Synthesis of conjugated-bridged triphenylenes and application in OLEDs

Article abstract of DOI:10.1039/b100083g

Novel conjugated-bridged triphenylene derivatives with electroluminescent properties were synthesized. A six step synthesis yields the cyanomethyltriphenylene derivatives (7a-7d). These were condensed by applying a Knoevenagel reaction with the alkoxy sub

Full text of DOI:10.1039/b100083g

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Synthesis of conjugated-bridged triphenylenes and application in
OLEDs
Roland Freudenmann, Boris Behnisch and Michael Hanack*
Institut fu¨r Organische Chemie Lehrstuhl II, Universita¨t Tu¨bingen, Auf der Morgenstelle 18,
D-72076 Tu¨bingen, Germany. E-mail: hanack@uni-tuebingen.de; Fax: z49-7071-295268;
http://www.uni-tuebingen.de/hanack/index.html
Received 3rd January 2001, Accepted 8th March 2001
First published as an Advance Article on the web 12th April 2001
Novel conjugated-bridged triphenylene derivatives with electroluminescent properties were synthesized. A six
step synthesis yields the cyanomethyltriphenylene derivatives (7a–7d). These were condensed by applying a
Knoevenagel reaction with the alkoxy substituted dialdehyde 8 to PPV analogous short chain compounds 9a–
9d. The products 9a–9d show bright orange to red photoluminescence. They are suitable as the emissive layer in
organic light-emitting diodes (OLEDs), both in single and double layer arrangements with copper
phthalocyanine as the hole transport layer.
obtained e.g. from o-dialkoxybenzenes by oxidative trimeris-
11
Introduction
ation with FeCl3,10 MoCl5 or VOCl3.12
Since the discovery of light emission from poly-p-phenylene-
vinylene (PPV)1 and analogous polymers,2 organic light-
emitting diodes (OLEDs) based on conjugated polymers are
of wide research interest.3 Substitution of the PPV backbone
increases the solubility and allows tailoring of the electronic
and optical properties in many directions. Besides the
introduction of substituents, a partial or complete replacement
of the phenylene rings in the PPV by different moieties (for
example naphthalene, anthracene or heterocycles3b) offers the
The synthesis of 9 requires a synthetic pathway for the
preparation of an unsymmetrically substituted triphenylene (in
our case the CH-acid cyanomethyl substituted triphenylenes
7a–7d) which will be submitted to a Knoevenagel reaction with
the terephthalaldehyde 8 (Scheme 2).
The synthesis of unsymmetrical Tps has been much less
explored than the symmetrically substituted hexaalkoxy
triphenylenes. A rational route involves the iodine promoted
photocyclisation of ortho-terphenyls.13 A selective coupling of
a 3,3,4,4-tetraalkoxybiphenyl and a 1,2-dialkoxybenzene is also
possible.14 Another route to unsymmetrically substituted
triphenylenes involves the oxidative coupling of unsymmetri-
cally substituted terphenyls with FeCl3,15 monofunctionalised
triphenylenes have also been synthesized by various methods
starting from symmetrically substituted hexaalkoxytripheny-
lenes.16,17
For the synthesis of a conjugated bridged Tp 9, a CN-PPV
linked to two unsymmetrically substituted triphenylenes, we
have chosen the route given in Scheme 1. This includes the
synthesis of a methyl substituted triphenylene (5) which could
be converted into the cyano derivative 7. Due to its acetic
hydrogens 7 would react in a Knoevenagel reaction with the
dialdehyde 8 to then form the conjugated bridged Tp 9.
Systems with high planarity and p-conjugation like 9 show a
strong tendency for aggregation and are expected to be
insoluble. This problem can be reduced by using alkoxy
substituted triphenylenes in which the peripheral alkoxy
substituents differ in their chain lengths. Thereby, the solubility
of the compounds 9a–9d in organic solvents with increasing
chain lengths should become better. In addition the effect of
luminescence properties of these conjugated systems can be
studied depending upon different substituents.
The first step of the synthetic route given in Schemes 1 and 2
is an ether synthesis of catechol (1) with an alkyl bromide in
acetonitrile at 80 ‡C with K2CO3 as base giving 2b–2d in yields
of at least 90%. For the palladium catalysed step (3A4) it is
necessary to have a halogen atom in the starting material 3a–
3d. As the bromination of 2b–2d often leads to polybrominated
products, we prefered to introduce iodine, which is possible in
high yields (w90%) by using iodine/iodic acid.18 Lithiation of
3a–3d with butyllithium (3a is commercially available) at
278 ‡C, followed by transmetallization with ZnCl2 leads to the
possibility of tuning the light-emitting properties in
a
controlled manner. Molecules with a low molecular weight
are of special interest: due to easy thin layer fabrication by a
high-vacuum deposition technique the processability is
enhanced and the impurities that arise from polymerisation
steps can be avoided.4 Moreover, conjugated short-chain
model compounds often show similar properties, when
compared with the corresponding polymers.5 Recently, the
triphenylene system, especially hexaalkoxy substituted triphe-
nylenes have gained increased interest in the construction of
OLEDs. Not only the discotic properties of these compounds,
but also their hole transporting properties have been investi-
gated.6–8 On the other hand, for a balanced electron flow in a
light-emitting device there is also an additional layer with
increased electron transport properties recommended. Alkoxy
substituted PPV derivatives, containing electron withdrawing
cyano groups (CN-PPV), are therefore suitable compounds.2,9
Up to now, one had to take at least double or triple layer
arrangements for an efficient OLED. A combination of hole
and electron transporting properties within one single molecule
should have a favourable effect on the preparation of an
OLED.
