Accurate Calculation of Isomerization and Conformational Energies of Larger Molecules Using Explicitly Correlated Local Coupled Cluster Methods in Molpro and ORCA.

An overview of the approximations in the explicitly correlated local coupled cluster methods PNO-LCCSD(T)-F12 in Molpro and DLPNO-CCSD(T) in ORCA is given. Options to select the domains of projected atomic orbitals (PAOs), pair natural orbitals (PNOs), and triples natural orbitals (TNOs) in both programs are described and compared in detail. The two programs are applied to compute isomerization and conformational energies of the ISOL24 and ACONFL test sets, where the former is part of the GMTKN55 benchmark suite.

Solvent Dependency of Catalyst-Substrate Aggregation Through π-π Stacking in Photoredox Catalysis.

Assemblies of photoredox catalysts and their target substrates prior to photoexcitation is a phenomenon naïvely overlooked by the majority of synthetic chemists, but can have profound influences on reactivity and selectivity in photocatalytic reactions. In this study, we determine the aggregation states of triarylamine radical cationic photocatalysts with various target arene substrates in different solvents by specifically parameterized polarizable molecular dynamics simulations. A π-stacking interaction previously implicated by more expensive, less-representative quantum calculations is confirmed.

Dispersion Energy-Stabilized Boron and Phosphorus Lewis Pairs.

An isostructural series of boron/phosphorus Lewis pairs was systematically investigated. The association constants of the Lewis pairs were determined at variable temperatures, enabling the extraction of thermodynamic parameters. The stabilization of the Lewis adduct increased with increasing size of the dispersion energy donor groups, although the donor and acceptor properties of the Lewis pairs remained largely unchanged.

High-throughput screening of spin states for transition metal complexes with spin-polarized extended tight-binding methods.

The semiempirical GFNn-xTB ( ) tight-binding methods are extended with a spin-dependent energy term (spin-polarization), enabling the fast and efficient screening of different spin states for transition metal complexes. While GFNn-xTB methods inherently can not differentiate properly between high-spin (HS) and low-spin (LS) states, this shortcoming is corrected with the presented methods termed spGFNn-xTB. The performance of spGFNn-xTB methods for spin state energy splittings is evaluated on a newly compiled benchmark set of 90 complexes (27 HS and 63 LS complexes) containing 3d, 4d, and 5d transition metals (termed TM90S) employing DFT references at the TPSSh-D4/def2-QZVPP level of theory.

ONIOM meets : efficient, accurate, and robust multi-layer simulations across the periodic table.

The computational treatment of large molecular structures is of increasing interest in fields of modern chemistry. Accordingly, efficient quantum chemical approaches are needed to perform sophisticated investigations on such systems. This engaged the development of the well-established "Our own N-layered integrated molecular orbital and molecular mechanics" (ONIOM) multi-layer scheme [L.

On the Rich Chemistry of Pseudo-Protic Ionic Liquid Electrolytes.

Mixing weak acids and bases can produce highly complicated binary mixtures, called pseudo-protic ionic liquids, in which a complex network of effects determines the physicochemical properties that are currently impossible to predict. In this joint computational-experimental study, we investigated 1-methylimidazole-acetic acid mixtures through the whole concentration range. Effects of the varying ionization and excess of either components on the properties, such as density, diffusion coefficients, and overall hydrogen bonding structure were uncovered.

Selective Chirality Transfer to the Bis(trifluoromethylsulfonyl)imide Anion of an Ionic Liquid.

Chirality transfer from the chiral molecule (R)-1,2-propylene oxide to the achiral anion of the 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquid is observed. The chiral probe selectively affects one part of the binary ionic liquid, i. e.

Proton-transfer rate constants for the determination of organic indoor air pollutants by online mass spectrometry.

Proton transfer reaction mass spectrometry (PTR-MS) has become an indispensable analytical tool for indoor related sciences. With high-resolution techniques not only is the online monitoring of the selected ions in the gas phase possible, but also, with some limitations, the identification of substance mixtures without chromatographic separation. The quantification is carried out with the help of kinetic laws, which require knowledge of the conditions in the reaction chamber, the reduced ion moblilities and the reaction rate constant under these conditions.

HOpen - Guest Editorial.

This special collection presents original research articles and reviews that are connected to the multifaceted and rich chemistry of water. These works serve as an illustration of how, despite its apparent simplicity and ubiquity, water continues to be at the center of scientific exploration from a wide range of perspectives and employing the toolbox of modern-day chemistry.

