Synthesis, electrochemical and optical properties of stable yellow fluorescent fluoranthenes

Article abstract of DOI:10.1021/jo100420x

Figure presented A novel series of thermally stable yellow light emitting fluoranthenes with an amine donor and a nitrile acceptor was prepared from a ketene-S,S-acetal under mild conditions without using an organometal catalyst. The organic light emitting device of yellow fluoranthene 10b exhibited substantially low turn-on voltage (2.6 V) and maximum brightness of 470 Cd/m² with luminance efficiency of 2.0 Cd/A without using any dopant.

Full text of DOI:10.1021/jo100420x

pubs.acs.org/joc
Synthesis, Electrochemical and Optical Properties of Stable Yellow
Fluorescent Fluoranthenes†
Atul Goel,*,‡ Vijay Kumar,‡ Sumit Chaurasia,‡ Madhu Rawat,§ Ramesh Prasad,§ and
R. S. Anand§
‡Division of Medicinal and Process Chemistry, Central Drug Research Institute, CSIR, Lucknow 226001,
India, and Department of Electrical Engineering, Indian Institute of Technology, Kanpur 208016, India
§
agoel13@yahoo.com; atul_goel@cdri.res.in
Received March 6, 2010
A novel series of thermally stable yellow light emitting fluoranthenes with an amine donor and a
nitrile acceptor was prepared from a ketene-S,S-acetal under mild conditions without using an
organometal catalyst. The organic light emitting device of yellow fluoranthene 10b exhibited
substantially low turn-on voltage (2.6 V) and maximum brightness of 470 Cd/m2 with luminance
efficiency of 2.0 Cd/A without using any dopant.
Introduction
often fabricated by doping a yellow fluorophore such as
rubrene.2 However, the success of the doping technology
requires selection of appropriate dopant and/or dopant
concentration to avoid phase separation in a host-dopant
system leading to ineffective energy transfer.3 Therefore,
novel nondoped illuminants with efficient electrolumines-
cence are essentially in great demand.
Intense research has been focused on examining optical and
electronic properties of 9,9-disubstituted fluorenes and poly-
fluorenes for developing OLEDs4,5 (Figure 1, I-III); however,
comparatively very little attention has been devoted to the
closely related scaffold, fluoranthene (IV).
Considering the growing importance of energy conserva-
tion, modernization, and miniaturization requirements,
polymer light emitting diodes (PLEDs) and small molecule
organic light emitting diodes (OLEDs) have generated amaz-
ing enthusiasm toward developing next generation electro-
luminescent (EL) material.1 These multicolored illuminants
have wide application ranging from flat surface displays to
leading edge lighting technology, automobile industry, home
appliances, and cell phone business.
To achieve high EL quantum efficiency, a doping ap-
proach is commonly employed. For example, in a typical
yellow OLED configuration, the yellow-emitting layer is
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Published on Web 05/06/2010
DOI: 10.1021/jo100420x
r
2010 American Chemical Society

Goel et al.
JOCArticle
Grignard reagents19 or Pd-catalyzed electrocyclic reaction
of a substituted acenaphthene.20
Recently we have shown that appropriately functionalized
donor-acceptor quateraryls21 and 9-unsubstituted fluor-
enes22a and fluorenones exhibited efficient, stable blue
emission and demonstrated their potential application in
developing blue OLEDs. We have demonstrated how the
positioning of donor-acceptor groups onto the fluorene-
fluorenone backbone transforms the green emission to blue
emission.22a To investigate photophysical properties of
fluoranthenes, a simple, general, and efficient synthetic route
that could offer flexibility of diverse functional groups in
their molecular framework was desirable. However, there is a
paucity of literature protocols that could generate fluor-
anthene derivatives with donor-acceptor and various chro-
mophoric functionalities in a rapid manner. Although
numerous Diels-Alder reactions23 of 2H-pyran-2-ones with
electron-deficient and electron-rich dienophiles do provide
annulated benzene derivatives, to the best of our knowledge,
none has utilized the chemistry of 2H-pyran-2-ones for
preparing fluoranthene scaffold. On the basis of retro-synth-
esis, we envisaged that the reaction of 2H-pyran-2-ones (3
and 9) with 2H-acenaphthylen-1-one (4) may furnish fluor-
anthene derivatives under mild conditions.
FIGURE 1. Fluorenes I-III and fluoranthenes IV-V.
Fluoranthenes possess interesting electronic and thermal
properties6 similar to those of fluorene with an advantage of
having an oxidatively labile 9-methylene moiety of fluorene
blocked by a 1,9-fused benzene ring. Recent reports on fluor-
anthene scaffold include fabrication of highly efficient blue
OLEDs,7,8 green OLEDs,9 and fluoranthene-based matrix
material10 to improve charge-carrier transport. In this paper,
we report a highly rapid novel approach for the synthesis of
thermally stable donor-acceptor fluoranthenes (V) and
their potential use in preparing economical, efficient non-
doped yellow-OLED devices.
