23 research outputs found
Spiro-Conjugated Molecular Junctions: Between Jahn–Teller Distortion and Destructive Quantum Interference
The
quest for molecular structures exhibiting strong quantum interference
effects in the transport setting has long been on the forefront of
chemical research. We establish theoretically that the unusual geometry
of spiro-conjugated systems gives rise to complete destructive interference
in the resonant-transport regime. This results in a current blockade
of the type not present in meta-connected benzene or similar molecular
structures. We further show that these systems can undergo a transport-driven
Jahn–Teller distortion, which can lift the aforementioned destructive-interference
effects. The overall transport characteristics are determined by the
interplay between the two phenomena. Spiro-conjugated systems may
therefore serve as a novel platform for investigations of quantum
interference and vibronic effects in the charge-transport setting.
The potential to control quantum interference in these systems can
also turn them into attractive components in designing functional
molecular circuits
Intricate Hydrogen-Bonded Networks: Binary and Ternary Combinations of Uracil, PTCDI, and Melamine
We report the formation of two- and three-component porous supramolecular networks from combinations of uracil, PTCDI, and melamine. The structures, which are formed on Au(111) in ultra-high vacuum (UHV) and studied by scanning tunneling microscopy (STM), are stabilized by hydrogen bonds. We show that two bimolecular networks comprising uracil and PTCDI can be formed, one of which contains two pore geometries and is composed of 28 molecules per unit cell. In addition, we observe two different ordered structures from mixtures of melamine and uracil. By combining all three of these species, we demonstrate the formation of a single ternary structure that contains 33 molecules per unit cell. Our results demonstrate the capacity of hydrogen bonding to produce highly complex structures, and open up the possibility of forming a wide range of new structures from combinations of nucleic bases and other small organic molecules
Determination of the Thermal Stability of the Fullerene Dimers C<sub>120</sub>, C<sub>120</sub>O, and C<sub>120</sub>O<sub>2</sub>
We have produced the fullerene dimers C120, C120O, and C120O2 by a high-speed vibration milling technique.
The thermal stability of C120, C120O, and C120O2 has been studied in the temperature range 150−350 °C for
up to 4 h under vacuum. The bridging oxygen atoms were found to substantially increase the stability of the
fullerene dimer molecules
N@C<sub>60</sub>–Porphyrin: A Dyad of Two Radical Centers
Dyads of endohedral nitrogen fullerene and porphyrin
have been
synthesized. In the two-radical-center dyad, the copperÂ(II) tetraphenylporphyrin
suppressed the electron spin resonance (ESR) signal of N@C<sub>60</sub> through intramolecular dipolar coupling with a strength of 27.0
MHz. Demetalation of the metalloporphyrin moiety of the dyad, which
effectively turned the two-radical-center dyad into a single-radical-center
dyad, recovered 82% of the ESR signal of N@C<sub>60</sub>. Such mechanism
of switching a spin state on and off could find use in molecular spintronics
applications
Capturing the Motion of Molecular Nanomaterials Encapsulated within Carbon Nanotubes with Ultrahigh Temporal Resolution
We use in situ low-voltage aberration corrected high resolution transmission electron microscopy with a temporal resolution of 80 ms to track the motional dynamics of nanostructures encapsulated within carbon nanotubes. Two different nanostructures are examined and both are produced by electron beam irradiation of peapods containing La@C82 metallofullerenes. The first novel nanostructure consists of a LaC2 metal cluster attached to carbon nanotube inside a nanotube host. It exhibits repeated nanopiston-like behavior over a 5 min duration, driven by energy supplied by electron beam irradiation. Interaction of the metal cluster with the nanotube host is also examined, revealing that the metal cluster can open up the nanotube sidewall, exit, and then seal the hole in the wall back up with carbon from the surrounding region. Finally, the intrinsic motional dynamics of an isolated single fullerene within a SWNT is captured and we report velocities up to 112 nm/s
Capturing the Motion of Molecular Nanomaterials Encapsulated within Carbon Nanotubes with Ultrahigh Temporal Resolution
