scholarly journals Electric field–induced selective catalysis of single-molecule reaction

2019 ◽  
Vol 5 (6) ◽  
pp. eaaw3072 ◽  
Author(s):  
Xiaoyan Huang ◽  
Chun Tang ◽  
Jieqiong Li ◽  
Li-Chuan Chen ◽  
Jueting Zheng ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Single Molecule ◽  
Alder Reaction ◽  
Diels Alder ◽  
Specific Chemical ◽  
Molecule Reaction ◽  
Aromatization Reaction ◽  
Order Of Magnitude ◽  
Selective Catalysis

Oriented external electric fields (OEEFs) offer a unique chance to tune catalytic selectivity by orienting the alignment of the electric field along the axis of the activated bond for a specific chemical reaction; however, they remain a key experimental challenge. Here, we experimentally and theoretically investigated the OEEF-induced selective catalysis in a two-step cascade reaction of the Diels-Alder addition followed by an aromatization process. Characterized by the mechanically controllable break junction (MCBJ) technique in the nanogap and confirmed by nuclear magnetic resonance (NMR) in bottles, OEEFs are found to selectively catalyze the aromatization reaction by one order of magnitude owing to the alignment of the electric field on the reaction axis. Meanwhile, the Diels-Alder reaction remained unchanged since its reaction axis is orthogonal to the electric fields. This orientation-selective catalytic effect of OEEFs reveals that chemical reactions can be selectively manipulated through the elegant alignment between the electric fields and the reaction axis.

scholarly journals Heterogeneous Intramolecular Electric Field as a Descriptor of Diels-Alder Reactivity

2020 ◽  
Author(s):  
Matthew Hennefarth ◽  
Anastassia N. Alexandrova
Keyword(s):  
Electric Field ◽  
Electron Density ◽  
Electric Fields ◽  
Alder Reaction ◽  
Diels Alder ◽  
Charge Movement ◽  
External Electric Fields ◽  
Topological Features ◽  
Diels Alder Reaction ◽  
Kinetics Of

<div> <div> <div> <p>External electric fields have proven to be an effective tool in catalysis, on par with pressure and temperature, affecting the thermodynamics and kinetics of a reaction. However, fields in molecules are complicated heterogeneous vector objects, and there is no universal recipe for grasping the exact features of these fields that implicate reactivity. Herein, we demonstrate that topological features of the heterogeneous electric field within the reactant state, as well as of the quantum mechanical electron density – a scalar reporter on the field experienced by the system – can be identified as rigorous descriptors of the reactivity to follow. We scrutinize specifically the Diels-Alder reaction. Its 3-D nature and the lack of a singular directionality of charge movement upon barrier crossing makes the effect of the electric field not obvious. We show that the electric field topology around the dienophile double bond, and the associated changes in the topology of the electron density in this bond are predictors of the reaction barrier. They are also the metrics by which to rationalize and predict how the external field would inhibit or enhance the reaction. The findings pave the way toward designing external fields for catalysis, as well as reading the reactivity without an explicit mechanistic interrogation, for a variety of reactions. </p> </div> </div> </div>

scholarly journals Electric field–catalyzed single-molecule Diels-Alder reaction dynamics

2021 ◽  
Vol 7 (4) ◽  
pp. eabf0689
Author(s):  
Chen Yang ◽  
Zitong Liu ◽  
Yanwei Li ◽  
Shuyao Zhou ◽  
Chenxi Lu ◽  
...  
Keyword(s):  
Electric Field ◽  
Single Molecule ◽  
Field Experiments ◽  
Alder Reaction ◽  
Diels Alder ◽  
Charge Transfer Complexes ◽  
Label Free ◽  
Diels Alder Reaction ◽  
Zwitterionic Intermediate

Precise time trajectories and detailed reaction pathways of the Diels-Alder reaction were directly observed using accurate single-molecule detection on an in situ label-free single-molecule electrical detection platform. This study demonstrates the well-accepted concerted mechanism and clarifies the role of charge transfer complexes with endo or exo configurations on the reaction path. An unprecedented stepwise pathway was verified at high temperatures in a high-voltage electric field. Experiments and theoretical results revealed an electric field–catalyzed mechanism that shows the presence of a zwitterionic intermediate with one bond formation and variation of concerted and stepwise reactions by the strength of the electric field, thus establishing a previously unidentified approach for mechanistic control by electric field catalysis.

scholarly journals Heterogeneous Intramolecular Electric Field as a Descriptor of Diels-Alder Reactivity

