One-pot synthesis of 2-bromo-4,5-diazafluoren-9-one via a tandem oxidation-bromination-rearrangement of phenanthroline and its hammer-shaped donor-acceptor organic semiconductors

Article abstract of DOI:10.1016/j.tet.2010.12.065

An unexpected one-pot tandem procedure of 2-bromo-4,5-diazafluoren-9-one starting from phenanthroline with a yield of up to 50% has been described. The conversion mechanism involves three consecutive oxidation, bromination, and rearrangement reactions. A series of its hammer-shaped donor-acceptor organic semiconductors with solvent-dependent fluorescence have also been constructed via Ullman and/or Friedel-Crafts reaction. Diazafluorenes (DAFs) and derivatives are regarded as promising building blocks or candidates for donor-acceptor organic semiconductors.

Full text of DOI:10.1016/j.tet.2010.12.065

Tetrahedron 67 (2011) 1977e1982
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
One-pot synthesis of 2-bromo-4,5-diazafluoren-9-one via a tandem
oxidationebromination-rearrangement of phenanthroline and its
hammer-shaped donoreacceptor organic semiconductors
*
Jian-Feng Zhao, Lin Chen, Peng-Ju Sun, Xiao-Ya Hou, Xiang-Hua Zhao, Wei-Jie Li, Ling-Hai Xie ,
*
Yan Qian, Nai-En Shi, Wen-Yong Lai, Qu-Li Fan, Wei Huang
Key Laboratory for Organic Electronics and Information Displays (KLOEID), Institute of Advanced Materials (IAM), Nanjing University of Posts and Telecommunications,
Nanjing 210046, China
a r t i c l e i n f o
a b s t r a c t
Article history:
An unexpected one-pot tandem procedure of 2-bromo-4,5-diazafluoren-9-one starting from phenan-
throline with a yield of up to 50% has been described. The conversion mechanism involves three
consecutive oxidation, bromination, and rearrangement reactions. A series of its hammer-shaped
donoreacceptor organic semiconductors with solvent-dependent fluorescence have also been con-
structed via Ullman and/or FriedeleCrafts reaction. Diazafluorenes (DAFs) and derivatives are regarded as
promising building blocks or candidates for donoreacceptor organic semiconductors.
Ó 2011 Published by Elsevier Ltd.
Received 22 September 2010
Received in revised form 17 December 2010
Accepted 24 December 2010
Available online 8 January 2011
Keywords:
One-pot synthesis
2-Bromo-4,5-diazafluoren-9-one
Tandem oxidationebromination-
rearrangement
Donoreacceptor
Organic semiconductor
1. Introduction
Recently, DeA conjugated polymers were extensively applied to
develop low-bandgap organic semiconductors with broad elec-
Donoreacceptor (DeA) molecules have attracted much atten-
tion in organic molecular and solid electronics after the discovery of
frontier molecular orbital (FMO) theory and subsequently appli-
tronic absorption and high charge mobilities for solar cells.7
However, most of
p-molecular segments exhibit electron-do-
nating property in organic semiconductors,8 it is significant to ex-
plore novel electron-withdrawing building blocks to fulfill various
cations in the nonlinear optical materials.1 DeA
p-systems possess
rectifying characteristics with the essence of intramolecular pen
DeA p-systems for high-performance devices. Numerous efforts
junctions in molecular devices.2 Huang’s group proposed pen
have been made to focus on pyridine,9 oxadiazole,10 benzothiadia-
13
p-conjugated copolymers to flexibly adjust highest occupied mo-
zole,11 perylene diimide,12 and C60 as electron-acceptors. Never-
lecular orbital (HOMO) and lower unoccupied molecular orbital
(LUMO) levels for red, green, and blue (RGB) light-emitting poly-
mers in polymer light-emitting diodes (PLEDs).3 Their charge
transfer and energy transfer processes can be well tuned through
the combination of various molecular segments to develop the
high-efficient fluorescent red light-emitting materials4 and ambi-
polar charge-transporting materials.5 Furthermore, trap depth and
trap density can be controlled via pen components to develop
polymeric dynamic random access memory (DRAM) cells.6
theless, 4,5-diazafluorenes (DAFs) as popular chelate ligands14
whose electron-deficient property have been ignored to a large
extent.15 DAFs are potential building blocks in organic electronics.
9,90-Diaryl-DAFs exhibit excellent hole-blocking ability in compar-
ison with the widely used 2,9-dimethyl-4,7-diphehyl-1,10-phe-
nanthroline (BCP).16 Moreover, spiro-DAF incorporated into blue
terfluorene was demonstrated to enhance the ability of electron
injection without changing the emission characteristics by Wong
et al.17 Besides, DAF-based photoinduced electron transfer (PET)
chromophores were constructed to chelate with sense metal ions.18
In this context, one challenge is to develop the key intermediates,
such as halogen-substituted DAFs, which are significant to be in-
* Corresponding authors. Tel.: þ86 25 8586 6008; fax: þ86 25 8586 6999;
e-mail addresses: iamlhxie@njupt.edu.cn (L.-H. Xie), iamwhuang@njupt.edu.cn
(W. Huang).
troduced into the p-conjugated systems in organic electronics.