Results and Discussion
Few synthetic methodologies are available for the synth-
esis of fluoranthene derivatives, which mainly include the
cycloaddition reaction of cyclopentadienone derivatives and
alkynes or alkenes,11,12 Suzuki-Heck reaction of 1-bromo-
naphthalene and 2-bromophenyl boronic acid,13 reaction in-
volving two triple bonds in 1,8-bis(phenylethynyl)naphtha-
lene under thermal or photochemical conditions14 or in the
presence of metal catalysts15 such as RhCl3-Aliquat 336,16
1,4-palladium migration from 2-iodo-1-phenylnaphtha-
lene,17 reaction of propargylic alcohol bearing a fluorene
moiety with diphenyl phosphine oxide,18 or benzoannula-
tion reactions of R-oxoketene dithioacetals with various
The reaction of methyl 2-carbomethoxy-3,3-bis(methyl-
sulfanyl)acrylate22 1 with substituted acetophenones (2a-e)
under alkaline conditions furnished substituted 2H-pyran-2-
ones (3a-e) in excellent yields. Our approach to prepare
substituted fluoranthenes 5a-e involved stirring an equimo-
lar mixture of 3a-e, 2H-acenaphthylen-1-one (4) in the
presence of NaH, and dry THF at room temperature for
35-90 min as shown in Scheme 1. The plausible reaction
mechanism for the ring transformation of 2H-pyran-3-car-
boxylic acid methyl esters 3a-e into fluoranthenes 5a-e
showed that the reaction is possibly initiated by Michael
addition of a conjugate base of 2H-acenaphthylen-1-one (4)
at position C6 of lactone 3, followed by intramolecular
cyclization involving the carbonyl functionality of 4 and
C3 of the pyranone ring followed by elimination of carbon
dioxide to yield 5a-e.
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Magnus, P. P. J. Phys. Chem. A 2002, 106, 1961.
To demonstrate the synthetic utility and scope of this
methodology for regiospecific introduction of electron donor
or acceptor functionalities, we explored the synthesis of fluor-
anthene derivatives with an amine donor and a nitrile acceptor
substituent. An independent reaction of methyl 2-cyano-3,3-
bis(dimethylsulfanyl)acrylate (6) with 1-acetylnaphthalene or
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Samanta, S.; Ray, J. K. Org. Lett. 2008, 10, 4795.
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B.; Verma, J. K.; Jain, M.; Anand, R. S.; Manoharan, S. S. Org. Lett. 2009,
11, 1289. (b) Tominaga, Y. Trends Heterocycl. Chem. 1991, 2, 43. (c) Goel,
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references cited therein.
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SCHEME 1. Synthesis of Fluoranthenes 5a-e
SCHEME 2. Synthesis of Fluoranthenes10a-c
with an amine donor (piperidine/pyrrolidine) and a nitrile
acceptor group respectively as in the case of fluoranthenes
10a-c (λPL 549-552 nm), a remarkable red shift of nearly
70 nm was observed. These findings match the results
demonstrated by Yamaguchi-Yoshida and co-workers.25
By the modification of the donor groups at the terminal
position of polycyano-oligo(phenyleneethylene) fluoro-
phores, they found that the PL is more red-shifted in the
presence of an amine functionality compared to the fluoro-
phore having a methylsulfanyl group. Unsubstituted fluor-
anthene showed the quantum efficiency of about 20% in
cyclohexane.24 The quantum yields of synthesized fluor-
anthenes 5a-e and 10a-c are shown in Table 1, which
revealed that the presence of the methylsulfanyl donor group
at position 8 and the carbomethoxy acceptor group at
position 9 of fluoranthenes 5a-e showed low quantum
efficiency (Φ=1.8-5.1%) while fluoranthenes 10a-c sub-
stituted with an amine donor and a nitrile acceptor group
showed better quantum yields (Φ= 36-56%) compare to
those of unsubstituted fluoranthene.
The electrochemical studies were carried out to ascertain
the redox behavior of the fluoranthenes (5a-e, 10a-c, and
12). Cyclic voltammetric measurements were performed in a
three-electrode cell setup with Ag/AgCl as the standard
electrode and Pt disk as the working electrode, 2 mM of
fluoranthenes, and 0.2 M of electrolyte tetrabutylammo-
nium hexafluorophosphate (Bu4NPF6) dissolved in DMF.
All the potentials were calibrated taking ferrocene as stan-
dard and the data are summarized in Table 1.
with 1-acetylpyrene was carried out to afford 6-aryl-3-cyano-4-
methylsulfanyl-2H-pyran-2-ones (8a,b) in 80-90% yields. To
prepare compounds with different donor functionalities, the
methylsulfanyl group of lactones (8a,b) was replaced with
various secondary amines such as piperidine or pyrrolidine
to furnish 6-aryl-2-oxo-4-amin-1-yl-2H-pyran-3-carbonitriles
(9a-c) in good yields. Further stirring an equimolar mixture of
9 and 2H-acenaphthylen-1-one (4) in the presence of NaH in
THF for 12-15 min at room temperature yielded 10-aryl-
8-(amin-1-yl)fluoranthene-7-carbonitriles 10a-c in 82-85%
yields (Scheme 2).
