A new extension of the polarizable continuum model: Toward a quantum chemical description of chemical reactions at extreme high pressure

Cammi, Roberto

doi:10.1002/jcc.24206

Cited by 76 publications

(128 citation statements)

References 59 publications

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“…The attractiveness of defining radii from the electron density is that a) the electron density is, at least in principle, an experimental observable, and b) it is the electron density at the outermost regions of a system that determines Pauli/exchange/same‐spin repulsions, or attractive bonding interactions, with a chemical surrounding. We are also interested in a consistent density‐dependent set of radii, for the systematic introduction of pressure on small systems by the XP‐PCM method, which we will report on in the near future. Our aim there is to provide a consistent account of electronegativity under compression.…”

Section: Introductionmentioning

confidence: 99%

Atomic and Ionic Radii of Elements 1–96

Rahm

Hoffmann

Ashcroft

2016

Chemistry A European J

315

219

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Atomic and cationic radii have been calculated for the first 96 elements, together with selected anionic radii. The metric adopted is the average distance from the nucleus where the electron density falls to 0.001 electrons per bohr(3) , following earlier work by Boyd. Our radii are derived using relativistic all-electron density functional theory calculations, close to the basis set limit. They offer a systematic quantitative measure of the sizes of non-interacting atoms, commonly invoked in the rationalization of chemical bonding, structure, and different properties. Remarkably, the atomic radii as defined in this way correlate well with van der Waals radii derived from crystal structures. A rationalization for trends and exceptions in those correlations is provided.

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Section: Introductionmentioning

confidence: 99%

Atomic and Ionic Radii of Elements 1–96

Rahm

Hoffmann

Ashcroft

2016

Chemistry A European J

315

219

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“…Them ajor challenge in the theoretical study of high pressure organic reactions in solution is to properly handle the effect of both solvent and pressure.Essentially none of the existing programs specialized in molecular calculations (e.g., Gaussian, GAMESS) takes pressure as ap arameter in the calculation of electronic energy.H owever,r ecent development of the XP-PCM (standing for "extreme pressure polarizable continuum model") method [33] by one of us successfully introduces the pressure variable into the calculation of solvated molecular systems by constraining the accessible space of the moleculeselectrons with ad ensity-dependent repulsive potential around the molecule. Figure 4sketches the essence of XP-PCM method.…”

Section: The Xp-pcm Methods For Studying Reactions Under Pressurementioning

confidence: 99%

“…We will follow up in the next section with ac ase study,u npacking this method numerically.R eaders interested in the detailed formulation of XP-PCM are referred to the Supporting Information (SI) or the original methodology paper for details. [33] As an extension of the basic polarizable continuum model (PCM) [34] that deals with solvation energy of molecules at standard pressure,t he XP-PCM method aims to introduce explicitly the effect of the pressure (higher than 1GPa = 10 kbar) into quantum chemical calculations.I nt he PCM model (Figure 4, left), the target molecular system (the solute) is dissolved in an external medium (the solvent). Theexternal medium is considered as ac ontinuum material distribution, with uniform dielectric permittivity e and electron density 1.…”

Section: The Xp-pcm Methods For Studying Reactions Under Pressurementioning

confidence: 99%

The Effect of Pressure on Organic Reactions in Fluids—a New Theoretical Perspective

2017

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This Review brings a new perspective to the study of chemical reactions in compressed fluid media. We begin by reviewing the substantial insight gained from more than 50 years of experimental studies on organic reactions in solution under pressure. These led to a proper estimation of the critical roles of volume of activation (Δ≠V) and reaction volume (ΔV) in understanding pressure effect on rates and equilibria of organic reactions. A recently developed computational method, the XP‐PCM (extreme pressure polarizable continuum model) method, capable of carrying out quantum mechanical calculations of reaction pathways of molecules under pressure, is introduced. A case study of the Diels–Alder cycloaddition of cyclopentadiene with ethylene serves, in pedagogical detail, to describe the methodology. We then apply the XP‐PCM method to a selection of other pericyclic reactions, including the parent Diels–Alder cycloaddition of butadiene with ethylene, electrocyclic ring‐opening of cyclobutene, electrocyclic ring‐closing of Z‐hexatriene, the [1,5]‐H shift in Z‐pentadiene, and the Cope rearrangement. These serve as examples of some of the most common combinations of Δ≠V and ΔV. Interesting phenomena such as a shift in a transition state along a reaction coordinate, a switch of rate‐determining step, and the possible turning of a transition state into a stable minimum are revealed by the calculations. A reaction volume profile, the change in the volume of the reacting molecules as the reaction proceeds, emerges as being useful.

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“…[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. 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.…”

mentioning

confidence: 99%

“…[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. [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.…”

mentioning

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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A new extension of the polarizable continuum model: Toward a quantum chemical description of chemical reactions at extreme high pressure

Cited by 76 publications

References 59 publications

Atomic and Ionic Radii of Elements 1–96

Atomic and Ionic Radii of Elements 1–96

The Effect of Pressure on Organic Reactions in Fluids—a New Theoretical Perspective

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

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