Home – Home – Jornals – Journal of Structural Chemistry 2013 number 6

Spin transition theory is developed for periodic chains with two and more exchange clusters in a unit cell. A general expression is obtained for the effective magnetic moment of a unit cell μ_eff with several exchange clusters. For heterospin complexes Cu(hfac)₂L^R characterized by chains with the head-to-head motif a two-site approximation for the statistical sum of the Cu²⁺ Jahn – Teller paramagnetic center Cu²⁺ with spin 1/2 is proposed, within which a comparison with the available experimental data is performed. It is shown that the model developed describes both smooth and abrupt (cooperative) spin-crossover cases for the chains of three-spin exchange clusters.

The results of pseudopotential calculations of the band structure and related electronic and optical properties of quasi-binary (GaP)_{1– x}(ZnSe)_x crystals in the zinc blende structure are presented. Trends in bonding and ionicity are discussed in terms of electronic charge densities. Moreover, the composition dependence of the refractive index and dielectric constants are reported. The computed values are in reasonable agreement with experimental data. The results suggest that for a proper choice of the composition x , (GaP)_{1– x}(ZnSe)_x could provide more diverse opportunities to achieve the desired electronic and optical properties of the crystals which would improve the performances of devices fabricated on them.

2,3-Trimethylene-3,4-dihydroquinazoline shares the heterocyclic core with natural compounds and synthetic drugs. The hydrochloride of the compound forms excellent dihydrate crystals which have allowed us to collect high-resolution X-ray diffraction data and obtain the experimental charge density. The solid may be understood as built up from pairs of heterocyclic cations and chloride anions; a direct hydrogen bond links the halide to the formally cationic pyrimidine NH group. The hydrate water molecules interact with the anions, forming an infinite chain along the crystallographic a axis between the stacks of the heterocyclic cations. Based on the experimental charge density, a dipole moment of 16.1 Debye is calculated for a pair of the hydrogen-bonded quinazolinium cation and the chloride anion in the extended crystal structure.

The structures of indole, skatole, and ethanole complexes with water molecules are calculated by the DFT method. Radial and angular dependences of hydrogen bridge parameters on the number of water molecules are analyzed. Two models are determined which enable the study of the reason for the hydrophobicity of indole and skatole. Frequencies and intensities of absorption bands corresponding to stretching vibrations of the NH bond of indole, skatole, and ethanol in complexes with water are compared. It is shown that the main reason for the domination of the hydrophobic component over the hydrophilic one is the taking into account of the interaction of water molecules with the aromatic system of indole and skatole, finally resulting in a substantial decrease in the HB strength.

By non-empirical ab initio quantum chemical calculation the spatial structure of 1,1'-divinyl-2,2'-diimidazolyl is determined and the formation of intramolecular hydrogen bonds of the С–H···N type in it is established. It is evidenced by energy preference for the conformation in which there is a short contact between the α-proton of the vinyl group and the endocyclic nitrogen atom (2.28 Å), creating favorable conditions for the formation of a six-membered chelate cycle. An analysis of the topological characteristics of the electron density and the reduced electron density gradient also give evidence in favor of the formation of a weak intramolecular hydrogen bond C–H···N. The estimation of the hydrogen bond energy by the Espinosa method results in a value below 3 kcal/mol.

