Non-covalent interactions and charge transfer in the CO activation by low-valent group 14 complexes.

Context: The CO activation by low-valent group 14 catalysts encompasses the rupture of varied covalent bonds in a single transition state through a concerted pathway. The bond between the central main group atom and the hydride in the complex is elongated to trigger the formation of the C-H bond with CO accompanied by the concomitant formation of the E-O bond between the complex and CO to lead the corresponding formate product. Prior studies have established that besides the apolar nature of CO , its initial interaction with the complex is primarily governed by electrostatic interactions.

Insights into the variations of kinetic and potential energies in a multi-bond reaction: the reaction electronic flux perspective.

Context: The debate over whether kinetic energy (KE) or potential energy (PE) are the fundamental energy components that contribute to forming covalent bonds has been enduring and stimulating over time. However, the supremacy of these energy components in reactions where multiple bonds are simultaneously formed or broken has yet to be explored. In this study, we use the reaction electronic flux (REF), an effective tool for investigating changes in driving electronic activity when bond formation or dissociation occurs in a chemical reaction, to examine the fluctuations in the KE and PE in a multi-bond reaction.

Molecular Environment Modulates CO Liberation from Carboxy-Biotin.

Carboxy-biotin serves as a coenzyme in certain carboxylases, exhibiting the remarkable capability to transfer a carboxy group to specific substrates. This process is made possible by the presence of biotin, a unique molecule that consists of a sulfur-containing tetrahydrothiophene ring fused to a ureido group. It is covalently attached to the enzyme via a flexible linker, allowing for its functionality.

Air- and Water-Stable Heteroleptic Copper (I) Complexes Bearing Bis(indazol-1-yl)methane Ligands: Synthesis, Characterisation, and Computational Studies.

A series of four novel heteroleptic Cu(I) complexes, bearing bis(1-indazol-1-yl)methane analogues as , ligands and DPEPhos as the ligand, were synthesised in high yields under mild conditions and characterised by spectroscopic and spectrometric techniques. In addition, the position of the carboxymethyl substituent in the complexes and its effect on the electrochemical and photophysical behaviour was evaluated. As expected, the homoleptic copper (I) complexes with the , ligands showed air instability.

High-Level Coupled-Cluster Study on Substituent Effects in H Activation by Low-Valent Aluminyl Anions.

The synthesis of novel aluminyl anion complexes has been well exploited in recent years. Moreover, the elucidation of the structure and reactivity of these complexes opens the path toward a new understanding of low-valent aluminum complexes and their chemistry. This work computationally treats the substituent effect on aluminyl anions to discover suitable alternatives for H activation at a high level of theory utilizing coupled-cluster techniques extrapolated to the complete basis set.

Diverse Cooperative Reactivity at a Square Planar Aluminium Complex and Catalytic Reduction of CO.

The use of a sterically demanding pincer ligand to prepare an unusual square planar aluminium complex is reported. Due to the constrained geometry imposed by the ligand scaffold, this four-coordinate aluminium centre remains Lewis acidic and reacts via differing metal-ligand cooperative pathways for activating ketones and CO . It is also a rare example of a single-component aluminium system for the catalytic reduction of CO to a methanol equivalent at room temperature.

Substituent Effects on Aluminyl Anions and Derived Systems: A High-Level Theory.

Aluminyl anions are low-valent aluminum species bearing a lone pair of electrons and a negative charge. These systems have drawn recent synthetic interest for their nucleophilic nature, allowing for the activation of σ-bonds, and have been proposed as a pathway to hydrogen energy storage. In this research, we provide high-level geometries and energies for both the simplest aluminyl anion (AlH) and several substituted derivatives.

Contrasting the Mechanism of H Activation by Monomeric and Potassium-Stabilized Dimeric Al Complexes: Do Potassium Atoms Exert any Cooperative Effect?

Aluminyl anions are low-valent, anionic, and carbenoid aluminum species commonly found stabilized with potassium cations from the reaction of Al-halogen precursors and alkali compounds. These systems are very reactive toward the activation of σ-bonds and in reactions with electrophiles. Various research groups have detected that the potassium atoms play a stabilization role via electrostatic and cation interactions with nearby (aromatic)-carbocyclic rings from both the ligand and from the reaction with unsaturated substrates.

Trapping an unusual pentacoordinate carbon atom in a neutral trialuminum complex.

A neutral trialuminum complex incorporates a pentacoordinate carbon through a methylidene bridge linking the three metal atoms. The rigid electron-deficient Al core stabilizes the hypercoordinate carbon atom resulting in the shortest equatorial Al-C distance reported for such an Al-(μ-CH) unit.

Toward a Neutral Single-Component Amidinate Iodide Aluminum Catalyst for the CO Fixation into Cyclic Carbonates.

A new iodide aluminum complex ({AlI(κ-naphbam)}, ) supported by a tetradentate amidinate ligand derived from a naphthalene-1,8-bisamidine precursor (naphbamH, ) was obtained in quantitative yield via reaction of the corresponding methyl aluminum complex ({AlMe(κ-naphbam)}, ) with 1 equiv of I in CHCl at room temperature. Complexes and were tested and found to be active as catalysts for the cyclic carbonate formation from epoxides at 80 °C and 1 bar of CO pressure. A first series of experiments were carried out with 1.

