Superaromatic terpyridines: Hexa-peri-hexabenzocoronenes with tridentate functionality

Article abstract of DOI:10.1021/jo902526u

Chemical Equation Presented Two superaromatic terpyridine ligands (1 and 2) incorporating a hexa-peri-hexabenzocoronene (HBC) unit at the 4′-position have been, prepared. In 1, the terpyridine and the HBC domains are directly fused, while in 2, they are separated by an acetylene linker. Also presented is the synthesis and characterization of several novel HBC derivatives, including 2-iodo-5,8,11,14,17-penta-tert-butyl-hexa-peri- hexabenzocoronene (7), a valuable synthetic intermediate. Different, synthetic routes to 1 and 2 are employed, and two alternative methods resulted in excellent yields of 2. The optical properties of both novel terpyridines are examined using UV-visible absorption and emission spectroscopy. The single-crystal X-ray structures of 7 and a precursor, 4-iodo-4′-tert- butylphenylacetylene (5), are discussed.

Full text of DOI:10.1021/jo902526u

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Superaromatic Terpyridines: Hexa-peri-hexabenzocoronenes with
Tridentate Functionality
Frances A. Murphy and Sylvia M. Draper*
School of Chemistry, Trinity College Dublin, D2, Ireland
smdraper@tcd.ie
Received November 27, 2009
Two superaromatic terpyridine ligands (1 and 2) incorporating a hexa-peri-hexabenzocoronene
(HBC) unit at the 40-position have been prepared. In 1, the terpyridine and the HBC domains are
directly fused, while in 2, they are separated by an acetylene linker. Also presented is the synthesis and
characterization of several novel HBC derivatives, including 2-iodo-5,8,11,14,17-penta-tert-butyl-
hexa-peri-hexabenzocoronene (7), a valuable synthetic intermediate. Different synthetic routes to 1
and 2 are employed, and two alternative methods resulted in excellent yields of 2. The optical
properties of both novel terpyridines are examined using UV-visible absorption and emission
spectroscopy. The single-crystal X-ray structures of 7 and a precursor, 4-iodo-40-tert-butylphenyla-
cetylene (5), are discussed.
Introduction
related compounds are expected to provide useful components
in the area of molecular electronics and optoelectronics.2,3
The first generation of nitrogen-containing HBC deriva-
tives (or heterosuperbenzenes, HSBs) were synthesized as a
family of pyrimidine-containing polyaromatic compounds.4
The addition of ortho-nitrogen atoms provided a site for
bidentate coordination to metal centers in a manner analo-
gous to 2,20-bipyridine.5-7 The result was the marriage of the
intriguing properties of HBC with the exciting photophysical
Hexa-peri-hexabenzocoronene (HBC) with 13 fused ben-
zene rings is a large polycyclic aromatic hydrocarbon and, as
such, has been the focus of considerable research. Large disk-
like HBC derivatives exhibit interesting electronic and optical
properties resulting from their extensive electron delocaliza-
tion and intrinsic chemical stability.1 In addition, such mole-
cules can aggregate to form columnar stacks. Analogues of
graphite (itself a highly efficient organic conductor), HBC, and
(1) Haley, M. M.; Tykwinski, R. R. Carbon-Rich Compounds: From
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2494.
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Tagawa, S.; Taniguchi, M.; Kawai, T.; Aida, T. Science 2006, 314, 1761–
1764.
(4) Draper, S. M.; Gregg, D. J.; Madathil, R. J. Am. Chem. Soc. 2002,
124, 3486–3487.
(5) Draper, S. M.; Gregg, D. J.; Schofield, E. R.; Browne, W. R.; Duati,
M.; Vos, J. G.; Passaniti, P. J. Am. Chem. Soc. 2004, 126, 8694–8701.
(6) Gregg, D. J.; Bothe, E.; Hofer, P.; Passaniti, P.; Draper, S. M. Inorg.
Chem. 2005, 44, 5654–5660.
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1862 J. Org. Chem. 2010, 75, 1862–1870
Published on Web 02/19/2010
DOI: 10.1021/jo902526u
r
2010 American Chemical Society

Murphy and Draper
JOCArticle
SCHEME 1. Synthesis of HBC-tpy 1, Its Uncyclized Precur-
sor 4, and the Terpyridine-Substituted Diphenylacetylene 3a
FIGURE 1. HBC-terpyridine ligands 1 and 2.
and electrochemical properties of Ru(II) trisdiimine metal
complexes. Here, in an extension to this emerging field, we
present the synthesis, characterization, and photophysical
study of HBC derivatives coupled to 2,20;60,200-terpyridine
(Figure 1). Ligand 1 consists of a terpyridine unit substituted
at the 40-position with a penta-tert-butyl-substituted HBC.
The tert-butyl groups confer increased solubility to large
planar molecules by reducing the propensity for aggregation
in solution. Ligand 2 differs from 1 in that the terpyridine
unit and the HBC platform are separated by an acetylene
bridge. 1 and 2 offer direct comparison for examining the
ability of the acetylene linker to promote enhanced electronic
communication between the tpy and HBC units, a feature
known to prolong the excited-state lifetimes in Ru(II) tpy
complexes.8 There is one example of an acetylene-HBC
derivative with long-chain substituents that has been used to
prepare metal complexes: a Pt(II) acetylide, which displayed
intriguing photophysical properties.9
aConditions: (i) triethylamine, toluene, Pd(PPh3)2Cl2 (6 mol %), CuI (6
mol %), 70 °C, 4 h, 61%; (ii) benzophenone, 350 °C, 3.5 h, 57%; (iii)
CH2Cl2, FeCl3 (25 equiv in CH3NO2), 24 h, 86%.
The tpy domain was incorporated into a hexaphenylbenzene
precursor, thus requiring subsequent cyclodehydrogenation
in the case of 1, while the appropriate tpy substituent was
coupled to a preformed iodine-functionalized HBC unit in
the case of 2.
Taking the first strategy, the construction of the novel
acetylene tpy unit, 40-[4-(4-tert-butylphenyl)-ethynylphenyl]-
2,20;60,200-terpyridine (3, Scheme 1), was needed and was
achieved via the coupling of 40-(4-bromophenyl)-2,20;60,200-
terpyridine with 4-tert-butylphenylacetylene under standard
Sonogashira conditions. Recrystallization of the product
from hot ethanol afforded 3 in 42% yield; however, column
chromatography allowed a further fraction of the product to
be obtained for a total combined yield of 61%. In order to
generate the hexaphenylbenzene 4, acetylene 3 was reacted
with 2,3,4,5-tetra-(4-tert-butylphenyl)cyclopenta-2,4-dienone
via a Diels-Alder [2 þ 4] cycloaddition in a benzophenone
melt. 4 was isolated in 57% yield following column chroma-
tography. Oxidative cyclodehydrogenation of 4 in methylene
chloride involved the addition of excess FeCl3 dissolved in
nitromethane (Scheme 1(iii)). Following a short workup, col-
umn chromatography on silica gel provided 1 as a yellow solid
in excellent yield. Although 1 was found to show relatively poor
solubility in most common solvents, it was sufficiently soluble
in CDCl3 for characterization by 1H NMR spectroscopy.