A new method is developed to obtain nanosized catalytic Pt–Sn/TiO₂ coatings on the inner surface of a capillary microreactor during adsorption of polynuclear carbonyl Pt–Sn complexes on mesoporous TiO₂. Titanium oxide sol prepared in the presence of template (Pluronic F127 surfactant) is supported in dynamic mode. Pt–Sn bimetallic catalysts with an average particle size of 1.5-2 nm are synthesized by adsorption of the bimetallic [Pt₃(CO)₃(SnCl₃)₂(SnCl₂×H₂O)]_n^2n¯ complex followed by thermal treatment. Physicochemical properties of samples (thickness, structure and morphology, chemical composition of the material, electronic state, specific surface area, pore volume and size distribution) are characterized by a set of methods (HR TEM, SEM, powder XRD, XRF, XPS, low-temperature nitrogen adsorption). Conditions to prepare the uniform non-peelable Pt–Sn/TiO₂ coating on the inner surface of a silica capillary with good adhesion are determined. To increase the TiO₂ thickness, multilayered TiO₂ films are synthesized by layer-by layer deposition. The coating thickness is found to increase with an increase in the capillary diameter. The coating of a capillary with a diameter of 0.55 mm after 14-fold deposition is characterized by a thickness of 2 mm and an average pore size of 5.4 nm. The solvent effect on the adsorption of Pt–Sn carbonyl complexes into the TiO₂ support is studied. The amount of the adsorbed complex increases in the following order: ethanol < acetone ~ tetrahydrofuran. The physicochemical properties of the active component (surface concentration, dispersion, and composition) can be fine-tuned by varying the deposition method, precursor concentration in the initial solution, and temperature conditions of activation treatment. The catalyst activity in citral hydrogenation was 0.06-0.54 min^–1, with the selectivity with respect to unsaturated alcohols reaching 90% at citral conversion above 95%.

FT-IR and FT-Raman spectra of 1-cyclopropylpiperazine (1cppp) are experimentally examined in the range 4000—200 cm^–1. The optimized geometric parameters, conformational equilibria, normal mode frequencies and corresponding vibrational assignments of 1cppp C₇H₁₄N₂ are theoretically examined by means of B3LYP hybrid density functional theory (DFT) with the 6-31++G(d,p) basis set. Based on the potential energy distribution (PED) reliable vibrational assignments are made and the thermodynamics functions, highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO) of 1cppp are predicted. Calculations are performed for four different conformations in two point groups of 1cppp in the gas phase. A comparison between the experimental and theoretical results indicates that the B3LYP method is able to provide satisfactory results for the prediction of vibrational frequencies, structural parameters, and assignments. Furthermore, the C _s (equatorial-equatorial) point group is found as the most stable conformer of 1cppp.

A new Schiff base ligand N,N'-bis(2,4-dihydroxybenzylidene)-1,2-diaminobenzene [=H₂L] and its Cu(II) complex [Cu(L)] are synthesized and characterized by IR, UV-Vis, NMR, mass spectrometry and elemental analysis. Also, the computational prediction of optimized geometries, IR spectra and NMR chemical shifts is performed using the density functional theory (DFT) method. The DFT optimized geometry of the ligand is not planar, so the three benzene rings are located in separate planes. The phenolic protons are engaged in the intramolecular hydrogen-bonding interactions. In the optimized geometry of the square comlex, dianionic L^2– acts as a tetradentate ligand, which occupies four coordination positions in the N, N, O^–, O^– manner. The consistency between the calculated and experimental results confirms the validity of the optimized structures for the H₂L ligand and its Cu complex.

In this work, a 3,3'-dihydroxy-4,4'-[1,2-cyclohexanediyl bis (nitrilomethylidyne)]-bis-phenol [=H₂L] Schiff-base ligand and its Mn(II) complex [Mn(L)(H₂O)₂] are newly synthesized and characterized by elemental analysis, IR and NMR spectroscopies. Also the geometry optimizations, assignment of the IR bands and NMR chemical shifts are computed using the density functional theory (DFT) method. The DFT optimized geometry of the ligand is not planar; each of the cyclohexane and two benzene rings are located in separate planes. The phenolic protons are engaged in the intramolecular-hydrogen-bonding interactions with azomethine nitrogen atoms. In the optimized geometry of the octahedral Mn²⁺ complex, the dianionic L^2– acts as a tetradentate ligand in the N, N, O^–, O^– manner, where the coordinating atoms occupy the four equatorial positions. The two axial positions are occupied by two H₂O ligands. The theoretical and experimental results are in good agreement, confirming the validity of the optimized geometries for the H₂L ligand and its Mn complex.

