Quantum-chemical interpretation of the isomer shift on tin compounds

Molecular orbital calculations (EHT, IEHT, IEHT + Madelung correction) have been applied to a series of tin halides. A calculation procedure is described to derive the charge density of the electrons at the nucleus (0). The dependence of the isomer shift on covalency effects is demonstrated. The influence of the outer charge of the molecules on the isomer shift is shown. The relative change of nuclear charge radius R/R is calculated for tin.     

Adsorption of nicotinic acid on the surface of nanosized hydroxyapatite and structurally modified hydroxyapatite

In the present paper, hydroxyapatite and structurally modified hydroxyapatite were investigated to establish the best material for nicotinic acid adsorption. Structurally modified hydroxyapatite wa prepared by adding sodium silicate in the reaction medium. The influence of silica concentration, presence of small amounts of metal ions, temperature and initial concentrations of nicotinic acid solutions on the adsorption capacity, were studied. Results indicated that structurally modified hydroxyapatite doped with copper adsorbed the highest amount of nicotinic acid. For this material the adsorption capacity was 0.232 mg nicotinic acid / g material, at an initial concentration of 10⁻⁴ M nicotinic acid. For all types of materials, best results were obtained at 15°C. The amount of nicotinic acid adsorbed increases with the decrease in temperature and with the increase in the initial concentration of nicotinic acid. Adsorption kinetics data were modeled using pseudo-first and pseudo-second order models while the interference due to diffusion was analyzed with intraparticle diffusion model. The results indicate that pseudo-second order model best describes the adsorption kinetics data, indicating the formation of chemical bonding.     

Intramolecular mobility of pentacoordinated tin compounds

The ¹¹⁹Sn NMR and ¹³C NMR data are reported for N-alkyl-5,5-di-t-butyldiptychoxazstannolidines. The activation parameters of an intramolecular process are estimated from the temperature dependence of the ¹H NMR spectra in different polar solvents, The NMR data support the dissociation—inversion mechanism for this process.     

Intramolecular mobility of pentacoordinated tin compounds

The ¹H and ¹³C NMR data for some N-methyl-5,5-dialkyldiptychthiaazstannolidines are reported. The differing coupling constants of the proton signals of the two nonequivalent Sn-alkyl groups suggest apical/equatorial positions for these groups at the pentacoordinated tin atom. The observed intramolecular process is explained by a dissociation-inversion mechanism.     

Growth of hydroxyapatite nanocrystals on polymer particle surface

In the present paper, we describe the preparation of hybrid particles consisting of polymeric core with deposited hydroxyapatite (HAp) nanocrystals. Polystyrene submicron particles modified by β-diketone groups have been used as templates for the growth of HAp. Hybrid particles with HAp nanocrystal content between 7 and 50 wt% have been prepared. Microscopy studies indicate that hybrid particles exhibit “raspberry” morphology, and HAp nanoparticles are not homogeneously distributed on the polymer particle surface. The increase in the HAp content on the polymer particle surface reduces the colloidal stability of the hybrid particles because of the vanishing of the surface charge.     

Microanalytical determination of tin in organotin compounds

Existing procedures for the determination of tin in organotin compounds are reviewed, and a new procedure is described which can be used for the rapid microanalysis of most organotin compounds. Wet oxidation with sulphuric acid and 30% hydrogen peroxide is followed by spectrophotometric determination of the extracted ternary tin(IV)-chloride-oxine complex in chloroform. Time for a single determination is 20 min, and the relative standard deviation is 0.7% for 1-5 mg of tin. On account of their volatility, methyltin compounds must be subjected to a sealed-tube wet oxidation in sulphuric-nitric acid mixture. Addition of sulphamic acid after boiling to remove most of the nitric acid makes this compatible with the solvent extraction step. Tin present as organotin stabilizer in PVC samples can also be determined by this method, after destruction of the organic matter with sulphuric acid and 50% hydrogen peroxide.     

Quantum chemical studies on newly synthesized tin anticancer compounds

The electronic structure of newly synthesized tin anticancer complexes coordinating one, two and four tin atoms has been studied both at semiempirical level and by using ab initio methods at the correlation level. The most probable structures of the systems under consideration have been determined being in a good agreement with the relevant experimental results. The compounds show very effective antitumor cytotoxic activity against A549 and HSMC cells.     

The direct synthesis of triorgano tin compounds

The synthesis of triorganotin halides directly from tin is described. The addition of an alkyl halide to tin metal dispersed in a molten quaternary halide rapidly and selectively produces the trialkyltin halide and a by-product containing the quaternary as a tin halide complex. The quaternary halide, the tin, and the halide ion are all recovered from the by-product by electrolysis and reused.     

