Home – Home – Jornals – Chemistry for Sustainable Development 2016 number 1

Based on the optical model of the Earth atmosphere developed by the authors, the numerical simulations of the propagation effectiveness of intense radiation of different laser sources in the near- and mid-IR spectral ranges on high-altitude slant optical paths are carried out. Different laser sources, including chemical oxygen-iodine laser (COIL), chain chemical DF laser, and carbon-oxide (CO) laser are considered upon different optical weather conditions taking into account linear and nonlinear optical effects. We show that in terms of the net laser power transmitted along a path, the most preferable is the use of a COIL source because of low atmospheric linear attenuation and minimum influence of nonlinear effects. This laser source also demonstrates the best performance in terms of the mean radiation intensity at the receiver plane. Among multispectral chemical lasers, DF lasers take the first place when comparing the power transfer function.

Temporal dynamics of maximum intensity and laser power in a finite-size aperture of the focused radiation at a wavelength of 10.6 microns under thermal self-action in a clear turbulent atmosphere is analyzed by means of computer simulation. Propagation of Gaussian beams along up to 160 m path is considered. It is shown that under strong turbulence conditions there are time intervals in which the maximum intensity in the middle of the path of a tightly focused beam is greater than in the focal plane at the end of the path.

Formation of light bullets is numerically investigated during filamentation of near and mid-IR femtosecond pulses in condensed media at anomalous group velocity dispersion. On the example of filamentation of microjoule pulses at wavelengths of 1.4, 1.8, and 2.2 mm in fused silica at powers slightly exceeding the critical self-focusing power, it is established that the subsequent light bullets are not formed if the dispersive length is much bigger and much smaller than the self-focusing length. It is shown that the peak intensity in light bullets does not depend on the initial pulse intensity, is determined by the multiphoton order of laser plasma generation, and increases with the order. In fused silica, the peak intensity in a light bullet makes about 40 TW/cm² during filamentation of microjoule pulses at a wavelength of 1.4-2.2 mm, and in CaF₂, the peak intensity reaches 120 TW/cm² for pulses at a wavelength of 3 mm. The light bullet is a short-lived formation existing on less than 1 mm distance. It is found that the change in the pulse energy at a wavelength of 3 mm during filamentation in CaF₂ influences the number of light bullets and does not increase their time of life.

A new physical mechanism of Gulf Stream abnormally large heating (up to 20 ^oC) and current shifting to the North (~ 200 km) in the summer 2011 off the coast of New Carolina was suggested and discussed. The key point is a tenfold decrease of sea water shear viscosity due to conversion of H₂O para-ortho spin isomers when heated to a temperature singular point (19-20 ^oC). This results in Gulf Stream shifting from the previous trajectory due to an inertial motion in a straight line. The observed phenomenon was triggered by Deepwater Horizon disaster in the Gulf of Mexico in 2010. The huge oil eruption resulted in iridescent film formation over a hundreds of thousands of square kilometers area (http://newsland.com/news/detail/id/1218207). The thin oil film dramatically changed the solar radiation absorbance and sea water thermodynamics, blocked the evaporation.

Fluorescence of thin oil films on the water surface induced by femtosecond UV laser pulse was studied experimentally. A wide range of laser pulse intensity including filamentation mode was studied. Applicability of this method to femtosecond UV pulses with two central wavelengths of 248 and 372 nm were compared. There was demonstrated that the spatial resolution of the fluorescence localization was not worse than 30 cm.

The new atmospheric correction algorithm is presented. The algorithm gives albedo of a heterogeneous lambertian surface taking into account multiple scatterings and reflections of the solar radiation. Test results to demonstrate potential of the algorithm are presented.

In the lidar complex, the combined optical method for sensing the lower and middle atmosphere was used. The method is based on the receiving signals of Rayleigh (elastic molecular scattering of light at a wavelength of 532 nm) and Raman (radiation of the first vibrational-rotational transition of nitrogen molecules at a wavelength of 607 nm when excited by the laser radiation at a wavelength of 532 nm) light scattering. The use of Raman channel made it possible to eliminate the distorting effect of aerosol at altitudes of its localization (up to 25 km) on the accuracy of temperature measurement. Extended temperature profiles at altitudes from 7 to 60 km, covering the upper troposphere and middle atmosphere, were obtained during simultaneous measurements of the signals at two receiving channels. A good agreement of the data with satellite and upper-air measurements and model results was obtained.

