5, 31.2, 41.4, 53.5, 101.4, 101.6, 105.2, 109.3, 112.8, 126.3,
129.0, 129.6, 130.6, 134.9, 136.2, 136.9, 137.1, 143.9, 144.8, 145.3,
145.9, 146.4, 151.2. Anal. calculated for C43H50N4: C, 82.91; H, 8.09;
N, 8.99. Found: C, 82.78; H, 7.96; N, 9.16.
n-C8H17
n-C8H17
n-C8H17
n-C8H17
.
NH2NH2 H2O, Pd(OH)2
H2N
O2N
H2N
H2N
NH2
NO2
NH2
NH2
EtOH,reflux
1
TADOF, 2a
n-C8H17
n-C8H17
n-C8H17
n-C8H17
100oC
1,4-dioxane
+
N
R CHO
N
H2N
H2N
NH2
NH2
R
R
N
H
N
H
2a
3a-o
Fig. 1. The synthetic route of the 6,10-dihydrofluoreno[2,3-d:6,7-d0]diimidazole derivatives 3a-o.

H.-F. Chen et al. / Dyes and Pigments 94 (2012) 583e591
585
Fig. 2. The synthesis of compounds 4a-b.
2.2.1.2. 10,10-Dioctyl-2,7-di(thiophen-2-yl)-6,10-dihydro-3H-fluo-
reno[2,3-d:6,7-d0]diimidazole (3b). Light yellow powder, yield 40%.
7.58e7.59 (m, 2H), 7.63 (m, 2H), 7.66e7.71 (m, 3H), 7.96 (m, 1H),
8.01 (d, J ¼ 7.6 Hz, 2H), 8.05e8.07 (m, J ¼ 7.9 Hz, 4H), 8.26 (s, 1H),
9.28 (m, 2H), 12.97e13.02 (m, 2H). 13C NMR (125 MHz, DMSO-d6):
Mp 145e147 ꢀC 1H NMR (500 MHz, DMSO-d6):
d ppm 0.51 (m, 4H),
0.70 (t, J ¼ 7.2 Hz, 6H), 0.94e1.00 (m, 20H), 2.01 (m, 4H), 7.23 (m,
2H), 7.41 (s, 1H), 7.55 (s, 1H), 7.69e7.71 (m, 2H), 7.81e7.84 (m, 2H),
7.87 (s, 1H), 8.07 (m, 1H), 12.85e12.94 (m, 2H). 13C NMR (125 MHz,
d ppm 13.9, 22.1, 23.7, 28.7, 28.9, 29.1, 29.6, 31.2, 41.5, 53.6, 101.6,
105.2, 109.5, 112.9, 125.4, 126.4, 126.7, 127.0, 127.7, 128.5, 130.0,
130.7, 133.8, 134.4, 136.3, 137.1, 144.0, 144.8, 145.4, 146.0, 146.6,
151.4. Anal. calculated for C51H54N4: C, 84.72; H, 7.53; N, 7.75.
Found: C, 84.52; H, 7.68; N, 7.64.
DMSO-d6):
d ppm 13.9, 14.0, 20.1, 22.1, 22.2, 23.7, 28.7, 28.8, 29.1,
29.4, 29.5, 31.2, 31.4, 31.6, 41.2, 41.3, 53.7, 101.2, 101.5, 105.0, 109.0,
112.5, 126.3, 128.3, 128.5, 134.2, 134.6, 134.8, 136.2, 137.0, 137.1,
143.6, 143.9, 144.9, 145.4, 146.0, 146.5, 147.0, 147.1. Anal. calculated
for C39H46N4S2 C, 73.77; H, 7.30; N, 8.82. Found: C, 73.74; H, 7.27; N,
8.90.
2.2.1.6. 10,10-Dioctyl-2,7-di((E)-styryl)-6,10-dihydro-3H-fluoreno
[2,3-d:6,7-d0]diimidazole (3f). Yellow powder, yield 38%. Mp
176e178 ꢀC 1H NMR (500 MHz, DMSO-d6):
d ppm 0.51 (m, 4H), 0.69
(t, J ¼ 7.0 Hz, 6H), 0.93e0.98 (m, 20H), 1.97 (m, 4H), 7.21e7.24 (m,
1H), 7.28 (s, 1H), 7.33 (m, 2H), 7.41 (m, 4H), 7.50 (m, 2H), 7.65e7.68
(m, 5H), 7.95 (s, 2H), 12.65 (m, 2H). 13C NMR (125 MHz, DMSO-d6):
2.2.1.3. 2,7-Bis(5-methylfuran-2-yl)-10,10-dioctyl-6,10-dihydro-3H-
fluoreno[2,3-d:6,7-d0]diimidazole (3c). Yellow powder, yield 36%.
Mp 181e183 ꢀC 1H NMR (500 MHz, DMSO-d6):
d
ppm 0.51 (m, 4H),
d ppm 13.9, 14.2, 20.8, 22.1, 23.7, 28.7, 28.9, 29.2, 29.5, 31.3, 41.4,
0.71 (t, J ¼ 7.1 Hz, 6H), 0.92e1.03 (m, 20H), 1.99e2.01 (m, 4H), 2.42
(s, 6H), 6.34 (m, 2H), 7.06 (m, 2H), 7.39 (s, 1H), 7.52 (s, 1H), 7.80 (s,
1H), 8.00 (s, 1H), 12.74e12.79 (m, 2H). 13C NMR (125 MHz, DMSO-
53.5, 118.0, 126.3, 127.0, 128.8, 129.0, 133.6, 136.0, 136.8, 145.7, 151.0.
