Synthesis and self-assembly of functionalized hexa-peri-hexabenzocoronenes

Article abstract of DOI:10.1002/1521-3765(20001201)6:23<4327::AID-CHEM4327>3.0.CO;2-7

Monolayers of hexa-alkyl substituted derivatives of hexa-peri-hexabenzocoronene (HBC) 1b have previously been investigated by scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS). It is expected that different functional groups (electron donating or withdrawing) connected to the aromatic core will influence the packing pattern and possibly the current-voltage characteristics as well. In order to provide suitable model systems, a new synthetic approach to synthesize functionalized HBC derivatives has been developed. This was accomplished by [4+2]-cycloaddition of suitably bromo-substituted diphenyl-acetylenes and 2,3,4,5-tetraarylcyclo-penta-2,4-dien-1-ones followed by an oxidative cyclodehydrogenation with iron(III) chloride/nitromethane. Using this strategy three different substitution patterns were synthesized: 2-bromo-5,8, 11,14,17-pentadodecylhexa-peri-hexabenzocoronene (2a), 2,5-dibromo-8,11,14,17-pentadodecylhexa-peri-hexabenzocoronene (2b), and 2,11-dibromo-5,8,14,17-pentadodecylhexa-peri-hexabenzocoronene (2c). These bromo-substituted HBC derivatives were subjected to palladium catalyzed coupling reactions to give donor (alkoxy, amino) as well as acceptor (ester, cyano) substituted derivatives. The self-assembly of these new HBC derivatives was studied in the bulk as well as at an interface. DSC, optical microscopy, and X-ray diffraction revealed the existence of columnar mesophases. The bulk structure in the mesophase is largely insensitive to changes of the substitution pattern; however, in situ scanning tunneling microscopy at the solid-fluid interface between an organic solution of the HBC derivative and highly oriented pyrolytic graphite reveals different packing patterns of the first adsorbed monolayer.

Full text of DOI:10.1002/1521-3765(20001201)6:23<4327::AID-CHEM4327>3.0.CO;2-7

FULL PAPER
Synthesis and Self-Assembly of Functionalized
Hexa-peri-hexabenzocoronenes
Shunji Ito,[a] Mike Wehmeier,[a] J. Diedrich Brand,[a] Christian Kübel,[a] Rebekka Epsch,[b]
Jürgen P. Rabe,*[b] and Klaus Müllen*[a]
Abstract: Monolayers of hexa-alkyl
substituted derivatives of hexa-peri-hexa-
benzocoronene ꢀHBC) 1b have previ-
ously been investigated by scanning
tunneling microscopy ꢀSTM) and scan-
ning tunneling spectroscopy ꢀSTS). It is
expected that different functional
groups ꢀelectron donating or withdraw-
ing) connected to the aromatic core will
influence the packing pattern and possi-
bly the current-voltage characteristics as
well. In order to provide suitable model
systems, a new synthetic approach to
synthesize functionalized HBC deriva-
tives has been developed. This was
accomplished by [4 ‡ 2]-cycloaddition
of suitably bromo-substituted diphenyl-
acetylenes and 2,3,4,5-tetraarylcyclo-
penta-2,4-dien-1-ones followed by an
oxidative cyclodehydrogenation with
ironꢀiii) chloride/nitromethane. Using
this strategy three different substitution
patterns were synthesized: 2-bromo-
5,8,11,14,17-pentadodecylhexa-peri-hexa-
benzocoronene ꢀ2a), 2,5-dibromo-
8,11,14,17-pentadodecylhexa-peri-hexa-
benzocoronene ꢀ2b), and 2,11-dibromo-
5,8,14,17-pentadodecylhexa-peri-hexa-
benzocoronene ꢀ2c). These bromo-sub-
stituted HBC derivatives were subjected
to palladium catalyzed coupling reac-
tions to give donor ꢀalkoxy, amino) as
well as acceptor ꢀester, cyano) substitut-
ed derivatives. The self-assembly of
these new HBC derivatives was studied
in the bulk as well as at an interface.
DSC, optical microscopy, and X-ray
diffraction revealed the existence of
columnar mesophases. The bulk struc-
ture in the mesophase is largely insensi-
tive to changes of the substitution pat-
tern; however, in situ scanning tunneling
microscopy at the solid-fluid interface
between an organic solution of the HBC
derivative and highly oriented pyrolytic
graphite reveals different packing pat-
terns of the first adsorbed monolayer.
Keywords: aromatic hydrocarbons ´
liquid crystals ´ mesophases ´ scan-
ning tunnelling spectroscopy ´ self-
assembly
columnar axis. Using time-of-flight photoconductivity techni-
ques as well as a pulse-radiolysis time-resolved microwave
conductivity technique, it has been shown that highly ordered
columnar phases of substituted triphenylenes exhibit a high
charge carrier mobility.[7] By further increasing the size of the
aromatic core, it should be possible to obtain an even higher
charge carrier mobility. Indeed, we have recently shown, that
soluble alkyl-substituted derivatives of hexa-peri-hexabenzo-
coronene ꢀHBC)[8] ꢀ1a ± c) ex-
Introduction
Polycyclic aromatic hydrocarbons ꢀPAHs) with peripheral
substituents such as alkoxy-substituted triphenylenes[1], rufi-
gallols[2], or dibenzopyrenes[3] have been intensely studied in
recent years. They consist of flat disc-type cores surrounded
by flexible chains, which enable them to self-assemble into
columnar mesophases.[4] The packing behavior of these
discotic liquid crystals renders them well suited materials for
the study of one-dimensional transport processes such as
electrical conductivity[5] and photoconductivity[6] along the
hibit a charge carrier mobility
as high as 0.13 cm2 VsÀ1 in the
mesophase[9]Ðthe largest val-
ues determined so far for a
discotic liquid crystalline mate-
rial ꢀFigure 1).
Research toward electronics
on the scale of individual mol-
ecules can be performed by
[a] Prof. Dr. K. Müllen, Dr. S. Ito, Dr. M. Wehmeier,
Dr. J. D. Brand, Dr. C. Kübel
Max-Planck-Institute for Polymer Research
Ackermannweg 10, 55128 Mainz ꢀGermany)
Fax : ꢀ‡49)6131-379100
E-mail: müllen@mpip-mainz.mpg.de
[b] Prof. Dr. J. P. Rabe, Dr. R. Epsch
Humboldt University Berlin, Department of Physics
Invalidenstrasse 110, 10115 Berlin ꢀGermany)
Fax : ꢀ‡49)30-20937632
investigating highly ordered
monomolecular adsorbate lay-
ers of PAHs. Using the scanning
tunneling microscope, single
Figure 1. Hexaalkyl-substitut-
ed hexa-peri-hexabenzocoro-
nenes 1a ± c.
E-mail: rabe@physik.hu-berlin.de
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J. P. Rabe, K. Müllen et al.
FULL PAPER
molecules in these two-dimensional patterns can be visualized
with submolecular resolution.[10±14] At the same time, infor-
mation on their electronic properties can be obtained. For
instance, it was possible to measure different current-voltage
curves for the aromatic and aliphatic moieties of hexaalkyl-
substituted hexa-peri-hexabenzocoronenes.[13]
It is tempting to subject HBCs to functionalization and
investigate the influence of the molecular structure upon
supramolecular ordering in both two-dimensional- and three-
dimensional motives. In order to provide suitable systems, we
have therefore synthesized HBC derivatives with electron
donating and electron withdrawing substituents. HBCs with
electron donating substituents provide a further prospect for
better photoconductive properties in the discotic meso-
phase.[7]
Our recently published synthetic concept to obtain alkyl-
substituted HBCs[8] consisted of an oxidative cyclodehydro-
genation of substituted hexaphenylbenzenes with aluminum
chloride/copperꢀii) trifluoromethanesulphonate ꢀCu-triflate)
in carbon disulfide. However, applying these conditions and
various other oxidizing agents[15] to hexaphenylbenzenes with
substituents other than alkyl groups, we were not able to
obtain the desired PAHs. With ironꢀiii) chloride/nitromethane
in dichloromethane we now introduce a cyclodehydrogena-
tion system that allowed us to synthesize bromo-substituted
hexa-peri-hexabenzocoronenes 2a ± c ꢀFigure 2).
solvents, flexible, solubilizing
substituents are a prerequisite
for any chemical transforma-
tions at the aromatic core.
Originally, we synthesized
hexaalkyl substituted hexa-
peri-hexabenzocoronenes[8]
starting from dialkyldiphenyl-
acetylenes 3a ꢀScheme 1). Af-
ter a dicobalt octacarbonyl cat-
alyzed cyclotrimerization, the
resulting hexaalkyl hexaphenyl-
benzenes 4a could be cyclode-
hydrogenated with aluminum
chloride/copper triflate in car-
bon disulfide to give the desired
PAHs 1.
This synthetic concept allows
only identical functionalization
of all six phenyl substituents of
the hexaphenylbenzene, or
product mixtures have to be
tolerated.[17] In order to get
selectively functionalized prod-
ucts we turned to a different
synthetic approach. This was
Scheme 1. Synthesis of hexa-
alkyl-substituted
hexa-peri-
hexabenzocoronenes 1. a) Co2-
ꢀCO)8, dioxane, reflux ꢀ92%);
b) AlCl3, CuꢀOSO2CF3)2, CS2,
RTꢀ49%).
accomplished by [4 ‡ 2]-cycloaddition of suitably substituted
diphenylacetylenes and 2,3,4,5-tetraarylcyclopenta-2,4-dien-
1-ones to afford well defined hexaphenylbenzene deriva-
tives[18] in excellent yields. With the right combination of
diphenylacetylene and tetraarylcyclopentadienone, the inter-
molecular Diels ± Alder reaction followed by a cyclodehydro-
genation offers the possibility of synthesizing a variety of
functionalized hexa-peri-hexabenzocoronenes for spectro-
scopic and electronic investigations. In a first attempt, we
synthesized the pentaalkyl-substituted hexabenzocoronene
1d, which we planned to modify at the free position at the
HBC core by typical aromatic substitution reactions. How-
ever, neither nitration, bromination, nor Friedel ± Crafts
reactions gave the desired products. During nitration and
Friedel ± Crafts, reactions decomposition took place due to
the strongly acidic conditions. Attempts to brominate 1d
resulted in inseparable mixtures of multiply brominated
compounds. We then decided to build up several bromo-
substituted hexabenzocoronenes by cyclodehydrogenation of
the corresponding bromo-sub-
Figure 2. Bromo-substituted hexa-peri-hexabenzocoronenes 2a ± c.
Having at hand compounds 2a ± c, it is possible to exchange
the bromo substituents at the aromatic core to introduce
various electron donating and electron withdrawing groups.
The liquid crystalline behavior of the new compounds is
presented, and their self-assembly in ordered molecular
patterns in monolayers at solid ± fluid interfaces is investigat-
ed by scanning tunneling techniques.
stituted hexaphenylbenzenes.
The necessary bromo-hexaphe-
nylbenzene derivatives were
synthesized by Diels ± Alder re-
actions of suitably substituted
Results
diphenylacetylene and tetraar-
ylcyclopentadienone building
Synthesis
blocks in a straightforward re-
action sequences.
4,4'-Dibromodiphenylacety-
lene ꢀ3b) was synthesized ac-
cording to a literature proce-
dure.[19] Attempts to prepare
From a symmetry point of view, we recently considered the
hexagonal structure of 1 as ªsuperbenzeneº[16] and analogous
larger structures as ºsupernaphthaleneº and ªsupertripheny-
leneº. Here, we will try to create a benzene-like chemistry for
the ºsuperbenzeneº-molecule. Since the parent hexa-peri-
hexabenzocoronene ꢀHBC) is insoluble in most common
Figure 3. Pentaalkyl-substitut-
ed hexa-peri-hexabenzocoro-
nene ꢀ1d).
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Hexa-peri-hexabenzocoronenes
4327±4342
the 4,4'-didodecyldiphenylacetylene ꢀ3a) from 3b under
Kumada[20] coupling conditions were unsuccessful, so we
synthesized 3a via a different reaction path ꢀScheme 2). This
was achieved by introducing alkyl groups to 4,4'-dibromo-
stilbene ꢀ5a)[21] in a quantitative Kumada coupling reaction
with NiCl2ꢀdppp) as catalyst. After bromination of the
stilbene double bond, the resulting precursor 6 could be
transformed quantitatively into the desired dialkyldiphenyl-
acetylene 3a by treatment with potassium tert-butanolate in
refluxing tert-butanol ꢀScheme 2).
Scheme 2. Synthesis of dialkyl-substituted diphenylacetylene 3a.
a) NiCl2ꢀdppp), Et2O ꢀ92%); Br2, CCl4, RTꢀ90%); c) tert-butanol,
potassium tert-butanolate, reflux ꢀ69%).
Scheme 4. Synthesis of substituted tetraarylcyclopentadienones 14a,b.
a) FeꢀCO)5, KOH, benzyltriethylammoniumchloride, CH2Cl2, H2O, reflux
ꢀ47 ± 53%); b) I2, DMSO, 1558C ꢀ69%); c) KOH, EtOH, reflux, 5 min
ꢀ43 ± 60%).
