Controlling the macroscopic chirality of organic materials based on 1,3,5-trialkynylbenzenes

Article abstract of DOI:10.1002/ejoc.201101636

By changing the position of the homochiral alkoxy substituents of C ₃-symmetric 1,3,5-trialkynylbenzenes from the center to the periphery, the macroscopic chirality of the resulting aggregates (crystals or fibers), studied by various spectrosco

Full text of DOI:10.1002/ejoc.201101636

FULL PAPER
DOI: 10.1002/ejoc.201101636
Controlling the Macroscopic Chirality of Organic Materials Based on
1,3,5-Trialkynylbenzenes
Gunther Hennrich,*[a] Belén Nieto-Ortega,[b] Berta Gómez-Lor,[c] Entique Gutierrez,[c]
Laura de Vega,[a] Emma Cavero,[c] Francisco J. Ramírez,[b] Juan T. López Navarrete,*[b] and
Juan Casado[b]
Dedicated to Dr. Helmut Sonnenschein on the occasion of his 60th birthday
Keywords: Chirality / Self-assembly / Crystal engineering / Cross-coupling / Spectroscopic methods
By changing the position of the homochiral alkoxy substitu-
ents of C3-symmetric 1,3,5-trialkynylbenzenes from the cen-
ter to the periphery, the macroscopic chirality of the resulting
aggregates (crystals or fibers), studied by various spectro-
scopic and microscopic techniques, was inverted, as con-
firmed by single-crystal X-ray diffraction analysis.
molecular-weight organic compounds, the crystallographic
analysis of supramolecular systems has proved extremely
useful for revealing the factors responsible for the high de-
gree of supramolecular order.[5] Macroscopic chirality is of
crucial importance for the application of organic materials
to the fields of nonlinear optics,[6] photonics,[7] electronics,[8]
and display technology.[9]
Introduction
In this work, we aimed to deliberately prepare supra-
molecular materials with chiral order on the macroscopic
level by employing 1,3,5-trialkoxybenzenes (TABs) as mo-
lecular modules bearing homochiral alkoxy substituents to
impart chiral information to the bulk aggregate. In recent
years an enormous amount of research has been dedicated
to the design of chiral molecular materials.[1] The controlled
arrangement of molecular units must conserve the function-
ality in the bulk that each single molecule is endowed with.
In the optimum case, the utility pre-programmed on the
molecular level can be enhanced in the macroscopic as-
sembly, and even completely new benefits may arise in the
bulk material as a result of the macroscopic order.[2] Al-
though common supramolecular weak interactions such as
dipole–dipole, hydrogen-bonding, and π-stacking are also
operative in the crystal,[3] the packing of the individual mo-
lecular units is an additional parameter of vital importance
in the design of crystalline materials.[4] In the case of low-
A recent review by Gibson and Castaldi covers the latest
advances in chiral C3-symmetric molecules.[10] Far more
than just being aesthetically appealing, these kinds of com-
pounds have found numerous applications in the fields of
supramolecular chemistry (chiral receptors), asymmetric
catalysis (chiral ligands), materials chemistry (chiral self-as-
sembled systems), and others. The rational design of chiral
organic materials is conveniently achieved either by using
inherently chiral scaffolds[11] or by introducing homochiral
substituents into achiral molecules.[12] In the absence of fur-
ther symmetry elements such as rotation axes or symmetry
planes, these substituents determine the chiral nature of the
resulting molecule. For disc-shaped structures, aromatic π–
π interactions and van der Waals forces between lateral
alkyl chains promote the stacking of discrete molecules into
[a] Departamento de Química Orgánica, Universidad Autónoma columnar piles.[13] By using homochiral building blocks, the
de Madrid,
supramolecular chirality is expressed in helical super-struc-
Cantoblanco, 28049 Madrid, Spain
tures.[14] The formation of fibrous aggregates or helical co-
Fax: +34-91-497-2775
E-mail: gunther.hennrich@uam.es
lumnar stacks from homochiral subunits is conveniently
visualized by using different microscopic techniques.[15] The
discotic TAB molecule is an ideal platform for the construc-
tion of simple electro-optical devices,[16] and the formation
of columnar stacks in the liquid-crystalline state has been
reported.[17]
[b] Departmento de Química Física, Universidad de Málaga,
29071 Málaga, Spain
E-mail: teodomiro@uma.es
[c] Instituto de Ciencia de Materiales, CSIC,
Cantoblanco, 28049 Madrid, Spain
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201101636.