0040-4020/$ e see front matter Ó 2011 Published by Elsevier Ltd.
doi:10.1016/j.tet.2010.12.065

1978
J.-F. Zhao et al. / Tetrahedron 67 (2011) 1977e1982
2. Results and discussion
boiled sodium hydroxide solution undergoing a rearrangement
reaction.22 On the basis of these experiments above, we proposed
a mechanism of one-pot three steps named as oxidationebromi-
nation-rearrangement (OBR) procedure (Scheme 1) to this tandem
reaction. In addition, we realized this useful alternative protocol for
the facile synthesis of 5 successfully (Scheme 1),23 which was
obtained either by the troublesome bromination of 2,20-bipyridine
hydrobromide salt or Stille cross-coupling reaction in the
literatures.24
It is known that halogenations of aromatic compounds have
always been considered as key starting materials to actualize the
connection of different
p-molecular segments to construct semi-
conducting DeA molecules by various CeC, CeO or CeN cross-
coupling reactions. The synthesis of diazafluorenone (1, Scheme 1)
has been carried out under the condition of KMnO4/KOH (0.24 M)
and NaOH (0.1 M).19 However, there are rarely reports on its halo-
gen-substituted derivatives,20 such as bromide substituted diaza-
fluorenone 2, in the last three decades. In this contribution, 2 was
firstly synthesized and demonstrated by an unexpected one-pot
tandem reaction in a yield of up to 50%, as shown in Scheme 1. We
initially planned to prepare 3 from 6 in the condition of H2SO4/
HNO3/KBr for 2 h according to the literatures.21 In fact, reaction
time was occasionally prolonged to 24 h. As a result, after neu-
tralizing the mixture with solid sodium hydroxide, two different
compounds were monitored by thin-layer chromatography (TLC)
after the rapid neutralization of the reactant with solid sodium
hydroxide. GCeMS showed their molecular ion peaks of 182 and
260 g/mol, respectively, corresponding to diazafluorenone 1 and 2-
bromo diazafluorenone 2, respectively. Fortunately, the target
compound 2 was unambiguously identified by single-crystal X-ray
diffraction (Fig. 1).
Subsequently, a series of DeA type derivatives, among which
DAF acting as acceptor and carbazole (Cz) as donor, were designed
and constructed (Scheme 2). Compound 7 was obtained via CeN
cross-coupling Ullman reaction in 71% yield. Then, dicyanovinyl
group was introduced in the presence of malononitrile in dime-
thylsulfoxide (DMSO) giving 8 with the yield of 66% in order to
further enhance the electron-withdrawing ability. The BF3$Et2O
catalyzed FriedeleCrafts (FeC) reaction25 was carried out to gen-
erate CDAFs, monosubstituted 9 in 30% yield and disubstituted 10
in 68% yield. Similarly, dicyanovinyl group was also introduced
giving 11, 12, and 13 in the yields of 70%, 63%, and 65%, respectively.
It should be noted that 13 could not be effectively obtained by
electrophilic FeC reaction starting from 11. All the compounds were
confirmed by 1H NMR, 13C NMR, GCeMS, MALDI-TOF MS, and
elemental analysis.
O
NC
N
CN
NC
N
CN
N
a, d
Br
g
50%
N
2
N
N
N
Br
N
6
55%
N
O
11
8
c, f
O
90%
O
98%
O
f
c
a
a
N
N
O
1
f
O
O
b, e
96%
Br
b
N
Br
70%
N
N
N
N
N
N
7
N
N
3
4
2
c
a, d
45%
Br
N
N
N
N
5
O
O
Scheme 1. Synthesis of 1,19a,22 2, and 5, and related intermediates. Conditions: (a)
H2SO4/HNO3/KBr, reflux, 24 h; (b) H2SO4/HNO3/KBr, reflux, 12 h; (c) H2SO4/HNO3/KBr,
reflux, 2 h; (d) NaOH (s); (e) NaOH (aq); (f) NaOH (0.1 M); (g) KMnO4; KOH (0.24 M).
N
N
N
N
N
N
10
9
a
a
NC
N
CN
N
NC
N
CN
N
N
N
Fig. 1. X-ray crystal structure of 2 with ORTEP drawing and its molecular packing.
In order to profoundly understand the conversion mechanism,
a series of experiments were designed and carried out with dif-
ferent reaction time. Compound 3 was obtained in 90% yield for 2 h,
which is consistent with the literature.21c Then 4 was obtained in
70% yield after treating 3 in the same condition for 12 h. At last, 2
was smoothly synthesized with a yield of 98% after treating 4 in
12
13
Scheme 2. Synthesis of diazafluorenone-based DeA type derivatives. Conditions:
(a) CH2(CN)2, DMSO, 5 h, 110 ꢀC; (b) Carbazole, 1,2-dichlorobenzene, CuI, 18-crown-6,
K2CO3, 24 h, 190 ꢀC; (c) 9-phenyl-fluoren-9-ol, BF3$Et2O, CH2Cl2, rt, 24 h.

