The Experts below are selected from a list of 41307 Experts worldwide ranked by ideXlab platform
Hong-jun Gao - One of the best experts on this subject based on the ideXlab platform.
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modification of the Potential landscape of molecular rotors on au 111 by the presence of an stm tip
Nano Letters, 2018Co-Authors: Yun Cao, Anne Bakker, Cristian A. Strassert, Xiao Lin, Karl-heinz Ernst, Harald Fuchs, Hong-jun GaoAbstract:Molecular rotors on solid surfaces are fundamental components of molecular machines. No matter whether the rotation is activated by heat, electric field or light, it is determined by the intrinsic Rotational Potential landscape. Therefore, tuning the Potential landscape is of great importance for future applications of controlled molecular rotors. Here, using scanning tunneling microscopy (STM), we demonstrate that both tip–molecule distance and sample bias can modify the Rotational Potential of molecular rotors. We achieve the Potential energy difference variations of ∼0.3 meV/pm and ∼18 meV/V between two configurations of a molecular rotor, a tetra-tert-butyl nickel phthalocyanine molecule on Au(111) substrate. Further analysis indicates that the mechanism of modifying the Rotational Potential is a combination of the van der Waals interaction and the interaction between the molecular dipole and an electric field. This work provides insight into the methods used to modify the effective Rotational potenti...
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Modification of the Potential Landscape of Molecular Rotors on Au(111) by the Presence of an STM Tip
2018Co-Authors: Yun Cao, Anne Bakker, Cristian A. Strassert, Xiao Lin, Karl-heinz Ernst, Harald Fuchs, Hong-jun GaoAbstract:Molecular rotors on solid surfaces are fundamental components of molecular machines. No matter whether the rotation is activated by heat, electric field or light, it is determined by the intrinsic Rotational Potential landscape. Therefore, tuning the Potential landscape is of great importance for future applications of controlled molecular rotors. Here, using scanning tunneling microscopy (STM), we demonstrate that both tip–molecule distance and sample bias can modify the Rotational Potential of molecular rotors. We achieve the Potential energy difference variations of ∼0.3 meV/pm and ∼18 meV/V between two configurations of a molecular rotor, a tetra-tert-butyl nickel phthalocyanine molecule on Au(111) substrate. Further analysis indicates that the mechanism of modifying the Rotational Potential is a combination of the van der Waals interaction and the interaction between the molecular dipole and an electric field. This work provides insight into the methods used to modify the effective Rotational Potential energy of molecular rotors
Yun Cao - One of the best experts on this subject based on the ideXlab platform.
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modification of the Potential landscape of molecular rotors on au 111 by the presence of an stm tip
Nano Letters, 2018Co-Authors: Yun Cao, Anne Bakker, Cristian A. Strassert, Xiao Lin, Karl-heinz Ernst, Harald Fuchs, Hong-jun GaoAbstract:Molecular rotors on solid surfaces are fundamental components of molecular machines. No matter whether the rotation is activated by heat, electric field or light, it is determined by the intrinsic Rotational Potential landscape. Therefore, tuning the Potential landscape is of great importance for future applications of controlled molecular rotors. Here, using scanning tunneling microscopy (STM), we demonstrate that both tip–molecule distance and sample bias can modify the Rotational Potential of molecular rotors. We achieve the Potential energy difference variations of ∼0.3 meV/pm and ∼18 meV/V between two configurations of a molecular rotor, a tetra-tert-butyl nickel phthalocyanine molecule on Au(111) substrate. Further analysis indicates that the mechanism of modifying the Rotational Potential is a combination of the van der Waals interaction and the interaction between the molecular dipole and an electric field. This work provides insight into the methods used to modify the effective Rotational potenti...