To generalize our methodology, an attempt was made to
prepare 8-methylsulfanylacenaphtho[1,2-j]fluoranthene-7-
carbonitrile (12). The parent precursor 10-methylsulfanyl-
8-oxo-8H-7-oxa-fluoranthene-9-carbonitrile (11) was pre-
pared by the reaction of 6 with 2H-acenaphthylen-1-one
(4) at 0-5 °C under alkaline conditions in 70% yield (Scheme
3). The cyclic lactone 11 was reacted with 2H-acenaphthylen-
1-one (4) in the presence of NaH in THF for 25 min and
afforded 5-methylsulfanylacenaphtho[1,2-j]fluoranthene-4-
carbonitrile (12) in 54% yield. It is worth mentioning that
these polycyclic systems are not easy to synthesize by classi-
cal approaches.
Table 1 shows the λmax of their UV and fluorescence spectral
data, fluorescence quantum yield, HOMO/LUMO energy
levels, and electrochemical band gap (Eop) of fluoranthenes
5a-e, 10a-c, and 12. Figure 2 shows the UV-vis and PL
spectra of fluoranthenes (5a, 5c, and 10a-c), respectively.
Unsubstituted fluoranthene exhibits PL maxima at two
wavelengths (431 and 455 nm).24 Fluoranthenes 5a-e con-
taining SMe and COOMe groups show PL in the range of
481-487 nm; however, when these groups were replaced
One irreversible oxidation and one reversible reduction
peak were observed for all fluoranthenes as shown in Figure
3 (see the Supporting Information), which indicates that
radical anions are stable entities but the radical cations
(oxidized species) may react with the solvent DMF or
supporting electrolyte. On close examination of CV graphs,
(24) Elliott, E. L.; Orita, A.; Hasegawa, D.; Gantzel, P.; Otera, J.; Siegel,
J. S. Org. Biomol. Chem. 2004, 3, 581.
(25) Yamaguchi, Y.; Ochi, T.; Wakamiya, T.; Matsubara, Y.; Yoshida, Z.
Org. Lett. 2006, 8, 717.
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SCHEME 3. Synthesis of Acenaphtho[1,2-j]fluoranthene-7-carbonitrile 12
TABLE 1. Photophysical and Electrochemical Properties of
Fluoranthenes 5a-e, 10a-c, and 12
a
b
d
λmax;abs
(nm)
λmax;em
(nm)
Φfc
(%)
HOMO
(eV)
LUMO
(eV)
Eop
(eV)
entry
5a
5b
5c
5d
5e
319, 370
314, 365
313, 375
311, 375
298, 368
482
481
483
481
487
550
5.1
3.2
4.9
4.7
1.8
56
-5.69
-5.72
-5.72
-5.70
-5.67
-5.27
-2.85
-2.82
-2.84
-2.85
-2.83
-2.77
2.84
2.90
2.88
2.85
2.84
2.50
10a 338, 357*,
440
10b 331
10c 332
552
549
483
36
51
8.9
-5.34
-5.51
-5.77
-2.85
-2.85
-3.10
2.49
2.46
2.67
12
357
aLongest wavelength absorption maximum in THF (the asterisk
indicates the shoulder peak). bFluorescence emission maximum in
THF. cFluorescence quantum yield relative to harmine in 0.1 M
H2SO4 as a standard (Φ = 0.45). dOptical band gap from CV.
FIGURE 3. Cyclic voltammograms of 5a, 5c and 10a and 10b
(in DMF).
206 °C respectively, while 10c with a bulky pyrene group
showed a higher melting temperature of 330 °C (see the
Supporting Information).
On the basis of the above studies, fluoranthenes 10a-c
having an amine donor and a nitrile acceptor group were
selected for further electroluminescent studies. Multilayer
devices were fabricated to investigate the performance of
yellow light-emitting fluoranthenes (10a-c) with the device
configuration of ITO/PEDOT:PSS (40 nm)/NPB(20 nm) /
fluoranthenes (60 nm)/BCP (8 nm)/Ca(3.2 nm)/Al (200 nm).
The relative energy-level alignment of the fabricated multi-
layered OLEDs and actual device picture of 10b are shown in
Figure 5.
Figure 6 shows the ILV characteristics of 10a-c. The
“turn-on” voltage and luminances of the devices 10a, 10b
(Figure 7), and 10c were found to be 3 V (17.91 Cd/m2), 2.6 V
(5.0 Cd/m2), and 3 V (7.65 Cd/m2), respectively. The low
“turn on” voltage suggests efficient charge injection into the
emitting layer. The turn-on voltage of 2.6 V in the case of
device 10b is quite impressive. One of the important objec-
tives of developing OLEDs is to reduce the operating voltage
and current to drive these OLED displays with commercially
available drivers of 5 V outputs. The low information con-
tent displays like 7-segment and general displays for signage
have a large market. Luminance intensity of 381 Cd/m2 at
5 V for compound 10b is good enough for such applica-
tions (Figure 7). The devices of fluoranthenes 10a-c exhi-
bited maximum luminance of 410, 470, and 420 Cd/m2,
respectively.