J.-F. Zhao et al. / Tetrahedron 67 (2011) 1977e1982
1979
Fig. 2 displays electronic absorption UVevis spectra of four DAF-
a
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
based DeA type derivatives including 7, 8, 10, and 13 in spin-coated
films and THF solvent (10ꢁ5 mol/L) (inset). There are several dis-
tinct bands in all four compounds in both dilute THF solution and
thin film. Among them, the high-energy absorption bands in the
Toluene
Benzene
THF
CHCl
3
range of 200e300 nm is assigned to
pep transition of p-conju-
*
DMSO
gated backbone on account of the large absorption coefficients.26
The lower-energy absorption band appearing in the range of
320e410 nm results from the intramolecular charge-transfer (ICT)
transition. The lowest-energy absorption band of 10 appearing in
the range of 420e510 nm with very small absorption coefficients is
300
400
500
attributed to the symmetry-forbidden ne
bonyl groups in diazafluorenone.
p
*
transition of the car-
Wavelength (nm)
b
0.4
500
400
300
200
100
0
7
1.6
8
1.4
7
1.2
8
0.3
0.2
0.1
0.0
10
13
Toluene
Benzene
THF
10
13
1.0
0.8
0.6
0.4
0.2
0.0
CHCl
3
0.0
500
DMSO
200
300
400
Wavelength (nm)
400
500
600
700
Wavelength (nm)
Fig. 3. The UVevis (a) and PL spectra (b) of 10 in different solvents (10ꢁ5 mol/L), insert:
the photograph (insert) of 10 in toluene, benzene, THF, and CHCl3 under the irradiation
of UV 365 nm.
200
300
400
500
600
Wavelength (nm)
It indicated that bulky 9-phenyl-fluoren-9-yl moieties (PFMs) of
10 also play a key role in tuning the energy transfer process and
electronic behaviors (in Fig. S10).
Fig. 2. The UVevis spectra of 7 (black), 8 (red), 10 (green), and 13 (blue) in spin-coated
films (a) and THF solvent (10ꢁ5 mol/L) (insert).
The reductive and oxidative cyclic voltammograms (CV) were
shown in Fig. 4 and Table 1. HOMO energy levels are estimated to be
The electronic absorption and photoluminescence spectra of 10
in several different polar solvents, including toluene, benzene,
tetrahydrofuran (THF), chloroform (CHCl3), and DMSO, are shown in
Fig. 3. The lower-energy bands in the range of 350e410 nm depend
slightly on solvent polarity, as shown in Fig. 3a, revealing that weak
electronic coupling existed between the donor (carbazole) and ac-
ceptor (diazafluorenone) moieties in the ground state. In contrast, it
exhibits solvent-dependent fluorescence, indicating that the com-
plicated excited states and energy transfer occur. There are two
emission bands with the peaks of ca. 420 and 560 nm under the
excitation of 360 nm in nonpolar toluene (420 and 561 nm) and
benzene (431 and 566 nm) solvents (Fig. 3b), in which the intensity
of yellow emission peak is relatively higher than that of blue emis-
sion. Blue and yellow emissions probablyoriginated from ICTand the
lowest excited state (ne
p state) via uncompleted energy transfer
*
process, respectively. The emissionwavelength of 10 altered with the
different excitation wavelengths, also indicating that energy transfer
from ICT to ne
p state is not completed. It is very interesting that two
*
emission peaks at 433 and 572 nm remain in polar THF, while the
yellow peak strength (572 nm) is weaker than that of blue peak
(433 nm). This result further indicates that blue and yellow emis-
sions probably originated from ICTexcited state and diazafluorenone
chromophores via uncompleted energy transfer process owing to
the latter easily quenched by stronger polar solvent than the former.
Furthermore, the long-wavelength emission disappeared in CHCl3
(434 nm) and DMSO (451 nm). This result probably indicated that
the stronger quenching effect of these polar solvents occur on the
lowest excited state of ne
*
p state feature of diazafluorenone. The
photograph shows the emission of 10 in different polar solvents
under the irradiation of UV 365 nm (Fig. 3b, insert) matching well
with the PL in different solvents. The similar solvent-dependent
effect and incomplete energy transfer in the emission spectra of 7
were also found in the abovementioned solvents, but not clearly.
Fig. 4. Reductive and oxidative cyclic voltammograms of 7 (a, blue), 8 (a, red), 10
(b, blue), and 13 (b, red); 0.1 M n-Bu4NPF6 in THF (reduction) and 0.1 M n-Bu4NPF6 in
CH2Cl2 (oxidation) were used as supporting electrolytes. A platinum shþeet electrode
was used as the working electrode; scanning rate was 100 mV/s, where E(Fc/Fc) is about