Anal. calculated for C47H54N4: C, 83.64; H, 8.06; N, 8.30. Found: C,
83.92; H, 8.02; N, 8.04.
d6): d ppm 13.6, 13.9, 22.1, 23.7, 28.7, 28.9, 29.2, 29.5, 31.2, 41.3, 53.4,
101.3, 105.1, 108.6, 111.1, 112.4, 134.1, 136.2, 136.7, 143.8, 144.4, 153.5.
Anal. calculated for C41H50N4O2 C, 78.06; H, 7.99; N, 8.88. Found: C,
78.18; H, 8.02; N, 8.68.
2.2.1.7. 10,10-Dioctyl-2,7-di-p-tolyl-6,10-dihydro-3H-fluoreno[2,3-
d:6,7-d0]diimidazole (3g). White solid, yield 75%. Mp 154e156 ꢀC 1H
NMR (500 MHz, DMSO-d6):
d
ppm 0.52 (m, 4H), 0.68 (t, J ¼ 7.1 Hz,
6H), 0.93e1.03 (m, 20H), 1.99 (m, 4H), 2.37 (s, 6H), 7.20e7.25 (m,
1H), 7.35 (d, J ¼ 7.9 Hz, 4H), 7.42 (s,1H), 7.59 (s, 1H), 7.86 (s,1H), 8.09
(d, J ¼ 7.7 Hz, 4H), 12.75e12.83 (m, 1H). 13C NMR (125 MHz, DMSO-
2.2.1.4. 10,10-Dioctyl-2,7-di(pyridin-2-yl)-6,10-dihydro-3H-fluoreno
[2,3-d:6,7-d0]diimidazole (3d). Light yellow powder, yield 46%. Mp
114e115 ꢀC 1H NMR (500 MHz, DMSO-d6):
d
ppm 0.48 (m, 4H), 0.62
d6): d ppm 13.9, 21.1, 22.1, 23.7, 28.7, 28.9, 29.5, 31.2, 41.4, 53.5,101.3,
(m, J ¼ 7.1 Hz, 6H), 0.87e0.98 (m, 20H), 1.91e1.96 (m, 4H), 7.45 (m,
3H), 7.65 (s, 1H), 7.83e7.90 (m, 1H), 7.95 (m, 2H), 8.10e8.18 (m, 1H),
8.34 (m, 2H), 8.70 (m, 2H),13.12 (m, 2H). 13C NMR (125 MHz, DMSO-
105.1, 109.0, 112.6, 126.3, 126.7, 127.9, 128.9, 129.6, 134.8, 136.3,
137.0, 139.3, 142.7, 144.0, 144.7, 145.3, 151.4. Anal. calculated for
C45H54N4: C, 83.03; H, 8.36; N, 8.61. Found: C, 83.18; H, 8.52; N, 8.31.
d6):
d ppm 13.9, 22.0, 23.7, 28.7, 28.9, 29.5, 31.2, 41.5, 53.5, 102.0,
105.8, 109.5, 113.2, 121.3, 124.4, 134.9, 136.4, 137.5, 144.0, 144.3,
145.1, 145.6, 146.5, 147.1, 148.8, 149.4, 150.8. Anal. calculated for
C41H48N6 C, 78.81; H, 7.74; N, 13.45. Found: C, 78.95; H, 7.82; N,
13.64.
2.2.1.8. 2,7-Bis(4-methoxyphenyl)-10,10-dioctyl-6,10-dihydro-3H-
fluoreno[2,3-d:6,7-d0]diimidazole (3h). White powder, yield 40%.
Mp 160e162 ꢀC 1H NMR (500 MHz, DMSO-d6):
d ppm 0.51(m, 4H),
0.67 (m, 6H), 0.92e1.03 (m, 20H), 1.97 (m, 4H), 3.82 (s, 6H), 7.11 (m,
4H), 7.50 (m, 2H), 7.90 (m, 2H), 8.14 (m, 4H), 12.74 (m, 2H). 13C NMR
2.2.1.5. 2,7-Di(naphthalen-1-yl)-10,10-dioctyl-6,10-dihydro-3H-fluo-
reno[2,3-d:6,7-d0]diimidazole (3e). Light yellow powder, yield 44%.
(125 MHz, DMSO-d6): d ppm 13.9, 22.1, 23.7, 28.7, 28.9, 29.6, 31.3,
41.4, 53.5, 55.4, 101.2, 108.2, 112.3, 114.5, 123.1, 127.9, 134.9, 136.5,
145.2, 151.4, 160.5. Anal. calculated for C45H54N4O2: C, 79.14; H,
7.97; N, 8.20; O, 4.69. Found: C, 79.35; H, 8.45; N, 8.02.