We consider the results of remote spectrophotometric and lidar measurements of the total ozone and nitrogen dioxide contents and temperature obtained at the Siberian Lidar Station (SLS) of V.E. Zuev Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences (Tomsk: 56.5°N, 85.0°E) in comparison with the results of analogous satellite measurements. The ground-based measurements of the total ozone content are performed with the help of a М-124 ozonometer; and the measurements of the NO₂ content are carried out with an automated spectrophotometer. The ground-based lidar measurements of temperature are conducted on the basis of SLS measurement complex. These measurements are compared with data of radiosonde and satellite measurements. The satellite measurements are performed by the TOMS and IASI instrumentation.

The May-July precipitation data for the Russian Southern Ural reconstructed via treatment of the radial growth of larch late Sukachev (Larix sukaczewii Dyl.) were analyzed with a wavelet transform. Next, a cross wavelet transform was used to compare the reconstructed data with the average annual values of Wolf numbers (sunspot numbers (SSN)) and the North Atlantic Oscillation (NAO) and Atlantic Multidecadal Oscillation (AMO) indices. The wavelet analysis revealed hidden periodicities in the original series and allowed one to define the relationship with the Wolf numbers and the NAO and AMO variabilities. It was found that the dominant 11-year SSN cycle is present in the reconstructed data almost over the entire time of observation. The reconstructed series of May-July precipitation showed good correlations with the NAO index for 8-11 year periods and with the AMO index for 11-50 year periods. In the analysis, the observation time spans 375 years (1631-2005) for the reconstructed May-July rainfall series, 306 years (1700-2005) for the Wolf numbers, 141 years (1865-2005) for the NAO index, and 150 years (1856-2005) for the AMO index.

The article presents the calculation results of the laser landing system efficiency (LLS) based on the definition of minimum required fluxes of scattered radiation from fixed extended pinpoints (FEPs), which are the LLS indicators at the visual detection of FEPs in the field conditions. It is shown that the minimal power P_min = 0.5 W for  = 0.52 m and  = 0.64 m is required to reliably detect the laser beams of the course glide group at night from distances L » 1.0-1.6 km at S_m = 800 m for deviations from the glide path to the angle  = 0-5. In twilight conditions, the green and red laser beams are visible from the distance L = 1-1.2 km for all S_m. When L = 1.6 km laser beams are visible at S_m > 2 km. The presence of commercially available lasers and the calculations confirm the possibility of creation of the LLS based on a new generation of lasers that can ensure aircraft landing satisfying I Category ICAO.

The paper presents the results of theoretical and experimental studies of the second harmonic generation process in the Ti:sapphire femtosecond complex, which includes generator of the femtosecond pulse, stretcher, regenerative amplifier, two multi-pass amplifiers, compressor, and second-harmonic generator. This complex provides 50-fs pulses with energy of 20 mJ and is used as a master oscillator in the THL-100 hybrid laser system, which operates in the visible region at a wavelength of 475 nm. Experiments and calculations for various beam parameters of the fundamental harmonic, such as radiation intensity, spatial profile of the beam, and the level of the noise component, were performed. It is theoretically shown that in the absence of the noise component in the beam of the fundamental wave a good homogeneity of the second harmonic should be observed. When making the amplitude inhomogeneities in the first harmonic even greater inhomogeneities in the second harmonic appeared. It is experimentally shown that the inhomogeneity of the second harmonic beam increases with the beam energy.

The paper presents first results on how CuBr laser active media can be used for high speed nanomaterial production process imaging. Various visualization circuits are considered. The results of visualization obtained using these circuits are given. The possibility of full suppression of stray background light, which is the laser monitor main advantage for diagnostics, is demonstrated. The application areas for each circuit are discussed.

Effect of the nature and content of secondary support, as well as the content and nature of palladium precursor on the catalytic activity in CO oxidation is considered for Pd/MeO _x /Ni-Al/SS catalysts where SS is stainless steel. It is demonstrated that the Ni-Al coating used to increase oxide adhesion to the metal substrate can serve as a catalyst and secondary support for palladium. It was determined that the best palladium precursor is [Pd(NH₃)₄](NO₃)₂. On the basis of the results of catalytic tests, the most active samples activated and not activated by palladium were revealed. All the catalysts are characterized by means of X-ray phase analysis and scanning electron microscopy with local microanalysis.

