Vol 59, No 6 (2018)

The chemical preparation and characterization of a novel coordination compound [CuClO₄(C₄H₆N₂O)4H₂O]ClO₄(C₄H₆N₂O)_0.08 is reported. The compound crystallizes in the monoclinic space group P2_1/c with lattice parameters a = 11.2678(5) Å, b = 12.8102(6) Å, c = 19.7250(8) Å, β = 100.3051(15)°, V = 2801.2(2) ų. The Cu(II) cation is six-coordinated in an elongated distorted octahedral fashion by four N atoms of four 3-amino-5-methylisoxazole ligands, one water oxygen atom, and one perchlorate oxygen atom. In the atomic arrangement, the coordinated and uncoordinated perchlorate anions are grouped in pairs to form anionic layers parallel to the (a, b) plane. A substantial number of H-bonding interactions leads to the formation of an intricate three-dimensional network. The vibrational absorption bands are identified by infrared spectroscopy and the electrical properties are studied by impedance spectroscopy. The DSC analysis agrees with the electrical conductivity results. Magnetic properties are also determined to characterize the complex.

In this study, two ligands and their ruthenium complexes are synthesized and their photovoltaic properties for dye-sensitized solar cells (DSSCs) of new substances substituted by 4,5-diazafluorenone-9-hydrazone groups is investigated. The structures of the compounds are determined by FTIR, UV-Vis, HNMR, CNMR, and MS spectroscopic techniques. The photovoltaic and electrochemical properties of these compounds are investigated and the applicability in DSSCs as photo sensitizers is studied. Photovoltaic cell efficiencies (PCEs) of the devices are in the range 0.08-1.54% under simulated AM 1.5 solar irradiation of 100 mW/cm², and the highest open-circuit voltage (V_oc) reaches 0.43 V. When the photovoltaic performance of the DSSC devices is compared, it indicates that PCEs assume the following: P1–Ru > > P2–Ru > P1 > P2. The PCE value of 1.54% is obtained with DSSC based on P1–Ru under AM irradiation (100 mW/cm²). DSSC based on the P1–Ru produced efficiency of 1.54% whereas DSSC-based P1 exhibits the device performance with an efficiency of 0.08% under illumination. These results suggest that a larger π-conjugated bridge and a richer electron donor of P1–Ru are beneficial for the photovoltaic performance of DSSC.

In this work, a nitrogen-doped anatase TiO₂ nanocrystal is prepared by a modified sol-gel preparation method using the nonionic surfactant (polyoxyethylene sorbitan monooleate) as a structural controller and a soft template. The as-prepared samples are characterized by X-ray diffraction, Raman spectroscopy, UVVis diffuse reflectance spectroscopy, and X-ray photoelectron spectroscopy techniques. Then the photocatalytic activity of these samples is assessed by the photocatalytic oxidation of phenol under visible light irradiation. The phenol concentration is measured using a UV-Vis spectrometer. Experimental results show that N-doping leads to an excellent visible light photocatalytic activity of the TiO₂ nanocatalyst. Furthermore, the formation energy and electronic structure of pure and N-doped anatase TiO₂ are described by density functional theory (DFT) calculations. It is found that N-doping narrowed the band gap of bare TiO₂, which leads to an excellent visible light photocatalytic activity of N–TiO₂ nanocatalysts. Therefore, the prepared N–TiO₂ photocatalyst is expected to find the use in organic pollutant degradation under solar light illumination.

A computer simulation study of a system containing 33666 SPC/E water molecules at the atmospheric pressure and room temperature is carried out. A thermodynamically motivated geometric criterion of the hydrogen bond is developed based on statistical regularities of joint distributions of oxygen-oxygen, oxygen-hydrogen distances, and the interaction energies of molecular pairs corresponding to these distances. Using this criterion makes it possible to substantially increase the selectivity of the algorithms for identifying hydrogen bonds during computer simulation.

