Structure–reactivity studies of chloro and isothiocyanato diorganotin (IV) complexes based on multidentate N‐donor ligands: Synthesis,spectral characterization and crystal structures

The reaction of [SnMe₂Cl₂] with the bidentate ligand 4,7‐phenanthroline (4,7‐phen) resulted in the formation of [SnMe₂Cl₂ (4,7‐phen)]_n ( 1a ) which is probably a polymeric chain in solution. On the other hand, the reaction of [SnEt₂Cl₂] with 4,7‐phen afforded the complex [Sn₂Et₄Cl₄ (κ¹‐N‐4,7‐phen)₂(μ‐κ²‐N,N‐4,7‐phen)] ( 1b ) which dissociates in dimethylsulfoxide solution. The reaction of [SnR₂Cl₂] (R = Me, Et) with 2,2′‐biquinoline (biq) yielded the complexes [SnMe₂Cl₂ (κ²‐N,N‐biq)] ( 2a ) and [SnEt₂Cl₂ (κ¹‐N‐biq)₂] ( 2b ) in the solid state. Moreover, the reaction of [SnR₂Cl₂] (R = Me, Et) with the tridentate ligand 4′‐(2‐furyl)‐2,2′:6′,2″‐terpyridine (ftpy) resulted in the formation of ionic penta‐ and hexa‐coordinated tin complexes [SnMe₂Cl (ftpy)][SnMe₂Cl₃] ( 3a ) and [SnEt₂Cl (ftpy)]Cl ( 3b ). The reaction of [SnMe₂ (NCS)₂] with ftpy afforded the hepta‐coordinated complex [SnMe₂ (NCS)₂(ftpy)] ( 4a ). The products were fully characterized using elemental analysis, and infrared, UV–visible, multinuclear (¹H, ¹³C, ¹¹⁹Sn) NMR, DEPT‐135°, HH‐COSY and HSQC NMR spectroscopies. The crystal structure of complex 3a reveals that it contains the simultaneous presence of penta‐ and hexa‐coordinated tin (IV) atoms. Notably, the crystal structure of complex 4a shows that tin (IV) is hepta‐coordinated in a pentagonal bipyramidal geometry SnC₂N₅ by three nitrogen atoms of ftpy, two nitrogen atoms of NCS^? and two Me groups with trans‐[SnMe₂] configuration. These data indicate the influence of halide or pseudo‐halide group on the coordination number and geometry of tin. Hirshfeld surface analysis and two‐dimensional fingerprint plots were calculated for 3a and 4a which show the π–π interaction between molecules in the solid is relatively weak.     

A novel algorithm based on parameterization method for calculation of curvature of the free surface flows

In this paper, a new approach based on parameterization method is presented for calculation of curvature on the free surface flows. In some phenomena such as droplet and bubble, surface tension is prominent. Therefore in these cases, accurate estimation of the curvature is vital. Volume of fluid (VOF) is a surface capturing method for free surface modeling. In this method, free surface curvature is calculated based on gradient of scalar transport parameter which is regarded as original method in this paper. However, calculation of curvature for a circle and other known geometries based on this method is not accurate. For instance, in practice curvature of a circle in interface cells is constant, while this method predicts different curvatures for it. In this research a novel algorithm based on parameterization method for improvement of the curvature calculation is presented. To show the application of parameterization method, two methods are employed. In the first approach denoted by, three line method, a curve is fitted to the free surface so that the distance between curve and linear interface approximation is minimized. In the second approach namely four point method, a curve is fitted to intersect points with grid lines for central and two neighboring cells. These approaches are treated as calculus of variation problems. Then, using the parameterization method, these cases are converted into the sequences of time-varying nonlinear programming problems. With some treatments a conventional equivalent model is obtained. It is finally proved that the solution of these sequences in the models tends to the solution of the calculus of variation problems. For verification of the presented methods, curvature of some geometrical shapes such as circle, elliptic and sinusoidal profile is calculated and compared with original method used in VOF process and analytical solutions. Finally, as a more practical problem, spurious currents are studied. The results showed that more accurate curve prediction is obtained by these approaches than the original method in VOF approach.     