Scheme 3. Synthesis of unsymmetrically substituted diphenylacetylene 3c.
a) Pd0, Et3N, trimethylsilyacetylene, 658C ꢀ89%); b) THF, potassium
0
fluoride, RTꢀ95%); c) Pd , Et3N, 4-bromo-iodobenzene, 658C ꢀ74%).
Synthesis of 4-bromo-4'-dodecyldiphenylacetylene ꢀ3c) was
accomplished by a sequence of Sonogashira coupling reac-
tions[22] ꢀScheme 3). First, 4-bromododecylbenzene ꢀ7)[23] was
coupled with trimethylsilylacetylene to give 8 in 89% yield.
After quantitative deprotection of the triple bond with
potassium fluoride in DMF,[24] alkyne 9 was coupled with
4-bromo-iodobenzene yielding the unsymmetrically substitut-
ed building block 3c ꢀ74%). Oxidation of the above
synthesized 4,4'-dodecyldiphenylacetylene ꢀ3a) with I2 in
DMSO[25] at 1558C resulted in the 1,2-diketone 11 and our
improved synthesis of 1,3-diarylacetones 13a,b[26] enabled the
synthesis of the substituted tetraarylcyclopentadienones
14a,b ꢀScheme 4).[27]
Scheme 5. Synthesis of bromo-substituted hexaphenylbenzenes 4b,c.
a) Diphenylether, reflux ꢀ71 ± 76%).
Two-fold Knoevenagel condensation of 11 and 13a,b in
refluxing ethanol yielded the tetraarylcyclopentadienone
building blocks 14a,b ꢀ48 ± 67%). Suitable combinations of
the synthesized diphenylacetylenes and tetraarylcyclopenta-
dienones were then reacted in a [4 ‡ 2]-cycloaddition in
refluxing diphenylether to give hexaphenylbenzenes 4b ± d in
good yields ꢀ70 ± 75%).
Thus, 4b and 4c were available by reaction of tetraꢀ4'-
alkylaryl)cyclopentadienone 14a with monobromo-3c and
dibromodiphenylacetylene ꢀ3b), respectively ꢀScheme 5),
whereas compound 4d was synthesized with 3,4-bisꢀ4'-alkyl-
aryl)-2,5-bisꢀ4'-bromoaryl)cyclopentadienoneꢀ14b) and dia-
lkyldiphenylacetylene 3a ꢀScheme 6). All hexaphenylben-
zenes could be unambiguously characterized by NMR spec-
troscopy, mass spectrometry and elemental analysis.
As mentioned in the introduction, we attempted to trans-
form the functionalized hexaphenylbenzenes into the corre-
sponding hexa-peri-hexabenzocoronene derivatives by apply-
ing the cyclodehydrogenation conditions ꢀAlCl3/Cu-triflate in
CS2) suitable for synthesizing hexaalkyl-substituted deriva-
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J. P. Rabe, K. Müllen et al.
FULL PAPER
Scheme 6. Synthesis of bromo-substituted hexaphenylbenzene 4d. a) Di-
phenylether, reflux ꢀ74%).
Scheme 7. Synthesis of bromo-substituted HBCs 2a ± c. a) FeCl3, CH3-
NO2, CH2Cl2, RTꢀ87 ± 93%).
tives.[8] However, reaction of the bromo-substituted hexaphe-
nylbenzenes 4b ± d under these oxidative conditions failed to
yield the desired products. According to mass spectrometry,
only partially cyclized products were formed. Also, treatment
of the HBC-precursors under various other oxidative coupling
conditions that had been developed by Kovacic[28] for the
synthesis of poly-para-phenylenes from benzene did not lead
to the desired HBC derivatives in high yields. Addition of
ironꢀiii)chloride to a solution of the precursor in dichloro-
methane,[29] led to unseparable mixtures of hexa-peri-hexa-
benzocoronene derivatives and chlorinated by-products. The
formation of the undesired by-products could be successfully
suppressed by dissolving the ironꢀiii)chloride in nitromethane
before adding it to the reaction mixture and by purging out
HCl evolving during the reaction. Using these improved
conditions ꢀScheme 7), products 2a ± c were isolated in
excellent yield after quenching the reaction with methanol
ꢀ90 ± 95%).
We planned to introduce different electron donating and
electron withdrawing substituents at the aromatic core using
the monobromo-substituted HBC 2a. Lithiation with n-
butyllithium in tetrahydrofuran followed by quenching of
the lithiated species with various electrophiles did not yield
the desired products but resulted in the dehalogenated PAH
in up to 80% yield. However, by using Pd-catalyzed coupling
reactions, we were able to introduce various substituents
ꢀScheme 8 and Scheme 9). It was possible to cross-couple
primary and secondary amines with the monobromo-HBC 2a
under catalysis with Pd2ꢀdba)3 and BINAP in the presence of
sodium tert-butanolate.[30] With this method, we obtained
undecylamino-HBCs 15a,b,c and piperidino-HBC 16 in 80%
yield ꢀ100% conversion).[31] By analogy to this reaction, we
tried to synthesize ether derivatives by similar cross-coupling
of alcohols and 2a with the above mentioned catalyst
system.[32] In contrast to the previous synthesis, the alcohols
did not react at all or the conversion was very low. The
Scheme 8. Synthesis of mono functionalized HBC derivatives. a) 15a:
undecylamine, sodium tert-butoxide, ꢀR)-BINAP, Pd0, toluene, 808C, 4 h
ꢀ74%); 16: piperidine, sodium tert-butoxide, ꢀR)-BINAP, Pd0, toluene,
808C, 4 h ꢀ78%); b) cyclohexanol, NaH, ꢀR)-BINAP, Pd0, toluene, 808C,
2 h ꢀ17%), c) CO, methanol, PdꢀPPh3)2, PPh3, triethylamine, THF, 1008C,
5 d ꢀ62%), d) CuCN, NMP, 1958C, 20 h ꢀ61%).
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Hexa-peri-hexabenzocoronenes
4327±4342
dependent as was observed for 1a before ꢀsee Experimental
Section). This is due to the strong p ± p-interaction in
aggregates which are present even at low concentrations.
Characterization of the mesophase behavior
The mesogenic properties of compounds 1, 2, and 15 ± 19 were
investigated using optical microscopy, DSC, and X-ray
diffraction. A summary of the thermal behavior deduced
from these techniques is shown in Tables 1, 2.
DSC Study: At room temperature all compounds are solids,
but they exhibit a liquid crystalline phase at slightly elevated
temperatures. Compounds 1, 2, 15a, and 16 ± 19 form a single
mesophase over a broad temperature range. One strongly
endothermic peak with a characteristic enthalpic value of
about 40 ± 50 JgÀ1 was observed during the heating cycle and
assigned to the solid-to-mesophase transition. In some cases
additional phase transitions could be identified at low
temperatures by small enthalpy changes. These phases are,
presumably, due to polymorphism in the crystalline or plastic
crystalline state.
The transition from the mesophase into the isotropic liquid
is accompanied by a small change in enthalpy of about 5 J gÀ1,
but was measured only exceptionally, since it occurs at
temperatures above 4008C, where decomposition slowly
starts. At temperatures below 3008C, where no decomposition
was observed, compounds 1, 2, 15a, and 16 ± 19 exhibit
reversible phase transitions.[36] However, these HBC deriva-
tives show strong supercooling ꢀup to 608C) and, in some
cases, tend to recrystallize only partially.
The bis-amines 15b and 15c exhibit a slightly different
phase behavior. Even though DSC shows only one phase
transition into a mesophase, an additional phase was observed
by X-ray diffraction for both bis-amines 15b and 15c. In case
of 15c, an approximately rectangular columnar phase was
identified, which is stable between 95 and 1158C. For
compound 15b a phase was observed which is only stable in
a small temperature range around 908C before the transition
into the hexagonal discotic mesophase occurs. This phase was
repeatedly observed upon heating, but could not be detected
upon cooling. The reason for the different phase behavior of
compounds 15b and 15c compared with 1, 2, 15a, or 16 ± 19 is
not yet well understood, but we expect that hydrogen bonding
between NH groups, resulting in a stronger coupling of the
disk-like molecules, plays a crucial role.
Scheme 9. Synthesis of bis-functionalized HBC derivatives. a) Undecyl-
amine, sodium tert-butoxide, ꢀR)-BINAP, Pd0, toluene, 808C, 4 h ꢀ75%);
b) CO, methanol, [PdꢀPPh3)2Cl2], PPh3, triethylamine, THF, 1008C, 5 d
ꢀ62%).
primary alcohol undecanol did not give the corresponding
ether derivative but afforded the dehalogenated PAH in 78%
yield, whereas the secondary alcohol cyclohexanol cross-
coupled with 2a to give the cyclohexyl ether 17 in low yield
ꢀ17%). Besides these derivatives with electron donating
substituents, it was also possible to introduce electron with-
drawing substituents by a Pd-catalyzed reaction. In a PdII
catalyzed carbonylation reaction with CO and methanol
under high pressure,[33] the methyl esters 18a and 18b were
synthesized in 60% yield. With the cyano-HBC 19a, another
derivative with a strongly withdrawing substituent could be
obtained in similar yield ꢀ61%) by a Rosenmund ± von
Braun[34] reaction with CuCN in N-methylpyrrolidone.
All attempts to obtain analytically pure diester 18c and the
dicyano-HBCs 19b and 19c, applying the same reaction
conditions as described above, were unsuccessful. Even
though, the reactions yielded the desired products, it was
not possible to separate them from the starting material and
side products.
Optical microscopy study: To study the thermal behavior of
the compounds 1, 2, and 15 ± 19 by polarization microscopy a
drop cast film was prepared from dichloromethane solution.
Upon heating under nitrogen the compounds underwent a
phase transition into a highly viscous phase, which exhibited a
much stronger birefringence than the initial, partially crystal-
line material. The textures observed at temperatures up to
about 2308C were not characteristic of a particular super-
structure, but upon further heating to a maximum of 4208C
growing domains with textures typical for a columnar
mesophase[1, 37] were observed for many compounds without
noticeable decomposition. Those textures did not change
The new derivatives could be unambiguously characterized
by NMR spectroscopy, mass spectrometry, IR spectroscopy,
UV/Vis spectroscopy,[35] and elemental analysis. The NMR
spectra show the expected number of signals, but the chemical
shifts in the 1H-NMR spectra are strongly concentration
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J. P. Rabe, K. Müllen et al.
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Table 1. Optical, thermal, and thermodynamic data of compounds1, 2, and
15 ± 19 ꢀC ˆ crystal, LC ˆ liquid crystal, Colho ˆ ordered hexagonal colum-
nar mesophase, I ˆ isotropic liquid) for the second heating.
Compound
Transition
T [8C]
DH [JgÀ1
]
1b
C-Colho
Colho-I
C-Colho
Colho-I
C-Colho
Colho-I
C-Colho
Colho-I
C-Colho
Colho-I
C-Colho
Colho-I
C-LC
LC-Colho
Colho-I
C-Colr
Colr-Colho
Colho-I
C-Colho
Colho-I
C-LC
106.5
60.6
5.7
50.8
417
124.4
412[a]
74.1
> 420[a]
59.3
1d
2a
46.6
40.7
79.1
40.1
51.8
2b
> 420[a]
104.3
> 420[a,b]
89.4
2c
15a
15b
410 ± 425[a]
89.7
ꢀ 95[c]
> 420[a]
95.6
15c
44.9
ꢀ 115[c]
360 ± 405[a]
16
101.7
> 420
40.3
39.2
47.3
41.2
31.5
17
95.9
404[a,b]
82.6
LC-I
18a
18b
19a
C-Colho
Colho-I
C-Colho
Colho-I
C-LC
> 420[a]
83.0
380 ± 400[a,b]
77.3
> 420[a]
LC-I
[a] A transition observed by optical microscopy. [b] Decomposition
noticeable during optical microscopy. [c] Transition observed by X-ray
diffraction.
Figure 4. Optical textures of the hexagonal discotic mesophase of 1d
observed under polarized light ꢀcrossed polarizers). Top: 4088C ꢀheating).
Bottom: 3808C ꢀcooling), scale ˆ 100 mm.
during cooling until the sample recrystallized, which could be
observed as fracturing of the mesophase texture in some cases.
For those compounds ꢀ1d, 15a, 15c, 17) with clearing points
below 4208C even fast cooling ꢀ15 KminÀ1) of the optically
isotropic liquid gave well-developed birefringent domains
typical for columnar mesophases, but often only after
pronounced supercooling of the optically isotropic liquid
phase. The observed textures include ribbon- or fan-like as
well as dendritic domains: Figure 4 shows some typical
examples.
X-ray Diffraction study: The structure of the different phases
of compounds 1, 2, and 15 ± 19 were examined by temperature
dependent X-ray diffraction. At temperatures up to the first
highly endothermic phase transition the diffraction patterns,
in combination with the mechanical behavior, indicated the
presence of a crystalline phase, however, the alkyl chains were
not well ordered in most cases.