The similarity of the photoluminescence (λPL 549-552
nm) and the electroluminescence (λΕL 554-559 nm) spectra
suggests that the EL was attributed to emission from the
radiation decay of the excited state of fluoranthenes 10a-c.
To further evaluate the electrochemical stability of fluor-
anthenes (10a-c), the EL spectra of these fluoranthenes were
recorded with an increase in applied voltage at an interval of
1 V (Figure 8). All the devices were found to be stable even
FIGURE 2. Absorbance and fluorescence spectra of fluoranthenes
5a, 5c, and 10a-c in THF (∼10-6 M).
we observed that incorporation of an amine donor and nitrile
acceptor moieties decreases the oxidation potential of fluora-
nthenes (10a-c) with respect to fluoranthenes (5a-e). How-
ever, no change was observed in reduction potentials and
hence the bandgap of fluoranthenes 10a-c was found lower
than that of fluoranthenes 5a-e.
The thermal properties of fluoranthenes 10a-c were
gauged by thermogravimetric analysis (TGA) and differen-
tial scanning calorimetry (DSC) (see the Supporting Infor-
mation). The TGA and DSC traces of 10b are shown in
Figure 4. Fluoranthenes 10a-c exhibited good thermal
stability. The TG thermogram of 10b exhibited high thermal
stability as evidenced by its TGA, with its 5% weight loss
temperature under nitrogen atmosphere being up to 300 °C.
The temperature corresponding to the complete weight
loss of 10a, 10b, and 10c was 600, 435, and 470 °C, respec-
tively. DSC was performed in the temperature range from
30 to 340 °C under nitrogen atmosphere at the rate of
10 deg/min. Fluoranthenes 10a and 10b melted at 239 and
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JOCArticle
FIGURE 4. TGA and DSC plots of 10b under N2 atmosphere.
FIGURE 5. Relative energy-level alignment and layer thickness of 10a-c OLEDs and actual device picture of fluoranthene 10b.
FIGURE 7. ILV characteristics (current density and luminance) of
10b (insert: the EL spectrum).
fluoranthene-based yellow OLEDs, which exhibited bright
yellow fluorescence, high quantum efficiency, and good ther-
mal stability. One of the Y-OLEDs showed bright yellow emi-
ssion with low turn-on voltage of 2.6 V and maximum bright-
ness of 470 Cd/m2 with luminance efficiency of 2.0 Cd/A (at
5 V) without using any dopant. The series of fluoranthenes
10a-c demonstrating emission in the yellow region may solve
the problem of dopant aggregation to a large extent. Owing to
interesting photophysical, electrochemical, and thermal prop-
erties, these compounds may also find application for devel-
oping new yellow fluorescent molecular probes.
FIGURE 6. ILV characteristics of device of 10a, 10b, and 10c
respectively.
under bias stress up to 9 V. Out of three OLEDs (10a-c), the
device of 10b was quite efficient with low turn-on voltage (2.6
V) and giving good luminance efficiency of 2.0 Cd/A (at 5 V)
with a maximum luminance of 470 Cd/m2.
In summary, we have demonstrated a novel approach for the
synthesis of D/A fluoranthenes and acenaphtho[1,2-j]fluor-
anthene from ketene-S,S-acetals in excellent yields through
carbanion-induced ring transformation of 2H-pyran-2-ones as
a key step. Our methodology is simple and convenient and does
not require any specialized organometal catalyst or reagents.
We have successfully fabricated highly efficient nondoped
Experimental Section
1
General. H and 13C NMR spectra were taken at 200, 300,
and 400 MHz, respectively. CDCl3 was taken as the solvent.
3660 J. Org. Chem. Vol. 75, No. 11, 2010

Goel et al.
JOCArticle
hexane as the eluent to afford 299 mg (65%) of 5b as a yellow
solid. Rf 0.54 (1:1 chloroform-hexane); mp 208-210 °C; MS
(ESI) 461 (Mþ þ 1), 463 (Mþ þ 3); IR (KBr) 3060, 2942, 1724,
1656, 1586 cm-1; 1H NMR (300 MHz, CDCl3) δ 2.55 (s, 3H),
4.15 (s, 3H), 7.15-7.20 (m, 2H), 7.36-7.49 (m, 3H), 7.59-
7.72 (m, 3H), 7.79 (d, J=8.1 Hz, 1H), 7.83-7.90 (m, 2H); 13
C
NMR (75.5 MHz, CDCl3) δ 18.1, 52.7, 122.4, 122.7, 123.0,
127.2, 127.7, 127.9, 128.0, 128.7, 129.9, 130.6, 131.9, 132.8,
133.8, 134.6, 134.8, 134.9, 136.8, 138.7, 138.8, 168.7; HRMS
(DART) calcd for C25H18BrO2S 461.01958, found 461.02109.