For terpyridine-substituted HBC 2, which incorporates an
acetylene bridge, a key precursor to the target compound is
iodine-substituted HBC 7 (Scheme 2). The first step to iodo-
HBC is the preparation of 4-iodo-40-tert-butylphenylacety-
lene (5) from 4-tert-butylphenylacetylene and p-diiodoben-
zene under Sonogashira reaction conditions (Scheme 2(i)); 5
Terpyridine (tpy) ligands readily form coordination com-
plexes favoring the octahedral geometry of group 8 metals such
as Fe(II) and Ru(II). Bis-tpy metal complexes, unlike polypyr-
idyl metal complexes bearing three bidentate ligands, are
achiral and non-enantiomeric. The quest to design original
and functional tpy ligands for metal complexation has
prompted the development of a number of synthetic strate-
gies.10 Ligands 1 and 2 presented herein contain the largest
fused aromatic substituent of any known tpy derivative. As
“superaromatic” ligands, these compounds are expected to
furnish metal complexes displaying optoelectronic properties
arising from the extended HBC platforms and, in the case of 2,
enhanced electronic communication via the acetylene bridge.
While many HBC derivatives have been prepared, there are no
examples with pendant polypyridyl ligands and few studies that
have focused on their important photophysical properties.
Results and Discussion
Synthesis: The syntheses of compounds 1 and 2 were
different and built upon two separate synthetic strategies.
(8) Hissler, M.; Harriman, A.; Khatyr, A.; Ziessel, R. Chem.;Eur. J.
1999, 5, 3366–3381.
(9) Kim, K. Y.; Liu, S.; Kose, M. E.; Schanze, K. S. Inorg. Chem. 2006, 45,
2509–2519.
(10) Schubert, U. S.; Hofmeier, H.; Newkome, G. R. Modern Terpyridine
Chemistry; Wiley-VCH: Weinheim, Germany, 2006.
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SCHEME 2. Synthesis of HBC-Actpy 2 and Its Precursorsa
aConditions: (i) diisopropylamine, THF, Pd(PPh3)2Cl2 (5 mol %), CuI (5 mol %), 24 h, 73%; (ii) benzophenone 350 °C, 2 h, 73%; (iii) CH2Cl2, FeCl3
(25 equiv in CH3NO2), 12 h, 90%; (iv) diisopropylamine, THF, Pd(PPh3)2Cl2 (5 mol %), CuI (5 mol %), 24 h, 94%; (v) THF, methanol, KF, 12 h, 100%;
(vi) toluene, diisopropylamine, Pd(PPh3)4 (5 mol %), 70 °C, 48 h, 78%; (vii) benzene, diisopropylamine, Pd(PPh3)4 (5 mol %), 70 °C, 24 h, 85%.
is obtained in 73% yield following column chromatography.
5 was then reacted with 2,3,4,5-tetra-(4-tert-butylphenyl)-
cyclopenta-2,4-dienone via a Diels-Alder [2 þ 4] cycloaddi-
tion (Scheme 2(ii)) to provide the 4-iodophenyl-substituted
hexaphenylbenzene 6 in 73% yield following a chromato-
graphic workup. The oxidative cyclodehydrogenation of 6
was then carried out to furnish iodo-HBC 7; this was
achieved by dissolving the uncyclized precursor in methylene
chloride and adding an excess of FeCl3 dissolved in nitro-
methane (Scheme 2(iii)). Addition of the reaction mixture to
an excess of methanol caused the precipitation of 7 as a
yellow solid.
the aromatic region, while 1 and 2 have in addition a further
four aromatic signals due to the terpyridine protons (see
Supporting Information).
UV-Vis Absorption Spectroscopy: Absorbance spectra in
THF solution were measured for iodo-HBC 7 and TMS-
acetylene HBC 8 because this solvent has been reported to
minimize aggregation in related compounds.9 The spectra
show features typical of other HBCs with a weak onset
absorption at ca. 425 nm followed by three band maxima.11
For 7, these appear at 392, 361, and 345 nm, while for TMS-
acetylene HBC 8, there is a slight red shift resulting in
absorptions at 394, 364, and 347 nm (Figure 2).
Iodo-HBC 7, a useful synthon for further functionaliza-
tion of the HBC platform, was used to generate the target
terpyridine ligand 2 via two different routes (Scheme 2). One
route involves the introduction of an acetylene functional
group using Sonogashira conditions to provide compound 8
and subsequently 9. The coupling reaction (Scheme 2(iv))
proceeds smoothly at room temperature, and 8 was isolated
in excellent yield after a short column. The TMS group on 8
was removed by stirring the compound in a mixture of THF
and methanol overnight with KF to provide acetylene-HBC
9 in quantitative yield. 9 was reacted with triflato-tpy to
afford 2 (Scheme 2(vi)). Alternatively, the direct Sonogashira
coupling of 7 to 40-ethynyl-2,20;60,200-terpyridine can be
employed to synthesize the same target compound
(Scheme 2(vii)). Both synthetic routes to 2 are high-yielding,
and since 2 is poorly soluble, it can be isolated from the
reaction mixture via filtration.
Although HBC-Actpy (2) is less soluble than the other
HBC fragments presented and HBC-tpy (1) is soluble only in
excess solvent, dilute solutions suitable for UV-visible
spectroscopic measurements could be obtained. 1 dissolves
completely in THF to give a clear solution at a concentration
of 5 ꢀ 10-6 M. 2 dissolves slowly at the same concentration,
taking up to 24 h for the solution to become completely
transparent. For 1, there are three observable maxima in the
absorption spectrum that are due to the HBC chromophore,
appearing at 393, 363, and 346 nm (similar to 7 and 8). In
addition, intense tpy-based π-π* and n-π* absorptions
appear in the UV region at 243 and 228 nm (Figure 2). For 2,
the three HBC bands appear at 395, 367, and 349 nm, while
the tpy-based absorptions are at 243 and 228 nm. In addi-
tion, there is a moderately intense band at 417 nm for 2,
which when observed in σ-acetylide Pt(II) complexes of
dodecyl HBC was assigned to the Pt-acetylide unit.9
A
NMR Spectroscopic Analysis: NMR spectroscopy was a
useful tool for the characterization of the HBC compounds
and their precursors. Due to the symmetry in the molecules,
the 1H NMR spectra of 7, 8, and 9 all show just six singlets in
(11) Wang, Z.; Tomovic, Z.; Kastler, M.; Pretsch, R.; Negri, F.;
€
Enkelmann, V.; Mullen, K. J. Am. Chem. Soc. 2004, 126, 7794–7795.
1864 J. Org. Chem. Vol. 75, No. 6, 2010

Murphy and Draper
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FIGURE 3. Room-temperature luminescence spectrum of
(5ꢀ10-6 M in THF).