Figure 5. X-ray diffraction pattern of 2a at 1708C.
Above the melting point, the X-ray diffraction patterns of
all HBC derivatives described in this paper yielded a set of
peaks which are characteristic of a hexagonal columnar
mesophase ꢀFigure 5).[8, 38] Three to five reflections are
observed at low angles with the first one being much more
to 31 Š. In addition to these reflections a broad halo with its
center around 4.7 Š was observed, which is associated to the
liquid-like correlation between aliphatic chains.[39] The 001-
reflection at about 3.5 ± 3.6 Š indicates the periodic stacking
of the molecular cores in the columns.[40]
The liquid crystalline samples could be easily aligned by
mechanical shearing, for example by extrusion to a fiber. In
case of compounds 1c and 2a, the fibers recrystallized
intense than the other ones. Their reciprocal spacings follow
p p p p
the ratio 1: 3: 4: 7: 9, and they can be indexed as 10-, 11-,
20-, 21-, and 30 reflections of a quasi two-dimensional
hexagonal lattice with intercolumnar distances of about 26
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Chem. Eur. J. 2000, 6, No. 23

Hexa-peri-hexabenzocoronenes
4327±4342
Table 2. Lattice spacings obtained by X-ray diffraction for the mesophase
of compounds 1, 2, and 15 ± 18 at 1708C.
stable for more than three months at room temperature. The
diffraction pattern of this fiber ꢀFigure 6) proved the orienta-
tion of the columns to be along the fiber axis.
Com-
pound
h
k
l
d [Š] Lattice
constant [Š] [g cmÀ3
Calcd density[a]
VCH
2
]
[Š3][b]
1b
1c
1d
2a
2b
1
1
2
0
1
1
2
0
1
1
2
0
1
1
2
0
1
1
2
2
3
0
1
1
2
0
1
1
2
0
1
1
2
0
1
1
2
0
1
1
2
0
1
1
2
3
0
1
1
2
0
0
1
0
0
0
1
0
0
0
1
0
0
0
1
0
0
0
1
0
1
0
0
0
1
0
0
0
1
0
0
0
1
0
0
0
1
0
0
0
1
0
0
0
1
0
0
0
0
1
0
0
0
0
0
1
0
0
0
1
0
0
0
1
0
0
0
1
0
0
0
0
0
1
0
0
0
1
0
0
0
1
0
0
0
1
0
0
0
1
0
0
0
1
0
0
0
0
1
0
0
0
1
25.6
14.8
12.3
a ˆ 29.6
Colho 0.95
31.8
3.55 c ˆ 3.55
26.7
15.3
13.3
a ˆ 30.7
Colho 0.95
Colho 0.99
Colho 0.98
Colho 1.07
30.7
31.7
33.8
34.5
3.67 c ˆ 3.67
23.3
13.6
11.2
a ˆ 27.2
3.60 c ˆ 3.60
24.5
14.2
12.3
a ˆ 28.3
3.54 c ˆ 3.54
22.8
a ˆ 26.3
13.2
11.4
8.7
7.7
3.52 c ˆ 3.52
Figure 6. X-ray diffraction pattern of an extruded fiber of 2b at room
temperature ꢀbeam direction normal to fiber axis).
2c
15a
15b
15c
16
22.7
13.1
11.4
a ˆ 26.2
Colho 1.08
Colho 1.02
Colho 1.00
Colho 1.03
Colho 0.94
Colho 0.93
34.0
29.1
30.5
29.3
32.7
33.9
3.51 c ˆ 3.51
Figure 7 shows the X-ray diffraction pattern of compound
15c at 1108C. The first three reflections can be indexed in
agreement with an approximately rectangular structure with
a ˆ 33.7 Š, but the split reflection at about 6.58 indicates a
small distortion from a rectangular geometry. The reflection
24.4
14.2
12.1
a ˆ 28.1
c ˆ
24.9
14.4
12.5
a ˆ 28.7
3.62 c ˆ 3.62
24.3
14.1
12.1
a ˆ 28.0
3.68 c ˆ 3.68
25.1
14.5
12.5
a ˆ 29.0
3.56 c ˆ 3.56
18a
24.7
a ˆ 28.6
14.4
12.4
8.3
3.59 c ˆ 3.59
18b[c]
24.0
13.7
12.0
a ˆ 27.7
Colho 0.94
36.1
Figure 7. X-ray diffraction pattern of compound 15c at 1108C.
3.51 c ˆ 3.51
at 4.67 Š is indexed as a 001-reflection, indicating the stacking
periodicity. Assuming a center-to-center distance of 3.6 Š,
this corresponds to a tilt angle of about 408 for the molecular
plane with respect to the column axis.
M=N
[a] The density was calculated using the following Equation: 1 ˆ
,
V
2
2
p
with M ˆ molecular weight, N ˆ Avogadro number, Vˆ
a c: volume
3
unit cell. [b] VCH was calculated by the following Equation VCH
ˆ
2
2
Scanning tunneling microscopy ?STM): As mentioned in the
introduction, different current-voltage characteristics through
single alkylated HBC molecules of 1b have been detected for
the aromatic and aliphatic parts,[13] and it is expected that the
functionalization of the aromatic core will influence the
packing patterns and possibly the current voltage character-
istics. The immobilization of the functionalized HBCs in two-
dimensional molecular patterns and the submolecularly
resolved scanning tunneling microscopy ꢀSTM) are also
Vmol À Vcore À Vsubst
with Vmol ˆ unit cell volume, Vcore ˆ volume of HBC
N
CH2
core ꢀ410 Š3), and Vsubst ˆ volume of varying substituents ꢀnon CH2), and
NCH ˆ number of CH2 and CH3 groups. [c] X-ray diffraction measurements
2
were done in a 2 mm capillary instead of a copper goniometer.
immediately upon cooling to room temperature, retaining the
preferential orientation, but in case of the dibromo-substi-
tuted compound 2b the hexagonal columnar mesophase was
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J. P. Rabe, K. Müllen et al.
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Table 3. Lattice constants of all described two-dimensional crystal struc-
tures of functionalized HBC.
prerequisites for the spectroscopy. Therefore, in situ STM
measurements were carried out at the solid ± fluid interface
between an organic solution containing the functionalized
HBCs ꢀ1b, 1d, 2a, and 15a ± c), and the atomically flat basal
plane of highly oriented pyrolytic graphite ꢀHOPG), follow-
ing a strategy developed some time ago.[11, 41±45]
The present investigation is concerned with the influence of
chemical modification on the two-dimensional crystal struc-
ture. In particular, how far will the replacement of an alkyl
side chain by a hydrogen atom or a bromine atom or the
insertion of amino groups into an alkyl chain modify the two-
dimensional crystal structures? The electronic characteriza-
tion of the molecules within the patterns shall be presented
elsewhere.[46]
For hexaalkyl-substituted HBC 1b two different molecular
patterns could be observed ꢀFigure 8a). Like in all STM
images of the present paper the areas of higher tunneling
current are attributed to the aromatic moiety of the mole-
cules.[47±49] Besides a rhombic lattice, which has been already
described for 1b,[13] also a two-dimensional crystal structure is
found, in which the molecules are dimerized. In Figure 8a two
Lattice type Lattice parameters
Area per molecule in nm2
1b dimer rows
a ˆ 3.40 Æ 0.17 nm
b ˆ 4.02 Æ 0.21 nm
a ˆ 768 Æ 28
6.63 Æ 0.75
x ˆ 1.64 Æ 0.17 nm
b ˆ 618 Æ 48
rhombic
a ˆ 1.88 Æ 0.09 nm
b ˆ 2.68 Æ 0.11 nm
a ˆ 808 Æ 28
4.96 Æ 0.48
6.27 Æ 0.45
1d dimer rows
a ˆ 2.89 Æ 0.11 nm
b ˆ 4.56 Æ 0.08 nm
a ˆ 728 Æ 38
x ˆ 1.84 Æ 0.16 nm
b ˆ 618 Æ 28
rhombic
a ˆ 1.86 Æ 0.07 nm
b ˆ 2.60 Æ 0.08 nm
a ˆ 798 Æ 38
4.75 Æ 0.37
6.17 Æ 0.30
15a
dimer rows
a ˆ 2.98 Æ 0.06 nm
b ˆ 4.29 Æ 0.08 nm
a ˆ 758 Æ 28
x ˆ 1.83 Æ 0.14 nm
b ˆ 638 Æ 58
15b dimer rows
a ˆ 2.89 Æ 0.15 nm
b ˆ 4.36 Æ 0.37 nm
a ˆ 768 Æ 48
6.11 Æ 0.97
6.10 Æ 0.57
x ˆ 1.70 Æ 0.16 nm
b ˆ 668 Æ 48
15c
2a
dimer rows
hexagonal
a ˆ 2.94 Æ 0.08 nm
b ˆ 4.39 Æ 0.23 nm
a ˆ 718 Æ 28
x ˆ 1.82 Æ 0.21 nm
b ˆ 568 Æ 48
a ˆ b ˆ 6.41 Æ 0.16 nm 5.07 Æ 0.39
a ˆ 608 Æ 2.58
c ˆ 2.70 Æ 0.16 nm
b ˆ 298 Æ 18
p ˆ 5.72 Æ 0.15 nm
g ˆ 2.75 Æ 0.12 nm
x ˆ 1.64 Æ 0.95 nm
dence between the axes of the rhombic lattice ꢀdetermined
by the positions of the aromatic cores) and the graphite
substrate.
Figure 8. a) STM image ꢀconstant height mode) of the two-dimensional
crystal structures of 1b; b) packing model of the dimer row structure of 1b;
c) packing model of the rhombic lattice of 1b.
For pentaalkyl-substituted HBC 1d also two molecular
patterns could be observed: A dimer row structure ꢀFigure 9a,
Table 3) and a rhombic lattice ꢀFigure 9c, Table 3). Similarly
to the case of 1b, discussed above, packing models have been
constructed, which are shown in Figure 9b ꢀdimer rows) and
Figure 9d ꢀrhombic lattice). Obviously, the symmetries of
both structures are identical to the ones reported for 1b.
By introducing amino groups one may expect changes of
the molecular arrangement due to hydrogen bonds between
neighboring molecules. The STM image of 15a ꢀFigure 10a)
reveals dimer rows.
domains are visible, which are separated by a wide domain
boundary, where the molecules are disordered. The domain in
the upper part of the STM image exhibits the rhombic lattice,
while in the domain in the lower part of the image the dimer
row structure is observed. The lattice constants of both
crystalline structures are given in Table 3.
The parallel orientation of all alkyl side chains along a
substrate lattice axis leads to a closely packed crystal. From
the comparison of Figure 8a with the STM images revealing
the underlying graphite lattice ꢀnot displayed) one can
determine, which axes of both two-dimensional lattices
correspond to graphite axes. Packing models have been
constructed and displayed in Figure 8b,c. The short diagonal
of the unit cell of the dimer row structure corresponds
to a graphite lattice axis, while there is no correspon-
The average area per molecule ꢀ6.17 nm2 Æ 0.30 nm2, see
[50]
Table 3) is a little larger than the calculated value
ꢀ5.69 nm2). From the experiment, the short diagonal of the
unit cell corresponds to a graphite lattice axis. Therefore, one
may expect that all alkyl chains are aligned along this axis
ꢀFigure 10b). Moreover, Figure 10b demonstrates that distan-
ces between the amino groups of neighboring molecules are
too large for intermolecular hydrogen bonds. On the other
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Hexa-peri-hexabenzocoronenes
4327±4342
Figure 10c shows quite a high number of these interstitial
molecules.
No change of the lattice constants was observed caused by
the additional molecules, but locally a closer packing is
obtained. The calculated value for a closely packed crystal
indicates that alkyl chains have to be lifted out of the
crystalline interfacial monolayer into the organic solution;
otherwise, within the monolayer there would be not enough
empty space for interstitial molecules. The analysis of all
measured STM images indicates that the additional incorpo-
ration of molecules does not initiate a phase transition to a
more closely packed crystal structure, but rather the inter-
stitials are filled statistically. The already known dimer row
structure is also the typical two-dimensional lattice for 15b
and 15c ꢀTable 3).
The symmetries of the two-dimensional crystals of the
functionalized HBCs reported so far are the same as for the
fully alkylated HBC. A different case is a bromo-substituted
HBC 2a. Figure 11 shows the STM image of 2a, which is a
Figure 9. a) STM image ꢀconstant current mode) of the dimer row
structure of 1d; b) packing model of the dimer row structure of 1d;
c) STM image ꢀconstant current mode) of the rhombic lattice of 1d;
d) packing model of the rhombic lattice of 1d.
Figure 11. STM image ꢀconstant current mode) of the hexagonal lattice of
2a.
rather complex two-dimensional lattice structure. The lattice
contains two types of molecules: molecules associated in
trimers and single molecules. The orientation of neighboring
trimers alternates.