Synthesis of Methyl 10-(Furan-2-yl)-8-(methylsulfanyl)-
fluoranthene-7-carboxylate (5c). A mixture of 3c (266 mg,
1 mmol, 1 equiv), compound 4 (168 mg, 1 mmol, 1 equiv), and
NaH (60% dispersion in oil, 60 mg, 1.5 mmol, 1.5 equiv) in dry
THF (5 mL) was stirred at room temperature for 35 min. The
progress of the reaction was monitored by TLC and on comple-
tion solvent was evaporated and the reaction mixture was poured
ontocrushed ice withvigorous stirring and finally neutralized with
10% HCl. The precipitate obtained was filtered and purified on a
silica gel column with 45% chloroform in hexane as the eluent to
afford 260 mg (70%) of 5c as a yellow solid. Rf 0.48 (1:1
chloroform-hexane); mp 140-142 °C; MS (EI) 372 (Mþ), 341
(Mþ - 31); IR (KBr) 3108, 3058, 2946, 1725, 1652, 1572 cm-1; 1H
NMR (400 MHz, CDCl3) δ 2.58 (s, 3H), 4.14 (s, 3H), 6.64-6.68
(m, 1H), 6.79-6.83 (m, 1H), 7.48 (s, 1H), 7.55 (t, J=5.72 Hz, 1H),
7.62 (t, J=5.72 Hz, 1H), 7.67-7.72 (m, 1H), 7.82-7.92 (m, 4H);
13C NMR (100 MHz, CDCl3) δ 18.4, 52.7, 109.5, 111.7, 122.5,
123.7, 127.4, 127.8, 127.9, 128.0, 128.4, 128.7, 129.5, 129.9, 132.9,
133.8, 134.4, 134.7, 135.2, 137.3, 142.5, 152.4, 168.7; HRMS calcd
for C23H16O3S 372.0820, found 372.0817.
FIGURE 8. Electrochemical stability vs voltage curves and yellow
OLEDs pictures of 10a-c.
Chemical shifts are reported in parts per million shift (δ value)
from Me4Si (δ 0 ppm for 1H) or based on the middle peak of the
solvent (CDCl3) (δ 77.00 ppm for 13C NMR) as an internal
standard. Signal pattern are indicate as follows: s, singlet; d,
doublet; dd, double doublet; t, triplet; and m, multiplet. Coup-
ling constants (J) are given in hertz. Infrared (IR) spectra were
recorded in KBr disk and reported in wavenumber (cm-1). An
ESIMS, EI spectrometer was used for mass spectra analysis.
UV/vis spectra were obtained with THF as solvent of choice
having a concentration of about 10-6 M. Fluorescence spectra
were obtained with THF as solvent of choice, having a concen-
tration of about 10-6 M. Melting points were measured with a
melting point apparatus. Cyclic voltammetry was done with Ag/
AgCl as the reference electrode. All the reactions were carried
out under anhydrous conditions and were monitored by TLC;
visualization was done with UV light (254 nm).
Synthesis of Methyl 8-(Methylsulfanyl)-10-phenylfluoranthene-
7-carboxylate (5a). A mixture of 3a (276 mg, 1 mmol, 1 equiv),
compound 4 (168 mg, 1 mmol, 1 equiv), and NaH (60% dis-
persion in oil, 60 mg, 1.5 mmol, 1.5 equiv) in dry THF (5 mL) was
stirred at room temperature for 45 min. The progress of the
reaction was monitored by TLC and on completion solvent was
evaporated and the reaction mixture was poured onto crushed ice
with vigorous stirring and finally neutralized with 10% HCl. The
precipitate obtained was filtered and purified on a silica gel
column with 40% chloroform in hexane as the eluent to afford
267 mg (70%) of 5a as a yellow solid. Rf 0.52 (1:1 chloro-
form-hexane); mp 210-212 °C; MS (EI) 382 (Mþ); IR (KBr)
2922, 2853, 1724, 1595 cm-1; 1H NMR (300 MHz, CDCl3) δ 2.55
(s, 3H), 4.15 (s, 3H), 7.14 (d, J = 6.9 Hz, 1H), 7.25 (s, 1H),
7.32-7.38 (m, 1H), 7.51-7.65 (m, 6H), 7.77 (d, J=8.1 Hz, 1H),
7.83-7.89 (m, 2H); 13C NMR (75.5 MHz, CDCl3) δ 18.1, 52.6,
122.6, 127.0, 127.7, 127.8, 128.2, 128.5, 128.7, 128.8, 129.0, 129.8,
132.9, 134.0, 134.4, 135.1, 136.7, 140.0, 140.2, 168.8; HRMS calcd
for C25H18O2S 382.1028, found 382.1031.
