Synthesis and crystal packing of large polycyclic aromatic hydrocarbons: Hexabenzo[bc,ef,hi,kl,no,qr]coronene and dibenzo[fg,ij]phenanthro[9,10,1,2,3- pqrst]pentaphene

Article abstract of DOI:10.1039/a908941a

A detailed study of the oxidative cyclodehydrogenation of two oligophenylene precursors resulting in large polycyclic aromatic hydrocarbons (PAHs) which contain up to 42 carbon atoms gave insight into the reaction course. This study confirmed that the reaction occurs exclusively in an intramolecular fashion without the formation of organic side products. X-Ray diffraction, selected area electron diffraction, and low-dose high-resolution electron microscopy were used to analyse the effect of heat treatment and sublimation on the morphology and crystal structure of large PAHs, hexabenzo[bc,ef,hi,kl,no,qr]coronene (HBC) and dibenzo[fg,ij]phenanthro[9,10,1,2,3-pqrst]pentaphene (DBPP). HBC crystallizes in the γ-motif, as has been determined from single crystals previously. The experiments showed that small crystals exhibit some characteristic distortions of the unit cell. DBPP also crystallizes also in the γ-motif, but due to the 'double-bay area' in the periphery of the molecule channels with a diameter of about 4 A are formed in the crystal.

Full text of DOI:10.1039/a908941a

J O U R N A L O F
Synthesis and crystal packing of large polycyclic aromatic
hydrocarbons: hexabenzo[bc,ef,hi,kl,no,qr]coronene and
dibenzo[fg,ij]phenanthro[9,10,1,2,3-pqrst]pentaphene
Christian K uÈ bel, Karin Eckhardt, Volker Enkelmann, Gerhard Wegner and Klaus M uÈ llen*
C H E M I S T R Y
Max-Planck-Institut for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany;
Fax. z49 6131 379 100. E-mail: muellen@mpip-mainz.mpg.de
Received 10th November 1999, Accepted 21st January 2000
A detailed study of the oxidative cyclodehydrogenation of two oligophenylene precursors resulting in large
polycyclic aromatic hydrocarbons (PAHs) which contain up to 42 carbon atoms gave insight into the reaction
course. This study con®rmed that the reaction occurs exclusively in an intramolecular fashion without the
formation of organic side products. X-Ray diffraction, selected area electron diffraction, and low-dose high-
resolution electron microscopy were used to analyse the effect of heat treatment and sublimation on the
morphology and crystal structure of large PAHs, hexabenzo[bc,ef,hi,kl,no,qr]coronene (HBC) and
dibenzo[fg,ij]phenanthro[9,10,1,2,3-pqrst]pentaphene (DBPP). HBC crystallizes in the c-motif, as has been
determined from single crystals previously. The experiments showed that small crystals exhibit some
characteristic distortions of the unit cell. DBPP also crystallizes also in the c-motif, but due to the ``double-bay
Ê
area'' in the periphery of the molecule channels with a diameter of about 4 A are formed in the crystal.
Introduction
Results and discussion
Polycyclic aromatic hydrocarbons (PAHs) have intensively
2
Synthesis
1
been investigated since the pioneering works of Scholl, Clar
3
and Zander. Besides synthetic challenges, correlations
between the chemical structure of PAHs and their electronic
properties, as well as their packing behavior in the solid state,
have been a key concern. Analysis of the electronic properties
of small PAHs led to a better understanding of the electronic
Several pathways for the synthesis of hexa-peri-hexabenzocor-
9
onene (HBC) are described in the literature, however oxidative
cyclodehydrogenation of hexaphenylbenzene (1, HPB) with
copper(II) chloride and aluminum(III) trichloride is the most
8
convenient method (Scheme 1). When using typical experi-
4
structure of aromatic systems. Large PAHs can formally be
8
mental conditions the only product observed was HBC 3,
regarded as two-dimensional graphite sub-units and are well
de®ned model systems for graphite. Different theoretical
methods have been applied to estimate the electronic properties
of graphite based on PAHs with increasing size and varying
which was clearly identi®ed by isotopically resolved ®eld
desorption-mass spectrometry (FD-MS). By using a smaller
excess of the oxidizing agent intermediate products with two
and four newly formed carbon±carbon bonds were also
observed by FD-MS (Fig. 1). It was even possible to isolate
phenyldibenzo[fg,ij]phenanthro[9,10,1,2,3-pqrst]pentaphene
5
topologies. Large aromatic compounds also play a crucial role
during the graphitation of organic compounds. PAHs with a
diameter of 1±2 nm constitute the so-called basic structural
units of the carbomesophase where they form a nematic
discotic liquid crystalline phase, the key step for the formation
(2), which was formed in about 10% yield (see Experimental
section). Other intermediate products containing only two new
carbon±carbon bonds were observed in trace amounts.
