Origins of complex solvent effects on chemical reactivity and computational tools to investigate them: a review

Varghese, Jithin John; Mushrif, Samir H.

doi:10.1039/c8re00226f

Cited by 149 publications

(151 citation statements)

References 194 publications

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“…functional groups held in specific spatial orientations, or functional group dissections that do not exist). Similarly, the computational prediction of solvent effects remains notoriously difficult . Therefore, for our experimental investigations in solution, we instead sought model systems in which through‐space effects would dominate over those occurring through bonds.…”

Section: Resultsmentioning

confidence: 99%

Quantifying Through‐Space Substituent Effects

et al. 2020

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The description of substituents as electron donating or withdrawing leads to a perceived dominance of through‐bond influences. The situation is compounded by the challenge of separating through‐bond and through‐space contributions. Here, we probe the experimental significance of through‐space substituent effects in molecular interactions and reaction kinetics. Conformational equilibrium constants were transposed onto the Hammett substituent constant scale revealing dominant through‐space substituent effects that cannot be described in classic terms. For example, NO2 groups positioned over a biaryl bond exhibited similar influences as resonant electron donors. Meanwhile, the electro‐enhancing influence of OMe/OH groups could be switched off or inverted by conformational twisting. 267 conformational equilibrium constants measured across eleven solvents were found to be better predictors of reaction kinetics than calculated electrostatic potentials, suggesting utility in other contexts and for benchmarking theoretical solvation models.

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Section: Resultsmentioning

confidence: 99%

Quantifying Through‐Space Substituent Effects

et al. 2020

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“…Some studies have shown that these effects are significant, for example, ORR on the Pt (111) surface and single‐atom catalyst . First‐principles molecular dynamics simulations with explicit water molecules are often used to obtain the water‐adsorbate interactions and/or the reaction barriers . However, this approach often suffers from high computational cost and large statistical error bar which can be comparable to the interaction energetics .…”

Section: Conclusion and Perspectivementioning

confidence: 99%

The electronic structure underlying electrocatalysis of two‐dimensional materials

Zhao

Shi

et al. 2019

WIREs Comput Mol Sci

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The understanding and development of advanced electrochemical catalysts have attracted intensive studies and achieved tremendous progress in the past decades. Two‐dimensional (2D) materials, such as doped graphene and atomically‐thin transition metal compounds, have shown great promise as electrocatalysts for various renewable energy conversion and storage reactions. Their further developments require improved understanding of the catalytic mechanisms at atomic level. Currently, most of the understandings are based on the formation free energies of the intermediates, which are determined by their binding strengths with the catalyst, usually calculated from density functional theory (DFT). These energies/binding strengths have been used as descriptor to describe the activity of many catalysts. However, it remains less explored why different catalysts have different binding strengths and what are the underlying factors controlling them, requiring studies going beyond atomic level to electronic level. This review aims to provide such links, focusing on 2D electrocatalysts for hydrogen evolution reaction (HER), oxygen reduction reaction/oxygen evolution reaction (ORR/OER), CO2 reduction reaction (CO2R) and nitrogen reduction reaction (NRR). We also discuss some of the significant issues that need to be addressed in DFT calculations, including the effects of varying charge and fixed potential of the catalyst, the passivation of active sites, and the solvation effects. This article is categorized under: Structure and Mechanism > Reaction Mechanisms and Catalysis Structure and Mechanism > Computational Materials Science

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“…Whilst the Kamlet and Taft parameters provide a good general and qualitative description for solvent effects, experimental measurements able to reveal physico‐chemical insights at a molecular level in solvent‐based homogeneous catalytic processes have remained overlooked. Computational tools can be used to explain solvent effects in catalysis . Experimental tools are however essential and, among the potential techniques for experimental studies of solvent effects in homogeneous catalysis, nuclear magnetic resonance (NMR) measurements of diffusion coefficients represent a powerful, non‐invasive method for studying interactions in homogeneously catalysed chemical reactions.…”

Section: Introductionmentioning

confidence: 99%

Solvent Effects in the Homogeneous Catalytic Reduction of Propionaldehyde with Aluminium Isopropoxide Catalyst: New Insights from PFG NMR and NMR Relaxation Studies

et al. 2020

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Solvent effects in homogeneous catalysis are known to affect catalytic activity. Whilst these effects are often described using qualitative features, such as Kamlet‐Taft parameters, experimental tools able to quantify and reveal in more depth such effects have remained unexplored. In this work, PFG NMR diffusion and T1 relaxation measurements have been carried out to probe solvent effects in the homogeneous catalytic reduction of propionaldehyde to 1‐propanol in the presence of aluminium isopropoxide catalyst. Using data on diffusion coefficients it was possible to estimate trends in aggregation of different solvents. The results show that solvents with a high hydrogen‐bond accepting ability, such as ethers, tend to form larger aggregates, which slow down the molecular dynamics of aldehyde molecules, as also suggested by T1 measurements, and preventing their access to the catalytic sites, which results in the observed decrease of catalytic activity. Conversely, weakly interacting solvents, such as alkanes, do not lead to the formation of such aggregates, hence allowing easy access of the aldehyde molecules to the catalytic sites, resulting in higher catalytic activity. The work reported here is a clear example on how combining traditional catalyst screening in homogeneous catalysis with NMR diffusion and relaxation time measurements can lead to new physico‐chemical insights into such systems by providing data able to quantify aggregation phenomena and molecular dynamics.

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Origins of complex solvent effects on chemical reactivity and computational tools to investigate them: a review

Abstract: Origins of solvent-induced enhancement in catalytic reactivity and product selectivity are discussed with computational methods to study them.

Cited by 149 publications

References 194 publications

Quantifying Through‐Space Substituent Effects

Quantifying Through‐Space Substituent Effects

The electronic structure underlying electrocatalysis of two‐dimensional materials

Solvent Effects in the Homogeneous Catalytic Reduction of Propionaldehyde with Aluminium Isopropoxide Catalyst: New Insights from PFG NMR and NMR Relaxation Studies

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