Home – Home – Jornals – Thermophysics and Aeromechanics 2016 number 2

In this paper, two new algorithms for the simulation of homogeneous random fields are proposed. Both algorithms are based on the widespread algorithm “in rows and columns” for the simulation of the Gaussian fields with special correlation functions. Applying the algorithms developed makes possible to efficiently simulate homogeneous random fields with non-convex correlation functions.

A mixed problem for a one-dimensional heat equation with several versions of initial and boundary conditions is considered. Explicit and implicit schemes are applied for the solution. The sweep method and the iteration methods are used for the implicit scheme for solving the implicit system of equations. The numerical filtration of a finite sequence of results obtained for different grids with an increasing number of nodal points is used to analyze errors of the method and rounding. In addition, to investigate the rounding errors, the results obtained with several lengths of the machine word mantissa are compared. The numerical solution of the mixed problem for the wave equation is studied by similar methods. The occurrence of deterministic dependencies of the error in the numerical method and the rounding on spatial coordinates, time and the number of nodes is revealed. The source models to describe the behavior of errors in terms of time are based on the analysis of the results of numerical experiments for different versions of conditions of problems. In accord with such models, which were verified by the experiment, the errors can increase, decrease or stabilize depending on conditions over time similar to changing the energy or mass.

A numerical algorithm for computing tsunami wave front amplitude is proposed. The first step consists in solving an appropriate eikonal equation. The eikonal equation is solved by the Godunov approach and the bicharacteristic method. The qualitative comparison of the two above methods is described. Then a change in variables associated with the eikonal solution is introduced. At the last step, using the expansion of the fundamental solution of shallow water equations in the sum of singular and regular parts, we obtain the Cauchy problem for the wave amplitude. This approach allows one to reduce computer costs. The numerical results are presented.

In this paper, we present new interesting fourth-order optimal families of Chebyshev-Halley type methods free from second-order derivatives. In terms of computational cost, each member of the families requires two functions and one first-order derivative evaluation per iteration, so that their efficiency indices are 1.587. It is found by way of illustration that the proposed methods are useful in high precision computing environment. Moreover, it is also observed that larger basins of attraction belong to our methods, whereas the other methods are slow and have darker basins, while some of the methods are too sensitive to the choice of the initial guess.

A new approach to the decomposition method of a three-dimensional computational domain into subdomains, adjoint without overlapping, which is based on a direct approximation of the Poincare-Steklov equation at the conjugation interface, is proposed. With the use of this approach, parallel algorithms and technologies for three-dimensional boundary value problems on quasi-structured grids are presented. The experimental evaluation of the parallelization efficiency on the solution of the model problem on quasi-structured parallelepipedal coordinated and uncoordinated grids is given.

An approach to optimization of trading strategies (algorithms) based on indicators of financial markets and evolutionary computation is described. A new version of the differential evolution algorithm for the search for optimal parameters of trading strategies for the trading profit maximization is used. The experimental results show that this approach can considerably improve the profitability of the trading strategies.

In the present paper, approximate analytical and numerical solutions to nonlinear eigenvalue problems arising in the nonlinear fracture mechanics in analysis of stress-strain fields near a crack tip under a mixed mode loading are presented. Asymptotic solutions are obtained by the perturbation method (the small artificial parameter method). The artificial small parameter is a difference between the eigenvalue corresponding to the nonlinear eigenvalue problem and the eigenvalue related to the linear “undisturbed” problem. It is shown that the perturbation technique gives an effective method of solving nonlinear eigenvalue problems in the nonlinear fracture mechanics. Comparison of numerical and asymptotic results for different values of the mixity parameter and hardening exponent shows good agreement. Thus, the perturbation theory technique for studying nonlinear eigenvalue problems is offered and applied to eigenvalue problems arising from the fracture mechanics analysis in the case of a mixed mode loading.