Results of field and laboratory studies of steam and gas assisted escape of elements from the material of sulphide-containing tailing dump (Komsomolsk settlement, Kemerovo Region) are presented. It was established that sulphur dioxide concentration in the ground layer of the atmosphere above the tailing dump exceeds the maximum permissible concentration more than 10 times. Due to emission from ground into the air, a broad range of chemical elements enters the atmosphere, though these elements are traditionally considered as non-volatile at low temperatures (Fe, Al, Mn and so on). The concentrations of As, Ni, Zn and Pb are substantially higher than the MPC for the air of populated areas. The coefficients of element distribution between the pore solution and the absorbing substance (alkaline load) were calculated. The mobility of elements in phase separation depends on the forms of their presence in pore solutions of the upper part of storage. The urgency of determining MPC and/or relatively safe level of emission was revealed for the elements for which the standard values have not been adopted yet.

The effect of mechanochemical action of aqueous alkaline media on the chemical composition and molecular mass distribution of lignin from upland peat was studied. It was shown that mechanochemical action leads both to hydrolytic destruction and to condensation processes in the molecular structure. These transformations are combined with oxidative processes. The accumulation of a noticeable amount of polar groups in lignin causes an increase in its hydrophilic properties and promotes a decrease in molecular mass due to the dissolution of low-molecular fraction in aqueous alkaline solution. As a consequence, complicated and deep lignin transformations combining destructive and condensation processes lead to gradual transformation of its chemical structure into humic substances. Lignin molecules subjected to sonolysis are composed of oxidized guayacyl and hydroquinone fragments connected through ether bonds or carbon bonds of methylene group. Some guayacyl fragments are oxidized to 2,3-dihydroxybenzoic acid. Along with carbon-carbon and ether bonds, they also include insignificant amount of nitrogen-carbon bonds formed as a result of oxidative ammonolysis of lignin during sonolysis. The stability of a part of lignocarbon bonds to hydrolytic action promotes the formation of not only framework but also the peripheral part of humic acids formed from polyose fragments as a result of sonolysis. The intensity of transformation of the lignocarbon complex into humic substances is due to the strength of the base used during sonolysis. It is assumed that the low molecular mass fractions of lignin participate in the formation of the framework part of humic substances during sonolysis of the secondary plant raw material in alkaline media.

The processes of phase formation and metal ion distribution in the systems without organic solvent were studied. The concentration parameters of the existence of two-phase systems water - polyethylene glycol esters of monoethanolamides of synthetic fatty acids (C _n H_{2 n + 1}CONHCH₂CH₂O(C₂H₄O) _m H, where m = 5-6, n = 10-16 (syntamide-5) - inorganic salting-out agent) were determined experimentally. Chlorides, fluorides, bromides, sulphates, nitrates, carbonates and acetates of alkaline, alkaline earth metals and ammonium, and some acids were used as salting-out agents. A comparison of salting-out capacity of salts and acids was carried out on the basis of the concentration boundaries of layering regions. The broadest concentration range of the existence of layering region is observed in the case of ammonium salts. The region of two-phase liquid equilibrium is conserved to water concentration 94 % in the system with ammonium sulphate and 93 % in the system with ammonium chloride. Extraction possibilities of the system water-syntamide-5-hydrochloric acid were evaluated. Quantitative extraction of thallium (III) from HCl solutions with the concentration of 2-3 mol/L was established.