Eur. J. Org. Chem. 2012, 1577–1582
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1577

G. Hennrich, J. T. López Navarrete et al.
FULL PAPER
vary slightly in the orientation of the central methoxy and
peripheral butoxy chains. Note that owing to the exception-
ally high resolution of the detection system, small variations
in the highly flexible substituents, which are commonly re-
ferred to as crystallographic disorder, could be unequivo-
cally assigned. Figure 1 shows the expanded, almost per-
fectly planar, molecular structure of 1 with the peripheral
phenyl rings slightly twisted out of the molecular plane. The
molecules are arranged in 2D layers, intercalated with the
peripheral phenylacetylene groups and their lateral alkyl
chains. The stabilization of the layers is attributed to several
short C=O···CH contacts of ca. 2.5 Å. These layers stack
along the [110] direction to form a chiral 3D crystal. In
addition to the disposition of the methylbutyl stereocenters
in the crystal, the relative configuration of the methoxy
groups around the central benzene core is worthwhile not-
ing as this may additionally contribute to the macroscopic
chirality of the crystal.
Concurring with the tendency observed for the crystal-
line state, long fibers were grown by preparing an over-satu-
rated, hot solution of compound 1 in decane (c =
0.093 molL–1), which was subsequently allowed to cool to
room temperature. In analogy, Meijer and co-workers had
reported the formation of macroscopic fibers consisting of
columnar stacks from discotic benzene derivatives.[20] In
this work, fibers were grown by slow cooling of a hot satu-
rated solution of 1 in decane. Scanning electron microscopy
shows bundles of hollow, tubular fibers (“rolled sheets“)
with lengths of various tens of micrometers and roughly 1–
2 μm in diameter (Figure 2).
Results and Discussion
In this report two different persubstituted TABs are pre-
sented. The chiral order in the crystalline and bulk phase
has been studied by various spectroscopic techniques such
as single-crystal X-ray diffraction, Raman and IR spec-
troscopy, and vibrational and electronic circular dichroism.
In addition, scanning electron microscopy (SEM) was used
to elucidate the structural features of the fibers formed in
decane solution. The relevant structural differences between
the two compounds are the positions of the homochiral
substituents in the molecular scaffold, either on the central
benzene core or on the periphery of the ethynylbenzene
substituents. Structural modification at the molecular level
enables the design of supramolecular materials with distinct
helical macrostructures, and thus control of the chirality of
the organic bulk material.
Target molecules 1 and 2 were obtained in a modular
approach by following an established synthetic pro-
cedure.[18] First, nucleophilic aromatic substitution yielded
the triiodobenzenes 1a and 2a from commercially available
1,3,5-trifluoro-2,4,6-triiodobenzene. In a second step, those
triiodobenzenes were subjected to a three-fold Sonogashira
coupling procedure with the corresponding 4-ethynylbenzo-
ates (Scheme 1).[19]
C3-Symmetric, highly conjugated π-systems were ob-
tained with electronically matching donor and acceptor
substitution at the central benzene core and the phenyleth-
ynyl periphery, respectively. This substitution pattern, that
is, the resulting electronic distribution, promotes the intra-
molecular stacking interactions and directs the supramolec-
ular order in the bulk.
The growth process was also monitored by IR spec-
troscopy. The variation of the benzene vibrations at ca.
Long needles of 1, suitable for single-crystal X-ray dif- 1600 cm–1 and, more significantly, the C=O stretching vi-
fraction, were grown by slow evaporation of dichlorometh- brations are the most characteristic features. The slow ap-
ane. The molecule crystallizes in a chiral (triclinic P1) space pearance of a band at 1714 cm–1 (fiber) at the expense of
group. For the refined structure, a Flack factor of 0.0(2) the initial vibration at 1728 cm–1 (nonaggregated 1) evi-
indicates the presence of a single enantiomer. The unit cell dences the participation of these moieties in the formation
is formed of six crystallographically different molecules that of aggregates (Figure S2).
Scheme 1. Stepwise preparation of homochiral TABs 1 and 2: Nucleophilic aromatic substitution followed by three-fold Sonogashira
cross-coupling.
1578
www.eurjoc.org
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2012, 1577–1582

Controlling the Macroscopic Chirality of Organic Materials
Figure 1. Chiral crystal of 1; crystal system: triclinic, space group: P1. View of the 2D layers, highlighting the short C=O···CH contacts.