Surprisingly, the solubility of compound 2 is even higher
than that of the starting compound hexaphenylbenzene (1) and
this enabled a detailed NMR-spectroscopic analysis. The
6
of well ordered anisotropic graphitic structures. In combina-
tion with the relatively simple molecular structure this has
stimulated research to gain an improved understanding of the
packing behavior of such compounds. It led to a rationaliza-
1
1
7
H± H COSY NMR spectrum of the intermediate reaction
tion of four typical herringbone-type structures for PAHs. An
product 2 could be completely assigned and clearly con®rmed
the proposed structure for compound 2 (Fig. 2). Furthermore,
NMR-spectroscopic analysis of the reaction mixture showed
that compound 2 was the only partially cyclodehydrogenated
species formed under the reaction conditions. The insoluble
material was separated by ®ltration. No partially cyclodehy-
drogenated products were observed in the insoluble fraction by
FD-mass spectrometry. In the soluble fraction the concentra-
tion of any other possible intermediate product other than
compound 2 was below the detection limit of the NMR-
spectroscopic measurement.
The observation and isolation of intermediate products
proves that oxidative cyclodehydrogenation does not occur as a
concerted planarization of all phenyl rings under carbon±
carbon bond formation in one step, but proceeds in separate
reaction steps. The fact that compound 2 was the only
interesting question in this regard is whether a transition to a
planar, graphitic structure will occur if the diameter of the
PAH increases and at which size this will be observed.
Intramolecular oxidative cyclodehydrogenation of oligophe-
8
nylene precursors, which has recently been described, gives
access to extremely large PAHs, which could eventually lead to
a further understanding of graphitic materials and their
electronic properties. Herein, the synthesis and packing
behavior of two large polynuclear aromatic compounds,
hexabenzo[bc,ef,hi,kl,no,qr]coronene (HBC) and dibenzo[fg,ij]-
phenanthro[9,10,1,2,3-pqrst]pentaphene (DBPP) were analysed
in order to develop improved processing methods for ultra-
large PAHs. Next to their electronic role as molecular models
of graphite, the compounds examined here, in particular
DBPP, show some interesting structural features due to
molecular shape as will be discussed below.
DOI: 10.1039/a908941a
J. Mater. Chem., 2000, 10, 879±886
This journal is # The Royal Society of Chemistry 2000
879

View Online
8
Scheme 1 Oxidative cyclodehydrogenation of hexaphenylbenzene yielding HBC (3) after formation of an intermediate product 2.
observable product upon quenching of the reaction, indicates
that 2 is the most stable intermediate.
Further oxidation of the partially cyclodehydrogenated
mixture by adding more oxidizing agent lead to the formation
of HBC 3. Owing to the low solubility, the ®nal product, HBC
3
, could only be analysed by UV/Vis spectroscopy, which is in
9
a
agreement with spectra published by Clar et al., and by FD-
MS as well as by LD-TOF-MS, which showed that no other
organic by-products were formed. In particular, no dimers or
higher oligomers of HBC were observed, indicating that
cyclodehydrogenation occurs only intramolecularly, not inter-
molecularly. This is also in agreement with observations made
8
during the synthesis of ultra-large PAHs.
Dibenzo[fg,ij]phenanthro[9,10,1,2,3-pqrst]pentaphene
(5)
can be synthesized similarly to hexabenzo[bc,ef,hi,kl,no,qr]cor-
onene (3) by oxidative cyclodehydrogenation of 1,2,3,4,5-
pentaphenylbenzene (4) with copper(II) dichloride and alumi-
nium(III) trichloride (Scheme 2). UV/Vis-spectroscopic analysis
of the reaction product is in agreement with the spectrum of
Fig. 1 Normalized superposition of FD-mass spectra taken at three
different times during cyclodehydrogenation of HPB 1: (a) Before the
reaction (only HPB 1), (b) after 12 h with 1.5 eq. of oxidizing agent per
carbon±hydrogen bond (partially cyclodehydrogenated products, HPB
9a
DBPP 5 published by Clar et al. In addition, we were able
clearly to identify the product 5 by NMR spectroscopy and
FD-mass spectrometry. In contrast to HBC 3, the solubility of
DBPP 5 in hot 1,1,2,2-tetrachloroethane is high enough to
1 and small amounts of HBC 3), (c) after two days with 3 eq. of AlCl
per carbon±hydrogen bond (only HBC).
3
1
1
record a well resolved H± H COSY NMR spectrum, which
was completely assigned (Fig. 3). Note that proton a experi-
ences a remarkably low-®eld shift to d 10.36 as a result of the
combined deshielding effect of the ®ve neighboring benzene
rings.
Coupling of two or more DBPP molecules due to
intermolecular reactions was not observed by NMR spectro-
scopy or FD-mass spectrometry, which is again consistent with
the assumption that the oxidative cyclodehydrogenation occurs
only intramolecularly.