Experiments on the enhancement of plant stability to oil pollution of soil were carried out for Vicia sativa as example. It was established that the positive effect on the probability of plant survival and an increase in the degree of destruction of oil pollution may be achieved due to the preliminary treatment of seeds by soaking them in potassium humate of salicylic acid solutions in different concentrations. With a 5 % addition of oil into soil, the best result on germ survival and the degree of destruction of oil pollution was obtained after seed soaking in the solution of salicylic acid with the concentration of 10^-4 mol/L, while for 10 % addition of oil - in the solution with the concentration of 10^-3 mol/L. Somewhat less efficient is seed treatment in humate solution. Baikal EM-1 preparation has insignificant positive effect only in the case of 5 % oil addition into soil. The degree of destruction of oil pollution exhibited good correlation with the survival of Vicia sativa ( K _corr = 0.9) in all experiments. A positive result of seed soaking in potassium humate is likely connected with its adaptogenic activity. Salicylic acid in low concentrations (10^-3-10^-4 mol/L) seems to be able to induce prooxidant processes participated by Н₂О₂. Due to this fact, first of all, the stability of plant organism to environmental stress factors increases as early as at the stage of seed soaking; second, Н₂О₂ and peroxidase secreted into the rhizosphere enhance the processes of oxidative oil destruction. Preliminary soaking of seeds in the solutions of salicylic acid with different concentrations depending on the level of oil pollution, or potassium humate may be recommended to increase the efficiency of revegetation of oil-polluted soil by means of phytoremediation.

Liquid-phase hydrogenation of acetylene into ethylene in a flow set-up with a steady catalyst layer at a pressure of 10 atm was investigated. N-methylpyrrolidone was used as a solvent. The effect of temperature and the presence of CO in the gas flow on the characteristics of selective hydrogenation of acetylene on Pd/Al₂O₃, Pd/Sibunite catalysts was studied. It was demonstrated that the selectivity of ethylene formation increases with an increase in CO content in the gas mixture H₂/CO, ethane content in reaction products decreases simultaneously, while the selectivity of the formation of C₄₊ oligomers remains practically unchanged. With an increase in reaction temperature, the degree of acetylene transformation increases, while the relations between reaction products change only insignificantly. The results provide evidence that liquid-phase hydrogenation of acetylene in the flow mode at a pressure of 10 amt and temperature of 120 °C and the presence of CO in the gas flow in the amount of 20 vol. % provide high conversion degree and selectivity of the formation of target product.

The effect of preliminary mechanochemical treatment of the mixtures of metal bismuth and the compounds of different composition on bismuth oxidation by atmospheric oxygen was studied by means of X-ray phase analysis and thermogravimetry. It was established that the oxidation of metal bismuth occurs at the stage of dispersion. It is shown that mechanochemical treatment of a mixture of metal bismuth with 10-30 % its oxide leads to a decrease in the temperature of the start of bismuth oxidation from 350 to 200 °C. It was established that complete transformation of bismuth into its oxide may be carried out by means of annealing of mechanochemically treated mixture of metal bismuth and its oxide (20 %) at 300 °C for 12 h, while at annealing temperature 400 °C - for 1 h. In the case of mechanochemical activation of the mixture of metal bismuth and sodium carbonate, followed by washing with water, the product is mainly bismuth oxide and oxo(hydroxo)carbonate and can be used at the stage of obtaining solutions of bismuth salts. It was shown that mechanochemical activation of a mixture of metal bismuth and sodium chloride followed by washing with water leads to the formation of a mixture of bismuth oxide and oxochloride. This mixture can be used at the stage of obtaining bismuth-containing hydrochloric solutions. It was established that bismuth oxide may be obtained by preliminary mechanochemical activation of metal bismuth with sodium or ammonium nitrate, as well as with stearic acid. The specific surface of bismuth oxide obtained as a result of mechanochemical activation of metal bismuth with different compounds was determined; it varies within the range 0.29-5.87 m²/g.

A method to obtain carbon nanofibres doped with nitrogen, with nitrogen content up to 8 mass %, was developed on the basis of the mechanism of carbide cycle of the synthesis of carbon nanomaterials. Within the framework of this mechanism, active dispersed nickel particle is a polyfunctional nanometre-sized system acting as a physicochemical robot and controlling the synthesis process.

Synthesis of layered double hydroxides (LDH) of MgAlSn with the ratio of Mg/(Al + Sn) = 3 and Sn/(Sn + Al), equal to 1, 5, 10 and 30 %, was carried out. The structural and acid-base properties of these compounds and the formation of the oxide phase were studied using a set of physicochemical methods (XPA, TA-DTG, СО₂ adsorption). It is shown that LDH obtained through co-precipitation have a single-phase composition for Sn/(Sn + Al) < 30 %. With an increase in tin content in the support, a side phase Mg(Sn(OH)₆) is formed. According to the data of СО₂ adsorption, the introduction of tin into LDH layers does not worsen their basic properties. Tin within the support promotes modification of the properties of platinum centres affecting the catalytic properties of Pt/MgAlSnO _x in the reaction of n- decane dehydrogenation. The dependence of n- decane transformation degree on tin content is extremal with the maximum at Sn/(Sn + Al) = 1 %, while the maximal yields of olefins and maximal selectivity are observed for the sample with Sn/(Sn + Al) = 5 %. The catalytic characteristics of the Pt/MgAl-5 % SnO _x sample are comparable with those for the industrial catalyst tested under similar conditions, which points to the promising character of further studies of the systems based on tin-containing LDH.

