Prediction of heptagonal bipyramidal nonacoordination in highly viable [OB-M©B7O7-BO]− (M = Fe, Ru, Os) complexes

Non-spherical distributions of ligand atoms in coordination complexes are generally unfavorable due to higher repulsion than for spherical distributions. To the best of our knowledge, non-spherical heptagonal bipyramidal nonacoordination is hitherto unreported, because of extremely high repulsion among seven equatorial ligand atoms. Herein, we report the computational prediction of such nonacoordination, which is constructed by the synergetic coordination of an equatorial hepta-dentate centripetal ligand (B7O7) and two axial mono-dentate ligands (-BO) in the gear-like mono-anionic complexes [OB-M©B7O7-BO]– (M = Fe, Ru, Os). The high repulsion among seven equatorial ligand B atoms has been compensated by the strong B–O bonding. These complexes are the dynamically stable (up to 1500 K) global energy minima with the HOMO-LUMO gaps of 7.15 to 7.42 eV and first vertical detachment energies of 6.14 to 6.66 eV (being very high for anions), suggesting their high probability for experimental realization in both gas-phase and condensed phases. The high stability stems geometrically from the surrounded outer-shell oxygen atoms and electronically from meeting the 18e rule as well as possessing the σ + π + δ triple aromaticity. Remarkably, the ligand-metal interactions are governed not by the familiar donation and backdonation interactions, but by the electrostatic interactions and electron-sharing bonding.

Mechanisms for the creation of intrinsic electron-hole trapping centers in a CaSO4 crystall

The mechanism of creation of electron-hole trapping centers in CaSO4 at 15-300 K was investigated by the methods of vacuum-ultraviolet and thermoactivation spectroscopy. It is shown that electron-hole trapping centers are formed upon trap of electrons in the anionic complexes SO4− and localization of holes in the form of SO4− radical. Based on the measurement of the spectrum of excitation of long-wavelength recombination emission at 3.0-3.1 eV and 2.7 eV, the energy distance of the formed electron-hole trapping centers was estimated (4.43 eV and 3.87 eV).

Oxovanadium(V/IV) Complexes as Redox Mediators for Biofuel Cells: Physical, Magnetic, and Electrochemical Characterization, DFT and Molecular Docking

Based on the potential redox and catalytic ability of oxovanadium complexes, our goal was to characterize the physical properties of two such complexes to be used as mediators for laccase. Computational studies, TD-DFT calculations and docking simulations were performed to elucidate the interaction between laccase and the two anionic complexes (aquabis(oxalato)oxidovanadate(IV) (1) and bis(oxalato)dioxidovanadate(V)) (2), respectively. Electrochemical measurements carried out on anion complexes of 1 and 2 docked into laccase were compared to laccase alone, showing changes in oxidation-reduction potential and current value, especially with the oxovanadium anion of 2. Since both internal tiny magnetic fields of ferromagnetic catalysts and external applied magnetic fields were found in previous investigations to constitute effective ways to improve the oxygen transfer rate, the magnetic susceptibility was measured. A valence change proneness was confirmed with higher valence for the oxovanadium anion of 2, which is in accordance with the electrochemical results.

Mechanisms formation of electron-hole trap centers in LiKSO4 crystall

The mechanisms of creation of electron-hole trapping centers in LiKSO4 have been investigated by the methods of vacuum and thermal activation spectroscopy. It is shown that electron-hole trapping centers are formed during the trapping of electrons by anionic complexes and localization of a hole in the lattice in the form of the radical SO4−. The appearance of phosphorescence at 3.0-3.1 eV, 2.6-2.7 eV and 2.3-2.4 eV confirms the creation of electron-hole trap centers.

Crystal structure of diammonium bis[tris(oxamide dioxime-κ2 N,N′)nickel(II)] bis[tris(oxalato-κ2 O,O′)chromate(III)] 6.76-hydrate

The asymmetric unit of the title compound, (NH4)2[Ni(C2H6N4O2)3]2[Cr(C2O4)3]2·6.76H2O, comprises two NH4 + cations, two [Ni(C2H6N4O2)3]2+ cations and two [Cr(C2O4)3]3– anions, as well as eight water molecules of crystallization of which only one is fully occupied. In the cationic and anionic complexes, the central atoms (NiII and CrIII) are each surrounded by three bidentate ligands (N-chelating oxamide dioxime and O-chelating oxalate, respectively), resulting in distorted octahedral coordination spheres. In the crystal, O—H...O hydrogen bonds between the oxamide dioxime ligands as donor groups and the oxalate ligands as acceptor groups alternately connect the cationic and anionic complexes into infinite pillars extending parallel to [100]. Moreover, N—H...O hydrogen bonds between the same ligands connect neighboring pillars, thus delineating channels that accommodate the charge-balancing NH4 + cations as well as the water molecules of crystallization. Although the H atoms could not be localized for these two species, the corresponding N...O and O...O distances indicate hydrogen bonds of medium strength.

EXTRACTION OF ANIONIC CADMIUM COMPLEXES WITH ORGANIC SOLUTIONS OF QUATERNARY AMMONIUM SALTS

The anion-exchange extraction of thiocyanate, chloride and iodide cadmium complexes by solutions of quaternary ammonium salts chlorides in organic solvents (toluene, carbon tetrachloride, ethyl acetate, isobutyl alcohol, nitrobenzene) was studied. Extraction involves solutions of alkyl dimethylbenzylammonium chlorides (R-N+(CH3)2-CH2C6H5-Cl-) and alkyl dimethylethyl-benzylammonium (R-N+(CH3)2-CH2-CH2C6H5-Cl-), where R is a straight alkyl chain, mainly C12 - C14. The composition of the cadmium anionic complexes was established by the analysis of the calibration curves E = f (pCCd (II)) constructed from cadmium sulfate solutions against the background of various contents of thiocyanate, chloride and iodide ions (ndicator electrode - ion-selective electrode with a membrane, which based on a nitrobenzene solution of tetradecylammonium bromide). The extraction process is estimated quantitatively using a distribution coefficient (D). The value of D is calculated taking into account the cadmium concentration in the aqueous phase before and after extraction. The dependence of the distribution coefficient on the organic solvent dielectric constant, the concentration and stability of the anionic complexes of cadmium is shown. So, for the indicated cadmium acidocomplexes, the minimum D values were obtained using low-polar toluene and carbon tetrachloride, and the maximum values were obtained using highly polar isobutyl alcohol and nitrobenzene. If the concentration of cadmium (II) is reduced by a factor of 100 for the cadmium rhodanide and iodide complexes, the value of D decreases by 1.6-1.9 times, for the chloride complex, by 1.2 times in the case of polar isobutyl alcohol and nitrobenzene, and 2.9-3.5 times in the case of low-polar solvents. It was experimentally established that in the series [Cd(SCN)4]2- - [CdI4]2-- [CdCl4]2- the value of D decreases for all the studied systems. The observed regularity is related both to the stability of the corresponding cadmium (II) complexes in aqueous solutions and to their hydrophobicity.