The optical properties of the partially cyclodehydrogenated
product 2 and DBPP 5 are similar as expected for the same
chromophore (Fig. 4). Nevertheless, this result is not trivial.
Whereas DBPP
5 is a planar molecule, the partially
cyclodehydrogenated product 2 should be strongly twisted as
1
0
semiempirical AM1 calculations show in agreement with the
crystal structure of the structurally comparable 9,18-diphenyl-
1
tetrabenz[a,c,h,j]anthracene (6) (Fig. 5).
1
The energy barrier for the twist inversion of an isopropyl
derivative of compound 6 was determined to be 16.7 kcal
2
mol by NMR spectroscopy, which is comparable to the
1
11
2
1
difference in heat of formation of about 15 kcal mol for the
symmetric planar and the twisted conformation of 2. The
NMR measurements for the isopropyl derivative of 6 show that
the energy barrier is suf®ciently low for the twist inversion to
1
1
occur on the NMR timescale at 300 K, suggesting a similarly
high ¯exibility for compound 2.
Crystal structures
1
1
Fig. 2 H± H NMR spectrum (500 MHz, 353 K, 1,1,2,2-tetrachloro-
ethane-d of phenyldibenzo[fg,ij]phenanthro[9,10,1,2,3-pqrst]penta-
phene (2).
2
)
The grain size of the material obtained after synthesis depends
on the quenching conditions of the cyclodehydrogenation
8
80
J. Mater. Chem., 2000, 10, 879±886

View Online
9
Scheme 2 Cyclodehydrogenation of pentaphenylbenzene (4) resulting in dibenzo[fg,ij]phenanthro[9,10,1,2,3-pqrst]pentaphene (5).
Fig. 5 Structure of phenyldibenzo[fg,ij]phenanthro[9,10,1,2,3-pqrst]
10
pentaphene (2) according to AM1 calculations (left) and sketch of
the structure of 9,18-phenyltetrabenz[a,c,h,j]anthracene (6) according
to crystal structure analysis (right).
11
1
1
Fig. 3 H± H NMR spectrum (500 MHz, 353 K, 1,1,2,2-tetrachloro-
ethane-d ) of dibenzo[fg,ij]phenanthro[9,10,1,2,3-pqrst]pentaphene (5).
2
1
2
reaction. Scanning (SEM) and transmission electron micro-
scopy (TEM) mainly show aggregates with an irregular shape
Fig. 6 (a) SEM micrograph of microcrystalline HBC 3 obtained
directly after synthesis. (b) Selected area electron diffraction pattern
of the [001] zone of a microcrystal of HBC 3 surrounded by some
nanocrystals (same batch as in a). (c) Packing of HBC molecules along
b direction.
(
small single crystals, which give rise to well de®ned diffraction
Fig. 6a). However, within these aggregates there are some
1
3
patterns in selected area electron diffraction (SAED).
Fig. 6(b) shows a typical diffraction pattern of such a single
crystal surrounded by nanocrystals.
precipitated microcrystals. However, a detailed analysis of the
reciprocal spacings shows that the structure of the micro-
crystals is slightly distorted compared to the single crystal
The appearance of the electron diffraction pattern is very
similar to that of the [001] zone of the single crystal structure of
1
HBC 3 grown from molten pyrene by Goddard et al., which
4
14
structure. With the assumption of an interplanar spacing of
Ê
indicates a similar packing pattern for these relatively rapidly
3
stacking axis (5.7 A from the reciprocal spacing of 1/2.85 A
.5 A a tilt angle of 38³ between the molecular plane and the
2
1
Ê
Ê
)
can be calculated (Fig. 6c). This differs from the angle of 44³,
which has been determined from the single crystal structure.
Ê
Taking this tilt angle an interplanar spacing of about 3.9 A
results which is unreasonably large for a p±p stacking distance.
This deviation is probably due to kinetic effects during fast
precipitation of the HBC molecules.
One possibility to obtain highly crystalline samples or single
crystals of PAHs is crystallization from pyrene or in some cases
even from 1,2,4-trichlorobenzene solution at high tempera-
1
4
tures. However, we found it more convenient to grow single
crystals of PAHs by heat treatment or sublimation under
1
5
vacuum using a temperature gradient.
When HBC 3 was annealed under nitrogen at 400 ³C for 4
days large needle-shaped crystals which were up to 50 mm long
formed from the microcrystalline aggregates. X-Ray powder
diffraction and selected area electron diffraction (Fig. 7)
showed that the material obtained was dominated by a crystal
Fig. 4 UV/Vis spectra (CHCl
3
)
of phenyldibenzo[fg,ij]phenan-
thro[9,10,1,2,3-pqrst]pentaphene (2) (dotted line, right axis) and
dibenzo[fg,ij]phenanthro[9,10,1,2,3-pqrst]pentaphene (5) (full line, left
axis).
