Sharif Digital Repository

A novel binuclear Mn(II) complex based on a para-nitro substituted amidic ligand (N-(4-nitrophenyl)picolinamide) has been synthesized and characterized by X-ray crystallography. This complex shows a high degree of conversion and epoxide selectivity in Mukaiyama aerobic epoxidation reactions of cyclic olefins in mild conditions  

In the present communication, three bimacrocyclic tweezers linked through azobenzene moiety, Ln (n = 1–3) were synthesized in a multistep route and characterized by x-ray crystallography, IR, 1H and 13C NMR, UV–vis spectroscopy as well as CHN microanalysis. UV–visible spectroscopy established that the irradiation of L1 and L3 with UV light promoted the trans to cis isomerization. Irradiating the reaction mixtures with Hg lamp, significant supramolecular interactions between L1 and L3 with C60 were also found in terms of the association constants calculated by UV–visible spectroscopy, denoting on more pronounced interaction with C60 that in the absence of UV light. The molecular structures of... 

The synthesis and structures of two new octadentate, Schiff-base calixpyrrole macrocycles are presented in which modifications at the meso-substituents (L1) or the aryl spacer between the two pyrrole-imine donor compartments (L2) are introduced. The outcomes of these changes are highlighted in the structures of binuclear Pacman complexes of these macrocycles, [M2(L1)] and [M2(L 2)]. Both palladium and cobalt complexes of the fluorenylmeso- substituted macrocycle H4L1 adopt rigid, but laterally twisted geometries with enclosed bimetallic microenvironments; a consequence of this spatial constraint is an exo-exo-bonding mode of pyridine in the dicobalt complex [Co2(py)2(L1)]. In contrast, the... 

Objectives: The aim of this study was to assess and compare the crystalline structures of both powder and bulk human dental enamel by X-ray diffraction analysis (XRD). Methods: The buccal surfaces of 60 selected noncarious third molars were divided into two groups of powdered and bulk enamel specimens. To prepare enamel powders, the enamel tissues were ground and powdered manually using a mortar and pestle. For bulk samples, the enamel slabs were sectioned using a low-speed diamond saw. The crystalline structures of samples were analyzed by XRD, and the obtained data were analyzed. The values of the lattice parameters were obtained using the equation of hexagonal crystalline structures. The... 

The preparation of two new azulene-based imine ligands N-(2,6-diisopropylphenyl)-6-tBu-1-azulenylmethaneimine, 3, and N-(2,6-diisopropylphenyl)-6-tBu-3-(2,6-diisopropylphenyliminomethyl)-1-azulenylmethaneimine, 4, is described. These imine ligands display stimuli responsive emissive behavior and their fluorescence can be switched on and off by protonation and neutralization with trifluoroacetic acid and trimethylamine, respectively. The cyclometalation of the monoimine ligand by platinum gave the cyclometalated complex [PtMe(SMe2)(3′)], 5, (where the prime denotes the cyclometalated ligand 3). The reaction of 5 with TlPF6 yields the trinuclear bent Pt2Tl complex {[PtMe(SMe2)(3′)]2(μ-Tl)}PF6,... 

The present investigation introduces a new series of cycloplatinated(II) complexes, with the general formula Pt(O-bpy)(Me)(CN-R)] (R = benzyl, 2-naphtyl and tert-butyl), which are able to generate the stable trans-Pt(IV) product in the solution after the reaction with iodomethane. In fact, the trans product is both the kinetic and thermodynamic product of the reaction; this observation was supported by DFT calculations. These Pt(II) complexes are supported by 2,2'-bipyridine N-oxide (O-bpy) and one of several isocyanides as the cyclometalated and ancillary ligands, respectively. These new Pt(II) complexes undergo oxidative addition with MeI to give the corresponding trans-Pt(IV) complexes.... 