We study the grid-characteristic methods for solving hyperbolic systems using a high order interpolation on unstructured tetrahedral and triangular grids for approximation. We consider the interpolation with orders from the first to the fifth included. Also, one-dimensional finite difference schemes appropriate for the considered methods are given. We study these schemes in terms of stability. The grid-characteristic method on unstructured triangular and tetrahedral grids are successfully used for solving the seismic prospecting problems, including, seismic prospecting in the conditions of the Arctic shelf and permafrost, as well as for solving seismic problems, problems of dynamic deformation and destruction, studying anisotropic composite materials.

Various issues of numerical simulation of supersonic gas flows with allowance for thermochemical nonequilibrium on the basis of fluid dynamic equations in the two-temperature approximation are discussed. The computational tool for modeling flows with thermochemical nonequilibrium is the commercial software package ANSYS Fluent with an additional user-defined open-code module. A comparative analysis of results obtained by various models of vibration-dissociation coupling in binary gas mixtures of nitrogen and oxygen is performed. Results of numerical simulations are compared with available experimental data. 

The aim of this study is to investigate numerically the effects of four vortices on the dynamic, scalar, and turbulent fields of the hydrogen jet. These vortices, which appear in the vicinities of the nozzle, are created by the vortex generators (VGs), and they are assembled with periodicity or symmetry in order, respectively, to give four vortices of the same or opposite direction. A second-order Reynolds stress model is used to investigate asymmetric turbulent jet. The results indicate that the presence of the vortex near the emission jet section noticeably enhances mixing to ensure a good combustion.

A supersonic air flow in a plane channel with a transverse turbulent jet of hydrogen injected through a slot on the bottom wall is simulated. The algorithm for solving the Favre-averaged NavierStokes equations for the flow of a perfect multispecies gas on the basis of the WENO scheme is proposed. The main attention is paid to the interaction of the shock-wave structure with the boundary layers on the upper and lower duct walls under the conditions of an internal turbulent flow. Namely, a detailed study of the structure of the flow is done, and separation and mixing depending on the jet slot width are investigated. It is found that in addition to well-known shock-wave structures produced by the interaction of the free stream with the transverse jet and the bow shock interaction with the boundary layers near the walls, an additional system of shock waves and the flow separation arise on the bottom wall downstream at some distance from the jet. The comparison with the experimental data is performed.

Recent years many flight control systems and industries are employing PID con-trollers to improve the dynamic behavior of the characteristics. In this paper, PID con-troller is developed to improve the stability and performance of general aviation aircraft system. Designing the optimum PID controller parameters for a pitch control aircraft is important in expanding the flight safety envelope. Mathematical model is developed to describe the longitudinal pitch control of an aircraft. The PID controller is designed based on the dynamic modeling of an aircraft system. Different tuning methods namely Zeigler–Nichols method (ZN), Modified Zeigler–Nichols method, Tyreus–Luyben tuning, Astrom–Hagglund tuning methods are employed. The time domain specifications of different tuning methods are compared to obtain the optimum parameters value. The results prove that PID controller tuned by Zeigler–Nichols for aircraft pitch control dynamics is better in stability and performance in all conditions. Future research work of obtaining optimum PID controller parameters using artificial intelligence techniques should be carried out.

A method of formation and heating of СО₂ as a test gas in the settling chamber of a hotshot wind tunnel is considered. To form and heat СО2, the chamber is filled with a source gas mixture of СО, О₂, and СО₂, and after initiation, these substances participate in an exothermic chemical reaction in accordance with the formula СО + 0.5 О₂ + х СО₂ = (1 + х)СО₂. A stoichiometric ratio of the concentrations of carbon monoxide CO and oxygen is used. Variation of the number of moles x of ballast CO₂ in the left part of the chemical formula allows changing the temperature of the resultant test gas in a wide range. Experiments in the IT-302M hotshot wind tunnel carried out at ITAM SB RAS have shown that a pressure increase during an isochoric process in the settling chamber due to the joint effect of heat released in the reaction СО + 0.5 О₂ and an electric charge provides the completeness of CO combustion almost equal to unity. The time of reaction completion at its initiation by an electric arc is no more than several milliseconds.