0.066 V for 7, 8, and 13, and 0.14 V for 10, respectively.

1980
J.-F. Zhao et al. / Tetrahedron 67 (2011) 1977e1982
Table 1
Physical properties of target molecules
Compound
labs, max/nm
lPL, max/nm
Cyclic voltammetry
Solution
Film
Solution
Eox/(V)
Ered/(V)
HOMO (eV)
LUMO (eV)
Eg (eV)
7
8
10
13
235, 350
231, 339
244, 353
237, 346
235, 359
230, 372
234, 376
235, 361
402, 551
419
425, 563
420, 560
1.12
1.10
1.07
1.06
ꢁ1.25
ꢁ0.66
ꢁ1.07
ꢁ0.68
ꢁ5.85
ꢁ5.83
ꢁ5.73
ꢁ5.79
ꢁ3.48
ꢁ4.07
ꢁ3.59
ꢁ4.05
2.37
1.76
2.14
1.74
ꢁ5.85 eV for 7, ꢁ5.83 eV for 8, ꢁ5.73 eV for 10, and ꢁ5.79 eV for 13
according to their turn-on voltages of oxidation processes,
respectively, which probably is attributed to their electron-donat-
ing Cz groups.27 Compared with 7 and 8, the second peaks of 10 and
13 result from the fluorene groups. LUMO energy levels are esti-
mated to be ꢁ3.48 eV for 7, ꢁ4.07 eV for 8, ꢁ3.59 eV for 10, and
ꢁ4.05 eV for 13 according to their turn-on voltages of reduction
processes, respectively. Compared with 7 and 10, the introduction
of strongly electron-withdrawing dicyanovinyl groups in 8 and 13
greatly decreased their LUMO energy levels. It is worthy noting that
13 has the lowest HOMO/LUMO bandgap energy of 1.74 eV.
about 0.066 V for 7, 8, and 13, and 0.14 V for 10, respectively. X-ray
crystallographic data for 2 were collected on a P4 Bruker diffractom-
eterequippedwith a Bruker SMART1 KCCD area detector (employing
the program SMART) and a rotating anode utilizing graphite-mono-
ꢀ
chromated Mo K
a
radiation (
l
¼0.71073 A). Data processing was
carried out using the program SAINT, while the program SADABS
was utilized for the scaling of diffraction data, the application of
a decay correction, and an empirical absorption correction based on
redundant reflections. The structures were solved by using the direct-
method procedure in the Bruker SHELXL program library and refined
by full-matrix least-squares methods on F2. All nonhydrogen atoms
were refined using anisotropic thermal parameters and hydrogen
atoms were added as fixed contributors at calculated positions, with
isotropic thermalparameters based on the carbon atom towhich they
are bonded.
3. Conclusions
In summary, we have developed an effective protocol to syn-
thesize 2-bromo-4,5-diazafluoren-9-one (2) and demonstrated the
tandem oxidationebromination-rearrangement mechanism. The
one-pot synthesis method reveals that KBr is an efficient bromi-
nation reagent for electron-deficient diaza-aromatic hydrocarbons.
A series of diazafluorenes-based derivatives also have been syn-
thesized via Ullman and/or FriedeleCrafts reaction, which exhibit
solvent-dependent fluorescence and low-energy bandgap. Diaza-
fluorenes-based donoreacceptor systems are promising organic
semiconductors and ligands in organic electronics and supramo-
lecular chemistry.
4.1.1. 2-Bromo-4,5-diazafluoren-9-one (2). Mixture of 1,10-phe-
nanthroline hydrate (2.93 g, 14.8 mmol), KBr (2.11 g, 17.8 mmol),
and a mixed acid (18 ml of concentrated HNO3 and 36 ml of con-
centrated H2SO4) was allowed to react for 24 h under reflux after
the temperature ascending to 100 ꢀC rapidly. The reaction mixture
was poured into water (300 ml) and neutralized with solid sodium
hydroxide until pH¼7. The precipitate was filtered and washed
with CHCl3, then extracted with CHCl3. The filtrate was dried over
anhydrous MgSO4. Then the solvent was removed by rotary evap-
oration, and the residue was purified by column chromatography
(silica gel, EtOAc/petroleum ether, 1:2) to give 2 (1.93 g, 50%) as
a straw yellow solid; mp 188e189 ꢀC; Rf 0.35 (silica gel, EtOAc/pe-
troleum ether, 1:3); [found: C, 50.62; H, 1.92. C11H5BrN2O requires
4. Experimental section
4.1. General information
C, 50.61; H, 1.93%]; 1H NMR (400 MHz, CDCl3)
d 8.89 (s, 1H),
All the chemicals and reagents were purchased from Nanjing
Fountain Global Displays.1H and 13C NMR were recorded on a Bruker
400 MHz spectrometer in CDCl3 or DMSO-d6 with tetramethylsilane
(TMS) as the interval standard. Mass spectra were recorded on a Shi-
madzu GCMS 2010 PLUS. For the MALDI-TOF MS spectrum, it was
recorded in reflectivemode. Elementalanalyseswerecarriedoutinan
elementar Analysensysteme GmbH-vario EL III element analyzer.
Absorption spectra were measured with a Shimadzu UV-3600 spec-
trometer at 25 ꢀC, and emission spectra were recorded on a Shimadzu
RF-5301(PC)S luminescence spectrometer. Differential scanning cal-
orimetry (DSC) analyses were performed on a Shimadzu DSC-60A
instrument. Thermogravimetric analyses (TGA) were conducted on
a Shimadzu DTG-60H thermogravimetric analyzer under a heating
rate of 10 ꢀC/min and a nitrogen flow rate of 50 ml/min. CV studies
were conducted using an CHI660C Electrochemical Workstation in
atypicalthree-electrodecellwithaplatinumsheetworkingelectrode,
a platinum wire counter electrode, and a silver/silver nitrate (Ag/Agþ)
reference electrode. All electrochemical experiments were carried
out under a nitrogen atmosphere at room temperature in an elec-
trolyte solution of 0.1 M tetrabutylammonium hexafluorophosphate
(n-Bu4NPF6) in dichloromethane (oxidation process) and tetrahy-
drofuran (reduction process) at a sweeping rate of 100 mV/s.