Synthesis of Methyl 8-(Methylsulfanyl)-10-(thiophen-2-yl)-
fluoranthene-7-carboxylate (5d). A mixture of 3d (282 mg,
1 mmol, 1 equiv), compound 4 (168 mg, 1 mmol, 1 equiv), and
NaH (60% dispersion in oil, 60 mg, 1.5 mmol, 1.5 equiv) in dry
THF (5 mL) was stirred at room temperature for 40 min. The
progress of the reaction was monitored by TLC and on comple-
tion solvent was evaporated and the reaction mixture was
poured onto crushed ice with vigorous stirring and finally
neutralized with 10% HCl. The precipitate obtained was filtered
and purified on a silica gel column with 40% chloroform in
hexane as the eluent to afford 264 mg (68%) of 5d as a yellow
solid. Rf 0.51 (1:1 chloroform-hexane); mp 152-154 °C; MS
(ESI) 388 (Mþ), 357 (Mþ - 31); IR (KBr) 2941, 1724, 1658,
1631, 1574 cm-1; 1H NMR (300 MHz, CDCl3) δ 2.56 (s, 3H),
4.15 (s, 3H), 7.21-7.25 (m, 1H), 7.31-7.36 (m, 2H), 7.38-7.46
(m, 2H), 7.50-7.54 (m, 1H), 7.58-7.66 (m, 1H), 7.79-7.91 (m,
3H); 13C NMR (75.5 MHz, CDCl3) δ 18.1, 52.7, 122.7, 123.1,
126.3, 127.1, 127.3, 127.4, 127.8, 128.0, 129.1, 129.8, 130.0,
132.4, 132.8, 133.7, 134.4, 134.8, 136.3, 136.8, 140.4, 168.6;
HRMS calcd for C23H16O2S2 388.05917, found 388.06130.
Synthesis of Methyl 8-(Methylsulfanyl)-9,10-diphenylfluoran-
thene-7-carboxylate (5e). A mixture of 3e (352 mg, 1 mmol,
1 equiv), compound 4 (168 mg, 1 mmol, 1 equiv), and NaH (60%
dispersion in oil, 60 mg, 1.5 mmol, 1.5 equiv) in dry THF (5 mL)
was stirred at room temperature for 90 min. The progress of the
reaction was monitored by TLC and on completion solvent was
evaporated and reaction mixture was poured onto crushed ice
with vigorous stirring and finally neutralized with 10% HCl.
The precipitate obtained was filtered and purified on a silica gel
column with 35% chloroform in hexane as the eluent to afford
275 mg (60%) of 5e as a white solid. Rf 0.55 (1:1 chloroform-
hexane); mp 254-256 °C; MS (EI) 458 (Mþ); IR (KBr) 3054,
Synthesis of Methyl 10-(4-Bromophenyl)-8-(methylsulfanyl)-
fluoranthene-7-carboxylate (5b). A mixture of 3b (355 mg,
1 mmol, 1 equiv), compound 4 (168 mg, 1 mmol, 1 equiv), and
NaH (60% dispersion in oil, 60 mg, 1.5 mmol, 1.5 equiv) in dry
THF (5 mL) was stirred at room temperature for 40 min. The
progress of the reaction was monitored by TLC and on comple-
tion solvent was evaporated and the reaction mixture was
poured onto crushed ice with vigorous stirring and finally
neutralized with 10% HCl. The precipitate obtained was filtered
and purified on a silica gel column with 40% chloroform in
1
2997, 1728, 1635, 1555 cm-1; H NMR (300 MHz, CDCl3) δ
2.10 (s, 3H), 4.18 (s, 3H), 6.51 (d, J=7.1 Hz, 1H), 7.11-7.21 (m,
7H), 7.25-7.32 (m, 4H), 7.61-7.67 (m, 1H), 7.77 (d, J=8.2 Hz,
1H), 7.81-7.89 (m, 2H); 13C NMR (75.5 MHz, CDCl3) δ 20.6,
52.7, 121.9, 123.9, 126.7, 127.1, 127.2, 127.3, 127.7, 127.9, 128.2,
129.6, 129.8, 130.4, 130.5, 133.0, 133.8, 134.3, 134.7, 135.5,
J. Org. Chem. Vol. 75, No. 11, 2010 3661

Goel et al.
JOCArticle
138.5, 138.8, 138.9, 139.6, 146.3, 169.1; HRMS calcd for
C31H22O2S 458.1341, found 458.1337.
Synthesis of 10-(Methylsulfanyl)-8-oxo-8H-7-oxa-fluoran-
thene-9-carbonitrile (11). A mixture of methyl 2-cyano-3,3-bis-
(methylsulfanyl)acrylate 6 (203 mg, 1 mmol, 1 equiv), 2H-acena-
phthylen-1-one 4 (168 mg, 1 mmol, 1 equiv), and NaH (60%
dispersion in oil, 48 mg, 1.2 mmol, 1.2 equiv) in dry THF (6 mL)
was stirred at 0-5 °C for 30-35 min. The progress of the reac-
tion was monitored by TLC and on completion solvent was eva-
porated and the reaction mixture was poured onto crushed ice
with vigorous stirring. The precipitate obtained was filtered and
purified on silica gel column with chloroform as the eluent to
afford 203 mg (70%) of 11 as an orange solid. Rf 0.35
(chloroform); mp 220-222 °C; MS (EIþ) 291 (Mþ); IR (KBr)
2817, 2217, 1695, 1595, 1528 cm-1; 1H NMR (200 MHz, CDCl3)
δ 3.14 (s, 3H), 7.67-7.79 (m, 2H), 7.94 (d, J = 8.3 Hz, 1H),
8.11-8.13 (m, 2H), 8.26 (d, J=7.08 Hz, 1H); HRMS calcd for
C17H9NO2S 291.0354, found 291.0354.