Results of the tests of platinum-containing catalysts on supports <>-ZrO₂-Al₂O₃, B₂O₃-Al₂O₃ and WO₃-Al₂O₃, as well Y-type, beta and mordenite zeolites mixed with aluminium oxide, within temperature range 200-375 °C are presented. It is shown that zeolite-containing catalysts ensure the maximal yield of methylcyclopentane - at a level of 14 mass % at a temperature of 275-300 °C. At higher temperature, the contribution from side reactions of cycle opening and hydrocracking increases on zeolite catalysts. Among anion-modified systems, the highest selectivity is demonstrated by the sample Pt/WO₃-Al₂O₃: the maximal yield of target methylcyclopentane and isoheptanes in the product mixture is 16.2 and 57 mass %, respectively. Almost complete benzene removal is provided, and the degree of heptane transformation is 80.6 %.

Effect of the modification of foamed polyurethane on extraction-sorption recovery of resorcinol from aqueous media was studied. The ratio of adsorbent/modifying agent phases was chosen. The conditions of adsorption-sorption concentrating of resorcinol were studied.

Under the conditions of inevitable depletion of the world resources of natural fossil fuel, in particular petroleum, an increase in oil recovery is an acute problem. The deposits of highly viscous heavy oil are increasingly actively involved in mining. The production of this kind of oil requires the action of steam and compositions containing chemical reagents. Not only the quantitative but also the qualitative composition of mined oil and investigation of the effect of different methods of oil recovery play essential part. In the present work we studied the effect of compositions pumped into productive deposits on the composition of mined heavy highly viscous petroleum from the Usinsk deposit (Republic of Komi, Russia). The introduction of oil-sweeping compositions into the stratum was carried out at the experimental plots through injection or producing wells, which provided a substantial increase in oil output. Using a set of physicochemical analysis methods (liquid adsorption chromatography, GC-MS), we studied the dynamics of the changes in the group composition of saturated and cyclic hydrocarbons, heterorganic compounds, individual composition of alkanes from oil subjected to the action of compositions. The most significant increase in the content of aromatic hydrocarbons and heterorganic compounds in oil was observed with the use of Zagushchennaya NINKA composition. The action of IKhN_PRO composition caused an increase in alkane content in the group composition of oil. It was shown that redistribution of light (C₁₀-C₁₅) and high molecular mass (more than С₁₆) homologues occurs among n- alkanes. The obtained results may promote deeper understanding of the processes occurring in the deposits as a result of the action of oil-sweeping compositions. Investigation of the effect of compositions on the composition of heavy highly viscous oil also allows one to control the quality of produced hydrocarbon raw material entering the processing facilities.

Modifiers of the properties of petroleum paving bitumen were developed on the basis of two kinds of acryl-nitrile rubbers BNKSС-18 AM (TU 38.30313-2006) and BNKS-28 AM (TU 38.30313-2006) and the fraction of liquid products of tyre pyrolysis without access of the air, with boiling point above 170 °C. Rubber content in the mixture did not exceed 30 mass %, the temperature of mechanical homogenization was 100-120 °C duration was 3 h. Preliminary studies showed that the mixtures prepared under these conditions do not get separated into phases when kept hot for 6 h. Addition of a modifier in the amount of 3-5 mass % per rubber improves the elasticity of bitumen and, which is especially important, causes a substantial decrease in brittle temperature. Due to this, resistance of paving asphalt concrete to frost and to cracks increases substantially. The composition of the fraction of liquid products of tyre pyrolysis was determined by means of IR spectroscopy and gas chromatography-mass spectrometry. This composition includes more than 100 individual compounds with content >0.1 % of the sum of all detectable peaks. These substances are represented mainly by aromatic hydrocarbons, mainly the derivatives of benzene and naphthalene containing aliphatic fragments with total number of carbon atoms 4 to 10 as substituents (43 rel. %). In addition, hydrocarbons with menthene structure were detected (31 rel. %), and aliphatic acyclic hydrocarbons with chains containing 16 to 27 carbon atoms (18 rel. %). Nitrogen-containing compounds are represented by hexahydro-2Н-azerin-2-one (caprolactam) - 0.5 rel. %, as well as 1,2,3-benzotriazol - 0.9 rel. %.