8
band (∼450-650 nm). The most intense peak within the
emission band is observed at λmax,em = 472 nm, but the lower
energy peaks at 493 and 502 nm are relatively less intense
than the corresponding peaks in 1. The emission band of 2
appears to extend toward lower energy wavelengths (>600 nm)
with a more prominent tail than that seen for 1. The shape
and position of the emission maxima remain constant when
the excitation wavelength is varied, and the most intense
emission appears on excitation which is coincident with the
maximum HBC absorption (λmax,abs=367 nm). When the
excitation wavelength used is coincident with the intense
high-energy tpy absorptions (243 and 228 nm), emission
from the HBC unit is observed but at lower intensity than
when the HBC unit is excited directly.
For 1 and 2, we have established that the most intense
fluorescence observed for both molecules arises from excita-
tion at the most strongly absorbing band of the HBC plat-
form (λmax,abs = 363 nm for 1 and 367 nm for 2). For both
compounds, the terpyridine unit absorbs strongly at 228 and
243 nm; excitation at these wavelengths also results in
emission from the lowest excited state on the HBC platform.
The spectra presented in Figure 4 and Figure 5 reveal that the
emission observed from excitation of the tpy unit of 2 is
comparatively more intense than that observed for 1. This is
summarized in Table 1, which compares the relative inten-
sities of the λmax emission peaks for 1 and 2 when the
compounds are excited at their most intense HBC absorption
or at the wavelengths of the tpy absorptions.
These proportionalities (Table 1) reveal information about
the relative ease of energy transfer from the tpy unit to the
lowest emitting excited state on the HBC unit and suggest that
a more efficient transfer of energy between the two domains is
possible for 2 than for 1. This can be attributed to the presence
of the acetylene bridge which facilitates electron and energy
transfer between the two components, resulting in a more
efficient internal conversion process in 2.
The fluorescence quantum yields of 1 and 2 were measured
in THF by comparison with a solution of the well-studied
standard coumarin 153 in methanol.12 The quantum yields
were found to be approximately 0.056 and 0.071 for 1 and 2,
respectively. The excited-state lifetimes of HBC-terpyridine
ligands 1 and 2 were measured at room temperature in
THF at concentrations of approximately 1ꢀ10-6 M using a
single-photon photomultiplier detection system. The excita-
tion source used was a Hamamatsu picosecond light pulser
FIGURE 2. UV-vis absorption spectra of HBCs 7 (black line) and
8 (red line) and HBC-terpyridine compounds 1 (blue line) and 2
(green line) in THF (5 ꢀ 10-6 M).
similar band can be identified on the spectrum of 2 and as a
shoulder in the same position for 1.
Emission Spectroscopy: The room-temperature emission
spectra of the HBC derivatives were recorded in THF at
dilutions of 5 ꢀ 10-7 to 1 ꢀ 10-6 M, and both 7 and 8 were
excited at the wavelength of their maximum absorption
(λmax,abs = 361 nm for 7 and 364 nm for 8). 8 emits strongly
at λmax,em =470 nm (Figure 3); however, iodo-HBC 7 is
essentially nonemissive with a very weak band centered at
λ
max,em = 495 nm. This is expected since heavy atoms such as
iodine perturb the excited-state properties of aromatic chro-
mophores through a spin-orbital coupling mechanism
(heavy atom effect).
Luminescence spectra were recorded for HBC-tpy (1) and
HBC-Actpy (2) in THF at concentrations of 1 ꢀ 10-6 M. For
both compounds, the spectra consist of a characteristic
broad band at ∼450-600 nm, having a complex vibronic
structure, and resemble the emission spectrum obtained for
8. For 1, the most intense peak within this band occurs at
469 nm, but two overlapping peaks at 489 and 497 nm also
dominate the spectrum (Figure 4). The shape and position of
the emission bands remain unchanged when different excita-
tion wavelengths are used, with the most intense emission
being observed when the excitation wavelength is coincident
with the maximum HBC absorption (λmax,abs = 363 nm).
When the strongly absorbing tpy fragment is excited at the
position of its maximum absorptions (λmax,abs =228 and
243 nm), the luminescence detected is identical in shape
and position to that observed upon irradiation at the HBC
absorptions; however, the detected emission appears at
much lower intensity (Figure 4).
This suggests that there is sufficient communication be-
tween the terpyridine and HBC units to allow luminescence to
be observed upon excitation of the tpy unit and that the lowest
emitting excited state is localized on the HBC fragment.
The luminescence spectrum obtained for HBC-Actpy (2) is
shown in Figure 5 and also consists of a broad structured
(12) Lewis, J. E.; Maroncelli, M. Chem. Phys. Lett. 1998, 282, 197–203.
J. Org. Chem. Vol. 75, No. 6, 2010 1865

Murphy and Draper
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TABLE 2. Photophysical Data for 1 and 2a
b
Φem
τ (ns)
emission (λmax/nm)
((0.01)
((0.03)
1
2
469
472
489
493
497
502
522
526
0.056
0.071
20.32
19.92
aAll measurements were made in argon-degassed THF solutions at
298 K. bFluorescence quantum yields were measured relative to cou-
marin 153 in methanol, Φem = 0.89.12 Measurements were made on
solutions with matched optical density at 395 nm.
FIGURE 4. Luminescence spectra for 1 recorded at various excita-
tion wavelengths in THF (1 ꢀ 10-6 M).
FIGURE 6. AB pairs of molecules in the crystal structure of 5,
showing the -CH-π interaction between the iodophenyl ring in A
and the triple bond in B.
FIGURE 5. Fluorescence spectra for 2 recorded at various excita-
tion wavelengths in THF (1 ꢀ 10-6 M).
(A and B) in the asymmetric unit and two A and B pairs in the
unit cell. The AB pairs of molecules are arranged in rows of
unidirectional molecules (Figure 6). In A, the dihedral angle
between the 4-iodophenyl ring and the 4-tert-butylphenyl
ring (33.2°) is different from that in B (54.3°). The acetylene
triple bond length is essentially the same in both mole-
TABLE 1. Comparative Emission Intensities for 1 and 2 at Different
Excitation Wavelengthsa
proportion of λmax HBC emission at various excitation λ
λmax emission
λex
=
max,abs HBCb
λex =
243 nm
λex =
228 nm
λ
˚
˚
cules (A, 1.202(6) A; B, 1.200(6) A). Each AB dimeric unit
is staggered with respect to the next, with a near-linear
CH(phenyl B unit)-π(CꢁC A unit) interaction between adjacent
1 (469 nm)
2 (472 nm)
1.0
1.0
0.27
0.61
0.13
0.35
aAll measurements were made in argon-degassed THF solutions at
˚
AB units (2.95 A and the CH-π 171.0°) .
