Molecular spoked wheels: Synthesis and self-assembly studies on rigid nanoscale 2D objects

Article abstract of DOI:10.1002/chem.201203444

We present the efficient synthesis of a new molecular spoked-wheel structure (MSW-3). Two derivatives with diameters of approximately 4 nm have been prepared. By highlighting the importance of pseudo-high-dilution conditions during cyclization, we were able to access the compounds on a several hundred milligram scale. In addition to the standard characterization (NMR spectroscopy, MS), we describe a detailed investigation of the optical properties of the fluorescent MSWs by comparison with appropriate model chromophores. Furthermore, a comprehensive study of the structure in solution by means of light- and X-ray scattering experiments has been conducted. Scanning tunneling microscopy (STM) revealed the two-dimensional organization of the molecules on highly oriented pyrolytic graphite and emphasized the spoked-wheel structure. The diameter of these molecules measured by small-angle X-ray scattering is in very good agreement with that obtained from STM and matches the results of molecular modeling. This confirms the rigidifying effect of the spokes, which results in highly shape-persistent nanometer-sized oblate organic compounds. Copyright

Full text of DOI:10.1002/chem.201203444

DOI: 10.1002/chem.201203444
Molecular Spoked Wheels: Synthesis and Self-Assembly Studies
on Rigid Nanoscale 2D Objects
A. Vikas Aggarwal,[a] Stefan-S. Jester,[a] Sara Mehdizadeh Taheri,[b]
Stephan Fçrster,*[b] and Sigurd Hçger*[a]
Abstract: We present the efficient syn-
thesis of new molecular spoked-
MSWs by comparison with appropriate
model chromophores. Furthermore, a
comprehensive study of the structure
in solution by means of light- and X-
ray scattering experiments has been
conducted. Scanning tunneling micro-
scopy (STM) revealed the two-dimen-
sional organization of the molecules on
highly oriented pyrolytic graphite and
a
emphasized the spoked-wheel struc-
ture. The diameter of these molecules
measured by small-angle X-ray scatter-
ing is in very good agreement with that
obtained from STM and matches the
results of molecular modeling. This
confirms the rigidifying effect of the
spokes, which results in highly shape-
persistent nanometer-sized oblate or-
ganic compounds.
wheel structure (MSW-3). Two deriva-
tives with diameters of approximately
4 nm have been prepared. By highlight-
ing the importance of pseudo-high-di-
lution conditions during cyclization, we
were able to access the compounds on
a several hundred milligram scale. In
addition to the standard characteriza-
tion (NMR spectroscopy, MS), we de-
scribe a detailed investigation of the
optical properties of the fluorescent
Keywords: aggregation · aromatic
compounds · macrocycles · nano-
structures · template synthesis
Introduction
tivity, the discovery of new carbon allotropes and the re-
markable effort in the development of transition-metal-cata-
À
Large oblate molecules that consist of arylene and alkyny-
lene moieties have been in the focus of research since the
1960s and the 1970s, mainly with respect to the question
about the aromaticity in cyclic conjugated p-systems
(Figure 1).[1] After a period with only moderate scientific ac-
lyzed C C cross-coupling reactions reinitiated the interest
in such carbon-rich compounds in the 1990s.[1a–d,h,2]
Although early publications on this topic focused on the
basic concepts of macrocycle synthesis,[1a,d,e,2j,3] the attention
soon shifted towards the investigation of the properties of
the developed compounds.[2c,4] Nowadays, shape-persistent
macrocycles (e.g., phenylene–acetylene macrocycles (PAMs)
or dehydrobenzo[n]annulenes (DBAs)) are designed in ad-
vance to (ideally) possess desired and predictable molecular
(microscopic), supramolecular (mesoscopic), and materials
(macroscopic) properties and functionalities in light of their
intended applications. In particular, the possibility to fine-
tune the properties of the molecules by side-group modifica-
tion has led to advanced systems. Recent efforts in the
emerging field of molecular engineering have derived com-
pounds that can act as optically active materials,[5] as molec-
ular wires,[6] as containers for reactions in confined environ-
ments,[7] or as versatile tiles for surface patterning.[8] Never-
theless, although continuative fundamental research in the
field of synthesis opens up new pathways to previously inac-
cessible compounds on larger scales, the investigations of in-
herent molecular and material properties still often lead to
unexpected findings.[2a,5h,8i,9]
Figure 1. Chemical structures of dehydrobenzo[n]annulenes (DBAs) and
phenylene–acetylene macrocycles (PAMs).
[a] A. V. Aggarwal, Dr. S.-S. Jester, Prof. Dr. S. Hçger
Kekulꢀ-Institut fꢁr Organische Chemie und Biochemie
Rheinische Friedrich-Wilhelms-Universitꢂt Bonn
Gerhard-Domagk-Strasse 1, 53121 Bonn (Germany)
Fax : (+49)228-73-5662
E-mail: Hoeger@uni-bonn.de
Recently, we reported about reinforced shape-persistent
macrocycles, naming them molecular spoked wheels
(MSWs), as their structures resemble a wheel-like motif
(Figure 2).[10] We referred to their building blocks as hub,
spokes, and rim, and this terminology shall be applied here
as well. Apart from MSWs, only few macrocycles with rigid
[b] S. M. Taheri, Prof. Dr. S. Fçrster
Physikalische Chemie I, Universitꢂt Bayreuth
Universitꢂtsstrasse 30, 95440 Bayreuth (Germany)
E-mail: Stephan.Foerster@uni-bayreuth.de
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201203444.
4480
ꢃ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2013, 19, 4480 – 4495

FULL PAPER
Figure 2. Previously synthesized MSW-1 and MSW-2a/b.[10]
intraannular covalently attached moieties have been pub-
lished to date.[11] The structure of the MSWs directly sug-
gests that their synthesis can be performed by the covalent
template approach.[2j,k,5b,12] Generally, covalent as well as
noncovalent templates are often used in directed synthesis
so as to favor the formation of a certain product or to in-
crease yields.[2j,13] However, apart from solely acting as cova-
lent connectors between the rim segments and the hub, thus
facilitating a cyclization (instead of the otherwise expected
formation of acyclic and cyclic oligomers of different oligo-
merization degrees), the spokes fulfill a second task: they
also stiffen the final MSW structure by increasing the elastic
modulus of the backbone. Although PAMs are often refer-
red to as shape-persistent, molecular dynamics (MD) simu-
lations indicate a high degree of flexibility of these struc-
tures in solution.[10b,12c] Even in crystal structures, distortions
of the macrocyclic backbones are frequently observed[4,5i,14]
and ascribed to the finite persistence length of poly(p-phe-
nyleneacetylene)s (PPAs).[10b,15] This limited rigidity also be-
comes important when two-dimensional organization of the
compounds is investigated.[8h] PAMs can be viewed as regu-
lar molecular polygons that consist of a tuple of corner units
(i.e., implemented by o- or m-phenylene units or (hetero-)
aromatic building blocks) that are linked by intermediate
rigid rod units (i.e., realized by p-phenylene/acetylene
units).[8h,16] When the polygons exceed a specific size or
number of corner units (i.e., the circumference of the mac-
rocycle exceeds a certain length), multiple conformations
are possible, including collapsed ones. Consequently, such
shape-persistent macrocycles can no longer be viewed as
(truly) rigid. MSWs, on the other hand, can either be consid-
ered as, more descriptively, macrocycles that are reinforced
by rigid spokes, or, probably more correctly, as six small
fused triangular shape-persistent macrocycles. According to
the first model, the spoke units of the MSWs restrict the
conformational degrees of freedom of shape-persistent mac-
rocycles, so that (apart from elasticity) their noncollapsed
symmetrical shape is maintained even if the compounds are
rather large. According to the second model, shape persis-
tency is achieved by the fusion of (smaller) triangular mac-
rocycles that reduce their degrees of freedom as distortions
of any segment induce an additional strain on the other tri-
angular parts of the MSW. For the first MSW (MSW-1),
which had a diameter of 5–6 nm (depending on the atoms
depicted for the distance measurement), extensive molecu-
lar dynamics (MD) and small-angle neutron scattering
(SANS) experiments were conducted.[10b,12c] The MD trajec-
tory, which shows the temporal evolution of the distance be-
tween two opposing atoms and their angle with the hub, re-
vealed that the MSW is much more rigid than its uncyclized
precursor or a corresponding PAM without rigidifying
spokes.[10b]
Additional proof of the wheel-like structure of MSWs
came from scanning tunneling microscopy (STM) investiga-
tions performed in situ at the liquid–solid interface. For
both macrocycles MSW-1 and MSW-2, submolecular fea-
tures, the backbone, the hub, the six spokes, and the six rim
segments were observable.[10a,b] Information on the self-as-
sembly behavior of MSWs was obtained by atomic force mi-
croscopy (AFM), which revealed a strong dependency of
the 3D packing of the MSWs on the length of their solubiliz-
ing side groups.[10a,b] In this context it is worth mentioning
that MSW-2a, with 48 hexyl side chains, exhibits a strong
tendency to form fiberlike structures when drop-casted from
Chem. Eur. J. 2013, 19, 4480 – 4495
ꢃ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
4481

S. Fçrster, S. Hçger et al.
toluene onto graphite. The resulting fibers extend over sev-
eral hundred nanometers and consist of stacks of MSWs ori-
ented perpendicularly to the surface.[10a] These results indi-
cate that MSWs can aggregate even when they contain a
rather large number of solubilizing side groups.
Herein, we present the synthesis of a new MSW (MSW-3)
and highlight its molecular properties and its self-assembly
in solution and on the surface. MSW-3 is smaller, and there-
fore expected to be even more rigid than the previously re-
ported MSWs (considering the molecular elasticity due to
shorter rigid segments). Due to a straightforward synthetic
protocol, MSW-3a was obtained on a scale of several hun-
dreds of milligrams. This was a prerequisite for an investiga-
tion of further materials properties either in the pure state
or as composite materials.[5k,17] MSW-3b, however, was con-
structed to allow subsequent functionalization after selective
dealkylation of the tBu periphery under mild acidic condi-
tions.
Figure 4. Schematic representation of the convex modular synthetic ap-
proach towards MSW-3a/b.
wards the rim module 7a were studied. The first route
began with the bromination of anisidine (1) followed by a
twofold Suzuki coupling[18] of 2 with the boronic ester triiso-
propyl{[4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phe-
nyl]ethynyl}silane (see Figure S3 in the Supporting Informa-
tion).[10b] Compound 3 was obtained after column chroma-
tography and its amino group was converted to the iodide
by the addition of iodine and tert-butyl nitrite to a solution
of 3 in benzene at 08C.[19] However, yields over all three
steps were low to moderate, and 7a was obtained in an over-
all yield of 11%. An alternative route to 7a was based on
Hartꢄs terphenyl synthesis. In principle, this reaction allows
the preparation of 2’-functionalized m-terphenyls in a single
step from 1,3-dibromides or 1,3-dichlorides.[20] However, 1,3-
dichloro-5-methoxybenzene (5a) required prefunctionaliza-
tion to direct metalation to the 2-position. Otherwise a bi-
phenyl was formed instead of the m-terphenyl 7a.[21] There-
fore, 5a was iodinated with phenyliodine bis(trifluoroace-
tate) (PIFA). This yielded 3,5-dichloro-4-iodoanisole togeth-
er with 3,5-dichloro-2-iodoanisole in a 3:1 ratio.[22] Despite
the fact that both compounds were inseparable at the cur-
rent stage, this product mixture was subjected to the Hart
reaction. We found that slow, dropwise addition of a solu-
tion of 6a in diethyl ether to a solution of 4-[2-(triisopropyl-
silyl)ethynyl]phenyllithium (prepared by the reaction of 1-
bromo-4-(triisopropylsilylethynyl)benzene[23] with tBuLi)
was crucial to obtain the coupled product in high yields
after an iodine quench.[24,25] Both products, the terphenyl
(7a) as well as the undesired biphenyl side product, were
isolated in yields that corresponded to approximately 75%
conversion of the respective iodides. Thus, clearly, the initial
lithium–iodine exchange proceeds very rapidly under these
conditions[25,26] and overrides any o-directing tendencies of
the methoxy group. Separation of both products was
straightforward by column chromatography, and 7a was iso-
lated as a pure compound. In summary, the route towards
7a based on the Suzuki coupling allows the purification of
all intermediate compounds, however, the overall yield over
three steps is low (Scheme 1a–c; 11%). On the other hand,
the route by means of the Hart reaction is considerably
shorter than the first route[27] and allows the isolation of
much larger quantities of 7a (Scheme 1e,f; 48%). Thus, 7b
was prepared only by the second route.
Results and Discussion
Synthesis: Figure 3 shows the chemical structure of MSW-3a
and MSW-3b. Both molecules are based on the same back-
bone but differ in their side-chain lengths. Their synthesis
Figure 3. Chemical structure of the new MSWs.
relies on a convex modular approach:[10] the three distinct
building blocks (the rim, spoke, and hub modules) are pre-
pared independently from each other and are combined just
prior to the cyclization (Figure 4). This minimizes the
number of sixfold transformations during the synthesis.
Compound 5b was not commercially available but readily
prepared by the reaction of 3,5-dichlorophenol (4) with iso-
butene.[28] Attempts to iodinate 5b regioselectively with
PIFA in the 2-position were still unsatisfactory, although a
better regioisomer ratio of 6:1 was obtained as calculated
Synthesis of the modules: The efficient preparation of the
spoke/rim segment 10a/b was a central task to the MSW
synthesis (Scheme 1, top). Therefore two different routes to-
4482
www.chemeurj.org
ꢃ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2013, 19, 4480 – 4495