The study concerns the dynamics of a network of hydrogen bonds in small water clusters (on the example of hexamer and octamer clusters). The numerical experiment is carried out with the molecular dynamics method using two analytical rigid potentials TIP4P and TIP5P. According to the obtained results, the criteria of phase transitions provided by the cluster theory are not reliable enough in the case of small water clusters. This is testified by the distributions of potential energies of individual molecules in the clusters. It is shown that the appearance of several peaks in these distributions reflects the number of hydrogen bonds between the molecule and other molecules of the cluster.

K-substituted zeolite - clinoptillolite

K_6.16Na_0.16Ca_0.07Mg_0.03(H₂O)_19.2|[Al_6.45Si_29.55O₇₂] (space group C2/m, a = 17.6490(3) Å, b = 17.9982(2) Å, c = 7.39329(12) Å, β = 116.0655(19)°, V = 2109.63(5) ų, Z = 1) is studied by the single crystal X-ray diffraction analysis under ambient conditions and also upon compression to 4 GPa in penetrating (water-containing) and non-penetrating (paraffin) media. Compression of Ksubstituted clinoptillolite in a water:ethanol (1:1) mixture results in its additional hydration: inclusion of 2.2 additional H₂O molecules into the structure at the initial stage. Upon further compression the H₂O concentration increases by two molecules. This is caused by additional occupancy of partially vacant H₂O sites. The cation environment practically does not change during overhydration. Changes in the coordination polyhedra of cations during compression in paraffin are reduced to a small (0.02-0.1 Å) decrease in bond lengths. Distinctions in the degree of hydration of the K-form upon compression in penetrating and non-penetrating media are manifested in the features of the compressibility of the compound.

In the interaction of [CrCp*₂] (Cp* = η⁵-C₅Me₅) with 3,6-di-tert-butyl-o-benzoquinone (Q³⁶), mixed-ligand complexes with the respective monoanionic (SQ³⁶) and dianionic (Cat³⁶) dioxolenes [CrCp*₂][Cr₃(μ₃-O)(Cp*)(SQ³⁶)(Cat³⁶)₃] (1), [{CrCp*(Cat³⁶)}₂(μ-O)] (2), and [Cr(thf)Cp*(Cat³⁶)] (3) are synthesized. Their crystal structures are determined by single crystal X-ray diffraction. The conclusions on the charge state of the central ion and ligands are drawn from the obtained data.

The crystal structure of DL-serinium heptafluorodiantimonate(III) (C₃H₈NO₃)Sb₂F₇ (I) synthesized for the first time is determined (monoclinic crystal system: a = 6.6367(1) Å, b = 5.9521(1) Å, c = 13.5562(3) Å, Z = 2, space group P2₁). The structure of (C₃H₈NO₃)Sb₂F₇ represents a new structure type of complex antimony(III) fluoride with a protonated amino acid cation. It is formed of DL-serinium (C₃H₈NO₃)⁺ cations and dimeric [Sb₂F₇]^- anion complexes. The complex [Sb₂F₇]^- anions consist of two trigonal SbF₄E bipyramids sharing a vertex. The structural units are arranged into a three-dimensional framework via N–H⋯F, O–H⋯O, and O–H⋯F hydrogen bonds.

Three novel trinuclear mixed-transition-metal complexes of Fe(III), Co(III, II), Ni(II) and Cr(III)), with pyridine-2-amidoxime (Hpa) ligand are synthesized, i.e. [FeNi₂(pa)₆]Cl·15H₂O (1), [CrNi₂(pa)₆]OH·5H₂O (2), and [CoCo₂(pa)₆]NO₃ (3). These complexes are characterized by variable-temperature magnetic susceptibility, electrochemistry, and single crystal X-ray diffraction methods. 1 and 2 are heteronuclear metal clusters in the perfect linear arrangement, i.e. [Ni^II⋯Fe^III⋯Ni^II and [Ni^II⋯Cr^III⋯Ni^II] respectively, while 3 is linear [Co^II⋯Co^III⋯Co^II] trinuclear. Theoretical calculations are employed to successfully account for the experimental results of the variable temperature magnetic susceptibility.