In this paper we present for the first time the p-conjugated
systems 9 (Scheme 2), containing a combination of the
thermally stable and hole transporting triphenylene system
with solubilizing alkoxy chains and a structural unit, that is
part of the electron conducting and also light-emitting CN-
PPV.2
Results and discussion
Most of the various syntheses of triphenylenes (Tp) lead to
symmetric hexaalkoxy-substituted triphenylenes, which were
1618
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This journal is # The Royal Society of Chemistry 2001
DOI: 10.1039/b100083g

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Scheme 1 Synthesis of the monocyanomethylene precursors 7a–7d: a) ether synthesis, b) I2/HIO3, c) I) BuLi, II) ZnCl2, III) 3,4-dibromotoluene,
[P(Ph)3]4Pd, d) FeCl3, e) NBS-bromination, f) [(Et)4N]CN/CH2Cl2.
intermediate organozinc compound. Pd-catalysed coupling of
the organozinc compound with 0.5 eq. dibromotoluene yields
the substituted o-terphenyls 4a–4d.19 Side products (e.g. homo
coupled biphenylenes) are removed by column chromatogra-
phy. The products 4a–4d were used without further purifica-
tion. Cyclisation of 4a–4d with FeCl3 in dichloromethane at
room temperature gives the unsymmetrically substituted
triphenylenes 5a–5d with yields for these two steps between
48 (5a) and 9% (5d). Longer alkyl chains in 3a–3d give lower
yields, because of the insolubility of the iodine derivatives at the
low reaction temperature for the lithiation step. The sub-
sequent bromination of 5a–5d in CCl4 with NBS and
azoisobutyronitrile leads to the bromomethyl products 6a–6d
(yieldsw60 %). Reaction of 6a–6d with tetraethylammonium
cyanide in dichloromethane at room temperature results in the
desired monofunctional cyanomethyltriphenylenes 7a–7d
(yields: 70–80%). 7a–7d and the substituted terephthalaldehyde
8 are precursors for the products 9a–9d, by applying the
Knoevenagel reaction (yields 48 to 54%).2 All compounds are
Photophysical properties
The UV-absorption of symmetrical substituted hexaalkoxy-
triphenylenes is about 280 nm, the photoluminescence (PL) is
at the edge of the visible area (380–420 nm).17 They exhibit
good hole transporting properties, when used in organic light-
emitting diodes.6–8 By extending the p-conjugated system as
shown for the new bridged triphenylene 9a–9d, the UV-
absorption as well as the PL maxima in comparison to
hexaalkoxytriphenylenes are strongly shifted to the red (see
Fig. 1). 9a–9d show strong orange to red photoluminescence
that meets the requirements for the preparation of OLEDs.
Therefore, we investigated the electroluminescent properties of
the triphenylenes 9a–9d by preparing single layer (ITO/TpPPV/
Al) and double layer (ITO/PcCu/TpPPV/Al) organic light-
emitting diodes. For controlling the electroluminescent cap-
ability, for an enhanced reproducibility and for a better
comparison of the investigated compounds we carried out a
screening test by preparing devices that contain 25 light-
emitting segments. For the schematic assembly of a device see
Fig. 2a. The commercially available ITO-glass substrate was
cut into 5 cm65 cm plates, which is advantageous due to the
1
characterized by H-NMR, 13C-NMR (with exception of the
bistriphenylenes 9a–9d due to their low solubility), MS, IR and
UV-spectroscopy (see Experimental).
Scheme 2 Synthesis of the bridged triphenylenes 9a–9d by Knoevenagel reaction (potassium tert-butoxide, THF).
J. Mater. Chem., 2001, 11, 1618–1624
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Fig. 1 UV-Vis absorption (solid line, measured in solution (CHCl3)),
photoluminescence (PL) (solid line, measured as thin film) and
electroluminescence (EL) spectra of the bridged triphenylenes 9a–9d.
The single layer EL spectra are plotted as solid circles, the double layer
spectra (ITO/PcCu/Emitter/Al) are shown as open squares. The UV-Vis
spectra of a thin film of copper phthalocyanine (PcCu) is depicted in the
first plot (open circles).
size-match to usual photo-type slides. A single light-emitting
segment is approx. 0.4 cm60.8 cm (an image of a single light-
emitting segment under forward current is shown in Fig. 2b).
The way of structuring the ITO-layer was done in the easy and
convenient way, which we have described earlier.20 After
several washing and cleaning steps the organic layers and the
air-stable aluminium cathode were evaporated in high-vacuum
(161025 mbar, layer thickness PcCu 10–30 nm, emitter 40–
80 nm). The EL spectra of all devices (single and double layer)
are shown in Fig. 1 together with the corresponding PL spectra
obtained from vacuum deposited thin films. The emission
maxima are listed in Table 1.
