Defect Chemistry, Electrical Properties, and Evaluation of New Oxides Sr2 CoNb1-x Tix O6-δ (0≤x≤1) as Cathode Materials for Solid Oxide Fuel Cells.

The perovskite series Sr2 CoNb1-x Tix O6-δ (0≤x≤1) was investigated in the full compositional range to assess its potential as cathode material for solid oxide fuel cell (SOFC). The variation of transport properties and thus, the area specific resistances (ASR) are explained by a detailed investigation of the defect chemistry. Increasing the titanium content from x=0-1 produces both oxidation of Co3+ to Co4+ (from 0 up to 40 %) and oxygen vacancies (from 6.0 to 5.7 oxygen atom/formula unit), although each charge compensation mechanism predominates in different compositional ranges. Neutron diffraction reveals that samples with high Ti-contents lose a significant amount of oxygen upon heating above 600 K. Oxygen is partially recovered upon cooling as the oxygen release and uptake show noticeably different kinetics. The complex defect chemistry of these compounds, together with the compositional changes upon heating/cooling cycles and atmospheres, produce a complicated behavior of electrical conductivity. Cathodes containing Sr2 CoTiO6-δ display low ASR values, 0,13â€…Ω cm2 at 973 K, comparable to those of the best compounds reported so far, being a very promising cathode material for SOFC.

New perovskite materials of the La(2-x)Sr(x)CoTiO6 series.

Substitution of La(3+) by Sr(2+) in the double perovskite La(2)CoTiO(6) yields materials of the La(2-x)Sr(x)CoTiO(6) series showing a significant amount of trivalent cobalt ions when prepared at ambient atmosphere. The as-prepared compounds can be reduced in severe conditions retaining the perovskite structure while inducing the formation of a large amount of oxygen vacancies. The limit of aliovalent substitution in this series was found to extend up to x = 1. For substitution of La(3+) up to 15% cobalt and titanium are ordered, though the order is progressively lost as x increases; for x≥ 0.30 no ordering is observed as evidenced by magnetic measurements. The ability of these materials to present either cobalt ions in a mixed oxidation state or large amounts of anion vacancies depending on the atmosphere makes them interesting to be further investigated regarding their electrical and electrochemical properties, and hence, their usefulness in some electrochemical devices.

Synthesis, biological activity, and quantitative structure-activity relationship study of azanaphthalimide and arylnaphthalimide derivatives.

A series of quinoline derivatives as aza analogues of the naphthalene chromophore and a series of "nonfused" tricyclic aromatic systems, in particular 5-arylquinolines and 5- or 6-aryl and heteroaryl naphthalene systems, were synthesized and evaluated for growth-inhibitory properties in several human cell lines. The analysis of quantitative structure-antitumor activity relationships for the growth-inhibitory properties is also reported. Findings suggest that these compounds may not express their cytotoxicity via interaction on DNA.

New analogues of amonafide and elinafide, containing aromatic heterocycles: synthesis, antitumor activity, molecular modeling, and DNA binding properties.

Amonafide- and elinafide-related mono and bisintercalators, modified by the introduction of a pi-excedent furan or thiophene ring fused to the naphthalimide moiety, have been synthesized. These compounds have shown an interesting antitumor profile. The best compound, 9, was 2.5-fold more potent than elinafide against human colon carcinoma cells (HT-29). Molecular dynamic simulations and physicochemical experiments have demonstrated that these compounds are capable of forming stable DNA complexes. These results, together with those previously reported by us for imidazo- and pyrazinonaphthalimide analogues, have prompted us to propose that the DNA binding process does not depend on the electronic nature of the fused heterocycle.

Synthesis, biological evaluation and DNA binding properties of novel mono and bisnaphthalimides.

A novel series of mono and bisnaphthalimides was synthesized and their antiproliferative activities were evaluated against three tumor cell lines. Bisnaphthalimides 3 and 4, bearing a pyrazine ring fused to the naphthalimide system, showed activities in the order of 10(-8) microM, similar to elinafide. DNA binding properties and the ability to induce DNA damage were studied for some of the most active compounds.

Synthesis, antitumor activity, molecular modeling, and DNA binding properties of a new series of imidazonaphthalimides.

A series of mono and bisintercalators based on the 5,8-dihydrobenz[de]imidazo[4,5-g]isoquinoline-4,6-dione system were synthesized and evaluated for growth inhibitory properties in several human cell lines. All target compounds showed activity in the micromolar range. Representative compounds were evaluated using UV--vis spectroscopy and viscosimetric determinations, showing that they behave as DNA intercalators. Molecular modeling techniques were used in order to rationalize the moderate activity observed for bisnaphthalimides.