298 K. bThe λmax,abs = 363 nm for 1 and 367 nm for 2.
Both above and below the linear arrangement of dimeric
units shown in Figure 6, an identical row of molecules is
present orientated in the opposite direction such that the
iodine substituents of the flanking rows are aligned with the
tert-butyl groups of the first. Figure 7 shows this as viewed
along the axis of the iodine substituents in Figure 6. The rows
of AB repeating units are held together by weak interactions
between adjacent molecules (e.g., CH(phenyl A unit)-π(phenyl B unit
laser at 371 nm, and emission was detected at λmax,em = 469 nm
for 1 and 472 nm for 2. A decay profile of the excited state was
obtained, and this was fitted to a single exponential decay
model, obtaining an excellent fit for both ligands. The room-
temperature excited-state lifetime for 1 was calculated to be
20.32 ( 0.03 ns. The goodness of fit between the observed
decay and the single exponential model was evaluated by
considering the χ2 value, which was found to be 1.027. For 2,
the room-temperature excited-state lifetime was estimated in
the same manner and was found tobe19.92( 0.03 ns. Clearly,
the lowest excited state at room temperature on the HBC
platform is relatively unaffected by the presence of the acety-
lene unit. A summary of the emission wavelengths, quantum
yields, and fluorescence lifetimes for ligands 1 and 2 is
presented in Table 2.
Crystal Structures: Crystals suitable for single-crystal
X-ray diffraction were obtained for iodo-acetylene 5 and
iodo-HBC 7 by slow evaporation of hexane and methylene
chloride solutions, respectively. The iodo-acetylene units of 5
undergo self-assembly by close-packing with the exclusion of
solvent molecules. The molecule crystallizes in a triclinic
system (P1) with two non-identical forms of the compound
˚
2.96 A with a CH-π angle of 157.7°).
Iodo-HBC 7 crystallizes in the C2/c space group with one
molecule in the asymmetric unit. There are eight equivalents of
7, and no solvent molecules in the unit cell. The crystal structure
shows the formation of head-to-tail dimers (Figure 8a). The
benzene rings of the aromatic platforms are offset so that the
center of each six-membered ring is precisely superimposed on a
carbon atom in the underlying molecule. This behavior is
analogous to that observed in the ideal crystal structure of
graphite and is referred to as Bernal stacking;13 it also features
in the crystal structure of hexa-tert-butyl HBC.14
(13) Ebbesen, T. W. Carbon Nanotubes: Preparation and Properties; CRC
Press: Boca Raton, FL, 1997.
€
(14) Herwig, P. T.; Enkelmann, V.; Schmelz, O.; Mullen, K. Chem.;Eur.
J. 2000, 6, 1834–1839.
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Murphy and Draper
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FIGURE 9. Arrangement of rows of dimers in the crystal structure
of 7.
FIGURE 7. Packing of molecules in the crystal structure of 5
showing the CH-π interaction between adjacent molecules with
A and B configuration.
FIGURE 10. Expanded crystal packing structure of iodo-HBC (7)
˚
showing the I-I interactions (3.83 A) between the dimeric units.
occupancy (80:20) was resolved by the PART command.15
A C atom (C6) of another tert-butyl group exhibits a non-
positive definite (even after repeated data collection at low
temperature) and was refined isotropically.
Interestingly, each iodo-HBC molecule within the dimer
interacts with another iodo-HBC molecule via a rarely
˚
observed iodine-iodine interaction measuring 3.83 A
(Figure 10). This compares to the sum of van der Waals
˚
radii for I-I at 3.96 A and is relatively weak. The extended
crystal structure therefore can be considered as interpene-
trating rows of dimers twisted at an angle of 55.8°, whose
orientation is influenced by the presence of weak iodine-
iodine interactions.
FIGURE 8. X-ray crystal structure of 7 showing the dimeric units
formed (H atoms omitted for clarity). Bernal stacking as viewed
from above the dimer (a) and the separation between the two
molecules as viewed along the plane of 7 (b).
Conclusion
The synthesis of a number of novel HBC derivatives and
their precursors has been presented, including two unique
terpyridine ligands (1 and 2) that contain the extended
aromatic HBC core as a pendant group. Together, these
compounds boast the largest fused aromatic units yet ap-
pended to a terpyridine. The synthesis of 1 required prior
formation of a nonplanar hexaphenylbenzene precursor (4)
to which oxidative cyclodehydrogenation was applied. Two
alternative syntheses were presented for 2, both requiring the
synthetically useful iodo-HBC (7). The X-ray crystal struc-
tures of 7 and its precursor, 4-iodo-40-tert-butylphenylace-
tylene (5), were obtained. The crystal structure of 7 features
the replication of discrete dimers which display Bernal
stacking and unusual iodine-iodine interactions. 7 readily
The interplanar distance between the iodo-HBC dimers,
˚
calculated from the aromatic core, is found to be 3.41 A. This
is remarkably close to the interplanar distance in ideal graphite
(3.35 A)13 and closer than that observed in the crystal structure
˚
˚
of hexa-tert-butyl HBC (3.44 A). The molecules are slightly
distorted from planarity at the periphery due to steric interac-
tion between the tert-butyl groups of adjacent molecules
(Figure 8b). The largest deviation of the central atoms on the
tert-butyl groups from the plane calculated from the aromatic
˚
core is found to be 0.78 A (found for the tert-butyl group closest
to the iodine substituent which is projected over the aromatic
platform of the neighboring molecule). Pairs of unidirectional
dimers (and therefore rows of dimers) are offset from each
€
(15) Muller, P.; Herbst-Irmer, R.; Spek, A. L.; Schneider, T. R.; Sawaya,
˚
other by 5.32 A (Figure 9). The tert-butyl group, situated
para to the iodine substituent, is disordered, and the partial
M. R. Crystal Structure Refinement: A Crystallographer0s Guide to SHELXL;
Oxford University Press Inc.: New York, 2006.
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Murphy and Draper
JOCArticle
undergoes palladium-catalyzed Sonogashira coupling reac-
tions, forming ligand 2 and the novel acetylene-containing
HBC derivatives 8 and 9.
collected, and lifetimes were determined from the observed
decays. The decay was fitted using a first order exponential
decay model (fit = A þ B ꢀ e(-t/τ1), where B is the pre-
exponential factor and τ1 is the lifetime of the excited state),
and the goodness of fit was evaluated for each result by
considering the χ2 values and inspecting the residual plots.
X-ray Crystallography: A suitable crystal of each compound 5
and 7 was selected and mounted using inert oil on a 0.30 mm
quartz fiber tip and immediately placed on the goniometer head
in a 123K N2 gas stream. The structures both converged to a
reasonable R factor. Further details are provided in the Sup-
porting Information.
All of the HBC compounds described were examined
spectroscopically and displayed characteristic absorption
and emission profiles. 1 and 2 were found to have excited-
state lifetimes of ca. 20 ns, with 2 showing the higher
quantum yield. The relative luminescence intensity detected
from the HBC unit of 1 upon irradiation of the tpy absorp-
tions was much lower than for 2, suggesting that the acet-
ylene bridge allows more efficient energy transfer between
the two parts of the molecule.
Compounds 1 and 2 have ligand functionality and offer
the exciting possibility of creating metal complexes which
incorporate the properties of a graphite-like HBC chromo-
phore. Such complexes offer intriguing opportunities for the
fabrication of functional nanoscale devices and for self-
assembly.16 The preparation of a range of complexes incor-
porating such systems is ongoing and heralds another chap-
ter in tpy-HBC chemistry.