Due to the longer alkyloxy chains the PL maxima of 9b–9d
are shifted 25 nm to the red, when compared with 9a. The EL
maxima of the single layer devices are in good agreement with
the PL values (630 nm, orange–red), whereas the spectra of the
double layer devices strongly differ from the PL spectra, which
is caused by the additional PcCu layer. PcCu is a good and
commonly used hole transport layer and enhances the long-
term stability as well as the efficiency of the device,21 but PcCu
has two UV-absorption maxima at 624 and 695 nm (see Fig. 1).
Reabsorption of the emitted light occurs and the spectra and
the resulting emission color are changed, when compared to the
single layer device. Depending on the thickness of PcCu the
maxima can be shifted more than 60 nm to the blue, e.g. for 9a
(the optimized thickness of PcCu is discussed between 2 and
30 nm, see lit.21a).
Due to the preparation method (deposition of a relatively
large emitting area (25 cm2)) and the resulting natural gradient
of the layer thickness of the different emitting segments, the
determination of precise efficiency values is difficult. The
efficiency and luminescence of several emitting segments were
calculated according to literature by assuming a lambertian
emission.22 The values for the luminescence are between 0.5
and 2.5 cd m22 (measured at 20 V) with the devices showing
onset voltages around 8 V. The photograph (Fig. 2b) was taken
at daylight with an applied voltage of 16 V. The obtained
values for the new bridged triphenylenes are not optimized and
can be improved by controlling the layer thicknesses of the hole
transport layer as well as the emitter layer. Improvement of the
Fig. 2 a) Schematic set-up of the organic light-emitting diode, b)
emission of TpPPV1 (9a) in a double layer arrangement with PcCu,
measured at 16 V.
electron injection by introducing an additional LiF layer23 at
the emitter/aluminium cathode interface to enhance the
intensities is under investigation.
Conclusions
We have prepared new monofunctional triphenylene deriva-
tives containing a methyl (5a–5d), bromomethyl (6a–6d) or a
cyanomethyl group (7a–7d), which are useful for linking two
triphenylene systems maintaining full p-conjugation. This was
carried out by a double Knoevenagel reaction with the
monofunctionalized cyanomethyltriphenylene derivatives
(7a–7d) and a suitable terephthalaldehyde compound (8).
The obtained bridged bistriphenylenes (9a–9d) are highly
conjugated and exhibit strong orange to red photolumines-
cence (lmax$630 to 660 nm). They show a strong bath-
ochromic shift of more than 250 nm when compared with a
single triphenylene system. Up to now, triphenylenes were only
used as a hole tranport material in organic light-emitting
diodes. In an electroluminescent screening method by prepar-
ing single and double layer devices with 25 segments we have
shown that highly conjugated triphenylenes are possible
candidates for use in displays. The triphenylene derivatives
9a–9d exhibit bright orange to red electroluminescence which is
visible in daylight. The comparison of single layer devices with
double layer devices showed a marked shift in the emission
maxima, which is assigned to reabsorption of the hole
transport layer copper phthalocyanine.
1620
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13C-NMR: 22.5, 25.0, 37.8, 67.5, 67.6, 82.4, 115.5, 122.5, 129.7,
149.1, 150.0; IR (NaCl): 633, 798, 818, 839, 872, 889, 920, 982,
1003, 1015, 1055, 1138, 1171, 1219, 1250, 1290, 1321, 1367,
1387, 1429, 1474, 1501, 1582, 2569, 2646, 2719, 2870, 2932,
2955, 3074; MS: 376 (Mz), 306, 236, 110, 71, 55, 43; UV-VIS:
285.
Table 1 Absorption and emission maxima. UV/Vis absorption,
photoluminescence (PL) and electroluminescence (EL) maxima (wave-
length units, nm) of the TpPPVs 9a–9d.
UV
(sol.,
CHCl3)
EL
PL
(thin film) device)
EL
(single layer (double layer
with CuPc)
TpPPV1 (9a)
TpPPVi4 (9b) 271, 458 660
TpPPVi5 (9c) 272, 461 660
271, 458 635
631
632
632
635
571
586
645
654
1,2-Bis(hexyloxy)-4-iodobenzene (3d). Yield: 35.6 g, 88 mmol
(88.0%); 1H-NMR: 0.90 (t, J~6.53 Hz, 6H), 1.21–1.47 (m, 12H),
1.78 (m, 4H), 3.95 (t, J~6.54 Hz, 4H), 6.58 (d, J3~8.30 Hz, 1H),
7.12 (d, J4~2.02 Hz, 1H), 7.14 (dd, J3~8.30 Hz, J4~2.02 Hz,
1H); 13C-NMR: 13.9, 22.5, 25.5, 25.6, 29.0, 29.2, 31.4, 31.5, 69.1,
69.2, 115.5, 122.5, 129.7, 149.1, 150.0; IR (NaCl): 631, 739, 795,
839, 868, 939, 1015, 1045, 1055, 1136, 1219, 1248, 1290, 1321,
1393, 1468, 1501, 1583, 2731, 2858, 2929, 2953; MS: 404, 278, 194,
110, 85, 55, 43; UV-VIS: 285.