Molecular Spoked Wheels
FULL PAPER
1
from the H NMR spectrum of
the crude reaction product. On
the contrary, a clean synthesis
of the desired 5-tert-butoxy-1,3-
dichloro-2-iodobenzene
(6b)
was achieved by deprotonation
of 5b with nBuLi at À788C fol-
lowed by the addition of iodine.
In contrast to the methoxy
group on 5a, the tBu group on
5b is bulky enough to suppress
any o-directing effects of the
oxygen atom.[29] Hence, the
most acidic hydrogen atom, lo-
cated between both chlorine
atoms, was substituted.[30] Com-
pound 6b, prepared by the
latter route, was then converted
to 7b in a similar manner as de-
scribed for the synthesis of 7a.
All in all, the yields of both 7a
and 7b show that the Hart reac-
tion opens up an efficient way
towards functionalized m-ter-
phenyls that can be incorporat-
ed into the spoked-wheel struc-
Scheme 1. Synthesis of MSW-3a and
MSW-3b. a) Br2, CH2Cl2, MeOH,
08C–RT, 4 h, 64%; b) triisopropyl{[4-
(4,4,5,5-tetramethyl-1,3,2-dioxaboro-
lan-2-yl)phenyl]ethynyl}silane,
pyri-
dine-enhanced precatalyst preparation
stabilization and initiation (PEPPSI),
KOH, THF, 608C, 24 h, 47%;[33]
c) tBuONO, I2, benzene, 08C–RT, 17 h,
36%;
d) R1 =tBu:
1) isobutene,
F3CSO3H, CH2Cl2, À788C, 3 h;
2) NEt3, À788C–RT, 17 h, 86%;
e) R1 =Me: PIFA, I2, CH2Cl2, RT,
2.5 h, 85% (3:1 mixture); R1 =tBu:
1) nBuLi, THF, À788C, 90 min; 2) I2,
THF, À50–108C, 20 min, 90%; f) 1) 1-
bromo-4-(triisopropylsilylethynyl)ben-
zene, tBuLi, Et2O, À78–108C, 1 h;
2) 10, 108C–RT, 17 h; 3) I2, Et2O, 0 8C,
60 min; 7a: 73%/48% (over two
steps: e+f); 7b: 66%; g) [PdCl2-
AHCTNUGRTEG(NNNU PPh3)2], CuI, PPh3, THF, piperidine;
9a: 908C, 3.5 h, 75%; 9b: mw (micro-
wave irradiation), 1208C, 12 min,
81%; h) K2CO3, THF, methanol, RT,
2 h; 10a: 91%; 10b: 94%; i) [PdCl2-
AHCTNUGRTEG(NNNU PPh3)2], CuI, PPh3, THF, piperidine,
808C, 17 h; 11a: 76%; 11b: 77%;
j) TBAF, THF, 08C–RT, 3 h; 12a:
98%; 12b: 74%; k) addition of 12a/b
to a stirred solution of [PdCl2ACHTUNGTRENNUNG(PPh3)2],
CuI, I2, NHiPr2, THF, 508C; MSW-3a:
90 h, 79%; MSW-3b: O2, 48 h, 68%.
HIPB=hexa(4-iodophenyl)benzene.
Chem. Eur. J. 2013, 19, 4480 – 4495
ꢃ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
4483

S. Fçrster, S. Hçger et al.
tures as shown below. The spoke (8a/b) and hub (hexa(4-io-
dophenyl)benzene (HIPB)) modules were readily obtained
by adopting procedures known from the literature (details
are reported in the Supporting Information).[31]
fluoride (TBAF) in THF within 3 h at RT (12a/b; Scheme 1,
middle).[39]
Cyclization reaction: Cyclization reactions (Scheme 1,
bottom) of 12a and 12b to MSW-3a and MSW-3b, respec-
tively, were performed by very slow addition of diluted solu-
tions of 12a/b in THF to vigorously stirred solutions of the
Assembly of the modules: The spoke module 8a and the
corner piece 7a were linked by a Sonogashira–Hagihara re-
action (Scheme 1, middle). With [Pd
N
catalyst systems ([PdACTHNGUTERNNUG
(PPh3)2Cl2], CuI, co-oxidizing agent)[9a]
iodide, and triphenylphosphane as catalyst system,[32] it was
essential to conduct this reaction at an elevated temperature
of at least 808C although the coupling of the acetylene was
performed with an aryl iodide. Lower reaction temperatures
only led to the formation of the diacetylene coupling prod-
uct, most probably owing to the steric hindrance at the iodo
position of 7. Nevertheless, 9a could be obtained in 80%
yield. In contrast, the yields of 9b were considerably lower
when using the same reaction conditions (Table 1).
in THF and di(isopropyl)amine at 508C. For the cyclization
of 12a, I2 was employed as the co-oxidizing agent, and the
dependency of the product yield on the time of addition and
concentration was investigated. In a second optimization
step, alternative (co-)oxidizing agents were tested on the
cyclization of 12b.
The template effect of the hub/spoke system on 12a/b
strongly favors intramolecular cyclization. Nevertheless, the
molecular-weight distribution of the crude product of MSW-
3a heavily depends on the addition time and on the
concentration, as determined by gel permeation
Table 1. Variations of the conditions of the Sonogashira–Hagihara reaction towards
9b.
chromatography (GPC) analysis (Figure 5a). If 12a
(0.83 mmol, 5 mg, 2 mL solution) is added instantly
to a concentrated solution of the catalyst (1.4 equiv
Entry
Catalyst system
Solvent
Base
Heat[a]
t
Yield
[%]
[PdCl2ACHTUNGRTNEUNG(PPh3)2], 2.0 equiv CuI, 7.8 equiv I2, 2.5 mL
1
2
3
4
5
[Pd
PPh3, CuI
[Pd(PPh3)2Cl2]
PPh3, CuI
[PdCl2A(dppe)]
CuI[d]
G
THF
THF
–
piperidine
piperidine
piperidine
conv
908C
mw
1208C
mw
1208C
mw
1208C
mw
17 h
31
solution; thus resulting in a concentration of 12a of
184 mmolLÀ1), a large amount of dimer and even
higher oligomers are produced. Increasing the time
of addition to 117 h and reducing the concentration
of 12a in the receiver to 0.2 mmolLÀ1[40] gives the
desired molecular spoked wheel almost exclusively.
These findings underline the importance of
(pseudo) high-dilution conditions[3] for the success
of multiple intramolecular coupling reactions, even
for templated PAMs.
12 min
10 min
12 min
12 min
77
G
–
[Pd
G
THF
MeCN
piperidine
DBU[b]
30[35]
12
PtBu3, CuI[34]
[(AllylPdCl2)2]
piperidine
[36]
PtBu3
DABCO[c]
1208C
[a] mw=Microwave irradiation, conv=conventional heating. [b] DBU=1,8-diazabicy-
cloundec-7-ene. [c] DABCO=1,4-diazabicyclo[2.2.2]octane. [d] dppe=1,2-bis(diphe-
nylphosphino)ethane.
AHCTUNGTRENNUNG
To enable the preparation of large quantities of
MSW-3a/b, the reduction of the amount of side
However, microwave (mw) heating of a sealed system re-
sulted in a dramatic increase of the product yield, and the
reaction time was reduced to a few minutes. By using the
standard catalyst system and heating to 1208C in a sealed
vessel, 9b was obtained in yields comparable to those of 9a
(Table 1, entry 2). At present, we ascribe this observation to
the much higher reaction temperature (1208C) that is ob-
tainable in the sealed microwave flask.[37] A further varia-
tion of the reaction conditions (ligand, base) only gave infe-
rior product yields (Table 1).
products and of the reaction time were desired. As the
copper-catalyzed protocol that had been optimized for the
MSWs published earlier[10a] gave no conversion of the start-
ing material (Figure 5b, light blue trace), modifications were
made to the palladium-based catalyst system. Since a rate
increase of the coupling reaction would have the same effect
as a slower reactant addition, alternative co-oxidizing agents
were considered for the cyclization reaction of 12b (Fig-
ure 5b). In fact, bubbling air through the solution prior to
the reaction or employing benzoquinone or 2,3-dichloro-5,6-
dicyano-1,4-benzoquinone (DDQ) instead of iodine under
an inert atmosphere proved beneficial for the intramolecular
reaction. The amount of dimer formed was reduced to a
third.[41]
The 3-(cyanopropyl)dimethylsilyl (CPDMS) protecting
groups on 9a and 9b were removed selectively.[38] Similarly
to the trimethylsilyl (TMS) group, CPDMS is readily
cleaved by potassium carbonate in THF/MeOH, thus leav-
ing the more stable triisopropylsilyl groups (TIPS) unaffect-
ed (10a/b). Subsequently, 10a and 10b were coupled to the
hub module (HIPB) in a sixfold Sonogashira–Hagihara reac-
The total yield over the final five steps in which the mod-
ules 7a, 8a, and HIPB were assembled reached up to 40%
for this macrocycle. Thus, on account of the efficient syn-
thetic route, we were able to obtain nearly 400 mg of MSW-
3a.
tion.[10a] By employing [Pd
ACTHUNRGTNEG(UN PPh3)2Cl2], copper iodide, and
triphenylphosphane at 808C, excellent yields of 76 and 77%
were obtained, which corresponded to 96% conversion per
reactive site. Then all twelve TIPS groups of 11a/b were re-
moved in good to excellent yields with tetrabutylammonium
Proof of cyclization: The successful sixfold ring closure was
proven by a variety of analytical methods. GPC shows an in-
4484
www.chemeurj.org
ꢃ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2013, 19, 4480 – 4495

Molecular Spoked Wheels
FULL PAPER
is more rigid than polystyrene, and its hydrodynamic radius
expands faster than that of a coiled polymer (such as PS)
but not nearly as fast as for linear rigid rod molecules.[42]
The combination of both effects leads to a rather good
agreement between GPC-measured (PS calibration) and
exact molecular weight (Table 2).
Table 2. Comparison of GPC-determined (PS calibration; peak molecu-
lar weight) and exact molecular weights.
Compound
Mabs [gmolÀ1
]
MGPC [gmolÀ1
]
MGPC/Mabs
12a
MSW-3a
12b
6002.76
5990.66
5581.96
5569.86
5830
5510
5620
5290
0.97
0.92
1.01
0.95
MSW-3b
Matrix-assisted laser desorption/ionization mass spectrom-
etry (MALDI-MS) clearly shows a difference of 12 Da that
corresponds to the twelve terminal acetylene hydrogen
atoms (Table 2). Furthermore, their absence at d=3.1 ppm
is observed by 1H NMR spectroscopy. Even the signals in
the aromatic region are well resolved and can be assigned
unambiguously (Figure 6).
Figure 5. a) Dependency of the relative amounts of MSW-3a, related
dimer, and higher oligomers on the concentration of 12a in the reaction
flask and the time of addition (catalyst: [PdCl2ACTHNUTRGNEG(UN PPh3)2], CuI, I2, diisopro-
pylamine, THF). Apart from the instant addition, the concentrations
were calculated for an assumed drop size of 0.05 mL.[40] b) Left: Amounts
of MSW-3b and the corresponding dimer relative to the type of oxidizing
agent used. These reactions were performed by instant addition of a solu-
tion of 12b to the heated catalyst solution, thereby resulting in an initial
concentration of 28 mmolLÀ1. Right: Magnification of the dimeric by-
product peak (UV absorption at 254 nm) in relation to the peak of MSW-
3b. DDQ=2,3-dichloro-5,6-dicyano-1,4-benzoquinone; BZQ=benzoqui-
none; DBU=1,8-diazabicycloundec-7-ene.
Figure 6. a) Partial molecular structure of 12b and MSW-3b, including an
assignment of the 1H NMR spectroscopic signals to hydrogen atoms of
the aromatic building blocks. b) 1H NMR spectra of 12b and MSW-3b.
The absence of the acetylene signal at d=3.1 ppm (see arrow) in MSW-
3b is a clear indicator of an effective cyclization.
crease in retention time upon cyclization of 12a/b to MSW-
3a/b that corresponds to a reduction of the estimated molec-
ular mass of approximately 325 Da instead of 12 Da expect-
ed for the loss of twelve hydrogen atoms. However, GPC is
a relative method for the detection of molecular weights
with a calibration based on the assignment of a measured
retention time to a specific molecular weight, in our case a
narrow dispersed polystyrene (PS) standard. The overesti-
mated molar mass difference between 12a/b and MSW-3a/b
is ascribed to the reduced hydrodynamic radius of the MSW
relative to the open precursor. In MSW-3a/b the rim–
spoke–“arms” are fixed in a plane and are therefore not
nearly as space filling as in 12a/b in which they can rotate
around the spoke axis and also bend out of the plane. In ad-
dition, the underestimation of the molecular weight by GPC
increases with the length of the alkyl chains. This is consis-
tent with expectations for branched molecular objects with a
high graft density. Conversely, the spoked-wheel backbone
Optical properties: The UV/Vis absorption and emission
spectra of corresponding compounds (MSW-3a/b and 12a/b)
are very similar, although the absorption spectrum of 12b
shows a better resolved fine structure than the spectrum of
12a (see the Supporting Information for the spectra of 12a,
MSW-3a, 12b, and MSW-3b; the former are also included
in Figure 8 below).
To model the UV/Vis absorption spectrum of 12a, differ-
ent chromophores were combined to model sets. Scheme 2
outlines the synthesis of the chromophores that is based on
repetitive Sonogashira–Hagihara coupling and acetylene de-
protecting reactions. Compound 15 resembles the rim chro-
mophore of 12a omitting the methoxy and phenyl groups in
m positions, as p-conjugation is expected to be hindere-
d.[10a,43] Compounds 20 and 22 represent the spoke chromo-
phore. Whereas 20 considers the expected interruption of
Chem. Eur. J. 2013, 19, 4480 – 4495
ꢃ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
4485