Synthesis,biological evaluation and molecular docking study of dihydropyrimidine derivatives as potential anticancer agents

A series of dihydropyrimidine analogues were prepared via one-pot Biginelli three-component condensation reaction and characterized by NMR, FT-IR, MS spectra, and element analysis. Subsequently, they were screened for in vitro anticancer effect. These analogues revealed good cytotoxic activity against three human cancer cell lines including MCF-7, HepG-2, and A549. Among these analogues, compounds 4d and 4h were the most potent against three cell lines. Cell viability assays indicated 4a and 4c had lower cytotoxicity. In vitro cytotoxicity study on all synthesized compounds demonstrated that introduction of electron withdrawing substituents on C4 position of phenyl ring of dihydropyrimidine contributed to the antiproliferative potency. Moreover, in silico molecular docking results stipulated a sign of good correlation between experimental activity and calculated binding affinity. It proved 4d and 4h as the strongest compounds. Binding modes of analogues proposed the involvement of hydrophobic interactions and hydrogen bonds with Eg5 active site. Structure activity relationship studies indicated that incorporating electron withdrawing substituents on C4 position of phenyl ring of dihydropyrimidine are important for this biological activity.     

Three-dimensional characterization of multiply twinned nanoparticles by high-angle tilt series of lattice images and tomography

A new electron tomography methodology is presented which allows the reconstruction of external particle shape from lattice resolved high-resolution electron microscopy images. The technique is based on the shape-from-silhouette binary backprojection algorithm after filtering of the lattice contrast. The simultaneous availability of particle shape and crystallographic lattice plane orientations allows the correlation of faceting with crystallographic orientations. The method is demonstrated using a multiply twinned decahedral gold nanoparticle. Eligibility limits in terms of degree of convexity are derived.     

Application of Mie theory and fractal models to determine the optical and surface roughness of Ag–Cu thin films

Thin films of Ag/Cu were deposited by reactive DC magnetron sputtering on (001)-oriented Si and glass substrates for various deposition times (4–24 min). These films were characterized by atomic force microscopy (AFM), and a power law scaling was performed on the obtained micrographs to investigate the self-affine nature of the sample morphology, which is indicative of a fractal structure. We applied the Higuchi’s algorithm to the AFM data to determine the fractal dimension of each sample, and the Hurst exponents were computed. The deposition time dependences of these parameters and the grain size distributions estimated from the UV–visible spectra using the Mie theory, allowed us to describe a particle formation mechanism during the deposition process, in which the length of continuous paths of conductive particles increases as the deposition time is increased. In agreement with this explanation, the electrical resistance decreased with the increment of the deposition time.     

Electron beam nanofabrication of ferromagnetic nanostructures in TEM

Electron beam (e-beam) fabrication of nanostructures by transmission electron microscopy (TEM) is rapidly developing into a top-down nanofabrication method for the sub-5 nm fabrication of structures that cannot usually be realised using resist based lithographic techniques or by the focused ion beam patterning methods. We describe the usage of a variety of e-beam shapes, including point and elliptical line focus, as well as a comparison of LaB₆ and field-emission guns (FEGs), to achieve versatile sculpting of nanodot arrays, nanobridges and nanotips. We operate our patterning on free-standing nickel (Ni) thin film laterally connected to a silicon (Si) substrate as well as to free-standing Ni nanotips, where we achieve a novel three-dimensional (3D) nano-sculpting methodology.     

Insights into the current status of privileged N-heterocycles as antileishmanial agents

Molecular Diversity - Leishmania, one of the most important neglected tropical diseases, is endemic in several regions of the world and hence regarded as a serious threat to public health. Major...     

Anti-cancer,anti-oxidant and molecular docking studies of thiosemicarbazone indole-based derivatives

Based on the structural elements of bioactive 3-substituted indoles, a new series of indole–thiosemicarbazone hybrid derivatives were designed, synthesized, and well-characterized using different spectral techniques. The intended scaffolds were screened for their in vitro anti-proliferative activities against breast cancer (MCF-7), lung cancer (A-549), and liver cancer (Hep-G2) cell lines, as well as their anti-oxidant properties. Cytotoxicity studies revealed that compound 6n was the most potent, at least threefold more potent than the commercially available reference drug etoposide, against A-549. In addition, morphological analysis by the acridine orange/ethidium bromide double staining test and flow cytometry analysis confirmed induction of apoptosis in the A-549 cells by compound 6n. In order to validate the experimental results, molecular studies were performed to achieve the possible binding interactions of the most potent compound (6n) and colchicine with tubulin as well as ANP with ATPase domain of topoisomerase IIα active sites. Moreover, the radical scavenging potential of the final derivatives was found to be excellent with the range of 0.015–0.630 µM, comparable to the standard ascorbic acid (0.655 µM).