Communication
ChemComm
quality of the supramolecular template is not affected by the Notes and references
adsorption of the star molecule. The Fourier filtered image (inset,
1 J. Elemans, S. B. Lei and S. De Feyter, Angew. Chem., Int. Ed., 2009,
48, 7298–7332; A. G. Slater, P. H. Beton and N. R. Champness, Chem.
Sci., 2011, 2, 1440–1448; L. Bartels, Nat. Chem., 2010, 2, 87–95;
J. V. Barth, Annu. Rev. Phys. Chem., 2007, 58, 375–407; T. R. Eaton,
D. M. Torres, M. Buck and M. Mayor, Chimia, 2013, 67, 222–226.
2 S. Stepanow, M. Lingenfelder, A. Dmitriev, H. Spillmann,
E. Delvigne, N. Lin, X. B. Deng, C. Z. Cai, J. V. Barth and K. Kern,
bottom right) yields a spot in the centre of the pore surrounded by a
sixfold pattern which is aligned with the melamine vertices of the
network. This pattern reflects the statistical occupation of the two
positions schematically shown in Fig. 1a which are energetically
equivalent due to the symmetry of the system.
ˇ
Nat. Mater., 2004, 3, 229–233; J. Cechal, C. S. Kley, T. Kumagai,
A close look at the high resolution images like the one depicted
in Fig. 3b, reveals additional features. Besides the dominating
adsorption geometry where the molecule retains it symmetric star
shape and all three arms point towards the melamine vertices
(e.g. pore 1), the geometry of the POH-TPEB molecule is distorted
in some of the pores with one arm pointing towards a PTCDI unit of
the network (pore 2). In all these cases there is a pronounced
additional protrusion which, based on the shape and imaging
contrast, is reasonable to assume to be a PTCDI molecule. While
a compartment defined by an undistorted star molecule is too small
to accommodate a PTCDI molecule, widening the angle between
two arms by deformation of the ethynylene units allows the PTCDI
to fit in as illustrated in the model of Fig. 3c. In this context it is
worth noting that for a network such as the one shown in Fig. 3b
which exhibits a high structural perfection we do not observe PTCDI
molecules trapped in the pores prior to the adsorption of the star
molecules. However, in the STM images the appearance of the pores
can vary to some extent. For a small fraction the measured height
difference between the PTCDI molecules of the network and the
pore area is different from the other pores or streaky features are
observed such as the one seen in the bottom of the STM image of
Fig. 1a. This suggests that residual PTCDI molecules are present in
some pores after the network preparation which, however, are too
mobile to be resolved by STM. Their presence is only revealed after
being locked into place by the adsorption of a star molecule.
The experiments described above identify a strategy and the
conditions for an iterative approach to ultraprecise two dimen-
sional structures. A primary template generated by bottom-up
self-assembly defines the positioning of another molecular
entity which further reduces dimensions through partitioning
of a pore. To achieve high yield and well defined compartmen-
tation the molecule must fully fit into the pore.
F. Schramm, M. Ruben, S. Stepanow and K. Kern, J. Phys. Chem. C,
2013, 117, 8871–8877.
3 A. Langner, S. L. Tait, N. Lin, C. Rajadurai, M. Ruben and K. Kern,
Proc. Natl. Acad. Sci. U. S. A., 2007, 104, 17927–17930; P. A. Staniec,
˜
L. M. A. Perdigao, A. Saywell, N. R. Champness and P. H. Beton,
ChemPhysChem, 2007, 8, 2177–2181; K. Tahara, K. Inukai,
J. Adisoejoso, H. Yamaga, T. Balandina, M. O. Blunt, S. De Feyter
and Y. Tobe, Angew. Chem., Int. Ed., 2013, 52, 8373–8376; Y. B. Li,
Z. Ma, K. Deng, S. B. Lei, Q. D. Zeng, X. L. Fan, S. De Feyter,
W. Huang and C. Wang, Chem. – Eur. J., 2009, 15, 5418–5423.
¨ ¨
4 M. T. Raisanen, A. G. Slater, N. R. Champness and M. Buck, Chem.
Sci., 2012, 3, 84–92.
5 J. Adisoejoso, K. Tahara, S. Okuhata, S. Lei, Y. Tobe and S. De Feyter,
Angew. Chem., Int. Ed., 2009, 48, 7353–7357.
¨ ¨
6 R. Madueno, M. T. Raisanen, C. Silien and M. Buck, Nature, 2008,
454, 618–621.
¨ ¨
7 C. Silien, M. T. Raisanen and M. Buck, Angew. Chem., Int. Ed., 2009,
48, 3349–3352.
¨ ¨
8 C. Silien, M. T. Raisanen and M. Buck, Small, 2010, 6, 391–394.
9 M. Stohr, M. Wahl, H. Spillmann, L. H. Gade and T. A. Jung, Small,
2007, 3, 1336–1340.
