Vol 59, No 1 (2018)

New quantum-mechanical expressions are obtained for forces between the particles in molecules. A new interpretation of quantum transitions in molecular isomeric structures is proposed in terms of matrix elements of force operators.

A laser ion-molecule reaction interaction through both polarizability and dipole moment contribution leads to variation in the intersection point in potential energy surface crossings along the reaction path; the polarizability is maximum and the dipole changes its sign at s = 4 a.u., defining a virtual transition state. Using the gauge representation (electric field gauge) for a wave length λ = 20.6 μm, intensity I = 5×10¹² W/cm², I = 1×10¹³ W/cm², I = 3×10¹³ W/cm², we show here that we can create a laser-induced potential energy surface crossing along the reaction path (s = 7-8 a.u.). We illustrate such effects for the Li H + CH₃⁺ ↔ Li⁺ + CH₄ reaction which takes the form of inverted Morse (without a barrier) using ab initio methods for calculating the reaction path and electric properties of the ion-molecule reaction.

Crystal structures of N-furfuryl-N-(3-hydroxybenzyl)amine (1) and N-furfuryl-N-(4-hydroxybenzyl)amine (2) are reported. The furyl ring is coplanar with the C–N–C plane in 1 and perpendicular to the C–N–C plane in 2. Intermolecular O–H ⋯ N and C–H ⋯ O hydrogen bonds stabilize the crystal structures and play a crucial role in crystal packing. In addition, the molecular geometry and molecular vibrations are calculated using the DFT/B3LYP method with the 6-31G(d,p) basis set and the calculated geometrical parameters are correlated with the corresponding experimental data. The obtained HOMO and LUMO energies are negative, indicating that the compounds are in the stable state. FT-IR spectra of compounds 1 and 2 are measured in order to elucidate the spectroscopic properties of the compounds in the spectral range 4000–500 cm⁻¹. The recorded FT-IR spectral measurements are further supported by spectral simulations.

¹⁹F and ¹Н NMR methods were used to study ion mobility in M₆Sb₄(SO₄)₃F₁₂ (M = Rb, Cs, NH₄) and (NH₄)₂Sb(SO₄)F₃ complex antimony(III) sulfate fluorides with alkali cations and ammonium. The types of ionic mobility in these compounds were identified at 150–470 K.

A number of experimental techniques were used to study the changes in the atomic structure of copper(II) acetate-bipyridine under thermal decomposition between 25°C and 700°C to form copper-containing nanoparticles. The dynamics of structural changes during decomposition in a thermogravimetric chamber is compared with X-ray absorption spectra, IR spectra, and diffraction patterns for a sequence of annealing temperatures. The experimental results were used to construct theoretical structural models of the complex under thermal decomposition.

Molecular relaxation in binary systems LiNO₃–LIClO₄, NaNO₃–NaNO₂, and K₂CO₃–K₂SO₄ is studied using Raman spectroscopy. The relaxation time of ν₁(A) vibrations for NO₃⁻ and CO₃²⁻ anions is found to be shorter in LiNO₃–LIClO₄, NaNO₃–NaNO₂, K₂CO₃–K₂SO₄ than in LiNO₃, NaNO₃, K₂CO₃, respectively. Higher relaxation rate is explained by additional relaxation of excited vibrational states. This mechanism is associated with vibrational excitation of the second anion ( ClO₄⁻, NO₂⁻, SO₄²⁻ ) and “production” of a lattice phonon. This relaxation mechanism is possible when the difference between the frequencies of these vibrations falls into the region of fairly high density of states of the phonon spectrum.

Profiles of various membrane characteristics are traditionally calculated from the middle plane of the membrane towards the surface. In this approach, atomic positions near the membrane surface are determined inaccurately because, strictly speaking, the membrane is nonplanar and can have unevennesses or a variable thickness. However, the profile can also be calculated from the membrane surface. We propose to use the Voronoi boundary surface (a set of adjacent faces of Voronoi regions of membrane atoms and surrounding water) as this surface. It naturally divides the space between the membrane and water. Atomic density and empty intermolecular space profiles calculated relative to this surface reveal new features not seen when the middle plane is used.

In compliance with the hypothesis that the crystal structure stability increases with a decrease in the degrees of freedom of the constituent atoms, we propose quantitative criteria for structures: the ratio between the amount of the degrees of freedom of atoms to their number in a primitive cell (S) and the fundamental volume (V*)–the quotient of the cell volume (asymmetric unit) and the order of the symmetry group (M) that is the general position multiplicity. The crystallographic analysis of diamond and spinel structure types and their comparative analysis with stability and packing criteria are performed. The study uses the findings from the analysis of abundant less symmetrical tourmaline and apatite structure types which confirm the existence of standard frameworks–symmetrical spatial configurations of atomic sites that can be taken by atoms of various types.

