Neutral Gold Complexes with Tridentate SNS Thiosemicarbazide Ligands

Na[AuCl4].2H(2)O reacts with tridentate thiosemicarbazide ligands, H(2)L1, derived from N-[N',N'-dialkylamino(thiocarbonyl)]benzimidoyl chloride and thiosemicarbazides under formation of air-stable, green [AuCl(L1)] complexes. The organic ligands coordinate in a planar SNS coordination mode. Small amounts of gold(I) complexes of the composition [AuCl(L3)] are formed as side-products, where L3 is an S-bonded 5-diethylamino-3-phenyl-1-thiocarbamoyl-1,2,4-triazole. The formation of the triazole L3 can be explained by the oxidation of H(2)L1 to an intermediate thiatriazine L2 by Au3+, followed by a desulfurization reaction with ring contraction. The chloro ligands in the [AuCl(L1)] complexes can readily be replaced by other monoanionic ligands such as SCN- or CN- giving [Au(SCN)(L1)] or [Au(CN)(L1)] complexes. The complexes described in this paper represent the first examples of fully characterized neutral Gold(III) thiosemicarbazone complexes. All the [AuCl(L1)] compounds present a remarkable cell growth inhibition against human MCF-7 breast cancer cells. However, systematic variation of the alkyl groups in the N(4)-position of the thiosemicarbazone building blocks as well as the replacement of the chloride by thiocyanate ligands do not considerably influence the biological activity. On the other hand, the reduction of Au-III to Au-I leads to a considerable decrease of the cytotoxicity.

Molecular organization and doping in poly(2-methoxyaniline)/Ni(dmit)(2) films obtained with the Langmuir-Blodgett technique

The control of the properties of materials at the molecular level is pursued for many applications, especially those associated with nanostructures. In this paper, we show that the coordination compound [Ni(dmit)(2)], where (dmit) is the 1,3-dithiole-2-thione-4,5-dithiolate ligand, can induce doping of poly(2-methoxyaniline) (POMA) in molecularly ordered Langmuir and Langmuir-Blodgett (LB) films. Doping was associated with interactions between the components and the compression of the Langmuir film at the air-water interface, according to polarization-modulated infrared reflection-absorption spectroscopy (PM-IRRAS) data. Taking these results together with in situ UV-Vis absorption measurements, we could identify the molecular groups involved in the interaction, including the way they were reoriented upon film compression. The Langmuir films were sufficiently stable to be transferred as Y-type LB films, while the hybrid POMA/[Ni(dmit)(2)] films remain doped in the solid state. As expected, the molecular charges affected the film morphology, as observed from combined atomic and electric force microscopy measurements. In summary, with adequate spectroscopy and microscopy tools we characterized molecular-level interactions, which may allow one to design molecular electronic devices with controlled electrical properties.

Stable water isotopes of precipitation and firn cores from the northern Antarctic Peninsula region as a proxy for climate reconstruction

In order to investigate the climate variability in the northern Antarctic Peninsula region, this paper focuses on the relationship between stable isotope content of precipitation and firn, and main meteorological variables (air temperature, relative humidity, sea surface temperature, and sea ice extent). Between 2008 and 2010, we collected precipitation samples and retrieved firn cores from several key sites in this region. We conclude that the deuterium excess oscillation represents a robust indicator of the meteorological variability on a seasonal to sub-seasonal scale. Low absolute deuterium excess values and the synchronous variation of both deuterium excess and air temperature imply that the evaporation of moisture occurs in the adjacent Southern Ocean. The delta O-18-air temperature relationship is complicated and significant only at a (multi)seasonal scale. Backward trajectory calculations show that air-parcels arriving at the region during precipitation events predominantly originate at the South Pacific Ocean and Bellingshausen Sea. These investigations will be used as a calibration for ongoing and future research in the area, suggesting that appropriate locations for future ice core research are located above 600 m a.s.l. We selected the Plateau Laclavere, Antarctic Peninsula as the most promising site for a deeper drilling campaign.

Development of paper based electrodes: From air-breathing to paintable enzymatic cathodes

This work presents the results from the development of bio-cathodes for the application on paper-based biofuel cells. Our main goal here is to demonstrate the possibility of using different designs of air-breathing bio-cathodes and ink-based bio-cathodes for this new type of paper based electrochemical cell. The electrochemical performance for the bio-electrocatalytic oxygen reduction reaction was studied by using open circuit voltage and amperometry measurements, as well as polarization curves to probe the four-electron reduction reaction of ambient oxygen catalyzed by bilirubin oxidase (BOx). The electrochemical measurements showed that all procedures allowed the direct electron transfer from the active site of the bilirubin oxidase to the electrode surface with a limiting current density of almost 500 mu A cm(-2) for an air-breathing BOx cathode and 150 mu A cm(-2) for an ink based BOx cathode. Under a load of 300 mV a stable current density was obtained for 12 h of continuous operation. (C) 2012 Elsevier Ltd. All rights reserved.