TpPPV6 (9d)
272, 461 660
Experimental
Chemicals received from commercial sources (Aldrich and
Fluka) were used without further purification. All reactions
were performed under a dry nitrogen atmosphere. Solvents
were dried according to standard procedures. The melting
points are uncorrected. NMR spectra were recorded with a
Bruker AC 250 spectrometer at 250 MHz (1H) and 62.9 MHz
(13C) in CDCl3 and internally referenced to CHCl3 (1H:
d~7.24, 13C: d~77.00). Infrared spectra were taken as KBr
pellets or with NaCl carriers using a Bruker IFS 48 spectro-
meter. UV-Vis spectra were recorded in CHCl3 solution with a
Shimadzu UV-2102 PC. Mass spectra were recorded on a
Finnigan ISQ 70 and a Varian MAT 711 A. Elemental analysis
of the products was carried out with a VarioEL V, the E.A. of
the precursors are in order. PL of evaporated thin films was
measured with a SPEX fluorolog 112 in the 45‡ configuration.
For EL measurements a HP 6030A voltage source was used
together with a Keithley 171 DMM. The EL spectra were taken
from devices with ITO/[copper phthalocyanine (PcCu)]/emit-
ter/Al configuration with a waveguide diode array set-up in air
at room temperature. The following compounds were prepared
as described in the literature: the dialkyl ethers 2b–2d were
synthesized by ether synthesis of catechol (1) and alkyl
bromides in acetonitrile at 80 ‡C with K2CO3 giving 2b–2d in
yields of over 90%. The spectroscopic data of 2b–2d were
described in the literature.24 2,5-Bis(2-ethylhexyloxy)terephthal-
General procedure for the preparation of the 2,3,6,7-
tetrakis(alkyloxy)-10-methyltriphenylenes 5a–5d
The reaction was carried out under nitrogen. To a solution of
45.0 mmol bromoveratrole (3a) or 1,2-bis(alkyloxy)-4-iodo-
benzene (3b–3d) in 100 ml THF, 32 ml of a 1.60 M solution of
butyllithium (50.0 mmol) in hexane was added at 278 ‡C,
immediately followed by a solution of 6.21 g dried zinc chloride
(45.0 mmol) in 50 ml THF. The mixture was stirred for one
more hour at 278 ‡C and refluxed for an additional hour.
15.0 mmol dibromotoluene were stirred together with 0.1 g
tetrakis(triphenylphosphine)palladium in THF for 10 min
before adding to the reaction mixture. The mixture was kept
under reflux for 16 h. The resulting o-terphenyls 4a–4d were
extracted with diethyl ether. Byproducts were mainly removed
by column chromatography. The crude product was cyclised
with 45.0 mmol FeCl3 in dichloromethane and 2 drops of conc.
H2SO4. After stirring for 4 h the mixture was quenched with
methanol. The solvents were removed. The crude product was
purified by repeated column chromatography (silica gel;
dichloromethane–petroleum ether eluents). The products 5a–
5d can be recrystallized from ethanol.
aldehyde
Compound 3a is commercially available.
8
was prepared according to the literature.5d
2,3,6,7-Tetramethoxy-10-methyltriphenylene (5a). White plates,
1
mp 246–248 ‡C; yield: 2.59 g, 6.9 mmol (47.6% for 2 steps); H-
NMR: 2.60 (s, 3H), 4.09–4.11 (4s, 12H), 7.40 (d, J~8.39 Hz, 1H),
7.74 (s, 2H), 7.92 (s, 1H), 7.94 (s, 1H), 8.23 (s, 1H), 8.34 (d,
J~8.39 Hz, 1H); 13C-NMR: 21.8, 55.8, 103.8, 103.8, 104.1, 104.2,
122.5, 122.6, 123.1, 123.2, 123.4, 123.8, 126.4, 127.4, 128.8, 135.3,
148.4,148.5,148.7, 149.0;13C-NMR(DEPT-135):21.8,55.8,103.8,
103.8, 104.1, 104.2, 122.5, 122.6, 127.4;IR(KBr):627, 644, 777, 802,
843, 860, 928, 964, 1026, 1045, 1157, 1173, 1202, 1215, 1263, 1304,
1346, 1383, 1410, 1420, 1447, 1466, 1520, 1543, 1616, 2831, 2912,
2935, 2955, 3003; MS: 362 (Mz), 347, 333, 319, 304, 288, 181, 138;
UV-VIS: 266, 275, 302, 341, 358.
General procedure for the preparation of the monoiodines 3b–3d
0.10 mol of 2b–2d were added to a solution of 75 ml glacial
acetic acid, 25 ml water and 2.0 ml conc. H2SO4. Before heating
to 40 ‡C 40.3 mmol iodine was added. 24.5 mmol iodic acid was
added in 3 parts, the first one following the addition of the
iodine, the second and third after one and two hours,
respectively. After 3.5 h the solution product was extracted
with diethyl ether and washed with solutions of sodium
hydrogensulfite and potassium carbonate. Drying in vacuum
yielded the pure product 3b–3d.