Single crystals of Tl₂[NbCl₆] (1) and Tl₂ [NbBr₆] (2) are obtained as black needles on heating TlCl, Nb, S₂Cl₂ (1) and Tl, Nb, and Br₂ at 400°C (2). Tl₂NbBr₆ also forms in the reaction of TlBr, Nb, Br₂, and S at 500°C. Both compounds crystallize in the K₂[PtCl₆] structure type to form non-distorted octahedral [NbХ₆]^2– anions (Nb–Cl 2.397(4) Å and Nb–Br 2.516(2) Å). The magnetic properties of Tl₂[NbBr₆] in a range 5-300 K indicate an antiferromagnetic interaction between Nb⁴⁺ ion spins (d¹, S = 1/2). On cooling, the compound becomes a noncollinear ferromagnet with T_c = 23 K.

Binuclear cobalt complexes [(Cp′′′Co)₂(μ₂-η¹:η²-S₂)₂] (1) (Cp′′′ = η⁵-1,2,4-tris(tert-butyl)cyclopentadienide) and [(Cp′′′Co)₂(μ₂-η¹:η²-Se₂)₂] (2) are obtained by the interaction of [(Cp′′′Co)₂(μ-η⁴:η⁴-C₇H₈)] with excess sulfur or selenium respectively. The structures of the complexes are determined by single crystal X-ray diffraction.

Crystalline nickel(II) decatungstate (II) [Ni(C₂H₆SO)₅(H₂O)]₂[W₁₀O₃₂] is synthesized for the first time and characterized by chemical and thermal analyses, scanning electron microscopy, IR and Raman spectroscopy, and single crystal X-ray diffraction (XRD). By single crystal XRD the crystallographic characteristics of [Ni(C₂H₆SO)₅(H₂O)]₂[W₁₀O₃₂] are determined (triclinic crystal system, space group P–1, a = 11.9339(7) Å, b = 12.2083(6) Å, c = 12.2083(6) Å, α = 75.235(5)°, β = 71.289(6)°, γ = 87.785(4)°, V = 1692.44(17) ų at T = 293(2) K, Z = 1, d_x = 3.223 g/cm³) and the structure is found to be composed of isolated [Ni(C₂H₆SO)₅(H₂O)]₂⁴⁺ cation complexes and [W₁₀O₃₂]^4– anions located in the voids between the cation complexes. By the powder XRD analysis it is shown that the crystals formed by growing from the solution do not contain impurities.

Two copper complexes Cu(tta)₂(L¹)₂ (1) and Cu(tta)₂(L²)₂ (2) are synthesized and characterized by IR spectroscopy, elemental analysis, and single crystal X-ray diffraction. The copper(II) ion of 1 and 2 is in a distorted octahedral environment with four O atoms of the tta ligands and two N atoms of the heterocyclic ligands. The hydrogen bonds play important roles in stabilizing the structures.

The crystal structures of [CuL₂](ReO₄)₂ and [NiL₂](ReO₄)₂ (L = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraaza-cyclotetradecane) are studied. The crystal structural data for [CuL₂](ReO₄)₂, C₁₆H₃₂CuN₄O₈Re₂: a = 13.5523(7) Å, b = 9.3446(4) Å, c = 18.4410(9) Å, V = 2335.38(19) ų, space group Pbca, Z = 4, d_x = 2.402 g/cm³; the copper atom coordination C–N of (2×)1.973(5) Å and (2×)2.008(5) Å, the additional coordination Cu…O of (2×)2.642 Å. The crystal structural data for [NiL₂](ReO₄)₂, C₁₆H₃₂NiN₄O₈Re₂: a = 8.9308(2) Å, b = 14.3479(3) Å, c = 18.6501(4) Å, β = 91.492(1)°, V = 2388.98(9) ų, space group P2₁/c, Z = 4, d_x = 2.334 g/cm³; the nickel atom coordination Ni–N of 1.889(4)-1.917(3) Å, the additional coordination Ni…O of 2.750(3) Å.