Mp 180e192 ꢀC 1H NMR (500 MHz, DMSO-d6):
d
ppm 0.55 (s, 4H),
0.65 (t, J ¼ 7.0 Hz, 6H), 0.93e1.02 (m, 20H), 2.00 (m, 4H), 7.47 (s,1H),

586
H.-F. Chen et al. / Dyes and Pigments 94 (2012) 583e591
2.2.1.9. 2,7-Bis(4-nitrophenyl)-10,10-dioctyl-6,10-dihydro-3H-fluo-
reno[2,3-d:6,7-d0]diimidazole (3i). Yellow powder, yield 65%. Mp
4H), 0.69 (t, J ¼ 7.1 Hz, 6H), 0.94e1.04 (m, 20H), 2.02e2.03 (m, 4H),
7.32e7.35 (m, 4H), 7.49e7.50 (m, 1H), 7.60e7.66 (m, 2H), 7.69 (m,
1H), 7.97 (s, 1H), 8.19 (s, 1H), 12.81e12.90 (m, 2H). 13C NMR
187e188 ꢀC 1H NMR (500 MHz, DMSO-d6):
d ppm0.47 (m, 4H), 0.63
(t, J ¼ 6.9 Hz, 6H), 0.82e0.99 (m, 20H), 1.96 (m, 4H), 7.51 (s, 1H), 7.67
(s, 1H), 7.98 (m, 1H), 8.20e8.24 (m, 1H), 8.39e8.40 (m, 4H),
8.43e8.45 (m, 4H), 13.24e13.32 (m, 2H). 13C NMR (125 MHz,
(125 MHz, DMSO-d6): d ppm 13.9, 22.0, 23.7, 28.7, 28.8, 29.6, 31.2,
41.4, 53.6, 101.8, 102.0, 105.4, 105.5, 109.3, 109.4, 109.5, 109.7, 112.4,
112.6,113.1,132.3,134.2,134.4,134.6,136.2,136.4,137.2,137.4, 140.9,
141.1, 143.4, 143.6, 143.8, 144.9, 145.4, 146.3, 146.9, 159.2, 159.3,
161.2, 161.3. Anal. calculated for C43H46F4N4: C, 74.33; H, 6.67; N,
8.06 Found: C, 74.53; H, 6.58; N, 8.12.
DMSO-d6):
d ppm 13.9, 22.0, 23.7, 28.7, 28.9, 29.5, 31.2, 41.3, 53.7,
102.0, 102.3, 105.6, 110.1, 113.4, 124.1, 124.4, 127.2, 135.3, 135.7, 136.4,
137.8, 138.0, 144.1, 144.5, 145.6, 146.1, 147.6, 149.1. Anal. calculated
for C43H48N6O4: C, 72.45; H, 6.79; N, 11.79. Found: C, 72.48; H, 6.62;
N, 11.90.
2.2.1.15. 2,7-Bis(4-chlorophenyl)-10,10-dioctyl-6,10-dihydro-3H-flu-
oreno[2,3-d:6,7-d0]diimidazole (3o). White powder, yield 46%. Mp
2.2.1.10. 10,10-Dioctyl-2,7-bis(4-(trifluoromethyl)phenyl)-6,10-
dihydro-3H-fluoreno[2,3-d:6,7-d0]diimidazole (3j). Light yellow
powder, yield 20%. Mp 181e182 ꢀC 1H NMR (500 MHz, DMSO-d6):
170e171 ꢀC 1H NMR (500 MHz, DMSO-d6):
d ppm 0.48 (m, 4H), 0.65
(m, 6H), 0.89e1.01 (m, 20H), 1.97 (m, 4H), 7.45 (s, 1H), 7.61 (m, 5H),
7.91 (s, 1H), 8.12e8.15 (m, 1H), 8.21 (m, 4H), 12.92e13.00 (m, 2H).
d
ppm 0.49 (m, 4H), 0.65 (t, J ¼ 7.1 Hz, 6H), 0.89e0.97 (m, 20H), 1.98
13C NMR (125 MHz, DMSO-d6):
d ppm 13.9, 22.1, 23.7, 28.7, 28.9,
(m, 4H), 7.49 (s, 1H), 7.66 (s, 1H), 7.90e7.91 (m, 4H), 7.95e7.97 (m,
29.5, 31.2, 41.4, 53.5, 101.5, 101.8, 105.3, 109.5, 112.8, 128.0, 129.1,
129.4,134.3,134.9,135.2,136.3,137.1,137.3,143.8,144.1,145.0,145.5,
146.7, 150.2. Anal. calculated for C43H48Cl2N4: C, 74.66; H, 6.99; N,
8.10. Found: C, 74.18; H, 7.11; N, 8.05.
1H), 8.18e8.22 (m, 1H), 8.40e8.42 (m, 4H), 13.10e13.19 (m, 2H). 13C
NMR (125 MHz, DMSO-d6):
d ppm 13.9, 22.0, 23.7, 28.7, 28.8, 29.5,
31.2, 41.4, 53.6, 101.8, 102.1, 105.5, 109.6, 109.8, 113.1, 121.0123.2,
125.4, 126.0, 126.9, 127.5, 129.3, 129.6, 134.3, 135.1, 135.4, 136.5,
136.7, 137.4, 137.6, 143.9, 144.2, 145.2, 145.8, 146.7, 147.2, 149.7. Anal.
calculated for C45H48F6N4: C, 71.22; H, 6.38; N, 7.38. Found: C, 71.35;
H, 6.54; N, 7.21.
2.2.2. Synthesis of 4a and 4b
To a suspension of 3,6-dinitro-9,9-dioctylfluorene-2,7-diamine
1 (575 mg, 1.12 mmol) in ethanol (80 mL) was added Sn powder
(802 mg, 6.8 mmol). The reaction mixture was heated to 90 ꢀC with
stirring, and concentrated hydrochloric acid (3 mL) was added to
the solution by portions. And the solution was continued to be
heated under reflux for about 30 min until 1 disappeared. The
mixture was filtered and extracted with AcOEt for three times. The
combined organic layer was washed with brine, dried over Na2SO4,
filtered, and then the solvent was evaporated in vacuum. The
obtained yellow residue 2,3,6,7-tetraamino-9,9-dioctylfluorene 2b
was directly used for next step without further purification.
A mixture of the above obtained 9,9-dioctylfluorene-2,3,6,7-
tetraamine (2b) and benzaldehyde (235 mg, 2.22 mmol) were
heated to 100 ꢀC in 1,4-dioxane for about 10 h. The solvent was
removed under vacuum and the residue was purified by flash
column chromatography using petroleum ether/ethyl acetate as
eluent to afford the desired compounds.
2.2.1.11. 2,7-Bis(2-fluorophenyl)-10,10-dioctyl-6,10-dihydro-3H-fluo-
reno[2,3-d:6,7-d0]diimidazole (3k). White powder, yield 51%. Mp
130e131 ꢀC 1H NMR (500 MHz, DMSO-d6):
d ppm 0.50 (m, 4H), 0.64
(t, J ¼ 7.2 Hz, 6H), 0.89e0.93 (m, 20H), 1.96e1.97 (m, 4H), 7.37 (m,
2H), 7.40 (d, J ¼ 8.8 Hz, 1H), 7.42 (d, J ¼ 8.8 Hz, 1H), 7.50e7.52 (m,
3H), 7.65 (s, 1H), 7.91e7.95 (m, 1H), 8.12e8.17 (m, 1H), 8.28 (m, 2H),
12.53e12.61 (m, 2H). 13C NMR (125 MHz, DMSO-d6):
d ppm 13.8,
22.0, 23.7, 28.7, 28.9, 29.5, 31.2, 41.5, 53.5, 102.0, 105.7, 109.2, 112.8,
116.4, 116.6, 118.5, 125.1, 126.1, 130.1, 131.5, 135.0, 136.5, 137.1, 143.4,
145.6, 146.4, 158.5, 160.5. Anal. calculated for C43H48F2N4: C, 78.39;
H, 7.34; N, 8.50. Found: C, 78.65; H, 7.23; N, 8.38.
2.2.1.12. 2,7-Bis(3-fluorophenyl)-10,10-dioctyl-6,10-dihydro-3H-fluo-
reno[2,3-d:6,7-d0]diimidazole (3l). White powder, yield 48%. Mp
148e149 ꢀC 1H NMR (500 MHz, DMSO-d6):
d ppm 0.50 (m, 4H),
0.65e0.70 (m, 6H), 0.91e1.01 (m, 20H), 1.97e1.99 (m, 4H),
7.29e7.32 (m, 2H), 7.47 (s, 1H), 7.57e7.61 (m, 3H), 7.64 (s, 1H),
7.95e8.00 (m, 2H), 8.04e8.06 (m, 2H), 8.14e8.19 (m, 1H),
2.2.2.1. 3-Benzyl-10,10-dioctyl-2,7-diphenyl-6,10-dihydro-3H-fluo-
reno[2,3-d:6,7-d0]diimidazole (4a). Light yellow powder, yield
19e23%. Mp 89e91 ꢀC 1H NMR (500 MHz, DMSO-d6):
d ppm 0.64
12.94e13.03 (m, 2H). 13C NMR (125 MHz, DMSO-d6):
d
ppm 13.9,
(s, 4H), 0.79 (m, 6H), 0.99e1.06 (m, 20H), 1.96 (m, 4H), 5.48 (s, 1H),
5.52 (s, 1H), 7.08e7.12 (m, 1H), 7.21e7.23 (m, 2H), 7.29e7.32 (m,
2H), 7.34 (m, 1H), 7.35e7.36 (m, 1H), 7.38e7.42 (m, 6H), 7.50 (s,
1H), 7.67e7.71 (m, 4H), 8.18 (d, J ¼ 7.2 Hz, 1H), 12.15 (s, 1H). 13C
22.0, 23.7, 28.7, 28.8, 29.5, 31.2, 41.3, 53.6, 101.9, 105.3, 109.6, 113.0,
113.3, 114.2, 116.0, 116.4, 122.4, 125.2, 130.7, 131.1, 132.8, 134.9, 136.4,
137.2, 139.9, 142.5, 143.7, 145.1, 145.6, 147.0, 150.0, 151.7, 161.6, 163.5.
Anal. calculated for C43H48F2N4: C, 78.39; H, 7.34; N, 8.50. Found: C,
78.49; H, 7.39; N, 8.27.