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Modification of the Potential Landscape of Molecular Rotors on Au(111) by the Presence of an STM Tip
2018Co-Authors: Yun Cao, Anne Bakker, Cristian A. Strassert, Xiao Lin, Karl-heinz Ernst, Harald Fuchs, Hong-jun GaoAbstract:Molecular rotors on solid surfaces are fundamental components of molecular machines. No matter whether the rotation is activated by heat, electric field or light, it is determined by the intrinsic Rotational Potential landscape. Therefore, tuning the Potential landscape is of great importance for future applications of controlled molecular rotors. Here, using scanning tunneling microscopy (STM), we demonstrate that both tip–molecule distance and sample bias can modify the Rotational Potential of molecular rotors. We achieve the Potential energy difference variations of ∼0.3 meV/pm and ∼18 meV/V between two configurations of a molecular rotor, a tetra-tert-butyl nickel phthalocyanine molecule on Au(111) substrate. Further analysis indicates that the mechanism of modifying the Rotational Potential is a combination of the van der Waals interaction and the interaction between the molecular dipole and an electric field. This work provides insight into the methods used to modify the effective Rotational Potential energy of molecular rotors
Miguel A Garciagaribay - One of the best experts on this subject based on the ideXlab platform.
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rotation of a bulky triptycene in the solid state toward engineered nanoscale artificial molecular machines
Journal of the American Chemical Society, 2014Co-Authors: Xing Jiang, Braulio Rodriguezmolina, Narega Nazarian, Miguel A GarciagaribayAbstract:We report the design and dynamics of a solid-state molecular rotor with a large triptycene rotator. With a cross-section and surface area that are 2 and 3 times larger than those of the phenylene rotators previously studied in the solid state, it is expected that van der Waals forces and steric hindrance will render the motion of the larger triptycene more difficult. To address this challenge, we used a rigid and shape-persistent stator in a dendritic structure that reaches ca. 3.6 nm in length. Using variable-temperature solid-state 2H NMR spectroscopy, we determined a symmetric three-fold Rotational Potential with a barrier of 10.2 kcal/mol and a pre-exponential factor of 1.1 × 1010 s–1, which correspond to ca. 4600 Brownian jumps per second in the solid state at 300 K.
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Rotational dynamics in a crystalline molecular gyroscope by variable temperature 13c nmr 2h nmr x ray diffraction and force field calculations
Journal of the American Chemical Society, 2007Co-Authors: Tinhalfredo V Khuong, Hung Dang, Peter D Jarowski, E F Maverick, Miguel A GarciagaribayAbstract:A combination of solid-state 13C CPMAS NMR, 2H NMR, X-ray-determined anisotropic displacement parameters (ADPs), and molecular mechanics calculations were used to analyze the Rotational dynamics of 1,4-bis[3,3,3-tris(m-methoxyphenyl)propynyl]benzene (3A), a structure that emulates a gyroscope with a p-phenylene group acting as a rotator and two m-methoxy-substituted trityl groups acting as a stator. The line shape analysis of VT 13C CPMAS and broad-band 2H NMR data were in remarkable agreement with each other, with Rotational barriers of 11.3 and 11.5 kcal/mol, respectively. The barriers obtained by analysis of ADPs obtained by single-crystal X-ray diffraction at 100 and 200 K, assuming a sinusoidal Potential, were 10.3 and 10.1 kcal, respectively. A similar analysis of an X-ray structure solved from data acquired at 300 K suggested a barrier of only 8.0 kcal/mol. Finally, a Rotational Potential calculated with a finite cluster model using molecular mechanics revealed a symmetric but nonsinusoidal potenti...
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dielectric response of a dipolar molecular rotor crystal
Physical Review B, 2005Co-Authors: Robert D Horansky, Tinhalfredo V Khuong, Peter D Jarowski, Laura Clarke, John C Price, Miguel A GarciagaribayAbstract:We report the results of the dynamics of a three dimensional lattice of dipolar molecular rotors where the unit cells consist of a dipolar phenylene ring rotating about an axle stabilized by stationary triphenyl groups. The molecules are synthesized such that the lattice may be customized to elicit novel and useful physical phenomena. Using dielectric spectroscopy and 2 H NMR, we demonstrate rapid thermal rotation of the molecular rotors in the solid state, and characterize the depth and asymmetry of the Rotational Potential. Calculations show that rotor-rotor interactions are weak in this structure, and the Rotational Potential is dominated by steric interactions between each rotary element and the nonrotating portions of neighboring molecules.
Daniel Sebastiani - One of the best experts on this subject based on the ideXlab platform.
