Vol 60, No 12 (2019)

Double molybdates of indium and scandium with alluaudite structure are prepared by the solid-phase synthesis method. The crystal structure of the indium containing compound is refined and optical characteristics of Na₅R(Mo0₄)₄(R = Sc, In) are determined. Electronic structures of Na₅R(Mo0₄)₄(R = Sc, In) molybdates are studied within the ab initio method taking account of Na/Sc(In) positional disordering. Calculations of the imaginary part of dielectric function predict the optical gap of ~3.8 eV, in accordance with absorption spectroscopy data. It is established that formation energy of sodium vacancies strongly depends on sodium position and Sc(In) concentration. As a result, various diffusion mechanisms may be activated in alluaudite-type compounds with high and low contents of metal R.

Various types of coordination numbers in molecular crystals are discussed. The relationship between parameter R of the Delone system, coordination number (CN), topological type, and the intermolecular interaction energy is studied on the example of crystal structures of centrosymmetric hydrocarbons. The first coordination sphere of a molecule takes 86.2±1.6% of the lattice energy; the interactions providing molecular arrangement take at least 50% of the lattice energy for CN ≥ 6. The nets characterizing the framework of intermolecular interactions in this series of structures tend to the lowest cyclomatic number of the quotient graph.

This study presents a computational investigation of p-phenylenediamine (PPD) interaction with 3,5-dinitrosalicylic acid (DNS) within PPD/DNS charge transfer (CT) complex. All calculations were performed by M06-2X/6-311+G(d,p) levels of theory in vacuum, water and methanol. EDA analysis was used to control the complexation process and suggested that electrostatic and dispersion energies contributes greatly in stabilizing PPD/DNS CT complex. The results of energy optimization showed that PPD/DNS CT complex is stable with negative complexation energy; the obtained geometries showed that ammonium group of PPD is closed to carboxylate one of DNS enabling the establishment of large number of interactions. Additionally, different analyses were performed on obtained optimized structures: TD-DFT, NBO, QTAIM and NCI. Consequently, NBO, QTAIM and NCI analysis give that PPD/DNS CT complex is stabilized by hydrogen bonding and van der Waals interactions.

Ultraviolet photoelectron spectroscopy in the gas phase (UPS, HeI), X-ray photoelectron spectroscopy in the condensed phase (XPS, MgK_α), and quantum chemical methods (DFT) are used to study the adducts of Eu(III) tris-hexafluoroacetylacetonate with two molecules of four-coordinated phosphorus, namely HMPA (OP[N(CH₃)₂]₃) and TPPO (OP(C₆H₅)₃). Spectral bands of valence and core levels are interpreted using energy calculations and localization of Kohn-Sham orbitals. It is shown that TPPO and HMPA molecules influence the electronic structure of the complexes; positions and localizations of molecular orbitals are determined, the nature of bonding between Eu(III) and three chelate ligands and two neutral molecules is established. The differences in positions and compositions of occupied and vacant orbitals participating in energy transfer under excitation are shown. It is estimated that the bonding energy between Eu(hfac)₃ and the two molecules is 10.91 eV for OP(C₆H₅)₃, 12.62 eV for OP[NMe₂]₃, and 24.9 eV for SP[NMe₂]₃. It is shown how the differences between the energies and localizations of HOMOs of neutral molecules affect the structure, localization of adducts by the frontier molecular orbital (MO) and HOMO-LUMO gaps and how these differences determine the parameters of “antenna” ligand effects and the relative quantum yield of the luminescence of the adduct.

The crystallographic analysis of six SiO₂ phases (α-quartz, β-tridymite, α- and β-cristobalite, coesite, and stishovite) is performed. The effect of the local symmetry of SiO₄ tetrahedra on the symmetry of phases tending either to highly symmetrical cubic P-cristobalite or hexagonal P-tridymite is shown. The parameters of cation, anion, and joint pseudotranslational sublattices characterizing the atomic configurations of the structures and their individual features are calculated. The relative stability of the phases is considered.

Two new coordination polymers are obtained: layered [Hdabco][Sc₂(H20)2(OH)(tFBDC)3]-3/2C4H_gO₂ (1) (dabco=1,4-diazabicyclo[2.2.2]octane) and chain-like [Zn(CH₃OH)₄(oFBPDC)]-2CH₃OH (2). They are formed by anions of perfluorinated terephthalic (tFBDC²) and biphenyl-4,4'-dicarboxylic (oFBPDC²) acids. The composition and structure of the obtained compounds are determined by the single crystal X-ray diffraction analysis.

In this paper, bis-monodentate Schiff base ligand (2,4-Cl-ba)₂bn and its 1D copper(I) coordination polymer [Cu₂(μ-(2,4-Cl-ba)₂bn)(μ-I₂)]_n are synthesized and characterized by the elemental analysis (CHN), FT-IR and ¹H NMR spectroscopy. Their crystal structure is determined from the single crystal X-ray diffraction analysis. The thermal behavior of the complex is studied using thermogravimetry in order to evaluate its thermal stability and thermal decomposition pathway. The X-ray results show that the free Schiff base ligand (2,4-Cl-ba)₂bn is centrosymmetric and coordinated to copper(I) ions via two iminic nitrogen atoms as a bis-monodentate bridging ligand. The coordination geometry around the copper ions is a distorted triangle formed by one nitrogen and two iodine atoms. The distance between the two symmetry-related copper atoms is very short: 2.4756(8) Å.

A three-dimensional Cd(II) complex [Cd(L)(BPDC)]-3H₂O (1) (L = 3,5-di(1H-benzimidazol-1-yl)pyridine, H₂BPDC = biphenyl-4,4-dicarboxylic acid) is synthesized and characterized using single crystal X-ray diffraction, IR spectroscopy, and elemental analysis. The single crystal X-ray diffraction analysis reveals that complex 1 is a novel twofold interpenetrating 4-connected net with a (6⁵·8) topology. Moreover, complex 1 exhibits an emission band at 400 nm with an inconspicuous shoulder at 525 nm (λ_ex = 329 nm).

A new heterocyclic compound ethyl 3-(3-amino-4-(methylamino)-N-(pyridin-2-yl)benzamido)propanoate (1), designed using 4-(methylamino)-3-nitrobenzoic acid (2) as a starting material is successfully obtained via a multiple synthesis route and finally characterized by IR, ¹H NMR, and single crystal X-ray crystallography. In addition, the in vitro anti-cancer activity of newly synthesized complex 1 is emulated against three human gastric cancer cell lines SGC-790, MKN-4, and MKN45.