According to the redox onset potentials of the CV measurements,
the HOMO/LUMO energy levels of the materials are estimated
based on the reference energy levelþof ferrocene (4.8 eV below the
vacuum): HOMO/LUMO¼ꢁ[EonsetꢁE(Fc/Fc)þ4.8] eV, where Eþ(Fc/Fc) is
8.84e8.83 (d, J¼5.2 Hz,1H), 8.13 (s, 1H), 8.04e8.02 (d, J¼7.6 Hz,1H),
7.42e7.39 (t, J¼12.4 Hz, 1H); 13C NMR (100 MHz, CDCl3)
d 188.1,
162.7, 161.4, 156.0, 155.5, 134.2, 131.8, 130.4, 129.2, 125.0, 122.3.
GCeMS (EI-m/z) calcd for C11H5BrN2Oþ [M]þ 261.07, found 261.15.
4.1.2. 3-Bromo-1,10-phenanthroline-5,6-dione (4). Mixture of Phe-
nanthroline-5,6-dione (0.50 g, 2.38 mmol), KBr (0.34 g, 2.87 mmol),
and a mixed acid (2.9 ml of concentrated HNO3 and 5.6 ml of con-
centrated H2SO4) was allowed to react for 12 h under reflux after the
temperature ascending to 100 ꢀC rapidly. The reaction mixture was
poured into water (300 ml) and neutralized with sodium hydroxide
solution until pH¼7. The precipitate was filtered and washed with
CHCl3, then extracted with CHCl3. The filtrate was dried over anhy-
drous MgSO4, thesolvent wasremoved by rotaryevaporation, and the
residue was purified by column chromatography (silica gel, EtOAc/
petroleum ether, 2:1) to afford the desired product 4 (0.48 g, 70%) as
a greenblack solid; mp 268 ꢀC; Rf 0.25 (silica gel, EtOAc/petroleum
ether, 2:1); [found: C, 49.90; H,1.76. C12H5BrN2O2 requires C, 49.86; H,
1.74%]; 1H NMR (400 MHz, CDCl3)
d 9.15e9.12 (s, 1H), 9.12e9.11 (d,
J¼4.8 Hz, 1H), 8.61 (s, 1H), 8.52e8.50 (d, J¼7.6 Hz, 1H), 7.63e7.60 (t,
J¼12.8 Hz, 1H); 13C NMR (100 MHz, CDCl3)
d 177.98, 177.78, 157.46,
156.52, 152.35, 151.00, 139.34, 137.55, 128.56, 127.99, 125.87, 123.34.
GCeMS (EI-m/z) calcd for C12H5BrN2Oþ2 [M]þ 289.08, found 289.95.
4.1.3. Preparation of 5-bromo-2,20-bipyridine (5). The procedure is
similar to the preparation of 2. Mixture of 2,20-bipyridine (0.5 g,

J.-F. Zhao et al. / Tetrahedron 67 (2011) 1977e1982
1981
3.2 mmol), KBr (0.46 g, 3.87 mmol), and a mixed acid (3.9 ml of
concentrated HNO3 and 7.7 ml of concentrated H2SO4) was allowed
to react for 24 h under reflux after the temperature ascending to
100 ꢀC rapidly. The reaction mixture was poured into 50 ml water
and neutralized with solid sodium hydroxide until pH¼7. The
precipitate was filtered and washed with CHCl3, then extracted
with CHCl3. The filtrate was dried over anhydrous MgSO4, the sol-
vent was removed by rotary evaporation, and the residue was pu-
rified by column chromatography (EtOAc/petroleum ether, 1:5) to
give desired product 5 (0.34 g, 45%) as a white solid; mp 74e75 ꢀC;
Rf 0.40 (silica gel, EtOAc/petroleum ether, 1:3); [found: C, 51.11; H,
2.94. C10H7BrN2 requires C, 51.09; H, 3.00%]; 1H NMR (400 MHz,
residue was purified by column chromatography (dichloro-
methane/petroleum ether, 4:1) to give 9 (0.076 g, 30%) as a yellow
solid; Rf 0.32 (silica gel, dichloromethane/petroleum ether, 5:1);
[found: C, 85.82; H, 4.27. C42H25N3O requires C, 85.84; H, 4.29%]; 1H
NMR (400 MHz, CDCl3)
d
9.03 (s, 1H), 8.86e8.85 (d, J¼3.6 Hz, 1H),
8.18 (s,1H), 8.07e8.05 (d, J¼7.6 Hz,1H), 7.98e7.93 (t, J¼19.2 Hz, 2H),
7.82e7.80 (d, J¼7.6 Hz, 2H), 7.50e7.48 (d, J¼7.6 Hz, 2H), 7.46e7.37
(m, 8H), 7.33 (t, 1H), 7.32e7.28 (m, 5H), 7.22 (s, 1H); 13C NMR
(100 MHz, CDCl3)