An efficient method for the synthesis of functionalized 4H-chromenes via a one-pot three-component condensation reaction of a 2-hydroxybenzaldehyde with an active methylene compound and a carbon-based nucleophile in the presence of a catalytic amount of ZrOCl2·8H2O in water under thermal condition has been described. High yields, simple work-up procedure, performing reactions in water and synthesis of complex molecules with a one-pot procedure are the main advantages of this procedure. In addition, the structure of the product from the condensation of salicylaldehyde, 2-naphthol, and dimedone was confirmed by X-ray crystallography. © 2018 Wiley Periodicals, Inc  

The structural and computational studies of a new molybdenum tetracarbonyl complex of 5,14-dihydro-6,17-dimethyl-8,15-diphenyldibenzo[b,i]-[1,4,8,11]tetraazacyclotetradecine, a 14-membered tetraazaannulene macrocyclic ligand, Me2Ph2H2TAA, were carried out by X-ray crystallography and density functional and natural bond orbital (NBO) theories. The complex showed an interesting intermolecular C-H⋯O hydrogen bond which was supported by n → π∗ interaction, forming a one-dimensional extended chain along the b-axis. Interesting intramolecular C-H⋯π and very short σ → π∗ (C-H⋯CO) interactions stabilized the twisted geometry of the coordinated ligand. © 2019 The Royal Society of Chemistry 2019  

The structural and computational studies of a new molybdenum tetracarbonyl complex of 5,14-dihydro-6,17-dimethyl-8,15-diphenyldibenzo[b,i]-[1,4,8,11]tetraazacyclotetradecine, a 14-membered tetraazaannulene macrocyclic ligand, Me2Ph2H2TAA, were carried out by X-ray crystallography and density functional and natural bond orbital (NBO) theories. The complex showed an interesting intermolecular C-H⋯O hydrogen bond which was supported by n → π∗ interaction, forming a one-dimensional extended chain along the b-axis. Interesting intramolecular C-H⋯π and very short σ → π∗ (C-H⋯CO) interactions stabilized the twisted geometry of the coordinated ligand. © 2019 The Royal Society of Chemistry 2019  

Using restricted Hartree-Fock (RHF) and density functional theory (DFT) methods at gauge invariant atomic orbital (GIAO) condition, chemical shielding of 13C and 15N nuclei of imidazole and its 4-nitro derivative at different temperatures were calculated. Since we have used the realized structures determined by X-ray and neutron diffraction methods, accuracy of calculated results is improved. By partially optimization of structures of 4-nitroimidazole, determined by X-ray crystallography, the obtained results of these structures are also better than nonoptimized structures. Additionally, we have obtained an optimized geometry for hydrogen bond in structures mentioned above. © 2006 Elsevier... 

The delamination phenomenon has been studied in macroscopic scale by different approaches. Here, using micro-mechanical models, it is tried to find the possible relationship between the problem and the stress fields around a fiber. Using the ideas and the results on the free surface cracking of unidirectional composite, the FEM model is developed. The model verification is done by comparing the results by the results obtained in presence of damaged incorporated by the damage theory. Here, on the free surfaces fiber/matrix debonding is applied as a composite damage and the results show a good agreement with the available results  

In this work, we have studied thermal stability of nanoscale Ag metallization and its contact with CoSi 2 in heat-treated Ag(50 nm)/W(10 nm)/Co(10 nm)/Si(1 0 0) multilayer fabricated by sputtering method. To evaluate thermal stability of the systems, heat-treatment was performed from 300 to 900 °C in an N 2 ambient for 30 min. All the samples were analyzed by four-point-probe sheet resistance measurement (R s ), Rutherford backscattering spectrometry (RBS), X-ray diffractometry (XRD), and atomic force microscopy (AFM). Based on our data analysis, no interdiffiusion, phase formation, and R s variation was observed up to 500 °C in which the Ag layer showed a (1 1 1) preferred crystallographic... 

Analytical studies on the effect of charge and magnetic impurities in a spin-polarized electron gas (SPEG) are carried out using a Thomas-Fermi semiclassical approximation (TFSA). The susceptibility matrix of an SPEG is calculated within the TFSA framework. Charge, spin and mixed charge-spin screening lengths are defined and calculated for the bulk metals (Fe, Co and Ni). It is found that these screening lengths do not strongly depend on temperature in metallic samples. Based on the Ruderman-Kittel-Kasuya-Yoshida (RKKY) model, the magnetic response function is then used to calculate the dependence of the exchange coupling between two ferromagnetic layers. It is seen that the exchange... 