A crystallographic analysis is performed for the structures of TlCu₂S₂, TlCu₇S₄, TlTaS₃, TlIn₃S₅, TlIn₅S₈, and TlCr₂V₃S₈. In them the Tl⁺ cation is included in anion sublattices and stabilizes their regularity. The cation sublattices are substantially distorted and have additional conjugation to the anionic positions of the thallium cations. The monoclinic structures (the last three) have geometrically similar anionic and cationic “forced skeletons,” while in tetragonal (the first two) and orthorhombic symmetries they are modified by symmetry restrictions.

By single crystal X‑ray diffraction the crystal structure of a series of [М (NH₃)₅Cl]WO₄ (М = Cr, Rh) complex salts is determined. The features of thermal expansion of the single crystal of [Cr(NH ₃) ₅Cl]WO ₄ are studied by low- and high-temperature X‑ray diffractometry in the temperature range from –173°C to +127°C. It is shown that with an increase in the temperature, W–O distances and ∠O–W–O bond angles equalize and the average W–O distances decrease by 0.012 Å. The thermal properties of the salts in different gaseous atmospheres are examined and the phase composition of the obtained products is studied.

By interaction of trimethylplatinum(IV) iodide with phenyl-containing β-diketonates, the volatile monomeric complexes of trimethylplatinum(IV) based on benzoyltrifluoroacetone (Hbtfa) and benzoylacetone (Hbac) of the composition (CH₃)₃Pt(btfa)H₂O (I) and (CH₃)₃Pt(bac)Py (II) are obtained. Synthesis of the complexes is described; data of elemental analysis and IR spectra are reported; thermal characteristics are studied by thermogravimetry. For the first time, a single crystal X-ray diffraction study of complexes (I), (II), and the initial tetrameric complex [(CH₃)₃PtI]₄ (III) is performed.

X-ray crystallography is used to investigate heteromolecular crystals of 3,6-bis(3,5-dimethylpyrazole-1-yl)-1,2,4,5-tetrazine with NH-donating azole derivatives. The effect is studied of the structure of azole on molecular packing in the crystal and the characteristics of covalent bonds in the molecule of 3,6-disubstituted tetrazine. The distribution of electron density critical points inside crystal cells is analyzed to identify and quantitatively describe the intermolecular interactions underlying the formation of lateral and stacking motifs.

A new complexing agent the “asymmetric” ethylenediamine-N,N-di-3-propionic acid (as.EDDP) is obtained. The crystal structure of the new compound is determined by single-crystal X-ray diffraction. С₈Н₁₆N₂O₄×Н₂О crystals are monoclinic; space group Р 2₁/c , а = 12.7416(4) Å, b = 6.5470(2) Å, c = 12.1908(4) Å, β = 93.100(1)°, Z = 4, ρ_x = 1.454 mg/m³, and R₁(I > 2.0σ( I )) = 0.0326. In the solid form, the as.EDDP molecule has a double betaine structure. The intramolecular hydrogen bonds with the betaine proton of the tertiary nitrogen atom are formed with the participation of one oxygen atom of the carboxyl group of each 3-propionic fragment, which forms two N(1)–H(1N)-bonded six-membered H-cycles. The intermolecular hydrogen bonds are formed between the three hydrogen atoms of the protonated primary nitrogen atom and the oxygen atoms of the 3-propionic fragments of three other as.EDDP molecules. The water molecule participates in the formation of intermolecular hydrogen bonds with the oxygen atom of one carboxyl group of the molecule.

Reactions of E -4-ferrocenylpent-3-en-2-one with S -methyldithiocarbazate or S -benzyldithiocarbazate result in the formation of methyl 5-ferrocenyl-3,5-dimethyl-2-pyrazoline-1-dithiocarboxylate (1) or benzyl 5-ferrocenyl-3,5-dimethyl-2-pyrazoline-1-dithiocarboxylate (2). The single crystals of both products are obtained and their structures are identified by X-ray diffraction method with triclinic P -1 space groups. The cell parameters for compound 1 are as follows: a = 7.7029(8) Å, b = 10.1631(11) Å, c = 10.7305(12) Å, α = 101.3270(10)°, β  = 90.6740(10)°, γ = 94.8390(10)°, and V = 820.40(15) Å ³. For compound 2, the crystallographic data are: a = 7.953(3) Å, b = 10.970(5) Å, c = 12.534(3) Å, α = 84.718(5)°, β  = 81.651(3)°, γ = 76.274(4)°, and V = 1049.1(7) Å ³.