A hydrothermal reaction between 4′-phenyl-terpyridine (L), silver(I) salt (silver nitrate), and disodium terephthalate led to the formation of the [Ag₂(μ₂-OCOC₆H₄OCO)L₂] complex. Its structure is determined by single crystal X-ray diffraction and confirmed by ¹H NMR and IR. The compound features a dinuclear neutral {Ag₂(μ₂-OCOC₆H₄OCO)} core in which each Ag⁺ ion is coordinated by three nitrogen atoms from the terpyridine ligand and one oxygen atom from the carboxylic group of terephthalate, forming an irregular AgN₃O square coordination geometry with a separation of 11.3301(5) Å between the two silver ions.

Binuclear bismuth complex [H₂dabco]₂[Bi₂Br₁₀]·4H₂O is obtained by heating the solution of bismuth bromide with diazabicyclo[2.2.2]octane in 2 M HBr. The structure of the complex is determined by single crystal X-ray diffraction. The compound is characterized by IR and Raman spectroscopy, powder X-ray diffraction, and elemental analysis.

The present paper describes the study of the effect of mechanochemical activation on the amorphization process of individual α-cellulose and native cellulose being a constituent part of the lignocellulosic material in the form of partially crystalline fibrils. In processing the powder X-ray diffraction data the following methods are used to determine the degree of crystallinity of cellulose: Segal’s, Rietveld’s, and Lorentzian deconvolution. It is demonstrated that mechanical activation of individual α-cellulose in an AGO-2 laboratory planetary ball mill with a shock-shear action results only in grinding and amorphization, while the degree of amorphization increases propotionally to the duration of the power supply. When α-cellulose is treated in an RM-20 flow-through centrifugal roller mill with a shear action, particle agglomeration is observed together with amorphization. When a lignocellulosic material (wheat straw) is treated in a centrifugal roller mill, considerable amorphization occurs only at high energies, and no particle agglomeration is observed.

[Mn₂(μ-4,4′-trimethylenedipyridine)(μ-3-nitrophthalate)₂(H₂O)₄]_n is synthesized using MnCl₂·4H₂O, 4,4′-trimethylenedipyridine, and 3-nitrophthalic acid as starting materials. The complex is investigated by Fourier transform infrared spectroscopy, single crystal X-ray diffraction, elemental analysis, powder X-ray diffraction, diffused reflectance spectroscopy, photoluminescent spectroscop, and thermogravimetric analysis. The complex crystallizes in the orthorhombic system in the space group Aba2 with cell parameters a = 30.1451(10) Å, b = 9.8718(3) Å, c = 11.3258(4) Å, V = 3370.40(19) ų, and Z = 4. The complex exhibits a 2D structure with each Mn(II) atom octahedrally coordinated to three oxygen atoms from two 3-nitrophthalate units, two oxygen atoms from two water molecules, and one nitrogen atom from 4,4′- trimethylenedipyridine.

An Ag(I) coordination polymer {[Ag(L)(Htbip)]}_n (H₂tbip = 5-tert-butylisophthalic acid, L = 1,1-(1,4- butanediyl)bis-1H-benzimidazole) is synthesized and characterized by the elemental analysis, infrared spectroscopy, thermogravimetric analysis, and single crystal X-ray diffraction. It crystallizes in the monoclinic space group P2₁/c, a = 18.2755(13), b = 8.8515(6), c = 18.4000(13) Å, β = 104.9200(10)°, V = 2876.1(3) ų, Z = 4, C₃₀H₃₁,AgN₄O₄, M_r = 619.46, D_c = 1.431 g/cm³, μ = 0.742 mm⁻¹. The structural analyses display that this compound has a 1D zigzag chain structure which is further extended into a 3D supramolecular framework through O–H⋯O hydrogen bond interactions. The complex can be stable up to 215°C.

A combined experimental and theoretical study is performed on DMSO solvated 7′-amino-1′,3′-dimethyl- 2,2′,4′-trioxo-1′,2′,3′,4′,4a′,8a′-tetrahydrospiro[indoline-3,5′-pyrano[2,3-d]pyrimidine]-6′-carbonitrile. The compound is studied by NMR, IR spectroscopy, and single crystal X-ray analysis. The crystal structure of the molecule is stabilized by intermolecular N–H…N, N–H…O, and C–H…π interactions. In the crystal, the molecules form hydrogen-bonded chains running along the b axis of the unit cell. In the present work, we have applied density functional theory (DFT) to explore the nonlinear properties of the molecule. The harmonic vibrational frequencies are calculated and compared with experimental FT-IR frequencies. The observed and calculated frequencies are found to be in good agreement. The calculated values of the HOMO-LUMO energy gap shows that a charge transfer occurs within the molecule.