Synthesis of 8-(Methylsulfany)acenaphtho[1,2-j]fluoranthene-
7-carbonitrile (12). A mixture of 11 (291 mg, 1 mmol, 1 equiv),
compound 4 (168 mg, 1 mmol, 1 equiv), and NaH (60% dispersion
in oil 60 mg, 1.5 mmol, 1.5 equiv) in dry THF (6 mL) was stirred at
room temperature for 25 min. The progress of the reaction was
monitored by TLC and on completion solvent was evaporated and
the reaction mixture was poured onto crushed ice with vigorous
stirring and finally neutralized with 10% HCl. The precipitate
obtained was filtered and purified on a silica gel column with
20% chloroform in hexane as the eluent to afford 214 mg (54%)
of 12 as a yellow solid. Rf 0.71 (1:1 chloroform-hexane); mp >
250 °C; MS (ESI) 398 (Mþ þ 1); IR (KBr) 2964, 2229, 1633, 1426
cm-1;1H NMR (300 Hz, CDCl3) δ2.62 (s, 3H), 7.67-7.79 (m, 4H),
7.89-7.99 (m, 4H), 8.55-8.61 (m, 2H), 8.65 (d, J=7.2 Hz, 1H),
8.95 (d, J=7.2 Hz, 1H); 13C NMR (75.5 MHz, CDCl3) δ19.9, 111.4,
117.9, 124.0, 125.2, 125.6, 126.2, 128.1, 128.3, 128.6, 128.7, 128.8,
129.1, 130.3, 133.6, 133.7, 133.9, 134.1, 134.6, 135.2, 135.8, 136.0,
139.1, 141.9; HRMS calcd for C28H15NS 397.0925, found 397.0919.
Experimental Device. Multilayer devices were fabricated to
investigate the performance of yellow light-emitting materials
(10a, 10b, and 10c) with the device configuration of ITO/
PEDOT:PSS (40 nm)/NPB(20 nm)/fluoranthenes (60 nm)/
BCP (8 nm)/Ca(3.2 nm)/Al (200 nm). The patterned ITO glass
plate was cleaned in 6:1:1 in RCA-I solution, rinsed in DI water
a number of times, and then dried. The ITO surface was treated
in ozone for 15 min. Immediately, the first layer of poly(3,4-
ethylenedioxythiophene) doped with poly(styrenesulfonic acid)
(PEDOT:PSS) was spin-coated on patterned ITO to form a hole
injection layer. The PEDOT-PSS was vacuum dried at 120 °C
for 1 h. All other organic layers and metal layers were sublimed
in high vacuum (∼1-5 ꢀ 10-6 mbar). Then devices were sealed
with a covering glass plate with UV epoxy. The ILV characteri-
stics of sealed OLED devices were obtained by using Keithley
source-measure unit. EL spectra were recorded with an optic
spectrometer.
Synthesis of 10-(Naphthalen-1-yl)-8-(pyrrolidin-1-yl)fluoran-
thene-7-carbonitrile (10a). A mixture of 9a (316 mg, 1 mmol,
1 equiv), compound 4 (168 mg, 1 mmol, 1 equiv), and NaH (60%
dispersion in oil, 60 mg, 1.5 mmol, 1.5 equiv) in dry THF (5 mL)
was stirred at room temperature for 12 min. The progress of the
reaction was monitored by TLC and on completion solvent was
evaporated and the reaction mixture was poured onto crushed
ice with vigorous stirring and finally neutralized with 10% HCl.
The precipitate obtained was filtered and purified on a silica gel
column with 30% chloroform in hexane as the eluent to afford
346 mg (82%) of 10a as a yellow solid. Rf 0.61 (1:1 chloroform-
hexane); mp 236-238 °C; MS (ESI) 423 (Mþ þ 1); IR (KBr)
1
2924, 2199, 1632, 1580 cm-1; H NMR (300 MHz, CDCl3) δ
1.98-2.12 (m, 4H), 3.68-3.82 (m, 4H), 6.16 (d, J=7.0 Hz, 1H),
6.61 (s, 1H), 7.02-7.09 (m, 1H), 7.27-7.33 (m, 1H), 7.45-7.71
(m, 6H), 7.86 (d, J=8.1 Hz, 1H), 7.96-8.04 (m, 2H), 8.75 (d, J=
7.0 Hz, 1H); 13C NMR (75.5 MHz, CDCl3) δ 25.8, 50.6, 89.1,
114.9, 120.3, 121.2, 123.9, 125.2, 125.5, 126.0, 126.1, 126.2,
126.4, 127.4, 127.8, 127.9, 128.2, 128.4, 129.4, 131.4, 132.4,
133.5, 134.7, 134.8, 137.9, 141.3, 143.5, 150.2; HRMS calcd
for C31H22N2 422.1783, found 422.1796.