d 188.63, 162.92, 161.00, 155.59, 153.06, 151.55,
146.33, 140.35, 140.13, 139.17, 138.94, 136.10, 131.85, 130.43, 129.87,
129.08, 128.32, 128.18, 127.84, 127.55, 127.29, 126.73, 126.56, 126.25,
124.83, 124.05, 123.92, 121.11, 120.82, 120.28, 119.84, 109.26, 109.15,
65.53; MALDI-TOF MS (m/z) calcd for C42H25N3Oþ [M]þ 587.67,
found 588.42. And 10 (0.24 g, 68%) as a yellow solid; Rf 0.30 (silica
gel, dichloromethane/petroleum ether, 5:1); [found: C, 88.53; H,
4.47. C61H37N3O requires C, 88.49; H, 4.50%]; 1H NMR (400 MHz,
CDCl3, ppm)
d
8.74e8.743 (d, J¼2 Hz,1H), 8.70e8.69 (d, J¼4 Hz,1H),
8.40e8.38 (d, J¼8 Hz, 1H), 8.35e8.33 (d, J¼8 Hz, 1H), 7.97e7.95 (d,
J¼8 Hz 1H), 7.86e7.82 (t, J¼8 Hz, 1H), 7.36e7.33 (t, J¼8 Hz, 1H); 13C
NMR (100 MHz, CDCl3, ppm) d 155.13, 154.59, 150.17, 149.23, 139.47,
137.00, 123.99, 122.33, 121.14. GCeMS (m/z) calcd for C10H7BrN2þ
[M]þ, found 233.95. The compound is known and that the data
obtained matches that of the literature values.24b
CDCl3)
d
8.99 (s, 1H), 8.87e8.85 (d, J¼6.4 Hz, 1H), 8.13 (s, 1H),
8.06e8.04 (d, J¼6 Hz, 1H), 7.83 (s, 2H), 7.81e7.79 (d, J¼7.6 Hz, 4H),
7.47e7.45 (d, J¼7.6 Hz, 4H), 7.42e7.36 (m, 6H), 7.30e7.25 (m, 16H),
7.24 (s, 1H); 13C NMR (100 MHz, CDCl3)
d 188.54, 163.09, 155.55,
4.1.4. 2-(Carbazol-9-yl)-4,5-diazafluorenone (7). The samples of 2
(0.50 g, 1.1952 mmol), carbazole (0.74 g, 4.4293 mmol), potassium
carbonate (0.32 g, 2.3153 mmol) a spot of 18-crown-6, and copper
(I) iodide were dissolved in 1,2-dichlorobenzene, the mixture was
refluxed for 24 h under the protection of N2. Then remove the
solvent by reduced pressure distillation, the remains were extrac-
ted with CH2Cl2. The combined extracts were dried over anhydrous
MgSO4, the solvent was removed by rotary evaporation, and the
residue was purified by column chromatography (EtOAc/petroleum
ether, 2:1) as eluent to obtain 0.47 g orange-red powder in the yield
of (0.47 g, 71%); mp 172e173 ꢀC; Rf 0.35 (silica gel, EtOAc/petroleum
ether, 1:3); [found: C, 79.49; H, 3.79. C23H13N3O requires C, 79.53;
152.89, 151.57, 146.39, 140.07, 139.28, 138.96, 136.05, 131.81, 130.39,
129.86, 128.92, 128.30, 128.08, 127.77, 127.50, 127.25, 126.70, 126.26,
124.78, 123.99, 120.23, 120.09, 109.04, 65.53; MALDI-TOF MS (m/z)
calcd for C61H37N3Oþ [M]þ 827.97, found 828.87.
4.1.7. 2-(2-Bromo-4,5-diazafluoren-9-ylidene) malononitrile (11). The
procedure is similar to the preparation of 7. A sample of 2 (0.10 g,
0.3830 mmol) and malononitrile (0.028 g, 0.4225 mmol) was dis-
solved in DMSO (1.4 ml), the mixture was stirred at 110 ꢀC for 5 h.
After reaction, the mixture was filtrated and washed with aceto-
nitrile to give a brownish black precipitation as 11 (0.083 g, 70%);
[found: C, 54.44; H, 1.58. C14H5BrN4 requires C, 54.40; H, 1.63; Br,
H, 3.77%]; 1H NMR (400 MHz, CDCl3)
d
9.10e9.09 (d, J¼2.0 Hz, 1H),
25.85; N, 18.12]; 1H NMR (400 MHz, CDCl3)
d 8.89 (s, 1H), 8.85e8.83
8.9e8.89 (d, J¼4.8 Hz, 1H), 8.26e8.25 (d, J¼2.0 Hz, 1H), 8.18e8.16
(d, J¼8.0 Hz, 2H), 8.1e8.08 (d, J¼7.2 Hz, 1H), 7.51e7.45 (m, 4H),
7.44e7.42 (t, J¼7.6 Hz, 1H), 7.40e7.36 (m, 2H); 13C NMR (100 MHz,
(d, J¼5.2 Hz,1H), 8.82 (s, 1H), 8.73e8.71 (d, J¼8.4 Hz,1H), 7.48e7.45
(t, J¼13.2 Hz, 1H); 13C NMR (100 MHz, CDCl3, ppm)
d 158.8, 157.7,
156.1, 155.5, 155.1, 135.9, 133.7, 130.3, 128.9, 124.8, 121.9, 111.9, 81.0.