40-[4-(4-tert-Butylphenyl)ethynylphenyl]-2,20;60,200-terpyridine
(3): 40-(4-Bromophenyl)-2,20:60,200-terpyridine (250 mg, 6.44 ꢀ
10-4 mol) was dissolved in freshly distilled toluene (5 mL) and
triethylamine (2 mL). CuI (7.35 mg, 3.86 ꢀ 10-5 mol) and
[Pd(PPh3)2Cl2] (27 mg, 3.86ꢀ10-5 mol) were added, and the
mixture was degassed. 4-tert-Butylphenylacetylene (0.174 mL,
9.66ꢀ10-4 mol) was added, and the solution was heated at
70 °C for 4 h. The brown reaction mixture was cooled, after
which H2O (50 mL) and DCM (50 mL) were added. The organic
layer was separated, dried over MgSO4, and evaporated to
dryness. Some crystals of the product were isolated by recrys-
tallizing from EtOH (125 mg, 42%). The remainder of the
product was purified via column chromatography on silica
gel, first using diethyl ether followed by a mixture of diethyl
ether, MeOH, and 10% aq NH3 (1:1:1). This provided a further
Experimental Section
General Methods: 2,3,4,5-Tetra-(4-tert-butylphenyl)cyclopenta-
2,4-dienone,17 40-[{(trifluoromethyl)sulfonyl}oxy]-2,20;60,200-ter-
pyridine,18 40-ethynyl-2,20;60,200-terpyridine,19 and 40-(4-bromo-
phenyl)-2,20;60,200-terpyridine20 were prepared following the literature
procedures. All reactions were carried out under inert conditions
with dry solvent, freshly distilled under anhydrous conditions.
Accurate mass spectra were referenced against leucine enkephalin
(555.6 g mol-1) and reported within 5 ppm for electrospray mass
spectra. MALDI-TOF mass spectra were recorded using an R-
cyano-4-hydroxycinnamic acid matrix, and accurate mass spectra
1
57 mg of product, total yield being 182 mg (61%): H NMR
(CDCl3) δ 8.78 (m, 4 H), 8.71 (d, 3J = 7.53 Hz, 2 H, H3), 7.93 (m,
4 H, H2a, H4), 7.69 (d, 3J = 8.53 Hz, 2 H, H3a), 7.53 (d, 3J =
8.03 Hz, 2 H), 7.41 (m, 3J = 8.54 Hz, 4 H), 1.36 (s, 9 H, -CH3
t-butyl); 13C NMR (CDCl3) δ 155.9 (2 C, quart.), 155.8 (2 C,
quart.), 151.6 (1 C, quart.), 149.3 (1 C, quart.), 148.9 (2 C,
-CH), 137.7 (1 C, quart.), 136.9 (2 C, -CH), 132.0 (2C, -CH),
131.3 (2C, -CH), 127.1 (2C, -CH), 125.3 (2C, -CH), 124.2
(1C, quart.), 123.8 (2C, -CH), 121.3 (2C, -CH), 119.9 (1C,
quart.), 118.6 (2C, -CH), 91.0 (1C, -CtC-), 88.3 (1C,
-CtC-), 34.7 (1C, -C(CH3)3), 31.0 (3C, -C(CH3)3); ES-MS
(THF) m/z = 466.2286 [M þ H]þ, calcd for C33H28N3 466.2283;
IR ν (cm-1) 2957 (m), 2903 (m), 2865 (m), 2217 (w), 1601 (m),
1583 (s), 1565 (s), 1541 (m), 1518 (s), 1465 (s), 1441 (m), 1409 (m),
1386 (s), 1263 (m), 1105 (m), 1075 (m), 1038 (m), 989 (m), 891
(m), 833 (s), 789 (s), 735 (s), 682 (m), 659 (s).
were referenced against [Glu1]-fibrinopeptide B (1570.6 g mol-1
)
and reported within 5 ppm. Nuclear magnetic resonance spectra
were recorded in deuterated acetonitrile or chloroform with a
400 MHz spectrometer at the following frequencies: 400.13 MHz
1
for H and 100.6 MHz for 13C or a 600 MHz spectrometer at
600.13 MHz for 1H and 150.6 MHz for 13C. The signals for 1H and
13C spectra were referenced to TMS at δ 0.0 ppm, and coupling
constants were recorded in hertz (Hz) to two decimal places. All
1-D 1H and 13C spectra were recorded using a 400 MHz spectro-
meter. 13C signals were assigned with the aid of DEPT 145 and
DEPT 90 experiments. Two-dimensional correlation spectra were
recorded on a 400 or 600 MHz spectrometer and were employed to
assign the 1H and 13C peaks. Homonuclear correlation spectros-
copy was performed using TOCSY or 1H-1H COSY experiments,
and heteronuclear correlation spectroscopy was performed using
HSQC, HMQC, or HMBC (long-range) experiments.
(1,10-Biphenyl)-2,3,4,5,6-(40-tert-butylphenyl)-40-[2,20:60,200-
terpyridin]-40-yl- (4): 3 (100 mg, 2.15 ꢀ 10-4 mol) and 2,3,4,5-
tetra(4-tert-butylphenyl)cyclopenta-2,4-dienone (131 mg,
2.15 ꢀ 10-4 mol) were combined with 1.75 g (9.60 ꢀ 10-3 mol)
of benzophenone in a 10 mL round-bottom flask. The mixture
was heated on a sand microburner to 350 °C for 3.5 h under N2
and then allowed to cool slowly to room temperature. Two
milliliters of DCM was added to dissolve the reaction mixture,
and this solution was added to a conical flask containing MeOH
(20 mL). The mixture was heated to remove the DCM and
cooled in the freezer at -10 °C to allow precipitation of an off-
white solid. The solid was removed via suction filtration and
washed well with MeOH (15 mL) before recrystallizing from hot
MeOH to afford 106 mg (47%) of the product. The remaining
mother liquor containing some product was purified via column
chromatography on silica gel using ethyl acetate, increasing the
gradient of triethylamine from 0 to 10% to afford a further
22 mg of the product; total yield 128 mg (57%): 1H NMR
Photophysical Measurements: All photophysical studies were
carried out with solutions contained within 1 ꢀ 1 cm2 quartz
cells in HPLC grade solvents and were degassed using argon
bubbling. Emission quantum yields were measured in reference
to coumarin 153 in methanol.12 Excited-state lifetimes were
measured using a single-photon photomultiplier detection sys-
tem using a picosecond light pulser laser with a 371 nm excita-
tion wavelength. Five thousand laser pulses were used in the
experiment with a pulse width of 200 ns; the resulting data were
3
(CDCl3) δ 8.70 (d, 3J = 7.53 Hz, 2 H), 8.62 (d, J = 8.03 Hz,
ꢁ
(16) Murphy, F. A.; Suarez, S.; Figgemeier, E.; Schofield, E. R.; Draper,
S. M. Chem.;Eur. J. 2009, 15, 5740–5748.
2 H), 8.59 (s, 2 H, H30), 7.84 (dd, 3J = 8.03 Hz, 2 H), 7.46 (d,
3J = 8.03 Hz, 2 H), 7.32 (dd, 3J = 4.51 Hz, 2 H), 7.06 (d, 3J =
8.03 Hz, 2 H), 6.86 (m, 10 H), 6.73 (m, 10 H), 1.13 (s, 45 H,
-C(CH3)3); 13C NMR (CDCl3) δ 156.2 (quart.), 155.5 (quart.),
150.4 (quart.), 148.9 (2C, -CH), 147.8 (quart.), 147.5 (quart.),
147.4 (quart.), 142.4 (quart.), 140.8 (quart.), 140.7 (quart.),
(17) Gregg, D. J.; Ollagnier, C. M. A.; Fitchett, C. M.; Draper, S. M.