Computation of CCSD(T)-Quality NMR Chemical Shifts via Δ-Machine Learning from DFT.

NMR spectroscopy undoubtedly plays a central role in determining molecular structures across different chemical disciplines, and the accurate computational prediction of NMR parameters is highly desirable. In this work, a new Δ-machine learning approach is presented to correct DFT-computed NMR chemical shifts using input features from the calculation and in addition highly accurate reference data at the CCSD(T)/pcSseg-2 level of theory with a basis set extrapolation scheme. The model is trained on a data set containing 1000 optimized and geometrically distorted structures of small organic molecules comprising most elements of the first three periods and containing data for 7090 H and 4230 C NMR chemical shifts.

Brominated [20]silafulleranes: pushing the limits of steric loading.

Starting from the perhydrogenated silafullerane [BuN][Cl@Si(SiH)H], treatment with BBr leads to partially and exhaustively brominated clusters, [BuN][Cl@Si(SiBrH)Br] (120 eq. BBr, room temperature, 30 min) and [BuN][Cl@Si(SiBr)Br] (300 eq. BBr, 130 °C, 3 d).

Regioselective Derivatization of Silylated [20]Silafulleranes.

Silafulleranes with endohedral Cl ions are a unique, scarcely explored class of structurally well-defined silicon clusters and host-guest complexes. Herein, we report regioselective derivatization reactions on the siladodecahedrane [BuN][Cl@Si(SiCl)Cl] ([BuN][]), which has its cluster surface decorated with 12 SiCl and 8 Cl substituents in perfect symmetry. The room-temperature reaction of [BuN][] with excess BuAlH in -difluorobenzene (DFB) furnishes perhydrogenated [BuN][Cl@Si(SiH)H] ([BuN][]) in 50% yield; the non-pyrophoric [] is the largest structurally authenticated (by X-ray diffraction) hydridosilane known to date.

Discrimination of the Enantiotopic Faces of Structurally Unbiased Carbenium Ions Employing a Cyclohexadiene-Based Chiral Hydride Source.

An enantioselective reduction of simple carbenium ions with cyclohexadienes containing a hydridic C-H bond at an asymmetrically substituted carbon atom is disclosed. The net reaction is a transfer hydrogenation of alkenes (styrenes) only employing chiral cyclohexadienes as dihydrogen surrogates. The trityl cation is used to initiate a Brønsted acid-promoted process, in which a delicate intermolecular capture of a carbenium-ion intermediate by the aforementioned chiral hydride source is enantioselectivity determining.

Reactivity of frustrated Lewis pairs with BOC protected diazocarboxylates: FLP capture of diazene.

Reactions of (BuOCN) with FLPs are examined. B(CF) interacts with the carbonyl oxygen atoms inducing loss of CHCMe; however, in the presence of basic donors, the protons are intercepted affording the salts [Hbase] [((CF)BOCN)] (base = BuP 1, NCHPh2, HNCHMe3). In contrast, in the presence of (-Tol)P, a proton transfers to the diazo-N atom affording (-Tol)PN(COBu)NHB(CF)4.

A non-self-consistent tight-binding electronic structure potential in a polarized double-ζ basis set for all spd-block elements up to Z = 86.

Existing semiempirical molecular orbital methods suffer from the usually minimal atomic-orbital (AO) basis set used to simplify the calculations. Here, a completely new and consistently parameterized tight-binding electronic structure Hamiltonian evaluated in a deeply contracted, properly polarized valence double-zeta basis set (vDZP) is described. The inner-shell electrons are accounted for by standard, large-core effective potentials and approximations to them.

[4+1] cyclization of α-diazo esters and mesoionic N-heterocyclic olefins.

Prompted by the recent stepwise mechanistic proposal for the Huisgen [3+2] cycloaddition reaction between enamine and α-diazo ester, where the nucleophilic addition of the enamine carbon onto the terminal nitrogen of diazo ester is crucial, we examined the possible use of N-heterocyclic olefins (NHOs) as highly electron-rich dipolarophiles in these reactions. The mesoionic NHOs derived from 1,2,3-triazoles undergo fast [4+1] cycloaddition to give 3-(triazolium-4-yl)-(3)-pyrazol-4-olates at room temperature. The reaction mechanism has been explored through experimental and DFT computational studies.