NMR (125 MHz, CDCl3):
d ppm 13.8, 22.3, 23.7, 29.1, 29.4, 29.8,
30.0, 31.2, 31.5, 41.6, 48.3, 53.7, 53.9, 100.7, 104.9, 109.5, 113.2,
113.3, 125.7, 125.9, 127.1, 127.6, 127.9, 128.5, 128.6, 128.7, 128.9,
129.0, 129.3, 129.4, 129.7, 129.8, 132.0, 135.6, 135.7, 136.1, 136.2,
136.5, 137.0, 137.4, 137.7, 141.8, 142.2, 142.3, 146.4, 146.8, 147.6,
152.2, 153.7, 169.7. ESI-MS (m/z): 713.4 [M þ H]þ. Anal. calculated
for C50H56N4: C, 84.23; H, 7.92; N, 7.86. Found: C, 84.07; H, 8.01;
N, 7.73.
2.2.1.13. 2,7-Bis(4-fluorophenyl)-10,10-dioctyl-3,6-dihydrofluoreno
[2,3-d:6,7-d0]diimidazole (3m). White powder, yield 54%. Mp
178e179 ꢀC 1H NMR (500 MHz, DMSO-d6):
d ppm 0.52 (m, 4H), 0.69
(t, J ¼ 7.1 Hz, 6H), 0.93e1.01 (m, 20H), 2.01e2.02 (m, 4H), 7.39e7.44
(m, 5H), 7.61 (s, 1H), 7.90 (m, 1H), 8.10e8.14 (m, 1H), 8.23e8.24 (m,
4H), 12.83e12.93 (m, 2H). 13C NMR (125 MHz, DMSO-d6):
d ppm
13.9, 22.0, 23.7, 28.7, 28.8, 29.5, 31.2, 41.3, 53.5, 101.7, 105.2, 109.1,
112.7,116.0,116.2,127.2,128.6,134.9,136.2, 136.9,143.8,144.1,144.8,
145.4, 145.9, 146.4, 150.4, 162.0, 164.0. Anal. calculated for
C43H48F2N4: C, 78.39; H, 7.34; N, 8.50. Found: C, 78.16; H, 7.21; N,
8.32.
2.2.2.2. 3,6-Dibenzyl-10,10-dioctyl-2,7-diphenyl-6,10-dihydro-3H-
fluoreno[2,3-d:6,7-d0]diimidazole (4b). Light yellow powder, yield
16e24%. Mp 174e176 ꢀC 1H NMR (500 MHz, CDCl3):
d ppm 0.73 (m,
4H), 0.80 (t, J ¼ 7.2 Hz, 6H), 1.05e1.12 (m, 20H), 2.07e2.11 (m, 4H),
5.48 (s, 4H), 7.17e7.19 (d, J ¼ 7.4 Hz, 4H), 7.32 (m, 2H), 7.37 (m, 4H),
7.42e7.46 (m, 8H), 7.68 (d, J ¼ 6.9 Hz, 4H), 7.78 (s, 2H). 13C NMR
2.2.1.14. 2,7-Bis(2,6-difluorophenyl)-10,10-dioctyl-6,10-dihydro-3H-
fluoreno[2,3-d:6,7-d0]diimidazole (3n). Light yellow powder, yield
(125 MHz, DMSO-d6): d ppm 13.9, 22.4, 23.8, 29.2, 29.5, 30.0, 31.6,
41.7, 48.3, 53.9, 100.4, 113.7, 125.8, 127.6, 128.0, 128.6, 129.0, 129.5,
129.7, 129.8, 132.5, 135.8, 136.4, 137.3, 142.7, 147.2, 153.9. ESI-MS
36%. Mp 169e170 ꢀC 1H NMR (500 MHz, DMSO-d6):
d ppm 0.52 (s,

H.-F. Chen et al. / Dyes and Pigments 94 (2012) 583e591
587
(m/z): 804.5 [M þ H]þ. Anal. calculated for C57H62N4: C, 85.24; H,
purification after the work-up. By condensation of 2a with the
corresponding aldehydes in 1.4-dioxane at 100 ꢀC for about 10 h,
fifteen aromatic substituted 6,10-dihydrofluoreno[2,3-d:6,7-d0]dii-
midazole derivatives 3a-o were successfully obtained in total
20e75% yields by two steps (Fig. 1). During exploration of the final
hydrogenated step, when tin powder was used as the reducing
agent, an alternate intermediate 2b was obtained. By condensation
of 2b with benzaldehyde, a mixture of two alkylated compounds 4a
and 4b, as well as 3a was obtained. This may be caused by the
existed Sn4þ having not been completely removed after the work-
up procedure (Fig. 2). This assumption was confirmed by adding
Sn4þ into the condensation reaction of 2a with benzaldehyde and
three compounds were obtained with the ratio slightly different.
All target compounds were isolated and purified by column chro-
matography on silica gel with high purity and their molecular
structures were confirmed by 1H NMR spectroscopy, 13C NMR
spectroscopy, and element analysis, which were shown detailed in
experiment section.
7.78; N, 6.98. Found: C, 85.10; H, 7.55; N, 6.87.