A neutral one-dimensional Cd^II coordination polymer [Cd(NO₂–BDC)(NPT)(H₂O)₂]_n (1) (NO₂–H₂BDC=5- nitro-1,3-benzenedicarboxylic acid, NPT=1-(4-nitrophenyl)-1,2,4-triazole) is prepared and characterized through IR, elemental and thermal analyses, and single crystal X-ray diffraction. The single crystal X-ray diffraction analysis reveals that complex 1 is comprised of neutral 1D zigzag chains. The luminescence and thermal stability of complex 1 are investigated.

Two new mixed-ligand Zn(II) coordination polymers, namely {[Zn(dtb)(1,3-bdc)(H₂O)₂](H₂O)}_n (1) and {[Zn1.5(dtb)(1,3,5-btc)(H₂O)₅](H₂O)}_n (2) (dtb = 1,3-di-(1,2,4-triazole-4-yl)benzene, 1,3-H₂bdc = 1,3- benzenedicarboxylic acid, 1,3,5-H₃btc = 1,3,5-benzenetricarboxylic acid) are hydrothermally synthesized and characterized by elemental analyses, infrared spectroscopy, powder and single crystal X-ray diffraction analyses. Both complexes display 1D chain structures. The thermal stabilities and luminescence properties of compounds 1 and 2 are also investigated. Crystal data: 1. C₁₈H₁₈N₆O₇Zn, M_r = 495.75, triclinic, P-1, a = 10.0820(11) Å, b = 10.1833(11) Å, c = 11.2000(12) Å, α = 80.8680(10)°, β = 73.7290(10)°, γ = 63.4320(10)°, V = 986.52(18) ų, Z = 2, R(F) = 0.0246, wR(F²) = 0.0664; 2. C₁₉H₂₃N₆O₁₂Zn_1.5, M_r = 625.49, triclinic, P-1, a = 6.588(4) Å, b = 11.757(7) Å, c = 15.724(9) Å, α = 76.883(6)°, β = 86.094(7)°, γ = 75.989(7)°, V = 1150.8(12) ų, Z = 2, R(F) = 0.0355, wR(F²) = 0.0822.

The crystal structure of the acetic acid solvate of N-(prop-2-en-1-yl)-2-(pyrid-2- ylmethylidene)hydrazinecarboselenoamide (I) is determined. The asymmetric unit of the unit cell in its crystal structure contains a molecule of I and an acetic acid molecule. The molecule of I is non-planar; the angle between the mean square planes of hydrazinecarboselenoamide A(Sе1N1N2N3С1C2) and prop-2-en-1-yl (С5С6C7) moieties is 82.3°. In the crystal, the acetic acid molecules link the molecules of I in endless chains along the [010] direction.

We located multiple binding sites for doxycycline on DNA under physiological conditions, using spectroscopic methods and molecular modeling. Fourier-transformed infrared spectroscopy and UV-visible spectroscopy are used to determine the ligand intercalation and external binding modes, the binding constant, and the stability of doxycycline–DNA complexes in an aqueous solution. Spectroscopic evidence shows that the doxycycline (DOXY) complexation with DNA occurs via G–C and A–T, and a PO₂ group with a binding constant K(DOXY–DNA) = 1.4×10⁴ M^–1. Uniform rare-earth gadolinium oxide (Gd₂O₃), as formed through a precipitation process using hexamine as template, are characterized using X-ray diffraction and scanning electron microscopy. Another aim of the study was to investigate the degradation of the DOXY antibiotic by nanosized Gd₂O₃ under ultraviolet irradiation. Various experimental parameters such as initial DOXY concentrations, initial Gd₂O₃ concentration, initial pH, reaction times are investigated. According to the results, this method can be good in the removal of DOXY.

