C carbide ligand in the trigonal prismatic environment of rheniums in [Re12CS17(CN)6] complexes

The electronic state of carbon in trigonal prismatic environment in [Re₁₂CS₁₇(CN)₆]ⁿ⁻ complexes with variable redox state n = 6 ↔ 8 was studied by molecular orbital method and electron localization function. The state is characterized by sp²-hybridisation and oxidation state −4. A weak long-distance interaction between μ₆-С and μ₂-S in the group [(μ₆-С)(μ₂-S)₃] was discovered for n = 6, the interaction disappears for n = 8.     

A novel workflow control system for Fourier transform ion cyclotron resonance mass spectrometry allows for unique on-the-fly data-dependent decisions

In this paper a novel workflow-based data acquisition and control system for Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) is presented that facilitates a fast on-the-fly decision-making process for a wide variety of data-dependent experiments. Several new workflow implementations demonstrate the flexibility and benefit of this approach for rapid dynamic experimental design on a chromatographic timescale. The different sequence, evaluation, decision and monitoring modules are described using a selected set of examples. During a tandem liquid chromatography (LC)/FTICR-MS experiment the system is used to dynamically switch between various dissociation techniques such as electron capture dissociation (ECD) and sustained off-resonance irradiation (SORI) depending on the charge state of a tryptic peptide peak. The use of this workflow-based system for imaging FTICR-MS using a desorption electrospray ionization (DESI) source demonstrates the possibility of external control of the workflow by feedback from an imaging sample stage.     

Electron localizability indicators ELI and ELIA: the case of highly correlated wavefunctions for the argon atom

Electron localizability indicators based on the same-spin electron pair density and the opposite-spin electron pair density are studied for correlated wavefunctions of the argon atom. Different basis sets and reference spaces are used for the multireference configuration interaction method following the complete active space calculations aiming at the understanding of the effect of local electron correlation when approaching the exact wavefunction. The populations of the three atomic shells of Ar atom in real space are calculated for each case.     

The interfacial tension and phase diagram of the Widom-Rowlinson mixture via Monte Carlo simulations

Results of Monte Carlo simulations are reported for the interfacial tension between two fluid phases in a binary mixture of penetrable spheres in which molecular pairs of like species do not interact, while those of unlike species interact as hard spheres. Semigrand canonical ensemble Monte Carlo simulations in a cubic cell with periodic boundary conditions are used to obtain histograms for various system sizes at various densities. At a given density, the interfacial tension and compositions of coexisting phases for an infinite system are evaluated via histogram analysis combined with finite-size scaling. The density dependence of the interfacial tension and phase diagram for an infinite system are thus obtained. The simulated behavior of the interfacial tension close to the critical density corroborates previous suggestions that the model belongs to the three-dimensional Ising universality class.     

Complex coacervation: a field theoretic simulation study of polyelectrolyte complexation

Using the complex Langevin sampling strategy, field theoretic simulations are performed to study the equilibrium phase behavior and structure of symmetric polycation-polyanion mixtures without salt in good solvents. Static structure factors for the segment density and charge density are calculated and used to study the role of fluctuations in the electrostatic and chemical potential fields beyond the random phase approximation. We specifically focus on the role of charge density and molecular weight on the structure and complexation behavior of polycation-polyanion solutions. A demixing phase transition to form a "complex coacervate" is observed in strongly charged systems, and the corresponding spinodal and binodal boundaries of the phase diagram are investigated.     