The structure, ¹⁴N NQR parameters, electronic spectra, and hyperplarizability of [Cr(CO)₅py] in seven different solvents were theoretically computed with MPW1PW91 method based on Polarizable Continuum Model (PCM). The substituent effects in para- substituted Cr(CO)₅-pyridine complexes have been evaluated. The results indicate that both polarity of solvents and the substituents have played a significant role on the structures and properties of complexes. The study also shows that the structural and solvent modification change the NLO properties.

Using MPW1PW91 quantum chemical calculations, we report structures, frontier orbital analysis, natural bond analysis, and aromaticity of the C₅H₅Ir(PH₃)₃ iridabenzene and XC₅H₄Ir(PH₃)₃para-substituted iridabenzenes. The substituent effects were estimated from the donor-acceptor interaction energies of the natural bond orbitals of substituent and iridabenzene frame. Nucleus-independent chemical shift (NICS) has been evaluated to understand the aromaticity. Time dependent density functional theory (TD-DFT) is used to calculate the energy, oscillatory strength and wavelength absorption maxima (l_max) of electronic transitions and their nature. Changes in hyperpolarizability of molecules are studied. Influence of solvent on the structure, frontier orbital energies, λ_max, and hyperpolarizability of C₅H₅Ir(PH₃)₃ iridabenzene has been studied.

Theoretical studies on the lanthanide and actinide triflate complexes M(OTf) _n where M = La, Ce, Gd, Yb, Lu, Th, U, Np, Pu, Am, Cm, Bk, and No; n = 3 and 4, are carried out using functional density theory (DFT). The study of An(OTf)₃ complexes showed that the three OTf groups are bidentate, generating a trigonal prism (TP). Two limiting structures of TP are observed; the most distorted is the thorium triflate Th(OTf)₃ and the ideal one is U(OTf)₃. The highest population contribution of 5 d orbital compared to 5 f orbital in Th-O bond of Th(OTf)₃ explains the distortion. The intramolecular rearrangement of the OTf ligands in Ln(OTf)₃ generates two conformers. In Yb(OTf)₃, the pseudo-eclipsed and the staggered conformations are stable and can be isolated.

Two new compounds of fluorine: (C₂H₅)₄N[I₂F] and (C₂H₅)₄N[Br₂F] have been easily synthesized in a nearly quantitative by a direct reaction of (C₂H₅)₄NF, I₂ and Br₂. The products were isolated and characterized by elemental analysis and spectroscopic methods such as: Fourier transform infrared spectroscopy (FTIR) and ultraviolet-visible spectroscopy (UV-Vis). These compounds have been studied with the Scalar ZORA relativistic level of theory using the ADF program package. The molecular parameters, and vibrational spectra were calculated. The excitation energies were found by time-dependent perturbation density functional theory (TD-DFT). Molecule optimization, frequencies and excitation energies were calculated with standard Slatertype-orbital (STO) basis sets with triple-zeta quality double plus polarization functions (TZ2P) for all atoms. The FTIR, UV-Vis spectra and assignment of principal transitions and total density of state (TDOS) were extracted using the GaussSum 2.2 program. The comparison between experimental and calculated values shows that the experimental results correlate well with the predicted data.

The electron paramagnetic resonance (EPR) parameters (g factors and hyperfine structure constants) for Cu²⁺ in [Cu(ipt)(dap)H₂O] _n × n H₂O (ipt is isophthalic acid, dap - 1,3-diaminopropane) are theoretically investigated from the high order perturbation formulas of these parameters for a 3 d ⁹ ion in a rhombically elongated octahedron. The ligand orbital and spin-orbit coupling contributions are included from the cluster approach because of strong covalency of the system. The nearly axial anisotropies of the g factors and hyperfine structure constants are correlated to the significant elongation distortion of the five-fold coordinated Cu²⁺ (in a distorted square pyramidal [CuN₂O₃] group). Nevertheless, the perpendicular anisotropies arising from the nonequivalent planar ligands are largely concealed by the experimental uncertainties. The theoretical analysis of the EPR behaviours for [Cu(ipt)(dap)H₂O] _n × n H₂O would be helpful to understand the local structures and properties of this and relevant systems.