We use in situ low-voltage aberration corrected high resolution transmission electron microscopy with a temporal resolution of 80 ms to track the motional dynamics of nanostructures encapsulated within carbon nanotubes. Two different nanostructures are examined and both are produced by electron beam irradiation of peapods containing La@C82 metallofullerenes. The first novel nanostructure consists of a LaC2 metal cluster attached to carbon nanotube inside a nanotube host. It exhibits repeated nanopiston-like behavior over a 5 min duration, driven by energy supplied by electron beam irradiation. Interaction of the metal cluster with the nanotube host is also examined, revealing that the metal cluster can open up the nanotube sidewall, exit, and then seal the hole in the wall back up with carbon from the surrounding region. Finally, the intrinsic motional dynamics of an isolated single fullerene within a SWNT is captured and we report velocities up to 112 nm/s
Capturing the Motion of Molecular Nanomaterials Encapsulated within Carbon Nanotubes with Ultrahigh Temporal Resolution
We use in situ low-voltage aberration corrected high resolution transmission electron microscopy with a temporal resolution of 80 ms to track the motional dynamics of nanostructures encapsulated within carbon nanotubes. Two different nanostructures are examined and both are produced by electron beam irradiation of peapods containing La@C82 metallofullerenes. The first novel nanostructure consists of a LaC2 metal cluster attached to carbon nanotube inside a nanotube host. It exhibits repeated nanopiston-like behavior over a 5 min duration, driven by energy supplied by electron beam irradiation. Interaction of the metal cluster with the nanotube host is also examined, revealing that the metal cluster can open up the nanotube sidewall, exit, and then seal the hole in the wall back up with carbon from the surrounding region. Finally, the intrinsic motional dynamics of an isolated single fullerene within a SWNT is captured and we report velocities up to 112 nm/s
Capturing the Motion of Molecular Nanomaterials Encapsulated within Carbon Nanotubes with Ultrahigh Temporal Resolution
We use in situ low-voltage aberration corrected high resolution transmission electron microscopy with a temporal resolution of 80 ms to track the motional dynamics of nanostructures encapsulated within carbon nanotubes. Two different nanostructures are examined and both are produced by electron beam irradiation of peapods containing La@C82 metallofullerenes. The first novel nanostructure consists of a LaC2 metal cluster attached to carbon nanotube inside a nanotube host. It exhibits repeated nanopiston-like behavior over a 5 min duration, driven by energy supplied by electron beam irradiation. Interaction of the metal cluster with the nanotube host is also examined, revealing that the metal cluster can open up the nanotube sidewall, exit, and then seal the hole in the wall back up with carbon from the surrounding region. Finally, the intrinsic motional dynamics of an isolated single fullerene within a SWNT is captured and we report velocities up to 112 nm/s
Capturing the Motion of Molecular Nanomaterials Encapsulated within Carbon Nanotubes with Ultrahigh Temporal Resolution
We use in situ low-voltage aberration corrected high resolution transmission electron microscopy with a temporal resolution of 80 ms to track the motional dynamics of nanostructures encapsulated within carbon nanotubes. Two different nanostructures are examined and both are produced by electron beam irradiation of peapods containing La@C82 metallofullerenes. The first novel nanostructure consists of a LaC2 metal cluster attached to carbon nanotube inside a nanotube host. It exhibits repeated nanopiston-like behavior over a 5 min duration, driven by energy supplied by electron beam irradiation. Interaction of the metal cluster with the nanotube host is also examined, revealing that the metal cluster can open up the nanotube sidewall, exit, and then seal the hole in the wall back up with carbon from the surrounding region. Finally, the intrinsic motional dynamics of an isolated single fullerene within a SWNT is captured and we report velocities up to 112 nm/s
Toward Controlled Spacing in One-Dimensional Molecular Chains:  Alkyl-Chain-Functionalized Fullerenes in Carbon Nanotubes
A range of fullerenes (C60) functionalized with long alkyl chains have been synthesized and
inserted into single-walled carbon nanotubes. The impact of the alkyl chain length and of the type of linker
between the addend and the fullerene cage on the geometry of molecular arrays in nanotube has been
studied by high-resolution transmission electron microscopy. In the presence of functional groups the mean
interfullerene separations are significantly increased by 2−8 nm depending on the length of the alkyl chain,
but the periodicity of the fullerene arrays is disrupted due to the conformational flexibility of the alkyl groups