2.3. Determination of crystal structure of 4b
Suitable single crystals of 4b for X-ray structural analysis were
obtained by slow evaporation of a solution of the solid in
dichloromethane and methanol at room temperature. The selected
crystal with approximate dimensions of 0.25 ꢁ 0.20 ꢁ 0.20 mm for
4b was mounted on a four-circle single crystal X-ray diffractometer
(CAD4 DIFFACTIS 586) using a graphite monochromated MoK
a
radiation (
l
¼ 0.071073 nm) and the data were collected at 296(2)
K. The structure was solved by direct methods and refined by full-
matrix least-squares method on Fo2bs by using the SHELXTL 97
software package. The non-hydrogen atoms were refined aniso-
tropically. The hydrogen atoms bound to carbon were located by
geometrical calculations, with their position and thermal parame-
ters being fixed during the structure refinement. The final refine-
ment converged at R1 ¼ 0.1352, wR2 ¼ 0.3435 for 4b. A summary of
the crystallographic data and structure refinement details is given
in Table 1. The crystal structure and cell structure of 4b are shown in
Fig. 3.
3.2. X-ray crystallography analysis
The spatial structure of compound 4b was determined by using
X-ray diffraction analysis. The ORTEP view of the structure of 4b
(Fig. 3a) showed the almost planar arrangement of the 6,10-
dihydrofluoreno[2,3-d:6,7-d0]diimidazole ring. The fluorene
moiety ii forms dihedral angle of 0.31ꢀ with adjacent imidazole ring
iii. In contrast, the adjacent phenyl ring iv takes a torsion angle of
41.24ꢀ with the 6,10-dihydrofluoreno[2,3-d:6,7-d0]diimidazole
moiety. In the crystal lattice (Fig. 3b), the molecules are stacked in
a head-to-tail manner and the alignment is mainly caused by weak
intermolecular Van der Waals force.
3. Result and discussion
3.1. Synthesis
The synthetic strategy employed involved the efficient prepa-
ration of the key intermediate 2,3,6,7-tetraamino-9,9-dioctylflu
orene (TADOF, 2a) from fluorene. A systematic synthetic route for
2,3,6,7-tetraamino-9,9-bisalkylfluorene was reported by Qian’s
group [40]. In our synthesis, we modified the final step and 3,6-
dinitro-9,9-dioctylfluorene-2,7-diamine (1) was hydrogenised
with Pd(OH)2 and hydrazine hydrate in EtOH under reflux to yield
TADOF (2a), which was used for next step without further
3.3. Spectral properties
The photophysical properties of the compounds were examined
by UVevis and photoluminescent (PL) spectra in dilute CH2Cl2 and
in the solid films, as shown in Figs. 4 and 5. The absorption peak
wavelengths (labs), fluorescence excitation wavelengths (lex), PL
Table 1
Crystal data and structure refinement for 4b.
peak wavelengths (lem), stokes shift (lemelex) in solution and the
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system, space group
Unit cell dimensions
a (Å)
C57 H62 N4
803.11
296(2) K
0.71073 Å
Triclinic, P-1
solid state, and fluorescence quantum yields (4FL) in solution are
collected in Table 2. The UVevis and PL spectra in the solid state
were carried out on films spin-coated onto quartz from chloroform
solution. The results showed that the absorption maxima of these
6,10-dihydrofluoreno[2,3-d:6,7-d0]diimidazole
derivatives
CH2Cl2 solution vary from 363 to 423 nm that are attributed to the
* transition depending on the substituents at the terminal
in
13.500(3)
14.957(3)
15.611(3)
66.689(3)
71.951(3)
82.431(3)
2752.3(10)
2
b (Å)
c (Å)
pep
position. As it can be observed in Fig. 4a, compound 3a bearing
phenyl group at the terminal exhibited the absorption maximum at
366 nm in CH2Cl2. With the change of the substituents at the
terminal position from the phenyl to other aryl group such as thi-
ophen-2-yl (3b), 5-methylfuran-2-yl (3c), pyridin-2-yl (3d), naph-
thalen-1-yl (3e) and (E)-styryl (3f), the UVevis absorption maxima
a
b
g
(ꢀ)
(ꢀ)
(ꢀ)
Volume (Å3)
Z
Density (calc.) (Mg/m3)
Absorption coefficient (mmꢂ1
F(000)
0.969
0.056
864
)
were all red-shifted. Compounds 3b and 3e exhibited strong pep*
Crystal size (mm)
0.25 ꢁ 0.20 ꢁ 0.20 mm
electron absorption bands, which peak at 382 and 372 nm,
respectively. The absorption spectra of compounds 3c and 3d were
very similar, showing two characteristic absorption peaks at ca. 376
and 388 nm. And the largest red-shift was observed at 396 nm for
compound 3f, which possesses the longest conjugation length,
relative to that of the other compounds. Moreover, it can be found
that compounds 4a-b with benzyl in N-1 positions have almost the
same absorption maxima as compound 3a, indicating that alkyl-
ation of imidazole has a limited effect on their electric energy
levels.
q
range for data collection (ꢀ)
1.97e25.05
Limiting indices
Reflections collected/unique
ꢂ16 ꢃ h ꢃ 8,ꢂ17 ꢃ k ꢃ 16,ꢂ18 ꢃ l ꢃ 18
14342/9557 [R(int) ¼ 0.0227]
98.0%
Completeness to theta ¼ 25.05
Absorption correction
None
Max. and min. transmission
Refinement method
0.9889 and 0.9861
Full-matrix least-squares on F2
9557/2/517
Data/restraints/parameters
Goodness-of-fit on F2
1.213
Final R indices [I > 2
s(I)]
R1 ¼ 0.1352, wR2 ¼ 0.3435
R1 ¼ 0.2054, wR2 ¼ 0.4030
1.038 and ꢂ0.324
CCDC 873787
R indices (all data)
Largest diff. Peak and hole (eÅꢂ3
CCDC deposit no.
