8 research outputs found
Branched Redox-Active Complexes for the Study of Novel Charge Transport Processes
The syntheses and electrochemical/optical
properties of some branched and linear 1,1â˛-substituted ferrocene
complexes for molecular electronics are described. Metal centers were
extended (and where relevant, connected) by arylethynyl spacers functionalized
with <i>m-</i>pyridyl, <i>tert-</i>butylthiol
(S<sup><i>t</i></sup>Bu), and trimethylsilyl (TMS) moieties.
Such systems provide two well-defined molecular pathways for electron
transfer and hold interesting prospects for the study of new charge
transport processes, such as quantum interference, local gating, and
correlated hopping events
Extreme Conductance Suppression in Molecular Siloxanes
Single-molecule conductance
studies have traditionally focused
on creating highly conducting molecular wires. However, progress in
nanoscale electronics demands insulators just as it needs conductors.
Here we describe the single-molecule length-dependent conductance
properties of the classic silicon dioxide insulator. We synthesize
molecular wires consisting of SiâO repeat units and measure
their conductance through the scanning tunneling microscope-based
break-junction method. These molecules yield conductance lower than
alkanes of the same length and the largest length-dependent conductance
decay of any molecular systems measured to date. We calculate single-molecule
junction transmission and the complex band structure of the infinite
1D material for siloxane, in comparison with silane and alkane, and
show that the large conductance decay is intrinsic to the nature of
the SiâO bond. This work highlights the potential for siloxanes
to function as molecular insulators in electronics
In Situ Formation of NâHeterocyclic Carbene-Bound Single-Molecule Junctions
Self-assembled
monolayers (SAMs) formed using N-heterocyclic carbenes
(NHCs) have recently emerged as thermally and chemically ultrastable
alternatives to those formed from thiols. The rich chemistry and strong
Ď-donating ability of NHCs offer unique prospects for applications
in nanoelectronics, sensing, and electrochemistry. Although stable
in SAMs, free carbenes are notoriously reactive, making their electronic
characterization challenging. Here we report the first investigation
of electron transport across single NHC-bound molecules using the
scanning tunneling microscope-based break junction (STM-BJ) technique.
We develop a series of air-stable metal NHC complexes that can be
electrochemically reduced in situ to form NHCâelectrode contacts,
enabling reliable single-molecule conductance measurements of NHCs
under ambient conditions. Using this approach, we show that the conductance
of an NHC depends on the identity of the single metal atom to which
it is coordinated in the junction. Our observations are supported
by density functional theory (DFT) calculations, which also firmly
establish the contributions of the NHC linker to the junction transport
characteristics. Our work demonstrates a powerful method to probe
electron transfer across NHCâelectrode interfaces; more generally,
it opens the door to the exploitation of surface-bound NHCs in constructing
novel, functionalized electrodes and/or nanoelectronic devices
In Situ Formation of NâHeterocyclic Carbene-Bound Single-Molecule Junctions
Self-assembled
monolayers (SAMs) formed using N-heterocyclic carbenes
(NHCs) have recently emerged as thermally and chemically ultrastable
alternatives to those formed from thiols. The rich chemistry and strong
Ď-donating ability of NHCs offer unique prospects for applications
in nanoelectronics, sensing, and electrochemistry. Although stable
in SAMs, free carbenes are notoriously reactive, making their electronic
characterization challenging. Here we report the first investigation
of electron transport across single NHC-bound molecules using the
scanning tunneling microscope-based break junction (STM-BJ) technique.
We develop a series of air-stable metal NHC complexes that can be
electrochemically reduced in situ to form NHCâelectrode contacts,
enabling reliable single-molecule conductance measurements of NHCs
under ambient conditions. Using this approach, we show that the conductance
of an NHC depends on the identity of the single metal atom to which
it is coordinated in the junction. Our observations are supported
by density functional theory (DFT) calculations, which also firmly
establish the contributions of the NHC linker to the junction transport
characteristics. Our work demonstrates a powerful method to probe
electron transfer across NHCâelectrode interfaces; more generally,
it opens the door to the exploitation of surface-bound NHCs in constructing
novel, functionalized electrodes and/or nanoelectronic devices
In Situ Formation of NâHeterocyclic Carbene-Bound Single-Molecule Junctions
Self-assembled
monolayers (SAMs) formed using N-heterocyclic carbenes
(NHCs) have recently emerged as thermally and chemically ultrastable
alternatives to those formed from thiols. The rich chemistry and strong
Ď-donating ability of NHCs offer unique prospects for applications
in nanoelectronics, sensing, and electrochemistry. Although stable
in SAMs, free carbenes are notoriously reactive, making their electronic
characterization challenging. Here we report the first investigation
of electron transport across single NHC-bound molecules using the
scanning tunneling microscope-based break junction (STM-BJ) technique.