Figure 2. SEM images of 1 at 1000ϫ (left), 1700ϫ (center), and 8000ϫ (right) magnification.
Different spectroscopic techniques were employed to
shed further light on the findings obtained from the crystal-
line and solid materials obtained. The UV/Vis and CD
spectra of molecules 1 and 2 as solid samples were recorded
by dispersing an identical amount of the two samples
(0.6 mg) in the same amount (0.6 mg) of a solid KBr ma-
trix. Under these conditions aggregation is forced, driven
by intermolecular π–π and van der Waals interactions, and
the absorption bands associated with π–π* electronic transi-
tions confirm this (Figure 3).
The UV/Vis spectra of the two molecules exhibit broad
absorptions of similar energy between 300 and 400 nm that
arise from π–π* transitions. In contrast, the CD spectra of
1 and 2 show different dichroic signals associated with these
π–π* bands. The bisignate character is indicative of exciton
coupling and a Cotton effect between coupled chiral chro-
mophores. The magnitude of the Cotton effect can be
evaluated by the energy difference between the negative and
positive peaks of the bisignate mode (W), which provides a
sensitive measure of the intermolecular coupling. The W
Figure 3. Electronic absorption and CD spectra of 1 (black line)
and 2 (grey line) from solid samples dispersed in KBr.
values for 1 and 2 are 0.52 and 0.51 eV, respectively, which and +/– for 2. The different macroscopic structures result
is indicative of large π-stacking coupling in both molecular from the positioning of the chiral butoxy substituents with
aggregates. The most significant features of the CD spectra the same chiral sense (S) either at the core or at the periph-
of 1 and 2 are the mirror-image bisignate bands: –/+ for 1 ery. The pattern of the bisignate signal is determined by
Eur. J. Org. Chem. 2012, 1577–1582
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
1579

G. Hennrich, J. T. López Navarrete et al.
FULL PAPER
the handedness of the supramolecular chirality and by the
spatial symmetry operations of the crystal structure, that
is, the screw axes and the glide planes. Thus, the charge
distribution of the π–π* transition within the two different
supramolecular aggregates are opposite (left- or right-
handed) and therefore give opposite CD responses.
To connect the features of the chiral super-structure with
its associated electronic structure, we calculated the CD
spectra of a supramolecular model of 1 by TDDFT (see
the Supporting Information). Comparison of the calculated
UV/Vis and CD spectra shows that the spectral pattern is
reliably predicted and that the W parameter of 0.15 eV is
clearly underestimated in the model. This can reasonably
be assumed to be due to the reduced number of units in the
interaction, although it highlights the fact that only three
molecules account for a third of the total W. The most re-
cent results reaffirm the reliability of this theoretical ap-
proach.[21]
The formation of chiral aggregates with opposite hand-
edness from 1 and 2 has also been studied by vibrational
circular dichroism (VCD; Figure 4). Considering the group
character of specific active vibrations, VCD spectroscopy
can delineate the specific interactions that promote the for-
mation of chiral supramolecular aggregates. Therefore, the
observed bands have to be assigned to local vibrational
transitions, which is assisted by quantum chemical and nor-
mal mode calculations. The validity of this experimental
versus theoretical approach was initially confirmed by IR
spectroscopy (see the Supporting Information). The spec-
tral deviations of the VCD spectra of 1 and 2 can be as-
cribed to different structures of the aggregates, namely the
opposite handedness of the chiral super-structures formed
by 1 and 2. Although the observed CD signals result from
a supramolecular arrangement of the molecular units, the
VCD spectra account for both the molecular and supra-
molecular chirality.
Figure 4. VCD (top) and IR (bottom) spectra of 1 (black line) and
2 (grey line) from solid samples dispersed in KBr.