The Keto-Enol Tautomerism of Biliverdin in Bacteriophytochrome: Could it Explain the Bathochromic Shift in the Pfr Form?.

Phytochromes are ubiquitous photoreceptors found in plants, eukaryotic algae, bacteria and fungi. Particularly, when bacteriophytochrome is irradiated with light, a Z-to-E (photo)isomerization takes place in the biliverdin chromophore as part of the Pr-to-Pfr conversion. This photoisomerization is concomitant with a bathochromic shift in the Q-band.

Theoretical study of glycine amino acid adsorption on graphene oxide.

The non-dissociative and dissociative adsorptions of zwitterionic Gly on graphene oxide (GO) was studied in the framework of DFT using a cluster model approach. In this work, the interaction with an epoxy group of GO basal plane was mainly considered. As a comparison, the non-dissociative and dissociative adsorptions of neutral Gly were also taken into account.

Formation of Formic Acid Derivatives through Activation and Hydroboration of CO by Low-Valent Group 14 (Si, Ge, Sn, Pb) Catalysts.

The chemistry of low-valent main group elements has attracted much attention in the past decade. These species are relevant because they have been able to mimic transition metal behavior in catalytic applications, with decreased material costs and diminished toxicity. In this contribution, we study the LEH catalysts (E = Si(II), Ge(II), Sn(II), and Pb(II); L = [ArNC(Me)CHC(Me)NAr] with Ar = 2,6-iPrCH) for the formation of formic acid derivatives through hydroboration of CO.

Decomposition of the electronic activity in competing [5,6] and [6,6] cycloaddition reactions between C and cyclopentadiene.

Fullerenes, in particular C60, are important molecular entities in many areas, ranging from material science to medicinal chemistry. However, chemical transformations have to be done in order to transform C60 in added-value compounds with increased applicability. The most common procedure corresponds to the classical Diels-Alder cycloaddition reaction.

Reaction Electronic Flux Perspective on the Mechanism of the Zimmerman Di-π-methane Rearrangement.

The reaction electronic flux (REF) offers a powerful tool in the analysis of reaction mechanisms. Noteworthy, the relationship between aromaticity and REF can eventually reveal subtle electronic events associated with reactivity in aromatic systems. In this work, this relationship was studied for the triplet Zimmerman di-π-methane rearrangement.

Radicals derived from acetaldehyde and vinyl alcohol.

Vinyl alcohol and acetaldehyde are isoelectronic products of incomplete butanol combustion. Along with the radicals resulting from the removal of atomic hydrogen or the hydroxyl radical, these species are studied here using ab initio methods as complete as coupled cluster theory with single, double, triple, and perturbative quadruple excitations [CCSDT(Q)], with basis sets as large as cc-pV5Z. The relative energies provided herein are further refined by including corrections for relativistic effects, the frozen core approximation, and the Born-Oppenheimer approximation.

A DFT study of hydrogen and methane activation by B(CF)/P(t-Bu) and Al(CF)/P(t-Bu) frustrated Lewis pairs.

This contribution presents a computational study aimed at understanding factors affecting barriers associated with the activation of the H-H bond in molecular hydrogen and the H-CH bond in methane mediated by intermolecular Frustrated Lewis Pairs (FLPs). The classical phosphine P(t-Bu) Lewis base in conjunction with two Lewis acids, B(CF) and Al(CF), were used as representative models of intermolecular FLPs. DFT calculations were performed using the dispersion corrected ωB97x-D functional, including toluene as a solvent through the PCM-SMD implicit solvent scheme.

Double Gold Activation of 1-Ethynyl-2-(Phenylethynyl)Benzene Toward 5-exo-dig and 6-endo-dig Cyclization Reactions.

In this work, a detailed characterization was carried out of the ring-closure mechanism of EPB (1-ethynyl-2-(phenylethynyl)benzene) toward the 5-exo-dig and 6-endo-dig cyclization reactions, catalyzed by two Au-N-heterocyclic carbene (NHC) moieties. It was found that the 5-exo-dig cyclization takes place with a slightly lower activation barrier and larger exothermicity compared to that of the 6-endo-dig cyclization, in agreement with the available experimental data. A phenomenological partition (structural and electronic) for rate constants computed using transition-state theory and the reaction force analysis was used to shed light into the nature of the activation rate constant.

Adsorption/desorption process of formaldehyde onto iron doped graphene: a theoretical exploration from density functional theory calculations.

The interaction of formaldehyde (HCO) onto Fe-doped graphene (FeG) was studied in detail from density functional theory calculations and electronic structure analyses. Our aim was to obtain insights into the adsorption, desorption and sensing properties of FeG towards HCO, a hazardous organic compound. The adsorption of HCO was shown to be energetically stable onto FeG, with adsorption energies of up to 1.