Synthesis procedures for new coordination compounds of iron(II) with tris(pyrazol-1-yl)methane (HC(pz)₃), containing cluster anions in the outer sphere, of the composition [Fe{HC(pz)₃}₂][Mo₆Cl₁₄]×2H₂O (I), [Fe{HC(pz)₃}₂][Mo₆Br₁₄]×H₂O (II), and [Fe{HC(pz)₃}₂]₂[Re₆S₈(CN)₆]×2H₂O (III) are developed. The compounds are studied by static magnetic susceptibility, electronic, IR, and Mössbauer spectroscopic methods. The magnetochemical study shows that in the polycrystalline phases of all compounds the spin-crossover ¹ А ₁ Û ⁵ - ₂ is observed which is accompanied by thermochromism.

A new dinuclear Fe(III) complex, [Fe(5-MeOL1)(OH)_0.86(CH₃O)_0.14]₂×2(CH₃OH), [H₂-5-MeOL1 = N,N¢-bis(5-methoxy-2-hydroxybenzylidene)-2,2-dimethylpropane-1,3-diamine], 1 has been synthesized and characterized by single crystal structure analysis. The structure of 1 consists of two Fe(III) centers with one tetradentate schiff base ligand (N₂O₂) which are bridged by dihydroxo/dimethoxo groups to yield a Fe₂O₂ core. Complex 1 exhibits weak antiferromagnetic exchange interaction between Fe(III) ions with J = -0.21 cm^-1.

By employing trans -dicyano or pentacyanometalate as building block and using a bicompartimental Schiff-base based manganese(III) compound as assemble segment, two new cyanide-bridged heterometallic Fe(III)-Mn(III) complexes {[Mn(L)(H₂O)][Febpb(CN)₂]}×2CH₃OH (1) and {[Mn(L)(H₂O)]₂×[Fe(CN)₅NO]} (2) (bpb^2- = 1,2-bis(pyridine-2-carboxamido)benzenete, L = N,N¢-ethylene-bis(3-ethoxysalicylideneiminate) have been synthesized and characterized by elemental analysis, IR spectroscopy and X-ray structure determination. Single X-ray diffraction analysis reveals binuclear FeMn and trinuclear FeMn₂ structure, respectively, in which the cyanide precursor acts as mono- or bidentate ligand to connect the Mn(III) Schiff-base unit(s). Furthermore, these two complexes are self-complementary through coordinated aqua ligands from one complex and the free O₄ compartments from the neighboring complex, giving dimeric and 1D single chain supramolecular structure. Investigation of the magnetic susceptibility of 1 reveals weak antiferromagnetic coupling between the adjacent Mn(III) ions. Based on the binuclear FeMn model, best fit of the magnetic susceptibilities of 1 leads to the magnetic coupling constants J = -1.37 cm^-1 and zJ ¢ = - 0.72 cm^-1 (1).

A dimeric [{Fe(5-ClL1)}₂(m-O)], [H₂-5-ClL1 = N,N¢-bis(5-Chloro-2-hydroxybenzylidene)- 2-methylpropane-1,2-diamine] tetradentate Schiff-base complex, 1, has been synthesized and its crystal structure has been determined by single crystal X-ray diffraction analysis. Structural analysis of complex 1 shows that the complex is a centrosymmetric dimer. Each of the Fe(III) ions has a five-coordinate geometry and one oxygen atom bridges two Fe(III) ions to form a m-oxo structure. The geometry around iron atom can be described as a square based pyramid with the FeN₂O₂ coordination plane and oxo ligand.

[Ni(5,5'-dmbipy)₂Cl₂]×3H₂O (1) complex was obtained from the reaction of NiCl₂×6H₂O with 5,5'-dimethyl-2,2'-bipyridine (5,5'-dmbipy) in a mixture of CH₃OH/CH₃CN. This complex was characterized by elemental analysis, IR, UV-Vis and luminescence spectroscopy, and its structure was determined by the single-crystal diffraction method. The Ni atom has a distorted octahedral coordination by four N atoms from two 5,5'-dmbipy ligands and two Cl^- anions.

