Advances in Quantum Mechanochemistry: Electronic Structure Methods and Force Analysis

Stauch, Tim; Dreuw, Andreas

doi:10.1021/acs.chemrev.6b00458

Cited by 177 publications

(220 citation statements)

References 436 publications

(792 reference statements)

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“…The design of stress‐responsive and mechanochromic polymers has received a tremendous amount of attention during the past few years ,. Recent advances in the incorporation of force‐responsive units, so‐called mechanophores, into the backbones of polymers have allowed the synthesis of a prototypical molecular force sensor, in which the mechanically induced isomerization of spiropyran to merocyanin is accompanied by a color change of the material from yellow to red .…”

Section: Methodsmentioning

confidence: 99%

Mechanical Switching of Aromaticity and Homoaromaticity in Molecular Optical Force Sensors for Polymers

Stauch

2018

Chemistry A European J

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The sensing of mechanical stress in polymers is indispensable for investigating the origin and propagation of cracks that lead to material failure and for designing mechanically responsive polymers. Here the unique approaches of using the force-induced switching of aromaticity and homoaromaticity in molecular optical force sensors for the real-time measurement of mechanical forces acting in stretched polymers are suggested. The mechanical switching of aromaticity in Dewar benzene is an irreversible event, whereas the degree of π-orbital overlap in homoaromatic compounds like homotropylium can be adjusted progressively over a wide range of forces. Using computational methods, it is demonstrated that both approaches lead to significant changes in the visible part of the UV/Vis spectra of the force sensors upon application of weak forces (pN-nN). Polymers that incorporate such molecular force sensors therefore change their color well before material failure occurs.

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Section: Methodsmentioning

confidence: 99%

Mechanical Switching of Aromaticity and Homoaromaticity in Molecular Optical Force Sensors for Polymers

Stauch

2018

Chemistry A European J

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“…The force that needs to be applied to meet the BBP on the corresponding effective PES is named the critical force, f c . The kind of points is also discussed elsewhere . An algorithm to locate optimal BBPs has been recently proposed .…”

Section: Application Of Newton Trajectoriesmentioning

confidence: 99%

“…The study of how external mechanical forces change the potential energy surfaces (PES) of molecular systems is of highest relevance in the context of mechanochemistry because this can lead to a better understanding of the molecular level of the mechanisms by which external forces control chemical processes. In the last years, the chemical response of single molecules, polymers, covalent inorganic crystals, metals, molecular solids, and so forth when subjected to mechanical forces has motivated experimental and theoretical researches . Chemical reactions can be thought of in terms of their “landscapes”—multidimensional PESes with a dimension much higher than three dimensions of our usual space—that map the saddle‐pathways and valleys of the potential energy as molecules interact .…”

Section: Introductionmentioning

confidence: 99%

Toward a theory of mechanochemistry: Simple models from the very beginnings

Quapp

Bofill

Ribas‐Ariño

2018

Int J of Quantum Chemistry

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A core idea in the context of mechanochemistry is that applying an external tensile force along a reaction coordinate should enhance the chemical reaction of interest. Here, we analyze perturbed generic molecular structures: schematic models of triatomics, ABC, and tetraatomics, AABB. They are used to demonstrate that pulling does usually not use the “reaction coordinate,” but opens new reaction pathways. Within development of these models we use the concept of Newton trajectories for a theory of mechanochemistry. However, we find cases where the theory of Newton trajectories is not applicable. For all cases, we define the curve of force‐displaced stationary points, and we discuss the importance of barrier breakdown points and valley‐ridge inflection points. The examples use Morse potentials for bonds and simple angle functions and are demonstrated by assumed real values for the potential parameters. On the basis of the systematic study of some generic models we explain a set of already observed experimental mechanochemical phenomena in specific molecular systems and we apply the results to the strength of chemical bonds.