Chem.;Eur. J. 2006, 12, 3043–3052.
(18) Potts, K. T.; Konwar, D. J. Org. Chem. 1991, 56, 4815–4816.
(19) Grosshenny, V.; Romero, F. M.; Ziessel, R. J. Org. Chem. 1997, 62,
1491–1500.
(20) Wang, J.; Hanan, G. Synlett 2005, 1251–1254.
1868 J. Org. Chem. Vol. 75, No. 6, 2010

Murphy and Draper
JOCArticle
140.2 (quart.), 139.1 (quart.), 137.9 (quart.), 137.7 (quart.),
137.0 (2 C, -CH), 134.4 (quart.), 132.2 (2 C, -CH), 131.1
(-CH phenyls), 131.1 (-CH phenyls), 125.5 (2 C, -CH), 123.8
(2 C, -CH), 123.4 (-CH phenyls), 123.11 (-CH phenyls),
123.05 (-CH phenyls), 121.3 (2 C, -CH), 118.7 (2 C, -CH),
34.14 (quart., -C(CH3)3), 34.06 (quart., -C(CH3)3), 31.2
(-CH, -C(CH3)3); ES-MS (THF) m/z = 1046.6367 [M þ
H]þ, calcd for C77H80N3 1046.6352; IR ν (cm-1) 2960 (s), 2902
(m), 2865 (m), 1585 (m), 1567 (m), 1512 (m), 1467 (m), 1389 (s),
1361 (s), 1269 (s), 1201 (m), 1149 (m), 1118 (m), 1103 (m), 1017
(s), 859 (m), 831 (s), 793 (s), 779 (s), 738 (m), 679 (m), 661 (s).
40-(2-5,8,11,14,17-Penta-tert-butylhexa-peri-hexabenzocoro-
nene)-2,20;60,200-terpyridine (1): 4 (40 mg, 3.82 ꢀ 10-5 mol) was
dissolved in degassed DCM (50 mL) in a three-necked round-
bottom flask, and nitrogen was bubbled through the solution.
FeCl3 (155 mg, 9.55 ꢀ 10-4 mol) was dissolved in nitromethane
(2 mL) in a small Schlenk flask, and the solution was degassed.
The solution was then transferred slowly into the stirring DCM
solution via cannula. The resulting solution was stirred over-
night with N2 bubbling through the solution. The reaction
mixture was then added to 50 mL of MeOH to obtain a red/
brown solution. The solvent was removed in vacuo, and the
solid obtained was purified by column chromatography on
silica, first using chloroform then a mixture of CHCl3/MeOH
(1:1) to remove a red band due to an iron complex ([Fe(HBC-
tpy)2](Cl)2). Finally, a mixture of CHCl3/NEt3 (4:1) was used to
remove a yellow compound slowly from the column. The
fractions containing the yellow compound were combined,
and the solvent was removed to give 34 mg (86%) of the product:
1H NMR (CDCl3, 600 MHz) δ 9.57 (s, 2 H), 9.40 (s, 2 H), 9.36
(m, 8 H), 9.19 (s, 2 H), 8.84 (d, 2 H), 8.81 (d, 2 H), 7.96 (dd, 2 H),
7.44 (dd, 2 H), 1.87 (s, 27 H, -C(CH3)3), 1.85 (s, 18 H,
-C(CH3)3); 13C NMR (CDCl3) δ 155.9 (quart.), 152.2
(quart.), 151.5 (quart.), 149.4 (quart.), 149.2 (quart.), 149.11 (2
C, -CH), 148.8 (quart.), 137.1 (2 C, -CH), 135.8 (quart.), 131.4
(quart.), 130.7 (quart.), 130.5 (quart.), 130.5 (quart.), 130.2
(quart.), 126.1 (quart.), 125.5 (quart.), 124.0 (quart.), 123.9 (2
C, -CH), 121.7 (2 C, -CH), 121.0 (2 C, -CH), 120.9 (quart.),
120.6 (quart.), 120.5 (2 C, -CH), 119.5 (2 C, -CH), 119.4 (2 C,
-CH), 119.0 (6 C, -CH), 35.8 (quart., -C(CH3)3), 35.8 (quart.,
-C(CH3)3), 32.1 (-CH, -C(CH3)3), 32.0 (-CH, -C(CH3)3);
MALDI-TOF MS m/z = 1033.5287, calcd for C77H67N3
1033.5335; IR ν (cm-1) 2952 (s), 2903 (m), 2865 (m), 1604 (m),
1581 (s), (1556 (m), 1463 (m), 1392 (m), 1365 (s), 1308 (w), 1259
(s), 1200 (m), 1077 (s, br), 1016 (s, br), 940 (m), 862 (s), 787 (s),
744 (s), 728 (s), 659 (s).
4-Iodo-40-tert-butylphenylacetylene (5): 4-tert-Butylphenyla-
cetylene (1.37 mL, 7.58 ꢀ 10-3 mol) was dissolved in THF (20 mL).
This solution was transferred via cannula to a solution of p-
diiodobenzene (6.26 g, 1.90 ꢀ 10-2 mol), PdCl2(PPh3)2 (27 mg,
3.8 ꢀ 10-4 mol), and CuI (7 mg, 3.68 ꢀ 10-5 mol) in diisopro-
plyamine (15 mL) and THF (60 mL) in a Schlenk flask. The
mixture was stirred overnight at room temperature under Ar.
