Such behavior inspired our suggestion that the mole-
cules of 2 prefer some kind of 2-D arrangement as a result
of the specific combination of planar and bulky segments
in their structure. The bulkiness of the bicyclopentane
cages, whichspacethe phenanthrene verticesofthetriangle
2, does not allow a “full-face” π-π stacking of the
molecules.8 This prevents a columnar organization often
observed in the case of the SPMs with a fully conjugated
planar backbone.9
To harness π-π stacking, probably the most effective
intermolecular interaction that the molecules of 2 have at
disposal, they overlap at least in part so the phenanthrene
rings in the vertices of one molecule interact with those in
different molecules of 2. The mutual head-to-tail orienta-
tion of the overlapping phenanthrene units is thus similar
like that found in crystals of 9,10-phenanthrenequin-
hydrone.10 Penetration of exterior hexyl chains into the
interior cavities of the neighboring macrocycles interlocks
the partially overlapped triangles. Some examples of a
similar arrangement of SPMs in crystals have already been
given in the literature.11 In an ideal case, the molecules
might arrange in a regular hexagonal grid with a mesh size
of around 6 nm, which is depicted in Figure 2. Of course,
the real structure of the film will be much less regular than
the varnished example, but a sporadic occurrence of such
regular domains could explain the 6 nm “spots” observed
by AFM.
Figure 2. An idealized, MM2 minimization model of 2D orga-
nization of the triangular molecules of 2 by π-π stacking of
their vertices (red ball = oxygen atom; the lower molecules are
colorized light blue for clarity).
planar phenanthrene units and bulky bicyclopentane cages
in its molecular backbone. A convergent synthetic path-
way used two building blocks, 1,3-diethynylbicyclo[1.1.1]-
pentane (1) and 3,6-diiodophenanthrene 3b, for syntheses
oftwo larger precursorsthatwerefinallycoupled affording
the target macrocycle 2 in good yield. The reported synth-
esis is the very first example of an application of the
bicyclopentane motif in the construction of SPMs. Its
incorporation into the SPM’s backbone brings some new
features such as bulkiness, σ-bonding that breaks the full-
cycle conjugation, and some conformational flexibility due
to its easy longitudinal rotation. We have used some of
them to rationalize an observed tendency of 2 to form films
on various surfaces. Our results in this area are very
preliminary, and further study of these phenomena, which
will certainly cover balancing the size of exterior tentacles
and interior cavities, construction of SPMs of different
geometry, and the useof different planarbuildingblocks, is
expected.
The intermolecular attractions are however too weak to
1
be revealed in solution (concentration dependence of H
NMR shifts or UV-vis spectra), but some evidence of
them comes from MALDI-MS spectra where peaks of a
dimer (M2þHþ; 2949.6) and even a trimer (M3þHþ;
4424.2) were observed. A high conformational flexibility
of bicyclo[1.1.1]pentane cages of 2, which can almost freely
rotate around their longitudinal axes within the yet geo-
metrically well-defined SPM, can lie behind a certain
spontaneity of the film formation that results, e.g. in its
outspreading over glassware walls. The rotation could ease
a sliding of the triangular molecules over each other until
they interlock.
In conclusion, we have synthesized the shape-
persistent macrocyclic compound 2, which combines
Acknowledgment. The authors thank to Profs. J. Havel
ꢁ
(8) The role of π-π stacking interaction in the aggregation of some
phenylacetylene macrocycles was thoroughly studied by: Shetty, A. S.;
Zhang, J.; Moore, J. S. J. Am. Chem. Soc. 1996, 118, 1019. See also:
Guieu, S.; Crane, A. K.; MacLachlan, M. J. Chem. Commun. 2011, 47,
1169. Shu, L.; Muri, M.; Krupke, R.; Mayor, M. Org. Biomol. Chem.
2009, 7, 1081. Ng, M.-F.; Yang, S.-W. J. Phys. Chem. B 2007, 111, 13886.
Shu, L.; Mayor, M. Chem. Commun. 2006, 4134.
and P. Skladal (MU Brno) and S. Bakardieva (IIC Prague)
for MALDI-MS, AFM, and SEM measurements, respec-
tively. The work was supported by the Ministry of Educa-
tion, Youth and Sports of the Czech Republic (Grant Nos.
MSM0021622410 and KONTAKT ME 09114). J.K. has
greatly acknowledged the financial support from Synthon
s.r.o., CZ.
€
€
(9) Fritzsche, M.; Jester, S.-S.; Hoger, S.; Klaus, C.; Dingenouts, N.;
Linder, P.; Drechsler, M.; Rosenfeldt, S. Macromolecules 2010, 43, 8379.
Shimura, H.; Yoshio, M.; Kato, T. Org. Biomol. Chem. 2009, 7, 3205.
Seo, S. H.; Jones, T. V.; Seyler, H.; Peters, J. O.; Kim, T. H.; Chang,
J. Y.; Tew, G. N. J. Am. Chem. Soc. 2006, 128, 9264.
(10) Calderazzo, F.; Forte, C.; Marchetti, F.; Pampaloni, G.; Pier-
ettia, L. Helv. Chim. Acta 2004, 87, 781.
(11) For examples of overlapping and interlocking SPMs, see: Sha-
Supporting Information Available. Experimental pro-
cedures, NMR spectra of new compounds, MALDI-MS
and UV-vis spectra of 2, and SEM and AFM pictures of
the obtained films are given. This material is available free
€
belina, N.; Klyatskaya, S.; Enkelmann, V.; Hoger, S. C. R. Chimie 2009,
€
12, 430. Hoger, S.; Weber, J.; Leppert, A.; Enkelmann, V. Beil. J. Org.
ꢂ
€
Chem. 2008, 4, 1. Grave, C.; Lentz, D.; Schafer, A.; Samori, P.; Rabe,
€
J. P.; Franke, P.; Schluter, A. D. J. Am. Chem. Soc. 2003, 125, 6907.
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