The X-ray crystallographic analysis of 1,7-difluoro-1,1,3,5,7,7-hexanitro-3,5-diazaheptane has been carried out. We have also determined its sensitivity to mechanical actions and a set of calculated and experimental data on explosion characteristics.

We report here the synthesis of the Z-3N(2-ethoxyphenyl)-2-N¢(2-ethoxyphenyl)-imino-thiazolidin-4-one compound. The crystal structure is determined by X-ray diffraction. The compound crystallizes in the monoclinic system with the space group P 2₁/ n and cell parameters: a = 9.4094(10) Å, b = 9.3066(10) Å, c = 20.960(2) Å, b = 99.0375(10)°, V = 1812.7(3) ų and Z = 4. The structure is refined to final R = 0.05 for 2083 observed reflections. The molecule in the crystal exhibits the intermolecular hydrogen bonds of C-H…O, C-H…N, and C-H…S types. Ab initio calculations are also performed at Hartree-Fock (HF) and density functional theory (DFT) levels. The full HF and DFT geometry optimization is carried out using the 6-31G( d , p ) basis set. The observed molecular structure is compared with that calculated by both HF and DFT methods. The optimized geometry of the titled compound is found to be consistent with the structure determined by X-ray diffraction.

Sterically hindered meso -tetramethyl- meso -tetraarylcalix[4]pyrroles 1-4 where aryl is p -fluorophenyl 1, p- chlorophenyl 2, and p -methylphenyl 3, 4 (configurational isomers) are synthesized and purified by the recrystallization technique. They are characterized by IR, ¹H and ¹³C NMR, and mass spectroscopy. Configurational isomers aabb (3) and aaaa (4) of meso -tetramethyl- meso -tetramethylphenylcalix[4]pyrroles are assigned by the ¹H NMR studies and confirmed by the X-ray diffraction analysis. The single crystal X-ray diffraction analysis reveals that the ethanol adduct of 1, the acetone adduct of 2 and 3 adopt the 1,2-conformation while the acetone-water adduct of 1 and the acetone adduct of 4 adopt partial cone and cone conformations respectively. The conformational diversity is due to non-covalent interactions among the encapsulated guest, pyrrolic NH protons, and meso- substituents. Anion binding studies (F^-, Cl^-, CH₃COO^-, _{) are carried out through ¹H NMR titrations; the binding constants are evaluated using the EQNMR program, displaying that they are more selective towards fluoride rather than other anions with the 1:1 stoichiometry. The configuration of compounds drastically influences the ion-recognition processes.}

The synthesis of two 1,2,4-benzothiadiazine derivatives, namely, 6-bromo-4 H -spiro[1,2,4-benzothiadiazine-3,1¢-cyclobutane] 1,1-dioxide (1) and 6-bromo-1¢-ethyl-4 H -spiro[1,2,4-benzothiadiazine-3,4¢-piperidine] 1,1-dioxide (2) is described in the present work. The synthesized compounds were studied by IR, ¹H and ¹³C NMR, and single crystal X-ray diffraction to determine their molecular and crystal structure. In both structures the conformation of the 1,2,4-thiadiazinane ring is a twisted chair and is stabilized by the intramolecular interaction of the C-H…O type. Compound 1 crystallizes in the monoclinic crystal system and space group C 2/ c with the unit cell parameters a = 15.8690(17) Å, b = 12.1453(16) Å, c = 12.0152(15) Å, b = 99.686(7)°, Z = 8 and V = 2282.7(5) ų. Compound 2 crystallizes in the monoclinic crystal system and space group P 2₁/c with the unit cell parameters a = 14.5748(6) Å, b = 9.3340(5) Å, c = 12.4283(6) Å, b = 112.757(2)°, Z = 4 and V = 1559.14(13) ų. In the crystal structures different packing motifs are implemented with the formation of supramolecular assemblies of different types due to classical hydrogen bonds such as N-H…O and intermolecular interactions of N-H…Br, N-H…N, C-H…O types and p…p stacking.