H2O (40 mL) and DCM (100 mL) were added to the reaction
mixture, and the organic layer was separated. The aqueous layer
was washed with DCM (2 ꢀ 40 mL), and the combined organic
fractions were dried over MgSO4 and reduced in volume. The
product was isolated by column chromatography (silica,
hexane) resulting in 1.98 g (73%). Crystals of 5 suitable for
X-ray diffraction were obtained by slow evaporation of a hexane
solution: 1H NMR (CDCl3) δ 7.70 (d, 3J = 8.35 Hz, 2 H), 7.48
(d, 3J = 8.54 Hz, 2 H), 7.39 (d, 3J = 8.54 Hz, 2 H), 7.27 (d, 3J =
8.53 Hz, 2 H), 1.35 (s, -C(CH3)3, 9 H); 13C NMR (CDCl3) δ
151.4 (quart.), 137.0 (2 C, -CH), 132.6 (2 C, -CH), 130.9 (2 C,
-CH), 125.0 (2 C, -CH), 122.6 (quart.), 119.4 (quart.), 93.4
(quart.), 90.5 (quart.), 87.4 (quart.), 34.4 (1 C (quart.), -C-
(CH3)3, 30.7 (3 C, -(CH3)3); IR ν (cm-1) 2952 (m), 2861 (m),
2218 (w), 1504 (m), 1478 (m), 1388 (m), 1361 (m), 1102 (m), 1002
(s), 832 (s), 819 (s), 733 (m). Anal. Calc for C18H17I: C, 60.01; H,
4.88. Found: C, 60.16; H, 4.88.
1-(4-Iodophenyl)-2,3,4,5,6-penta-(4-tert-butylphenyl)benzene
(6): 5 (255 mg, 7.08 ꢀ 10-4 mol) and 2,3,4,5-tetra(4-tert-
butylphenyl)cyclopenta-2,4-dienone (431 mg, 7.08 ꢀ 10-4 mol)
were mixed together with benzophenone (4 g, 2.20 ꢀ 10-2 mol)
in a 25 mL round-bottom flask fitted with an air condenser. The
reagents were stirred together under Ar on a sand microburner
at 350 °C for 2 h. The reaction mixture was cooled to room
temperature and was purified by column chromatography on
silica using a mixture of hexane/DCM (4:1) to give 488 mg
(73%) of product: 1H NMR (CDCl3) δ 7.18 (d, 3J = 8.54 Hz, 2
H), 6.87 (d, 4 H), 6.82 (m, 6 H), 6.69 (d, 6 H), 6.66 (d, 3J = 8.53
Hz, 4 H), 6.60 (d, 3J = 8.53 Hz, 2 H), 1.16 (s, 18 H, -C(CH3)3),
1.12 (s, 27 H, -C(CH3)3); 13C NMR (CDCl3) δ 147.4 (quart.),
147.0 (quart.), 147.0 (quart.), 140.4 (quart.), 140.34 (quart.),
140.26 (quart.), 139.6 (quart.), 138.1 (quart.), 137.3 (quart.),
137.2 (quart.), 137.1 (quart.), 135.0 (2 C, -CH), 133.1 (2 C,
-CH), 130.6 (4 C, -CH), 130.5 (6 C, -CH), 122.9 (4 C, -CH),
122.6 (6 C, CH), 90.2 (quart.), 33.6 (5 C, quart., -C(CH3)3), 30.7
(15 C, C(CH3)3); MALDI-TOF MS m/z = 940.4470, calcd for
C62H69I 940.4444; IR ν (cm-1) 2961 (s), 2903 (m), 2865 (m), 1513
(m), 1475 (m), 1148 (m), 1117 (m), 1104 (m), 1017 (m), 1009 (m),
860 (m), 829 (s), 777 (m), 680 (s). Anal. Calcd for C62H69I: C,
79.13; H, 7.39. Found: C, 78.01; H, 7.31.
2-Iodo-5,8,11,14,17-penta-tert-butylhexa-peri-hexabenzocoro-
nene (7): 6 (250 mg, 2.66 ꢀ 10-4 mol) was dissolved in degassed
DCM (100 mL) in a three-necked round-bottom flask, and a
stream of N2 was bubbled through the solution. FeCl3 (862 mg,
5.13ꢀ10-3 mol) was quickly transferred into a Schlenk flask
and dissolved in freshly distilled nitromethane (5 mL). The
FeCl3 solution was degassed and added slowly to the reaction
flask via cannula. The reaction was stirred for 12 h with N2
bubbling through the solution. MeOH (150 mL) was added to
quench the reaction and produce a dark yellow precipitate. The
yellow precipitate was filtered over Celite, washed well with
MeOH, dried, and redissolved in the minimum volume of DCM.
The DCM solution was passed through a short plug of silica gel
to remove Fe impurities. The resulting solution was evaporated
1
to dryness to produce 7 as an orange solid (221 mg, 90%): H
NMR (CDCl3) δ 9.17 (s, 2 H), 9.09 (s, 2 H), 9.00 (s, 2 H), 8.85 (s,
2 H), 8.67 (s, 2 H), 8.55 (s, 2 H), 2.00 (s, 9 H, -C(CH3)3), 1.95 (s,
18 H, -C(CH3)3), 1.83 (s, 18 H, -C(CH3)3); 13C NMR (CDCl3)
δ 148.1 (quart.), 147.9 (quart.), 147.8 (quart.), 131.5 (quart.),
130.0 (quart.), 129.6 (quart.), 129.3 (quart.), 129.2 (2 C, -CH),
128.0 (quart.), 123.5 (quart.), 123.0 (quart.), 122.9 (quart.),
122.7 (quart.), 119.8 (quart.), 119.4 (quart.), 119.3 (quart.),
118.7 (2 C, -CH), 118.42 (4 C, -CH), 118.35 (2 C, -CH),
118.2 (2 C, -CH), 35.7 (1 C, quart., -C(CH3)3), 35.6 (2 C,
quart., -C(CH3)3), 35.5 (2 C, quart., -C(CH3)3), 32.14 (3 C,
C(CH3)3), 32.09 (6 C, -C(CH3)3), 32.0 (6 C, -C(CH3)3);
MALDI-TOF MS m/z = 928.3538, calcd for C62H57I 928.3505;
IR ν (cm-1) 2953 (s), 2903 (m), 2865 (m), 1608 (m), 1570 (m),
1477 (m), 1460 (m), 1368 (s), 1261 (s), 1224 (m), 1201 (m), 866 (s),
850 (s), 744 (s). Anal. Calcd for C62H57I: C, 80.16; H, 6.18.
Found: C, 79.04; H, 6.05.
2-Trimethylsilylethynyl-5,8,11,14,17-penta-tert-butylhexa-peri-
hexabenzocoronene (8): 7 (160 mg, 1.72 ꢀ 10-4 mol), [Pd(PPh3)2-
Cl2] (7.24 mg, 1.03 ꢀ 10-5 mol), and CuI (1.97 mg, 1.03 ꢀ 10-5
mol) were dissolved in THF (15 mL) and diisopropylamine
(6 mL), and the resulting solution was degassed. Trimethyl-
silylacetylene (0.049 mL, 3.44ꢀ10-4 mol) was added, and the
solution was stirred overnight under N2. The solvent was
removed, and the residue was purified via column chromatog-
raphy on silica using a mixture of petroleum ether/DCM (3:1) to
give 8 as a bright orange solid (134 mg, 94%): 1H NMR (CDCl3)
δ 9.10 (s, 2 H), 9.02 (s, 2 H), 8.95 (s, 2 H), 8.78 (s, 2 H), 8.60
(s, 2 H), 8.46 (s, 2 H), 2.03 (s, 9 H, -C(CH3)3), 1.98 (s, 18 H,
J. Org. Chem. Vol. 75, No. 6, 2010 1869

Murphy and Draper
JOCArticle
-C(CH3)3), 1.88 (s, 18 H, -C(CH3)3), 0.68 (s, 9 H, -(CH3)3
TMS); 13C NMR (CDCl3) δ 147.4 (quart.), 147.2 (quart.), 147.1
(quart.), 129.5 (quart.), 129.2 (quart.), 129.1 (quart.), 128.9
(quart.), 128.7 (quart.), 128.3 (quart.), 123.9 (2 C, -CH),
122.5 (quart.), 122.4 (quart.), 122.1 (quart.), 119.2 (quart.),
119.1 (quart.), 118.8 (quart.), 118.6 (2 C, -CH), 118.0 (2 C,
-CH), 117.9 (2 C, -CH), 117.7 (2 C, -CH), 117.6 (2 C, -CH),
107.0 (1 C, -CtC-), 94.1 (1 C, -CtC-), 35.4 (1 C, quart.,
-C(CH3)3), 35.3 (2 C, quart., -C(CH3)3), 35.2 (2 C, quart.,
-C(CH3)3), 31.9 (3 C, -C(CH3)3), 31.84 (6 C, -C(CH3)3), 31.82
(6 C, -C(CH3)3), 0.1 (3 C, TMS); IR ν (cm-1) 2953 (s), 2903 (m),
2866 (m), 2146 (m), 1607 (m), 1578 (m), 1478 (m), 1369 (m), 1362
(m), 1247 (m), 1090 (m, br), 1020 (m, br), 987 (m), 942 (m), 865
(s), 854 (s), 840 (s), 668 (s); MALDI-TOF MS m/z = 898.4916,
calcd for C67H66Si 898.4943. Anal. Calcd for C67H66Si: C, 89.48;
H, 7.40. Found: C, 88.30; H, 7.33.