J. Mater. Chem., 2000, 10, 879±886
881

View Online
fringes (Fig. 9). In some extreme cases even concentric lattice
fringes with a radius of curvature of about 2 nm were observed
(
Fig. 9b) around a central defect of about 3 to 4 molecules in
diameter. The structural variations observed for the crystals
and the high tendency for defect formation serve as an
indication of a relatively ¯at energy surface as proposed by
7
Gavezzotti and Desiraju for smaller PAHs.
Heating HBC 3 to 480 ³C led to sublimation of the material
and large yellow needles (0.160.160.5 mm) were formed in
the cold area (approx. 420 ³C) of the sublimation ampoule. X-
Ray diffraction analysis of these yellow single crystals
Ê
1
a~18.459, b~5.122, c~12.935 A, b~112.59³, P2 /a, Z~2)
(
showed that the structure is in good agreement with that of
1
4
HBC 3 grown from molten pyrene by Goddard et al.
Ê
(
a~18.431, b~5.119, c~12.929 A, b~112.57³, P2 /a, Z~2).
1
Even at 480 ³C some of the material did not sublime and
formed brown needles (0.0360.0360.1 mm). The ®rst suspi-
cion that decomposition or oligomerization of the material had
occurred could be falsi®ed by laser desorption-time of ¯ight
mass spectrometry (LD-TOF MS) which showed an isotopi-
cally resolved spectrum of HBC. By using the residual powder
mixture instead of the single crystals and suppressing all signals
below 700 Da in the LD-TOF MS, traces of a HBC dimer
could be observed, but the intensity of those signals was at the
resolution limit indicating that the amount of this dimer is very
small.
Fig. 7 TEM overview image of recrystallized HBC showing needles
with different size and some remaining microcrystalline material. The
inset shows a typical selected area electron diffraction pattern of one of
the small needles.
The occurrence of brown HBC crystals has been described
1
4
by Goddard et al. It is not clear to date whether this is a
different polymorph. The small crystal size prevented a detailed
crystal structure analysis. However, preliminary data suggest
that we deal here with crystals of the already known HBC
structure crystallizing in another crystal habit and presumably
with a larger amount of lattice defects, e.g. stacking faults.
Owing to its lower molecular weight, DBPP 5 could be
sublimed at lower temperatures than HBC 3. Sublimation with
a temperature gradient from 410 to 320 ³C led to the formation
of microcrystals between 320 and 370 ³C whereas large needles
(0.160.1562 mm) as well as thin platelets (0.461.2 mm) were
obtained between 370 and 410 ³C. In the residual material,
recrystallization with formation of both large needle-like
crystals and thin platelets was observed.
structure in agreement with the one published for HBC 3 by
1
4
Goddard et al.
The combination of SAED and HREM shows that even
though long, uniform needles with a crystal structure similar to
1
4
the one known in the literature are formed, the smaller
crystals in particular exhibit many defects. In addition to a
variation of the cell parameters a and c of the thin needles by
about 10%, nearly all needle-like crystals are twisted around
their long axis. Bend contours move more or less continuously
over a distance of up to 200 nm indicating regular twisting of
the needle (Fig. 8a). However, dark ®eld images also indicate
discontinuous twisting, probably mediated by small angle grain
boundaries (Fig. 8b).
Some small microcrystallites also exhibit strongly bent lattice
The needle-shaped crystals of DBPP 5 obtained by
Fig. 8 (a) Bend contours in a twisted needle of HBC grown by heat treatment. During tilting the bend contours move continuously over a distance of
up to 200 nm, before a sudden change is observed. (b) Bright ®eld image and dark ®eld images (310, 410, 510, 610 re¯ections) taken under a tilt angle
difference of 3³.
8
82
J. Mater. Chem., 2000, 10, 879±886

View Online
distortion of the molecule, which would also explain the high
solubility of DBPP 5 compared to that of HBC 3. Nevertheless,
structural analysis shows that DBPP 5 is nearly planar. The
largest deviation of a carbon atom from the calculated best
Ê
plane is 0.06 A. This gives rise to a distance of the hydrogen
Ê
atoms in the ``double-bay area'' of 1.97 and 1.98 A (Fig. 11).
The anisotropic thermal vibration ellipsoids show that, at least
in the crystal, the main molecular motion is within the
molecular plane. The anisotropic thermal motion of 5 can be
described with good approximation as rigid body motion. TLS
1
6
analysis leads to eigenvalues of the root mean square
2
librational amplitudes of 0.40, 2.78 and 5.68 degrees.
An unusual structural feature is the packing of two
neighboring DBPP molecules with the ``double-bay areas''
pointing towards each other, which generates a cavity with a
Fig. 9 Dislocations and strongly bent lattice fringes corresponding to
the 001 plane.
sublimation had a suf®cient quality for crystal structure
determination (Fig. 10). DBPP 5 crystallizes in a herring-
bone-type structure (c-motif) typical for large PAHs where the
DBPP molecules are arranged in two columns with a tilt angle
of 43³ between the molecular plane and the stacking axis. This
leads to an angle of 86³ between molecules in neighboring
columns along the c axis (Fig. 10a), whereas the molecules are
oriented nearly parallel to each other along the a axis
1
7
Ê
diameter of about 4 A between the molecules. In the
projection of the crystal structure approximately along the b
axis (Fig. 10b) one recognizes that these cavities are not
isolated, but form channels through the crystal.
