Selective conversion of methane to methanol facilitated by molecular metal-methoxy complexes a self-correcting chemical cycle.

The controlled oxidation of methane to methanol has been an area of intense research over the past decades. Despite the efforts, the identification of an efficient catalyst with high selectivity is still elusive. Here we propose a thoroughly different strategy employing catalysts containing a metal methoxy unit.

A fresh perspective on metal ammonia molecular complexes and expanded metals: opportunities in catalysis and quantum information.

Recent advances in our comprehension of the electronic structure of metal ammonia complexes have opened avenues for novel materials with diffuse electrons. These complexes in their ground state can host peripheral "Rydberg" electrons which populate a hydrogenic-type shell model imitating atoms. Aggregates of such complexes form the so-called expanded or liquid metals.

Transition metal oxide complexes as molecular catalysts for selective methane to methanol transformation: any prospects or time to retire?

Transition metal oxides have been extensively used in the literature for the conversion of methane to methanol. Despite the progress made over the past decades, no method with satisfactory performance or economic viability has been detected. The main bottleneck is that the produced methanol oxidizes further due to its weaker C-H bond than that of methane.

[FeS] cubane in sulfite reductases: new insights into bonding properties and reactivity.

The dissimilatory sulfite reductase enzyme has very characteristic active site where the substrate binds to an iron site, ligated by a siroheme macrocycle and a thiol directly connected to a [FeS] cluster. This arrangement gives the enzyme remarkable efficiency in reducing sulfite and nitrite all the way to hydrogen sulfide and ammonia. For the first time we present a theoretical study where substrate binding modalities and activation are elucidated using active site models containing proton supply side chains and the [FeS] cluster.

Impact of Graphene Quantum Dot Edge Morphologies on Their Optical Properties.

The optoelectronic properties of functionalized graphene quantum dots (GQDs) have been explored by simulating electronic structure of three different shapes of GQDs containing exclusively zigzag or armchair edges in both pristine and functionalized forms. Absorption spectra and transition densities for the low-lying excited states are evaluated by using time-dependent density functional theory and compared for different functionalization species. The functionalization position dictates the optical properties of square GQDs, where isomers with CH in the intermediate positions (excluding corner and center positions) have higher electronic transition energies and exciton delocalization than other isomers.

Electronic Structure of RhO, Its Ammoniated Complexes (NH)RhO, and Mechanistic Exploration of CH Activation by Them.

High-level electronic structure calculations are initially performed to investigate the electronic structure of RhO. The construction of potential energy curves for the ground and low-lying excited states allowed the calculation of spectroscopic constants, including harmonic and anharmonic vibrational frequencies, bond lengths, spin-orbit constants, and excitation energies. The equilibrium electronic configurations were used for the interpretation of the chemical bonding.

Scandium in Neutral and Positively Charged Ammonia Complexes: Balancing between Sc and Sc.

High-level quantum chemical approaches are performed to study the stability and electronic structure of tri-, di-, monocationic, and neutral scandium ammonia complexes. The calculated binding energies of all Sc(NH) complexes reveal the higher stability of hexa- and octacoordinated systems. The ground states of Sc(NH) and Sc(NH) have a Sc(3d) center, while there are two competitive electronic states for Sc(NH) with a Sc(3d) or a Sc center.

Methane to Methanol Conversion Facilitated by Transition-Metal Methyl and Methoxy Units: The Cases of FeCH and FeOCH.

The conversion of methane to methanol (MTM) catalyzed by FeOCH and FeCH is investigated by means of multireference configuration interaction (MRCI), single-reference coupled clusters (CC), and density functional theory (DFT) approaches. Our dual purpose is the assessment of the applied methodologies and the performance of the proposed catalytic cycle, which involves both of the titled units. The investigated cycle aims to bypass the limitations of metal-oxide catalysts and offers an alternative promising method for efficient MTM transformation.

Ligand field effects on the ground and excited states of reactive FeO species.

High-valent Fe(iv)-oxo species have been found to be key oxidizing intermediates in the mechanisms of mononuclear iron heme and non-heme enzymes that can functionalize strong C-H bonds. Biomimetic Fe(iv)-oxo molecular complexes have been successfully synthesized and characterized, but their catalytic reactivity is typically lower than that of the enzymatic analogues. The C-H activation step proceeds through two competitive mechanisms, named σ- and π-channels.

Aufbau Rules for Solvated Electron Precursors: Be(NH) Complexes and Beyond.

Tetra-amino beryllium complexes and ions, Be(NH), have a tetrahedral Be(NH) core with one, two, or three outer electrons orbiting its periphery. Our calculations reveal a new class of molecular entities, solvated electron precursors, with Aufbau rules (1s, 1p, 1d, 2s, 1f, 2p, 2d) that differ from their familiar hydrogenic counterparts and resemble those of jellium or nuclear-shell models. The core's radial electrostatic potential suffices to reproduce the chief features of the ab initio results.

The role of O(D) in the oxidation mechanism of ethylene by iodosobenzene and other hypervalent molecules.

The role of the first excited state of oxygen (D) is proven essential for the description of terminal iodine-oxygen chemical bonds. The description of the I-O bond as a dative one from iodine to O(D) provides a simple and accurate picture which explains the oxidation properties of iodosobenzene and similar in nature molecules.