2020 ◽  
Author(s):  
Matthew Hennefarth ◽  
Anastassia N. Alexandrova
Keyword(s):  
Electric Field ◽  
Electron Density ◽  
Electric Fields ◽  
Alder Reaction ◽  
Diels Alder ◽  
Charge Movement ◽  
External Electric Fields ◽  
Topological Features ◽  
Diels Alder Reaction ◽  
Kinetics Of

<div> <div> <div> <p>External electric fields have proven to be an effective tool in catalysis, on par with pressure and temperature, affecting the thermodynamics and kinetics of a reaction. However, fields in molecules are complicated heterogeneous vector objects, and there is no universal recipe for grasping the exact features of these fields that implicate reactivity. Herein, we demonstrate that topological features of the heterogeneous electric field within the reactant state, as well as of the quantum mechanical electron density – a scalar reporter on the field experienced by the system – can be identified as rigorous descriptors of the reactivity to follow. We scrutinize specifically the Diels-Alder reaction. Its 3-D nature and the lack of a singular directionality of charge movement upon barrier crossing makes the effect of the electric field not obvious. We show that the electric field topology around the dienophile double bond, and the associated changes in the topology of the electron density in this bond are predictors of the reaction barrier. They are also the metrics by which to rationalize and predict how the external field would inhibit or enhance the reaction. The findings pave the way toward designing external fields for catalysis, as well as reading the reactivity without an explicit mechanistic interrogation, for a variety of reactions. </p> </div> </div> </div>

scholarly journals Tuning Single-Molecule Conductance by Controlled Electric Field-Induced trans-to-cis Isomerisation

2021 ◽  
Vol 11 (8) ◽  
pp. 3317
Author(s):  
C.S. Quintans ◽  
Denis Andrienko ◽  
Katrin F. Domke ◽  
Daniel Aravena ◽  
Sangho Koo ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Single Molecule ◽  
Quantum Interference ◽  
Single Molecule Level ◽  
Wet Chemical Synthesis ◽  
Single Molecule Junctions ◽  
Tunnelling Microscopy ◽  
The Difference

External electric fields (EEFs) have proven to be very efficient in catalysing chemical reactions, even those inaccessible via wet-chemical synthesis. At the single-molecule level, oriented EEFs have been successfully used to promote in situ single-molecule reactions in the absence of chemical catalysts. Here, we elucidate the effect of an EEFs on the structure and conductance of a molecular junction. Employing scanning tunnelling microscopy break junction (STM-BJ) experiments, we form and electrically characterize single-molecule junctions of two tetramethyl carotene isomers. Two discrete conductance signatures show up more prominently at low and high applied voltages which are univocally ascribed to the trans and cis isomers of the carotenoid, respectively. The difference in conductance between both cis-/trans- isomers is in concordance with previous predictions considering π-quantum interference due to the presence of a single gauche defect in the trans isomer. Electronic structure calculations suggest that the electric field polarizes the molecule and mixes the excited states. The mixed states have a (spectroscopically) allowed transition and, therefore, can both promote the cis-isomerization of the molecule and participate in electron transport. Our work opens new routes for the in situ control of isomerisation reactions in single-molecule contacts.

scholarly journals Breaching the Axial Limits in Ln(III) Single-Ion Magnets Using External Electric Field

2020 ◽  
Author(s):  
Arup Sarkar ◽  
Rajaraman Gopalan
Keyword(s):  
Electric Field ◽  
External Electric Field ◽  
Barrier Height ◽  
Electric Fields ◽  
Single Molecule ◽  
Information Storage ◽  
Fine Tuning ◽  
Ligand Field ◽  
Nano Technology ◽  
Technology Applications

<i>Single-Molecule Magnets have potential applications in several nano-technology applications including in high-dense information storage devices and realization of this potential application lies in enhancing the barrier height for magnetization reversal (U<sub>eff</sub>). Recent literature examples suggest that the maximum values that one can obtain using a ligand field are already accomplished. Here we have explored using a combination of DFT and ab initio CASSCF calculations, the way to enhance the barrier height using an oriented external electric field for top three Single-ion Magnets ([Dy(Py)<sub>5</sub>(O<sup>t</sup>Bu)<sub>2</sub>]<sup>+</sup> (<b>1</b>) and [Er{N(SiMe<sub>3</sub>)<sub>2</sub>}<sub>3</sub>Cl]<sup>-</sup> (<b>2</b>) and [Dy(Cp<sup>Me3</sup>)Cl] (<b>3</b>)). For the first time our study reveals that, for apt molecules, if appropriate direction and value of electric fields are chosen, the barrier height could be enhanced twice that of the limit set by the ligand field. This novel non-chemical-fine tuning approach to modulate the magnetic anisotropy is expected to yield new generation SIMs.</i>

