Journal of Structural Chemistry最新文献

The following homo- and mixed-anionic Eu(III) complexes with anions of benzoic (bz) and pentafluorobenzoic (pfb) acids and quinoline (quin) or phenanthridine (phtd) molecules are studied: (Hphtd)₂[Eu₂(H₂O)₂(pfb)₈] (1), [Eu(EtOH)(pfb)₂(bz)]_n·n(phtd) (2), [Eu(MeOH)(pfb)₃]_n·n(quin) (3), [Eu₂ (H₂O)₈(pfb)₆]·6(quin)·2(H₂O) (4), and [Eu(H₂O)₂(bz)₃]_n··1.5n(quin)·n(MeCN) (5). The influence of various factors on the composition and structure of new compounds is revealed by varying the ratios of reactants and synthesis and crystallization conditions. The complexes are characterized by XRD, IR spectroscopy, and CHN analysis. The structure and crystal packing of the complexes is studied in detail. The crystal packaging is mainly stabilized by π⋯π, C–H⋯F, and C–F⋯π interactions.

Issues related to the procedure of optimizing the calibration of modern area-detector diffractometers using reference single crystals are considered. It is shown that the accuracy of measuring the unit cell parameters (UCPs) of polycrystalline samples in the Debye–Scherrer scheme can be improved by considering the eccentricity. The procedure is tested on a CeO₂ polycrystalline sample (SRM674b). The value obtained for the cubic unit cell parameter a = 5.4117(2) Å differs from the reference one by 0.0002 Å, in agreement with the experiment′s absolute error. The XRD certification of a promising Y₂O₃ XRD standard is performed (TU 48-4-524-90; ItO-V grade; 99.999% purity; cubic unit cell parameter a is 10.6047(3) Å).

Potassium, rubidium, and cesium thenoyltrifluoroacetonates (ttfac^– = C₄H₃SCOCHCOCF₃) are prepared and characterized (elemental and powder XRD, IR and NMR spectroscopy). The structure of new {K(H₂O)(ttfac)}_∞ and {Rb(ttfac)}_∞ compounds is determined by XRD (the rubidium complex is shown to be isostructural to its cesium analogue) and is shown to be layered due to M–O and M–F contacts. The presence of water in the structure diminishes the anion′s denticity. The immediate environment of K⁺, consisting of oxygen and fluorine atoms, is typical for potassium β-diketonates (coordination number = 8), whereas that of Rb⁺/Cs⁺ is an unusual coordination polyhedron with a coordination number of 7. The layers in the structures of anhydrous {M(ttfac)}_∞ are connected by C–H⋯π interactions. The structural organization of the studied complexes is compared with that of their benzoyltrifluoroacetonate analogs. Thermal properties of M(ttfac)(H₂O)_x are studied by TG-DSC with a mass spectrometric analysis of evolved gases. It is shown by powder XRD that the decomposition of potassium, rubidium, and cesium thenoyltrifluoroacetonate in air leads to the formation of corresponding sulfates as the main decomposition products.

New mixed calcium oxo-salts with the general formula Ca₉Sm(PO₄)_7(1–x)(VO₄)_7x and the β-Ca₃(PO₄)₂ structure are prepared. It is studied how ferroelectric, optical, and luminescent properties of these compounds are affected by the substitution of (text{PO}_{4}^{3-}) by (text{VO}_{4}^{3-}). Successful introduction of (text{VO}_{4}^{3-}) groups into the structure is confirmed by Raman and IR spectroscopy. The formation of a continuous series of solid solutions is established, and the presence of regions with different space groups is demonstrated by the second-harmonic generation method. It is shown that a centrocymmetric region with the (Rbar{3}c) space group is formed for 0.2 ≤ x ≤ 0.4 in Ca₉Sm(PO₄)_7(1–x)(VO₄)_7x. It is established that the photoluminescence intensity depends on the changes in the anionic part of the structure: for x = 0.2, the integrated intensity increases by 10% with respect to the Ca₉Sm(PO₄)₇ phosphate and by 110% with respect to the Ca₉Sm(VO₄)₇ vanadate. The absorption edge of the diffuse reflectance spectra shifts towards the visible region with increasing vanadate content. The bandgap decreases from 4.5 eV for Ca₉Sm(PO₄)₇ to 2.8 eV for Ca₉Sm(VO₄)₇. Due to the strong luminescence of Sm³⁺ ions in the red visible spectrum, the studied series can be considered as color correcting luminescent materials for LED lighting.

