Titanocene-Catalyzed [2+2] Cycloaddition of Bisenones and Comparison with Photoredox Catalysis and Established Methods.

Cp Ti(TFA) is a broadly applicable catalyst for the [2+2] cycloaddition of bisenones by inner-sphere electron transfer. The attractiveness of this mechanism is shown by comparison with outer-sphere ET methods. DFT calculations show that the reaction proceeds through a unique unfavorable 5-exo (the rate-determining step) and a favorable 4-exo cyclization.

BSSE-corrected consistent Gaussian basis sets of triple-zeta valence with polarization quality of the sixth period for solid-state calculations.

Consistent basis sets of triple-zeta valence with polarization quality for the elements Cs-Po were derived for periodic quantum-chemical solid-state calculations. They are an extension of the pob-TZVP-rev2 [Vilela Oliveira, D.; Laun, J.

Efficient Quantum Chemical Calculation of Structure Ensembles and Free Energies for Nonrigid Molecules.

The application of quantum chemical, automatic multilevel modeling workflows for the determination of thermodynamic (e.g., conformation equilibria, partition coefficients, p values) and spectroscopic properties of relatively large, nonrigid molecules in solution is described.

How is CO absorbed into a deep eutectic solvent?

Deep eutectic solvents show great potential as CO absorbents, which is highly desirable for the sustainable development of CO reduction and prevention of global climate changes. Ab initio molecular dynamics simulations in the isothermal-isobaric ensemble at pressures of 1 MPa and 5 MPa and at the corresponding experimental density are carried out to investigate the CO absorption in choline chloride: ethylene glycol deep eutectic solvent. Based on the structural analysis, there is a strong anion and hydrogen bond donor effect and a minor cation effect on CO solvation in the solvent.

Surfaces of VO -Polymorphs: Structure, Stability and the Effect of Doping.

Vanadium dioxide is an interesting and frequently applied material due to its metal-insulator phase transition. However, there are only few studies of the catalytic activity and surface properties of different VO polymorphs. Therefore, we investigated the properties of the surfaces of the most stable VO phases theoretically at density-functional theory level using a self-consistent hybrid functional which has demonstrated its accuracy for the prediction of structural, electronic and energetic properties in a previous study.

Chiral Dibenzopentalene-Based Conjugated Nanohoops through Stereoselective Synthesis.

Conjugated nanohoops allow to investigate the effect of radial conjugation and bending on the involved π-systems. They can possess unexpected optoelectronic properties and their radially oriented π-system makes them attractive for host-guest chemistry. Bending the π-subsystems can lead to chiral hoops.

rSCAN-3c: A "Swiss army knife" composite electronic-structure method.

The recently proposed rSCAN meta-generalized-gradient approximation (mGGA) of Furness and co-workers is used to construct an efficient composite electronic-structure method termed rSCAN-3c. To this end, the unaltered rSCAN functional is combined with a tailor-made triple-ζ Gaussian atomic orbital basis set as well as with refitted D4 and geometrical counter-poise corrections for London-dispersion and basis set superposition error. The performance of the new method is evaluated for the GMTKN55 database covering large parts of chemical space with about 1500 data points, as well as additional benchmarks for non-covalent interactions, organometallic reactions, and lattice energies of organic molecules and ices, as well as for the adsorption on polar salt and non-polar coinage-metal surfaces.

rSCAN-D4: Dispersion corrected meta-generalized gradient approximation for general chemical applications.

We combine a regularized variant of the strongly constrained and appropriately normed semilocal density functional [J. Sun, A. Ruzsinszky, and J.

Exclusively Relativistic: Periodic Trends in the Melting and Boiling Points of Group 12.

First-principles simulations can advance our understanding of phase transitions but are often too costly for the heavier elements, which require a relativistic treatment. Addressing this challenge, we recently composed an indirect approach: A precise incremental calculation of absolute Gibbs energies for the solid and liquid with a relativistic Hamiltonian that enables an accurate determination of melting and boiling points (MPs and BPs). Here, we apply this approach to the Group 12 elements Zn, Cd, Hg, and Cn, whose MPs and BPs we calculate with a mean absolute deviation of only 5 % and 1 %, respectively, while we confirm the previously predicted liquid aggregate state of Cn.