At a ®rst glance the formation of these channels is quite
surprising. It might be anticipated that some small reorienta-
tion of the molecules along the c axis would close the cavities
(Fig. 10b). However, this would only be true for a planar,
graphite-like structure, but not for a herringbone-type
(
Fig. 10b).
Two structural features of the crystal structure of DBPP 5
structure. In the case of the c-motif reorganization would
lead to an interdigitation of neighboring stacks, which seems
sterically impossible. Thus the strong tendency for the
formation of a herringbone structure enforces the formation
of channels.
are especially noteworthy. One might expect that the ``double-
bay area'', similar to the cove area, induces some slight
The thin platelets which were also obtained by sublimation
of DBPP 5 were too thin for a X-ray single crystal structure
analysis, but the smallest platelets were of suitable dimensions
to enable electron microscopic analysis. Examinations of about
Fig. 11 (a) In¯uence of the topology: planar, all-benzoid structure of
DBPP (5) containing bay and double-bay areas, and twisted structure
16
of non-all-benzoid tribenzopyrene due to the cove area. (b) Nearly
planar geometry of a DBPP molecule 5 (with anisotropic thermal
vibration ellipsoids according to crystal structure analysis at room
temperature).
Fig. 10 Different projections of the crystal structure of DBPP 5: (a) b±c
plane, (b) a±c plane.
J. Mater. Chem., 2000, 10, 879±886
883

View Online
Fig. 12 (a) Selected area electron diffraction pattern of DBPP platelets.
(
19
1
8
Fig. 13 (a) HREM image of DBPP 5. (b) Fourier-transformed image
of the HREM micrograph.
b) Simulated electron diffraction pattern of DBPP 5 (with a~89³).
thirty different crystallites by SAED showed the same zone for
nearly all crystallites. The electron diffraction patterns
fringes are also visible with lower contrast. Fourier transfor-
1
mation of the image (Fig. 13b) reveals that lattice fringes
9
(
Fig. 12a) of those crystallites are essentially identical to the
Ê
down to d spacings of 2.21 A are present in the image. The d
diffraction pattern of the [100] zone of the needle-shaped
crystals shown above. The only difference is the angle a*, which
should be 90³ for a monoclinic system, whereas approximately
spacing, the intensities of the re¯ections and the systematic
absence correspond to the diffraction pattern (Fig. 12). The
only difference with the SAED pattern is the strong 100
re¯ection, which is only slightly visible in the diffraction
pattern (Fig. 12). We suspect this effect to be due to the defocus
of the image and the contrast transfer function modulating the
observed intensities depending on the reciprocal spacing.
The HREM images of the sublimed DBPP 5 crystallites
exhibit some crystal defects such as slight bending or insertion
of lattice fringes, but in contrast to the heat-treated HBC
sample these defects were observed only occasionally for the
sublimed material. Furthermore, strongly bent lattice fringes as
shown in Fig. 9 were never observed in the case of the sublimed
crystals.
8
9³ was found by electron diffraction analysis. This effect may
be due to a minor distortion of the crystal structure,
1
8
presumably due to surface effects. Simulations of the electron
diffraction pattern using the structure of the needle-shaped
crystals (slightly distorted with a~89³) showed good agree-
ment with the experimentally obtained diffraction pattern
(
Fig. 12). The lattice spacing and the systematic extinction of
some re¯ections are the same, thus indicating only a small
structural variation between the needles and the platelets.
The electron diffraction experiments indicated that the
platelets have the same structure as that of the needle-shaped
crystals. Furthermore, as most platelets are imaged with the
[100] zone, this shows the b±c plane is the main growth
direction. The platelets are very thin, which is consistent with
the assumption that crystal growth in the direction of the
Conclusion
``double-bay area'' under formation of channels is less
favorable than growth in the other two directions.
Synthesis of two large PAHs, hexabenzo[bc,ef,hi,kl,no,qr]cor-
onene (HBC 3) and dibenzo[fg,ij]phenanthro[9,10,1,2,3-
pqrst]pentaphene (DBPP 5), by oxidative cyclodehydrogention
was shown to proceed smoothly starting from oligophenylene
precursors by stepwise formation of new carbon±carbon
bonds. The relatively high solubility of the intermediate
product 2 as well as of DBPP 5 enabled, in addition to the
The stability of DBPP 5 under electron irradiation is high
enough to also enable direct imaging of thin crystallites by low-
dose high resolution electron microscopy. Fig. 13a shows a
lattice image of DBPP 5 with the strongest observable lattice
fringes corresponding to the 001 re¯ection. Several other lattice
8
84
J. Mater. Chem., 2000, 10, 879±886

View Online
mass spectrometric and the UV/Vis-spectroscopic analysis,
further NMR-spectroscopic support for the structure obtained.