Single molecules and trimers assemble in a supramolecular
pattern. A hexagonal lattice results ꢀTable 3), in which single
molecules fill positions in the center of an ensemble of six
trimers, while every trimer is surrounded by three single
molecules.
The positions of the bromine atoms within the two-dimen-
sional crystal structure of 2a could not be resolved. As it has
been often observed for crystals of other chloro-, bromo-, and
iodo derivatives,[51±55] halogen end groups tend to be adjacent
to each other. For that reason, it seems to be most probable
that within the two-dimensional lattice of 2a bromine atoms
are located in the center of trimers ꢀsee Discussion).
Figure 10. a) STM image ꢀconstant height mode) of the dimer row
structure of 15a; b) packing model of the dimer row structure of 15a;
c) STM image ꢀconstant height mode) of the dimer row structure of 15a,
with interstitials ꢀmarked with x).
Discussion
hand, hydrogen bonds cannot be completely excluded, given
the error of the unit cell data.
The described lattice of dimer rows is the only molecular
pattern observed for 15a. Often additional molecules are
located between the dimer rows in interstitial positions.
It appears that mono- and dibromo derivatives of HBC 2a,b,c
are readily available via the Diels ± Alder synthesis of
adequately substituted hexaphenylbenzenes and their subse-
quent cyclodehydrogenation. The chemical transformation of
the bromo substituted HBC derivatives is limited for several
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J. P. Rabe, K. Müllen et al.
FULL PAPER
reasons. The molecules are unstable under highly acidic
conditions and show a relatively low solubility in organic
solvents at room temperature. This is especially true for the
dibromo compound 2c, which has an even lower solubility
than 2a or 2b. Further problems arise in the purification
process of these extremely large polycyclic aromatic hydro-
carbons. It is often not possible to separate different HBC
derivatives on a chromatography column or to get analytically
pure samples by recrystallization, due to the long alkyl tails.
Therefore, it is necessary to have clean reactions with a high
conversion, especially in case of dibromo-HBCs 2b and 2c.
The synthesis of 15, 18, and 19 may serve as typical examples.
It is possible to react the ªsuperbenzeneº HBC-molecule
under various conditions known from benzene chemistry. In
contrast to phthalocyanines, where selectively functionalized
derivatives are hard to obtain, the HBCs allow a direct
correlation of the varying substitution pattern with the
packing behavior and the electronic properties.
It becomes obvious from the STM image of hexaalkyl HBC
1b that the alkyl side chains are located in the area of lower
tunneling current. As with all other STM images presented in
this paper, they could not be molecularly resolved, indicating
a high conformational mobility at room temperature. How-
ever, on graphite the alkyl side chains tend to align along a
substrate lattice axis, as already described for many other
alkylated molecules studied with STM.[11, 14, 59]
Noteworthy, the dimer row structure ꢀFigure 8b) reveals
empty space in the two-dimensional arrangement of the
molecules of 1b. Correspondingly, the area per molecule
determined by the STM experiment ꢀAdr ˆ 6.63 nm2 Æ
0.75 nm2) is significantly larger than the calculated value for
closely packed molecules ꢀAtheor ˆ 5.67 nm2) given by the
van der Waals contour of the flat lying molecules.[50] The
empty space is presumably filled with solvent. The rhombic
lattice ꢀFigure 8c) on the other hand, is closely packed ꢀArh ˆ
4.96 nm2 Æ 0.48 nm2). Since crystals generally tend to be
closely packed, the average area per molecule may be used
as a means to estimate the relative stability of both crystals:
The denser packing of molecules within the rhombic lattice
indicates its higher stability.[60] Thus, it is not surprising that
with time the denser and more stable rhombic lattice is the
favored two-dimensional crystal structure of 1b molecules.
The dimer row structure and rhombic lattice of 1d were
found to coexist for a long time ꢀFigures 9a ± d). Unfortu-
nately, the phase transition between both crystal structures
could not be observed in situ in the STM, probably because of
the limited measuring time.[61] The area which one 1d flat
lying molecule needs within the rhombic lattice ꢀArh ˆ
4.75 nm2 Æ 0.37 nm2), differs substantially from the dimer
row case ꢀAdr ˆ 6.27 nm2 Æ 0.45 nm2). The theoretical value
for closely packed molecules of 1d ꢀAtheor ˆ 4.99 nm2), as
calculated from the van der Waals contour of flat flying
molecules,[50] fits well with Arh. Thus, the rhombic lattice
structure has to be considered as the most stable crystalline
modification of 1d ꢀas already demonstrated for 1b). Based
on this assumption the less closely packed dimer row structure
may be a metastable preadsorbate.
The crystal symmetries of 1d are unchanged in comparison
with those of 1b. This is not obvious, since the symmetry of the
free molecules is reduced by the chemical modification, and
new crystal symmetries might be anticipated. The absence of
additional intermolecular forces may explain why the sub-
stitution of an alkyl chain by a simple hydrogen atom does not
entail any significant changes of crystal symmetry. The present
investigation of crystal structures of 1b and 1d indicates that
stronger chemical modifications are necessary to assemble
different stable molecular patterns.
The insertion of NH functionality into the alkyl chains leads
to a stabilization of the dimer row structure when comparing
compounds 15 and 1b. The failure to observe a different
packing when varying both number and position of functional
groups indicates that the two-dimensional crystal symmetry is
probably more determined by requirements of dense packing
than by additional intermolecular forces such as, for example
hydrogen bonding.
X-ray diffraction of all HBC derivatives described herein
reveals the formation of hexagonal columnar mesophases with
the exception of 15c which exhibits an approximately rectan-
gular structure. The density of the substituted HBCs, calculated
from the X-ray diffraction data, is typically on the order of
0.95 ± 1.0 gcmÀ3 as is expected for these kinds of compounds.
Only compounds 2b and 2c have a higher density of about
1.07 gcmÀ3, presumably due to the heavy bromo substituents.
3
The calculated volume of a CH2 group is on average 31.4 Š
for the pure hydrocarbons, a relatively large, but still typical
value in discotic mesophases.[56, 57] On substituting the alkyl
chains by a short but bulky group ꢀe.g., bromo or methylester)
the calculated volume per CH2 group increases to about 33 ±
3
35 Š with this effect being most pronounced for the ortho
disubstituted hexa-peri-hexabenzocoronene derivatives. One
explanation for this observation is the flexibility of the alkyl
chains which does not allow the complete filling of the space
around the bulky substituents, thus leaving a small free
volume in the periphery of these groups.
We conclude that the different substituents in HBC
derivatives induce only small differences in the mesophase
structure and stability. This is in contrast to observations made
for triphenylenes where the mesophase stability is very
sensitive towards different substituents or substitution pat-
terns.[58] An explanation for the different properties of
substituted HBCs compared with triphenylenes is the stronger
p ± p interaction and the larger size of the aromatic core in
case of HBC, which stabilizes the mesophase dramatically and
allows for the incorporation of different substituents without
losing mesomorphic properties.
While transitions from parent HBCs 1a,b,c to their chemi-
cally functionalized analogues does not cause significant
changes of the liquid crystalline phases, STM studies reveal
profound changes of the resulting monomolecular adsorbate
layers on HOPG surfaces. It is of key importance to carefully
follow the relation between molecular structures and their
two-dimensional patterns on substrates which may serve as
anchoring layers in devices. While organic chemistry has
accumulated a vast number of three-dimensional crystal
structures, the study of two-dimensional crystals is still in its
infancy.
A completely different situation is encountered for the
monolayer of the bromo-substituted HBC 2a because one
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Hexa-peri-hexabenzocoronenes
4327±4342
visualizes patterns coexisting of both trimeric assemblies and
single molecules. The proximity of bromo end groups and the
formation of trimers could be caused by attractive interac-
tions[62±65] between bromine atoms of neighboring molecules.
Close intermolecular contacts between more than two halo-
gen groups as described in the present case for 2a have been
reported for many crystals,[54, 62, 66, 67] and triangular arrange-
ments of halogen end groups are known, for example for 1,4-
dichloro-benzene.[67] In general, two types of attractive
interactions may be considered. Dispersion forces[62] can be
responsible for the formation of crystalline structures where
the halogen atoms ꢀexcept fluorine)[55] are close to each other.
In this case the intermolecular distances are determined by
the sum of van der Waals radii of interacting atoms. The
reason for halogen ± halogen intermolecular contacts, which
are shorter than expected from the van der Waals radius, has
been controversially discussed in the literature. Price[62] and
Nyburg[63] explain the decreased intermolecular distances
between halogen end groups by an anisotropic model for the
repulsion term. However, Desiraju[64] and Parthasarathy[65]
conclude from angle preferences of intermolecular forces
around halogen atoms that specific attractive interactions
exist, which have been interpreted, for example as ªdonor±
acceptorº interactions, ªcharge-transferº interactions or ªin-
cipient electrophilic and nucleophilic attackº. Assuming in a
model treatment of the triangular arrangement of 2a that the
bromine atoms point toward the trimer center one estimates a
distance of the aromatic cores of 1.64 nm. This distance agrees
very well with the experimental value of 1.6 nm Æ 0.1 nm.
However, owing to the considerable error of the calculated
distance one cannot decide on whether the distances are
shorter than van der Waals type contacts ꢀreduced van der
Waals radii by 20% are within the error).
interact strongly and thereby induce a hexagonal super-
structure of six trimers and a single molecule. A similar
superstructure could not be observed in the bulk mesophase.
The mesophases of the HBC derivatives are very stable
with respect to variation of the substitution pattern. At high
temperatures an ordered hexagonal columnar mesophase is
observed. This might be due to the high temperature
necessary for reaching the mesophase, which induces a high
mobility of the molecules that competes with specific
intermolecular forces such as the bromine ± bromine inter-
action. On the other hand, the change from two-dimensional
to three-dimensional may also be important bringing addi-
tional intermolecular forces into play. Noteworthy, while the
amino groups in 15 induce only a slightly changed packing
behavior in the two-dimensional crystals, these compounds
were the only ones exhibiting an additional mesophase
structure below the transition to the hexagonal columnar
phase. We attribute this to hydrogen bonding between NH
groups in the bulk mesophase.
In summary, the work presented proves the feasibility of
ªHBC-chemistryº. The structural characterization gives first
indications how the substitution of the aromatic core affects
two-dimensional and three-dimensional ordering. Further-
more, gathering knowledge on the formation of monomolec-
ular adsorbate layers and, in particular, correlating molecular
structure and the packing mode in two-dimensional crystals
are important steps toward molecular electronics. Subsequent
studies by scanning tunneling spectroscopy can then detect an
influence on the current voltage curve of the aromatic core
upon a change of its electron density.
Experimental Section
STM procedure
Conclusion
In situ STM images were obtained at the interface between the basal plane
of highly oriented pyrolytic graphite ꢀHOPG, Union Carbide, quality ZYB)
and a diluted solution of the functionalized HBCs in 1,2,4-trichlorobenzene
ꢀc ˆ 10À4 mollÀ1), following an experimental procedure reported else-
where.[11, 41] Experiments were performed at room temperature with an in-
house built microscope, which is based on the ªBeetleº type STM[68, 69] and
Omicron controls ꢀCPU-3CE, SPM software version 2.1). Both electro-
chemically etched ꢀ2n KOH‡6n KCN) and mechanically cut Pt/Ir ꢀ80:20)
tips were used. Typical operation conditions for imaging the graphite lattice
were negative sample bias ꢀ30 ± 200 mV), tunneling currents around 0.2 nA
and scan rates of 30 Hz per line.
We have presented a new method to synthesize unsymmetri-
cally substituted hexa-peri-hexabenzocoronenes by oxidative
cyclodehydrogenation of suitable hexaphenylbenzene deriv-
atives with ironꢀiii)chloride in nitromethane, which tolerates
bromine functions at the aromatic core. These bromo groups
enable benzene-like substitution reactions for hexabenzocor-
onene, even though the reactions are limited due to the
solubility of the HBC and the more demanding purification
from similar by-products. Nevertheless, we were able to
synthesize HBCs with several electron donating or electron
withdrawing groups ꢀScheme 8 and 9).
These new hexa-peri-hexabenzocoronene derivatives self-
assemble in the bulk as well as at the solid ± fluid interface
between an organic solution and HOPG. In situ scanning
tunneling microscopy shows the influence of the substituents
on the molecular packing in a two-dimensional crystal.
Interestingly, the molecular symmetry is not determining the
packing pattern. The hexaalkyl HBC 1b exhibits the same two
typical motives as the pentaalkyl HBC 1d, namely a rhombic
and a ªdimer rowº structure. Introducing a bromo function at
the aromatic core causes a completely different packing
pattern. The bromine groups of different molecules seem to
First, STM images of the freshly cleaved substrate in pure solvent or air
were recorded in ªconstant heightº mode to calibrate the scanner for the
currently used tip. Afterwards a drop of the organic solution containing the
HBC was deposited on the graphite surface. Often spontaneous crystal-
lization was observed; otherwise the crystallization was induced by an
external voltage pulse between sample and tip ꢀÀꢀ2 ± 4) V). The two-
dimensional crystals of physisorbed molecules were studied in the
ªconstant current modeº as well as in the ªconstant height modeº under
ambient conditions ꢀnegative sample bias: 1.0 ± 1.8 V, tunneling current:
0.1 ± 0.6 nA, scan rates: 30 Hz per line). After imaging of the molecular
pattern the bias voltage was reduced to 30 ± 200 mV, which allows to
characterize the underlying graphite lattice.[45, 70] Based on this method one
may determine the relative orientation between adsorbate and substrate
lattices.