A new chalcone derivative 1-phenyl-3-(4-bis(2-chloroethyl)aminophenyl)-2-propen-1-one with the molecular formula C₁₉H₁₉Cl₂NO is synthesized by the Claisen-Schmidt condensation reaction. A transparent yellow single crystal was obtained by the slow evaporation solution growth technique using ethanol at room temperature. The compound crystallizes in the triclinic crystal system, P -1 space group, Z = 4, calculated density = 1.332 mg/m³, V = 1736.00(8) ų with unit cell parameters a = 7.8899(2) Å, b = 14.1924(4) Å, c = 15.7879(4) Å, a = 83.1280(10)°, b = 81.929(2)°, g =86.4820°. The second harmonic generation efficiency is found to be 1.5 times higher than that of urea. Thermal stability of the crystal is found to be 250°C determined from the thermogravimetric analysis. The FT-IR spectroscopy is used to identify the functional groups of the synthesized compound. The optical behavior of the grown crystal is examined by the UV-visible spectral analysis, which shows that the absorbance is almost negligible in the wavelength range 400-1300 nm.

Novel bis-NO-acyclic Schiff base compounds are synthesized by the condensation of 3-methoxy-4-(2-(4-formyl-2-ethoxyphenoxy)ethoxy)benzaldehyde with 2-aminophenol (L¹) or 4-aminophenol (L²). The titled compounds with the monoclinic space group C 2/ c are characterized by elemental analyses and single crystal X-ray diffraction.

We report the synthesis and characterization of two new macrocyclic Schiff base compounds: a 15-membered (1) and 16-membered (2) one. Their synthesis involves a Schiff base condensation of 2,2-dimethylpropanediamine and two dialdehydes: 5,5¢-dimethoxy-2,2¢-(ethane-1,2-diyldioxy)dibenzaldehyde and 5,5¢-dimethoxy-2,2¢-(propane-1,3-diyldioxy)dibenzaldehyde. The compounds are characterized by elemental analysis (CHN), FT-IR, ¹H and ¹³C-NMR spectroscopy, and single crystal X-ray diffraction. Compound 1 crystallizes in the monoclinic space group Cc with a = 11.0668(5) Å, b = 11.7962(5) Å, c = 17.1980(9) Å, b = 103.611(5)°, V = 2182.08(18) ų, Z = 4, R ( F ² > 2s( F ²)) = 0.048 and wR ( F ²) == 0.150, while compound 2 crystallizes in the monoclinic space group C 2/ c with a = 38.4782(15) Å, b = 5.6309(2) Å, c = 20.4029(7) Å, b = 102.524(4)°, V = 4315.4(3) ų, Z = 8, R ( F ² > 2s( F ²)) = 0.051 and wR ( F ²) = 0.130.

By single crystal X-ray diffraction the features of the molecular and crystal structures of 2-morpholino-5-trifluoromethyl-1,3,4-thiadiazole are determined. This is the main substance of the certified reference material of trifluoromethylmorpholinothiadiazole for the quantitative elemental analysis of fluoroorganic compounds.

By the interaction of methyl 1-bromocyclobutanecarboxylate with zinc and ethyl 6-bromo-2-oxo-2Н-chromene-3-carboxylate, ethyl E-6-bromo-4-[1-(methoxycarbonyl)cyclobutyl]-2-oxochromene-3-carboxylate is obtained whose structure is determined by X-ray crystallography.

A series of fluoro- and hydroxy-substituted thiocarboxyhydrazones, 2-(3-fluorobenzylidene)-N-methylhydrazinecarbothioamide (1), 2-(2,3-difluorobenzylidene)-N-methylhydrazinecarbothioamide (2), and 2-(2-hydroxybenzylidene)-N-methylhydrazinecarbothioamide (3), are synthesized and characterized by elemental analysis, IR and UV-vis spectra, and single crystal X-ray diffraction. Structures of the three compounds are similar, but with a slight modification due to fluoro substituting groups. The crystal structures of the compounds are stabilized by hydrogen bonds and π⋯π interactions. The antimicrobial activity of the compounds shows that they are effective against some bacteria.