All analytical methods clearly indicate that intramolecular
cyclodehydrogenation is the only reaction occurring under
these oxidative reaction conditions.
zene (1) (1.07 g, 2.00 mmol) in carbon disul®de (500 ml) under
argon for about two days at room temperature. When no
remaining reactant was observed by mass spectrometry the
reaction was quenched by addition of ethanol (500 ml). The
suspension was ®ltered and the residue washed with H O, conc.
2
The reaction products were originally partially crystalline to
microcrystalline. By heat treatment at elevated temperatures it
was possible to obtain well ordered materials. Recrystallization
in the solid state leads to the formation of needle-shaped
crystals from the originally microcrystalline material. However,
these needle-like crystals still exhibit many defects.
At higher temperatures the PAHs can be sublimed using a
temperature gradient to grow macroscopic single crystals. In
case of HBC 3 sublimation led to the formation of needles,
which crystallized in the c-structure. Goddard et al. observed
the same crystal structure by growth of HBC 3 from molten
pyrene indicating that this packing pattern is thermodynami-
cally very favorable.
2 2 2 2 2
HCl, H O, conc. amonia solution, H O, acetone, CS , CH Cl
(about 500 ml in small portions) and dried under vacuum.
Yield: 1.0 g of HBC 3. Sublimation was performed using a
temperature gradient from 480 to 420 ³C (over a range of 5 cm)
2
6
at a pressure of 8610 mbar. Mp w300 ³C. UV/Vis (1,2,4-
trichlorobenzene): lmax (log e)~343 (4.85), 359 (5.13), 387
(4.72), 399 (4.45), 420±450 (small aggregates). FD MS: m/z (%)
z
z
522 (M , 100). LD-TOF MS: m/z (%): 522 (M , 100). EDX:
only carbon.
Dibenzo[fg,ij]phenanthro[9,10,1,2,3-pqrst]pentaphene (DBPP)
. Copper(II) dichloride (584 mg, 4.36 mmol) and alumin-
5
ium(III) trichloride (582 mg, 4.36 mmol) were stirred together
with pentaphenylbenzene (4) (100 mg, 0.218 mmol) in carbon
disul®de (80 ml) under argon for about two days at room
temperature. When no remaining reactant was observed by
mass spectrometry the reaction was quenched by addition of
ethanol (50 ml). The suspension was ®ltered and the residue
washed with H O, conc. HCl, H O, conc. amonia solution,
By sublimation it was also possible to obtain single crystals
of DBPP 5, which crystallizes in the c-motif. Owing to the
Ê
``double-bay area'' in the molecule channels of about 4 A
diameter are present through the crystal. Those channels could
be used to insert other small molecules. Especially, the use of a
doping reagent such as iodine to investigate its in¯uence on the
electronic properties of the material will be the topic of further
experiments.
2
2
2
H O, acetone, CS
2
, CH
2
Cl
2
(about 100 ml in small portions)
and dried under vacuum. Yield: 95 mg of DBPP 5. Sublimation
was performed using a temperature gradient from 410 to 320 ³C
(over a range of 10 cm) at a pressure of 3610 mbar. Mp
2
5
Experimental
1
1
1
w300 ³C. H NMR (500 MHz, C
2 4 2
Cl D , 353 K, H± H
Melting points were determined in open capillary tubes and are
uncorrected. Argon was used for all preparations as an inert
gas. Solvents and starting materials were puri®ed according to
standard procedures, when necessary. H and C NMR
spectra were recorded using a Bruker DRX 500, mass spectra
using a VG Instruments ZAB-2 and a Bruker Re¯ex-
TOF. High-pressure liquid chromatography (HPLC) was
carried out using a Kromail C8, 10 mm column with
COSY): d 7.79 (2H, dd, H-d), 7.84 (2H, dd, H-c), 8.10 (3H,
m, H-g, H-j), 8.84 (2H, d, J~8.0, H-e), 8.94 (2H, d, J~8.0,
3
3
3
H-f), 9.05 (2H, d, J~8.1, H-h), 9.08 (2H, d, J~8.0, H-i), 9.14
3
1
13
3
13
(
2H, d, J~8.1, H-b), 10.34 (1H, s, H-a). C NMR (125 MHz,
Cl , 353 K): d 122.04, 122.32, 122.41, 124.17, 124.19,
24.23, 124.79, 127.14, 127.17, 127.25, 128.20, 128.25, 130.23,
30.44, 130.68, 130.71. UV/Vis (CHCl ): lmax (log e) ~ 304
C
2
4 2
D
1
1
3
(
4
(
4.70), 318 (4.65), 333 (4.77), 363 (4.46), 375 (4.16), 405 (3.65),
z
14 (3.59), 429 (3.45). FD MS: m/z (%) 450 (M , 100), 225
CH
CH
3
CN±CH
Cl ).