2-Ethynyl-5,8,11,14,17-penta-tert-butylhexa-peri-hexabenzo-
coronene (9): 8 (25 mg, 2.78 ꢀ 10-5 mol) was dissolved in THF
(5 mL) and MeOH (5 mL). KF (5 mg, 8.61 ꢀ 10-5 mol) was
added, and the mixture was stirred at room temperature for 20 h.
DCM (10 mL) and H2O (10 mL) were added to the reaction
mixture, and the yellow organic phase was separated. The
organic layer was dried over MgSO4, and the solvent was
removed in vacuo to give 9 (23 mg, 100%): 1H NMR (CDCl3)
δ 9.18 (s, 2 H), 9.11 (s, 2 H), 9.03 (s, 2 H), 8.88 (s, 2 H), 8.69
(s, 2 H), 8.60 (s, 2 H), 3.63 (s, 1 H, -CtCH), 1.98 (s, 9 H,
-C(CH3)3), 1.93 (s, 18 H, -C(CH3)3), 1.83 (s, 18 H, -C(CH3)3);
13C NMR (CDCl3) δ 148.3 (quart.), 148.1 (quart.), 148.0
(quart.), 130.2 (quart.), 129.84 (quart.), 129.80 (quart.), 129.7
(quart.), 129.5 (quart.), 128.7 (quart.), 124.4 (2 C, CH), 123.2
(quart.), 123.1 (quart.), 122.9 (quart.), 120.1 (quart.), 119.9
(quart.), 119.6 (quart.), 119.04 (2 C, -CH), 118.97 (quart.),
118.6 (2 C, -CH), 118.5 (2 C, -CH), 118.4 (4 C, -CH), 85.9 (1 C,
-CtCH), 77.2 (1 C, -CtCH), 35.8 (1 C, quart., -C(CH3)3),
35.7 (2 C, quart., -C(CH3)3), 35.6 (2 C, quart, -C(CH3)3),
32.2 (3 C, -C(CH3)3), 32.2 (6 C, -C(CH3)3), 32.1 (6 C,
-C(CH3)3); MALDI-TOF MS m/z = 826.4547, calcd for
C64H58 826.4539; IR ν (cm-1) 3310 (w), 2953 (s), 2905 (m),
2866 (m), 2163 (w), 1607 (m), 1578 (m), 1478 (m), 1459 (m), 1362
(s), 1244 (m), 1201 (m), 1503 (m, br), 1021 (m, br), 942 (m), 865
(s), 811 (s).
40-(2-Ethynyl-5,8,11,14,17-penta-tert-butylhexa-peri-hexabe-
nzocoronene)-2,20;60,200-terpyridine (2): Route A: 7 (50 mg,
5.38 ꢀ 10-5 mol) and 40-ethynyl-2,20;60,200-terpyridine (13.9 mg,
5.38 ꢀ 10-5 mol) were dissolved in benzene (12 mL) and
diisopropylamine (3 mL), and the resulting solution was de-
gassed via three freeze-pump-thaw cycles. Pd(PPh3)4 (3.1 mg,
2.69 ꢀ 10-6 mol) was then added, and the clear yellow solution
was heated to 70 °C under Ar overnight. The resulting bright
yellow precipitate was cooled, and the volume of the solvent was
reduced in vacuo. The insoluble yellow precipitate was removed
via filtration, washed with ether, and dried (48 mg 85%). Route
B: 9 (50 mg, 6.04 ꢀ 10-5 mol) and 40-[{(trifluoromethyl)-
sulfonyl}oxy]-2,20;60,200-terpyridine (23 mg, 6.04 ꢀ 10-5 mol)
were dissolved in toluene (15 mL) and diisopropylamine (5 mL),
and the resulting solution was degassed via three freeze-
pump-thaw cycles. Pd(PPh3)4 (3.5 mg, 3.23 ꢀ 10-6 mol) was
then added, and the clear yellow solution was heated to
70 °C under Ar for 48 h. The reaction mixture was cooled,
and the volume of solvent was reduced in vacuo. The insoluble
yellow precipitate was removed via filtration, washed with ether,
and dried (49.6 mg, 78%): 1H NMR (CDCl3, poorly soluble) δ
9.43 (s, 2 H), 9.35 (m, 8 H), 9.33 (s, 2 H), 8.85 (s, 2 H), 8.82 (d,
2 H), 8.66 (d, 2 H), 7.91 (dd, 2 H), 7.42 (dd, 2 H), 1.91 (s, 18 H,
-C(CH3)3), 1.87 (s, 27 H, -C(CH3)3); MALDI-TOF MS m/z =
1057.5345, calcd for C79H67N3 1057.5335; IR ν (cm-1) 2952 (s),
2903 (m), 2866 (m), 2218 (w), 1604 (m), 1581 (s), 1565 (m), 1465
(m), 1446 (m), 1391 (s), 1360 (s), 1307 (w), 1258 (s), 1200 (m),
1148 (m), 1097 (m), 999 (m), 940 (m), 882 (m), 866 (s), 810 (m),
787 (s), 764 (m), 741 (s), 672 (s), 660 (s).
Acknowledgment. The authors thank Dr. John O’Brien,
Dr. Manuel Reuther, and Dr. Martin Feeney for technical
assistance, and Dr. Thomas McCabeand Dr. Sunil Varughese
for the X-ray crystallography. The work presented was
supported financially by Science Foundation Ireland
(05PICAI819) and IRCSET (PG-Murphy).
Supporting Information Available: 1H and 13C NMR spec-
tra for compounds 1-9, X-ray crystallographic information for
compounds 5 and 7. This material is available free of charge via
the Internet at http://pubs.acs.org.
1870 J. Org. Chem. Vol. 75, No. 6, 2010