Single-Point Hessian Calculations for Improved Vibrational Frequencies and Rigid-Rotor-Harmonic-Oscillator Thermodynamics.

The calculation of harmonic vibrational frequencies (HVF) to interpret infrared (IR) spectra and to convert molecular energies to free energies is one of the essential steps in computational chemistry. A prerequisite for accurate thermostatistics so far was to optimize the molecular input structures in order to avoid imaginary frequencies, which inevitably leads to changes in the geometry if different theoretical levels are applied for geometry optimization and frequency calculations. In this work, we propose a new method termed single-point Hessian (SPH) for the computation of HVF and thermodynamic contributions to the free energy within the modified rigid-rotor-harmonic-oscillator approximation for general nonequilibrium molecular geometries.

Reactions of B (o-tolyl) with Boranes: Assembly of the Pentaborane(9), HB[B(o-tolyl)(μ-H)].

Reactions of the diborane(4) B (o-tolyl) and monohydridoboranes are shown to give B(o-tolyl) and (o-tolyl)BR (R =(C H ) 3, cat 4, pin 5, (C F ) 6) as the major products. The corresponding reaction with BH -sources gives complex mixtures, resulting from hydride/aryl exchange, dimerization and borane elimination. This led to the isolation of the first tetra-substituted pentaborane(9) HB[B(o-tolyl)(μ-H)] 8.

CuZnSbS: A Thioantimonate(V) with Remarkably Strong Covalent Sb-S Bonding.

A new member to the ABCX compound family, CuZnSbS, was synthesized successfully using ball milling and postannealing in HS-atmosphere. For comparative purposes, CuSbS was additionally prepared using the same synthetic approach. As is common for ABCX compounds, CuZnSbS crystallizes isostructural to CuSbS in the stannite-type structure in space group 42.

Hydrogenation of Secondary Amides using Phosphane Oxide and Frustrated Lewis Pair Catalysis.

The metal-free catalytic hydrogenation of secondary carboxylic acid amides is developed. The reduction is realized by two new catalytic reactions. First, the amide is converted into the imidoyl chloride by triphosgene (CO(OCCl ) ) using novel phosphorus(V) catalysts.

Lithium Dicyclohexylamide in Transition-Metal-Free Fischer-Tropsch Chemistry.

Lithium dicyclohexylamide (CyNLi) reacts with syn-gas or CO to generate transient intermediates with carbene character, which are capable of reacting further with CO or H, effecting sequential C-C and C-H bond formations from CO or H, thus providing a transition-metal-free avenue to the fundamental reactions of the Fischer-Tropsch process. Further experimental and computational data indicate that reactions with CO and H are thermodynamically accessible, with a kinetic bias toward CO homologation.

TiCl Dissolved in Ionic Liquid Mixtures from ab Initio Molecular Dynamics Simulations.

To gain a deeper understanding of the TiCl4 solvation effects in multi-component ionic liquids, we performed ab initio molecular dynamics simulations of 1-butyl-3-methylimidazolium [C4C1Im]+, tetrafluoroborate [BF4]-, chloride [Cl]- both with and without water and titanium tetrachloride TiCl4. Complex interactions between cations and anions are observed in all investigated systems. By further addition of water and TiCl4 this complex interaction network is extended.

A case study on the conversion of Li/Cl phosphinidenoid into phosphinidene complexes.

N,N-Diphenylamino- and N,N-dicyclohexylamino-substituted dichlorophosphane W(CO) complexes 1a,b were used to generate thermally very labile Li/Cl phospinidenoid W(CO) complexes 2a,b. The formation of transient complex 2a was confirmed via low-temperature P{H} NMR spectroscopy, but further strong evidence for the formation of transient complexes 2a,b was obtained from reactions with methanol and methylamine as formal E-H insertions (E = O, N) furnished complexes 3a,b and 4a. By using toluene in the absence of donor ligands, the primarily nucleophilic complexes 2a,b were converted into electrophilic terminal phosphinidene complexes 5a,b which was deduced from specific trapping reactions using tolane, 1-pentene and 1-hexene and thus obtained 1H-phosphirene 6 and phosphirane complexes 7 and8.

Theoretical study on conformational energies of transition metal complexes.

Conformational energies are an important chemical property for which a performance assessment of theoretical methods is mandatory. Existing benchmark sets are often limited to biochemical or main group element containing molecules, while organometallic systems are generally less studied. A key problem herein is to routinely generate conformers for these molecules due to their complexity and manifold of possible coordination patterns.