2
Cl
2
as eluent (gradient starting with CH
3
CN to
2
2
2z
M
, 25). EDX: only carbon.
Preparations
Crystal structure determination
Phenyldibenzo[fg,ij]phenanthro[9,10,1,2,3-pqrst]pentaphene
. Copper(II) dichloride (4.84 g, 36.0 mmol) and aluminium(III
trichloride (4.80 g, 36.0 mmol) were stirred together with
2
)
The crystal structure of DBPP 5 was determined at room
temperature on a Nonius CAD4 diffractometer with graphite
hexaphenylbenzene (1) (1.07 g, 2.00 mmol) in carbon disul®de
(
monochromated Cu-Ka radiation (l~1.5418 AÊ ). The lattice
parameters were obtained by a least square analysis of the
500 ml) under argon at room temperature for 12 hours before
the reaction was quenched by addition of ethanol (500 ml). The
suspension was ®ltered and the residue washed with dichloro-
methane (100 ml). The combined ®ltrates were dried under
vacuum and the crude product containing 2 as well as
hexaphenylbenzene (1) was puri®ed twice by preparative
HPLC. By slow evaporation of the solvent a few small
crystallites of 2 were obtained before hexaphenylbenzene also
setting angles of 25 re¯ections with hw20³. The structure was
2
0
solved by direct methods (SIR 92) and re®ned by full-matrix
least squares analysis with anisotropic thermal parameters for
the carbon atoms. The hydrogen atoms were placed according
to the binding geometry and re®ned with ®xed isotropic
thermal parameters in the riding mode. 4011 Re¯ections, 2112
observed (Iw3s(I)), empirical correction; re®nement on F; unit
1
1
1
precipitated. H NMR (500 MHz, C
2
Cl
4
D
2
, 353 K, H± H
weight; R~0.047, R ~0.057. Monoclinic, space group C2/c,
w
3
COSY): d 6.93 (2H, dd, H-h), 7.32 (2H, d, J~10.1, H-i), 7.44
a~45.381(1), b~5.1771(7), c~18.266(1), b~106.293(6)³,
3
23
(
1H, dd, H-g), 7.49 (6H, m, H-j, H-k, H-l), 8.06 (2H, dd, H-d),
V~4110.1 AÊ , Z~8, D ~1.453 g cm
CCDC reference number 1145/206.
.
x
3
.12 (1H, t, J~7.9, H-a), 8.61 (2H, d, J~8.1, H-f), 8.83 (2H,
3
8
d, J~7.8, H-e), 8.96 (2H, d, J~7.9, H-c), 9.01 (2H, d,
3
3
See http://www.rsc.org/suppdata/jm/a9/a90841a for crystal-
lographic ®les in .cif format.
3
13
J~7.9, H-b). C NMR (125 MHz, C Cl D , 353 K, J-mod): d
2
4
2
1
1
1
1
21.35, 122.41, 122.51, 123.77, 124.64, 126.94, 127.18, 127.41,
27.87, 130.03, 131.32, 133.25 (tert.-CH), 121.07, 123.95,
25.17, 126.54, 130.24, 130.43, 130.81, 130.95, 132.36, 136.69,
Acknowledgements
45.14 (quat.-C). UV/Vis (CHCl ): l
3
(log e)~311 (3.66), 324
max
(
(
3.98), 338 (4.19), 368 (3.76), 383 (3.20), 411 (2.4), 421 (2.3), 435
z
2.2); FD MS: m/z (%) 526 (M , 100).
This work was supported by the Volkswagen Stiftung and the
Bundesministerium f uÈ r Bildung und Forschung (BMBF). We
thank Dr J. R aÈ der and Dipl. Chem. K. Martin for the LD-TOF
MS measurements and Dr C. Honecker for his help with the
sublimation of DBPP. C.K. thanks the BMBF and Fonds der
Chemischen Industrie for a scholarship.
Hexabenzo[bc,ef,hi,kl,no,qr]coronene (HBC) 3. Copper(II
dichloride (9.68 g, 72.0 mmol) and aluminium(III) trichloride
9.60 g, 72.0 mmol) were stirred together with hexaphenylben-
)
(
J. Mater. Chem., 2000, 10, 879±886
885

View Online
11
R. A. Pascal, Jr., W. D. McMillan, D. Van Engen and R. G. Eason,
J. Am. Chem. Soc., 1987, 109, 4660.
References
1
2
3
4
R. Scholl, C. Seer and R. Weitzenb oÈ ck, Chem. Ber., 1910, 43, 2202;
R. Scholl and C. Seer, Liebigs Ann. Chem., 1912, 55, 111; R. Scholl
and H. Neumann, Chem. Ber., 1922, 55, 118.