S. Fçrster, S. Hçger et al.
as the absorption derived from
the extended spoke chromo-
phore (lmax =384 nm) decrease.
Instead, two new absorption
maxima are observed at l=323
and 345 nm.
These changes are attributed
to two processes. Firstly, the
length doubling of the rim chro-
mophore after the acetylene
homocoupling leads to a strong
redshift of the previously unre-
solved features with l<300 nm
(the absorption spectrum of
1,4-bis[4-(1,1’-biphenyl)]buta-
diyne (lmax =332 nm) can be
found in the Supporting Infor-
mation). Secondly, the cycliza-
tion constrains the rotational
degrees of freedom of the
phenyl units on the spoke and
hub modules. As a result, the
intensity of the band at l=
384 nm is reduced, and a hypso-
chromic shift of the spoke chro-
mophore is observed.[44] Nevertheless, the long chromophore
can still be observed as a shoulder in the absorption spec-
Scheme 2. Synthesis of the model chromophores. a) TMSA, [PdCl
1208C, 12 min (mw), 85%; b) K2CO3, THF, methanol, RT, 2 h, 92%; c) 8a, [Pd
dine, 408C, 17 h, 82%; d) K2CO3, THF, methanol, RT, 2 h, 71%; e) 18, [Pd2ACTHUNGTRENNU(G dba)3], CuI, dppf, THF, piperidine,
1208C, 12 min (mw), 77%; f) [PdCl2ACHTUNGRTNE(UNG PPh3)2], CuI, PPh3, THF, piperidine, 1208C, 12 min (mw), 72%. CPDMS=
(3-cyanopropyl)dimethylsilyl.
2ACHTGNURTEN(NUNG PPh3)2], CuI, PPh3, THF, piperidine,
2ACHTUGNTREN(NUNG dba)3], CuI, dppf, THF, piperi-
conjugation along the spoke by a turbine-like arrangement
around the central hub, compound 22 spans the whole width
of the macrocycle. By an appropriate combination of these
chromophores, various model sets were prepared for 12a.
Two of them will be discussed here. In agreement with the
model for MSW-2, model system 1 contains six of the short
chromophores (20). Instead, model system 2 includes three
spoke chromophores (22). To model the rim units, both con-
tain twelve 4-ethynyl-1,1’-biphenyl (15) units. Figure 7 shows
comparisons between the absorption spectra of precursor
12a and both model systems.
Clearly, the absorption cannot be explained by purely
adding up the extinction coefficients of the chromophores.
The absorption of precursor 12a at 384 nm is only about
60% of that of the model systems. To simplify the compari-
son of the relative shifts, Figure 7b shows the precursor as
well as the model systems normalized to the second absorp-
tion maximum (l=384 nm for 12a and model 2, and l=
374 nm for model 1). The left-hand side of the absorption
spectrum is determined by the absorption of the rim
module, though the use of only one chromophore type is
not sufficient. The right-hand side of the spectrum is defined
by the absorption of the spoke chromophore. Clearly—and
contrary to earlier results[10a]—the spoke chromophore is not
divided in two halves by the hexaphenylbenzene hub. Here,
a coupling of the p-conjugation of the chromophores across
the hub is necessary to explain the absorption spectrum of
12a.
Figure 7. a) Comparison of the UV/Vis absorption spectra of 12a
(CH2Cl2, 6.7ꢅ10À6 molLÀ1) with its two model systems composed of 12ꢅ
Upon cyclization, distinctive changes in the UV/Vis ab-
sorption spectra can be observed (Figure 8). The intensity of
the previously most prominent absorption features, namely,
the absorption in the region of 250 nm<l<300 nm as well
15 (CH2Cl2, 1.0ꢅ10À5 molLÀ1
)
and either 6ꢅ20 (CH2Cl2, 5.0ꢅ
10À6 molLÀ1
)
(model system 1) or 3ꢅ22 (CH2Cl2, 5.0ꢅ10À6 molLÀ1
)
(model system 2). b) Comparison of the normalized UV/Vis absorption
spectra of 12a and both model systems.
4486
www.chemeurj.org
ꢃ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2013, 19, 4480 – 4495

Molecular Spoked Wheels
FULL PAPER
Figure 9. a) STM image of a self-assembled monolayer of MSW-3a at the
1-octanoic acid/HOPG interface (25.0ꢅ25.0 nm2; VS =À1.5 V; It =5 pA);
b) supramolecular monolayer model. A unit cell of a=(4.1Æ0.1) nm, b=
Figure 8. Comparison of the absorption (black) and emission (gray) spec-
tra of 12a (dashed; for abs: CH2Cl2, 6.7ꢅ10À7 molLÀ1; for em: CH2Cl2,
3.4ꢅ10À8 molLÀ1), MSW-3a (solid; for abs: CH2Cl2, 1.8ꢅ10À6 molLÀ1; for
em: CH2Cl2, 9.0ꢅ10À8 molLÀ1) and 22 (dotted; for abs: CH2Cl2, 5.0ꢅ
10À6 molLÀ1; for em: CH2Cl2, 2.5ꢅ10À7 molLÀ1). A color version of this
plot containing the spectra of 20 is included in the Supporting Informa-
tion.
(4.1Æ0.1) nm, and g
(a,b)=(60Æ1)8 is indexed. The spoke units are
aligned along cn with gACTHUNGTRNEN(UG a,cn)=308+nꢅ608; n=integer. The red, white,
and blue lines indicate the unit cell, HOPG main axis directions, and the
spoke directions, respectively. Note: The hexadecyloxy side chains are
not adsorbed onto the substrate and are thus neglected in the molecular
model in (b).
trum of MSW-3a. In fact, the maximum of the emission
spectrum (Figure 8) is redshifted by 12 nm in the MSW with
respect to the open precursor 12a. At the same time, the
emission spectrum of the MSW is very broad and shows no
distinct features. Considering almost identical emission spec-
tra of 12a and 22, we conclude that in both cases 22 is likely
to be the longest chromophore present.
Self-assembly studies in solution: Neither the UV/Vis ab-
sorption spectrum (in CH2Cl2 over a concentration range
1
from 1ꢅ10À7 to 1ꢅ10À4 molLÀ1) nor the H NMR spectrum
(in [D3]chloroform over
a concentration range from
0.5 mgmLÀ1 (8.3ꢅ10À5 molLÀ1) to 27 mgmLÀ1 (4.4ꢅ
10À3 molLÀ1)) of MSW-3a were concentration-dependent
(the spectra are included in the Supporting Information).
However, these studies are not sufficient to gain insight into
the solution on a molecular level.
Self-assembly studies at the solid/liquid interface: To opti-
mize the MSWs for applications in material science it is im-
portant to analyze their structures in solution as well as on
surfaces and at interfaces. The long hexadecyloxy chains
were introduced to shield the unsaturated moieties, hence,
to reduce p-stacking and to guarantee a high solubility.[45]
As a result, MSW-3a and MSW-3b are highly soluble in
CH2Cl2, THF, and toluene (even more than 10 wt%),
whereas the solubility in pure hexane or methanol remains
low. Owing to steric reasons, MSW-3a and MSW-3b force
the largest parts of the alkoxy chains to be oriented orthog-
onal to the ring plane into the solvent phase. Therefore,
both compounds were barely expected to form monolayers
on highly oriented pyrolytic graphite (HOPG).[46] However,
for MSW-3a we could observe two-dimensional self-assem-
bly at the interface of 1-octanoic acid and HOPG by STM
(see Figure 9a). The molecules form a highly ordered pat-
tern, and a hexagonal unit cell of a=(4.1Æ0.1) nm, b=
Dynamic light scattering (DLS) is especially sensitive to
large particles (scattering intensity scales with approximately
6
Rh , in which Rh =hydrodynamic radius),[47] thus allowing
the determination of very low concentrations of aggregates.
Therefore, chloroform and toluene, which form clear solu-
tions even at weight contents of 10 wt% of MSW-3a, were
chosen for the evaluation of its solubility. The measurements
were conducted at concentrations of 1 mgmLÀ1 (which cor-
responds to 0.1 wt% in toluene and 0.07 wt% in chloro-
form) and 6 mgmLÀ1 (which corresponds to 0.7 wt% in tol-
uene and 0.4 wt% in chloroform). CONTIN[48] (Figure 10a)
as well as cumulant (Figure 10c) analysis reveal almost ex-
clusively the monomer in the solutions in toluene (magenta
and cyan curves), whereas the aggregate accounts for 45%
of the scattered light intensity in the dilute chloroform solu-
tion (Figure 10a, green curve). Although this distribution is
stable over time (Figure 10c), the aggregation process can
be monitored at higher concentrations (Figure 10b). For this
solution (6 mgmLÀ1 in CHCl3) the semilogarithmic plot of
the first cumulant reveals the presence of two regions with
very different behavior (Figure 10c). For t<100 min, aggre-
gation to large particles is very fast but slows down consider-
ably afterwards. By stretching the timescale by logarithmic
plotting (Figure 10d), a linear behavior for t<80 min and a
crossover region until about 300 min is observed, followed
by a linear behavior, now at a reduced rate of aggregation.
(4.1Æ0.1) nm, and g(a,b)=(60Æ1)8 was indexed. The six-
G
fold symmetry of the brightly appearing rigid-rod units
(“spokes”) can be clearly observed. The lattice parameters
of the hexagonal pattern are consistent with the shape and
size of the molecular backbone (see Figure 9b), whereas the
methoxy substituents at the outer corners define the inter-
molecular distances of the rim rod units. The hexadecyloxy
side chains are not observable and are most probably not
adsorbed to the substrate, but rather point to the solution
phase.
Chem. Eur. J. 2013, 19, 4480 – 4495
ꢃ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
4487

S. Fçrster, S. Hçger et al.
by the fast rise of the exponential that corresponds to the
slow process, it stagnates until about 270 min have passed
(Figure 11a), before it begins to decrease slightly, whereas
the autocorrelation curve shifts towards larger relaxation
times (Figure 11b). The integration of the CONTIN distribu-
tion, as well as double-exponential fitting to the autocorrela-
tion curves (details are shown in the Supporting Informa-
tion), give a more differentiated view. After the fast initial
aggregation phase, the ratio of aggregate to monomer
begins to decrease slightly, whereas the aggregate size con-
tinuously grows. Figures 11c,d show the corresponding plots
versus time. The observed behavior is probably the result of
the reorganization of initially formed thermodynamically
unstable aggregates to more regular self-assembled struc-
tures.[49] Considering the abundance of monomers and
rather large aggregates at all times, it can be concluded that
self-assembly follows a cooperative aggregation mechanism
that involves an energy barrier for dimerization.[50] In terms
of solvent quality, chloroform and toluene can be distin-
guished clearly. Whereas chloroform leads to association
even at a concentration of 1 mgmLÀ1 (though never visible
by the bare eye), toluene is a much better solvent for these
systems.
Figure 10. a) CONTIN analysis of solutions of MSW-3a in chloroform
(1 mgmLÀ1 (green), after 21 h) and in toluene (1 (turquoise) and
6 mgmLÀ1 (magenta) after 28 and 25 h, respectively). b) CONTIN analy-
sis of a solution of MSW-3a in chloroform (6 mgmLÀ1) at different times
(succeeding curves have been colored in blue and red for clarity). c) Cu-
mulant analysis: semilogarithmic plot with linear time axis (chloroform:
1 (green) and 6 mgmLÀ1 (blue); toluene: 1 (turquoise) and 6 mgmLÀ1
(magenta)) and d) logarithmic plot of the concentrated sample in chloro-
form (blue, 6 mgmLÀ1) with lines (black, not fitted) emphasizing the
linear behavior for t<80 min and t>300 min obtained from a cumulant
analysis. All values were calculated from autocorrelation curves recorded
at an angle of 308 at 258C.
Small-angle X-ray scattering (SAXS): As mentioned above,
the DLS experiments of solutions in chloroform indicated
the formation of aggregates. To gain a deeper insight into
their structure, SAXS measurements were performed.
Owing to the strong X-ray absorption of chloroform, SAXS
studies in respective solutions were not possible. However,
measurements in toluene could be performed over a range
of concentrations (2.5, 5, and 10%) in the dilute regime.
Figure 12 shows the measured SAXS curves for the three
solutions.
The change in kinetics can also be observed directly by
comparison of the normalized autocorrelation curves (Fig-
ure 11a,b). Over the whole time span, bimodal relaxation
curves are recorded; these correspond to one fast (small par-
ticle, monomer) and one slow (large particle, aggregate) re-
laxation process. Whereas the first 120 min are characterized
Figure 12. SAXS curves measured (gray) for MSW-3a at concentrations
of 2.5, 5, and 10% in toluene with appropriate model curves (black). The
SAXS curve at 2.5% can be described by short disk stacks, whereas at
concentrations of 5 and 10% the scattering curves can be thoroughly de-
scribed by core–shell cylinders.
The black lines are fits to simple geometrical structures.
At a concentration of 2.5% the scattering curve can be
quantitatively described by a disk with a radius of 3.2 nm
and a thickness of 0.6 nm. The measured radius is somewhat
larger than the geometrical radius estimated from Figure 9.
This indicates some aggregate formation, although not yet
Figure 11. Detailed analysis of the aggregation of the MSW-3a sample in
chloroform (6 mgmLÀ1
, angle: 308, T=258C). a,b) Autocorrelation
curves (scattering angle: 458) after a) 10–270 min and b) 270–2480 min.
c,d) Results from CONTIN analysis and double-exponential (DE) fitting
to the autocorrelation curves: c) Ratio of monomer to aggregate versus
time; d) sizes of aggregate and monomer versus time.
4488
www.chemeurj.org
ꢃ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2013, 19, 4480 – 4495

Molecular Spoked Wheels
FULL PAPER
with a well-defined cylindrical structure. At the two higher
concentrations (5 and 10%), the scattering vector (q) de-
pendence of the measured scattering curves differ considera-
bly from the q dependence of the scattering curve measured
at lower concentration. Both scattering curves can be descri-
bed by a core–shell cylinder with a core radius of 0.9 nm, an
overall radius of 1.7 nm, and a length of 25 nm. As the spa-
tial resolution of the experiment is limited by the minimum
q value, this length represents a lower limit. The fit to the
scattering curve is not very sensitive to the core radius, but
in reasonable agreement with aromatic core region of the
molecules. The outer radius is in good agreement with geo-
metrical radius of a cylindrical stacking of the molecules es-
timated from Figure 9 and confirms the preservation of the
noncollapsed planar structure of the MSW in solution.
thesis is based on a modular convex template approach. The
rim module has been prepared by a Hart reaction that has
been optimized for the synthesis of functionalized alkoxy-
containing terphenyls.[51] Furthermore, the cyclization step
has been investigated in detail. To optimize MSWs for
future applications in materials science, we closely looked
into the structure of MSW-3a in solution and on surfaces.
MSW-3a forms a close-packed 2D hexagonal lattice on
HOPG as observed by STM. The self-assembly process in
solution was investigated by DLS and SAXS. We concluded
a cooperative mechanism with a fast initial self-assembly
process followed by a slower reorganization of the aggre-
gates. Furthermore, the shape and dimensions of the self-as-
sembled structures were derived from SAXS measurements
and are in good agreement with the findings from STM.
Moreover, we were able to obtain MSWs in quantities that
were sufficient to initiate investigations on advanced materi-
als. Currently, the applicability of MSW-3a and derivatives
thereof in high-performance nanocomposites are under in-
vestigation.
A sample in the dry state was also investigated by small-
angle X-ray scattering to characterize the self-assembly be-
havior in the bulk. The SAXS curve shows several reflec-
tions, in which the first-order peak (10) is part of a set of
peaks (11, 20) that are consistent with a hexagonal packing
of cylinders (Figure 13). The corresponding cylinder–cylin-
Experimental Section
STM: The experimental setup consisted of an Agilent 5500 SPM system
placed on a Halcyonics active vibration damping platform and was sur-
rounded by a home-built acoustic damping box. Mechanically cut Pt/Ir
(80:20) tips were used and further modified in situ by applying short volt-
age pulses. Highly oriented pyrolytic graphite (HOPG) substrates were
obtained from MikroMasch in ZYB quality and freshly cleaved prior to
each experiment. All STM measurements were performed in situ (with
the tip immersed into the liquid) and typically completed within 30 min
after the sample preparation. As a representative experiment, 1 mL of a
10À5–10À6 m solution of the respective substance in 1-octanoic acid was
dropped onto freshly cleaved HOPG at an elevated temperature (808C),
the temperature was retained for 30 s, and the sample was subsequently
allowed to cool to RT prior to STM imaging. Bias voltages between À0.8
and À1.8 V and current set points between 2 and 30 pA were applied to
image the molecular adlayers. All images were calibrated by subsequent
immediate acquisition of an additional image at reduced bias voltage,
therefore the atomic lattice of the HOPG surface is visible and can be
used as a calibration grid. Data processing, also for image calibration,
was performed using the SPIP 5 (Image Metrology) software package.
Figure 13. SAXS curve of MSW-3a in the dry state. The first-order peak
(10) is part of a set of peaks that are consistent with a hexagonal packing
of cylinders. The corresponding cylinder–cylinder distance of 4.1 nm is in
very good agreement with Figure 9.
der distance of 4.1 nm is in very good agreement with
Figure 9. The two additional reflections at q=2.45 and
2.85 nmÀ1 (2.6 and 2.2 nm, respectively) are due to addition-
al positional correlations of molecules within the cylinders
or correlations of molecules in different (adjacent) cylinders,
but cannot be indexed on any of the two-dimensional space
groups.
Thus the SAXS experiments confirm that rigid molecular
spoked wheels self-assemble into well-defined rigid cylindri-
cal structures, in solution as well as in the bulk, whereby the
cylinders assemble into a hexagonal lattice.
SAXS: SAXS was performed using a rotating anode setup (Seifert) that
consisted of a rotating Cu anode (Rigaku), a Gçbel mirror, and image
plate detectors (Fuji) with a sample detector distance of 1.00 m. The ex-
perimental data were reduced and analyzed using the Scatter software.[52]
Details of the structure and form factors and fitting procedures can be
found in the literature.[53]
DLS: The measurements were conducted using an ALV-CGS-3 system
with a He:Ne laser (632.8 nm) and an ALV/LSE-5004 autocorrelator.
The temperature was regulated using a Thermo Haake Phoenix II thero-
mostat and set to 258C for all measurements. All samples were prepared
in a flow box to ensure a dust-free working environment. Hellma Analyt-
ics 540.110-QS cuvettes (inner diameter 8 mm, V=2.8 mL) were flushed
with distilled acetone and allowed to dry overnight at RT. The samples
were then dissolved in freshly distilled solvents and filtered through hy-
drophobic Rotilabo syringe filters (polytetrafluoroethylene (PTFE);
0.2 mm, 25 mm) into the cuvettes. Then these were immersed into a tol-
uene bath and allowed to equilibrate for 10 min. At regular time inter-
vals, the scattered light was recorded at an angle of 30 and 458. The data
was collected and processed as far as possible using the ALV-Correlator
software, version 3.0.3.2. The CONTIN and cumulant analysis were per-
Conclusion
In conclusion, we have developed and optimized a highly ef-
ficient synthetic route to molecular spoked wheels. The
shape-persistent backbones resemble disklike platelets with
diameters of approximately 4 nm substituted with twelve
alkoxy side chains that point away from the latter. The syn-
Chem. Eur. J. 2013, 19, 4480 – 4495
ꢃ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
4489

S. Fçrster, S. Hçger et al.
formed by the software, whereas the double-exponential fits were done
manually for the given intensity autocorrelation curves g2(t). Details can
be found in the Supporting Information. Diffusion coefficients and hy-
drodynamic radii were obtained using the following solvent data: chloro-
The reaction was diluted by the addition of aqueous NaHSO3 (10%) and
extracted with CH2Cl2. The organic phase was then washed with aqueous
NaHCO3 (saturated), water, and brine. After drying over MgSO4 and re-
moval of the solvent, the crude product was purified by column chroma-
tography (petroleum ether (PE)/CH2Cl2 25:1, Rf =0.29). A white solid
was obtained (3.20 g, 85%) that consisted of an inseparable mixture (3:1
w/w) of the desired 2,4-dichloro-3-iodoanisole (2.04 g, 64%) and the un-
desired 2,4-dichloro-5-iodoanisole (0.80 g, 21%); it was used for the fol-
lowing reaction sequence without further purification. Hart reaction: [2-
(4-bromophenyl)ethynyl]triisopropylsilane (see Figure S2 in the Support-
ing Information) (14.48 g, 42.9 mmol) was dissolved in diethyl ether
(50 mL), cooled to À788C, and tert-butyllithium (1.7m in pentane;
52.4 mL, 89.1 mmol) was added dropwise. Subsequently, the reaction
mixture was stirred for 20 min at this temperature and allowed to warm
to 108C within 1 h. A solution of the aforementioned iodinated product
mixture (2.00 g) in diethyl ether (25 mL) was then added slowly at 108C
to the intensely colored solution (the colors varied from red to blue
among different reactions) of lithiated [2-(4-bromophenyl)ethynyl]triiso-
propylsilane, then stirred for 15 h at RT. The reaction was quenched by
the slow addition of a solution of iodine (16.76 g, 66.0 mmol) in diethyl
ether at 08C. After stirring for another hour, the reaction mixture was
slowly diluted with aqueous NaHSO3 (6%). The layers were separated
and the aqueous phase was extracted twice with CH2Cl2. The combined
organic phases were washed with water and brine. Drying over MgSO4
and removal of the solvent were followed by column chromatography
(PE/CH2Cl2 1:0 to 9:1). [2-(4-Iodophenyl)ethynyl]triisopropylsilane
(8.4 g, colorless liquid) and 2’-iodo-5’-methoxy-4,4’’-bis[2-(triisopropyl-
silyl)ethynyl]-1,1’:3’,1’’-terphenyl (2.70 g, 3.6 mmol, yellow solid, 73%
(only during the last step), 48% (over the whole reaction sequence))
form nD20 =1.44400, h298K =0.54200 cp; toluene nD20 =1.49600, h298K
=
0.55480 cp.
Synthesis, materials, and general equipment: Reagents were purchased at
reagent grade from commercial sources and used without further purifi-
cation. All water- and/or air-sensitive reactions were carried out using
preheated glassware with standard Schlenk techniques under argon.
Unless stated otherwise, all glassware in which the reactions were carried
out was evacuated, heated over 1008C, and flushed with argon prior to
loading with the reagents. Solvents were either purchased in anhydrous
quality (diethyl ether, diisopropylamine) or were dried and distilled ac-
cording to standard methods (THF (dried over Na), piperidine (dried
over CaH2), or CH2Cl2 (dried over CaH2)). Solvents used for workup
were purified by distillation. 1H and 13C NMR spectra were recorded
using a Bruker DPX 300 (1H: 300 MHz, 13C: 75 MHz), DPX 400 (1H:
400 MHz, 13C: 100.6 MHz), or DPX 500 (1H: 500 MHz, 13C: 125.8 MHz)
spectrometer. Chemical shifts are given in parts per million (ppm) refer-
enced to residual 1H or 13C signals in deuterated solvents. Mass spectra
were measured using
a Bruker Daltronics autoflex II TOF/TOF
(MALDI-MS; matrix material: DCTB or dithranol), a Finnigan Thermo-
Quest MAT 95 XL (EI-MS), or an AEI MS-5 (EI-HRMS). Peaks (m/z)
smaller than 10% (relative to the basis peak) are not reported. UV/Vis
absorption spectra were recorded using a Perkin–Elmer Lambda 18 spec-
trophotometer using 0.1, 0.2, 1.0, 10, and 100 mm quartz cuvettes manu-
factured by Hellma. Fluorescence experiments were run on a Perkin–
Elmer LS 50 B spectrofluorometer in all-transparent 10 mm quartz cuv-
ettes by monochromatic excitation at the indicated wavelength. Melting
points were determined using a Leica DMLB microscope with resistive
heating socket controlled using a Leica LMW transformer and a Testo
925 digital thermometer. Thin-layer chromatography (TLC) was conduct-
ed on silica-gel-coated aluminum plates (Macherey–Nagel, Alugram SIL
G/UV254, 0.25 mm coating with fluorescence indicator). For purification
by column chromatography silica gel 60M (Macherey–Nagel, 0.04–
0.063 mm, 230–400 mesh) was used as the stationary phase that was sus-
pended in the indicated solvent. Gel permeation chromatography (GPC,
also size-exclusion chromatography (SEC)) was performed using THF
(HPLC grade, stabilized with 2.5 ppm 2,6-di-tert-butyl-4-methylphenol
(BHT)) at RT. GPC analyses were run using an Agilent Technologies
system at a flow rate of 1 mLminÀ1 using an IsoPump G1310A, a
G1314B VWD detector, and PSS columns (Polymer Standards Service
(PSS), Mainz, Germany; 102, 103, 105, and 106 ꢆ; 5 m; 8ꢅ300 mm). All
molecular weights were determined after polystyrene (PS) calibration
(using PS standard substances obtained from PSS). For the preparative
separation of product mixtures by means of GPC, one of two Shimadzu
recycling GPC systems was used, equipped with an LC-20 AD pump, an
SPD-20A UV detector, and a set of three preparative columns from PSS
(either 103 ꢆ, 5 m, 20ꢅ300 mm, or linear S, 5 m, 20ꢅ300 mm), operated at
a flow rate of 5 mLminÀ1. GC-MS analysis were performed using a Shi-
madzu system equipped with an AOC-20i autoinjector, a GCMS-QP2010
Plus mass spectrometer, and a GC-2010 gas chromatograph with an FS-
Supreme-5MS column (length 30 m, internal diameter 0.25 mm, film
thickness 0.26 mm). The system was operated with helium as carrier gas
in the temperature range of 50–3408C. Microwave-assisted reactions
were performed using a Discover Labmate instrument manufactured by
CEM.
were isolated. 1H NMR (500 MHz, CDCl3, 298 K): d=7.55 (d, 3J
8.5 Hz, 4H), 7.31 (d, 3J
(H,H)=8.5 Hz, 4H), 6.82 (s, 2H), 3.81 (s, 3H),
ACHTUNGTRENNUNG(H,H)=
AHCTUNGTRENNUNG
1.15 ppm (brs, 42H); 13C NMR (125 MHz, CDCl3, 298 K): d=159.25,
148.45, 145.33, 131.79, 129.39, 123.10, 114.93, 106.96, 91.67, 91.41, 55.67,
18.83, 11.47 ppm; MS (EI, 70 eV): m/z calcd for C41H55IOSi2: 746.28;
found (%): 746.2 (5) [M]+, 703.1 (10) [MÀC3H7]+, 544.1 (31)
[MÀC14H34]+, 501.0 (100) [MÀC17H41]+, 473.0 (14) [MÀC17H41Si]+, 459.0
(24) [MÀC18H42Si]+, 445.0 (25) [MÀC19H45Si]+, 431.0 (38) [MÀC6H16I]+.
2’-Iodo-5’-tert-butoxy-4,4’’-bis[2-(triisopropylsilyl)ethynyl]-[1,1’:3’,1’’]-ter-
phenyl (7b): (2-[4-Bromophenyl)ethynyl]triisopropylsilane (see Figure S2
in the Supporting Information) (5.14 g, 13.04 mmol) was dissolved in di-
ethyl ether (10 mL), cooled to À788C, and tert-butyllithium (1.7m in pen-
tane; 15.35 mL, 26.09 mmol) added dropwise. Subsequently, the reaction
mixture was stirred 20 min at this temperature and allowed to warm to
08C within 1 h. Then a solution of 5-tert-butoxy-1,3-dichloro-2-iodoben-
zene (0.50 g, 1.45 mmol) in diethyl ether (10 mL) was added slowly at
08C to the colored solution (colors varied from red to blue among differ-
ent reactions) of lithiated [2-(4-bromophenyl)ethynyl]triisopropylsilane
and stirred for 15 h allowing the mixture to warm to RT. The reaction
was quenched by the slow addition of iodine (4.05 g, 15.94 mmol) in di-
ethyl ether (30 mL) at 08C. After stirring for another two hours, the reac-
tion mixture was slowly diluted with aqueous Na2SO3 (6%). The layers
were separated, and the aqueous phase was extracted twice with CH2Cl2.
The combined organic phases were washed with water and brine. Drying
over MgSO4 and removal of the solvent were followed by repeated
column chromatography (SiO2, PE/CH2Cl2 1:0 to 5:1; Al2O3 (Brockmann
I+6% H2O), PE/CH2Cl2 96:4). [2-(4-Iodophenyl)ethynyl]triisopropylsi-
lane (4.5 g, colorless liquid) and 2’-iodo-5’-tert-butoxy-4,4’’-bis[2-(triiso-
propylsilyl)ethynyl]-1,1’:3’,1’’-terphenyl (0.76 g, 66%) were isolated.
1H NMR (300 MHz, CDCl3, 298 K): d=7.59–7.49 (m, 4H), 7.36–7.27 (m,
4H), 6.90 (s, 2H), 1.37 (s, 9H), 1.15 ppm (s, 42H); 13C NMR (75 MHz,
CDCl3, 298 K): d=155.33, 148.04, 145.24, 131.78, 129.45, 124.34, 123.06,
107.00, 95.16, 91.39, 79.47, 28.97, 18.84, 11.50 ppm; MS (EI, 70 eV): m/z
calcd for C44H61IOSi2: 788.33; found (%): 788.4 (10) [M]+, 732.3 (20)
[MÀC4H8]+, 689.3 (100) [MÀC7H15].
Here the synthesis of the compounds 7a/b (by means of the Hart reac-
tion), 9a/b, 10a/b, 11a/b, 12a/b, MSW-3a, MSW-3b, 20, and 22 is descri-
bed. The synthetic procedures for HPIB, 1, 2, 3, 4, 5a/b, 6a/b, 7a (by
means of amine 3), 8a/b, 14, 15, 17, 18, 20, 22, and for some other com-
pounds known from the literature can be found in the Supporting Infor-
mation.
Compound 9a: Under Ar, [PdACHTNUGTRNEGNU(PPh3)2Cl2] (28 mg, 39 mmol), CuI (12 mg,
2’-Iodo-5’-methoxy-4,4’’-bis[2-(triisopropylsilyl)ethynyl]-[1,1’:3’,1’’]-ter-
phenyl (7a): Iodination: 3,5-Dichloroanisole (2.20 g, 12.43 mmol), [bis-
(trifluoroacetoxy)iodo]benzene (2.84 g, 0.52 mmol), and iodine (1.64 g,
0.52 mmol) were dissolved in CH2Cl2 (60 mL) and stirred at RT for 2.5 h.
64 mmol), and PPh3 (32 mg, 0.12 mmol) were suspended in piperidine
(15 mL), treated in an ultrasonic bath, and carefully degassed at reduced
pressure. Then a solution of 7a (1.48 g, 1.98 mmol) in THF (3 mL) was
added. The mixture was stirred for 15 min, followed by the addition of
4490
www.chemeurj.org
ꢃ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2013, 19, 4480 – 4495

Molecular Spoked Wheels
FULL PAPER
8a (2.03 g, 2.78 mmol) dissolved in THF (2 mL). The reaction was imme-
diately placed into a preheated oil bath at 908C and heated at reflux for
2 h. Then, to make up for the amount of 8a that had been lost due to
side reactions, an additional amount of 8a (0.29 g, 0.39 mmol) in THF
(2 mL) was added to the red solution. After stirring for another 90 min
and cooling to RT, the reaction was diluted with aqueous H2SO4 (10%)
and CH2Cl2. The aqueous phase was extracted another two times with
CH2Cl2. The combined organic phases were washed with aqueous H2SO4
(10%), water, and brine, and then dried over MgSO4. After removal of
the solvent under reduced pressure, the crude product was purified by
column chromatography (PE/CH2Cl2 3:2), and 9a was obtained as a
yellow oil (2.00 g, 75%). 1H NMR (500 MHz, CDCl3, 298 K): d=7.62 (d,
Compound 10b: Under argon, 10b (500 mg, 0.43 mmol) and K2CO3
(658 mg, 4.76 mmol) were suspended in THF (80 mL) and methanol
(32 mL) and stirred for 2 h at RT. Then water and CH2Cl2 were added.
After phase separation and extraction of the aqueous layer, the com-
bined organic phases were washed with aqueous NH4Cl (saturated) and
brine. Then drying over anhydrous MgSO4, removal of the solvent under
reduced pressure, and purification of the residue by column chromatogra-
phy (SiO2, PE/CH2Cl2 1:1) led to 11b as a yellow oil (468 mg, 94%).
1H NMR (500 MHz, CD2Cl2, 298 K): d=7.65 (d, J=8.5 Hz, 4H), 7.55 (d,
J=8.5 Hz, 4H), 7.03 (s, 2H), 6.85 (s, 1H), 6.38 (s, 1H), 3.89 (t, J=6.2 Hz,
2H), 3.78 (t, J=6.8 Hz, 2H), 3.33 (s, 1H), 1.79–1.71 (m, 2H), 1.60–1.43
(m, 4H), 1.42 (s, 9H), 1.26 (m, 34H), 1.16 (s, 42H), 0.91–0.85 ppm (m,
6H); 13C NMR (126 MHz, CD2Cl2, 298 K): d=156.34, 154.34, 153.16,
145.88, 141.44, 132.03, 130.13, 124.44, 123.30, 118.40, 117.02, 115.40,
115.03, 112.53, 107.55, 94.26, 92.69, 91.86, 82.52, 80.61, 80.15, 70.11, 69.68,
32.53, 30.31, 30.29, 30.28, 30.25, 30.23, 30.05, 29.96, 29.91, 29.73, 29.45,
29.29, 26.67, 26.44, 23.29, 19.06, 14.49, 11.95 ppm; MS (MALDI-TOF,
DCTB): m/z calcd for C78H114O3Si2: monoisotopic 1154.83, distr. max
3J
(s, 1H), 6.30 (s, 1H), 3.88 (s, 3H), 3.84 (t, 3J
3J(H,H)=6.7 Hz, 2H), 2.41 (t, 3J
(H,H)=7.0 Hz, 2H), 1.89–1.78 (m, 2H),
1.78–1.69 (m, 2H), 1.52–1.43 (m, 4H), 1.34–1.18 (m, 48H), 1.14 (brs,
42H), 0.88 (t, 3J
(H,H)=7.0, 6H), 0.85–0.80 (m, 2H), 0.24 ppm (s, 6H);
ACHTUNGTRENNUNG ACHTUNGTRENNUNG
(H,H)=8.2 Hz, 4H), 7.53 (d, 3J
AHCTUNGTRENNUNG
A
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
13C NMR (125 MHz, CDCl3, 298 K): d=159.33, 153.98, 152.62, 146.11,
141.07, 131.66, 129.63, 122.91, 119.86, 117.63, 116.43, 115.33, 114.58,
112.72, 112.47, 107.16, 102.91, 97.48, 94.06, 92.02, 91.33, 69.71, 68.95,
55.67, 32.08, 29.94, 29.91, 29.87, 29.83, 29.75, 29.52, 29.50, 29.00, 26.37,
26.00, 22.85, 20.78, 20.60, 18.86, 15.89, 14.28, 11.50, À1.61 ppm; MS
(MALDI-TOF, DCTB): m/z calcd for C89H135NO3Si3: monoisotopic
1349.98, distr. max 1351.29; found: 1349.9 [M]+; GPC (in THF versus
1155.91; found: 1154.8 [M]+ 1110.0 [MÀC3H8]+, 1098.7 [MÀC4H8]+;
,
GPC (in THF versus PS): Mp =1451 gmolÀ1
.
Compound 11a: Compound 10a (1404 mg, 1.123 mmol) was dissolved in
THF and transferred to the reaction flask. After removal of the solvent
under reduced pressure [PdACHTNUGTRNEGNU(PPh3)2Cl2] (53 mg, 75 mmol), CuI (24 mg,
126 mmol), PPh3 (53 mg, 201 mmol), hexa(4-iodophenyl)benzene (HPIB;
162 mg, 126 mmol), and piperidine (5 mL) were added. While treating the
suspension in an ultrasonic bath, it was degassed by carefully reducing
the pressure and refilling the flask with argon repeatedly. The mixture
was then immediately immersed into a preheated oil bath and stirred at
808C overnight. After cooling to RT, the reaction mixture was diluted
with water (40 mL) and CH2Cl2. The organic phase was washed succes-
sively with aqueous H2SO4 (10%), water, and brine, and then dried over
MgSO4. The crude product was purified by column chromatography
(twice, starting with PE/CH2Cl2 =7:2 up to PE/CH2Cl2 =2:1), and 11a
was obtained as a yellow oil (755 mg, 76%). 1H NMR (500 MHz, CDCl3,
PS): Mp =1713 gmolÀ1
Compound 9b: Compound 7b (420 mg, 532 mmol), 8b (594 mg,
958 mmol), [PdCl2A(PPh3)2] (19 mg, 27 mmol), CuI (14 mg, 75 mmol), and
.
CHTUNGTRENNUNG
PPh3 (20 mg, 75 mmol) were transferred into a microwave tube. It was
evacuated for 1 h and finally refilled with argon. The contents were dis-
solved in piperidine (3.5 mL) and THF (4.0 mL), and reacted in the mi-
crowave (max power 300 W, 1208C, 12 min). After cooling to RT, the re-
action was diluted with aqueous NH4Cl (saturated) and CH2Cl2. The or-
ganic phase was washed with aqueous NH4Cl (saturated), water, and
brine, and then dried over MgSO4. After removal of the solvent under re-
duced pressure, the crude product was purified by column chromatogra-
phy (PE/EtOAc 24:1), and 9b was obtained as yellow oil (526 mg, 81%).
1H NMR (400 MHz, CD2Cl2, 298 K): d=7.69–7.62 (m, 4H), 7.59–7.52 (m,
298 K): d=7.62 (d, 3J
A
ACHTUNGTREN(NUNG H,H)=8.2 Hz,
24H), 7.03 (d, 3J
A
3
(d, J
A
A
4H), 7.02 (s, 2H), 6.80 (s, 1H), 6.37 (s, 1H), 3.87 (t, 3J
(H,H)=6.1 Hz,
6.0 Hz, 12H), 3.72 (t, JACHTUNTGRENNUNG
3
2H), 3.78 (t, 3J(H,H)=6.7 Hz, 2H), 2.42 (t, 3J
G
E
ACHTUNGTRENNUNG
1.70 (m, 4H), 1.56–1.46 (m, 4H), 1.42 (s, 9H), 1.39–1.20 (m, 32H), 1.16
(s, 42H), 0.95–0.79 (m, 8H), 0.28–0.22 ppm (m, 6H); 13C NMR
(101 MHz, CD2Cl2, 298 K): d=156.34, 154.39, 153.19, 145.86, 141.45,
132.02, 130.12, 124.43, 123.30, 120.26, 117.87, 116.95, 115.32, 115.04,
113.34, 107.57, 103.08, 98.24, 94.37, 92.82, 91.86, 80.15, 70.12, 69.54, 32.53,
30.35, 30.31, 30.29, 30.25, 30.13, 29.99, 29.96, 29.93, 29.49, 29.31, 26.79,
26.46, 23.29, 21.24, 20.96, 19.08, 16.22, 14.48, 11.97, À1.53 ppm; MS
(MALDI-TOF, DCTB): m/z calcd for C84H125NO3Si3: monoisotopic
1279.90, distr. max: 1281.15; found: 1279.9 [M]+, 1235.1 [MÀC3H8]+,
6.9 Hz, 36H); 13C NMR (125 MHz, CDCl3, 298 K): d=159.17, 153.23,
152.69, 145.98, 141.10, 140.13, 139.95, 131.63, 131.32, 130.47, 129.61,
122.87, 121.03, 117.07, 116.57, 114.55, 114.35, 113.48, 112.91, 107.19, 94.82,
93.65, 92.40, 91.23, 86.55, 69.52, 69.07, 55.63, 32.11, 32.10, 29.97, 29.96,
29.95, 29.90, 29.88, 29.86, 29.84, 29.81, 29.61, 29.57, 29.54, 29.36, 29.01,
26.27, 26.07, 22.87, 22.86, 18.83, 14.29, 11.48 ppm; MS (MALDI-TOF,
DCTB): m/z calcd for C540H762O18Si12: monoisotopic 7871.59, distr. max
7878.84); found: 7877.5 [M]+, 7905.8 [M+C2H4]+; GPC (in THF versus
PS): Mp =6550 gmolÀ1
.
1223.8 [MÀC4H9]+; GPC (in THF versus PS): Mp =1713 gmolÀ1
.
Compound 11b: [PdCl2ACHNUTTGREGN(NUN PPh3)2] (14 mg, 20 mmol), CuI (6 mg, 33 mmol),
Compound 10a: Under argon, 9a (800 mg, 0.59 mmol) and K2CO3
(812 mg, 5.92 mmol) were suspended in THF (110 mL) and methanol
(45 mL) and stirred for 2 h at RT before the reaction was diluted with
water (50 mL) and CH2Cl2 (100 mL). After phase separation and extrac-
tion of the aqueous layer, the combined organic phases were washed
with aqueous H2SO4 (10%), water, and brine. After drying over anhy-
drous MgSO4 and removal of the solvent under reduced pressure, the res-
idue was purified by flash chromatography. Compound 10a was obtained
as a yellow oil (660 mg, 91%). 1H NMR (400 MHz, CDCl3, 298 K): d=
PPh3 (14 mg, 52 mmol), and hexa(4-iodophenyl)benzene were dissolved in
piperidine (5 mL) and degassed by passing Ar through the solution
(30 min). At the same time, 10b (338 mg, 0.293 mmol) was dissolved in
THF (1.5 mL) and degassed by passing Ar through the solution (20 min).
Finally, the catalyst mixture was heated to 808C and the solution of 10b
was added within 10 min. After stirring overnight at 808C, the reaction
was cooled to RT and diluted with water and CH2Cl2. The organic phase
was washed successively with aqueous NH4Cl (saturated), water, and
brine, and then dried over MgSO4. The crude product was purified by
column chromatography (PE/CH2Cl2 2:1 to 1:1) and recycling GPC
(SEC) to yield 11b as a yellow oil (187 mg, 25 mmol, 77%). 1H NMR
7.63 (d, 3J
2H), 6.82 (s, 1H), 6.33 (s, J
(t, 3J
(H,H)=6.8 Hz, 2H), 3.28 (s, 1H), 1.80–1.68 (m, 2H), 1.52–1.38 (m,
4H), 1.24 (m, 48H), 1.15 (s, 42H), 0.88 ppm (t, 3J
(H,H)=6.8 Hz, 6H);
ACHTUNGTRENNUNG ACHTUNGTRENNUNG
(H,H)=8.4 Hz, 4H), 7.54 (d, 3J
3
AHCTUNGTRENNUNG
T
(400 MHz, CD2Cl2, 298 K): d=7.62 (d, 3J
3J(H,H)=8.4 Hz, 24H), 7.06 (d, 3J(H,H)=8.3 Hz, 12H), 6.99 (s, 3J-
(H,H)=3.4 Hz, 12H), 6.81 (d, 3J
(H,H)=8.3 Hz, 12H), 6.77 (s, 6H), 6.31
(s, 6H), 3.84 (t, 3J(H,H)=6.0 Hz, 12H), 3.73 (t, 3J
(H,H)=6.7 Hz, 12H),
ACHTUNGTNER(NUNG H,H)=8.4 Hz, 24H), 7.52 (d,
N
A
ACHTUNGTRENNUNG
13C NMR (101 MHz, CDCl3, 298 K): d=159.35, 153.90, 152.65, 146.13,
141.09, 131.66, 129.63, 122.93, 118.22, 116.74, 115.40, 114.59, 112.76,
111.96, 107.18, 93.92, 91.91, 91.35, 82.03, 80.33, 69.75, 69.27, 55.67, 32.09,
29.87, 29.82, 29.80, 29.64, 29.53, 29.48, 29.23, 28.97, 26.25, 25.99, 22.85,
18.86, 14.27, 11.52 ppm; MS (MALDI-TOF, DCTB): m/z calcd for
C83H124O3Si2: monoisotopic 1224.91, distr. max 1226.04); found: 1224.9
A
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
1.78–1.65 (m, 12H), 1.50–1.43 (m, 24H), 1.43–1.38 (m, 54H), 1.37–1.16
(m, 192H), 1.16–1.07 (m, 252H), 0.86 ppm (m, 36H); 13C NMR
(126 MHz„ 298 K): d=155.39, 153.24, 152.79, 145.29, 140.98, 140.12,
140.10, 139.97, 131.62, 131.32, 130.48, 129.65, 124.00, 122.78, 121.02,
117.09, 116.62, 115.02, 114.22, 113.64, 107.21, 94.89, 93.60, 93.00, 91.20,
[M]+; GPC (in THF versus PS): Mp =1599 gmolÀ1
.
Chem. Eur. J. 2013, 19, 4480 – 4495
ꢃ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
4491

S. Fçrster, S. Hçger et al.
86.52, 79.66, 69.55, 69.07, 32.14, 32.07, 29.87, 29.84, 29.81, 29.62, 29.60,
29.52, 29.50, 29.39, 29.08, 28.98, 26.30, 26.03, 22.89, 22.84, 18.83, 14.31,
14.28, 11.48 ppm; MS (MALDI-TOF, DCTB): m/z calcd for
3.75 (t, 3J
1.40–1.03 (m, 300H), 0.86 (t, 3J
(H,H)=7.0 Hz, 18H); 13C NMR (125 MHz, CDCl3, 298 K): d=159.39,
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
C
510H702O18Si12: monoisotopic 7451.12, distr. max 7458.05: found: 7457.0
153.12, 153.02, 145.75, 141.87, 140.06, 139.98, 132.12, 131.34, 130.65,
129.96, 121.16, 120.75, 117.43, 116.38, 114.45, 114.04, 113.59, 113.16, 94.56,
92.95, 92.12, 86.22, 81.63, 74.69, 69.63, 69.51, 55.71, 32.09, 29.96, 29.91,
29.89, 29.85, 29.84, 29.79, 29.67, 29.65, 29.55, 29.35, 29.14, 26.12, 26.05,
22.86, 14.29 ppm; MS (MALDI-TOF, DCTB): m/z calcd for C432H510O18,
monoisotopic 5985.90, distr max 5990.66: found: 5990.7 [M]+, 6018.5
[M]+, 7401.9 [MÀC4H9]+; GPC (in THF versus PS): Mp =6253 gmolÀ1
.
Compound 12a: Compound 11a (745 mg, 95 mmol) was dissolved in THF
(130 mL) and degassed by ultrasonication under slightly reduced pres-
sure. The solution was cooled to 08C, and a solution of TBAF in THF
(1m, 14.2 mL, 14.2 mmol) was added at once. Then the reaction was stir-
red at room temperature for 3 h and diluted with water. Extraction with
CH2Cl2 was followed by successive washings with aqueous H2SO4 (10%),
water, and brine, then drying over MgSO4, and finally removal of the sol-
vent gave the crude product. This was purified by flash chromatography
[M+C2H4]+; GPC (in THF versus PS): Mp =5555 gmolÀ1
.
Compound MSW-3b: CuI (6.5 mg, 33.9 mmol) and iodine (22.0 mg,
96.8 mmol) were dissolved in THF (75 mL) and diisopropyl amine
(70 mL). This solution was saturated with air by bubbling it through the
1
(PE/CH2Cl2 30:1) to yield 12a as a yellow solid (555 mg, 98%). H NMR
(500 MHz, CDCl3, 298 K): d=7.62 (d, J
solution for 1 h. Then [PdACTHNGUTERNNU(G PPh3)2Cl2] (13.6 mg, 19 mmol) was added, and
3
3
N
the solution heated to 508C. Under vigorous stirring, a solution of 12b
(27.0 mg, 4.84 mmol) in THF (30 mL) was added with a constant rate
over 48 h to the catalyst solution held at 508C. The reaction was diluted
with water and CH2Cl2, and the organic phase was washed successively
with aqueous NH4Cl (saturated), aqueous Na2SO3 (10%), and brine, and
then dried over MgSO4. After removal of the solvent, the crude product
was purified by column chromatography (SiO2, cyclohexane/CH2Cl2
12:11) and recycling GPC (SEC) by using THF as eluent. To remove
BHT, the vials that contained the product were combined, the solvent re-
moved, and the product precipitated from CH2Cl2 and methanol. After
filtration, MSW-3b was obtained as a yellow solid (18.0 mg, 68%).
3
(H,H)=8.4 Hz, 24H), 7.02 (d, J
N
(s, 6H), 6.72 (d, 3J
A
3
3
(t, J
(H,H)=6.3 Hz, 12H), 3.71 (t, J
1.86–1.69 (m, 12H), 1.51–1.41 (m, 24H), 1.38–1.14 (m, 288H), 0.87 ppm
(t, 3J(H,H)=7.8 Hz, 36H); 13C NMR (125 MHz, CDCl3, 298 K) d=
ACHTUNGTRENNUNG
159.23, 153.44, 152.56, 145.89, 141.61, 140.11, 139.98, 131.79, 131.34,
130.46, 129.75, 121.41, 120.99, 117.01, 116.34, 114.51, 114.14, 113.39,
113.12, 94.93, 93.70, 92.57, 86.45, 83.73, 77.88, 69.67, 69.14, 55.68, 32.10,
32.09, 29.95, 29.94, 29.93, 29.92, 29.89, 29.86, 29.84, 29.82, 29.57, 29.56,
29.54, 29.48, 29.42, 29.11, 26.16, 25.96, 22.86, 22.86, 14.30, 14.29 ppm; MS
(MALDI-TOF, DCTB): m/z calcd for C432H522O18: monoisotopic 5997.99,
distr. max 6002.76; found: 6003.0 [M]+, 6031.8 [M+C2H4]+; GPC (in
1H NMR (500 MHz, 298 K): d=7.70 (d, 3J
3J(H,H)=8.5 Hz, 24H), 7.11 (d, 3J
(H,H)=8.4 Hz, 12H), 7.08 (s, 12H),
6.88–6.83 (m, 18H), 6.48 (s, 6H), 3.89 (t, 3J
(H,H)=6.7 Hz, 12H), 3.78 (t,
3J
(H,H)=7.1 Hz, 12H), 1.82–1.73 (m, 12H), 1.51–1.45 (m, 12H), 1.44 (s,
ACHTUNGTNER(NUNG H,H)=8.4 Hz, 24H), 7.61 (d,
A
ACHTUNGTRENNUNG
THF versus PS): Mp =5922 gmolÀ1
.
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
Compound 12b: Compound 11b (187 mg, 25 mmol) was dissolved in THF
(35 mL) and degassed by ultrasonication under reduced pressure. The
solution was cooled to 08C, and a solution of TBAF in THF (1m, 6.0 mL,
6.0 mmol) was added at once. The reaction was stirred at room tempera-
ture for 3 h and diluted with water. Extraction with CH2Cl2 followed by
successive washings with aqueous NH4Cl (saturated), water, and brine,
and then drying over MgSO4 prior to removal of the solvent gave the
crude product. This was purified by flash chromatography (cyclohexane/
CH2Cl2 1:1) to yield 12b as a yellow oil (103 mg, 74%). 1H NMR
(500 MHz, CD2Cl2) d=7.67–7.61 (m, 24H), 7.59–7.52 (m, 24H), 7.06 (d,
54H), 1.38–1.13 (m, 216H), 0.83 ppm (m, 36H); 13C NMR (126 MHz,
298 K): d=156.32, 153.52, 153.41, 145.54, 142.28, 140.76, 140.37, 132.53,
131.94, 130.73, 130.43, 124.40, 121.38, 121.27, 117.74, 116.69, 115.51,
114.20, 113.89, 94.65, 93.41, 92.89, 86.83, 81.97, 80.23, 74.92, 70.01, 69.89,
32.57, 32.50, 30.37, 30.34, 30.30, 30.28, 30.24, 30.12, 30.08, 30.01, 29.98,
29.80, 29.55, 29.27, 26.59, 26.46, 23.28, 14.50, 14.46 ppm; MS (MALDI-
TOF, DCTB): m/z calcd for C402H450O18: monoisotopic 5565.43, distr max
5569.86; found: 5569.9 [M]+, 5513.2 [MÀC4H8]+; GPC (in THF versus
PS): Mp =5289 gmolÀ1
.
3J
6.78 (s, 6H), 6.20 (s, 6H), 3.79 (t, 3J
(H,H)=7.0 Hz, 12H), 3.14 (s, 12H), 1.80–1.70 (m, 12H), 1.52–1.44 (m,
A
R
Compound 20: 4-Iodo-1,1’-biphenyl (32.9 mg, 0.118 mmol), CuI (2.6 mg,
0.014 mmol), [Pd2A(dba)3] (4.1 mg, 0.005 mmol), and (diphenylphosphino)-
E
CHTUNGTRENNUNG
G
ferrocene (dppf; 4.9 mg, 0.009 mmol) were dissolved in THF (2 mL) and
piperidine (5 mL) in a microwave tube. After sealing the tube and purg-
ing the solution for 30 min with argon, compound 18 (80.0 mg,
0.112 mmol) was added, and the mixture was heated under microwave ir-
radiation (1208C, 12 min, max power 300 W). The reaction was diluted
with CH2Cl2 and washed with aqueous H2SO4 (10%), water, and brine,
and then dried over MgSO4. Filtration and removal of the solvent fol-
lowed by column chromatography (cyclohexane/CH2Cl2 5:1) and recrys-
24H), 1.43–1.40 (m, 54H), 1.37–1.16 (m, 204H), 0.86 ppm (m, 36H);
13C NMR (101 MHz, CD2Cl2, 298 K) d=156.22, 153.89, 153.13, 145.66,
141.95, 140.69, 140.54, 132.19, 131.93, 130.70, 130.22, 124.39, 121.80,
121.44, 117.36, 116.80, 115.41, 114.41, 113.89, 95.13, 94.08, 93.35, 86.89,
83.98, 80.15, 78.28, 70.10, 69.67, 32.57, 32.51, 30.33, 30.31, 30.27, 30.24,
30.23, 30.20, 30.02, 30.00, 29.95, 29.91, 29.87, 29.54, 29.29, 26.65, 26.36,
23.33, 23.28, 14.53, 14.48 ppm; MS (MALDI-TOF, DCTB): m/z calcd for
C
402H462O18: monoisotopic 5577.52, distr max 5581.96; found: 5582.0 [M]+;
GPC (in THF versus PS): Mp =5622 gmolÀ1
tallization from ethanol yielded 20 as a yellow solid (74.6 mg,
.
0.086 mmol, 77%). M.p. 788C; 1H NMR (400 MHz, CD2Cl2, 298 K): d=
7.69–7.57 (m, 6H), 7.53–7.43 (m, 4H), 7.38 (m, 1H), 7.04 (s, 1H), 7.02 (s,
1H), 6.95–6.87 (m, 2H), 4.04 (m, 4H), 3.83 (s, 3H), 1.92–1.79 (m, 4H),
1.62–1.50 (m, 4H), 1.45–1.19 (m, 48H), 0.87 ppm (m, 6H); MS (EI,
70 eV): m/z calcd for C61H84O3: 865.32: found (%): 864.6 (100) [M]+,
640.4 (10) [MÀC16H32]+, 429.1 (20) [MÀC31H63]+, 401.1 (20)
[MÀC33H67]+; 387.1 (12) [MÀC33H67O]+.
Compound MSW-3a: Compound 12a (200 mg, 33.3 mmol) was dissolved
in THF (25 mL) and added with a constant rate over 90 h to a solution of
[PdACHTUNGTRENNUNG(PPh3)2Cl2] (28 mg, 40 mmol), CuI (12 mg, 62 mmol), and iodine
(56 mg, 220 mmol) in THF (50 mL) and diisopropyl amine (60 mL) at
508C. After the addition was completed, the syringe was refilled trice
with THF (7 mL), and the solutions were added over 90 min to the cata-
lyst system. The reaction was cooled to RT and diluted with water
(200 mL) and CH2Cl2. The organic phase was washed successively with
aqueous H2SO4 (10%), aqueous NaHSO3 (10%), water, and brine, and
then dried over MgSO4. After removal of the solvent, the crude product
was filtered over SiO2 (PE/CH2Cl2 1:4) and purified by recycling GPC by
using THF as eluent. To remove BHT, the vials that contained the prod-
uct were combined, the solvent removed, and the product precipitated
from CH2Cl2 and methanol. After filtration, MSW-3a was obtained as a
yellow solid (158 mg, 79%). 1H NMR (500 MHz, CDCl3, 298 K): d=7.68
Compound 22: 4,4’’-Diiodo-p-terphenyl (11.0 mg, 22.8 mmol), CuI
(0.5 mg, 2.5 mmol), [PdACTHNUTRGNEUNG(PPh3)2Cl2] (1.0 mg, 1.4 mmol), and PPh3 (1.2 mg,
4.6 mmol) were dissolved in THF (1 mL) and piperidine (4 mL) in a mi-
crowave tube. Compound 18 (34.2 mg, 47.9 mmol) was added and the
mixture was heated under microwave irradiation (1208C, 12 min, max
power 300 W). After cooling to RT, the reaction was diluted with methyl
tert-butyl ether (MTBE) and CH2Cl2, and washed with aqueous H2SO4
(10%), water, and brine, followed by drying over MgSO4. Filtration and
removal of the solvent followed by column chromatography (cyclohex-
ane/CH2Cl2 2:1) gave a crude product. Further purification involved re-
crystallization from hot chloroform and methanol and recycling GPC
(SEC) of the solid. Compound 22 (27 mg, 16.3 mmol, 72%) was obtained
(d, 3J
(H,H)=8.3 Hz, 12H), 6.96 (s, 12H), 6.84 (s, 6H), 6.74 (d, 3J
8.3 Hz, 12H), 6.44 (s, 6H), 3.91 (s, 18H), 3.87 (t, 3J
(H,H)=6.6 Hz, 12H),
ACHTUNGTRENNUNG ACHTUNGTRENNUNG
(H,H)=8.4 Hz, 24H), 7.58 (d, 3J
N
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
4492
www.chemeurj.org
ꢃ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2013, 19, 4480 – 4495