Comprehensive Benchmark Study on the Calculation of Si NMR Chemical Shifts.

A comprehensive and diverse benchmark set for the calculation of Si NMR chemical shifts is presented. The set includes 100 silicon containing compounds with 146 experimentally determined reference Si NMR chemical shifts measured in nine different solvents in a range from -400 to +828 ppm. Silicon atoms bound to main group elements as well as transition metals with coordination numbers of 2-6 in various bonding patterns including multiple bonds and coordinative and aromatic bonding are represented.

Non-steroidal Anti-inflammatory Drugs Target TWISTED DWARF1-Regulated Actin Dynamics and Auxin Transport-Mediated Plant Development.

The widely used non-steroidal anti-inflammatory drugs (NSAIDs) are derivatives of the phytohormone salicylic acid (SA). SA is well known to regulate plant immunity and development, whereas there have been few reports focusing on the effects of NSAIDs in plants. Our studies here reveal that NSAIDs exhibit largely overlapping physiological activities to SA in the model plant Arabidopsis.

Oxidation Under Reductive Conditions: From Benzylic Ethers to Acetals with Perfect Atom-Economy by Titanocene(III) Catalysis.

Described here is a titanocene-catalyzed reaction for the synthesis of acetals and hemiaminals from benzylic ethers and benzylic amines, respectively, with pendant epoxides. The reaction proceeds by catalysis in single-electron steps. The oxidative addition comprises an epoxide opening.

A Unified Strategy for the Chemically Intuitive Interpretation of Molecular Optical Response Properties.

Interpreting response properties such as the polarizability, optical rotation (OR), or hyperpolarizabilities is a complex task for which a uniform strategy would be desirable. We propose a response analysis procedure called the RespA approach with two interrelated schemes to describe molecular optical response properties in terms of natural response orbitals (NROs) and chemical fragment response for convenient elucidation of structure-(optical)property relationships. These quantities can be easily extracted from the frequency-dependent perturbed one-electron transition/current density matrix obtained from any quantum mechanical response function calculation.

The Reactivity of Isomeric Nitrenium Lewis Acids with Phosphines, Carbenes, and Phosphide.

Alkylation of spiro[fluorene-9,3'-indazole] at N(1) and N(2) with tBuCl affords the nitrenium cations [C H N (tBu)C(C H )][BF ], 1 and 2, respectively. Compound 1 converts to 2 over the temperature range 303-323 K with a free energy barrier of 28±5 kcal mol . Reaction of 1 with PMe afforded the N-bound phosphine adduct [C H N(tBu)N(PMe )C(C H )]BF ] 3.

Modeling of spin-spin distance distributions for nitroxide labeled biomacromolecules.

Electron Paramagnetic Resonance (EPR) spectroscopy is a powerful method for unraveling structures and dynamics of biomolecules. Out of the EPR tool box, Pulsed Electron-Electron Double Resonance spectroscopy (PELDOR or DEER) enables one to resolve such structures by providing distances between spin centers on the nanometer scale. Most commonly, both spin centers are spin labels or one is a spin label and the other is a paramagnetic metal ion, cluster, amino acid or cofactor radical.

Quantification of Noncovalent Interactions in Azide-Pnictogen, -Chalcogen, and -Halogen Contacts.

The noncovalent interactions between azides and oxygen-containing moieties are investigated through a computational study based on experimental findings. The targeted synthesis of organic compounds with close intramolecular azide-oxygen contacts yielded six new representatives, for which X-ray structures were determined. Two of those compounds were investigated with respect to their potential conformations in the gas phase and a possible significantly shorter azide-oxygen contact.

Accurate elemental boiling points from first principles.

The normal boiling point (NBP) is a fundamental property of liquids and marks the intersection of the Gibbs energies of the liquid and the gas-phase at ambient pressure. This work provides the first comprehensive demonstration of the calculation of boiling points of atomic liquids through first-principles molecular-dynamics simulations. To this end, thermodynamic integration (TDI) and perturbation theory (TPT) are combined with a density-functional theory (DFT) Hamiltonian, which provides absolute Gibbs energies, internal energies, and entropies of atomic liquids with an accuracy of a few meV/atom.