Conclusion
Chiral bulk materials have been obtained from designed
The VCD signal associated with the carbonyl stretching molecular building blocks. The C3-symmetric phenylacetyl-
is incipiently bisignate in the case of 1, whereas it appears enes are densely functionalized (persubstituted benzene
as a negative band for 2. We should take into account the core) and self-assemble into macroscopically chiral aggre-
fact that, with molecular C3 symmetry, all the vibrations of gates. A recent study attributed the formation of helical fi-
the three lateral ethynylaryl groups are actually the result bers with opposite handedness from structurally related
of one mode of symmetry A and two degenerate modes phenylacetylene amphiphiles to favorable stacking interac-
with symmetry E. Negligible differences are expected for tions between the homochiral monomers in the aggregates,
vibrations of symmetry A and E, assuming the molecules as visualized by TEM.[22] In our case, a detailed XRD study
as isolated entities. A rather different scenario is expected of 1 unequivocally revealed the nature of the supramolec-
in the solid state, because these A and E modes can produce ular chirality of the solid material. Furthermore, an exten-
chiral signals with a different helical sense in the supra- sive spectroscopic investigation of the bulk aggregates of 1
molecular structures. Differences are also observed in the and 2 completes the characterization of the organic materi-
1200–1000 cm–1 region in which several medium-to-large als and gives additional insights into the process leading to
intensity VCD features can be noted. One of these is associ- the formation of the chiral assemblies. The molecular chi-
ated with the intense IR band at 1275–1272 cm–1, which is rality, brought about by the homochiral alkoxy substituents,
clearly more intense in the VCD spectrum of 1. Its corre- is efficiently expressed in the macroscopic material. The
sponding eigenvector extracted from the theoretical IR supramolecular chirality is delicately influenced by the posi-
spectrum describes this mode as a complex vibration with tioning of the stereocenters in the highly functionalized mo-
contributions from the central and peripheral benzene moi- lecular scaffold. Most surprisingly, opposite handedness is
eties (C–C and C=O stretchings, C–H bendings) and is observed for the helical aggregates of 1 and 2 even though
therefore very sensitive to the chiral environment of the mo- the homochiral alkoxy substituents have the same chirality
lecule in the aggregate.
(S).
1580
www.eurjoc.org
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2012, 1577–1582

Controlling the Macroscopic Chirality of Organic Materials
H), 1.75–1.61 (m, 3 H), 1.37–1.27 (m, 3 H), 1.12 (d, J = 6.8 Hz, 9
H), 0.99 (t, J = 7.5 Hz, 9 H) ppm. 13C NMR (125 MHz, CDCl3):
δ = 160.4, 83.2, 78.0, 35.7, 26.2, 16.6, 11.5 ppm. MS (MALDI-
TOF): m/z = 714 [M]+. C21H33I3O3 (714.20): calcd. C 35.31, H
4.66; found C 34.82, H 4.47.
Experimental Section
General: All solvents and reagents were purchased from Aldrich
and used without further purification. Optical rotations were deter-
mined at 589 nm (sodium-D line) by using a Perkin–Elmer-341 MC
1
polarimeter. H and 13C NMR spectra were recorded with Bruker
1,3,5-Tris{[4-(methoxycarbonyl)phenyl]ethynyl}-2,4,6-tris[(S)-2-meth-
ylbutoxy]benzene (2): According to the same procedure as described
for 1 by employing triiodobenzene 2a (357 mg, 0.5 mmol) and
methyl 4-ethynylbenzoate[18] (2.25 mg, 360 mg) pure 2 was obtained
as a pale-yellow solid after column chromatography (hexane/Et2O,
AC-300 and AC-200 spectrometers in deuteriated chloroform
(deuteriation grade Ͼ99.80%) with the solvent signal serving as
internal standard. Mass spectra (MALDI, EI, FAB) were recorded
with an HP1100MSD spectrometer. Elemental analyses were per-
formed with a LECO CHNS 932 microanalyzer.