Molecular Spoked Wheels
FULL PAPER
as a yellow solid. 1H NMR (400 MHz, CDCl3, 298 K): d=7.71 (s, 4H),
7.68–7.59 (m, 8H), 7.51–7.45 (m, 4H), 7.03 (s, 2H), 7.01 (s, 2H), 6.93–
6.85 (m, 4H), 4.04 (m, 8H), 3.84 (s, 6H), 1.92–1.80 (m, 8H), 1.64–1.49
(m, 8H), 1.47–1.17 (m, 96H), 0.93–0.83 ppm (m, 12H); 13C NMR
(101 MHz, CDCl3, 298 K): d=159.82, 153.89, 153.66, 140.31, 139.71,
133.21, 132.21, 127.56, 126.97, 122.80, 117.15, 117.01, 115.78, 114.67,
114.13, 113.71, 95.18, 94.77, 87.14, 84.84, 69.85, 69.82, 55.44, 32.08, 29.88,
29.87, 29.84, 29.82, 29.80, 29.62, 29.62, 29.55, 29.52, 26.28, 26.25, 22.84,
14.27 ppm; MS (MALDI-TOF, DCTB): m/z calcd for C116H162O6: mono-
isotopic 1651.24, distr max 1652.52); found: 1651.2 [M]+.
Zhao, J. S. Moore, L. Zang, J. Am. Chem. Soc. 2007, 129, 6978–
6979; h) M. Fritzsche, A. Bohle, D. Dudenko, U. Baumeister, D. Se-
bastiani, G. Richardt, H. W. Spiess, M. R. Hansen, S. Hçger, Angew.
Chem. 2011, 123, 3086–3089; Angew. Chem. Int. Ed. 2011, 50, 3030–
3033; i) S. Hçger, X. H. Cheng, A. D. Ramminger, V. Enkelmann,
A. Rapp, M. Mondeshki, I. Schnell, Angew. Chem. 2005, 117, 2862–
2866; Angew. Chem. Int. Ed. 2005, 44, 2801–2805; j) S. Hçger, V.
Enkelmann, K. Bonrad, C. Tschierske, Angew. Chem. 2000, 112,
2356–2358; Angew. Chem. Int. Ed. 2000, 39, 2268–2270; k) S.
Hçger, Chem. Eur. J. 2004, 10, 1320–1329; l) O. Y. Mindyuk, M. R.
Stetzer, P. A. Heiney, J. C. Nelson, J. S. Moore, Adv. Mater. 1998, 10,
1363–1366; m) S. H. Seo, T. V. Jones, H. Seyler, J. O. Peters, T. H.
Kim, J. Y. Chang, G. N. Tew, J. Am. Chem. Soc. 2006, 128, 9264–
9265.
[6] a) S. Hçger, K. Becker, G. Gaefke, J. Rolffs, J. M. Lupton, Chem.
Commun. 2010, 4686–4688; b) J. Luo, Q. Yan, Y. Zhou, T. Li, N.
Zhu, C. Bai, Y. Cao, J. Wang, J. Pei, D. Zhao, Chem. Commun.
2010, 46, 5725–5727.
[7] S. Dawn, M. B. Dewal, D. Sobransingh, M. C. Paderes, A. C.
Wibowo, M. D. Smith, J. A. Krause, P. J. Pellechia, L. S. Shimizu, J.
Am. Chem. Soc. 2011, 133, 7025–7032.
Acknowledgements
This work was financially supported by the Deutsche Forschungsgemein-
schaft (DFG), the Sonderforschungsbereich (SFB) 624, and the Fonds
der Chemischen Industrie (FCI).
[8] a) S. Furukawa, K. Tahara, F. C. De Schryver, M. Van der Auweraer,
Y. Tobe, S. De Feyter, Angew. Chem. 2007, 119, 2889–2892; Angew.
Chem. Int. Ed. 2007, 46, 2831–2834; b) S. Furukawa, H. Uji-i, K.
Tahara, T. Ichikawa, M. Sonoda, F. C. De Schryver, Y. Tobe, S. De
Feyter, J. Am. Chem. Soc. 2006, 128, 3502–3503; c) S. B. Lei, K.
Tahara, F. C. De Schryver, M. Van der Auweraer, Y. Tobe, S. De
Feyter, Angew. Chem. 2008, 120, 3006–3010; Angew. Chem. Int. Ed.
2008, 47, 2964–2968; d) J. Adisoejoso, K. Tahara, S. Okuhata, S. Lei,
Y. Tobe, S. De Feyter, Angew. Chem. 2009, 121, 7489–7493; Angew.
Chem. Int. Ed. 2009, 48, 7353–7357; e) K. Tahara, S. Okuhata, J.
Adisoejoso, S. B. Lei, T. Fujita, S. De Feyter, Y. Tobe, J. Am. Chem.
Soc. 2009, 131, 17583–17590; f) K. Tahara, S. B. Lei, J. Adisoejoso,
S. De Feyter, Y. Tobe, Chem. Commun. 2010, 46, 8507–8525; g) S.-S.
Jester, D. Schmitz, F. Eberhagen, S. Hçger, Chem. Commun. 2011,
47, 8838–8840; h) S.-S. Jester, E. Sigmund, S. Hçger, J. Am. Chem.
Soc. 2011, 133, 11062–11065; i) S.-S. Jester, N. Shabelina, S. M. Le B-
lanc, S. Hçger, Angew. Chem. 2010, 122, 6237–6241; Angew. Chem.
Int. Ed. 2010, 49, 6101–6105; j) J. A. A. W. Elemans, S. B. Lei, S. De
Feyter, Angew. Chem. 2009, 121, 7434–7469; Angew. Chem. Int. Ed.
2009, 48, 7298–7332; k) T. Chen, G.-B. Pan, H. Wettach, M. Fritz-
sche, S. Hçger, L. J. Wan, H. B. Yang, B. H. Northrop, P. J. Stang, J.
Am. Chem. Soc. 2010, 132, 1328–1333; l) G.-B. Pan, X. H. Cheng, S.
Hçger, W. Freyland, J. Am. Chem. Soc. 2006, 128, 4218–4219.
[9] a) J. A. Marsden, J. J. Miller, M. M. Haley, Angew. Chem. 2004, 116,
1726–1729; Angew. Chem. Int. Ed. 2004, 43, 1694–1697; b) W.
Zhang, J. S. Moore, J. Am. Chem. Soc. 2005, 127, 11863–11870;
c) W. Zhang, J. S. Moore, J. Am. Chem. Soc. 2004, 126, 12796–
12796; d) D. E. Gross, J. S. Moore, Macromolecules 2011, 44, 3685–
3687; e) A. J. Gallant, M. J. MacLachlan, Angew. Chem. 2003, 115,
5465–5468; Angew. Chem. Int. Ed. 2003, 42, 5307–5310; f) I. Hisaki,
Y. Sakamoto, H. Shigemitsu, N. Tohnai, M. Miyata, S. Seki, A.
Saeki, S. Tagawa, Chem. Eur. J. 2008, 14, 4178–4187.
[1] a) J. S. Moore, J. S. Zhang, Angew. Chem. 1992, 104, 873–874;
Angew. Chem. Int. Ed. Engl. 1992, 31, 922–924; b) F. Diederich,
Nature 1994, 369, 199–207; c) M. M. Haley, Synlett 1998, 557–565;
d) Q. Zhou, P. J. Carroll, T. M. Swager, J. Org. Chem. 1994, 59,
1294–1301; e) H. A. Staab, K. Neunhoeffer, Synthesis 1974, 424–
424; f) G. Eglinton, A. R. Galbraith, Proc. Chem. Soc. 1957, 350–
351; g) O. M. Behr, G. Eglinton, A. R. Galbraith, R. A. Raphael, J.
Chem. Soc. 1960, 3614–3625; h) E. L. Spitler, C. A. Johnson, M. M.
Haley, Chem. Rev. 2006, 106, 5344–5386; i) H. A. Staab, F. Graf, Tet-
rahedron Lett. 1966, 7, 751–757; j) H. A. Staab, J. Ipaktschi, A.
Nissen, Chem. Ber. Recl. 1971, 104, 1182–1190; k) I. D. Campbell,
G. Eglinton, W. Henderson, R. A. Raphael, J. Chem. Soc. Chem.
Commun. 1966, 87–89; l) M. Nakagawa, Pure Appl. Chem. 1975, 44,
885–924; m) M. Nakagawa, Angew. Chem. 1979, 91, 215–226;
Angew. Chem. Int. Ed. Engl. 1979, 18, 202–214; n) H. N. C. Wong,
P. J. Garratt, F. Sondheimer, J. Am. Chem. Soc. 1974, 96, 5604–5605;
o) F. Sondheimer, Acc. Chem. Res. 1972, 5, 81–91.
[2] a) W. Zhang, J. S. Moore, Angew. Chem. 2006, 118, 4524–4548;
Angew. Chem. Int. Ed. 2006, 45, 4416–4439; b) J. Sakamoto, J. van
Heijst, O. Lukin, A. D. Schlꢁter, Angew. Chem. 2009, 121, 1048–
1089; Angew. Chem. Int. Ed. 2009, 48, 1030–1069; c) J. S. Moore,
Acc. Chem. Res. 1997, 30, 402–413; d) U. H. F. Bunz, Y. Rubin, Y.
Tobe, Chem. Soc. Rev. 1999, 28, 107–119; e) W. B. Wan, M. M.
Haley, J. Org. Chem. 2001, 66, 3893–3901; f) T. Yoshimura, A.
Inaba, M. Sonoda, K. Tahara, Y. Tobe, R. V. Williams, Org. Lett.
2006, 8, 2933–2936; g) W. B. Wan, S. C. Brand, J. J. Pak, M. M.
Haley, Chem. Eur. J. 2000, 6, 2044–2052; h) M. M. Haley, S. C.
Brand, J. J. Pak, Angew. Chem. 1997, 109, 863–866; Angew. Chem.
Int. Ed. Engl. 1997, 36, 836–838; i) I. Hisaki, M. Sonoda, Y. Tobe,
Eur. J. Org. Chem. 2006, 833–847; j) S. Hçger, J. Polym. Sci. Part A
1999, 37, 2685–2698; k) S. Hçger, A. D. Meckenstock, Chem. Eur. J.
1999, 5, 1686–1691.
[10] a) D. Mçssinger, D. Chaudhuri, T. Kudernac, S. Lei, S. De Feyter,
J. M. Lupton, S. Hçger, J. Am. Chem. Soc. 2010, 132, 1410–1423;
b) S. Lei, A. Ver Heyen, S. De Feyter, M. Surin, R. Lazzaroni, S.
Rosenfeldt, M. Ballauff, P. Lindner, D. Mçssinger, S. Hçger, Chem.
Eur. J. 2009, 15, 2518–2535; c) D. Mçssinger, J. Hornung, S. Lei, S.
De Feyter, S. Hçger, Angew. Chem. 2007, 119, 6926–6930; Angew.
Chem. Int. Ed. 2007, 46, 6802–6806.
[11] a) T. C. Bedard, J. S. Moore, J. Am. Chem. Soc. 1995, 117, 10662–
10671; b) J. A. Marsden, M. J. OꢄConnor, M. M. Haley, Org. Lett.
2004, 6, 2385–2388; c) M. Laskoski, W. Steffen, J. G. M. Morton,
M. D. Smith, U. H. F. Bunz, J. Organomet. Chem. 2003, 673, 25–39;
d) T. Takeda, A. G. Fix, M. M. Haley, Org. Lett. 2010, 12, 3824–
3827.
[3] J. Zhang, D. J. Pesak, J. L. Ludwick, J. S. Moore, J. Am. Chem. Soc.
1994, 116, 4227–4239.
[4] C. Grave, A. D. Schlꢁter, Eur. J. Org. Chem. 2002, 3075–3098.
[5] a) M. E. Gallina, C. Giansante, P. Ceroni, M. Venturi, J. Sakamoto,
A. D. Schlꢁter, Eur. J. Inorg. Chem. 2011, 1479–1486; b) K. Becker,
P. G. Lagoudakis, G. Gaefke, S. Hçger, J. M. Lupton, Angew. Chem.
2007, 119, 3520–3525; Angew. Chem. Int. Ed. 2007, 46, 3450–3455;
c) A. D. Slepkov, F. A. Hegmann, R. R. Tykwinski, K. Kamada, K.
Ohta, J. A. Marsden, E. L. Spitler, J. J. Miller, M. M. Haley, Opt.
Lett. 2006, 31, 3315–3317; d) K. Ohta, S. Yamada, K. Kamada,
A. D. Slepkov, F. A. Hegmann, R. R. Tykwinski, L. D. Shirtcliff,
M. M. Haley, P. Salek, F. Gel’mukhanov, H. Agren, J. Phys. Chem.
A 2011, 115, 105–117; e) E. L. Spitler, J. M. Monson, M. M. Haley,
J. Org. Chem. 2008, 73, 2211–2223; f) A. Sarkar, J. J. Pak, G. W.
Rayfield, M. M. Haley, J. Mater. Chem. 2001, 11, 2943–2945; g) T.
Naddo, Y. Che, W. Zhang, K. Balakrishnan, X. Yang, M. Yen, J.
[12] a) S. H. Jung, W. Pisula, A. Rouhanipour, H. J. Rꢂder, J. Jacob, K.
Mꢁllen, Angew. Chem. 2006, 118, 4801–4806; Angew. Chem. Int.
Ed. 2006, 45, 4685–4690; b) S. Hçger, A. D. Meckenstock, H.
Chem. Eur. J. 2013, 19, 4480 – 4495
ꢃ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
4493