)
Next, in order to study the substituent effect on the optical
properties, a series of compounds (3g-o) with various polar groups

588
H.-F. Chen et al. / Dyes and Pigments 94 (2012) 583e591
Fig. 3. The molecular structures of compound 4b, H atoms and the molecular structures of solvents are omitted for clarity. (a) ORTEP drawing. (b) A view of the molecule packing
structure.
(F, Cl, CH3, CF3, NO2, OMe) substituted on the phenyl ring were
studied. Among these polar groups, some are known as strong
peaks, one at 370 nm and the other at 385 nm. The UVevis
absorption maxima of 3l, 3m, 3n and 3o were red-shifted by 4, 0,
2, 7 nm respectively relative to that of 3a, and the enormous red-
shift of 57 nm as observed in 3i with a broad and featureless
absorption band. The effect of the substituent on the absorption
properties is not clearly seen. This suggests that the electronic
properties of the substituents might not play an important role in
the UVevis absorption spectra.
According to the electronic absorption spectra of 3a-f, 4a-b in
thin films, as shown in Fig. 4b, all compounds showed red-shifted
absorption maxima by 5e30 nm by comparison with the dilute
CH2Cl2 solutions and the enormous red-shift of 30 nm as observed
p-
acceptors (i.e., NO2), others are known as intermediate (i.e. F, Cl),
besides being classified as electron-withdrawing (i.e., F, Cl, CF3,
NO2) or electron-donating groups (i.e., CH3, OMe). Compared with
the maximum absorption peak of compound 3a (366 nm),
compounds 3g (371 nm) and 3h (373 nm) with electron-donating
methyl and methoxyl groups, respectively, had slight shifts
toward higher wavelengths. Compound 3j with electron-
withdrawing CF3 group exhibited the absorption maximum at
378 nm. Moreover, compound 3k with fluorine group in ortho-
position of the terminal benzene ring showed two absorption

H.-F. Chen et al. / Dyes and Pigments 94 (2012) 583e591
589
Fig. 4. Normalized absorption spectra of 3a-o, 4a-b (1 ꢁ 10ꢂ5 M) recorded in CH2Cl2 solutions (a) and thin neat films (b) at room temperature.
in 3f with a broad and featureless absorption band at ca. 426 nm.
Regarding the absorption spectra of 3g-o in films, the trends
observed with different substituents in terms of the spectral shapes
and peak positions were nearly the same compared to the spectra
obtained in dilute solutions. And the UVevis absorption maxima of
compounds 3a, 3g-h, 3j and 3o were almost the same at ca. 375 nm.
The UVevis absorption maxima of 3n, 3m, 3l and 3i were red-
shifted by 2, 4, 10 and 20 nm respectively relative to those in
dilute CH2Cl2 solution and compound 3k showed a slightly blue
shift.
Fig. 5 shows the photoluminescence (PL) spectra recorded upon
excitation at each excitation wavelength (lex) at room temperature.
In CH2Cl2 solution, the fluorescence spectra of 3a showed two
peaks at 395 and 416 nm (Fig. 5a) and the fluorescence quantum
yield is 0.78, which is higher than that of quinine sulfate
3k-l, and 3n were very similar to those of 3a with two peaks at ca.
395 and 416 nm. Compared to 3a, compound 3o (lem ¼ 401,
420 nm) with para-Cl substituted phenyl group at the terminal red-
shifted ca. 5 nm, whereas compound 3m (lem ¼ 387, 409 nm) with
para-F blue-shifted by 7 nm. Compound 3j fluoresced in dichloro-
methane with emission peaks at 431 nm, probably due to the
increased charge-transfer character induced by the fluoroalkyl
group. Compound 3i exhibited quite weak fluorescence in solution
and in thin films owing to the existence of nitro-substituent, which
would decrease the radiative rate and increase the internal
conversion rate of an excited state fluorophore [41]. Except
compound 3i, all the other compounds synthesized were moderate
to high fluorescent in CH2Cl2 solution with fluorescence quantum
yields 4FL in the range of 0.30e0.89.
By comparison with the dilute CH2Cl2 solutions, the emission
spectra of all compounds in solid states showed red-shifts to longer
wavelengths by 20e74 nm (Fig. 5b). The red-shifts of the emission
observed in the solid state were probably due to the rigid 6,10-
dihydrofluoreno[2,3-d:6,7-d0]diimidazole group and its strong
intermolecular forces, which drove the molecules to pack at high
(4 ¼ 0.55). The fluorescence spectra of compounds 3c and 4b
FL
were almost the same as those of 3a, showing two peaks at 396 and
417 nm, whereas compound 4a (lem ¼ 392, 412 nm) showed
slightly blue-shifted PL spectra by 3 nm. The fluorescence spectra of
compound 3b with two peaks at 409 and 426 nm were red-shifted
by 10 nm relative to those of 3a. It’s interesting to note that the
fluorescence maxima of 3d, 3e and 3f, relative to those of 3a, were
red-shifted by 12, 26 and 38 nm, respectively, and compound 3f
fluoresced in dichloromethane with emission peaks at ca. 454 nm,
probably due to the elongation of the conjugation length.
