Vol 43, No 11 (2017)

The results on the synthesis and study of the crystal structures of compounds based on anionic fragments {VO(Cbdc)₂}^2– formed by oxovanadium(IV) (vanadyl, VO²⁺) and two chelate-bound anions of cyclobutane-1,1-dicarboxylic acid (H₂Cbdc = C₄H₆(COOH)₂) are presented. The use of ammonium cation NH₄⁺ as a counterion in the synthesis leads to the formation of the mononuclear complex (NH₄)₂[VO(Сbdc)₂(H₂O)] · 2H₂O (I). In the case of K⁺ cation, compound [K₄(VO)₂(Сbdc)₄(H₂O)₄]_n (II) with the 3D polymeric crystal structure is formed. The reaction of compound II with Mg(NO3)2 · 6H₂O in an aqueous solution involves the partial substitution of K⁺ by Mg²⁺ cations to form 1D polymeric compound {[KMg_0.5(VO)(Сbdc)₂(H₂O)_6.5] · 3H₂O}_n (III), while a similar reaction of compound I does not afford the product of substitution of NH₄⁺ by Mg²⁺ cations (CIF files CCDC 1551021–1551023 for compounds I–III, respectively).

The binuclear copper(II) complex with bis-azomethine, viz., the product of condensation of 1,3-diaminopropanol-2 with 4-hydroxy-3-formylcoumarin (H₃L), of the composition [Cu₂L(μ₂-CH₃COO)] (I) is synthesized and studied. Complex I is characterized by the exchange interaction of the antiferromagnetic type (2J =–112 cm^–1), which is switched to the ferromagnetic one (2J = +106 cm–1) after the recrystallization of the complex from dimethyl sulfoxide (DMSO) to form solvate [Cu₂L(μ₂-CH₃COO)(μ₂-DMSO)] · 0.5DMSO (II). The structure of solvate II is studied by X-ray diffraction analysis (CIF file CCDC no. 982198). The difference in the exchange character is explained by the stabilization by the μ₂-coordinated DMSO molecule of a distorted (roof-shaped type) conformation of the polydentate ligand and the complex as a whole, unlike the symmetric conformation characteristic of the nonsolvated complex. The data obtained are compared with those on similar compounds synthesized earlier and with the quantum chemical modeling results for the exchange interaction in the framework of the DFT-BS approximation.

Two new Zn(II) and Co(II) compounds obtained by reactions of tetrafluoroborates of these metals with 1,3,5-benzenetricarboxylic (trimesic) acid (H₃Btc) and 1,3-bis(pyridyl)propane (Bpp) as an additional ligand were studied by X-ray diffraction. The formation of coordination polymers of various dimensionality, {[Zn₄(Bpp)₄(HBtc)₃((Me)Btc)]{(Me)₂HBtc} · 2H2O}_n (I), 1D, and {[Co₄(μ₃-OH)₂(Btc)₂(H₂O)₈] · 4(H₂O)}_n (II), 2D (CIF files CCDC no. 1552167 (I), 1552168 (II)) was demonstrated. Since H3Btc is partially methylated during the reaction, in I, this acid is stabilized in three forms: HBtc^2–, (Me)Btc^2–, and (Me)₂HBtc. The tetrahedral Zn(II) coordination polyhedron is formed by the N₂O₂ set of donor atoms: the O atoms belong to two different carboxylate ligands, HBtc^2– and (Me)Btc^2–, while the N atoms belong to two Bpp ligands. In II, the Bpp ligand is not incorporated in the complex and H₃Btc is coordinated to five metal atoms as a triply deprotonated ligand. Two carboxyl groups are coordinated to Co atoms as bidentate bridging ligands, while the third group is monodentate. The octahedral coordination polyhedra of Co(II) atoms in II are supplemented by terminal water molecules and μ₃-bridging OH^– groups.

Herein the synthesis of 3-(3,5-Dimethyl-1H-pyrazol-1-yl)butanal oxime (L) and its complex formation with PdCl₂ is studied. IR and 1Н NMR spectroscopic methods as well as X-ray diffraction analysis (СIF file CCDC no. 1531058) elucidate that the nitrogen atoms N(4) and N(15) from pyrazole and imine group of oxime respectively, participate in coordination with PdCl₂. Moreover, primarily thermal stability test shows that [PdCl₂(L)] complex (I) is quite stable at moderate temperatures and intense decomposition of latter occurs ca 200–210°C. As a consequence of thermal decomposition, both volatile ligand and its dehydration by-product 3-(3,5-dimethyl-1H-pyrazol-1-yl)butanenitrile are formed. Afterwards, the anticonvulsant properties of PdCl₂, L, and I are of interest and well studied in this section.

Two new oxidovanadium(V) complexes, [VO(L¹)(L)] (I) and [VO(L²)(L)] (II), where L¹ and L² are the dianionic form of N'-(2-hydroxy-5-methoxybenzylidene)pivalohydrazide (H₂L¹) and N'-(2-hydroxy-3-methoxybenzylidene)pivalohydrazide (H₂L²), respectively, and L is the monoanionic form of 8-hydroxyquinoline (HL), were prepared and characterized by elemental analysis, infrared and electronic spectra, and ¹H NMR spectra. Structures of the complexes were further confirmed by single crystal X-ray determination (CIF files CCDC nos. 1477854 (I), 1477856 (II)). H₂L¹ and H₂L² coordinate to the V atoms through the phenolate O, imino N, and enolate O atoms. 8-Hydroxyquinoline coordinates to the V atoms through bidentate ON donor set. The V atoms of the complexes are in octahedral coordination with the oxo group furnished the octahedral geometry. The complexes show effective antibacterial activity against Bacillus subtilis.

A new compound {[Cu(En)₂]₂V₂O₇} · 4H₂O (I) (En = ethanediamine) has been synthesized by the combination of hydrothermal and solvent evaporation method and characterized by single-crystal X-ray diffraction (CIF file CCDC no. 1450218), IR, UV-Vis spectra, thermogravimetric analysis, powder X-ray diffraction, and fluorescence analysis. Crystal data for I: C₈H₄₀Cu₂N₈O₁₁V₂, Mr = 653.44, orthorhombic, space group Cmca, a = 18.559(11), b = 17.583(11), c = 7.600(6) Å, V = 2480(3) ų, and Z = 4. Interestingly, two [Cu(En)₂]²⁺ coordination cations are bridged by the [V₂O₇]^4– unit to build up a neutral framework compound.