CDCl3)
d
188.63, 162.91, 161.12, 155.6, 153.3, 140.1, 136.1, 131.8, 130.5,
GCeMS (EI-m/z) calcd for C14H5BrNþ4 [M]þ 309.12, found 307.95.
129.9, 129.3, 126.60, 124.8, 124.1, 121.2, 120.7, 109.3. GCeMS (m/z)
calcd for C23H13N3Oþ [M]þ 347.37, found 347.10.
4.1.8. 2-(2-(3-(9-Phenyl-9H-fluoren-9-yl)-9H-carbazol-9-yl)-9H-
4,5-diazafluoren-9-ylidene)malononitrile (12). The procedure is
similar to the preparation of 7 and 11. Compound 9 (0.1 g,
0.1702 mmol) and malononitrile (0.01240 g, 0.1877 mmol) were
dissolved in DMSO (0.62 ml), and then the mixture was stirred at
110 ꢀC for 5 h. After filtration, 12 (0.68 g, 63%) was obtained as
a brownish black precipitation; [found: C, 85.06; H, 3.91. C45H25N5
4.1.5. 2-(2-(Carbazol-9-yl)-4,5-diazafluoren-9-ylidene)malononitrile
(8). Mixture of 7 (0.2 g, 0.5758 mmol) and malononitrile (0.042 g,
0.6351 mmol) was dissolved in DMSO (5.0 ml). Then the mixture
was stirred at 110 ꢀC for 5 h. The carmine precipitation was then
filtered and washed with MeCN to give 8 (0.15 g, 66%); [found: C,
78.93; H, 3.34. C26H13N5 requires C, 78.97; H, 3.31%]; 1H NMR
requires C, 85.02; H, 3.96%]; 1H NMR (100 MHz, CDCl3, ppm)
d 9.02
(400 MHz, CDCl3)
d
9.11 (s, 1H), 8.98 (s, 1H), 8.90e8.89 (d, J¼4.4 Hz,
(s, 1H), 8.89 (s, 1H), 8.86e8.85 (d, J¼5.2 Hz, 1H), 8.75e8.73 (d,
J¼8 Hz, 1H), 7.99e7.95 (t, J¼15.2 Hz, 2H), 7.82e7.80 (d, J¼7.6 Hz,
2H), 7.50e7.48 (d, J¼7.6 Hz, 2H), 7.74e7.75 (t, J¼7.2 Hz, 1H),
7.44e7.33 (m, 8H), 7.32e7.30 (m, 5H), 7.24 (s, 1H); 13C NMR
1H), 8.79e8.77 (d, J¼8.4 Hz, 1H), 8.19e8.17 (d, J¼8 Hz, 2H),
7.53e7.49 (m, 4H), 7.48e7.47 (t, J¼4.8 Hz, 1H), 7.41e7.37 (m, 2H);
13C NMR (100 MHz, CDCl3)
d 159.1, 157.2, 155.8, 155.5, 153.3, 140.0,
135.8, 133.7, 131.1, 130.1, 129.5, 126.8, 124.6, 124.2,121.4, 120.8, 112.0,
109.2, 81.0. GCeMS (EI-m/z) calcd for C26H13Nþ5 [M]þ 395.41, found
395.35.
(100 MHz, CDCl3, ppm) d 159.01, 157.18, 155.73, 155.47, 153.20,
151.52, 146.33, 140.33, 140.13, 139.40, 138.94, 135.84, 133.67, 130.97,
130.08, 129.46, 128.32, 128.19, 127.85, 127.55, 127.33, 126.72, 126.27,
124.55, 124.17, 124.06, 121.45, 121.32, 120.91, 120.80, 120.28, 120.02,
111.98, 109.13, 108.94, 81.00, 65.54; MALDI-TOF MS (m/z) calcd for
C45H25Nþ5 [M]þ 635.71, found 635.91.