density, restricted the molecular rotation and increased the
conjugation significantly, in turn resulting in the red-shifts. Con-
cerning the larger stokes shift ( emelex) of compounds 3a-h, 3j-o
p-
l
and 4a-b in the film state as compared with those in the solution
phase, it can be explained in the same way. In the solid state, the
fluorescence maxima of 3a were red-shifted by ca. 39 nm relative to
those in CH2Cl2 solution, showing one peak at 455 nm. Derivatives
The PL spectra of compounds 3a, 3g-h and 3k-o in CH2Cl2 were
very similar in shape. The fluorescence spectra of compounds 3g-h,

590
H.-F. Chen et al. / Dyes and Pigments 94 (2012) 583e591
Fig. 5. Normalized fluorescence spectra of 3a-o, 4a-b (1 ꢁ 10ꢂ6 M) recorded in CH2Cl2 solutions (a) and thin neat films (b) excited at each lex at room temperature.
3c and 3f showed blue-green emission, with PL emission maxima
at 491 and 498 nm, respectively. Besides compounds 3h, 4a and 4b
It is worth mentioning that both the absorption and emission
maxima of 3a, 3g, 3j, and 3m-o in solution and in the solid state are
red-shifted from those of their fluoreno[2,3-d]imidazole counter-
parts (e.g., the labs in CH2Cl2, lem in CH2Cl2 and in the solid state of
compound 3a, relative to those of compound DOFIPh [39], were
(
lmax ¼ 450, 432 and 441 nm, respectively), all other compounds
3b, 3d-e, 3g and 3j-o showed blue PL with lmax between 462 and
470 nm in their solid states.
Table 2
Optical properties of the compounds 3a-o, 4a-b.
labs(nm)a
lex(nm)b
lem(nm)c
Stokes shifts (nm)d
CH2Cl2
4FL
e
Compound
CH2Cl2
film
CH2Cl2
film
CH2Cl2
film
film
3a
3b
3c
3d
3e
3f
3g
3h
3i
3j
3k
3l
3m
3n
3o
4a
4b
366
382
377, 387
375, 390
372
375
403
398
366
383
377
376
374
396
372
371
e
375
405
400
387
387
426
376
378
e
395, 416
409, 426
396, 417
428
442
454
393, 413
393, 415
ef
455
468
491
465
464
498
464
450
ef
29
26
19
52
68
58
21
22
e
80
63
91
78
77
72
88
72
e
0.78
0.42
0.64
0.61
0.61
0.33
0.85
0.8
386, 402
387
426
376
375
443
377
383
380
370
370
374
373
368
396
371
373
423
0.01
0.3
378
380
372
373
377
374
373
365
366
383
383
383
378
378
382
381
376
431
470
464
462
468
467
464
432
441
51
23
25
10
23
28
27
30
87
81
79
90
89
82
51
65
370, 385
370
395, 416
398, 417
387, 409
397, 416
401, 420
392, 412
396, 417
0.81
0.79
0.82
0.63
0.89
0.72
0.67
366
368
373
364
363
a
UVevis absorption wavelengths in dichloromethane or in thin neat films at room temperature.
Excitation wavelengths in dichloromethane or in thin neat films at room temperature.
Fluorescence wavelengths in dichloromethane or in thin neat films at room temperature.
b
c
d
e
f
Stokes shift (lemelex) in dichloromethane or in thin neat films at room temperature.
Fluorescence quantum yields, measured in CH2Cl2 solution using a 0.2 M H2SO4 solution of quinine sulfate (4FL ¼ 0.55) as a reference.
Too weak to be measured.

H.-F. Chen et al. / Dyes and Pigments 94 (2012) 583e591
591
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In summary, 2,3,6,7-tetraamino-9,9-dioctylfluorene (TADOF), as
a new multifunctional intermediate for -conjugated molecules,
was efficiently synthesized. And novel 10,10-dioctyl-3,6-
dihydrofluoreno[2,3-d:6,7-d0]diimidazole
(DOFDI)-type fluo-
p
rophores with various aryl substituents were designed and
conveniently synthesized, and their absorption and fluorescence
properties were investigated in solution and in the solid state. The
DOFDIs were synthesized by condensation of the key intermediate
TADOF with aldehydes under very mild conditions, which make it
possible to incorporate a diverse range of substituents in the DOFDI
core and provided an efficient approach to the preparation of some
useful dyes and pigments. It can be concluded that the absorption
spectra and fluorescence characteristics of the new target
compounds show dependence on their molecular structure. These
compounds possess a medium strong blue fluorescence-emitting
ability with 4FL values in the region of 0.30e0.89. Further
research regarding the incorporation of these systems usable both
as organic light-emitting diodes and as fluorescent probes is under
way in our laboratory.
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The authors are grateful for support from the National Natural
Science Foundation of China (Project No. 30672506), Shanghai
Pujiang Program (No. 10PJ1403700), and Leading Academic Disci-
pline Project of Shanghai Municipal Education Commission (Project
No. J50102). H.-F.C. thanks the support of the 5th Innovation
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