Electric Field-induced switching among multiple conductance pathways in single-molecule junctions

2021 ◽  
Author(s):  
Tengyang Gao ◽  
Zhichao Pan ◽  
Zhuanyun Cai ◽  
Jueting Zheng ◽  
Chun Tang ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Single Molecule ◽  
Scanning Tunneling Microscope ◽  
Binding Sites ◽  
Scanning Tunneling ◽  
Tunneling Microscope ◽  
Field Increase ◽  
Electric Field Increase ◽  
Single Molecule Junctions

Here, we report the switching among multiple conductance pathways achieved by sliding the scanning tunneling microscope tip among different binding sites under different electric fields. With the electric field increase,...

scholarly journals Resonant collisional shielding of reactive molecules using electric fields

Science ◽  
2020 ◽  
Vol 370 (6522) ◽  
pp. 1324-1327 ◽  
Author(s):  
Kyle Matsuda ◽  
Luigi De Marco ◽  
Jun-Ru Li ◽  
William G. Tobias ◽  
Giacomo Valtolina ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Chemical Reaction ◽  
Reaction Rate ◽  
Reaction Rates ◽  
Dipolar Interactions ◽  
Full Control ◽  
Order Of Magnitude ◽  
Quantum Science ◽  
Chemical Reaction Rates

Full control of molecular interactions, including reactive losses, would open new frontiers in quantum science. We demonstrate extreme tunability of ultracold chemical reaction rates by inducing resonant dipolar interactions by means of an external electric field. We prepared fermionic potassium-rubidium molecules in their first excited rotational state and observed a modulation of the chemical reaction rate by three orders of magnitude as we tuned the electric field strength by a few percent across resonance. In a quasi–two-dimensional geometry, we accurately determined the contributions from the three dominant angular momentum projections of the collisions. Using the resonant features, we shielded the molecules from loss and suppressed the reaction rate by an order of magnitude below the background value, thereby realizing a long-lived sample of polar molecules in large electric fields.

scholarly journals Can electric fields drive chemistry for an aqueous microdroplet?

2022 ◽  
Vol 13 (1) ◽  
Author(s):  
Hongxia Hao ◽  
Itai Leven ◽  
Teresa Head-Gordon
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Reaction Rates ◽  
Droplet Surface ◽  
Surface Reactivity ◽  
Coarse Grained ◽  
Bulk Solution ◽  
Electron Model ◽  
Field Distributions ◽  
Order Of Magnitude

AbstractReaction rates of common organic reactions have been reported to increase by one to six orders of magnitude in aqueous microdroplets compared to bulk solution, but the reasons for the rate acceleration are poorly understood. Using a coarse-grained electron model that describes structural organization and electron densities for water droplets without the expense of ab initio methods, we investigate the electric field distributions at the air-water interface to understand the origin of surface reactivity. We find that electric field alignments along free O–H bonds at the surface are ~16 MV/cm larger on average than that found for O–H bonds in the interior of the water droplet. Furthermore, electric field distributions can be an order of magnitude larger than the average due to non-linear coupling of intramolecular solvent polarization with intermolecular solvent modes which may contribute to even greater surface reactivity for weakening or breaking chemical bonds at the droplet surface.

scholarly journals A Bond Bundle Case Study of Diels-Alder Catalysis Using Oriented Electric Fields

2022 ◽  
Author(s):  
Timothy Wilson ◽  
Mark Eberhart
Keyword(s):  
Electric Field ◽  
Charge Density ◽  
Electric Fields ◽  
Chemical Reactions ◽  
Catalytic Effect ◽  
Reaction Pathway ◽  
Three Dimensional ◽  
Atomic Charge ◽  
Diels Alder

Bond bundles are chemical bonding regions, analogous to Bader atoms, uniquely defined according to the topology of the gradient bundle condensed charge density, itself obtained by a process of infinitesimal partitioning of the three-dimensional charge density into differential zero-flux surface bounded regions. Here we use bond bundle analysis to investigate the response of the charge density to an oriented electric field in general, and the catalytic effect of such a field on Diels-Alder reactions in particular, which in this case is found to catalyze by allowing the transition state valance bond bundle configuration to be achieved earlier along the reaction pathway. Using precise numerical values, we arrive at the conclusion that chemical reactions and electric field catalysis can be understood in terms of intra-atomic charge density redistribution, i.e., that charge shifts within more so than between atoms account for the making and breaking of bonds.

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