Journal of the American Chemical Society
COMMUNICATION
’ ACKNOWLEDGMENT
This work was financially supported in part by a Grant-in-Aid
for Scientific Research on Priority Areas “Electron Transport
through a Linked Molecule in Nanoscale” and a Grant-in-Aid for
Scientific Research (S) “Single Molecule Spectroscopy Using
Probe Microscope” from the Ministry of Education, Culture,
Sports, Science, and Technology (MEXT), Japan, and in part by
the Global COE Program “Chemistry Innovation through Co-
operation of Science and Engineering”, MEXT, Japan. We
acknowledge support by the National Research Foundation of
Korea (NRF-2006-0093847 and NRF-2010-00349). We are
grateful for the computational resources of the RIKEN Inte-
grated Cluster of Clusters (RICC) supercomputer system. J.J.
kindly acknowledges the International Program Associate (IPA)
of RIKEN for financial support. We also wish to thank
David W. Chapmon for carefully reading the manuscript.
’ REFERENCES
(1) Joachim, C.; Gimzewski, J. K.; Aviram, A. Nature 2000, 408, 541.
(2) De Feyter, S.; De Schryver, F. C. Chem. Soc. Rev. 2003, 32, 139.
(3) Barth, J. V.; Costantini, G.; Kern, K. Nature 2005, 437, 671.
(4) Otero, R.; Rosei, F.; Besenbacher, F. Annu. Rev. Phys. Chem.
2006, 57, 497.
(5) Barth, J. V.; Weckesser, J.; Cai, C.; G€unter, P.; B€urgi, L.;
Jeandupeux, O.; Kern, K. Angew. Chem., Int. Ed. 2000, 39, 1230.
(6) B€ohringer, M.; Schneider, W.-D.; Berndt, R. Angew. Chem., Int.
Ed. 2000, 39, 792.
Figure 4. Electron densities of (a) “A” and (b) “B”. The red and yellow
arrows indicate hydrogen-bonding and vdW interactions, respectively.
The contours are drawn at logarithmic intervals of 1.0 ꢁ 101/5 e/bohr3.
adsorption site, such as a phenyl ring on a hollow site. However,
when the next molecule is added, the intermolecular interac-
tions become dominant, and with every additional molecule
added, the molecule strays a little farther from the original
adsorption site. Thus, individual molecules in the MZ may not
be fully aligned with the substrate, even though the MZ is
properly aligned with the high-symmetry directions of the
substrate. Therefore, it is our observation in this work that
the MZ can be fabricated on various solid substrates that have
only weak interactions with adsorbates.19
In summary, we have presented the formation of MZs of
azobenzene derivatives as studied by STM observation and DFT
calculations. Formation of the MZs is driven by the intermole-
cular interactions consisting of vdW interactions between two
(7) Munro, O. Q.; du Toit, K.; Drewes, S. E.; Crouch, N. R.;
Mulholland, D. A. New J. Chem. 2006, 30, 197.
(8) Bisson, A. P.; Carver, F. J.; Eggleston, D. S.; Haltiwanger, R. C.;
Hunter, C. A.; Livingstone, D. L.; McCabe, J. F.; Rotger, C.; Rowan, A. E.
J. Am. Chem. Soc. 2000, 122, 8856.
(9) Tao, F.; Bernasek, S. L. J. Am. Chem. Soc. 2005, 127, 12750.
(10) Vonau, F.; Suhr, D.; Aubel, D.; Bouteiller, L.; Reiter, G.; Simon,
L. Phys. Rev. Lett. 2005, 94, No. 066103.
(11) Shu, L.; Mu, Z.; Fuchs, H.; Chi, L.; Mayor, M. Chem. Commun.
2006, 1862.
(12) Manz, T. A.; Sholl, D. S. J. Chem. Theory Comput. 2010, 6, 2455.
(13) Barth, J. V.; Brune, H.; Ertl, G.; Behm, R. J. Phys. Rev. B
1990, 42, 9307.
(14) Kirakosian, A.; Comstock, M. J.; Cho, J.; Crommie, M. F. Phys.
Rev. B 2005, 71, No. 113409.
alkyl chains and CꢀH O hydrogen-bonding interactions, and
3 3 3
the moleculeꢀsubstrate interactions affect the direction of the
MZ on the substrate. The results of the present study may
provide a novel way of controlling the width of the MZ by tuning
the lengths of the alkyl chains.
(15) Henzl, J.; Mehlhorn, M.; Gawronski, H.; Rieder, K.-H.;
Morgenstern, K. Angew. Chem., Int. Ed. 2006, 45, 603.
(16) Choi, B.-Y.; Kahng, S.-J.; Kim, S.; Kim, H.; Kim, H. W.; Song,
Y. J.; Ihm, J.; Kuk, Y. Phys. Rev. Lett. 2006, 96, No. 156106.
(17) Miwa, J. A.; Weigelt, S.; Gersen, H.; Besenbacher, F.; Rosei, F.;
Linderoth, T. R. J. Am. Chem. Soc. 2006, 128, 3164.
(18) Kim, H. W.; Han, M.; Shin, H.-J.; Lim, S.; Oh, Y.; Tamada, K.;
Hara, M.; Kim, Y.; Kawai, M.; Kuk, Y. Phys. Rev. Lett. 2011, 106, No.
146101.
’ ASSOCIATED CONTENT
S
Supporting Information. Details of the synthesis of the
b
(19) Vonau, F.; Aubel, D.; Bouteiller, L.; Reiter, G.; Simon, L. Phys.
Rev. Lett. 2007, 99, No. 086103.
EtOꢀAzꢀOHx molecule, computational details, selected atom-
ic charges, selected geometrical parameters, and Cartesian co-
ordinates of optimized MZs. This material is available free of
’ AUTHOR INFORMATION
Corresponding Author
Present Addresses
#The Institute for Solid State Physics, The University of Tokyo,
Kashiwa-no-ha, Kashiwa 277ꢀ8581, Japan.
9238
dx.doi.org/10.1021/ja2031486 |J. Am. Chem. Soc. 2011, 133, 9236–9238