We develop a series of air-stable metal NHC complexes that can be
electrochemically reduced in situ to form NHCâelectrode contacts,
enabling reliable single-molecule conductance measurements of NHCs
under ambient conditions. Using this approach, we show that the conductance
of an NHC depends on the identity of the single metal atom to which
it is coordinated in the junction. Our observations are supported
by density functional theory (DFT) calculations, which also firmly
establish the contributions of the NHC linker to the junction transport
characteristics. Our work demonstrates a powerful method to probe
electron transfer across NHCâelectrode interfaces; more generally,
it opens the door to the exploitation of surface-bound NHCs in constructing
novel, functionalized electrodes and/or nanoelectronic devices
In Situ Formation of NâHeterocyclic Carbene-Bound Single-Molecule Junctions
Self-assembled
monolayers (SAMs) formed using N-heterocyclic carbenes
(NHCs) have recently emerged as thermally and chemically ultrastable
alternatives to those formed from thiols. The rich chemistry and strong
Ď-donating ability of NHCs offer unique prospects for applications
in nanoelectronics, sensing, and electrochemistry. Although stable
in SAMs, free carbenes are notoriously reactive, making their electronic
characterization challenging. Here we report the first investigation
of electron transport across single NHC-bound molecules using the
scanning tunneling microscope-based break junction (STM-BJ) technique.
We develop a series of air-stable metal NHC complexes that can be
electrochemically reduced in situ to form NHCâelectrode contacts,
enabling reliable single-molecule conductance measurements of NHCs
under ambient conditions. Using this approach, we show that the conductance
of an NHC depends on the identity of the single metal atom to which
it is coordinated in the junction. Our observations are supported
by density functional theory (DFT) calculations, which also firmly
establish the contributions of the NHC linker to the junction transport
characteristics. Our work demonstrates a powerful method to probe
electron transfer across NHCâelectrode interfaces; more generally,
it opens the door to the exploitation of surface-bound NHCs in constructing
novel, functionalized electrodes and/or nanoelectronic devices
In Situ Formation of NâHeterocyclic Carbene-Bound Single-Molecule Junctions
Self-assembled
monolayers (SAMs) formed using N-heterocyclic carbenes
(NHCs) have recently emerged as thermally and chemically ultrastable
alternatives to those formed from thiols. The rich chemistry and strong
Ď-donating ability of NHCs offer unique prospects for applications
in nanoelectronics, sensing, and electrochemistry. Although stable
in SAMs, free carbenes are notoriously reactive, making their electronic
characterization challenging. Here we report the first investigation
of electron transport across single NHC-bound molecules using the
scanning tunneling microscope-based break junction (STM-BJ) technique.
We develop a series of air-stable metal NHC complexes that can be
electrochemically reduced in situ to form NHCâelectrode contacts,
enabling reliable single-molecule conductance measurements of NHCs
under ambient conditions. Using this approach, we show that the conductance
of an NHC depends on the identity of the single metal atom to which
it is coordinated in the junction. Our observations are supported
by density functional theory (DFT) calculations, which also firmly
establish the contributions of the NHC linker to the junction transport
characteristics. Our work demonstrates a powerful method to probe
electron transfer across NHCâelectrode interfaces; more generally,
it opens the door to the exploitation of surface-bound NHCs in constructing
novel, functionalized electrodes and/or nanoelectronic devices
In Situ Formation of NâHeterocyclic Carbene-Bound Single-Molecule Junctions
Self-assembled
monolayers (SAMs) formed using N-heterocyclic carbenes
(NHCs) have recently emerged as thermally and chemically ultrastable
alternatives to those formed from thiols. The rich chemistry and strong
Ď-donating ability of NHCs offer unique prospects for applications
in nanoelectronics, sensing, and electrochemistry. Although stable
in SAMs, free carbenes are notoriously reactive, making their electronic
characterization challenging. Here we report the first investigation
of electron transport across single NHC-bound molecules using the
scanning tunneling microscope-based break junction (STM-BJ) technique.
We develop a series of air-stable metal NHC complexes that can be
electrochemically reduced in situ to form NHCâelectrode contacts,
enabling reliable single-molecule conductance measurements of NHCs
under ambient conditions. Using this approach, we show that the conductance
of an NHC depends on the identity of the single metal atom to which
it is coordinated in the junction. Our observations are supported
by density functional theory (DFT) calculations, which also firmly
establish the contributions of the NHC linker to the junction transport
characteristics. Our work demonstrates a powerful method to probe
electron transfer across NHCâelectrode interfaces; more generally,
it opens the door to the exploitation of surface-bound NHCs in constructing
novel, functionalized electrodes and/or nanoelectronic devices