Application of tin and nanometer tin in allylation of carbonyl compounds in tap water

[reaction: see text] Nanometer tin-mediated allylation of aldehydes or ketones in distilled or tap water gave rise to corresponding homoallyl alcohol in high yield without any other assistance such as heat or supersonic or acidic media.     

Photoreduction of carbonyl compounds by tributyl tin hydride

The photochemical reactions of cyclohexanone, acetone, l-naphthaldehyde, 2-naphthaldehyde, and 2-acetonaphthone with tributyltin hydride are chain processes leading to the tributyltin ethers of the derived alcohols as the major products, and the analogous ethers of the corresponding pinacols as the most abundant minor products, rather than simple reductions to the alcohols themselves as previously reported. Chain termination for the reductions of those compounds that have a n,π^* triplet state occurs primarily by coupling of tributyltin radicals to form hexabutyiditin, but by coupling of the ketyl radicals to form pinacol ethers for those compounds that have a π,π^* triplet state. Ring reduction is an important process for the aromatic compounds with π, π^* triplet states that were studied. Analyses were performed using 1H, 13C and 119 Sn NMR.     

Substoichiometric determination of inorganic tin in organotin compounds

Inorganic tin(IV) present in organotin compounds is determined substoichiometrically by complexation with salicylideneamino-2-thiophenol in a non-aqueous medium, after isolation of the tin(IV) by iodide extraction. The method is applied to the degradation products in commercial chemicals and those formed by u.v.-irradiation.     

Bilayers coating on titanium surface: The impact on the hydroxyapatite initiation

Most of the actual orthopaedic devices, widely made of titanium and its alloys, present different weaknesses like ions release and risks of loosening over a long period. To solve such problems, new developments in surface modification are crucial. This work is an extension of our recent effort on the development and improvement of a multifunctional inorganic/organic bilayers coating. A thin tantalum oxide layer is formed by sol–gel synthesis followed by the modification with organophosphonic acids of the tantalum oxide layer. We focus in particular on the effect of the bilayers coating on corrosion resistance and hydroxyapatite growth rate by immersion in a simulated body fluid solution. It is also highlighted that the structure of the organophosphonic acid is of major importance on the osteoinduction character of the material.     

Platinum nanoparticles on the antimony-doped tin dioxide surface: Quantum-chemical modeling

The interaction of Pt₂₉ nanoparticles with pristine and reduced (110) and (100) SnO₂ surfaces doped with Sb has been modeled using the density functional theory method within the generalized gradient approximation (GGA). It has been demonstrated that the introduction of antimony contributes to dispersion of substrate particles and, in some cases, leads to an increase in the energy of interaction with platinum and to the fixation of platinum nanoparticles on the surface.     

Spot identification of tin dioxide and organic tin compounds through pyrolytic conversion into stannous chloride

Summary Tin dioxide and organic tin compounds can be conveniently and sensitively identified through their pyrolytic conversion into tin(II) chloride, which is detected with phosphomolybdic acid.

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Zusammenfassung Zinndioxid und organische Zinnverbindungen können durch pyrolytische Umwandlung zu Zinn(II)-chlorid empfindlich nachgewiesen werden, das mit Phosphomolybdänsäure unter Blaufärbung reagiert.

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Résumé On peut identifier, d'une manière sensible et pratique, l'oxyde stannique et l'étain présent dans les composés organiques, en les transformant par pyrolyse en chlorure stanneux. On décèle ce dernier par l'acide phosphomolybdique.

     

Two new dibenzobicyclic penta- and hexacoordinated tin compounds

Two new dibenzobicyclic penta- andhexacoordinated tin compounds ( 1–2 ) were prepared, derived from bis(2-hydroxy-3,5-di-tert-butyl-phenol)imine and dichloro-dimethylstannane and trichloro-n-butylstannane, respectively. Each compound is an example of two different coordination forms of the ligand. The crystalline complexes have been characterized by magnetic moment, infrared and mass spectrometry, elemental analysis, and X-ray diffraction studies. Compound 1 crystallized in the monoclinic system, space group P2₁/n; it contains a five-coordinated trigonal bipyramidal tin atom with methyl groups in equatorial positions and a planar dibenzobicyclic ring. It is a paramagnetic compound (μ_eff = 1.59 μ_B) due to the radical dianion nature of the ligand. Compound 2 crystallized also in the monoclinic system, space group P2₁/c; it contains a six-coordinated tin atom with an octahedral geometry; the dibenzobicyclic ring is planar, and the chlorine atoms are in trans positions. It is diamagnetic with a delocalized monoanion structure of the ligand. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:321–326, 1998