Journal of Structural Chemistry最新文献

Formation of Ln³⁺ lanthanide complexes with di-(2-ethylhexyl) phosphoric acid (HDEHP) is studied by the density functional theory method. In the calculations, HDEHP is modeled by dimethylphosphoric acid (HDMP). It is shown that formation of the Ln(HDMP)₃(DMP)₃ complex from the Ln(DMP)₃ complex in an organic medium is determined by two factors: lanthanide contraction and solvent polarity. The probability of Ln(HDMP)₃(DMP)₃ formation decreases with increasing lanthanide serial number and increases with decreasing solvent polarity. The presence of complexes with a number of HDMP/DMP‾ ligands larger than six in the organic medium is unlikely.

The crystal structure of 3,4-difluorobenzyloxyme and 2,4,6-trimethylbenzyloxyme is studied by X-ray diffraction. It is established that 3,4-difluorobenzyloxyme molecules form chains due to O–H⋯N hydrogen bonds, which also form dimers in the crystal packing of 2,4,6-trimethylbenzyloxyme. The crystal lattice energies are calculated by the method of pairwise interactions (DLPNO-CCSD(T)/cc-pVTZ, B3LYP-D4/6-31G(d,p) and PWPB95/def2-TZVP) and the electron density topological analysis (Espinosa–Molins–Lecomte correlation, EML). The nature and energy of intermolecular interactions are analyzed by these methods, and it is shown that the EML correlation significantly overestimates the contribution of O–H⋯N hydrogen bonds and fluorine-mediated interactions to the total energy of the molecule′s interactions and underestimates the contribution of weak C–H⋯O(N) hydrogen bonds and H⋯H interactions.

The [Pt(NH₃)₄]₃[Ta(C₂O₄)₄]₂·2H₂O (I) and [Rh(NH₃)₆][TaO(C₂O₄)₃]·2.5H₂O (II) double complex salts (DCSs) are prepared and characterized by single crystal XRD, powder XRD, and IR spectroscopy methods. Crystal data for I: P2₁/c space group, a = 7.4894(3) Å, b = 17.4414(5) Å, c = 15.4949(5) Å, β = 92.958(10)°, Z = 2. Crystal data for II: (Pbar{1}) space group, a = 7.8194(2) Å, b = 15.5143(5) Å, c = 15.8494(5) Å, α = 90.991(10)°, β = 92.096(10)°, γ = 101.549(10)°, Z = 2. Oxalic acid tantalum(V) solutions are studied by mass spectrometry; a number of complex forms in such solutions are established. Thermal decomposition processes of I and II in inert and reducing atmospheres are considered.

The interaction of 14-bromousnic acid with hydrazine dithiocarbamate is investigated. The reaction is found to proceed in two parallel paths: with modifying the bromoacetyl group into the 1,3,4-thiadiazine ring and the triketone fragment of the C ring into the pyrazole ring annelated to positions 1,2 or to 2,3 of the dibenzofuran core. Conditions are determined for the selective formation of one of the regioisomers in the structure of which the pyrazole ring is annelated to positions 1,2. It is revealed that this compound inhibits the activity of human DNA repair enzyme tyrosyl–DNA–phosphodiesterase 1 (TDP1) with a half-maximal inhibitory concentration of 1.25 µM, which enables its consideration as the basis for the synthesis of effective inhibitors of this enzyme - components of the antitumor drug.

The possibility is studied to obtain middle-entropy perovskite PbSc_1/4In_1/4Nb_1/4Ta_1/4O₃ by the sol-gel method from citric acid solutions containing F^– ions. According to synchrotron X-ray diffraction data, the synthesis passes through a low-temperature stage of forming a phase with the pyrochlore structure (500-600 °C). As the temperature increases (800 °C), this phase transforms into a phase with the perovskite structure. The composition of the synthesis product appreciably deviates from the set one and corresponds to formula Pb_1–0.9Sc_0.431±0.016In_0.142±0.014Nb_0.228±0.013Ta_0.199±0.005O_3–δF_δ. Indium, niobium, and tantalum concentrations are underestimated in it with regard to the volatility of their fluorides removed from the system at early stages of the xerogel formation during evaporation of the solution. The fluorine concentation decreases in the samples with increasing temperature due to high-temperature vapor phase hydrolysis. There is the optimal fluorine concentration (~0.04 at. % per PSINT mol) reached at 800 °C and stabilizing the perovskite structure. When the F^– concentration decreases up to zero after annealing at 1100 °C, perovskite almost completely transforms into pyrochlore.