Complexes {(3,5-MePy)₂(CH₂)_n}₃[Bi₂Br₉]₂ (n = 2 (1), 5 (2)) are obtained by the reaction of bismuth oxide with salts of various doubly charged cations based on 3,5-dimethylpyridine in concentrated HBr, and they are structurally characterized by X-ray diffraction. The features of intermolecular contacts in the crystal structure are considered.

Silver(I) coordination polymers are considered as components of antibacterial systems and precursors for preparing metallic and oxide nanoparticles for medical purposes. Mixed ligand complexes [Ag₂(CH₃CN)(L)₂]_∞ (L = ofhac (1,1,1,5,5,6,6,6-octafluoropentane-2,4-dionate), ptac (1,1,1-trifluoro-5,5-dimethylhexane-2,4-dionate), hfac (1,1,1,5,5,5-hexafluoropentane-2,4-dionate) are obtained by crystallization of respective silver(I) β-diketonates from acetonitrile or by direct neutralization of Ag₂O with β-diketone in this solvent, and their structures are analyzed by single crystal X-ray diffraction. The compounds with L = ofhac, hfac are additionally characterized by NMR spectroscopy. The comparison of structures of the complexes with isoformula analogues shows that the formation of polymeric chains is characteristic of all compounds where structural blocks Ag(L)₂ with chelating β-diketonate ligands are linked in pairs by Ag–C_α bonds with the methine carbon atom and are further linked by two silver atoms coordinating the solvent and having the {AgO₂C_αN} environment. The Ag–O, Ag–C_α, and Ag–N bond lengths vary in the ranges of 2.30-2.49 Å, 2.33-2.44 Å, and 2.17-2.23 Å respectively. The thermal properties of the complexes are investigated by the thermogravimetric analysis: complexes with fluorinated ligands L = hfac, ofhac are more thermally stable, and for L = ptac the step of acetonitrile removal is distinguished.

The distribution character and supramolecular aggregation of the enzyme - recombinant lipase (rec-Lip) on the surfaces of carbon adsorbents, such as multiwalled carbon nanotubes (MWCNTs) and pyrocarbon supports (Sibunit^TM, activated carbon) are examined by small angle X-ray scattering (SAXS) and scanning electron microscopy (SEM) techniques. The SAXS studies show that rec-Lip molecules aggregate on the carbon surface with the formation of nanoparticles with sizes from 4 nm (monomers) to 26 nm (aggregates of more than 10 molecules). SEM images demonstrate that not only single round nanoparticles with a size more than 20 nm but also complex branched aggregates formed by short fibrils of single nanoparticles are observed on the surface. It is revealed that the enzyme activity of biocatalysts prepared by rec-Lip adsorption on carbon supports has the minimum value if the enzyme is in the monomeric form. Information about the distribution character of the immobilized enzyme on the adsorbent surfaces and about its supramolecular aggregation is not only of the fundamental value for heterogeneous biocatalysis, but are also of scientific and practical value because these processes govern the properties of biocatalysts, primarily, their enzyme activity.

Two new copper(II) complexes, [Cu₂(L^a)₂(OAc)₂]·2H₂O (1) and [Cu(L^b)₂] (2), where L^a and L^b are the deprotonated monoanionic form of 5-bromo-2-(ethylaminoethylimino)methyl)phenol (HL^a) and 5-bromo-2-cyclohexyliminomethylphenol (HL^b), respectively, have been synthesized and characterized by elemental analysis, infrared and electronic spectroscopy. Structures of both complexes were further determined by single crystal X-ray diffraction. Complexes 1 and 2 were synthesized from copper acetate with HL^a and HL^b, respectively in methanol. The Cu atoms in complex 1 are in octahedral coordination, while that in 2 is in square planar coordination. The two complexes have high catalytic property for the epoxidation of styrene, with conversions over 90% and selectivity over 85%.

Structural and sensing characteristics of zinc(II) 2,11,20,29-tetra-tert-butyl-2,3-naphthalocyanine (ZnNc(tBu)₄) films are studied. The chemiresistive sensing response of ZnNc(tBu)₄ films to ammonia in concentrations below the threshold limit value (TLV) in the working zone′s air is considered for the first time. It is shown that the annealing of ZnNc(tBu)₄ films in air at 250 °C for 3 h causes a phase transition to a stable high-temperature β-phase, increases the crystallite size, and enhances the sensing response to ammonia by 40-45 times, depending on its concentration.

A 3D metal–organic framework [Mn₄(2,5-I-bdc)₄(DMF)₄]·0.5DMF (1) is prepared by the reaction of MnCl₂·4H₂O with H₂(2,5-I-bdc) (2,5-diiodoterephthalic acid) and is structurally characterized. Thermal stability and luminescent properties (blue emission) of 1 are studied.