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“…[9] Using effective nuclear forces scaled by their distances from the molecular centroid we here model spin crossover in octahedral metal-ligand complexes as a function of hydrostatic pressure. [21,22] Spatially varying nuclear forces have been described in a previous work as a generalized force-modified potential energy surface (G-FMPES). Finer quantum chemical effects at play in the process involve a change in the covalent binding energy, Pauli repulsion, and charge transfer as a function of pressure, as demonstrated with an Energy Decomposition Analysis (EDA) [11] scheme.…”

mentioning

confidence: 99%

“…[13][14][15] These techniques quantify the change in the molecular PES under external stresses and the resulting changes in observables. [21,22] Spatially varying nuclear forces have been described in a previous work as a generalized force-modified potential energy surface (G-FMPES). [21,22] Spatially varying nuclear forces have been described in a previous work as a generalized force-modified potential energy surface (G-FMPES).…”

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confidence: 99%

Quantum Chemical Modeling of Pressure‐Induced Spin Crossover in Octahedral Metal‐Ligand Complexes

2019

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Spin state switching on external stimuli is a phenomenon with wide applicability, ranging from molecular electronics to gas activation in nanoporous frameworks. Here, we model the spin crossover as a function of the hydrostatic pressure in octahedrally coordinated transition metal centers by applying a field of effective nuclear forces that compress the molecule towards its centroid. For spin crossover in first-row transition metals coordinated by hydrogen, nitrogen, and carbon monoxide, we find the pressure required for spin transition to be a function of the ligand position in the spectrochemical sequence. While pressures on the order of 1 GPa are required to flip spins in homogeneously ligated octahedral sites, we demonstrate a fivefold decrease in spin transition pressure for the archetypal strong field ligand carbon monoxide in octahedrally coordinated Fe 2 + in [Fe(II)(NH 3 ) 5 CO] 2 + .Pressure-induced spin-flips of transition metal sites involve changes in Coulomb energy, closed shell repulsions, covalent bonding energy and crystal field energy. [1,2] Using the computational Extreme-Pressure PCM (XP-PCM) protocol, [3][4][5] it has been shown that high pressures cause drastic electronic rearrangements, causing first row transition metals with electronic configurations d n (4 � n � 8) to favor low spin configurations at high pressures. [6] In a metal-organic framework (MOF) with exposed Fe(II) sites, a distinct step as a function of atmospheric pressure has been observed in the adsorption isotherm of carbon monoxide, for which a cooperative spin-transition mechanism involving interacting iron centers in the MOF on introduction of the strong-field ligand carbon monoxide has been proposed. [7] In general, the use of MOFs in the separation of industrially relevant gases like hydrogen, nitrogen and carbon monoxide holds a lot of promise, due to the large surface areas, the thermal stability and the adjustability of various parameters of the MOFs. [8] The smallest building block of spin crossover systems is often an octahedrally coordinated transition metal center with its 3d orbitals split by the ligand field environment. Spin-flip at high pressures can be attributed to the increase in splitting of the 3d levels at the metal site such that the potential energy required to maintain a high spin configuration surpasses the spin pairing energy. [9] Using effective nuclear forces scaled by their distances from the molecular centroid we here model spin crossover in octahedral metal-ligand complexes as a function of hydrostatic pressure. We find the pressure required for spin transition to be a function of ligand position in the spectrochemical sequence [10] and demonstrate that the spin transition pressure can be tuned by an adequate choice of the ligand field. Finer quantum chemical effects at play in the process involve a change in the covalent binding energy, Pauli repulsion, and charge transfer as a function of pressure, as demonstrated with an Energy Decomposition Analysis (EDA) [11] scheme.Any external force on...

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Advances in Quantum Mechanochemistry: Electronic Structure Methods and Force Analysis

Cited by 177 publications

References 436 publications

Mechanical Switching of Aromaticity and Homoaromaticity in Molecular Optical Force Sensors for Polymers

Mechanical Switching of Aromaticity and Homoaromaticity in Molecular Optical Force Sensors for Polymers

Toward a theory of mechanochemistry: Simple models from the very beginnings

Quantum Chemical Modeling of Pressure‐Induced Spin Crossover in Octahedral Metal‐Ligand Complexes

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