A series of copper and zinc pentafluorobenzoate (pfb) and trifluoroacetate compounds with phosphorus-containing pyrrolidine derivatives are synthesized: [Cu(L₁–F)₂(CF₃COO)₂] (1, L₁–F - (3-(3-fluorobenzylidene)pyrrolidin-2-yl-)di(p-hexyl)phosphinoxide), [Cu(L₂–Cl)₂(CF₃COO)₂] (2, L₂–Cl - (3-(4-chlorobenzylidene)pyrrolidin-2-yl-)di(p-hexyl)phosphinoxide), [Cu(L₂–Br)₂(CF₃COO)₂] (3, L₂–Br - (3-(4-bromobenzylidene)pyrrolidin-2-yl-)di(p-hexyl)phosphinoxide), [Zn₂(L₂–Cl)₂(CF₃COO)₄] (4), [Zn₂(L₃–Et)₂(C₆F₅COO)₄] (5, L₃–Et - (1-(ethylsulfonide)pyrrolidin-2-yl)diphenylphosphinoxide), [Cu₂(L₃–Et)₂(C₆F₅COO)₄]·2MeCN (6), [Cu₂(L₃–Vi)₂(C₆F₅COO)₄] (7, L₃–Vi - (1-(vinylsulfonyl)pyrrolidin-2-yl)diphenylphosphinoxide). The coordination compounds obtained are characterized by single crystal X-ray diffraction, IR spectroscopy, and the CHNS analysis. The structures and crystal packings of the obtained complexes are studied in detail and the main structure-forming non-covalent interactions are revealed in the crystals.

Samples of cobalt ferrite CoFe₂O₄ are synthesized by coprecipitation: 1) from iron(III) and cobalt(II) nitrates followed by calcination of the obtained precipitate at 500 °C and 1000 °C; 2) from iron(III) nitrate and cobalt(II) chloride followed by calcination of the obtained precipitate at 500 °C. They are characterized by powder X-ray diffraction, scanning electron microscopy, X-ray energy dispersive and Mössbauer spectroscopy, and in situ magnetometry. Before calcination the samples exhibit superparamagnetism; and the phase formation is not completed. The calcination stage is needed to reach the crystalline state. The crystalline sample with unit cell parameter a = 8.386 Å forms after calcination at 1000 °C. Magnetometric measurements show the formation of a phase with the Curie temperature close to 500 °C. According to the Mössbauer spectroscopic data, the cation distribution in the sample can be described as Fe_0.53Co_0.47 [Fe_1.47Co_0.53]O₄. At –196 °C and 23 °C the calculated sizes of magnetic domains are 3.0 nm and 2.5 nm respectively.

Polymeric silver terephthalate [Ag₂(ter)] (1) (ter^2– = O₂C-C₆H₄-CO₂) and malonate [Ag₂(malo)] (2) (malo^2– = O₂C-CH₂-CO₂) are obtained and characterized by the elemental analysis and IR spectroscopy. When heated, these complexes dissolve in pyridine (py) or its derivatives. The crystals of MOFs [Ag(py)₄](Hter) (3a), [Ag₂(3-Me-py)₄(ter)] (4a), [Ag₂(3-Me-py)₄(malo)] (5a) are obtained from solutions. Single crystals are analyzed by X-ray diffraction, however, they rapidly decompose with a loss of py molecules if they are isolated from the mother liquor or slightly heated. Stable products of 3a, 4a, 5a desolvation and decoordination are [Ag₂(py)_2.8](Hter)₂ (3), [Ag₂(3-Me-py)_1.3(ter)] (4), [Ag₂(3-Me-py)_2.9(malo)] (5).