Synergistic Catalysis in Heterobimetallic Complexes for Homogeneous Carbon Dioxide Hydrogenation.

Two heterobimetallic Mo,M' complexes (M' = Ir, Rh) were synthesized and fully characterized. Their catalytic activity in homogeneous carbon dioxide hydrogenation to formate was studied. A pronounced synergistic effect between the two metals was found, most notably between Mo and Ir, leading to a fourfold increase in activity compared with a binary mixture of the two monometallic counterparts.

Diazene Chemistry: Metal-Free Models of N Reduction Intermediates.

Interest in main group chemistry related to the Haber-Bosch process has drawn less attention than that of transition metal species. Herein, we show that the steric demands in (BuOCN) block initial interaction of B(CF) with nitrogen and prompt loss of methylpropene and CO to diazene (NH) borane adduct and the analogous hydrazine (NH) adduct . These species react with basic phosphines to give anions of and containing NH and NH fragments, respectively.

BSSE-corrected consistent Gaussian basis sets of triple-zeta valence quality of the lanthanides La-Lu for solid-state calculations.

Consistent basis sets of triple-zeta valence quality for the elements La-Lu were derived for periodic quantum-chemical solid-state calculations. They are an extension of the pob-TZVP-rev2 [D. Vilela Oliveira, et al.

To Waste or Not to Waste: Questioning Potential Health Risks of Micro- and Nanoplastics with a Focus on Their Ingestion and Potential Carcinogenicity.

Micro- and nanoplastics (MNPs) are recognized as emerging contaminants, especially in food, with unknown health significance. MNPs passing through the gastrointestinal tract have been brought in context with disruption of the gut microbiome. Several molecular mechanisms have been described to facilitate tissue uptake of MNPs, which then are involved in local inflammatory and immune responses.

Liquid Dynamics Determine Transition Metal-N-Heterocyclic Carbene Complex Formation.

Invited for the cover of this issue are Oldamur Hollóczki and co-workers at the Universities of Bonn, Ghent and Debrecen. The image depicts the search of an ionic base for the acidic proton of an imidazolium cation in order to form a carbene complex. Read the full text of the article at 10.

molecular dynamics calculations on electron ionization induced fragmentations of CFN and CFO for understanding their decompositions under discharge conditions.

CFN and CFO are the most promising SF alternatives as eco-friendly insulating gaseous mediums in electrical engineering. It is necessary to clarify their electrical stability and decomposition mechanisms. In this work, we first introduced our experimental results for decomposition products of CFN/CO and CFO/synthetic air mixtures under partial discharge and spark discharge conditions.

London Dispersion Effects in a Distannene/Tristannane Equilibrium: Energies of their Interconversion and the Suppression of the Monomeric Stannylene Intermediate.

Reaction of {LiC H -2,4,6-Cyp ⋅Et O} (Cyp=cyclopentyl) (1) of the new dispersion energy donor (DED) ligand, 2,4,6-triscyclopentylphenyl with SnCl afforded a mixture of the distannene {Sn(C H -2,4,6-Cyp ) } (2), and the cyclotristannane {Sn(C H -2,4,6-Cyp ) } (3). 2 is favored in solution at higher temperature (345 K or above) whereas 3 is preferred near 298 K. Van't Hoff analysis revealed the 3 to 2 conversion has a ΔH=33.

Design of transition metal complexes containing a P-E radical motif.

Recently, we have synthesized phosphane W(CO) complexes containing a -O-TEMP ligand motif as bench-stable precursors of thermally accessible phosphanoxyl complex radicals possessing a ligand with a P-O˙ group. In this work, extensive dispersion-corrected DFT calculations are used to explore both W(CO) and Fe(CO) phosphane complexes containing the -E-TEMP ligands (E = O, S, NMe, and PMe) in order to reach thermally accessible radicals with a P-E˙ motif. Moreover, a more general single-electron transfer (SET) oxidation approach to synthesize such P-E˙ radicals anionic precursors is disclosed.

TBMaLT, a flexible toolkit for combining tight-binding and machine learning.

Tight-binding approaches, especially the Density Functional Tight-Binding (DFTB) and the extended tight-binding schemes, allow for efficient quantum mechanical simulations of large systems and long-time scales. They are derived from ab initio density functional theory using pragmatic approximations and some empirical terms, ensuring a fine balance between speed and accuracy. Their accuracy can be improved by tuning the empirical parameters using machine learning techniques, especially when information about the local environment of the atoms is incorporated.