1
40:1). Yield: 85 mg, 21%. [α]2D0 = –0.4 (c = 1, CH2Cl2). H NMR
1-[(S)-2-Methylbutoxy]-4-ethynylbenzene: 1-Iodo-4-[(S)-2-methyl-
butoxy]benzene[23] (1.0 mmol, 388 mg) was heated in a pressure
tube at 80 °C with (trimethylsilyl)acetylene (2.5 mmol, 0.353 mL)
in Ar-degassed NEt3 (15 mL) in the presence of [Pd(PPh3)Cl2]
(0.063 mmol, 44 mg) and CuI (0.063 mmol, 12 mg) for 48 h. After
cooling, the reaction mixture was suspended in water (25 mL) and
extracted with EtOAc (3ϫ10 mL). The combined organic phases
were dried (MgSO4), and the solvent was evaporated to leave the
crude solid product, which was stirred with tetrabutylammonium
fluoride (392 mg, 1.5 mmol) in THF (10 mL) at room temp. for
1.5 h. The resulting mixture was suspended in water (20 mL) and
extracted with EtOAc (2ϫ10 mL). The combined organic layers
were dried (MgSO4), the solvent was evaporated, and the remaining
oil was purified by column chromatography (hexane/EtOAc, 10:1)
to leave the pure 4-ethynylbenzoate as a colorless oil. Yield:
(200 MHz, CDCl3): δ = 8.04 (d, J = 8.2 Hz, 6 H), 7.56 (d, J =
8.2 Hz, 6 H), 4.30–4.12 (m, 6 H), 2.05–1.89 (m, 3 H), 1.80–1.58 (m,
3 H), 1.44–1.28 (m, 3 H), 1.12 (d, J = 6 Hz, 9 H), 0.93 (t, J =
7.1 Hz, 9 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 166.7, 164.1,
131.2, 129.8, 129.7, 128.3, 107.5, 96.7, 84.8, 79.8, 52.5, 36.2, 26.3,
16.9, 11.7 ppm. HRMS (MALDI-TOF): calcd. for C36H63I3O3Na
318.0117; found 947.1803.
CCDC-828854 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
Supporting Information (see footnote on the first page of this arti-
cle): Full characterization of the new compounds, spectroscopic,
and crystallographic data.
167 mg, 78%. [α]2D0 = +4.0 (c = 1, CH2Cl2). H NMR (300 MHz,
1
CDCl3): δ = 7.99 (d, J = 8.3 Hz, 2 H), 7.55 (d, J = 8.4 Hz, 2 H),
4.24–4.10 (m, 2 H), 3.22 (s, 1 H), 1.91–1.80 (m, 1 H), 1.57–1.48 (m,
1 H), 1.33–1.23 (m, 1 H), 1.01 (d, J = 6.8 Hz, 3 H), 0.96 (t, J =
7.5 Hz, 3 H) ppm. 13C NMR (125 MHz, CDCl3): δ = 165.9, 132.0,
130.5, 129.4, 126.6, 83.8, 79.9, 69.7, 34.3, 26.1, 16.5, 11.2 ppm.
HRMS (EI+): calcd. for C14H16O2 216.1150; found 216.11435.
Acknowledgments
We thank the Ministerio de Educación y Ciencia (MEC), Spain
(project nos. CTQ2009-10098-BQU and CTQ2010-1883), the Com-
unidad de Madrid (project no. S2009/MAT-1656/CAM) and the
Junta de Andalucia (project no. P09-FQM-4708) for funding.
B. N. O. thanks the MEC for a personal grant (FPU-AP2009-
2797).
1,3,5-Trimethoxy-2,4,6-tris[(4-{[(S)-2-methylbutoxy]carbonyl}-
phenyl)ethynyl]benzene (1): 1,3,5-Triiodo-2,4,6-trimethoxybenzene
(1a; 273 mg, 0.5 mmol) was heated with 1-ethynyl-4-[(S)-2-meth-
ylbutoxy]benzene (486 mg, 2.25 mmol), [Pd(PPh3)2Cl2] (27 mg,
0.038 mmol), and CuI (7 mg, 0.038 mmol) in Ar-degassed triethyl-
amine (10 mL) at 70 °C for 24 h. The mixture was poured into
water (20 mL) and extracted with EtOAc (3ϫ10 mL). The com-
bined organic phases were dried (MgSO4), and the solvent was re-
moved in vacuo. From the remaining oil, pure 1 was obtained as
a pale-orange solid after column chromatography (hexane/EtOAc,
[1] a) D. B. Amabilino (Ed.), Chirality at the Nanoscale: Nanopar-
ticles, Surfaces, Materials and More, Wiley-VCH, Weinheim,
2009; b) I. Danilas, F. Riobé, F. Piron, J. Puigmartí-Luis, J. D.
Wallis, M. Linares, H. Ågren, D. Beljonne, D. A. Amabilino,
N. Avarvari, J. Am. Chem. Soc. 2011, 133, 8344–8353.
[2] D. Chakrabati, S. N. Fejer, D. J. Wales, Proc. Natl. Acad. Sci.
USA 2009, 106, 20164–20167.
[3] J. L. Atwood, J. W. Steed, Core Concepts in Supramolecular
Chemistry and Nanochemistry, Wiley, New York, 2007.