Generation and suppression of 3-/4-functionalized benzynes using zinc ate base (TMP-Zn-ate): new approaches to multisubstituted benzenes

We present full details of our new methods for preparing functionalized benzynes with lithium di-alkyl(2,2,6,6-tetramethylpiperidino)zincate (R2Zn(TMP)Li) through deprotonative zincation as a key reaction. In this system, by choosing appropriate ligands for the zincate, either regioselective zincation of functionalized haloaromatics or the generation of substituted benzynes can be controlled in good yields with excellent chemoselectivity, using the same substrate. Zincation with (t)Bu2Zn(TMP)Li followed by electrophilic trapping or zincation with Me2Zn(TMP)Li followed by nucleophilic or diene trapping is shown to be a powerful tool for the chemoselective preparation of 1,2,3-/1,2,4-trisubstituted benzene derivatives. These methods offer far greater generality than previous methods for the synthesis of multifunctionalized benzenes. Computational/theoretical studies of the reaction mechanism of this unique benzyne formation indicated that preferential coordination of the dialkylzinc moiety of zincate to halogen is the reason for the reduced activation energy of the elimination, that is, for the formation of the benzyne. The role of the ligands on Zn in accelerating/decelerating the elimination is also discussed.     

Synthesis of Derivatives of the Optically Active β‐Amino Acids from (+)‐Car‐2‐ene

The reaction of (+)‐car‐2‐ene ( 4 ) with chlorosulfonyl isocyanate (=sulfuryl chloride isocyanate; ClSO₂NCO) led to the tricyclic lactams 6 and 8 corresponding to the initial formation both of the tertiary carbenium and α‐cyclopropylcarbenium ions (Scheme 2). A number of optically active derivatives of β‐amino acids which are promising compounds for further use in asymmetric synthesis were synthesized from the lactams (see 16, 17 , and 19 – 21 in Scheme 3).     

Crystal structure and chemical bonding of Mg3Ru2

Mg 3Ru 2 was prepared by a reaction between the elements in the ideal ratio in a sealed tantalum ampule. Its beta-manganese type crystal structure was refined on the basis of the single-crystal data: space group P4 132, a = 693.52(6) pm, wR2 = 0.024, 168 F (2) values, and 10 parameters. The magnesium (CN = 14) and ruthenium (CN = 12) atoms are completely ordered on the 12d and 8c sites of the crystal structure of beta-manganese. Both environments can be considered as Frank-Kasper related polyhedra. A periodic nodal surface P4 132(110) pi (1) P4 132 separates the magnesium and ruthenium positions in two different labyrinths, suggesting different chemical interactions within different parts of the structural motif. Analysis of the chemical bonding with the electron localizability indicator (ELI-D) reveals covalently interacting three-bonded ruthenium atoms, forming a 3D network. The network interacts with the magnesium substructure by multicenter bonds.     

Recognizing alpha-, beta- or gamma-substitution in pyridines by mass spectrometry

A general mass spectrometric method able to recognize the site of substitution of monosubstituted pyridines is described. The method requires that the molecule under investigation forms, upon ionization and dissociation, the respective alpha-, beta- or gamma- pyridinium ion of m/z 78. Pyridinium ions are stable and common fragments of ionized and protonated pyridines and are found to function as appropriate structurally diagnostic fragment ions. They can be identified by their characteristic and nearly identical collision-induced dissociation behavior and distinguished by the combined use of two structurally diagnostic ion/molecule reactions with acetonitrile and 2-methyl-1,3-dioxolane. alpha-, beta- or gamma-substitution in pyridines can, therefore, be securely recognized via an MS-only method based on structurally diagnostic ions and by the inspection of a single molecule (no need for intracomparisons within the whole set of isomers).     

Reactions over multiple, interconnected potential wells: unimolecular and bimolecular reactions on a C3H5 potential

In this article we analyze quantitatively and discuss in detail a number of reactions that take place on a C3H5 potential. These reactions include the reaction of hydrogen atoms with allene and propyne, the reaction of methyl with acetylene, the isomerization of cyclopropyl to allyl, and the dissociation of allyl, 1-propenyl, and 2-propenyl. The theory employs high-level electronic-structure methods to characterize the potential energy surface, RRKM theory to calculate microcanonical, J-resolved rate coefficients, and master-equation methods to determine phenomenological rate coefficients, k(T,p). The agreement between our theory and the experimental results available is very good. The final theoretical results are cast in a form that is convenient for use in chemical kinetics modeling.