2,3,6,7-Tetraisobutoxy-10-methyltriphenylene (5b). White plates,
1
1,2-Diisobutoxy-4-iodobenzene (3b). Yield: 33.4 g, 96 mmol
(96.4%); 1H-NMR: 1.02 (d, J~6.46 Hz, 12H), 2.10 (t sept,
J~6.46 Hz, 2H), 3.70 (d, J~6.46 Hz, 4H), 6.59 (d,
J3~8.36 Hz, 1H), 7.11 (d, J4~2.04 Hz, 1H), 7.16 (dd,
J3~8.36 Hz, J4~2.04 Hz, 1H); 13C-NMR: 19.2, 28.3, 28.3,
75.6, 75.7, 82.4, 115.7, 122.8, 129.7, 149.4, 150.3; IR (NaCl):
633, 798, 818, 829, 871, 889, 920, 982, 1003, 1015, 1055, 1138,
1071, 1218, 1250, 1290, 1321, 1367, 1387, 1429, 1474, 1501,
1582, 2648, 2719, 2870, 2932, 2956; MS: 348 (Mz), 292, 236,
222, 166, 110, 57, 43; UV-VIS: 285.
mp 166–167 ‡C, yield: 2.25 g, 4.2 mmol, (28.2% for 2 steps); H-
NMR:1.15 (d, J~6.5 Hz, 24H), 2.27(dsept, J~6.5 Hz, 4H)2.61 (s,
3H), 4.02 (d, 12H), 7.39 (d, J~8.25 Hz, 1H), 7.82 (s, 2H), 7.96 (s,
1H), 7.98 (s, 1H), 8.24 (s, 1H), 8.34 (d, J~8.25 Hz, 1H); 13C-NMR:
19.4, 21.8, 28.7, 75.7–76.1, 107.4, 122.8, 124.4, 127.5, 129.0, 135.3,
149.5; IR (KBr): 624, 762, 802, 839, 851, 860, 874, 924, 941, 955, 968,
1045, 1175, 1188, 1200, 1209, 1225, 1265, 1308, 1342, 1366,
1394, 1427, 1472, 1520, 1547, 1616, 2872, 2912, 2955, 3105; MS: 530
(Mz), 474, 418, 361, 318, 306, 277, 248, 57; UV-VIS: 267, 276, 302,
344, 361.
1,2-Bis(isopentyloxy)-4-iodobenzene (3c). Yield: 35.5 g,
94.8 mmol (94.5%); 1H-NMR: 0.95 (d, J~6.57 Hz, 12H),
1.67 (tt, 6.57 Hz, 4H) 1.82 (t sept, J~6.57 Hz, 2H), 3.95 (d,
J~6.57 Hz, 4H), 6.52 (d, J3~8.42 Hz, 1H), 7.17 (d,
J4~2.22 Hz, 1H), 7.20 (dd, J3~8.52 Hz, J4~2.22 Hz, 1H);
2,3,6,7-Tetrakis(isopentyloxy)-10-methyltriphenylene (5c). White
plates, mp 119–120 ‡C, yield: 1.08 g, 1.85 mmol (12.3% for 2 steps);
1H-NMR: 1.15 (d, J~6.4 Hz, 24H), 1.80–2.03 (m, 12H) 2.60 (s, 3H),
4.28(t, 6.0 Hz, 8H), 7.38(d, J~8.3 Hz,1H),7.84(s, 2H), 7.98(s,1H),
8.00 (s, 1H), 8.24 (s, 1H), 8.35 (d, J~8.3 Hz, 1H); 13C-NMR: 21.8,
J. Mater. Chem., 2001, 11, 1618–1624
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2,3,6,7-Tetrakis(hexyloxy)-10-bromomethyltriphenylene (6d).
22.6,25.3,38.1,67.0,67.8,68.0,68.1,106.8,107.0,107.1,107.2,122.8,
122.9, 123.6, 123.7, 123.9, 124.3, 126.7, 127.5, 129.0, 135.5, 149.0,
149.1, 149.2, 149.4; IR (KBr): 623, 714, 761, 802 841, 860, 881, 920,
949, 982, 1018, 1061, 1171, 1184, 1211, 1225, 1263, 1302, 1367,
1385,1425,1468,1518,1541,1614,2363,2870,2932,2955,3101;MS:
586 (Mz), 516, 446, 376, 306, 71, 43; UV-VIS: 266, 276, 302, 343,
360.
Yellow powder, mp 139–141 ‡C, yield: 1.14 g, 1.58 mmol
(63.2%); 1H-NMR: 0.92 (t, J~5.9 Hz, 12H), 1.39 (m, 16H),
1.57 (m, 8H), 1.90 (m, 4H), 4.23 (t, J~5.68 Hz, 8H), 4.75 (s,
3H), 7.57 (d, J~8.48 Hz, 1H), 7.79 (s, 2H), 7.94 (s, 2H), 8.33 (s,
1H), 8.34 (d, J~8.48 Hz, 1H); 13C-NMR: 14.0, 22.6, 25.8, 29.3,
31.7, 34.4, 69.3, 69.4, 69.6, 106.9, 123.2, 123.4, 123.7, 124.4,
124.4, 126.7, 128.9, 129.0, 135.0, 149.1, 149.7, 149.8; IR (KBr):
633, 663, 725, 810, 839, 872, 881, 924, 962, 1020, 1049, 1072,
1175, 1184, 1204, 1228, 1242, 1265, 1310, 1329, 1389, 1427,
1443, 1466, 1512, 1543, 1614, 2854, 2928, 2952; MS: 724 (Mz),
720, 643, 557, 389, 317, 277, 148, 97, 82, 80, 71, 55, 53, 43; UV-
VIS: 281, 368.