General methods
1H-NMR and 13C-NMR spectra were recorded in CDCl3, CDCl3/CS2 1:1,
and C2D2Cl4 on a Varian Gemini 200, Bruker DPX 250, Bruker AMX300,
Chem. Eur. J. 2000, 6, No. 23
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4337

J. P. Rabe, K. Müllen et al.
FULL PAPER
and Bruker DRX500 with use of the solvent proton or carbon signal as
internal standard. Melting points were determined on a Büchi hot stage
apparatus and are uncorrected. Infrared spectra were recorded on a Nicolet
FT-IR 320 spectrophotometer as KBr pellets. Mass spectra were obtained
on a VG Instruments ZAB 2-SE-FPD by using FD. Elemental analysis
were carried out on a Foss Heraeus Vario EL.
solution and dried ꢀMgSO4). After evaporation of the solvent the crude
product was recrystallized from toluene to afford 4,4'-didodecyldiphenyl-
acetylene ꢀ55 g, 69%): M.p. 588C; 1H NMR ꢀ300 MHz, CDCl3): d ˆ 7.40 ꢀd,
J ˆ 8.4 Hz, 4H), 7.12 ꢀd, J ˆ 8.4 Hz, 4H), 2.58 ꢀt, J ˆ 7.2 Hz, 4H), 1.6 ± 1.2
ꢀm, 40H), 0.86 ꢀd, J ˆ 7.6 Hz, 6H); 13C NMR ꢀ75 MHz, CDCl3): d ˆ 143.6,
131.8, 128.8, 121.0, 89.3, 36.3, 36.2, 31.6, 30.0, 29.8, 29.8, 29.7, 29.6, 23.1, 14.5;
‡
FD-MS: m/z ꢀ%): 514.6 [M] ꢀ100); anal. calcd ꢀ%) for C38H58: C 88.65, H
11.35; found: C 88.51, H 11.33.
Differential scanning calorimetry ꢀDSC) was measured on a Mettler DSC
30 with heating and cooling rates of 5 ± 108CminÀ1. First order transition
temperatures were reported as the minima of their endothermic peaks
during heating. A Zeiss Axiophot with a nitrogen flushed Linkam THM
600 hot stage was used to characterize the polarization microscopy textures
and to estimate clearing temperatures. Heating and cooling rates varied
4-Bromododecanoylbenzene: Dodecanoyl chloride ꢀ219 g, 1 mol) was
added dropwise to
a solution of bromobenzene ꢀ314 g, 2 mol) and
aluminum chloride ꢀ160 g, 1.2 mol). The mixture was stirred at 508C for
1 h. The reaction mixture was then poured into ice water and extracted with
dichloromethane. The organic phase was washed with 2m HCl and brine
and dried ꢀMgSO4). After removal of the solvent, the residue was purified
by recrystallization from ethanol to afford 4-bromododecanoylbenzene as
colorless plates ꢀ227 g, 67%): M.p. 64.08C; 1H NMR ꢀ300 MHz, CDCl3):
d ˆ 7.73 ꢀd, J ˆ 8.0 Hz, 2H), 7.52 ꢀd, J ˆ 8.0 Hz, 2H), 2.83 ꢀt, J ˆ 7.5 Hz, 2H),
1.63 ꢀq, J ˆ 7.5 Hz, 2H), 1.31 ± 1.08 ꢀm, 16H), 0.89 ꢀt, J ˆ 7.0 Hz, 3 H) ;
13C NMR ꢀ75 MHz, CDCl3): d ˆ 199.86, 136.21, 132.24, 129.99, 128.36,
38.98, 32.29, 30.00, 29.87, 29.85, 29.71, 24.68, 23.07, 14.49; FD-MS: m/z ꢀ%):
between 5 and 208CminÀ1
.
X-ray diffraction experiments were performed using a Siemens D 500 Kris-
talloflex with a graphite-monochromatized CuKa X-ray beam, emitted from
a rotating Rigaku RV-300 anode. The temperature of the samples, which
were directly on a copper sample-holder or in glass capillaries, was
measured by a bimetal sensor and calibrated by reference measurements.
Materials
NiCl2ꢀdppp), 1m dodecylmagnesiumbromide in diethyl ether, AlCl3 ꢀ99%),
dodecanoyl chloride ꢀ98%), hydrazine hydrate ꢀ98%), piperidine ꢀ99%),
trimethylsilylacetylene ꢀ98%), KF ꢀ99%), 4-bromoiodobenzene ꢀ98%),
sodium hydride ꢀ95%), iron pentacarbonyl, diphenyl ether ꢀ99%), nitro-
methane ꢀ96 ‡ %), undecylamine ꢀ98%), copper cyanide ꢀ99%), cyclo-
hexanol ꢀ99%), and N-methyl-2-pyrrolidinone ꢀ99 ‡ %) ꢀall from Aldrich)
were used as received. Triphenylphosphine ꢀ97%), iodine ꢀ99.5%), CS2
ꢀ99 ‡ %), dimethylformamide, benzyltriethylammoniumchloride ꢀ98%),
and potassium-tert-butanolate ꢀall from Fluka) were used as received.
Ironꢀiii)chloride ꢀ98%), triethylamine ꢀ99%), and copper iodide ꢀ98%)
ꢀall from Merck) were used as received. Trans-dichlorobisꢀtriphenylphos-
phine)palladiumꢀii) ꢀ99%), trisꢀdibenzylideneacetone)-dipalladiumꢀ0), and
ꢀR)-BINAP ꢀ98%) ꢀall from Strem) were used as received. Dimethyl
sulfoxide, methanol, ethanol, and chloroform ꢀA.C.S. reagent, Riedel-de
‡
338.5 [M] ꢀ100); anal. calcd ꢀ%) for C18H27OBr: C 63.72, H 8.02; found: C
63.46, H 7.96.
4-Bromododecylbenzene ?7): A mixture of 4-bromododecanoylbenzene
ꢀ200 g, 589 mmol), hydrazine hydrate ꢀ98%, 85.8 mL), and potassium
hydroxide ꢀ132 g, 2.36 mol) in triethylene glycol ꢀ1 L) was heated at reflux
for 2 h. The mixture was distilled at atmospheric pressure until the
temperature of the reaction mixture reached 2108C. After cooling to room
temperature, the resulting mixture was poured into water, acidified with
conc. HCl ꢀ220 mL), and extracted with dichloromethane. The organic
phase was washed with water, dried ꢀMgSO4) and concentrated under
reduced pressure. The residue was purified by column chromatography on
silica gel with petroleum ether to afford 7 as colorless oil ꢀ130 g, 68%):
1H NMR ꢀ300 MHz, CDCl3): d ˆ 7.40 ꢀd, J ˆ 8.0 Hz, 2H), 7.06 ꢀd, J ˆ
8.0 Hz, 2H), 2.58 ꢀt, J ˆ 7.5 Hz, 2H), 1.61 ꢀquint, J ˆ 7.5 Hz, 2H), 1.36 ±
1.18 ꢀm, 18H), 0.92 ꢀt, J ˆ 7.0 Hz, 3H); 13C NMR ꢀ75 MHz, CDCl3): d ˆ
142.25, 131.65, 130.56, 119.64, 35.76, 32.33, 31.72, 30.05, 29.98, 29.87, 29.76,
È
È
Haen) were used as received. THF ꢀA.C.S. reagent, Riedel-de Haen) was
refluxed over potassium and distilled freshly before use. Toluene ꢀA.C.S.
È
reagent, Riedel-de Haen) was refluxed over sodium and distilled freshly
‡
29.60, 23.10, 14.51; FD-MS: m/z ꢀ%): 324.2 [M] ꢀ100).
È
before use, CH2Cl2 ꢀA.C.S. reagent, Riedel-de Haen) was dried over CaH2
and freshly distilled before use.
4-[?Trimethylsilyl)ethynyl]dodecylbenzene ?8): A solution of 7 ꢀ20.3 g,
62.5 mmol), triphenylphosphine ꢀ1.65 g, 6.30 mmol), copper iodide ꢀ1.15 g,
Synthesis
6.02 mmol),
and
trans-dichlorobisꢀtriphenylphosphine)palladiumꢀii)
4,4'-Didodecyl-trans-stilbene ?5b): Dodecylmagnesiumbromide ꢀ550 mL,
1m in diethyl ether, 0.55 mol) was added to a solution of 4,4'-dibromo-trans-
stilbene[18] ꢀ85 g, 251 mmol) and NiCl2ꢀdppp) ꢀ5.49 g) in diethyl ether
ꢀ600 mL). After stirring overnight, 2m aqueous HCl was added to the
reaction mixture. The organic phase, together with some precipitate was
separated from the aqueous phase and the solvent was removed under
reduced pressure. The residue was dissolved in dichloromethane and
filtered over silica gel to afford 4,4'-didodecyl-trans-stilbene as a colorless
solid ꢀ119 g, 92%): M.p. 80 ± 828C; 1H NMR ꢀ300 MHz, CDCl3): d ˆ 7.43
ꢀd, J ˆ 8.0 Hz, 4H), 7.18 ꢀd, J ˆ 8.0 Hz, 4H), 7.05 ꢀs, 2H), 2.60 ꢀt, J ˆ 7.6 Hz,
4H), 1.1 ± 1.8 ꢀm, 40H), 0.90 ꢀd, J ˆ 7.6 Hz, 6H); 13C NMR ꢀ75 MHz,
CDCl3): d ˆ 142.8, 135.4, 129.1, 128.1, 126.7, 36.1, 32.3, 31.8, 30.1, 30.0, 29.9,
ꢀ2.10 g, 3.00 mmol) in piperidine ꢀ400 mL) was heated at 508C and
trimethylsilylacetylene ꢀ18 mL, 12.5 g, 127 mmol) was added dropwise.
The resulting mixture was stirred at 808C for 24 h under an argon
atmosphere. The reaction mixture was poured into a saturated NH4Cl
solution and extracted with dichloromethane. The organic phase was
washed with half-saturated ammonium chloride solution and water. After
removing the solvent the residue was purified by column chromatography
on silica gel with petroleum ether to afford 8 ꢀ19.1 g, 89%) as a pale yellow
oil. 1H NMR ꢀ200 MHz, CDCl3): d ˆ 7.38 ꢀd, J ˆ 8.0 Hz, 2H), 7.10 ꢀd, J ˆ
8.0 Hz, 2H), 2.59 ꢀt, J ˆ 7.5 Hz, 2H), 1.58 ꢀquint, J ˆ 7.5 Hz, 2H), 1.46 ± 1.12
ꢀm, 18H), 0.89 ꢀt, J ˆ 6.6 Hz, 3H), 0.25 ꢀs, 3H).
4-Ethynyldodecylbenzene ?9): A solution of potassium fluoride ꢀ4.39 g,
75.6 mmol) in water ꢀ21 mL) was added to a solution of 8 ꢀ12.9 g
37.8 mmol) in dimethylformamide ꢀ300 mL). After stirring at room
temperature for 3 h the reaction mixture was poured into water and
extracted with toluene. The organic phase was washed with water, dried
ꢀMgSO4), and concentrated under reduced pressure. The residue was
purified by column chromatography on silica gel with petroleum ether to
‡
29.7, 23.1, 14.5; FD-MS: m/z ꢀ%): 516.4 [M] ꢀ100); anal. calcd ꢀ%) for
C38H60: C 88.30, H 11.70; found: C 87.91, H 11.43.
