A sodium atom in a large water cluster: electron delocalization and infrared spectra

Ab initio molecular dynamics simulations modeling low-energy collisions of a sodium atom with a cluster with more than 30 water molecules are presented. We follow the dynamics of the atom-cluster interaction and the delocalization of the valence electron of sodium together with the changes in the electron binding energy. This electron tends to be shared by the nascent sodium cation and the water cluster. IR spectra of the sodium-water cluster are both computationally and experimentally obtained, with a good agreement between the two approaches.     

Two-dimensional thin-layer chromatography with adsorbent gradient as a method of chromatographic fingerprinting of furanocoumarins for distinguishing selected varieties and forms of Heracleum spp

There are a lot of taxonomic classifications of the genus Heracleum, and many authors indicate they need revision. Morphological identification is difficult to perform, as there are only few characteristic differences between each Heracleum species, varieties and forms. Furanocoumarins are characteristic compounds for the Apiaceae family, and they can be found in the whole genus in large quantities. Despite this fact, it is difficult to use the furanocoumarin profiles of plants, for their discrimination, as furanocoumarins are difficult to separate, due to their similar chemical structures and physicochemical properties. In this paper, a new, simple method is proposed for the discrimination of selected species, varieties and forms of the genus Heracleum. Thin-layer chromatography (TLC) with an adsorbent gradient (unmodified silica gel+octadecylsilica wettable with water) enables complete separation of the structural analogues. The proposed method gives the possibility to distinguish selected species, varieties and forms of the Heracleum genus, as they produce distinctive furanocoumarin fingerprints. The method is characterised by high specificity, precision, reproducibility and stability values. It is for the first time that graft TLC is used for constructing fingerprints of herbs. The complete separation of ten structural analogues, by combining gradient TLC with the unidimensional multiple development technique, has not been reported yet.     

Porous and Water Stable 2D Hybrid Metal Halide with Broad Light Emission and Selective H2O Vapor Sorption

In this work we report a strategy for generating porosity in hybrid metal halide materials using molecular cages that serve as both structure-directing agents and counter-cations. Reaction of the [2.2.2] cryptand (DHS) linker with Pb^II in acidic media gave rise to the first porous and water-stable 2D metal halide semiconductor (DHS)₂Pb₅Br₁₄. The corresponding material is stable in water for a year, while gas and vapor-sorption studies revealed that it can selectively and reversibly adsorb H₂O and D₂O at room temperature (RT). Solid-state NMR measurements and DFT calculations verified the incorporation of H₂O and D₂O in the organic linker cavities and shed light on their molecular configuration. In addition to porosity, the material exhibits broad light emission centered at 617 nm with a full width at half-maximum (FWHM) of 284 nm (0.96 eV). The recorded water stability is unparalleled for hybrid metal halide and perovskite materials, while the generation of porosity opens new pathways towards unexplored applications (e.g. solid-state batteries) for this class of hybrid semiconductors.     

Adsorption of aromatic hydrocarbons and ozone at environmental aqueous surfaces

Adsorption of environmentally important aromatic molecules on a water surface is studied by means of classical and ab initio molecular dynamics simulations and by reflection-absorption infrared spectroscopy. Both techniques show strong activity and orientational preference of these molecules at the surface. Benzene and naphthalene, which bind weakly to water surface with a significant contribution of dispersion interactions, prefer to lie flat on water but retain a large degree of orientational flexibility. Pyridine is more rigid at the surface. It is tilted with the nitrogen end having strong hydrogen bonding interactions with water molecules. The degree of adsorption and orientation of aromatic molecules on aqueous droplets has atmospheric implications for heterogeneous ozonolysis, for which the Langmuir-Hinshelwood kinetics mechanism is discussed. At higher coverages of aromatic molecules the incoming ozone almost does not come into contact with the underlying aqueous phase. This may rationalize the experimental insensitivity of the ozonolysis on the chemical nature of the substrate on which the aromatic molecules adsorb.     

Existence of oriented ion-hydroxide clusters in concentrated aqueous NaCl solution at pH 13

We probe the local electronic structure at solvated Na+ ions in 1 M aqueous NaCl solutions as a function of pH. A dramatic change in the Na+ white line intensity in X-ray absorption is observed for high pH values, reflecting a changing local electronic structure at the Na+ ions when OH- is present. Given the relative abundance of sodium and hydroxide ions, we conclude that one OH- affects at least 2.4+/-0.6 Na+ ions in an electronically noticeable way at pH 13. From the experimental data we infer that spatially extended clusters or networks incorporating Na+ and OH- can exist in the electrolyte solution. The experimental data are complemented by molecular dynamics simulations, which indicate the presence of structured clusters incorporating Na+, OH-, and solvent molecules.     

Extending the coordination chemistry of 1,3,5-triaza-7-phosphaadamantane (PTA) to cobalt centers: first examples of co-PTA complexes and of a metal complex with the PTA oxide ligand

Water-soluble Co (III) and Co (II) complexes with P- or N-coordinated PTA or PTA oxide ligands, respectively, have been prepared and fully characterized, constituting the first examples of cobalt compounds bearing PTA or any ligand with a cage-like PTA core, the latter complex providing also the first PTA oxide coordination to a metal center.     

Nevanlinna–Pick Problem and Uniqueness of Left Inverses in Convex Domains,Symmetrized Bidisc and Tetrablock

In the paper we discuss the problem of uniqueness of left inverses (solutions of two-point Nevanlinna–Pick problem) in bounded convex domains, strongly linearly convex domains, the symmetrized bidisc and the tetrablock.     

Regioselective Amine–Borane Cyclization: Towards the Synthesis of 1,2‐BN‐3‐Cyclohexene by Copper‐Assisted Triazole/Gold Catalysis

The combination of triazole/gold (TA‐Au) and Cu(OTf)₂ is identified as the optimal catalytic system for promoting intramolecular hydroboration for the synthesis of a six‐membered cyclic amine–borane. Excellent yields (up to 95 %) and regioselectivities (5‐exo vs. 6‐endo) were achieved through catalyst control and sequential dilution. Good functional‐group tolerance was attained, thus allowing the preparation of highly functionalized cyclic amine–borane substrates, which could not be achieved using other methods. Deuterium‐labeling studies support the involvement of a hydride addition to a gold‐activated alkyne with subsequent C?B bond formation.