The single crystal X-ray diffraction (XRD) method was used to determine the structure of the [Cu(mi-tfac)₂] (mi-tfac = MeC(O)CHC(NMe)CF₃) complex at the temperature of 150 K. The crystallographic data are as follows: space group Pnna , a = 11.8798(16) Å, b = 12.0315(16) Å, c = 10.6259(14) Å, V = 1518.8(4) ų, Z = 4, R = 0.0288. The structure is molecular, the coordination environment of copper in the molecule adopts a distorted tetrahedral geometry. The Cu-O and Cu-N distances are 1.9182(13) Å and 1.9610(16) Å respectively, the OCuN chelate angle is 94.18(5)°. The thermal properties of the compounds [Cu(mi-tfac)₂] and [Cu(RC(O)CHC(NMe)R)₂] (R = Me, ^t Bu) in the condensed phase have been studied by the methods of thermogravimetry and differential scanning calorimetry. The thermodynamic characteristics of the melting processes have been determined.

A new Cu (II) complex with bidentate o-phenanthroline (phen) ligand, ([Cu(phen)]₂(H₂PO₄)₂×_{×HPO4)2(H3PO4)4, has been synthesized and characterized by single crystal X-ray diffraction, IR spectroscopy and magnetic data. The crystal structural analysis shows that the title compound contains two phosphate-bridged dimeric units ([Cu(phen)]2(H2PO4)HPO4), which are crystallographically independent. In these units, each copper atom is five coordinated and the geometry around the Cu(II) can be described as slightly distorted square-based pyramidal, with parameter varying between 0.001 and 0.04. The crystal structure is stabilized by O-H…O and C-H…O hydrogen bonds between the dimeric units and the phosphoric acid molecules. In addition, the organic ligands are associated by π-π stacking interactions between neighboring non-nitrogen aromatic rings. The infrared spectrum recorded at room temperature was interpreted on the basis of data published in the literature. The magnetic susceptibilities data show a weak intra-dimer ferromagnetic interaction with J = 31.8 K.}

The preparation of four new copper(II) complexes with different N-donor ligands [CuBr₂×(2-benzylpyridine)₂] (1), [CuBr₂(2-benzylpyridine)(2,2'-bipyridine)]×H₂O (2), [CuBr₂(3-methyl-2-phenylpiridine)₂] (3), [Cu(picolinate)₂]×KI (4) from copper(I) halides as starting material is described. During the preparation of compound 4 a ligand oxidation reaction took place to give the picolinate ligand starting from 2-(2-methylaminoethyl)pyridine. The complexes were characterized by elemental analyses, IR spectroscopy and crystallographic studies. Single crystal X-ray diffraction analysis of the complexes reveals their monomeric penta- and tetracoordinated nature. For all compounds, the copper(II) present a common square planar coordination except for compound 2 which is five coordinated in a quasi-square pyramidal configuration with t of 0.29. The Cu-N distances for these compounds are in the range of 1.959(4)-2.041(3) Å, Cu-O distance was 1.961(3) Å and Cu-Br distances were in the range of 2.4052(4)-2.4381(6) Å for the square base configuration while for apical distance it was 2.6745(7) Å. Magnetic properties have been investigated for all compounds in the temperature range 2-300 K. Compound 1 shows weak antiferromagnetic intermolecular interaction.

A new Zn(II) coordination polymer, {[Zn(npht)(L)_0.5(H₂O)]×H₂O} _n (L = 1,4-bis(2-methylbenzimidazol-1-ylmethyl)benzene, H₂npht = 3-nitrophthalic acid) has been hydrothermally synthesized and characterized by elemental analysis, IR, XRPD, and single-crystal X-ray diffraction. The Zinc(II) coordination compound exhibits a 1D linear chain, which is further assembled into a 2D supramolecular layer via two modes of classial hydrogen bonding interactions. The fluorescence properties and thermal stability of the complex have been investigated in the solid state.