1,2-Dibromo-1,2-bis?4-dodecylphenyl)ethane ?6): Bromine ꢀ6.7 mL,
131 mmol) was added to a solution of 5b ꢀ68 g, 131 mmol) in chloroform
ꢀ800 mL). After stirring overnight the solution was washed with aqueous
sodium sulfite and water ꢀ2 Â ) and dried ꢀMgSO4). The solvent was
evaporated to afford 6 as a colorless solid ꢀ81 g, 90%): M.p. 115 ± 1178C;
1H NMR ꢀ300 MHz, CDCl3): d ˆ 7.50 ꢀd, J ˆ 8.0 Hz, 4H), 7.25 ꢀd, J ˆ
8.0 Hz, 4H), 7.10 ꢀd, J ˆ 8.0 Hz, 4H), 7.00 ꢀd, J ˆ 8.0 Hz, 4H), 5.55 ꢀs,
2H), 5.50 ꢀs, 2H), 2.70 ꢀt, J ˆ 7.8 Hz, 4H), 2.55 ꢀt, J ˆ 7.8 Hz, 4H), 1.2 ± 1.9
ꢀm, 40H), 0.95 ꢀd, J ˆ 7.6 Hz, 6H); 13C NMR ꢀ75 MHz, CDCl3): d ˆ 144.4,
143.8, 137.8, 135.5, 129.1, 128.9, 128.5, 128.1, 59.9, 56.8, 36.1, 35.9, 32.3, 31.6,
1
afford 9 ꢀ9.71 g, 95%) as a colorless oil. H NMR ꢀ200 MHz, CDCl3): d ˆ
7.42 ꢀd, J ˆ 8.1 Hz, 2H), 7.14 ꢀd, J ˆ 8.1 Hz, 2H), 3.03 ꢀs, 1H), 2.61 ꢀt, J ˆ
7.7 Hz, 2H), 1.61 ꢀquint, J ˆ 7.7 Hz, 2H), 1.44 ± 1.11 ꢀm, 18H), 0.90 ꢀt, J ˆ
6.2 Hz, 3H); 13C NMR ꢀ50 MHz, CDCl3): d ˆ 144.37, 132.54, 128.87, 128.69,
119.87, 84.38, 76.88, 36.42, 32.46, 31.71, 30.19, 30.12, 30.02, 29.90, 29.78,
‡
‡
23.22, 14.60; FD-MS: m/z ꢀ%): 270.3 [M] ꢀ100).
31.5, 30.1, 30.0, 29.9, 29.8, 29.6, 23.1, 14.5; FD-MS: m/z ꢀ%): 676.7 [M]
ꢀ100); anal. calcd ꢀ%) for C38H60Br2: C 67.45, H 8.94; found: C 67.62, H 8.68.
4-Bromo-4'-dodecyldiphenylacetylene ?3c): Triphenylphosphine ꢀ948 mg,
3.62 mmol), copper iodide ꢀ691 mg, 3.63 mmol), and trans-dichlorobisꢀtri-
phenylphosphine)palladiumꢀii) ꢀ1.26 g, 1.80 mmol) in piperidine ꢀ280 mL)
9 ꢀ9.71 g, 35.9 mmol) was added dropwise to 4-bromoiodobenzene ꢀ11.2 g,
39.5 mmol). The resulting mixture was stirred at room temperature for 3 h
under an argon atmosphere. The reaction mixture was poured into a
4,4'-Didodecyldiphenylacetylene ?3a): A solution of 6 ꢀ80 g, 118 mmol)
and potassium-tert-butanolate ꢀ140 g, 1.248 mol) in tert-butanol ꢀ1 L) was
heated at reflux overnight. The reaction mixture had cooled to room
temperature and extracted with methyl-tert-butyl ether. The organic phase
was washed with 2m aqueous HCl and a saturated sodium bicarbonate
4338
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Chem. Eur. J. 2000, 6, No. 23

Hexa-peri-hexabenzocoronenes
4327±4342
‡
saturated ammonium chloride solution and extracted with dichlorome-
thane. The organic phase was washed with concentrated ammonium
chloride solution and water. After removing the solvent the residue was
purified by column chromatography on silica gel with petroleum ether to
yield 3c ꢀ11.34 g, 74%) as colorless needles. M.p. 69.58C; 1H NMR
ꢀ500 MHz, CDCl3): d ˆ 7.45 ꢀd, J ˆ 8.4 Hz, 2H), 7.41 ꢀd, J ˆ 8.1 Hz, 2H),
7.356 ꢀd, J ˆ 8.4 Hz, 2H), 7.14 ꢀd, J ˆ 8.1 Hz, 2H), 2.59 ꢀt, J ˆ 7.6 Hz, 2H),
1.59 ꢀt, J ˆ 7.6 Hz, 2H), 1.33 ± 1.20 ꢀm, 18H), 0.87 ꢀt, J ˆ 7.0 Hz, 3H);
13C NMR ꢀ125 MHz, CDCl3): d ˆ 143.76, 132.96, 131.57, 131.50, 128.51,
122.54, 122.22, 120.04, 90.79, 87.67, 35.92, 31.92, 31.20, 29.66, 29.63, 29.56,
29.47, 29.34, 29.24, 22.68, 14.10. anal. calcd ꢀ%) for C26H33Br: C 73.40, H
7.82, Br 18.78; found: C 73.85, H 7.71, Br 18.27.
29.2, 22.7, 14.1; FD-MS: m/z ꢀ%): 878.6 [M] ꢀ100); IR ꢀKBr): nÄ ˆ 2924 ꢀs),
2853 ꢀs), 1709 ꢀs), 1486 ꢀm), 1465 ꢀm), 1072 ꢀm), 1010 ꢀm), 847 ꢀw), 766 ꢀw);
anal. calcd ꢀ%) for C53H66Br2O: C 72.44, H 7.52, Br 18.20; found: C 72.26, H
7.41, Br 17.80.
4-Bromo-4',4'',4''',4'''',4''''-pentadodecylhexaphenylbenzene ?4b) as an ex-
ample for the synthesis of substituted hexaphenylbenzenes: A mixture of
4-bromo-4'-dodecyldiphenylacetylene ꢀ11) ꢀ4.00 g, 9.41 mmol) and tetraꢀ4-
dodecylphenyl)cyclopentadienone ꢀ15b) ꢀ10.0 g, 9.46 mmol) in diphenyl
ether ꢀ15 mL) was heated at reflux for 16 h under an argon atmosphere.
After cooling to room temperature ethanol ꢀ300 mL) was added to the
reaction mixture. The solvent was decanted and the residual oil was
purified by column chromatography on silica gel with petroleum ether/
dichloromethane 10:1 to afford 4b.
Compound 4b: Yield: 71%; m.p. 35.58C; 1H NMR ꢀ500 MHz, CDCl3): d ˆ
6.93 ꢀd, J ˆ 8.2 Hz, 2H), 6.66 ± 6.61 ꢀm, 16H), 6.59 ꢀd, J ˆ 7.9 Hz, 6H), 2.35
ꢀt, J ˆ 7.6 Hz, 4H), 2.32 ꢀt, J ˆ 7.6 Hz, 6H), 1.43 ± 1.06 ꢀm, 100H), 0.87 ꢀt,
J ˆ 6.9 Hz, 15H); 13C NMR ꢀ125 MHz, CDCl3): d ˆ 140.85, 140.57, 140.25,
140.11, 139.48, 139.19, 138.80, 138.06, 137.99, 137.84, 133.24, 131.30, 129.56,
126.77, 126.50, 119.06, 35.35, 35.32, 31.94, 31.23, 31.14, 29.76, 29.75, 29.69,
1,3-Bis?4-dodecylphenyl)-propan-2-one ?13b) as an example for the syn-
thesis of substituted diphenylpropan-2-ones: A vigorously stirred mixture
of 4-bromomethyldodecylbenzene ꢀ12b) ꢀ24 g, 71 mmol), iron penta-
carbonyl ꢀ7.3 g, 37 mmol) benzyltriethylammoniumchloride ꢀ0.54 g,
1.93 mmol) and sodium hydroxide ꢀ12.3 g dissolved in 7 mL H2O) in
dichloromethane ꢀ170 mL) was heated at reflux overnight. After cooling to
room temperature half concentrated HCl ꢀ130 mL) was added. The organic
phase was then washed with 2m HCl and water and dried ꢀMgSO4). The
solvent was evaporated, and the residue was purified by column chroma-
tography with petrol ether/CH2Cl2 3:1 to afford 13a.
‡
29.54, 29.38, 28.88, 28.82, 22.69, 14.09; FD-MS: m/z ꢀ%): 1454.5 [M] ꢀ100);
anal. calcd ꢀ%) for C102H149Br: C 84.19, H 10.32, Br 5.49; found: C 84.30, H
10.43, Br 5.40.
Compound 13a: Yield: 53%; m.p. 1168C; 1H NMR ꢀ300 MHz, CDCl3):
d ˆ 7.47 ꢀd, J ˆ 8.4 Hz, 4H), 7.04 ꢀd, J ˆ 8.4 Hz, 4H), 3.69 ꢀs, 4H); 13C NMR
ꢀ75 MHz, CDCl3): d ˆ 205.1, 133.0, 132.3, 131.6, 121.7, 48.9; FD-MS: m/z
1
Compound 4c: Oil; yield: 76%; H NMR ꢀ250 MHz, CDCl3): d ˆ 6.97 ꢀd,
J ˆ 8.5 Hz, 4H), 6.65 ꢀd, J ˆ 8.5 Hz, 4H), 6.62 ± 6.60 ꢀm, 16H), 2.38 ± 2.28
ꢀm, 8H), 1.38 ± 1.04 ꢀm, 80H), 0.88 ± 0.83 ꢀm, 12H); 13C NMR ꢀ63 MHz,
CDCl3): d ˆ 140.7, 140.0, 139.3, 139.2, 138.9, 138.1, 137.3, 137.1, 132.7, 130.8,
129.5, 126.4, 126.2, 119.1, 34.9, 31.6, 30.8, 30.7, 29.4, 29.3, 29.2, 29.0, 28.5,
‡
ꢀ%): 367.7 [M] ꢀ100); IR: nÄ ˆ ꢀKBr) 1715 ꢀs), 1650 ꢀm), 1488 ꢀm), 1265 ꢀm),
1012 ꢀw), 738 ꢀm), 704 ꢀw); anal. calcd ꢀ%) for C15H12Br2O: C 48.94, H 3.26;
found: C 48.71, H 3.05.
‡
28.4, 22.3, 13.7; FD-MS: m/z ꢀ%): 1365.1 [M] ꢀ100).
Compound 13b: Yield: 47%; m.p. 72 ± 748C; 1H NMR ꢀ300 MHz, CDCl3):
d ˆ 7.15 ꢀd, J ˆ 8.0 Hz, 4H), 7.07 ꢀd, J ˆ 8.0 Hz, 4H), 3.69 ꢀs, 4H), 2.60 ꢀt,
J ˆ 7.4 Hz, 4H), 1.7 ± 1.1 ꢀm, 40H), 0.91 ꢀd, J ˆ 7.4 Hz, 6H); 13C NMR
ꢀ75 MHz, CDCl3): d ˆ 206.5, 142.2, 131.7, 129.8, 129.2, 49.2, 36.1, 42.4, 31.9,
1
Compound 4d: Yield: 74%; m.p. 718C; H NMR ꢀ300 MHz, CDCl3): d ˆ
6.88 ꢀd, J ˆ 8.5 Hz, 4H), 6.61 ꢀd, J ˆ 8.5 Hz, 4H), 6.58 ± 6.56 ꢀm, 16H), 2.29
ꢀt, J ˆ 7.3 Hz, 8H), 1.35 ± 1.04 ꢀm, 80H), 0.91 ꢀt, J ˆ 6.8 Hz, 12H); 13C NMR
ꢀ75 MHz, CDCl3): d ˆ 141.6, 140.8, 140.4, 138.9, 134.6, 132.5, 130.8, 128.1,
120.2, 36.7, 33.3, 32.5, 31.1, 31.0, 30.9, 30.7, 30.1, 24.1, 15.6; FD-MS: m/z ꢀ%):
‡
30.0, 29.8, 23.2, 14.6; FD-MS: m/z ꢀ%): 546,4 [M] ; IR ꢀKBr): nÄ ˆ 3421 ꢀs),
3043 ꢀm), 2891 ꢀs), 2849 ꢀs), 1715 ꢀs), 1467 ꢀs); anal. calcd ꢀ%) for C39H62O:
C 85.65, H 11.43; found: C 85.17, H 11.40.
‡
1365.1 [M] ꢀ100); anal. calcd ꢀ%) for C90H124Br2: C 79.19, H 9.09, Br 11.72;
found: C 79.24, H 8.95, Br 11.57.
4,4'-Didodecylbenzil ?11): A mixture of 4,4'-didodecyldiphenylacetylene
ꢀ50 g, 97 mmol) and iodine ꢀ12.2 g, 48 mmol) in dimethyl sulfoxide
ꢀ250 mL) was stirred at 1558C overnight. After cooling to room temper-
ature, the reaction mixture was poured into an aqueous sodium thiosulfate
solution ꢀ500 mL) and extracted with dichloromethane. The organic phase
was washed with water and dried ꢀMgSO4). After evaporation of the
solvent the residue was purified by column chromatography with petrol
ether/dichloromethane 3:1 to yield 11 ꢀ55 g, 69%) as yellow crystals. M.p.