E. Clar and D. G. Stewart, J. Am. Chem. Soc., 1953, 75, 2667;
E. Clar, C. T. Ironside and M. Zander, Tetrahedron, 1966, 22,
12 C. K uÈ bel, Ph.D. thesis, Johannes Gutenberg-University, Mainz,
Germany, 1998.
13 The electron microscopic analysis was performed using a Philips
6
CM12 microscope equipped with a LaB cathode operating at
120 kV in low-dose mode at nominally 60 000 times magni®cation.
The electron diffraction patterns were calibrated with TlCl and the
measurements done with a selected area aperture of 40 mm. The
high-resolution images were calibrated using a grid with 2160 lines
per mm. The samples were prepared by ultrasonication of the PAH
in methanol. After precipitation of the larger crystals the
remaining dispersion was sonicated again and the dispersion
dried on a copper grid covered with amorphous carbon ®lm.
14 R. Goddard, M. W. Haenel, W. C. Herndon, C. Kr uÈ ger and
M. Zander, J. Am. Chem. Soc., 1995, 117, 30; J. M. Robertson and
T. Trotter, J. Chem. Soc., 1961, 1280.
3
527; E. Clar and W. Schmidt, Tetrahedron, 1979, 35, 2673.
M. Zander, Chem. Ber., 1962, 92, 2749; M. Zander and
W. H. Franke, Angew. Chem., 1964, 76, 922; Angew. Chem., Int.
Ed. Engl., 1964, 3, 755.
E. Clar, The Aromatic Sextet, John Wiley and Sons, London,
1
972.; H. Hosoya, Top. Curr. Chem., 1990, 153, 255; M. Zander,
Polycyclische Aromaten: Kohlenstoffe und Fullerene, B. G. Teubner,
Stuttgart, 1995.
5
6
(a) S. E. Stein and R. L. Brown, in Molecular Structure and
Energetics, VCH-Verlag, Weinheim, 1987, vol. 2; (b) S. E. Stein
and R. L. Brown, J. Chem. Soc., 1958, 1861.
H. Marsch and M. A. Diez, in Liquid Crystalline and Mesomorphic
Polymers, eds. V. P. Shibaev and L. Lam, Springer-Verlag, New
York, Berlin, 1993; A. Oberlin, in Chemistry and Physics of
Carbon, ed. P. A. Thrower, Marcel Dekker Inc., New York, Basel,
15
Ampoules with a diameter of 2 cm and a length of about 5 or
0 cm were used for the sublimation. 20 to 50 mg of the PAH were
inserted and the sample heated to 200 ³C at a vacuum of
1
22
10
mbar for 2 hours. Afterwards the ampoule was closed
25
under a vacuum of about 10 mbar. A self-made oven which
was heated on one side was used for the sublimation. The
temperature gradient was calibrated with a thermal element.
V. Schomaker and K. N. Trueblodd, Acta Crystallogr., Sect. B,
1
989, vol. 22.
A. Gavezzotti and G. R. Desiraju, Acta Crystallogr., Sect. B, 1988,
4, 427; G. R. Desiraju and A. Gavezzotti, Acta Crystallogr., Sect.
7
8
4
1
6
7
B, 1989, 45, 473.
1968, 24, 63.
V. S. Iyer, M. Wehmeier, J. D. Brand, M. A. Keegstra and
K. M uÈ llen, Angew. Chem., 1997, 109, 1675; Angew. Chem., Int. Ed.
Engl., 1997, 36, 1603; M. M uÈ ller, J. Petersen, R. Strohmeier,
C. G uÈ nther, N. Karl and K. M uÈ llen, Angew. Chem., 1996, 108,
1
The size of the channel was determined as the distance between
atomic centers of hydrogen atoms on opposite sides of the cavity
with twice the van der Waals radius for hydrogen subtracted.
The electron diffraction pattern was simulated using the crystal
1
8
9
47; Angew. Chem., Int. Ed. Engl., 1996, 35, 886.
(a) E. Clar, C. T. Ironside and M. Zander, J. Chem. Soc., 1959,
42; (b) E. Clar and M. Zander, J. Chem. Soc., 1958, 1861;
c) A. Halleux, R. H. Martin and G. S. D. King, Helv. Chim. Acta,
958, 129, 1177.
2
diffraction module of the program Cerius Version 3.5 by
Molecular Simulations Inc.
9
0
1
(
1
1
2
9
0
The Fourier transformation was performed using the program
Analysis 2.11 by Soft-Imaging GmbH.
SIR 92, J. Appl. Crystallogr., 1994, 27, 435.
1
The AM1 structure optimization was performed using Spartan 4.0
by Wavefunction Inc., Irvine, CA, starting with a planar central
aromatic core and the free phenyl ring orthogonal to it as well as at
an angle of 45³.
Paper a908941a
8
86
J. Mater. Chem., 2000, 10, 879±886