10 S. D. Ha, B. R. Kaafarani, S. Barlow, S. R. Marder and A. Kahn,
J. Phys. Chem. C, 2007, 111, 10493–10497.
11 P. Szabelski, S. De Feyter, M. Drach and S. B. Lei, Langmuir, 2010, 26,
9506–9515; P. Szabelski, W. Rzysko, T. Panczyk, E. Ghijsens,
K. Tahara, Y. Tobe and S. De Feyter, RSC Adv., 2013, 3,
25159–25165; Z. Mu, L. Shu, H. Fuchs, M. Mayor and L. Chi,
J. Am. Chem. Soc., 2008, 130, 10840–10841.
12 J. A. Theobald, N. S. Oxtoby, M. A. Phillips, N. R. Champness and
P. H. Beton, Nature, 2003, 424, 1029–1031.
13 F. Silly, A. Q. Shaw, G. A. D. Briggs and M. R. Castell, Appl. Phys. Lett.,
2008, 92, 023102.
¨ ¨
14 I. Cebula, M. T. Raisanen, R. Madueno, B. Karamzadeh and
M. Buck, Phys. Chem. Chem. Phys., 2013, 15, 14126–14127.
15 V. V. Korolkov, N. Mullin, S. Allen, C. J. Roberts, J. K. Hobbs and
S. J. B. Tendler, Phys. Chem. Chem. Phys., 2012, 14, 15909–15916.
16 T. Takeda and Y. Tobe, Chem. Commun., 2012, 48, 7841–7843; S. Toyota,
T. Yamamori and T. Makino, Tetrahedron, 2001, 57, 3521–3528; G. Jeschke,
M. Sajid, M. Schulte, N. Ramezanian, A. Volkov, H. Zimmermann and
A. Godt, J. Am. Chem. Soc., 2010, 132, 10107–10117.
´
¨
17 D. Heim, D. Ecija, K. Seufert, W. Auwarter, C. Aurisicchio, C. Fabbro,
D. Bonifazi and J. V. Barth, J. Am. Chem. Soc., 2010, 132, 6783–6790;
Compared to a similar approach taken in a UHV experiment25
where partitioning of pores is accomplished by three non-covalently
interacting molecules, the strategy presented here using a single
molecule provides higher flexibility in the design. Notably, going
beyond the simple threefold symmetry of the star molecule by
modifying the geometry and/or introducing functionality and/or
chirality to subpores, which can be envisaged to be different for
each one, a new level of control at this small length scale opens up.
Furthermore, partitioning by a purely covalent structure is also
beneficial for the stability of the systems required in subsequent
steps of a hierarchical assembly process.
This work was supported in part by The Leverhulme Trust.
The synthetic team at the University of Basel acknowledges
financial support by the Swiss National Science Foundation
(SNF) and the Swiss Nanoscience Institute (SNI). BK is grateful
to EaStCHEM and the Funds for Women Graduates (FfWG) for
postgraduate studentships.
¨
D. Ecija, S. Vijayaraghavan, W. Auwarter, S. Joshi, K. Seufert, C. Aurisicchio,
D. Bonifazi and J. V. Barth, ACS Nano, 2012, 6, 4258–4265.
18 N. M. Jenny, M. Mayor and T. R. Eaton, Eur. J. Org. Chem., 2011,
4965–4983.
19 E. A. Krasnokutskaya, N. I. Semenischeva, V. D. Filimonov and
P. Knochel, Synthesis, 2007, 81–84.
¨
20 U. Harten, A. M. Lahee, J. P. Toennies and C. Woll, Phys. Rev. Lett.,
1985, 54, 2619–2622; A. R. Sandy, S. G. J. Mochrie, D. M. Zehner,
K. G. Huang and D. Gibbs, Phys. Rev. B, 1991, 43, 4667–4687.
21 C. Woll, S. Chiang, R. J. Wilson and P. H. Lippel, Phys. Rev. B, 1989,
¨
39, 7988–7991.
22 F. Rossel, P. Brodard, F. Patthey, N. V. Richardson and W.-D.
Schneider, Surf. Sci., 2008, 602, L115–L117.
23 J. T. Sun, L. Gao, X. B. He, Z. H. Cheng, Z. T. Deng, X. Lin, H. Hu,
S. X. Du, F. Liu and H. J. Gao, Phys. Rev. B, 2011, 83, 115419.
24 C. B. France, P. G. Schroeder, J. C. Forsythe and B. A. Parkinson,
Langmuir, 2003, 19, 1274–1281; F. Silly, A. Q. Shaw, M. R. Castell and
G. A. D. Briggs, Chem. Commun., 2008, 1907–1909; Y. Y. Lo,
J. H. Chang, G. Hoffmann, W. B. Su, C. I. Wu and C. S. Chang,
Jpn. J. Appl. Phys., 2013, 52, 101601–101606.
25 D. Ku¨hne, F. Klappenberger, W. Krenner, S. Klyatskaya, M. Ruben
and J. V. Barth, Proc. Natl. Acad. Sci. U. S. A., 2010, 107, 21332–21336.
14178 | Chem. Commun., 2014, 50, 14175--14178
This journal is ©The Royal Society of Chemistry 2014