4th EucheMs chemistry congress

tuesday, 28-Aug 2012
s736
chem. Listy 106, s587–s1425 (2012)
Nanochemistry / Nanotechnology / Molecular machines, Carbon tubes, sheets, balls
Molecular devices and machines – ii
o - 2 0 2
MoLeCuLAr rotAry MotorS
B. ferinGA 1
1 University of Groningen, Chemistry, Groningen, Netherlands
In our body a fascinating collection of ingenious molecular
motors and machines make it possible that our cells divide, that
we can use our muscles and that the consumption of ATP can be
used to generate force and mobility. A billion times larger than
these nanoscale protein motors in Nature are the plethora of
macroscopic motors that power the cars and machinery in daily
life. The ingenious structures and complex functions present in
biological systems offer a great challenge to develop synthetic
nanostructured materials with functions controllable at the
molecular level. Molecular motors stand out among the most
challenging goals in nanoscience and will provide the heart of
future molecular level machinery. Both linear and rotary motors
are shown as well as the principle of a chemical powered
molecular motor. Progress in the construction of molecular motors
anchored to surfaces, the realization of autonomous movement
and the application of molecular motors to perform useful
functions is discussed.
Keywords: molecular motor; molecular machines;
Molecular devices and machines – ii
4 th EucheMs chemistry congress
o - 2 0 3
An APPLied voLtAGe-triGGered SinGLe
MoLeCuLAr SPin SwitCh
G. hArzMAnn 1 , r. friSendA 2 ,
e. Burzuri LinAreS 2 , h. vAn der zAnt 2 ,
M. MAyor 1
1 University of Basel, Department of Chemistry, Basel,
Switzerland
2 Kavli Institute of Nanoscience Delft University of Technology,
Department of Quantum Nanoscience, Delft, Netherlands
Herein we report design and successful synthesis of several
homoleptic and heteroleptic Fe-bisterpyridine complexes.
Especially the implementation of heteroleptic Fe-bisterpyridine
complexes into miniaturized electronic devices is of high interest
in the field of molecular electronics due to the complexes’
potential capability of acting as applied voltage-triggered single
molecular spin switches.
To allow a spin switching behavior on a single molecular
level the accordant tailor-made molecules had to be immobilizable
between two Au-electrodes. Additionally they had to contain a
core Fe(II)-ion exhibiting an externally controllable spin state.
Therefore we came up with different heteroleptic
Fe-bisterpyridine complexes each bearing a symmetric thiolfunctionalized
terpyridine ligand to enable the complexes’
immobilization between two electrodes. The varying second
terpyridine ligand incorporated customizable push-/pull-systems
exhibiting a strong dipole moment needed to provide the desired
sensitivity of the described system towards an applied
electric field. The challenge to assemble the uncommon
4,4''-disubstitution pattern required for the terpyridine core moiety
was overcome by the development of an unprecedented synthetic
route. We applied Suzuki-Miyaura cross coupling reactions
utilizing suitable 4-substituted lithium triisopropyl
2-pyridylborates to form the desired 4,4''-disubstituted 2,2':6',2''-
-terpyridine ligands. Remarkably this coupling methodology,
though inevitably depending on α-boronylated heteroaryls, allows
a successful assembly of several 2,2':6',2''-terpyridines avoiding
the concurring and usually favored proto-deboronation
previously described in literature. Finally a cascade of further
Suzuki-Miyaura reactions led to the desired target compounds.
For all Fe-bisterpyridine complexes characterized by X-ray
crystallography consistently almost perfect octahedral geometries
were revealed indicating the required low-spin configurations of
the Fe(II)-ions. In the ongoing physical experiments an alternation
of the applied electric field strengths between the Au-electrodes
should result in a distortion of the original octahedral geometry
towards pseudo-planarity triggered by the alignment of the
push/pull-ligand with the externally applied electric field. This
should then result in a reversible switching of the Fe(II)-ion’s spin
state.
Keywords: Molecular Electronics; Cross-coupling; Tridentate
ligands; Spin crossover; Single-molecule studies;
AUGUst 26–30, 2012, PrAGUE, cZEcH rEPUbLIc