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tunneling of coupled methyl quantum rotors in 4 methylpyridine single rotor Potential versus coupling interaction
Journal of Chemical Physics, 2017Co-Authors: Somayeh Khazaei, Daniel SebastianiAbstract:We study the influence of Rotational coupling between a pair of methyl rotators on the tunneling spectrum in condensed phase. Two interacting adjacent methyl groups are simulated within a coupled-pair model composed of static Rotational Potential created by the chemical environment and the interaction Potential between two methyl groups. We solve the two-dimensional time-independent Schrodinger equation analytically by expanding the wave functions on the basis set of two independent free-rotor functions. We investigate three scenarios which differ with respect to the relative strength of single-rotor and coupling Potential. For each scenario, we illustrate the dependence of the energy level scheme on the coupling strength. It is found that the main determinant of splitting energy levels tends to be a function of the ratio of strengths of coupling and single-rotor Potential. The tunnel splitting caused by coupling is maximized for the coupled rotors in which their total hindering Potential is relatively shallow. Such a weakly hindered methyl Rotational Potential is predicted for 4-methylpyridine at low temperature. The experimental observation of multiple tunneling peaks arising from a single type of methyl group in 4-methylpyridine in the inelastic neutron scattering spectrum is widely attributed to the rotor-rotor coupling. In this regard, using a set of first-principles calculations combined with the nudged elastic band method, we investigate the Rotational Potential energy surface (PES) of the coaxial pairs of rotors in 4-methylpyridine. A Numerov-type method is used to numerically solve the two-dimensional time-independent Schrodinger equation for the calculated 2D-density functional theory profile. Our computed energy levels reproduce the observed tunneling transitions well. Moreover, the calculated density distribution of the three methyl protons resembles the experimental nuclear densities obtained from the Fourier difference method. By mapping the calculated first-principles PES on the model, it is confirmed that the hindering Potential in 4-methylpyridine consists of proportionally shallow single-rotor Potential to coupling interaction.
Xiao Lin - One of the best experts on this subject based on the ideXlab platform.
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modification of the Potential landscape of molecular rotors on au 111 by the presence of an stm tip
Nano Letters, 2018Co-Authors: Yun Cao, Anne Bakker, Cristian A. Strassert, Xiao Lin, Karl-heinz Ernst, Harald Fuchs, Hong-jun GaoAbstract:Molecular rotors on solid surfaces are fundamental components of molecular machines. No matter whether the rotation is activated by heat, electric field or light, it is determined by the intrinsic Rotational Potential landscape. Therefore, tuning the Potential landscape is of great importance for future applications of controlled molecular rotors. Here, using scanning tunneling microscopy (STM), we demonstrate that both tip–molecule distance and sample bias can modify the Rotational Potential of molecular rotors. We achieve the Potential energy difference variations of ∼0.3 meV/pm and ∼18 meV/V between two configurations of a molecular rotor, a tetra-tert-butyl nickel phthalocyanine molecule on Au(111) substrate. Further analysis indicates that the mechanism of modifying the Rotational Potential is a combination of the van der Waals interaction and the interaction between the molecular dipole and an electric field. This work provides insight into the methods used to modify the effective Rotational potenti...
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Modification of the Potential Landscape of Molecular Rotors on Au(111) by the Presence of an STM Tip
2018Co-Authors: Yun Cao, Anne Bakker, Cristian A. Strassert, Xiao Lin, Karl-heinz Ernst, Harald Fuchs, Hong-jun GaoAbstract:Molecular rotors on solid surfaces are fundamental components of molecular machines. No matter whether the rotation is activated by heat, electric field or light, it is determined by the intrinsic Rotational Potential landscape. Therefore, tuning the Potential landscape is of great importance for future applications of controlled molecular rotors. Here, using scanning tunneling microscopy (STM), we demonstrate that both tip–molecule distance and sample bias can modify the Rotational Potential of molecular rotors. We achieve the Potential energy difference variations of ∼0.3 meV/pm and ∼18 meV/V between two configurations of a molecular rotor, a tetra-tert-butyl nickel phthalocyanine molecule on Au(111) substrate. Further analysis indicates that the mechanism of modifying the Rotational Potential is a combination of the van der Waals interaction and the interaction between the molecular dipole and an electric field. This work provides insight into the methods used to modify the effective Rotational Potential energy of molecular rotors
