Mechanism of Oxidative Shuttling for [2]Rotaxane in a Stoddart−Heath Molecular Switch:  Density Functional Theory Study with Continuum-Solvation Model

Jang, Yun Hee; Goddard, William A.

doi:10.1021/jp055473c

Cited by 35 publications

(29 citation statements)

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“…In addition to the experimental correlation of the kinetics and thermodynamics of switching in solution with those in devices, this hypothesis was supported by first-principles simulations (Deng et al 2004;Jang & Goddard 2006 figure 3a,b) predicted that the MSCC should be 10-100 times more conductive than the GSCC, in agreement with the experimental MSTJ results. Furthermore, calculation of the frontier molecular orbitals of the two switch states suggested a model for the higher conductivity of the MSCC (Deng et al 2004).…”

Section: Bistable [2]rotaxanes In Molecular Switch Tunnel Junctionssupporting

confidence: 62%

Designing bistable [2]rotaxanes for molecular electronic devices

Dichtel

Heath

Stoddart

2007

Phil. Trans. R. Soc. A.

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The development of molecular electronic components has been accelerated by the promise of increased circuit densities and reduced power consumption. Bistable rotaxanes have been assembled into nanowire crossbar devices, where they may be switched between low-and high-conductivity states, forming the basis for a molecular memory. These memory devices have been scaled to densities of 10 11 bits cm K2, the 2020 node for memory of the International Technology Roadmap for Semiconductors. Investigations of the kinetics and thermodynamics associated with the electromechanical switching processes of several bistable [2]rotaxane derivatives in solution, self-assembled monolayers on gold, polymer electrolyte gels and in molecular switch tunnel junction devices are consistent with a single, universal switching mechanism whose speed is dependent largely on the environment, as well as on the structure of the switching molecule. X-ray reflectometry studies of the bistable rotaxanes assembled into Langmuir monolayers also lend support to an oxidatively driven mechanical switching process. Structural information obtained from Fourier transform reflection absorption infrared spectroscopy of rotaxane monolayers taken before and after evaporation of a Ti top electrode confirmed that the functionality responsible for switching is not affected by the metal deposition process. All the considerable experimental data, taken together with detailed computational work, support the hypothesis that the tunnelling current hysteresis, which forms the basis of memory operation, is a direct result of the electromechanical switching of the bistable rotaxanes.

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Section: Bistable [2]rotaxanes In Molecular Switch Tunnel Junctionssupporting

confidence: 62%

Designing bistable [2]rotaxanes for molecular electronic devices

Dichtel

Heath

Stoddart

2007

Phil. Trans. R. Soc. A.

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“…36,37 In addition, the B3LYP functional has been widely used to investigate the potential energy surfaces (PES) of various systems containing H/C/O. [38][39][40][41][42][43][44] This functional also provides a good description of the PES of transition metal-containing molecules. [45][46][47][48][49][50][51][52][53][54][55] It is important to have a consistent QM method for building a training set, so we have chosen to use the B3LYP functional to build and expand the force field to describe systems such as hydrocarbons, metals, and metal oxides.…”

Section: Quantum Mechanical Calculationsmentioning

confidence: 99%

ReaxFF Reactive Force Field for Molecular Dynamics Simulations of Hydrocarbon Oxidation

2008

Self Cite

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To investigate the initial chemical events associated with high-temperature gas-phase oxidation of hydrocarbons, we have expanded the ReaxFF reactive force field training set to include additional transition states and chemical reactivity of systems relevant to these reactions and optimized the force field parameters against a quantum mechanics (QM)-based training set. To validate the ReaxFF potential obtained after parameter optimization, we performed a range of NVT-MD simulations on various hydrocarbon/O 2 systems. From simulations on methane/O 2 , o-xylene/O 2 , propene/O 2 , and benzene/O 2 mixtures, we found that ReaxFF obtains the correct reactivity trend (propene > o-xylene > methane > benzene), following the trend in the C-H bond strength in these hydrocarbons. We also tracked in detail the reactions during a complete oxidation of isolated methane, propene, and o-xylene to a CO/CO 2 /H 2 O mixture and found that the pathways predicted by ReaxFF are in agreement with chemical intuition and our QM results. We observed that the predominant initiation reaction for oxidation of methane, propene, and o-xylene under fuel lean conditions involved hydrogen abstraction of the methyl hydrogen by molecular oxygen forming hydroperoxyl and hydrocarbon radical species. While under fuel rich conditions with a mixture of these hydrocarbons, we observed different chemistry compared with the oxidation of isolated hydrocarbons including a change in the type of initiation reactions, which involved both decomposition of the hydrocarbon or attack by other radicals in the system. Since ReaxFF is capable of simulating complicated reaction pathways without any preconditioning, we believe that atomistic modeling with ReaxFF provides a useful method for determining the initial events of oxidation of hydrocarbons under extreme conditions and can enhance existing combustion models.

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“…To further study the complexation between 1 and PQ, the formation of the 1·PQ complex was simulated using Gaussian 03 software on the arithmetic method B3LYP/6-31G(D) to obtain an energy-minimized structure (Figure 7) [34]. The modeling computation was run based on the previously reported X-ray crystal structures of PQ and 1,4-benzo-1,5-naphtho [36]crown-10 (BN36C10) [35][36][37].…”

Section: Resultsmentioning

confidence: 99%

Negatively charged crown ethers for binding paraquat in water

Liu

Chen

et al. 2010

Sci. China Chem.

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A water soluble negatively charged fluorescent 1,4-benzo-1,5-naphtho-36-crown-10-based host has been devised and synthesized. As shown by proton NMR, ESI mass spectrometry and UV-vis spectroscopy, it binds paraquat with a 1:1 stoichiometry and an association constant of 4.50 (± 0.02) × 10 3 M 1 in water. Its complexation with paraquat in water was further investigated by fluorescence emission spectroscopy. The results revealed that when paraquat was added to the water solution of the host, the fluorescence emission of the host was quenched by the charge transfer between the crown ether host and paraquat guest. A similar bis-p-phenylene-34-crown-10-based host was synthesized as a contrasting host. Lacking the naphthalene unit, the second host binds paraquat with a 1:1 stoichiometry and a lower association constant, 1.04 (± 0.04)  10 3 M 1 , in water. This demonstrated that the naphthalene unit could not only act as a strong fluorescence group but also improve the - stacking interactions between the host and guest. crown ether, pseudorotaxane, paraquat, fluorescent

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Mechanism of Oxidative Shuttling for [2]Rotaxane in a Stoddart−Heath Molecular Switch: Density Functional Theory Study with Continuum-Solvation Model

Cited by 35 publications

References 50 publications

Designing bistable [2]rotaxanes for molecular electronic devices

Designing bistable [2]rotaxanes for molecular electronic devices

ReaxFF Reactive Force Field for Molecular Dynamics Simulations of Hydrocarbon Oxidation

Negatively charged crown ethers for binding paraquat in water

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