4.1.6. 2-(3,6-Bis(9-phenyl-fluoren-9-yl)-carbazol-9-yl)-9H-4,5-dia-
zafluoren-9-one and 2-(3-(9-phenyl-9H-fluoren-9-yl)-9H-carbazol-
9-yl)-9H-4,5-diazafluoren-9-one (9 and 10). A sample of 7 (0.15 g,
0.4318 mmol) was dissolved in dry CH2Cl2 placed in the flask,
9-phenyl-fluorene-9-ol (PFOH) (0.25 g, 0.9678 mmol) was dis-
solved in dry CH2Cl2 in a constant dripping funnel, BF3$Et2O (0.4 ml)
was injected in the flask, the aqueous turned into green from yellow
immediately, stirred in room temperature, the PFOH was added in
the flask by dropwise, the solution turned into purple accordingly,
stirred at room temperature for 48 h, the reaction was quenched
by water and ethanol, then extracted with CH2Cl2. The combined
extracts were dried over anhydrous MgSO4, concentrated, and the
4.1.9. 2-(2-(3,6-Bis(9-phenyl-fluoren-9-yl)-carbazol-9-yl)-9H-4,5-
diazafluoren-9-ylidene)malononitrile (13). The procedure is similar
to the preparation of 11. Compound 10 (0.2 g, 0.2416 mmol) and
malononitrile (0.01756 g, 0.2658 mmol) were dissolved in DMSO
(2.1 ml), then the mixture was stirred at 110 ꢀC for 5 h. After washed
with MeCN, the product 13 (0.14 g, 65%) was obtained as a brown-
ish black precipitation; [found: C, 87.79; H, 4.23. C64H37N5 requires
C, 87.75; H, 4.26%]; 1H NMR (400 MHz, CDCl3, ppm):
J¼12.4 Hz, 1H), 8.85 (s, 1H), 8.13 (s, 1H), 8.06e8.04 (d, J¼7.6 Hz, 1H),
d 8.99e8.96 (d,

1982
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7.87 (s, 1H), 7.83 (s, 1H), 7.81e7.79 (d, J¼7.2 Hz, 4H), 7.47e7.45 (d,
J¼7.6 Hz, 4H), 7.39e7.36 (t, J¼14.8 Hz, 6H), 7.30e7.26 (m, 16H), 7.25
(s, 1H); 13C NMR (100 MHz, CDCl3, ppm)
d 157.09, 155.54, 151.58,
146.43, 140.08, 139.40, 139.29, 139.15, 138.97, 133.67, 131.81, 131.01,
130.39, 130.07, 129.85, 129.48, 128.92, 128.31, 128.10, 127.79, 127.52,
127.27, 126.71, 126.27, 124.14, 124.00, 120.25, 109.06, 81.01, 65.55;
MALDI-TOF MS (m/z) calcd for C64H37Nþ5 [M]þ 876.01, found 876.97.
5. Kulkami, A. P.; Zhu, Y.; Babel, A.; Wu, P. T.; Jenekhe, S. A. Chem. Mater. 2008, 20,
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4.2. X-ray crystallographic data
6. Ling, Q. D.; Song, Y.; Lim, S. L.; Teo, E. Y. H.; Tan, Y. P.; Zhu, C. X.; Chan, D. S. H.;
Kwong, D. L.; Kang, E. T.; Neoh, K. G. Angew. Chem., Int. Ed. 2006, 45, 2947.
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Crystallographic data for 2 are saved as the cif file, 2.cif.
C11H5BrN2O, M¼261.08, colorless diamond 0.30ꢂ0.15ꢂ0.12 mm,
monoclinic, P2(1)/n, Z¼4, a¼3.888 (ꢀ3), b¼21.646 (16), c¼11.389 (9),
3
¼90.00ꢀ,
b
¼99.578 (10)ꢀ,
¼90.00 , V¼945.2 (12) A , F(000)¼512,
g
ꢀ
a
Dc¼1.835 Mg mꢁ3
,
m
(Mo K
a
)¼4.317 mmꢁ1. Reflections collected/
unique 3776/1647 (Rint¼0.0336), Final
R indices (I>2s (I))
R1¼0.0990, wR2¼0.2428,
R
indices (all data) R1¼0.1067,
wR2¼0.2464. Crystallographic data (excluding structure factors) for
the structures in this paper have been deposited with the Cam-
bridge Crystallographic Data centre as supplementary publication
numbers CCDC 760634. Copies of the data can be obtained, free of
charge, on application to CCDC, 12 Union Road, Cambridge CB2 IEZ,
UK [fax: þ44 (0) 1223 336033 or e-mail: deposit@ccdc.cam.ac.uk].
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M.; Tao, Y. T.; Chuen, C. H. Adv. Funct. Mater. 2004, 14, 83; (e) Kitamura, C.;
Tanaka, S.; Yamashita, Y. Chem. Mater. 1996, 8, 570.
Acknowledgements
12. (a) Rajaram, S.; Armstrong, P. B.; Kim, B. J.; Frechet, J. M. J. Chem. Mater. 2009, 21,
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We thank the “973” project (2009CB930600), NNSFC (Grants
20704023, 60876010, 60706017, and 20774043), the Key Project of
Chinese Ministry of Education (No. 104246, 208050, 707032), the
NSF of the Education Committee of Jiangsu Province (Grants
08KJB510013, BK2008053, SJ209003, TJ209035, BK2009025), and
the Nanjing Science and Technology Centre (200907003). Dr. Bin
Liu, National University of Singapore (NUS), is appreciated for her
helpful discussion of photophysics.
Supplementary data
20. (a) Mlochowski, J.; Szulc, Z. J. Prakt. Chem. 1980, 322, 971; (b) Harel, T.; Shefer,
1H NMR, 13C NMR, GCeMS, and MALDI-TOF MS spectral data for
all corresponding products are provided. Supplementary data
associated with this article can be found in the online version at
doi:10.1016/j.tet.2010.12.065. These data include MOL files and
InChIKeys of the most important compounds described in this
article.
N.; Hagooly, Y.; Rozen, S. Tetrahedron 2010, 66, 3297.
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