In this study the influence of precipitates on the mechanical properties and plastic anisotropy of an age hardenable aluminum alloy during uniaxial loading was investigated using crystal plasticity modeling. The kinetics model of Myhr et al. was used to obtain the solute and precipitate features after different cycles of aging treatment. The amounts of solute, precipitate size and volume fraction, and dislocation density varying during deformation, were used to calculate the slip system strength. An explicit term was obtained based on the elastic inclusion model for the directional dependency of internal stress developed by non-shearable rod shape precipitates. Also, a dislocation evolution... 

A mixture of the platinum(0) complex [Pt(PtBu3)2] and tetrakis(acetonitrile)copper(i) hexafluorophosphate in acetone activated a water molecule and gave the hydride platinum(ii) complex [PtH(CH3CN)(PtBu3)2]PF6, 1, and the hydroxide Cu(i) species. The crystal structure of complex 1 was determined by X-ray crystallography, indicating a distorted square planar geometry around the platinum center. Although three possible mechanisms are proposed for this transformation, monitoring of the reaction using NMR spectroscopy at low temperature reveals that a cooperative pathway involving formation of a Pt0-CuI dative bond complex is the most probable pathway. The hydride platinum complex 1 is stable in... 

Diquaternarization of dipyrido-[2,3-a:2′,3′-c]-phenazine,(dppz) and its analogous dipyrido-[2,3-a:2′,3′-c]-dimethylphenazine,(dppx) using 1,3-dibromopropane afford new water-soluble derivatives of phenazine, propylene-bipyridyldiylium-phenazine (1) and propylene-bipyridyldiylium-dimethylphenazine (2). The compounds have been characterized by means of FT-IR, NMR, elemental analysis and conductometric measurements and their structure were determined by X-ray crystallography. The experimental studies on the compounds have been accompanied computationally by Density Functional Theory (DFT) calculations. The DNA binding properties of both compounds to calf thymus DNA (ctDNA) were investigated by... 

The new water-soluble derivative of pyrazino[2,3-f][1,10] phenanthroline has been synthesized and characterized by conductivity measurement, elemental analysis, FT-IR, 1H NMR, 13C NMR spectroscopic studies, as well as single crystal x-ray crystallography. Theoretical calculations have been performed using the density functional theory (DFT) in order to confirm the structure and understand the electronic structure of the synthesized compound. The DNA binding properties of the compound were investigated by absorption spectroscopy, melting temperature and viscosity measurements. The intrinsic binding constant, Kb, was determined as 7.84 × 103 M−1 at 298 K. Thermodynamic parameters showed that... 

13C chemical shieldings and 14N and 2H electric field gradient (EFG) tensors of L-alanylglycine (L-alagly) dipeptide were calculated at RHF/6-31++G and B3LYP/6-31++G levels of theory respectively. For these calculations a crystal structure of this dipeptide obtained from X-ray crystallography was used. Atomic coordinates of different clusters containing several L-alagly molecules were used as input files for calculations. These clusters consist of central and surrounding L-alagly molecules, the latter forming short, strong, hydrogen bonds with the central molecule. Since the calculations did not converge for these clusters, the surrounding L-alagly molecules were replaced by glycine... 

In the literature, the analytical solutions concerned with the interaction between screw dislocation and surfaces/interfaces have been mainly limited to simple geometries and perfect interfaces. The focus of the current work is to provide an approach based on a rigorous semi-analytical theory suitable for treatment of such surfaces/interfaces that concurrently have complex geometry and imperfect bonding. The proposed approach captures the singularity of the elastic fields exactly. A vast variety of the pertinent interaction problems such as dislocation near a multi-inhomogeneity with arbitrary geometry bonded imperfectly to a matrix, dislocation near the free boundaries of a finite elastic...