A new coordination polymer, {[Cd(bbmb)(bdc)]} _n (bbmb = 1,1¢-(1,4-butanediyl)bis-(2-methylbenzimidazole), H₂bdc = 1,3-benzenedicarboxylic acid) was synthesized under hydrothermal conditions. The complex was structurally characterized by single crystal X-ray diffraction analyses, infrared spectroscopy (IR), elemental analyses. The compound crystallizes in the monoclinic system, space group P 2₁/ c with a = 10.860(6) Å, b = 13.115(7) Å, c = 21.009(9) Å, b = 120.94(2)°, V = 2567(2) ų, Z = 4, C₂₈H₂₆CdN₄O₄, M_r = 594.93, D_c = 1.540 g/cm³, m = = 0.893 mm^-1. Each cadmium center is six coordinated with four O atoms from two bdc^2- anions, and two N atoms of two bbmb ligands. The complex features a 4-connected 2D (4, 4) sheet with a point symbol {4².6²}. Fluorescence properties of the title complex were investigated.

A two-dimensional (2D) coordination polymer, formulated as [Y₄(m₃-OH)₄(hma)(cba)₅] _n × × n (Hcba) (1), is synthesized by the synergistic coordination of hemimellitate (H₃hma) and 4-chlorobenzoate (Hcba) ligands with Y₂O₃ under hydrothermal conditions. It has been characterized by single-crystal X-ray diffraction, powder XRD, thermogravimetric analysis, elemental analysis and infrared spectroscopy. Single-crystal X-ray diffraction reveals that it crystallizes in the triclinic crystal system, P space group. Unit cell parameters: a = 11.0280(6) Å, b = 14.5791(10) Å, c = 18.9515(12) Å, a = 72.233(6)°, b = 82.641(5)°, g = 70.933(5)°, V = 2741.1(3) ų, Z = 2. The asymmetric unit contains a [Y₄(m₃-OH)₄]⁸⁺ core which is extended into an infinite {[Y₄(m₃-OH)₄]⁸⁺} _n chain along the direction of a axis. Every {[Y₄(m₃-OH)₄]⁸⁺} _n chain is further connected to two neighboring chains by hma^3- ligands along the direction of b axis, forming a 2D yttrium-organic layer in the ab plane. Adjacent layers are further packed with each other via hydrophobic interactions to form a three-dimensional (3D) structure.

New hybrid organic-inorganic complex zirconium and hafnium fluorides with the 4-amino-1,2,4-triazolium cation (C₂H₅N₄)₂MF₆ (M = Zr, Hf, Zr _x Hf_{1- x} ), which crystallize in two polymorphs (monoclinic ( P 2₁/ n , Z = 4) and triclinic ( P , Z = 2)) are synthesized and structurally studied for the first time. The structures of both polymorphs are composed of hydrogen bonded (N-H⋯F and C-H⋯F) 4-amino-1,2,4-triazolium cations protonated via the nitrogen atom in site 1 and complex [M₂F₁₂]^4- anions that are centrosymmetric dimers formed by edge-sharing pentagonal bipyramids MF₇ (M = Zr, Hf, Zr _x Hf_{1- x} ). It is found that in the structures studied 4-amino-1,2,4-triazolium cation occur simultaneously as cis- and trans- conformers. The packing character of structural units in the unit cells of the studied crystals is discussed along with the structure of the neutral and protonated forms of 4-amino-1,2,4-triazole.

A novel inorganic-organic hybrid salt, hexanediammonium heptamolybdate (C₆H₁₈N₂)₂[H₂Mo₇O₂₄]×7H₂O has been synthesized and characterized by elemental analyses, IR, TGA, cyclic voltammetry, UV and X-ray single crystal diffraction. It crystallizes in triclinic space group P -1 with a = 10.0619(2) Å, b = 12.059(2) Å, c = 20.044(3) Å, a = 97.06(1)°, b = 91.56(1)°, g = 110.59(2)° and Z = 2. The crystal structure shows that seven MoO₆ distorted octahedra share edges which have four ranges of Mo-O bond distances. The heptamolybdate anion of the crystal has approximate mm 2 point symmetry and its structure is similar to that observed in other heptamolybdates. The titled compound consists of the protonated hexanediamine cations and the inorganic [H₂Mo₇O₂₄]^4- oxomolybdate anions, linked by hydrogen-bonding interactions.