[4] M. Schwoerer, H. C. Wolf, Organic Molecular Solids, Wiley-
VCH, Weinheim, 2007.
[5] a) Z. Wang, V. Enkelmann, F. Negri, K. Müllen, Angew. Chem.
2004, 116, 2006–2009; Angew. Chem. Int. Ed. 2004, 43, 1972–
1975; b) D. L. Reger, J. Horger, M. D. Smith, G. J. Long, Chem.
Commun. 2009, 6219–6221.
[6] A. Ciesielski, C.-A. Palma, M. Bonni, P. Samori, Adv. Mater.
2010, 22, 3506–3520.
1
10:1). Yield: 204 mg, 51%. [α]2D0 = +0.6 (c = 1, CH2Cl2). H NMR
(300 MHz, CDCl3): δ = 8.05 (d, J = 8.3 Hz, 6 H), 7.61 (d, J =
8.3 Hz, 6 H), 4.23–4.12 (m, 15 H), 1.93–1.82 (m, 3 H), 1.61–1.47
(m, 3 H), 1.37–1.22 (m, 3 H), 1.03 (d, J = 6.8 Hz, 9 H), 0.97 (t, J
= 7.5 Hz, 9 H) ppm. 13C NMR (125 MHz, CDCl3): δ = 166.0,
164.1, 131.3, 130.1, 129.5, 127.8, 107.3, 97.0, 83.6, 69.8, 61.7, 34.3,
26.2, 16.5, 11.3 ppm. MS (MALDI-TOF): m/z = 810 [M]+.
C51H54O9·0.5H2O (820.0): calcd. C 74.70, H 6.76; found C 74.74,
H 6.70.
1,3,5-Triiodo-2,4,6-tris[(S)-2-methylbutoxy]benzene (2a): (–)-[So-
dium (S)-2-methylbutoxide] (5.0 mmol), prepared in situ by adding
(S)-2-methylbutanol (6.0 mmol, 652 μL) dropwise to neat NaH
(60 % suspension in mineral oil), was added to 1,3,5-triifluoro-
2,4,6-triiodobenzene (510 mg, 1.0 mmol). N,N-Dimethylimid-
azolidinone (DMI, 1 mL) was added and the mixture stirred at
room temp. overnight. The mixture was poured into water (25 mL)
and the resulting precipitate filtered and purified by column
chromatography (hexane/CH2Cl2, 40:1) to leave pure 2a as a color-
less solid. Yield: 350 mg, 49%. [α]2D0 = –0.7 (c = 1, CH2Cl2). 1H
NMR (300 MHz, CDCl3): δ = 3.86–3.71 (m, 6 H), 2.14–2.03 (m, 3
[7] a) U. Gubler, C. Bosshard, Nature Mater. 2002, 1, 209–210; b)
S. Sioncke, T. Verbiest, A. Persoons, Mater. Sci. Eng., R 2003,
42, 115–155.
[8] H. Choi, J. Kim, S. Nishimura, T. Toyooka, F. Araoka, K.
Ishikawa, J. W. Wu, H. Takezoe, Adv. Mater. 2010, 22, 2680–
2684.
[9] X. Feng, V. Marcon, W. Pisula, M. R. Hansen, J. Kirkpatrick,
F. Grozema, D. Andrienko, K. Kremer, K. Müllen, Nature Ma-
ter. 2009, 8, 421–426.
[10] S. E. Gibson, P. Castaldi, Chem. Commun. 2006, 3045–3062.
[11] a) J. C. Roberts, N. Kapernaum, Q. Song, D. Nonnenmacher,
K. Ayub, F. Giesselmann, R. P. Lemieux, J. Am. Chem. Soc.
Eur. J. Org. Chem. 2012, 1577–1582
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
1581

G. Hennrich, J. T. López Navarrete et al.
FULL PAPER
2010, 132, 364–370; b) D. Miyajima, F. Araoka, H. Takezoe, J.
Kim, K. Kato, M. Takata, T. Aida, J. Am. Chem. Soc. 2010,
132, 8530–8531.
Asselberghs, S. Foerier, K. Clays, T. Verbiest, J. L. Serrano, An-
gew. Chem. 2006, 118, 4310–4313; Angew. Chem. Int. Ed. 2006,
45, 4203–4206; c) G. Hennrich, E. Cavero, J. Barberá, B.
Gómez-Lor, R. E. Hanes, M. Talarico, A. Golemme, J. L. Ser-
rano, Chem. Mater. 2007, 19, 6068–6070.
