Synthesis,structural characterization and in vitro cytotoxic activity of novel polymeric triorganotin(IV) complexes of urocanic acid

Two novel triorganotin carboxylate complexes of the biologically active urocanic acid have been synthesized and characterized. Elemental analysis, melting point, spectroscopic techniques – IR, ¹H, ¹³C and ¹¹⁹Sn NMR – mass spectrometry and X‐ray diffraction studies have been used for structural characterization. Crystal structures of the tin(IV) derivatives show that urocanic acid acts as a bridging bidentate ligand through its imidazole nitrogen atom and its carboxylic group, producing a polymeric one‐dimensional chain. The molecular structures of the complexes, catena‐poly‐tri(n‐butyl)tin(IV) 3‐(3H‐imidazol‐4‐yl)prop‐2‐enoate (1) and catena‐poly‐triphenyltin(IV) 3‐(3H‐imidazol‐4‐yl)prop‐2‐enoate (2), present a distorted trigonal–bipyramidal configuration. This is further confirmed by ¹¹⁹Sn NMR in the solid state. The tin(IV) derivatives form double‐stranded ribbons via N―H^…O―H bonds. Nevertheless, the compounds are essentially monomeric in solution, with a tetrahedral configuration as observed by ¹¹⁹Sn NMR in solution. The cytotoxic activity of the titled compounds has been tested against six human cell lines and the corresponding IC₅₀ values are reported. Both tin(IV) compounds have a high to very high in vitro cytotoxic activity against the tumor cell lines K562, HCT‐15 and MCF‐7. Compound 1 is 86 times more active than cisplatin in the HTC‐15 cell line. Copyright © 2012 John Wiley & Sons, Ltd.     

Tributyltin(IV) Schiff base complexes with amino acid derivatives: synthesis,characterization and biological activity

The synthesis in one‐pot reactions and structural characterization of six new tri‐n‐butyltin(IV) derivatives of Schiff bases are reported. The compounds are derived from a condensation reaction between l ‐alanine, l ‐valine, l ‐isoleucine, l ‐methionine, l ‐phenylalanine or l ‐tryptophan and 3,5‐di‐tert‐butyl‐2‐hydroxybenzaldehyde. Characterization was completed using elemental analysis, infrared spectroscopy, mass spectrometry, one‐ and two‐dimensional solution NMR (¹H, ¹³C and ¹¹⁹Sn) as well as solid‐state ¹¹⁹Sn NMR. In addition, the crystal structures of three of the compounds were confirmed using single‐crystal X‐ray diffraction. Although five‐coordinated and polymeric in the solid state, the tin compounds are four‐coordinated and monomeric in solution. The coordination environment around the triorganotin units comprises three carbon atoms and two oxygen atoms from two ligands in a trigonal bipyramidal geometry. The anti‐proliferative effect of these compounds on the cervical carcinoma cell lines HeLa, CaSki and ViBo was screened in vitro, the compounds showing cytotoxic activity against all three strains and null or low cytotoxic activity (necrotic) as well. Copyright © 2016 John Wiley & Sons, Ltd.     

Slow-light fourier transform interferometer

We describe a new type of Fourier transform (FT) interferometer in which the tunable optical delay between the two arms is realized by using a continuously variable slow-light medium instead of a moving arm as in a conventional setup. The spectral resolution of such a FT interferometer exceeds that of a conventional setup of comparable size by a factor equal to the maximum group index of the slow-light medium. The scheme is experimentally demonstrated by using a rubidium atomic vapor cell as the tunable slow-light medium, and the spectral resolution is enhanced by a factor of approximately 100.     

Is the non-physical states conjecture valid?

The canonical quantization for N = 1 supergravity in the context of gravitational minisuperspace described by Gowdy T ³ and Bianchi class A cosmological models is analyzed in order to search for physical states. There are indeed physical states in the minisuperspace sector of the theory. This fact entails that the non-physical states conjecture has a restricted validity, and in consequence it cannot be considered a general result.     

Critical points in a relativistic bosonic gas induced by the quantum structure of spacetime

It is well known that phase transitions arise if the interaction among particles embodies an attractive as well as a repulsive contribution. In this work it will be shown that the breakdown of Lorentz symmetry, characterized through a deformation in the relation dispersion, plus the bosonic statistics predict the emergence of critical points. In other words, in some quantum gravity models the structure of spacetime implies the emergence of critical points even when no interaction among the particles has been considered.     

Electron density and temperature contour plots from alaser-produced plasma using collective ultraviolet Thomson scattering

Temporally integrated ultraviolet collective Thomson scattering measurements were performed with frequency-quadrupled Nd:YAG laser radiation on an underdense long-scalelength aluminum plasma (n_c ~10²¹ cm^-3, Z≈7, T_e≈T_i ⩾50 eV, L⩾100 μm). The plasma was preformed by an Nd:YAG fundamental beam (1.06 μm) with focusable intensities of 10 ¹¹ W/cm². Color images of two-dimensional (2-D) spatially resolved (30 μm) electron density and electron temperature were obtained. These are the shortest wavelength Thomson scattering measurements on a plasma to date     

Positronium lifetime in polymers

A model describing the relationship between the orthopositronium lifetime and the volume of a void, located in a synthetic zeolite, is analyzed. Our idea, which allows us to take into account the effects of temperature, comprises the introduction of a non-Hermitian term in the Hamiltonian, which accounts for the annihilation of the orthopositronium. The predictions of the present model are also confronted against an already known experimental result.