Structural and energetic properties of cluster models of anatase-supported single late transition metal atoms: a density functional theory benchmark study.

Context: Single-atom catalytic systems constitute an intriguing research topic due to their inherently different chemical behavior as compared to classic heterogeneous catalysts. In this study, cluster systems representing single late transition metal atoms adsorbed on anatase were constructed starting from previously generated periodic models and subjected to a density functional theory (DFT) benchmark study. The ability of different density functional approximations representing all rungs of the Jacob's Ladder classification to accurately describe bond lengths and adsorption energies was assessed for these clusters with the aim of revealing the functional that allows to retain the structural characteristics of the initial periodic system, while also delivering reliable energetics.

The electrophilic aromatic bromination of benzenes: mechanistic and regioselective insights from density functional theory.

The HBr-assisted electrophilic aromatic bromination of benzene, anisole and nitrobenzene was investigated using static DFT calculations in gas phase and implicit apolar (CCl4) and polar (acetonitrile) solvent models at the ωB97X-D/cc-pVTZ level of theory. The reaction profiles corresponding to either a direct substitution reaction or an addition-elimination process were constructed and insight into the preferred regioselectivity was provided using a combination of conceptual DFT reactivity indices, aromaticity indices, Wiberg bond indices and the non-covalent interaction index. Our results show that under the considered reaction conditions the bromination reaction preferentially occurs through an addition-elimination mechanism and without formation of a stable charged Wheland intermediate.

Understanding the Reactivity of Supported Late Transition Metals on a Bare Anatase (101) Surface: A Periodic Conceptual DFT Investigation.

The rapidly growing interest for new heterogeneous catalytic systems providing high atomic efficiency along with high stability and reactivity triggered an impressive progress in the field of single-atom catalysis. Nevertheless, unravelling the factors governing the interaction strength between the support and the adsorbed metal atoms remains a major challenge. Based on periodic density functional theory (DFT) calculations, this paper provides insight into the adsorption of single late transition metals on a defect-free anatase surface.

Synergistic Effects in the Activity of Nano-Transition-Metal Clusters Pt M (M=Ir, Ru or Rh) for NO Dissociation.

The dissociation of environmentally hazardous NO through dissociative adsorption on metallic clusters supported by oxides, is receiving growing attention. Building on previous research on monometallic M clusters [The Journal of Physical Chemistry C 2019, 123 (33), 20314-20318], this work considers bimetallic Pt M (M=Rh, Ru or Ir) clusters. The adsorption energy and activation energy of NO dissociation on the clusters have been calculated in vacuum using Kohn-Sham DFT, while their trends were rationalized using reactivity indices such as molecular electrostatic potential and global Fermi softness.

Reactivity of Single Transition Metal Atoms on a Hydroxylated Amorphous Silica Surface: A Periodic Conceptual DFT Investigation.

The drive to develop maximal atom-efficient catalysts coupled to the continuous striving for more sustainable reactions has led to an ever-increasing interest in single-atom catalysis. Based on a periodic conceptual density functional theory (cDFT) approach, fundamental insights into the reactivity and adsorption of single late transition metal atoms supported on a fully hydroxylated amorphous silica surface have been acquired. In particular, this investigation revealed that the influence of van der Waals dispersion forces is especially significant for a silver (98 %) or gold (78 %) atom, whereas the oxophilicity of the Group 8-10 transition metals plays a major role in the interaction strength of these atoms on the irreducible SiO support.

Synthesis and Reactivity of Spirocarbocycles as Scaffolds for Nucleoside Analogues.

A novel class of substituted spiro[3.4]octanes can be accessed via a [2 + 2]-cycloaddition of dichloroketene on a readily prepared -methylene cyclopentane building block. This reaction sequence was found to be robust on a multigram scale and afforded a central spirocyclobutanone scaffold for carbocyclic nucleosides.

Stereoselective Reductions of 3-Substituted Cyclobutanones: A Comparison between Experiment and Theory.

The stereoselective reduction of carbonyls is of key importance in the total synthesis of natural products and in medicinal chemistry. Nevertheless, models for rationalizing the stereoselectivity of the hydride reductions of cyclobutanones toward cyclobutanols are largely lacking, unlike cyclohexanone reductions. In order to elucidate the factors that control the stereoselectivity of these reductions, we have investigated the effect of the reaction temperature, solvent, substituent, and type of reducing agent using a synergistic experimental-computational approach.

Performance of Electronic Structure Methods for the Description of Hückel-Möbius Interconversions in Extended π-Systems.

Expanded porphyrins provide a versatile route to molecular switching devices due to their ability to shift between several π-conjugation topologies encoding distinct properties. DFT remains the workhorse for modeling such extended macrocycles, when taking into account their size and huge conformational flexibility. Nevertheless, the stability of Hückel and Möbius conformers depends on a complex interplay of different factors, such as hydrogen bonding, π···π stacking, steric effects, ring strain, and electron delocalization.

Organogermanium(II) Hydrides as a Source of Highly Soluble LiH.

The reactions of monomeric C,N-chelated organogermanium(II) hydride L(H)Ge⋅BH with organolithium salts RLi yielded lithium hydrogermanatoborates (Li(THF) {BH [L(H)GeR]}) . Compound (Li(THF) {BH [L(H)GePh]}) was used as a source of LiH for the reduction of organic C=O or C=N bonds in nonpolar solvents accompanied by the elimination of a neutral complex L(Ph)Ge⋅BH . The interaction of (Li(THF) {BH [L(H)GePh]}) with the polar C=O bond was further investigated by computational studies revealing a plausible geometry of a pre-reactive intermediate.

A Benchmark of Density Functional Approximations For Thermochemistry and Kinetics of Hydride Reductions of Cyclohexanones.

The performance of density functionals and wavefunction methods for describing the thermodynamics and kinetics of hydride reductions of 2-substituted cyclohexanones has been evaluated for the first time. A variety of exchange correlation functionals ranging from generalized gradient approximations to double hybrids have been tested and their performance to describe the facial selectivity of hydride reductions of cyclohexanones has been carefully assessed relative to the CCSD(T) method. Among the tested methods, an approach in which single-point energy calculations using the double hybrid B2PLYP-D3 functional on ωB97X-D optimized geometries provides the most accurate transition state energies for these kinetically-controlled reactions.

Aromatic sulfonation with sulfur trioxide: mechanism and kinetic model.

Electrophilic aromatic sulfonation of benzene with sulfur trioxide is studied with molecular dynamics simulations in gas phase, and in explicit noncomplexing (CClF) and complexing (CHNO) solvent models. We investigate different possible reaction pathways, the number of SO molecules participating in the reaction, and the influence of the solvent. Our simulations confirm the existence of a low-energy concerted pathway with formation of a cyclic transition state with two SO molecules.