2,3,6,7-Tetrakis(hexyloxy)-10-methyltriphenylene (5d). White
plates, mp 115–117 ‡C, yield: 870 mg, 1.35 mmol (9.0% for 2
steps); 1H-NMR:0.85(t, J~6.7 Hz, 12H), 1.09 (m, 16H), 1.49 (m,
8H), 1.85 (tt, J~6.4 Hz, 4H) 2.61 (s, 3H), 4.14 (t, J~6.4 Hz, 8H),
7.30 (d, J~8.37 Hz, 1H), 7.74 (s, 2H), 7.88 (s, 1H), 7.90 (s, 1H),
8.14 (s, 1H), 8.26 (d, J~8.37 Hz, 1H); 13C-NMR: 14.1, 21.8, 22.7,
25.9, 29.5, 31.7, 69.4, 69.5, 69.8, 69.9, 107.3, 122.8, 123.8, 124.4,
126.7, 127.5, 129.0, 135.3, 149.2, 149.5; IR (KBr): 623, 725, 762,
802, 839, 860, 872, 924, 959, 1022, 1051, 1070, 1173, 1184, 1195,
1209, 1219, 1240, 1265, 1306, 1386, 1427, 1466, 1518, 1616, 2856,
2926,2956,3104;MS:642,558,473,389,318,305,276,247,85, 55,
43; UV-VIS: 266, 276, 302, 345, 360.
General procedure for the preparation of the
cyanomethyltriphenylenes 7a–7d
2.0 mmol 2,3,6,7-tetrakis(alkyloxy)-10-bromomethyltripheny-
lenes (6a–6d) were dissolved in 100 ml dichloromethane. A
solution of 2.2 mmol tetraethylammonium cyanide in dichlor-
omethane was added dropwise in 15 min. The reaction mixture
was stirred for another 2 h at room temperature. The solution
was washed with water, the organic phase was dried over
MgSO4 and the solvent was evaporated. The crude product 7a–
7d was purified by column chromatography (silica gel;
dichloromethane–petroleum ether).
General procedure for the preparation of the
bromomethyltriphenylenes 6a–6d
2.5 mmol
2,3,6,7-tetrakis(alkyloxy)-10-methyltriphenylenes
(5a–5d) were dissolved in 500 ml of dry CCl4 under nitrogen
atmosphere. After adding 2.5 mmol NBS and 0.10 g AIBN the
reaction was kept under reflux for 16 h. The solvent was
evaporated. The products 6a–6d were purified by washing with
methanol (3650 ml).
2,3,6,7-Tetramethoxy-10-cyanomethyltriphenylene(7a). Yellow–
brown powder, mp 233 ‡C, yield: 490 mg, 1.27 mmol (63.8%); 1H-
NMR: 3.94 (s, 2H), 4.07 (s, 12H), 7.42 (d, J3~7.18 Hz, J4~1.50 Hz
1H), 7.60 und 7.61 (2s, 2H), 7.75 (s, 1H), 7.79 (s, 2H), 8.31 (s, 1H),
8.36 (d, J~7.18 Hz, 1H); 13C-NMR: 23.9, 55.9, 56.0, 56.6, 104.0,
104.0, 104.2, 104.4, 118.1, 122.0, 122.6, 122.8, 123.7, 123.9, 124.1,
125.2, 127.1, 128.2, 129.0, 148.8, 149.5, 149.6; IR (KBr): 619, 777,
802, 810, 824, 837, 1018, 1034, 1047, 1151, 1167, 1184, 1194, 1213,
1261, 1306, 1383, 1412, 1425, 1448, 1472, 1518, 1545, 1618,
2245, 2831, 2912, 2941, 2963, 2991, 3005; MS: 387 (Mz), 376,
361,344,330,312, 304, 258,215,193, 152, 93;UV-VIS:276,302,344,
361.
2,3,6,7-Tetramethoxy-10-bromomethyltriphenylene (6a). White–
yellowish powder, mpw280 ‡C, yield: 660 mg, 1.5 mmol (60.2%);
1H-NMR: 4.06–4.08 (4s, 12H), 4.76 (s, 2H), 7.56 (dd, J3~8.46 Hz,
J4~1.81Hz, 1H), 7.56 (s, 1H), 7.59 (s, 1H), 7.74 (s, 1H), 7.86 (s, 1H),
8.32 (d, J3~8.39 Hz, 1H), 8.34 (d, J4~1.81 Hz, 1H); 13C-NMR:
34.5, 55.9, 55.9, 56.0, 56.6, 103.8, 104.0, 104.3, 104.5, 122.8, 122.9,
123.2, 123.5, 123.9, 124.0, 126.6, 128.6, 128.7, 135.0, 148.7, 149.4,
149.5; IR (KBr): 633, 777, 804, 814, 822, 835, 1022, 1038, 1051, 1153,
1169, 1198, 1215, 1232, 1261, 1306, 1383, 1412, 1425, 1452, 1472,
1506, 1520, 1543, 1618, 2829, 2910, 2937, 2957, 2988;MS:442 (Mz),
440, 361, 347, 332, 317, 304, 180, 96, 94, 82, 80, 40;UV-VIS:281, 348,
365.
