Vol 60, No 6 (2019)

The review summarizes the data obtained in the studies of transition metal complexes (V^IVO, Co^II, Ni^II, Cu^II, Zn^II) with anions of substituted malonic acids, which are not only coordination polymers but also compounds with a discrete molecular structure. The influence of malonic acid substituents and the nature of metal ions (alkali, alkaline earth, and transition metals) on the formation of molecular and polymeric systems is discussed. The crystal structures of recently described heterometallic coordination polymers are analyzed.

The experimental crystal structure of a Schiff base compound 4-bromo-2-(4,6-dichloro-phenylimino)-phenol 1 is determined by single crystal X-ray diffraction and also characterized by FT-IR and ¹H NMR spectroscopy. The electronic structure in the gas phase is studied by density functional theory (DFT) calculations.The theoretical results have good agreement with the data obtained from the crystallographic analysis. In addition, theoretical configurations which refer to the title compound are relaxed and studied in terms of the combined analysis of HOMO-LUMO energy gap, total density of states (DOS), partial density of state (PDOS), overlap population density of state (OPDOS), molecular electrostatic potential (MEP), NMR spectra, and harmonic vibrational frequencies.

The electronic structure of mono- and binuclear platinum complexes with N-phenyl-o benzosemiquinondiimine ligands was studied using X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, and the density functional theory. The oxidation state of the central platinum ion corresponds to that of Pt(II). Upon the transition from the trans-complex 1 to the cis-complex 2 and to the binuclear complex 3, the electron density on platinum and nitrogen atoms decreases thus testifying the participation of platinum and nitrogen atoms in the oxidation processes and in the formation of binuclear complex 3.

A new mechanism of the dipole-induced dipole polarizability effect by the example of

1-halogensilatranes is proposed. The mechanism involves a through-space interaction between the dipole moment μ of the core and the dipole Δμ which is induced on the halogen and, in turn, induces an extra dipole ΔΔμ on the transannular bond Si ← N to make it stronger. This effect explains for the first time the previously discovered contradiction for 1-halogensilatranes where an inverse dependence in the linear correlations between the Si ← N bond length, δ¹⁵N, δ¹H(CH₂N) chemical shifts, and the inductive constant σ are observed. For example, the length of the Si ← N coordination bond is shorter in 1-chlorosilatranе than in 1-fluorosilatrane due to the fact that the polarizability effect is stronger than the inductive effect in the case of the Cl atom.

The tungsten substitution for molybdenum in cesium dimolybdate Cs₂Mo₂O₇ with the formation of an α-Cs₂Mo_2−xW_xO₇ solid solution is studied, and its homogeneity region at 540 °C is found to reach 0 ≤ x ≤ 0.6. It is established that the volume of the monoclinic (pseudo-orthorhombic) unit cell and the solid solution melting point monotonically increase with increasing tungsten content, whereas the phase transition temperature to the orthorhombic phase remains practically constant and is ∼390 °C. The crystals of solid solutions with several compositions are obtained, their structure is determined, and the tungsten atoms are found to be mainly located in octahedral positions of the α-Cs₂Mo₂O₇ structure. As a result of the phase transition at 390 °C the electrical conductivity of Cs₂Mo₂O₇ increases approximately by two orders of magnitude reaching 1.2·10⁻⁴S/cm at 460 °C. Due to a large size of Cs⁺ ions and a high charge of molybdenum cations it is supposed that the charge carriers are oxygen anions. The calculation of bond valence sum (BVS) maps for possible positions of oxygen atoms in the α-Cs₂Mo₂O₇ cell shows the formation of a 3D system of oxygen conductivity channels at boundary BVS isosurface values ≥ 2.13.

Reaction of 2-(methylthio)pyrazine (L) with CuI (MeCN, r.t.) results in formation of iodide-bridged complex [Cu₂(μ₂-I)₂L₄], wherein Cu⋯Cu contact of 2.6351(4) Å is observed. The each metal atom of the [Cu₂(μ₂-I)₂] core is coordinated by the two ligands via 4-pyrazyl nitrogen atoms. In the solid state at room temperature, the complex obtained emits an orange photoluminescence (λ_max = 600 nm) with the average lifetime of 1.66 μs and quantum yield of 17%.

Features of the molecular structure in crystals of a series of functionalized 4-cyano-3(2H)-furanones with a spiro-cyclohexane substituent or two methyl groups at position 2 of the furanone ring and also an aryl or heteroaryl substituent at position 5 are analyzed in comparison with the literature data. Effects appearing in ¹H NMR spectra, which are caused by the features of the molecular structures of these compounds are interpreted. Their crystal structure is considered and intermolecular interactions responsible for the supramolecular architecture of the crystals formed are revealed.

A doctor can find out how pancreas is working using bentiromide. This drug can exist as six possible tautomers. Herein, by density functional theory (DFT) and handling the solvent effects with the polarizable continuum model (PCM), the mechanism of its tautomerization, energies, and structural parameters of the tautomers are investigated. Also, the natural bond orbital analysis (NBO) is used for exploring the frontier molecular orbitals. The most stable tautomer of bentiromide has three carbonyl groups in its structure. The amount of other tautomers is negligible in the aqueous solution. The non-covalent interactions of the most stable tautomer of bentiromide with an armchair (5,5) single-wall carbon nanotube and a γ-Fe₂O₃ nanoparticle are explored. In each case, three possible forms are optimized. Their most stable form is determined. The intermolecular H bonds have a critical role in the energy behavior of the interaction between bentiromide and the γ-Fe₂O₃ nanoparticle.