[12] a) V. Percec, J. G. Rudick, M. Peterca, P. A. Heiney, J. Am.
Chem. Soc. 2008, 130, 7503–7508; b) T. Verbiest, S. Sioncke,
A. Persoons, L. Vyclicki, T. J. Katz, Angew. Chem. 2002, 114,
4038–4040; Angew. Chem. Int. Ed. 2002, 41, 3882–3884.
[13] a) C. Lavigueur, E. J. Foster, V. E. Williams, J. Am. Chem. Soc.
2008, 130, 11791–11800; b) S. Grimme, Angew. Chem. 2008,
120, 3478–3483; Angew. Chem. Int. Ed. 2008, 47, 3430–3434.
[14] a) M. Tanaka, T. Ikeda, J. Mack, N. Kobayashi, T. J. Haino, J.
Org. Chem. 2011, 76, 5082–5091; b) W. Lv, X. Wu, Y. Bian, J.
Jiang, X. Zhang, ChemPhysChem 2009, 10, 2725–2732; c) G. S.
Tulevski, M. L. Bushey, J. L. Kosky, S. J. T. Ruter, C. Nuckolls,
Angew. Chem. 2004, 116, 1872–1875; Angew. Chem. Int. Ed.
2004, 43, 1836–1839.
[18] G. Hennrich, I. Asselberghs, K. Clays, A. Persoons, J. Org.
Chem. 2004, 69, 5077–5081.
[19] a) C. I. Schilling, O. Plietzsch, M. Nieger, T. Muller, S. Bräse,
Eur. J. Org. Chem. 2011, 1743–1754; W. B. Austin, N. Bilow,
W. J. Kelleghan, K. S. Y. Lau, J. Org. Chem. 1981, 46, 2280–
2286.
[20] a) M. M. J. Smulders, P. J. M. Stals, T. Mes, T. F. E. Paffen,
A. P. H. J. Schenning, A. R. A. Palmans, E. W. Meijer, J. Am.
Chem. Soc. 2010, 132, 621–626; b) J. J. van Gorp, J. A. J. M.
Vekemans, E. W. Meijer, J. Am. Chem. Soc. 2002, 124, 14759–
14769.
[15] a) H. Engelkamp, S. Middelbeek, R. J. M. Nolte, Science 1999,
284, 785–788; b) M. Fischer, G. Lieser, A. Rapp, I. Schnell, W.
Mamdouh, S. de Feyter, F. C. de Schryver, S. Höger, J. Am.
[21] B. Nieto-Ortega, J. Casado Cordon, J. T. López Navarrete, G.
Hennrich, F. J. Ramirez, J. Chem. Theory Comput. 2011, 7,
3314–3322.
Chem. Soc. 2004, 126, 214–222; c) J.-B. Lin, G.-T. Wang, X.- [22] a) F. Gaecía, F. Aparicio, M. Marenchino, R. Campos-Olivas,
K. Jiang, Z.-T. Li, Tetrahedron Lett. 2010, 51, 4221–4224; d)
S. Candekin, J. W. R. Balkenende, M. M. J. Smulders, A. R. A.
Palmans, E. W. Meijer, Nature Chem. 2011, 3, 42–46.
L. Sánchez, Org. Lett. 2010, 12, 4264–4267; b) F. Aparicio, F.
García, G. Fernández, E. Matesanz, L. Sánchez, Chem. Eur. J.
2011, 17, 2769–2776.
[16] B. Traber, J. J. Wolff, F. Rominger, T. Oeser, R. Gleiter, M. Goe-
bel, R. Wortmann, Chem. Eur. J. 2004, 10, 1227–1238.
[17] a) M. L. Bushey, T.-Q. Nguyen, W. Zhang, D. Horoszewski, C.
Nuckolls, Angew. Chem. 2004, 116, 5562–5570; Angew. Chem.
Int. Ed. 2004, 43, 5446–5453; b) G. Hennrich, A. Omenat, I.
[23] L. de Vega, P. D. Ortiz, G. Hennrich, A. Omenat, R. M. Tej-
edor, J. Barberá, B. Gómez-Lor, J. L. Serrano, J. Phys. Chem.
B 2010, 114, 4811–4815.
Received: November 11, 2011
Published Online: January 26, 2012
1582
www.eurjoc.org
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2012, 1577–1582