2,3,6,7-Tetraisobutoxy-10-cyanomethyltriphenylene (7b). Yellow–
brown powder, mp 123–127 ‡C, yield: 920 mg, 1.65 mmol (82.7%);
1H-NMR: 1.13 (d, J~6.63 Hz, 24H), 2.26 (sept t, J~6.63 Hz, 4H),
3.98(d,J~6.63 Hz12H),3.99(s,2H),7.47(d,J~8.56 Hz,1H),7.79(s,
2H), 7.91 (s, 1H), 7.96 (s, 1H), 8.34 (s, 1H), 8.43 (d, J~8.56 Hz, 1H);
13C-NMR: 19.3, 23.9, 28.6, 75.6, 75.7, 75.9, 76.0, 106.8, 106.9, 107.0,
107.1,118.1,122.3,122.9,123.1,124.0,124.3,124.5,125.3,127.1,128.6,
129.3, 149.4, 150.0, 150.1; IR (KBr): 802, 839, 864, 874, 893, 905, 922,
943,953,972,984,1003,1049,1072,1082,1113,1175,1202,1265,1367,
1393, 1427, 1441, 1472, 1514, 1543, 1614, 2247, 2872, 2910, 2957; MS:
555, 530, 499, 473, 443, 416, 386, 361, 331, 306, 278, 248, 57, 41; UV-
VIS: 277, 304, 345, 362.
2,3,6,7-Tetraisobutoxy-10-bromomethyltriphenylene (6b). White–
yellowishpowder,mp172–174 ‡C,yield:960 mg,1.59 mmol(63.5%);
1H-NMR: 1.14 (d, J~6.5 Hz, 24H), 2.24 (m, 4H), 3.99 (d, J~6.8 Hz
12H), 4.77(s, 2H), 7.58 (d, J~8.52 Hz, 1H), 7.79(s, 2H), 7.93 (s, 2H),
8.41(s,1H),8.43(d,J~8.52 Hz,1H);13C-NMR:19.4,28.6,34.4,75.6,
75.7, 75.9, 106.9, 107.0, 107.0, 107.1, 123.2, 123.2, 123.4, 123.7, 124.4,
124.5, 126.7, 128.9, 129.0, 135.0, 149.3, 149.4, 149.9, 150.0; IR (KBr):
633, 690, 719, 804, 839, 870, 922, 970, 1005, 1030, 1047, 1175,
1190,1200,1209,1229,1265,1306,1329,1367,1393,1437,1472,1512,
1543, 1614, 2872, 2908, 2957, 3103; MS: 610 (Mz), 608, 530, 473,
417, 361, 317, 306, 277, 248, 231, 80, 82, 57, 43; UV-VIS: 281, 249,
366.
2,3,6,7-Tetrakis(isopentyloxy)-10-cyanomethyltriphenylene (7c).
Yellow–brown powder, mp 142–144 ‡C, yield: 830 mg,
1.36 mmol (68%); H-NMR: 1.03 (d, J~6.45 Hz, 24H), 1.84–
1
2,3,6,7-Tetrakis(isopentyloxy)-10-bromomethyltriphenylene (6c).
Yellow powder, mp 165–167 ‡C, yield: 900 mg, 1.35 mmol
(54.2%); 1H-NMR: 1.04 (d, J~6.45 Hz, 24H), 1.79–1.97 (m,
12H), 4.24 (m, 8H), 4.76 (s, 2H), 7.58 (d, J~8.24 Hz, 1H), 7.81
(s, 2H), 7.96 (s, 2H), 8.41 (s, 1H), 8.43 (d, J~8.24 Hz, 1H); 13C-
NMR: 22.7, 25.3, 34.4, 38.0, 68.8, 67.9, 68.0, 106.8, 106.8,
106.9, 107.0, 123.2, 123.4, 123.7, 124.4, 126.7, 128.9, 129.0,
135.0, 149.1, 149.1, 149.7, 149.8; IR (KBr): 621, 633, 797, 808,
841, 918, 972, 984, 1015, 1059, 1123, 1175, 1188, 1198, 1211,
1229, 1267, 1311, 1331, 1367, 1389, 1429, 1443, 1466, 1522,
1543, 1614, 2866, 2928, 2553; MS: 666. (Mz), 642, 600, 586,
516, 445, 375, 305, 277, 248, 82, 80, 71, 43; UV-VIS: 282, 349,
368.
1.91 (m, 12H), 4.05 (s, 2H), 4.24 (t, J~6.57 Hz, 8H), 7.47 (d,
J~7.18 Hz, 1H), 7.81 (s, 2H), 7.94 (s, 2H), 8.34 (s, 1H), 8.47 (d,
J~7.18 Hz, 1H); 13C-NMR: 22.7, 23.9, 25.3, 38.0, 67.8, 67.9,
68.0, 68.0, 106.8, 106.8, 106.9, 118.1, 122.3, 122.9, 123.1, 123.9,
124.3, 124.5, 125.3, 127.2, 128.5, 129.3, 149.2, 149.8, 149.9; IR
(KBr): 804, 841, 972, 984, 1016, 1059, 1124, 1173, 1198, 1213,
1265, 1304, 1337, 1367, 1385, 1425, 1443, 1466, 1516, 1543,
1614, 1670, 1695, 1718, 2249, 2868, 2955, 3103; MS: 611, 586,
541, 400, 343, 331, 302, 235, 82, 80, 71, 43; UV-VIS: 277, 303,
344, 362.