By an ab initio Hartree-Fock method at the (6-311+G*) level of theory the structural and energy characteristics of gallic acid (GA) complexes are calculated with and without taking into account the first hydration shell: GA–GA, GA–H₂O, GA–H₂O–GA and GA–H₂O–GA (+6 water molecules), GA–GA (+8 water molecules). The calculations are carried out in the vacuum and aqueous solutions by the selfconsistent reaction field method (SCRF calculations). The solvent effect is studied using the Onsager model. The effect of the medium on the geometry, dipole moment, and stability of the considered complexes is estimated. The most stable structures of the complexes, their geometric parameters and atomic charges are determined and the vibrational spectra are calculated. In the aqueous medium, the GA–GA complex (ΔE_int =–12.9758 kcal/mol) is found to be the most stable as compared to GA–H₂O and GA–H₂O–GA. It is shown that the involvement of solvent molecules as the first hydration shell significantly affects the structure and stability of GA complexes.

The density functional method in the full-electron approximation is used to calculate optimized structural parameters, band spectrum, density of states, electron density maps and to study chemical bonding in the low-temperature phase of lithium imide with a crystal structure of the space group Ima2. The valence band width is 15.14 eV, and it consists of three subzones (slightly dispersed bottom subzone, medium subzone, and top subzone with a width of ~2.4 eV) due to dispersion cased by hybridization of hydrogen s states and nitrogen p states. The top of the valence band and the bottom of the conduction band are in the center of the Brillouin zone, the width of the band gap is 4.48 eV, the absorption edge is direct. The electron density maps demonstrate chains of N–H complexes bound by pairs of Li atoms. The Li–N bond is predominantly ionic, while the N–H bond is polar covalent.

Interactions and natural bond orbital analysis of cyclopropylpiperazine(cppp) and B- or Al-doped C₆₀ fullerenes are investigated by quantum mechanical calculations. The structural and electronic properties, such as NH stretching vibrations, nuclear magnetic shielding tensors of ²⁷Al and ¹¹B nuclei or the energy gap are also investigated. All calculations are carried out in the gas phase and water media. Results of the bond order and the binding energy suggest that chemisorption occurs between the cppp nitrogen atom and boron or aluminum atoms of fullerenes. The Alcomplex in water is foundto have the highest binding energy. Further, AlC₅₉…cppp complexes have a slightly higher kinetic stability and a low chemical reactivity. However, BC₅₉…cppp works as a function-type sensor for cppp.

A comprehensive theoretical study on the conducting oligomeric systems is carried out in view of their potential application in electrochemical charge storage. Density functional theory (DFT) calculations are carried out on a series of oligomers made up of 3-(p-fluorophenyl)-thiophene (FPT) to estimate the geometric and electronic structures, conjugated lengths, bandwidths, and energetic properties of polymeric systems. The calculations are performed on the dimer up to octamer chains in the ground state and both pand n-doped phases. The results obtained show that the conjugated system in p- and n-doped oligo(FPT)s has a higher distance with more planar chains with respect to their neutral forms. The band gap energy between the frontier molecular orbitals decreases dramatically for both ionic states, and approaches a low limiting value with increasing oligomer length. The charge delocalization through the monomer rings along the backbone oligo(FPT)s reveals that the p- and n-doped states had more suitable properties, reflecting the electron and hole transport characteristics for conductivity, respectively. The calculated first excitation energies for oligo(FPT)s at the time-dependent B3LYP/6-31G(d,p) level of theory indicate that both doped oligomers have lower excitation energies, which display a red shift in their absorption spectra. For polymeric systems, the evolution of ionization potential, electron affinity, electron chemical potential, molecular hardness, and thermodynamic stability is made through the extrapolated oligomer ones.

The structure of 2-methylphenylcyanamide NCNH(C₆H₄Me-2) is established in the solid state using single crystal X-ray diffraction data. The contribution of various intermolecular contacts to the crystal packing is studied using the Hirshfeld surface analysis and quantum chemical calculations within the density functional (DFT) M06-2X/6-311++G(d,p) level of theory.

The original list of authors, affiliation was not given in full. Should read: