Journal of Structural Chemistry最新文献

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.

(2R,3R)-5-(2-(Chloroacetoxy)-2-(3,4-diacetoxyphenyl)-4-oxochroman-3,7-diyl diacetate containing two symmetrically independent molecules in the crystal unit cell is analyzed by single crystal X-ray diffraction. Molecular coordination numbers are studied in the crystal structure together with the topology of nets of intermolecular contacts. Intermolecular interaction energies are calculated and Hirshfeld surfaces of symmetrically independent molecules are analyzed.

Two salts of 1,2-diaminobenzene (dab) as acceptor with the trichloroacetic acid and 4-nitro-phthalic acid as donor were prepared and featured by the multiple analytical techniques of FTIR, elemental analysis (EA), and single crystal X-ray diffraction (SCXRD). The structural studies tell that the cation and anion are joined together by the energetic N⁺–H⋯O^– H-bonds due to the transfer of the proton from the donor to the acceptor. The salts show well resolved proton transfer bands in the regions where neither the donor nor the acceptor has any IR peaks. Spectrophotomeric and crystallographic studies have ensured the formation of 2:1/1:1 salts. The chief non-covalent interactions were counted via the Hirshfeld surface analysis. Despite variations of the carboxylic acids, there both bore the strong intermolecular N–HO H-bonds. Apart from the strong classical H-bonds, other supramolecular associates of O–O, Cl–C/Cl–O/Cl–Cl, CH–O, C–π, and π–π are also involved in the spatial stretchings. The anionic C7 chain was built at 2 by the O–H⋯O H-bonds. The roles of these non-covalent contacts are made clear. For the combination of the weak contacts, both salts exhibited the 3D views.