478C; 1H NMR ꢀ300 MHz, CDCl3): d ˆ 7.90 ꢀd, J ˆ 8.2 Hz, 4H), 7.30 ꢀd, J ˆ
8.2 Hz, 4H), 2.68 ꢀt, J ˆ 7.4 Hz, 4H), 1.8 ± 1.1 ꢀm, 40H), 0.88 ꢀd, J ˆ 7.6 Hz,
6H); 13C NMR ꢀ75 MHz, CDCl3): d ˆ 194.8, 151.2, 131.2, 128.8, 129.3, 36.5,
2-Bromo-5,8,11,14,17-pentadodecylhexa-peri-hexabenzocoronene ?2a) as
an example for the synthesis of substituted hexa-peri-hexabenzocoronenes:
A solution of ironꢀiii)chloride ꢀ3.87 g, 23.9 mmol) in nitromethane ꢀ30 mL)
was added dropwise to a stirred solution of 4-bromo-4',4'',4''',4'''',4'''''-
pentadodecylhexaphenylbenzene ꢀ4b) ꢀ2.03 g, 140 mmol) in dichlorome-
thane ꢀ400 mL). An argon stream was bubbled through the reaction
mixture throughout the entire reaction. After stirring another 30 min the
reaction was quenched with methanol ꢀ200 mL). The precipitate was
filtered, washed with methanol ꢀ200 mL), and dried under reduced
pressure. The crude product was purified by column chromatography on
silica gel with hot toluene/petroleum ether to afford 2a.
‡
32.2, 31.3, 29.9, 29.8, 29.7, 29.6, 29.5, 23.0, 14.4; FD-MS: m/z ꢀ%): 546.3 [M]
Compound 2a: Yield: 93%; 1H NMR ꢀ500 MHz, 50% CDCl3/CS2): d ˆ
7.99 ꢀs, 2H), 7.86 ꢀs, 2H), 7.75 ꢀs, 2H), 7.61 ꢀs, 2H), 7.53 ꢀs, 2H), 7.40 ꢀs, 2H),
2.94 ꢀm, 2H), 2.73 ꢀm, 4H), 2.51 ꢀm, 4H), 2.03 ꢀm, 2H), 1.86 ꢀm, 4H), 1.78 ±
1.24 ꢀm, 94H), 0.95 ± 0.87 ꢀm, 15H); 13C NMR ꢀ125 MHz, 50% CDCl3/
CS2): d ˆ 138.86, 138.71, 138.64, 130.10, 128.82, 128.58, 128.29, 128.17,
127.03, 122.24, 121.99, 121.86, 121.76, 121.70, 120.64, 120.38, 120.22, 120.14,
120.00, 119.91, 118.40, 118.06, 117.81, 117.10, 37.40, 37.20, 36.86, 32.67, 32.50,
32.21, 32.08, 31.96, 30.43, 30.34, 30.27, 30.18, 30.11, 30.08, 30.02, 29.99, 29.91,
ꢀ100); IR ꢀKBr): nÄ ˆ 3438 ꢀs), 2925 ꢀm), 2850 ꢀs), ꢀs), 1671 ꢀs), 1606 ꢀs); anal.
calcd ꢀ%) for C39H58O2: C 83.46, H 10.69; found: C 83.49, H 10.89.
Tetrakis?4-dodecylphenyl)cyclopentadienone ?14a) as an example for the
synthesis of substituted tetraarylcyclopentadienones: A solution of potas-
sium hydroxide ꢀ1.2 g, 22 mol) in ethanol ꢀ6 mL) was added to a refluxing
solution of 11 ꢀ12 mg, 22 mmol) and 1,3-bisꢀ4-dodecylphenyl)propan-2-one
ꢀ10.81 g, 20 mmol) in ethanol ꢀ36 mL). After 5 min the reaction was cooled
to 08C and the resulting purple oil was separated from the solvent. Column
chromatography of this viscous oil with petrol ether/dichloromethane 4:1
afforded 14a as a purple solid.
‡
29.56, 22.86, 14.19; FD-MS: m/z ꢀ%): 1442.1 [M] ꢀ100); anal. calcd ꢀ%) for
C102H149Br: C 84.19, H 10.32, Br 5.49; found: C 84.26, H 10.39, Br 5.17.
Compound 2b: Yield: 89%; 1H NMR ꢀ250 MHz, 50% CDCl3/CS2): d ˆ
7.77 ꢀs, 2H), 7.53 ꢀs, 2H), 7.32 ꢀs, 2H), 7.03 ꢀs, 2H), 6.91 ꢀs, 2H), 6.85 ꢀs, 2H),
2.86 ꢀt, J ˆ 7.2 Hz, 4H), 2.52 ꢀt, J ˆ 7.2 Hz, 4H), 2.09 ± 1.90 ꢀm, 4H), 1.85 ±
1.32 ꢀm, 76H), 1.02 ± 0.97 ꢀm, 12H); 13C NMR ꢀ125 MHz, CDCl3): d ˆ
139.08, 138.58, 129.78, 129.13, 128.48, 128.29, 127.86, 126.44, 122.60, 122.22,
121.10, 120.92, 120.87, 120.69, 120.40, 120.00, 119.87, 117.54, 117.01, 116.00,
110.39, 37.67, 37.28, 32.93, 32.61, 32.42, 30.85, 30.79, 30.64, 30.59, 30.56, 30.54,
Compound 14a: Yield: 43%; m.p. 558C; 1H NMR ꢀ300 MHz, CDCl3): d ˆ
7.19 ꢀd, J ˆ 8.2 Hz, 4H), 7.05 ꢀd, J ˆ 8.2 Hz, 4H), 6.98 ꢀd, J ˆ 8.2 Hz, 4H),
6.83 ꢀd, J ˆ 8.2 Hz, 4H), 2.55 ꢀt, J ˆ 7.5 Hz, 4H), 1.8 ± 1.1 ꢀm, 40H), 0.91 ꢀd,
J ˆ 7.6 Hz, 6H); 13C NMR ꢀ75 MHz, CDCl3): d ˆ 154.6, 143.6, 142.5, 131.2,
130.4, 129.8, 128.9, 128.5, 128.3, 125.2, 36.2, 32.4, 31.7, 31.5, 30.2, 30.0, 29.9,
‡
29.7, 23.2, 14.6; FD-MS: m/z ꢀ%): 1057.0 [M] ꢀ100); IR ꢀKBr): nÄ ˆ 2924 ꢀs),
2853 ꢀs), 1710 ꢀs), 1465 ꢀs); anal. calcd ꢀ%) for C77H116O: C 87.43, H 11.05;
found: C 87.12, H 11.12.
‡
30.45, 30.11, 23.49, 14.71; FD-MS: m/z ꢀ%): 1353.4 [M] ꢀ100); anal. calcd
ꢀ%) for C90H112Br2: C 79.86; H 8.34, Br 11.81; found: C 79.88, H 8.46, Br: 11.40.
Compound 14b: Yield: 60%; m.p. 558C; 1H NMR ꢀ300 MHz, CDCl3): d ˆ
7.34 ꢀd, J ˆ 8.5 Hz, 4H), 7.08 ꢀd, J ˆ 8.5 Hz, 4H), 6.97 ꢀd, J ˆ 8.0 Hz, 4H),
6.76 ꢀd, J ˆ 8.0 Hz, 4H), 2.54 ꢀt, J ˆ 7.5 Hz), 1.80 ± 1.10 ꢀm, 40H), 0.91 ꢀt, J ˆ
6.8 Hz, 6H); 13C NMR ꢀ75 MHz, CDCl3): d ˆ 199.6, 155.3, 143.9, 131.6,
131.2, 130.2, 129.8, 129.2, 128.1, 123.9, 121.7, 35.8, 31.9, 31.0, 29.7, 29.5, 29.4,
Compound 2c: Yield: 87%; 1H NMR ꢀ300 MHz, 50% CDCl3/CS2): d ˆ 7.51
ꢀs, 4H), 7.11 ꢀs, 8H), 2.42 ꢀt, J ˆ 7.4 Hz, 8H), 1.71 ± 1.40 ꢀm, 80H), 0.98 ꢀt,
J ˆ 6.8 Hz, 12H); 13C NMR ꢀ75 MHz, CDCl3): d ˆ 138.8, 130.0, 127.8, 126.8,
122.6, 121.4, 121.1, 120.8, 120.2, 117.2, 116.9, 37.3, 32.8, 32.6, 30.9, 30.8, 30.7,
Chem. Eur. J. 2000, 6, No. 23
ꢁ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2000
0947-6539/00/0623-4339 $ 17.50+.50/0
4339

J. P. Rabe, K. Müllen et al.
FULL PAPER
‡
30.6, 30.3, 23.7, 15.0; FD-MS: m/z ꢀ%): 1353.4 [M] ꢀ100); anal. calcd ꢀ%)
pressure. The residue was purified by column chromatography on silica gel
with petroleum ether/carbon disulfide 3:1 and hot toluene/petroleum ether
1:1 to afford 16 ꢀ87 mg, 17%) as yellow crystals. 1H NMR ꢀ500 MHz, 50%
CDCl3/CS2): d ˆ 8.27 ꢀs, 2H), 8.26 ꢀs, 2H), 8.19 ꢀs, 2H), 8.17 ꢀs, 4H), 8.14 ꢀs,
2H), 4.76 ꢀm, 1H), 2.98 ꢀt, J ˆ 8.4 Hz, 4H), 2.93 ꢀt, J ˆ 8.4 Hz, 2H), 2.91 ꢀt,
J ˆ 8.4 Hz, 4H), 2.39 ± 2.32 ꢀm, 2H), 2.16 ± 2.08 ꢀm, 2H), 2.00 ± 1.88 ꢀm,
14H), 1.85 ± 1.77 ꢀm, 2H), 1.76 ± 1.24 ꢀm, 90H), 0.892 ꢀt, J ˆ 6.6 Hz, 15H);
13C NMR ꢀ125 MHz, 50% CDCl3/S2): d ˆ 155.57, 139.31, 139.14, 131.22,
129.42, 129.31, 129.20, 129.13, 129.10, 123.08, 122.79, 121.13, 120.89, 120.72,
120.67, 119.78, 119.19, 118.67, 118.48, 109.00, 75.35, 37.26, 37.23, 32.46, 32.43,
32.38, 32.32, 32.04, 30.19, 30.16, 30.04, 30.00, 29.93, 29.85, 29.53, 26.17, 24.06,
for C90H112Br2: C 79.86, H 8.34, Br 11.81; found: C 79.77, H 8.22, Br 11.32.
2-?N-Undecyl)amino-5,8,11,14,17-pentadodecylhexa-peri-hexabenzocoro-
nene ?15a) as an example for the synthesis of amino-substituted hexa-peri-
hexabenzocoronenes: A mixture of 2-bromo-5,8,11,14,17-pentadodecyl-
hexa-peri-hexabenzocoronene ꢀ2a) ꢀ104 mg, 0.0718 mmol), undecylamine
ꢀ0.45 mL, 358 mg, 2.09 mmol), sodium tert-butoxide ꢀ242 mg, 2.52 mmol),
trisꢀdibenzylideneacetone)-dipalladiumꢀ0) ꢀ7.1 mg, 0.0078 mmol), and ꢀR)-
BINAP ꢀꢀR)-ꢀ‡)-2,2'-bisꢀdiphenylphosphino)-1,1'-binaphthyl) ꢀ13 mg,
0.021 mmol) in toluene ꢀ10 mL) was heated at 808C for 4 h under an
argon atmosphere. The resulting mixture was purified by column chroma-
tography on silica gel with hot toluene/petroleum ether to afford the
4-undecylaminohexabenzocoronene ꢀ83 mg, 75%) as yellow crystals.
‡
22.89, 14.20; FD-MS: m/z ꢀ%): 1462.0 [M] ꢀ100); anal. calcd ꢀ%) for
C
108H148O: C 88.70, H 10.20; found: C 88.27, H 10.22.
2-Methoxycarbonyl-5,8,11,14,17-pentadodecylhexa-peri-hexabenzocoro-
nene ?18a) as an example for the synthesis of methylester-substituted hexa-
peri-hexabenzocoronenes: A mixture of 2-bromo-5,8,11,14,17-pentadode-
cylhexa-peri-hexabenzocoronene ꢀ10) ꢀ530 mg, 0.367 mmol), triphenyl-
phosphine ꢀ100 mg, 0.383 mmol), triethylamine ꢀ1.06 g, 10.1 mmol), meth-
anol ꢀ703 mg, 21.9 mmol), and trans-dichlorobisꢀtriphenylphosphine)palla-
diumꢀii) ꢀ131 mg, 0.186 mmol) in tetrahydrofuran ꢀ20 mL) was stirred at
1008C for 5 d under a carbon monoxide atmosphere ꢀ5 atm) in a 40 mL
autoclave. After cooling the reaction mixture the solvent was removed
under reduced pressure. The residue was purified by column chromatog-
raphy on silica gel with hot toluene/petroleum ether to afford 2-methoxy-
carbonyl-5,8,11,14,17-pentadodecylhexa-peri-hexabenzocoronene ꢀ325 mg,
62%) as orange yellow crystals.