The title complex [Ru(Cl)₂(CO)(py)₂(AsPh₃)], was synthesized and characterized. The molecular structure and crystal structures are determined by X-ray crystallography. The dihedral angle between the two cis -pyridine rings is 73.3(2)°, which shows that they are almost orthogonal to each other. The molecular structure is stabilized by inter-molecular and intra-molecular C-H…Cl interactions. The molecular structure is further stabilized by interactions between the aromatic rings.

The crystal structures of the compounds with the composition [Rh(H₂O)₅Cl](C₇H₇O₃S)₂ (I) and Cs[Rh(H₂O)₅NO₃](C₇H₇O₃S)₃×H₂O (II) are determined. Crystallographic data for I: a = 10.063(10) Å, b = 7.771(8) Å, c = 13.524(15) Å; b = 100.44(3)°, space group P 2₁, Z = 2, d _calc = 1.823 g/cm³; for II: a = 16.221(3) Å, b = 9.646(19) Å, c = 21.307(4) Å, b = 92.06(3)°, space group P 2₁, Z = 8, d _calc = 1.833 g/cm³. The compounds are characterized by IR spectroscopy and powder X-ray diffraction. The rhodium atoms have a distorted octahedral environment consisting of five oxygen atoms of coordinated water molecules and one chloride ion (I)/oxygen atom of the nitrate ion (II) with the following distances: Rh-O_H2O of 1.993-2.075 Å and Rh-Cl of 2.270 Å for I; Rh-O_H2O of 1.996-2.031 Å and Rh-O_NO3 of 1.990 Å for II.

A novel ladder-like polymeric silver(I) complex, [Ag₂L₂] _n ×2 n H₂O, where L is 3-aminopyrazine-2-carboxylate, was obtained by the reaction of 3-aminopyrazine-2-carboxylic acid and silver oxide in aqueous ammonia. The complex was characterized by elemental analysis, IR spectra and single crystal X-ray determination. The smallest repeat unit contains a [Ag₂L₂] moiety and two water molecules. The Ag⋯Ag distance is 3.176(1) mmol. Each Ag atom is in a Y-shaped coordination, with one carboxylate O and two pyrazine N atoms from two ligands. In the crystal structure of the complex, the dinuclear silver moieties are linked through 3-aminopyrazine-2-carboxylate ligands, to form 1D ladder-like chain along the b axis. The water molecules are linked to the silver chain through hydrogen bonds. There are p⋯p interactions between the chains. The complex showed effective cytotoxic property on human lung cancer cell line A549.

Coordination of a pyridine-based bridging ligand, 4-bpmp, with cadmium nitrate afforded an infinite ladder-type complex {[Cd(4-bpmp)₂(H₂O)Cl₂]} _n (A) (4-bpmp = 1,4-bis(4-pyridylmethyl)piperazine) containing T -shaped building blocks. IR spectra, elemental analysis, and X-ray single-crystal diffraction were carried out to determine the composition and crystal structure of complex A. Inclined interpenetration of infinite ladders was observed in the solid structure. The combined work demonstrates the ability of bipyridyl coordination polymer leads to a novel metal complex with impressive structural motif.