Synthesis of 10-(Naphthalen-1-yl)-8-(piperidin-1-yl)fluoran-
thene-7-carbonitrile (10b). A mixture of 9b (330 mg, 1 mmol,
1 equiv), compound 4 (168 mg, 1 mmol, 1 equiv), and NaH (60%
dispersion in oil, 60 mg, 1.5 mmol, 1.5 equiv) in dry THF (5 mL)
was stirred at room temperature for 13 min. The progress of the
reaction was monitored by TLC and on completion solvent was
evaporated and the reaction mixture was poured onto crushed
ice with vigorous stirring and finally neutralized with 10% HCl.
The precipitate obtained was filtered and purified on a silica gel
column with 32% chloroform in hexane as the eluent to afford
370 mg (85%) of 10b as a yellow solid. Rf 0.62 (1:1 chloroform-
hexane); mp 206-208 °C; MS (ESI) 437 (Mþ þ 1); IR (KBr)
2931, 2848, 2214, 1642, 1578 cm-1; 1H NMR (300 MHz, CDCl3)
δ 1.62-1.67 (m, 2H), 1.81-1.89 (m, 4H), 3.24-3.35 (m, 4H),
6.33 (d, J = 7.1 Hz, 1H), 6.95 (s, 1H), 7.10-7.15 (m, 1H),
7.26-7.34 (m, 1H), 7.48-7.76 (m, 6H), 7.91 (d, J = 8.1 Hz,
1H), 7.98-8.05 (m, 2H), 8.70 (d, J=7.0 Hz, 1H); 13C NMR (75.5
MHz, CDCl3) δ 24.1, 26.2, 53.8, 99.4, 117.8, 119.6, 122.4, 123.6,
123.7, 125.5, 125.8, 126.1, 126.3, 126.5, 127.9, 128.0, 128.4,
128.6, 128.7, 129.6, 131.3, 131.8, 132.8, 133.6, 134.1, 134.5,
137.5, 141.1, 143.0, 156.3; HRMS calcd for C32H24N2
436.1940, found 436.1943.
Synthesis of 8-(Piperidin-1-yl)-10-(pyren-1-yl)fluoranthene-7-
carbonitrile (10c). A mixture of 9c (406 mg, 1 mmol, 1 equiv),
compound 4 (168 mg, 1 mmol, 1 equiv), and NaH (60% dis-
persion in oil, 60 mg, 1.5 mmol, 1.5 equiv) in dry THF (5 mL)
was stirred at room temperature for 15 min. The progress of the
reaction was monitored by TLC and on completion solvent was
evaporated and the reaction mixture was poured onto crushed
ice with vigorous stirring and finally neutralized with 10% HCl.
The precipitate obtained was filtered and purified on a silica gel
column with 30% chloroform in hexane as the eluent to afford
420 mg (82%) of 10c as a yellow solid. Rf 0.62 (1:1 chloroform-
hexane); mp >250 °C; MS (ESI) 513 (Mþ þ 1); IR (KBr) 2936,
Acknowledgment. We gratefully acknowledge financial
support by the Department of Science and Technology
(DST), New Delhi, India. V.K. and S.C. are thankful to
UGC and CSIR, New Delhi for senior research fellowships.
R.S.A. thanks the MHRD, New Delhi for financial support.
The spectroscopic data provided by SAIF, CDRI is grate-
fully acknowledged. Authors are thankful to Dr. G. K. Jain
and Dr. G. Palit, Scientist, CDRI for their support in
obtaining absorbance and fluorescence data.
1
2850, 2215, 1632, 1581 cm-1; H NMR (300 MHz, CDCl3) δ
1.61-1.68 (m, 2H), 1.83-1.91 (m, 4H), 3.25-3.35 (m, 4H), 6.15
(d, J=7.1 Hz, 1H), 6.95-7.01 (m, 1H), 7.04 (s, 1H), 7.62 (d, J=
8.2 Hz, 1H), 7.71-7.77 (m, 1H), 7.84-7.93 (m, 3H), 8.03-8.28
(m, 6H), 8.34 (d, J=7.8 Hz, 1H), 8.74 (d, J=7.1 Hz, 1H); 13
C
Supporting Information Available: 1H and 13C NMR spec-
tra, UV-vis and fluorescence spectra, DSC, TGA, cyclic vol-
tammograms and device efficiency graph for the compounds
5a-e, 10a-c, 11, and 12. This material is available free of charge
via the Internet at http://pubs.acs.org.
NMR (75.5 MHz, CDCl3) δ 24.1, 26.2, 53.8, 99.4, 117.9,
120.0, 122.4, 123.7, 124.7, 124.8, 124.9, 125.0, 125.4, 125.5,
126.2, 126.3, 126.7, 127.4, 127.9, 127.9, 128.0, 128.1, 128.7,
129.6, 131.0, 131.4, 132.0, 132.8, 134.1, 134.5, 134.8, 141.5,
143.1, 156.3.
3662 J. Org. Chem. Vol. 75, No. 11, 2010