S. Fçrster, S. Hçger et al.
Pellen, J. Org. Chem. 1997, 62, 4556–4557; c) A. Ziegler, W. Mam-
douh, A. Ver Heyen, M. Surin, H. Uji, M. M. S. Abdel-Mottaleb,
F. C. De Schryver, S. De Feyter, R. Lazzaroni, S. Hçger, Chem.
Mater. 2005, 17, 5670–5683.
[29] The deprotonation of 3,5-dichloranisole in THF at À788C with
tBuLi (1.2 equiv) followed by the addition of iodine in THF led to a
product mixture of unreacted 3,5-dichloroanisole (34%), 3,5-di-
chloro-2-iodoanisole (38%), and 3,5-dichloro-2,6-diiodoanisole
(21%) along with some unknown side products (7%). These ratios
were determined by GC-MS.
[30] a) M. Iwao, J. Org. Chem. 1990, 55, 3622–3627; b) F. Toudic, A.
Turck, N. Ple, G. Queguiner, M. Darabantu, T. Lequeux, J. C. Pom-
melet, J. Heterocycl. Chem. 2003, 40, 855–860.
[31] a) M. J. Plater, J. P. Sinclair, S. Aiken, T. Gelbrich, M. B. Hursthouse,
Tetrahedron 2004, 60, 6385–6394; b) W. A. Daoud, M. L. Turner,
Bull. Chem. Soc. Jpn. 2005, 78, 367–369; c) N. Gonzꢈlez-Rojano, E.
Arias-Marꢉn, D. Navarro-Rodrꢉguez, S. Weidner, Synlett 2005, 1259–
1262; d) C. S. Andersen, K. V. Gothelf, Org. Biomol. Chem. 2009, 7,
58–60; e) J.-F. Morin, T. Sasaki, Y. Shirai, J. M. Guerrero, J. M.
Tour, J. Org. Chem. 2007, 72, 9481–9490; f) K. Kobayashi, N. Ko-
bayashi, M. Ikuta, B. Therrien, S. Sakamoto, K. Yamaguchi, J. Org.
Chem. 2005, 70, 749–752.
[32] R. Chinchilla, C. Nꢈjera, Chem. Soc. Rev. 2011, 40, 5084–5121.
[33] Partially deprotected 7a was isolated in a yield of 20%.
[34] T. Hundertmark, A. F. Littke, S. L. Buchwald, G. C. Fu, Org. Lett.
2000, 2, 1729–1731.
[35] The system was reported without DBU and with dioxane as solvent
and diisopropyl amine as base. Heating was not required and reac-
tion times were between 0.5 and 15 h. In the present case, this
system did not give any product, even at 808C (conventional heat-
ing) or after 12 min of microwave irradiation at 1208C. Only the
starting material was observed by TLC.
[36] A. Soheili, J. Albaneze-Walker, J. A. Murry, P. G. Dormer, D. L.
Hughes, Org. Lett. 2003, 5, 4191–4194.
[37] a) C. Oliver Kappe, Chem. Soc. Rev. 2008, 37, 1127–1139; b) V. P.
Mehta, E. V. Van der Eycken, Chem. Soc. Rev. 2011, 40, 4925–4936.
[38] a) G. Gaefke, S. Hçger, Synthesis 2008, 2155–2157; b) S. Hçger, K.
Bonrad, J. Org. Chem. 2000, 65, 2243–2245.
[13] a) S. Anderson, H. L. Anderson, J. K. M. Sanders, Acc. Chem. Res.
1993, 26, 469–475; b) D. H. Busch, Top. Curr. Chem. Vol. 249 (Eds.:
C. A. Schalley, F. Vçgtle, K. H. Dçtz), Springer Berlin/Heidelberg,
2005, 1–65; c) Z. R. Laughrey, B. C. Gibb, Top. Curr. Chem. Vol.
249 (Eds.: C. A. Schalley, F. Vçgtle, K. H. Dçtz), Springer Berlin/
Heidelberg, 2005, 67–125; d) J. K. Sprafke, D. V. Kondratuk, M.
Wykes, A. L. Thompson, M. Hoffmann, R. Drevinskas, W.-H. Chen,
C. K. Yong, J. Kꢂrnbratt, J. E. Bullock, M. Malfois, M. R. Wasielew-
ski, B. Albinsson, L. M. Herz, D. Zigmantas, D. Beljonne, H. L. An-
derson, J. Am. Chem. Soc. 2011, 133, 17262–17273; e) M. C. OꢄSulli-
van, J. K. Sprafke, D. V. Kondratuk, C. Rinfray, T. D. W. Claridge,
A. Saywell, M. O. Blunt, J. N. OꢄShea, P. H. Beton, M. Malfois, H. L.
Anderson, Nature 2011, 469, 72–75.
[14] S. Hçger, V. Enkelmann, Angew. Chem. 1996, 107, 2917–2919;
Angew. Chem. Int. Ed. Engl. 1995, 34, 2713–2716.
[15] a) U. H. F. Bunz, Chem. Rev. 2000, 100, 1605–1644; b) P. M. Cotts,
T. M. Swager, Q. Zhou, Macromolecules 1996, 29, 7323–7328; c) A.
Godt, M. Schulte, H. Zimmermann, G. Jeschke, Angew. Chem. 2006,
118, 7722–7726; Angew. Chem. Int. Ed. 2006, 45, 7560–7564.
[16] Acyclic alternating rigid rod/corner copolymers behave as freely ro-
tating chains (in which the degrees of freedom of the corner seg-
ments are restricted to rotational motion of the rod units). Note:
Freely jointed chains consist of rigid rod units that are connected by
flexible linker units. On the contrary, in freely rotating chains the
rigid rods are linked by corner units that allow a rotation.
[17] a) C. Grave, A. D. Schlꢁter, Eur. J. Org. Chem. 2002, 3075–3098;
b) M. Xanthos, Functional Fillers for Plastics, VCH, Weinheim,
2005.
[18] M. Albrecht, Yeni, R. Frçhlich, Synlett 2007, 2295–2297.
[19] a) W. B. Smith, O. C. Ho, J. Org. Chem. 1990, 55, 2543–2545; b) L.
Malet-Sanz, J. Madrzak, R. S. Holvey, T. Underwood, Tetrahedron
Lett. 2009, 50, 7263–7267.
[39] Most likely the lower yield of the cyclization of 12b can be ascribed
to the smaller scale on which the reaction was performed (relative
to 12a).
[20] a) C. J. F. Du, H. Hart, K. K. D. Ng, J. Org. Chem. 1986, 51, 3162–
3165; b) A. Saednya, H. Hart, Synthesis 1996, 1455.
[40] For the addition all at once (0 h; within 1 min), the concentration of
12a in the receiver is calculated directly by dividing the amount of
12a in the syringe by the total volume. All other concentrations
were calculated by assuming a drop size of 0.05 mL of the solution
of 12a in THF. The average concentration of 12a in the receiver,
after addition of a drop, was calculated according to the following
[21] Direct conversion of 5a to 7a fails due to a strong ortho-directing
effect of the methoxy substituent. While Hart et al. were able to
obtain the terphenyl directly from 1,3-dichlorobenzene and the lith-
iumorganyl, the reaction of 5a with 4-[2-(triisopropylsilyl)ethynyl]-
phenyl lithium (formed from 1-bromo-4-(triisopropylsilylethynyl)-
benzene and tBuLi) leads to 5-chloro-2-iodo-3-methoxy-4’-[2-(triiso-
propylsilyl)ethynyl]biphenyl; a) S. Hçger, Liebigs Ann. Recl. 1997,
273–277; b) N. J. R. van Eikema Hommes, P. von Raguꢀ Schleyer,
Angew. Chem. 1992, 104, 768–771; Angew. Chem. Int. Ed. Engl.
1992, 31, 755–758; c) F. M. Irvine, J. C. Smith, J. Chem. Soc. 1927,
74–77.
equation: c(12a in receiver)=[c(12a in syringe)ꢅ0.05 mLVÀ1
(receiver)+c(12a in syringe)ꢅ0.05 mL/[V(receiver)+V(syringe)]]/2
-
A
R
ACHTUNGTRENNUNG
(=average concentration of 12a in the receiver, by considering the
first and the last drop that is added). We assume in this calculation
that all bisacetylene of one drop is completely coupled before the
next drop reaches the solution.
[41] Assuming the dimer to have an extinction coefficient that is twice as
large as for the monomer, the amount of dimer was reduced from
approximately 3% to approximately 1%.
[42] D. Mçssinger, S.-S. Jester, E. Sigmund, U. Mꢁller, S. Hçger, Macro-
molecules 2009, 42, 7974–7978.
[43] a) A. M. Boldi, F. Diederich, Angew. Chem. 1994, 106, 482–485;
Angew. Chem. Int. Ed. Engl. 1994, 33, 468–471; b) Y. Pang, J. Li, B.
Hu, F. E. Karasz, Macromolecules 1999, 32, 3946–3950; c) L. Liao,
Y. Pang, L. M. Ding, F. E. Karasz, J. Polym. Sci. Part A 2003, 41,
3149–3158; d) S. Amiri, P. R. Schreiner, J. Phys. Chem. A 2009, 113,
11750–11757.
[44] Since absorption and emission of MSW-3a and MSW-3b are nearly
identical (see the Supporting Information), we currently do not be-
lieve that the formation of hydrogen aggregates can be responsible
for alterations of such a large extent.
[22] Iodination with N-iodosuccinimide (NIS) (product ratio: 3:1, overall
yield <50%), iodic acid, and iodine (product ratio 1:1), and bis(tert-
butylcarbonyloxy)iodobenzene or bisACTHUNTGRNEUNG(acetoxy)iodobenzene (no re-
action) were inferior. A more regioselective iodination method that
gave a ratio of 16:1 was reported after completion of this work by
Lehmler et al.: S. N. Joshi, S. M. Vyas, H. Wu, M. W. Duffel, S.
Parkin, H.-J. Lehmler, Tetrahedron 2011, 67, 7461–7469.
[23] A. Godt, O. ꢇnsal, M. Roos, J. Org. Chem. 2000, 65, 2837–2842.
[24] This was ascribed to an artificially increased ratio between the lithi-
um organyl and 6a (as opposed to adding 6a all at once).
[25] H. Hart, K. Harada, C. J. F. Du, J. Org. Chem. 1985, 50, 3104–3110.
[26] C. Elschenbroich, Organometallchemie, 5th ed., Teubner, Wiesba-
den, 2 005.
[27] Starting with commercially available compounds, the Suzuki cou-
pling affords a five-step synthesis, whereas the Hart reaction re-
quires only three. This includes the preparation of the lithiated com-
pound for the latter and the preparation of the boronic ester for the
former reaction.
[45] S. Hçger, Pure Appl. Chem. 2010, 82, 821–830.
[46] The voids of the larger MSW-1 and MSW-2a/b offered more room
to accommodate larger parts of their alkyl chains. Furthermore, the
peripheral alkyl chains adsorbed well on HOPG, thereby resulting
in highly attractive alkyl–graphite interactions. Thus those com-
[28] J. L. Holcombe, T. Livinghouse, J. Org. Chem. 1986, 51, 111–113.
4494
www.chemeurj.org
ꢃ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2013, 19, 4480 – 4495

Molecular Spoked Wheels
FULL PAPER
pounds could be visualized well by STM (ref. [10b]; K. Tahara, S.
Lei, D. Mçssinger, H. Kozuma, K. Inukai, M. Van der Auweraer,
F. C. De Schryver, S. Hçger, Y. Tobe, S. De Feyter, Chem. Commun.
2008, 3897–3899; D. Mçssinger, D. Chaudhuri, T. Kudernac, S. Lei,
S. De Feyter, J. M. Lupton, S. Hçger, J. Am. Chem. Soc. 2010, 132,
1410–1423). Such forces are missing in MSW 3a/b.
Lindsay, D. A. Weitz, R. C. Ball, R. Klein, P. Meakin, Nature 1989,
339, 360–362.
[50] M. M. J. Smulders, M. M. L. Nieuwenhuizen, T. F. A. de Greef, P.
van der Schoot, A. P. H. J. Schenning, E. W. Meijer, Chem. Eur. J.
2010, 16, 362–367.
[51] If desired, the corresponding phenol can be obtained by acid-pro-
moted cleavage of the oxygen–carbon bond.
[52] S. Fçrster, L. Apostol, W. Bras, J. Appl. Crystallogr. 2010, 43, 639–
646.
[47] W. Schꢂrtl, Light scattering from polymer solutions and nanoparticle
dispersions, Springer, Berlin/Heidelberg, 2007.
[48] a) S. W. Provencher, Comput. Phys. Commun. 1982, 27, 213–227;
b) S. W. Provencher, Comput. Phys. Commun. 1982, 27, 229–242.
[49] a) V. Privman, D. V. Goia, J. Park, E. Matijevic, J. Colloid Interface
Sci. 1999, 213, 36–45; b) M. Y. Lin, H. M. Lindsay, D. A. Weitz, R.
Klein, R. C. Ball, P. Meakin, J. Phys. Condens. Matter 1990, 2, 3093–
3113; c) M. Y. Lin, H. M. Lindsay, D. A. Weitz, R. C. Ball, R. Klein,
P. Meakin, Phys. Rev. A 1990, 41, 2005–2020; d) M. Y. Lin, H. M.
[53] S. Fçrster, S. Fischer, K. Zielske, C. Schellbach, M. Sztucki, P. Lind-
ner, J. Perlich, Adv. Colloid Interface Sci. 2011, 163, 53–83.
Received: September 26, 2012
Published online: February 18, 2013
Chem. Eur. J. 2013, 19, 4480 – 4495
ꢃ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
4495