A new terpenoid-like bischalcone (1E,4E)-1-(4-nitrophenyl)-5-(2,6,6-trimethylcyclohex-1-enyl)-penta-1,4-dien-3-one was synthesized from a b-ionone and 4-nitrobenzaldehyde by Claisen—Schmidt condensation reaction and its structure was determined by single crystal X-ray diffraction analysis. Additionally, this compound was featured by powder X-ray diffraction, ¹H, ¹³C NMR and IR spectroscopy techniques. The molecule in the asymmetric unit showed disordered occupancy sites over two positions for the trimethylcyclohexene atoms. These two conformations were related by a rotation of about 180° around the axis of the C—C bond linking the six-membered ring and the olefin carbons. Single-molecule calculations using the DFT method have strengthened this structural finding, since our theoretical approaches also suggest two well-defined conformations of similar energies which resemble the molecular geometries determined by X-ray diffraction. Furthermore, the inspection of the crystal packing revealed that the hydrogen bonding patterns are different for each conformation of the compound reported here.

Two organic-inorganic hybrid compounds (C ₅H ₁₄N ₂)[Cd(H ₂O) ₆](SO ₄) ₂ (I) and R-(C ₅H ₁₄N ₂) [Cd(H ₂O) ₆](SO ₄) ₂ (II) are synthesized by the slow evaporation method and characterized by single crystal X-ray diffraction, thermogravimetry, temperature-dependent X-ray diffraction, and infrared spectroscopy. The first compound crystallizes in the centrosymmetric space group P 2 ₁/ n with the following unit cell parameters: a = 6.6208(2) Å, b = 10.6963(3) Å, c = 12.9318(4) Å, V = 893.05(6) Å ³, and Z = 2. Its structure is solved by direct methods and refined by the least-squares analysis [ R ₁ = 0.0389 and wR ₂ = 0.0821]. This compound shows a crystallographic disorder II destroys the inversion symmetry and leads to a fully ordered structure. Indeed, compound II crystallizes in the non-centrosymmetric space group P 2 ₁ with the following unit cell parameters: a = 6.6306(1) Å, b = 10.7059(2) Å, c = 12.9186(1) Å, V = 894.67(2) Å ³, and Z = 2. The crystal structure of both compounds is built from isolated _{anions, disordered 2-methylpiperazinediium, (C 5H 14N 2) ²⁺ in compound I or R-2-methylpiperazinediium R-(C 5H 14N 2) ²⁺ in compound II, and divalent metal cations surrounded by six water molecules. These different entities are connected together only by a 3D hydrogen bond network. The thermodiffractometry and the thermogravimetric analyses indicate that the decomposition of the supramolecular precursors proceeds through several stages leading to cadmuim oxide.}

Crystal structure of a complex salt [CoEn₃]₂(W₇О₂₄)×6Н₂О is determined by X-ray crystallography. Powder X-ray diffraction is applied for the phase identification of the products of thermal decomposition of the salt in the helium atmosphere.

The reaction of diethyl-4-hydroxy-4-methyl-2-phenyl-6-oxocyclohexane-1,3-dicarboxylate with N-isobutylethylenediamine is performed and the crystal structure of this reaction product (diethyl-1-isobutyl-9-hydroxy-9-methyl-7-phenyl-1,4-diazaspiro[4,5]decane-6,8-dicarboxylate) is determined by X-ray crystallography.