Two bromo-substituted Schiff bases 5-bromo-2-methoxy-4-( p -tolyliminomethyl)phenol (1) and 2-bromo-6-[(6-methylpyridin-2-ylimino)methyl]phenol (2) are prepared and characterized by elemental analysis, ¹H and ¹³C NMR, and single crystal X-ray diffraction. Compound 1 crystallizes in the triclinic space group _{with unit cell dimensions a = 6.228(1) Å, b = 10.929(2) Å, c = 21.312(2) Å, α = 104.230(2)°, β = 91.780(2)°, γ = 90.890(2)°, V = 1405.0(4) ų, Z = 4, R 1 = 0.0359, and wR 2 = 0.0830. Compound 2 crystallizes in the monoclinic space group P 21/ c with unit cell dimensions a = 8.180(2) Å, b = 12.011(3) Å, c = 12.843(3) Å, β = 106.263(2)°, V = 1211.4(4) ų, Z = 4, R 1 = 0.0364, and wR 2 = 0.0889. X-ray diffraction indicates that the Schiff base molecules of the compounds display trans configuration with respect to the C=N double bonds. The crystal structures of the compounds are stabilized by hydrogen bonds and weak π⋯π interactions.}

The single crystal X-ray analysis of 3-amino-1{[bis(benzylsulfanyl)methylidene]amino}urea shows that the compound crystallizes in the triclinic system with the space group P -1 and Z = 4. The asymmetric unit contains two independent molecules of 3-amino-1{[bis(benzylsulfanyl)methylidene]amino}urea. Both bis(benzylsulfanyl)methylidene groups are in a trans configuration with respect to the C16/O1/N3/N4 and C32/O2/N7/N8 fragments, respectively. The tautomeric transition energies of the three tautomeric forms are calculated at the generalized gradient approximation (GGA) level by the BLYP/DND method to estimate the kinetic and thermodynamic barriers. The keto form has a lower energy than the other two forms. Relatively lower values of kinetic barriers (about 58 kcal/mol for the transition between ( a ) and ( b ) forms) are found.

The title compound C₂₉H₂₈N₈O₄, 1,1¢-(propane-1,3-diyl)bis(5-benzyl-7-methyl-1H-pyrazolo[3,4-d]××pyrimidine-4,6(5H,7H)-dione) is characterized by single crystal X-ray diffraction. It crystallizes in the centrosymmetric space group P _{, with two molecules in the unit cell. There is one formula unit in the asymmetric unit with a folded conformation due to arene interaction and an unusually large angle of 124° in the propylene linker. The crystal structure is stabilized due to the presence of π-π and C-H…O interactions.}

8-(1-((5-Cyclopentenylpyridin-3-yl)methyl)piperidin-4-yl)-3,4-dihydroquinolin-2(1H)-one (1) and 8-(1-(3-cyclopentenylbenzyl)piperidin-4-yl)-3,4-dihydroquinolin-2(1H)-one (2) are synthesized and obtained in the crystalline state for X-ray diffraction studies. In the asymmetric unit of compound 1, there are two independent molecules (A and B) having similar conformations. In the crystals of compounds 1 and 2, individual molecules are linked by pairs of N-H⋯O hydrogen bonds forming A-A and B-B inversion dimers with _{(8) ring motifs. The dimers are stabilized by N-O hydrogen bonds and are linked via C-H⋯O short contact interactions, forming a three-dimensional and two-dimensional networks in 1 and 2 respectively. The network in 2 is further stabilized by a number of C-H⋯p interactions. Compounds 1 and 2 have a dual dopamine D2 and serotonin 5-HT1A receptor profile.}

The trans -[ReO₂(3,5-lut)₄]I₃ complex (trans-dioxotetra(3,5-lutidine)rhenium(V) triiodide) is obtained by the reaction of ReI₃ with 3,5-lutidine (3,5-lut) in acetonitrile. The structure is triclinic, space group PT, a = 8.5224(9) Å, b = 8.9607(9) Å, c = 12.6271(12) Å, α = 76.987(3)°, β = 73.932(3)°, γ = 65.500(3)°, V = 836.44(15) ų, Z = 1, d _calc = 2.040 g/cm³. Re atoms have an octahedral coordination environment formed by N atoms of 3,5-lutidine molecules and О atoms in the trans-position.