CPM Seminar
Switching with Molecules at Surfaces
T.A. Jung
NCCR Nanoscale Science, Institut für Physik &
Micro- & Nanotechnology, Paul Scherrer Institute
![[OEP assembly]](CPM_jung.jpg)
Fig. 1: Octa-ethyl-porphyrin (OEP) assembled inside a supra-molecular porous
network formed from perylene. At room temperature STM reveals ring like
structures due to confined libration.
One of the key challenges in molecular machines and devices is the reproducible
assembly of functional units in an addressable arrangement. By combining
concepts of supra-molecular chemistry [1] and surface
science, increasingly complex functional layers have been manufactured
and explored. Site specific molecular interaction is the generic origin
of molecular self assembly [2]. The selective chemical
bonding programmed into the architecture of the molecular building block
leads to specific inter-molecular and molecule substrate interactions
[3]. In combination with entropic and conformational
mechanisms [4], distinctively different molecular layers
and 2D phases emerge [5]. By using building blocks which
combine attractive and repulsive interactions which e.g. involve longer
range dipole forces and entropic mobility structural parameters such as the
periodicity can be tuned to reach values up to 7.2 nm [6].
Beyond supra-molecular assembly, extended networks have been created by
a thermally activated chemical reaction [7] and have
been used as a template for supra-molecular organisation of ad molecules
[8], and for the confinement of coupled quantum dots from
delocalised substrate electronic states [9]. A single chain
covalent polymer has also been formed [10]. Ultimately,
adressable supra-molecular rotor-stator systems [11,12], in particular a supra-molecular rotational switch [12] have been described. Molecular layers on insulator
thin films [13] and on ferromagnetic substrates
[14] have been characterised for their electronic
and magnetic coupling which depends on physical parameters and chemical
stimuli [15]. Notably also supramolecular macroscycles
[16] have been described, as well as self assembling
arrays of Donor / Acceptor systems built from C60 and Phthalocyanines [17]. All these examples have in common that the supra-molecular
structures are extremely well defined on a level which is impossible to reach
by conventional top-down assembly techniques. The physics and chemistry of
these unprecedented addressable systems provides insight into mechanic and
electronic ‘function’ on a single molecular scale.
References
[1] J. M. Lehn Supramolecular Chemistry, VCH, Weinheim,
1995.
[2] G. M. Whitesides, et al. Science 254, 1312
(1991)
[3] S. Berner et. al. Phys. Rev. B 68, 115410
(2003)
[4] T. A. Jung et al. Nature 386, 696
(1997)
[5] M. de Wild et al. ChemPhysChem 10, 881
(2002)
[6] D. Bonifazi et al. Angewandte Chemie
Intl. Ed., 43, 4759 (2004). N.
Wintjes et al. Chem.
Eur. J. 41, 5794 (2008).
[7] M. Stoehr et al. Angewandte Chemie Intl. Ed.,
44, 16 (2005)
[8] H. Spillmann et al. Advanced Materials 18,
275-279 (2006)
[9] J. Lobo-Checa et al. Science 325, 300
(2009)
[10] M. Matena et al. Angewandte Chemie Intl. Ed.
120, 1-5 (2008).
[11] M. Wahl et al. Chem. Commun., 2007,
1349-1351
[12] N. Wintjes et al. Angewandte Chemie Intl. Ed.
119, 4167 (2007).
[13] L. Ramoino et al. Chem. Phys. Lett. 417
2227 (2006).
[14] A. Scheybal et al. Chem. Phys. Lett. 411
214 (2005).
[15] C. Waeckerlin et al. Nature Communications
2010 1:61 DOI: 10.1038/ncomms1057
[16] L. A. Fendt et al. Chem. Eur. J. 15,
11139 (2009).
[17] T. Samuely et al. J. Phys. Chem. C 113,
No. 45, 2009.
Monday, October 18th 2010, 12:00
Ernest Rutherford Physics Building, R.E. Bell Conference Room (room 103)
|