Two new chlorido-bridged dinuclear copper(II) complexes [Cu ₂Cl ₂(L ¹) ₂] (1) and [Cu ₂Cl ₂(L ²) ₂] (2), where L ¹ and L ² are the deprotonated form of Schiff bases 2-[1-(2-morpholin-4-ylethylimino)ethyl]phenol (HL ¹) and 2-[1-(2-piperidin-1-ylethylimino)ethyl]phenol respectively, are prepared and structurally characterized by elemental analysis, IR spectra, and single crystal X-ray crystallography. Complex 1 crystallizes in the monoclinic space group P 2 ₁/ c with unit cell dimensions a = 8.0816(2) Å, b = 19.1780(3) Å, c = 9.6757(3) Å, b = 106.465(2)°, V = 1438.13(6) Å ³, Z = 2, R ₁ = 0.0409, and wR ₂ = 0.1085. Complex 2 crystallizes in the monoclinic space group P 2 ₁/ c with unit cell dimensions a = 7.7640(10) Å, b = 19.930(3) Å, c = 9.628(2) Å, b = 103.890(3)°, V = 1446.2(4) Å ³, Z = 2, R ₁ = 0.0634, and wR ₂ = 0.1316. Each Cu atom in the complexes is coordinated by three donor atoms of the Schiff bases and by two bridging Cl atoms, forming square pyramidal geometry. The Cl anions are preferred bridging groups for the construction of dinuclear copper complexes with tridentate Schiff bases.

Two new solvated benzohydrazone derivatives N'-(4-hydroxy-3-nitrobenzylidene)-3-methylbenzohydrazide—methanol—water (2/1/1) 2(C ₁₅H ₁₃N ₃O ₄)×CH ₃OH×H ₂O (1) and N'-(4-dimethylaminobenzylidene)-3-methylbenzohydrazide methanol monosolvate C ₁₇H ₁₉N ₃O×CH ₃OH (2) are prepared and characterized by elemental analysis, ¹H and ¹³C NMR, and single crystal X-ray diffraction. Compound 1 crystallizes in the monoclinic space group P2 ₁/ c with unit cell dimensions a = 17.084(2) Å, b = 12.706(1) Å, c = 15.412(1) Å, β = 113.207(1)°, V = 3074.1(4) Å ³, Z = 4, R ₁ = 0.0567, and wR ₂ = 0.1209. Compound 2 crystallizes in the monoclinic space group P2 ₁/ n with unit cell dimensions a = 15.058(1) Å, b = 6.658(1) Å, c = 17.211(2) Å, β = 94.189(2)°, V = 1720.8(3) Å ³, Z = 4, Rsub>1 = 0.0611, and wR ₂ = 0.1594. X-ray diffraction indicates that the asymmetric unit of 1 contains two independent benzohydrazone molecules, one methanol and one water molecules. The asymmetric unit of 2 contains one benzohydrazone molecule and one methanol molecule. Benzohydrazone molecules of the compounds display trans configurations with respect to the C=N double bonds. The crystal structures of the compounds are stabilized by hydrogen bonds and weak π⋯π interactions.

Two new aroylhydrazones 3-bromo-N'-(2-hydroxy-5-methoxybenzylidene)benzohydrazide (1) and 4-hydroxy-3-methoxy-N'-(2-hydroxy-5-methoxybenzylidene)benzohydrazide (2), derived from 5-methoxysalicylaldehyde, are prepared and determined by means of infrared and ¹H NMR spectroscopy and single crystal X-ray diffraction. Compound 1 crystallizes in the monoclinic space group P2 ₁/ n with a = 5.9406(7) Å, b = 31.833(3) Å, c = 7.6460(8) Å, β = 94.522(4)°, V = 1441.4(3) Å ³, Z = 4. Compound 2 crystallizes in the monoclinic space group P2 ₁/ c with a = 14.3471(9) Å, b = 11.3893(7) Å, c = 9.6853(6) Å, β = 94.063(2)°, V = 1578.6(2) Å ³, Z = 4. Both molecules have very similar bond lengths and angles. The crystal structures of both compounds are stabilized by N—H⋯O and O—H⋯O hydrogen bonds as well as π⋯π interactions.