2,3,6,7-Tetrakis(hexyloxy)-10-cyanomethyltriphenylene (7d). Yellow–
brown powder, mp 105–107 ‡C, yield: 1.12 g, 1.68 mmol
1622
J. Mater. Chem., 2001, 11, 1618–1624

View Online
plates, mpw330 ‡C, yield: 160 mg, 0.09 mmol (54.0%); 1H-
(83.9%); 1H-NMR: 0.92 (t, J~6.5 Hz, 12H), 1.38 (m, 16H),
1.57 (m, 8H),
NMR: 0.88 (m, 30H), 1.20–1.70 (m, 64H), 1.70–2.10 (m, 18H),
4.11 (d, 5.35 Hz, 4H), 4.25 (t, 5.95 Hz, 16H), 7.84 (s, 4H), 7.90
(d, 9.40 Hz, 2H), 8.01 (s, 2H), 8.05 (s, 2H), 8.09 (s, 2H), 8.24 (s,
2H), 8.50 (d, 9.05 Hz, 2H), 8.78 (s, 2H); IR (KBr): 802, 824,
839, 872, 924, 932, 953, 960, 972, 1013, 1022, 1032, 1049, 1070,
1111, 1221, 1178, 1219, 1248, 1267, 1319, 1385, 1429, 1466,
1514, 1541, 1616, 2208, 2858, 2928, 2955; MS (FD): 1688 (Mz);
UV-VIS: 272, 461; EA: calculated for C112H156N2O10, C 79.62,
H 9.24, N 1.66; found: C 76.92, H 8.84, N 1.56.
1.93 (m, 8H), 3.97 (s, 2H), 4.22 (t, J~6.35 Hz, 8H), 7.47 (d,
J~8.38 Hz, 1H), 7.80 (s, 2H), 7.93 (2s, 2H), 8.33 (s, 1H),
8.42 (d, J~8.38 Hz, 1H); 13C-NMR: 14.0, 22.6, 23.9, 25.8,
29.3, 31.7, 69.4, 69.5, 69.6, 69.7, 106.9, 106.9, 107.0, 107.0,
118.1, 122.3, 122.9, 123.1, 123.9, 124.3, 124.5, 125.3, 127.1,
128.5, 129.3, 149.1, 149.7, 149.8; IR (KBr): 612, 725, 764,
802, 839, 872, 924, 941, 962, 1020, 1051, 1072, 1177, 1200,
1211, 1265, 1308, 1427, 1443, 1466, 1514, 1614, 1693, 2249,
2365, 2854, 2925, 2953, 3103; MS: 667 (Mz), 642, 583, 557,
499, 473, 414, 389, 331, 302, 277, 85, 55, 43; UV-VIS: 277,
305, 344, 361.
Acknowledgements
This research was supported by the Fonds der Chemischen
Industrie. We would also like to thank Professor Dr. D. Oelkrug
and Dipl. Chem. L. Lu¨er from the Institute of Physical
and Theoretical Chemistry at the University of Tu¨bingen for
the technical assistance in the photo- and electroluminescence
part.
General procedure for the preparation of the bistriphenylenes 9a–
9d
The reaction was carried out under nitrogen. 0.50 mmol
2,3,6,7-tetrakis(alkyloxy)-10-cyanomethyltriphenylenes (7a–
7d) and 0.22 mmol 2,5-bis(2-ethylhexyloxy)terephthalaldehyde
(8) were dissolved in dry THF and heated to 40 ‡C. 0.50 mmol
potassium tert-butanolate and 4 drops of a methanolic solution
of tetra-n-butylammonium hydroxide were added. After
30 min the products 9a–9d precipitated and were centrifuged
after addition of methanol. The product was washed with
methanol (36) and recrystallized from chloroform.
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plates, mpw330 ‡C, yield: 94 mg, 0.08 mmol (37.7%); 1H-
NMR: 0.86 (t, 6.20 Hz, 3H), 0.97 (t, 7.03 Hz), 1.20–1.80 (m,
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0.85 (t, 7.37 Hz, 3H), 0.97 (t, 7.55 Hz, 6H), 1.14 (d, 6.70 Hz,
48H), 1.20–1.70 (m, 16H), 1.86 (m, 2H), 2.26 (d sept, 8.87 Hz,
8H), 4.03 (m, 16H), 4.10 (d, 5.55 Hz, 4H), 7.82 (s, 4H), 7.86 (d,
9.37 Hz, 2H), 7.98 (s, 2H), 8.05 (s, 2H), 8.07 (s, 2H), 8.23 (s,
2H), 8.52 (d, 9.04 Hz, 2H), 8.77 (s, 2H); IR (KBr): 613, 802,
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6.55 Hz, 48H), 1.20–1.70 (m, 16H), 1.70–2.10 (m, 26H), 4.11 (d,
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1624
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