Compound 15a: 1H NMR ꢀ500 MHz, 50% CDCl3/CS2): d ˆ 8.30 ꢀs, 4H),
8.26 ꢀs, 2H), 8.20 ꢀs, 2H), 7.97 ꢀs, 2H), 7.38 ꢀs, 2H), 3.23 ꢀt, J ˆ 6.6 Hz, 2H),
2.97 ꢀt, J ˆ 8.7 Hz, 4H), 2.95 ꢀt, J ˆ 8.7 Hz, 2H), 2.85 ꢀt, J ˆ 7.8 Hz, 4H),
2.00 ± 1.78 ꢀm, 12H), 1.68 ± 1.22 ꢀm, 106H), 0.95 ± 0.85 ꢀm, 18H); 13C NMR
ꢀ125 MHz, 50% CDCl3/CS2): d ˆ 145.79, 139.31, 139.13, 139.03, 130.52,
129.56, 129.50, 129.31, 129.04, 123.25, 123.15, 123.11, 120.80, 120.68, 119.69,
119.31, 118.31, 118.09, 117.68, 105.49, 44.19, 37.35, 37.20, 32.56, 32.42, 32.07,
32.03, 30.30, 30.24, 30.18, 30.05, 30.00, 29.92, 29.89, 29.84, 29.55, 29.51, 27.77,
‡
22.85, 22.81, 14.15; FD-MS: m/z ꢀ%): 1533.1 [M] ꢀ100); anal. calcd ꢀ%) for
C
113H161N: C 88.50, H 10.58, N 0.91; found: C 88.25, H 10.16, N 0.87.
Compound 15b: 1H NMR ꢀ500 MHz, 50% CDCl3/CS2): d ˆ 8.58 ꢀs, 2H),
8.55 ꢀs, 2H), 8.51 ꢀs, 2H), 8.28 ꢀs, 2H), 7.67 ꢀs, 2H),7.36 ꢀs, 2H), 3.72 ꢀm,
2H), 3.28 ꢀt, J ˆ 7.2 Hz, 4H), 3.09 ꢀt, J ˆ 8.0 Hz, 4H), 3.02 ꢀt, J ˆ 8.1 Hz,
4H), 2.02 ± 1.92 ꢀm, 12H), 1.86 ± 1.20 ꢀm, 102H), 0.90 ± 0.85 ꢀm, 18H);
13C NMR ꢀ125 MHz, 50% CDCl3/CS2): d ˆ 145.60, 139.09, 139.01, 130.54,
130.26, 129.54, 129.51, 129.47, 129.33, 123.51, 123.40, 120.86, 120.79, 120.73,
118.78, 118.54, 118.34, 117.91, 105.67, 105.44, 44.12, 37.37, 37.27, 32.58, 32.47,
32.05, 30.22, 30.05, 30.02, 29.95, 29.86, 29.54, 27.73, 22.90, 14.21; FD-MS:
Compound 18a: 1H NMR ꢀ500 MHz, 50% CDCl3/CS2): d ˆ 8.47 ꢀs, 2H),
7.80 ꢀs, 2H), 7.74 ꢀs, 2H), 7.71 ꢀs, 2H), 7.66 ꢀs, 2H), 7.63 ꢀs, 2H), 4.14 ꢀs, 3H),
2.76 ꢀt, J ˆ 8.1 Hz, 2H), 2.66 ꢀt, J ˆ 8.1 Hz, 4H), 2.59 ꢀt, J ˆ 8.1 Hz, 4H),
1.88 ꢀq, J ˆ 8.1 Hz, 2H), 1.83 ± 1.72 ꢀm, 8H), 1.64 ± 1.23 ꢀm, 90H), 0.93 ± 0.88
ꢀm, 15H); 13C NMR ꢀ125 MHz, 50% CDCl3/CS2): d ˆ 167.15, 139.16,
138.90, 128.93, 128.62, 128.52, 128.46, 128.26, 126.43, 125.15, 121.89, 120.65,
120.49, 120.41, 120.25, 119.28, 119.04, 118.22, 117.31, 51.86, 37.24, 37.12,
37.03, 32.49, 32.41, 32.37, 32.07, 31.96, 30.39, 30.34, 30.12, 30.08, 30.05, 29.98,
‡
m/z ꢀ%): 1534.2 [M] ꢀ100); anal. calcd ꢀ%) for C112H160N2: C 87.66, H
10.51, N 1.83; found: C 87.64, H 10.53, N 1.81.
Compound 15c: 1H NMR ꢀ500 MHz, 50% CDCl3/CS2): d ˆ 8.46 ꢀs, 4H),
8.30 ꢀs, 4H), 7.73 ꢀs, 4H), 3.85 ꢀbrm, 2H), 3.37 ꢀt, J ˆ 6.6 Hz, 4H), 3.01 ꢀt,
J ˆ 7.7 Hz, 8H), 1.98 ± 1.85 ꢀm, 12H), 1.59 ± 1.32 ꢀm, 104H), 0.90 ± 0.85 ꢀm,
18H); 13C NMR ꢀ125 MHz, 50% CDCl3/CS2): d ˆ 145.2, 138.5, 130.0, 129.0,
128.7, 122.8, 120.2, 118.4, 117.8, 117.4, 105.0, 43.4, 36.4, 31.5, 31.2, 31.1, 29.3,
‡
29.89, 29.55, 22.86, 14.18; FD-MS: m/z ꢀ%): 1422.3 [M] ꢀ100); anal. calcd
ꢀ%) for C104H140O2: C 87.83, H 9.92; found: C 87.63, H 9.03.
Compound 18b: 1H NMR ꢀ250 MHz, CD2Cl2/CS2): d ˆ 7.83 ꢀs, 2H), 7.78 ꢀs,
2H), 7.61 ꢀs, 2H), 7.50 ꢀs, 2H), 7.36 ꢀs, 2H), 7.25 ꢀs, 2H), 3.99 ꢀs, 3H), 2.71 ꢀt,
J ˆ 7.5 Hz, 4H), 2.49 ꢀt, J ˆ 7.2 Hz, 4H), 1.91 ± 1.25 ꢀm, 80H), 1.03 ± 0.88 ꢀm,
12H); 13C NMR ꢀ125 MHz, CD2Cl2/CS2): d ˆ 167.23, 140.36, 140.21, 129.76,
129.64, 129.21, 128.79, 128.50, 126.41, 122.41, 122.21, 121.92, 121.61, 121.45,
119.66, 119.40, 118.43, 52.81, 38.56, 38.29, 33.61, 33.37, 31.94, 31.90, 31.66,
‡
29.2, 29.1, 29.0, 28.9, 28.6, 26.8, 22.0, 13.3; FD-MS: m/z ꢀ%): 1534.2 [M]
ꢀ100); anal. calcd ꢀ%) for C112H160N2: C 87.66, H 10.51; found: C 87.72, H
10.41.
‡
31.56, 31.52, 31.43, 31.10, 24.50, 15.72; FD-MS: m/z ꢀ%): 1311.9 [M] ꢀ100);
2-Piperidino-5,8,11,14,17-pentadodecylhexa-peri-hexabenzocoronene
?17): A mixture of 2-bromo-5,8,11,14,17-pentadodecylhexa-peri-hexaben-
zocoronene ꢀ2a) ꢀ107 mg, 0.074 mmol), piperidine ꢀ0.21 mL, 181 mg,
2.12 mmol), sodium tert-butoxide ꢀ242 mg, 2.52 mmol), trisꢀdibenzylide-
neacetone)dipalladiumꢀ0) ꢀ7.9 mg, 0.0086 mmol), and ꢀR)-BINAP ꢀꢀR)-
ꢀ‡)-2,2'-bisꢀdiphenylphosphino)-1,1'-binaphthyl) ꢀ16 mg, 0.026 mmol) in
toluene ꢀ10 mL) was heated at 808C for 4 h under an argon atmosphere.
The resulting mixture was purified by column chromatography on silica gel
with hot toluene/petroleum ether to afford 17 ꢀ83 mg, 78%) as yellow
crystals. 1H NMR ꢀ500 MHz, 50% CDCl3/CS2): d ˆ 8.25 ꢀs, 2H), 8.22 ꢀs,
2H), 8.16 ꢀs, 2H), 8.15 ꢀs, 2H), 8.11 ꢀs, 2H), 8.10 ꢀs, 2H), 3.57 ꢀt, J ˆ 5.3 Hz,
4H), 2.95 ꢀt, J ˆ 8.1 Hz, 4H), 2.875 ꢀt, J ˆ 7.5 Hz, 4H), 2.86 ꢀt, J ˆ 7.5 Hz,
2H), 2.10 ± 2.04 ꢀm, 4H), 1.98 ± 1.83 ꢀm, 12H), 1.66 ± 1.23 ꢀm, 90H), 0.92 ±
0.85 ꢀm, 15H); 13C NMR ꢀ125 MHz, 50% CDCl3/CS2): d ˆ 149.80, 139.26,
139.05, 130.45, 129.47, 129.33, 129.11, 123.21, 122.88, 120.89, 120.76, 120.64,
119.34, 119.22, 119.19, 118.54, 118.46, 109.95, 51.64, 37.35, 37.28, 32.62, 32.46,
32.04, 30.22, 30.05, 30.00, 29.92, 29.84, 29.51, 26.63, 24.79, 22.82, 14.16; FD-
anal. calcd ꢀ%) for C94H118O4: C 86.06, H 9.07; found: C 86.03, H 8.98.
2-Cyano-5,8,11,14,17-pentadodecylhexa-peri-hexabenzocoronene ?19a): A
mixture of 2-bromo-5,8,11,14,17-pentadodecylhexa-peri-hexabenzocoro-
nene ꢀ315 mg, 0.219 mmol) and copper cyanide ꢀ4.10 g, 45.7 mmol) in N-
methyl-2-pyrrolidinone ꢀ30 mL) was heated at 1858C for 20 h under an
argon atmosphere. The reaction mixture was poured into 10% ammonium
hydroxide solution. The precipitated crystals were collected by filtration,
washed with water and purified by column chromatography on silica gel
with CS2/petroleum ether 1:1 and toluene/petroleum ether 1:1 to afford the
2-cyano-5,8,11,14,17-pentadodecylhexa-peri-hexabenzocoronene ꢀ184 mg,
61%) as yellow crystals. 1H NMR ꢀ500 MHz, 50% CDCl3/CS2): d ˆ 7.92 ꢀs,
2H), 7.76 ꢀs, 2H), 7.35 ꢀs, 2H), 7.16 ꢀs, 2H), 7.08 ꢀs, 2H), 6.82 ꢀs, 2H), 2.89 ꢀt,
J ˆ 8.2 Hz, 2H), 2.66 ꢀt, J ˆ 8.2 Hz, 4H), 2.17 ꢀt, J ˆ 8.2 Hz, 4H), 1.97
ꢀquint, J ˆ 8.2 Hz, 2H), 1.80 ꢀquint, J ˆ 8.2 Hz, 4H), 1.71 ± 1.25 ꢀm, 94H),
0.98 ± 0.87 ꢀm, 15H); 13C NMR ꢀ125 MHz, 50% CDCl3/CS2): d ˆ 139.44,
138.82, 138.57, 128.75, 128.14, 127.76, 127.60, 127.53, 125.92, 124.25, 121.37,
121.30, 121.12, 120.68, 120.35, 120.29, 120.15, 119.98, 119.22, 118.67, 117.80,
117.36, 115.43, 107.19, 37.27, 37.09, 36.41, 32.68, 32.45, 32.08, 31.98, 31.81,
30.43, 30.36, 30.24, 30.20, 30.16, 30.11, 30.07, 30.04, 30.01, 29.92, 29.58, 22.91,
‡
MS: m/z ꢀ%): 1446.6 [M] ꢀ100); anal. calcd ꢀ%) for C107H147N: C 88.80, H
10.24, N 0.97; found: C 88.21, H 10.26, N 0.91.
2-Cyclohexyloxyhexabenzocoronene ?16): After stirring
a mixture of
‡
14.21; FD-MS: m/z ꢀ%): 1388.4 [M] ꢀ100); anal. calcd ꢀ%) for C103H137N: C
cyclohexanol ꢀ1.14 g, 11.4 mmol) and sodium hydride ꢀ338 mg, 14.1 mmol),
in toluene ꢀ50 mL) at room temperature for 1 h, 2-bromo-5,8,11,14,17-
pentadodecylhexa-peri-hexabenzocoronene ꢀ2a) ꢀ503 mg, 0.348 mmol),
trisꢀdibenzylideneacetone)dipalladiumꢀ0) ꢀ33 mg, 0.036 mmol), and ꢀR)-
BINAP ꢀꢀR)-ꢀ‡)-2,2'-bisꢀdiphenylphosphino)-1,1'-binaphthyl) ꢀ67 mg,
0.11 mmol) was added to the mixture. The resulting mixture was stirred
at 808C for 2 h under an argon atmosphere. The reaction mixture was
poured into water and extracted with hot toluene. The organic phase was
washed with water, dried ꢀMgSO4), and concentrated under reduced
89.05, H 9.94, N 1.01; found: C 88.41, H 10.03, N 0.90.
Acknowledgements
Financial support by the European Commission ꢀTMR-Program Sisitomas)
and by the Volkswagen Stiftung is gratefully acknowledged.
4340
ꢁ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2000
0947-6539/00/0623-4340 $ 17.50+.50/0
Chem. Eur. J. 2000, 6, No. 23

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