For the first time, the fluoridotantalates(V) with the mono- and diprotonated 4-amino-1,2,4-triazolium cation of the heterocyclic base (C₂H₅N₄)₂TaF₇ and (C₂H₆N₄)TaF₇×H₂O, are synthesized and their crystal structures are determined. The orthorhombic crystals of (C₂H₅N₄)₂TaF₇ (space group Cmc 2₁) are formed of complex [TaF₇]^2- anions with the configuration of monocap trigonal prism and the monoprotonated (C₂H₅N₄)⁺ cations, one of which is statistically disordered. The crystal structure of (C₂H₆N₄)TaF₇×H₂O (space group Pna 2₁) consists of the pentagonal bipyramidal complex [TaF₇]^2- anions, the diprotonated (C₂H₆N₄)²⁺ cations, and the molecules of crystallization H₂O. In the structure of I, the (C₂H₅N₄)⁺ cations simultaneously exist as cis- and trans- conformers. The formation of the diprotonated 4-amino-1,2,4-triazolium cation (C₂H₆N₄)²⁺ was revealed for the first time. Via ionic interactions and N-H⋯F, N-H⋯N, and O-H⋯F hydrogen bonds, the units in I and II are arranged in a three-dimensional structure.

Acyclic tetraazametal gold(III) perrhenate complex [Au(C₉H₁₉N₄)](ReO₄)₂ is synthesized. The 3D crystal structure of the complex is stabilized by weak secondary interactions (N-H…O, C-H…O, С-H…Au hydrogen bonds, and Au…O contacts). The translation sublattice method shows that the motif of the mutual arrangement of cations can be considered to be pseudohexagonal. The product of the thermal decomposition of [Au(C₉H₁₉N₄)](ReO₄)₂ in a hydrogen atmosphere is a mixture of nanocrystalline phases (HCP phases based on Re and Au) with the coherent scattering region of 24 nm and 34 nm, respectively.

In this study, a novel phthalonitrile, 4-chloro-5-(2-((2-hydroxyethyl)( p -tolyl)amino)ethoxy)phthalonitrile (3), and its metallophthalocyanine derivatives (4-6) are prepared by cyclotetramerization with appropriate metal salts in dimethylformamide. The newly prepared compounds have been characterized by several spectroscopic techniques. All compounds are evaluated for their antioxidant and antibacterial potential. For the antioxidant studies, three tests are applied; DPPH (2,2-diphenyl-1-picrylhydrazylradical) scavenging, metal chelating and reducing power activity. Compound 4 exhibits the best DPPH scavenging activity as 35.2 % at 100 mg/L concentration. The metal chelating activities of compounds 3 and 4 are 69.7 % and 56.4 %, respectively. Reducing power activities of compounds 3 and 4 are higher than a-tocopherol which is used as positive control. All compounds show moderate antibacterial activity when compared to the standard antibiotics, amikacin and tetracycline.

A new tetranuclear complex [Cu₄(L)₄] (1) (H₂L = N-(2-hydroxyethyl)-3-metoxysalicylaldimine) has been synthesized and characterized by crystal structure analysis and magnetic susceptibility. Single-crystal X-ray diffraction studies reveal that complex 1 contains three independent Cu₄O₄ open-cubane cores of 4+2 type (four short and two long Cu⋯Cu distances), where the copper(II) centers are linked by alkoxo-bridges. Each copper(II) ion have a distorted square-pyramidal geometry. Variable-temperature magnetic susceptibility measurements on the tetranuclear complex 1 in the range 2-300 K indicate dominant antiferromagnetic coupling ( J = -108.46) between copper(II) centers.

A silver(I) complex of arginine (arg), [Ag(arg)]NO₃×0.5H₂O (1) was prepared and characterized by elemental analysis, IR and NMR spectroscopy, and X-ray crystallography. The IR and NMR spectroscopic data confirmed the coordination of the ligand to silver(I). The structure of 1 shows that it is polymeric with each silver atom bound to the carboxyl O atom of one arginine ligand and to the amino N atom of another adopting a linear coordination environment. The two coordinate N-Ag-O units are repeated to form infinite chains. The molecular structure is stabilized by N-H…O and C-H…O hydrogen bonds. Antimicrobial activities of the complex were evaluated by minimum inhibitory concentration against gram-negative bacteria ( E. coli , P. aeruginosa ), molds ( A. niger, P. citrinum ) and yeasts ( C. albicans, S. cerevisiae ).