Today (year 2020), the globally recognized problem of arsenic (As) contamination of water resources and other environments at toxic levels has been reported in all of the 20 Latin American countries. The present review indicates that As is prevalent in 200 areas across these countries. Arsenic is naturally released into the environment and mobilized from geogenic sources comprising: (i) volcanic rocks and emissions, the latter being transported over thousands of kilometers from the source, (ii) metallic mineral deposits, which get exposed to human beings and livestock through drinking water or food chain, and (iii) As-rich geothermal fluids ascending from deep geothermal reservoirs contaminate freshwater sources. The challenge for mitigation is increased manifold by mining and related activities, as As from mining sites is transported by rivers over long distances and even reaches and contaminates coastal environments. The recognition of the As problem by the authorities in several countries has led to various actions for remediation, but there is a lack of long-term strategies for such interventions. Often only total As concentration is reported, while data on As sources, mobilization, speciation, mobility and pathways are lacking which is imperative for assessing quality of any water source, i.e. public and private.

Fukui functions are related to electron densities, and their interpretation permits the determination of reactivity of atomic centres. However, negative values cannot be interpreted by an “electron density based” model and represent a phenomenon that has been little investigated and understood. Previous works in the literature suggest that they are related to nodes in the wave function. In our investigations we can relate negative values to nitro groups and their position on aromatic systems, as it is a moiety with HOMO electron densities close to “0” related to “electron attracting” groups. This work can help us understand and predict this phenomenon and the associated chemical reactivities. We also pay attention to the influence of the nitro group angle vs. the aromatic ring.

Alkyl-bis(5-hydroxy-3-methyl-1-phenyl-1H-pyrazole-4-carbodithioates) are interesting targets as they are useful complexing agents for transition metal ion extraction. Anyhow, the intents of their synthesis lead to heterocyclic products and not to the desired molecules. To gain insight into the reaction, we carried out a theoretical investigation on the reaction mechanism and the involved activation energies and the relative thermodynamic stabilities of the desired and obtained. GRAPHICAL ABSTRACT

Due to the promising properties of semiconducting polymers they have attracted wide spread interest. During the last decade we have worked on a smart chemistry approach to these substrates and organometallic compounds with special focus on design, synthesis and characterization of materials that could be used in photovoltaic devices. In these materials, one of the most important aspects is high absorbance in the UV-Vis spectrum as a necessary characteristic for high conversion rates of light to electric energy. We were able to show that this can be achieved introducing certain functional groups as, e.g., NO2-moieties. Another important aspect is the interaction with the buffer layers that also form part of the whole photovoltaic device. Here we show that a double layer of CuI/MoO3 increased the energy yield for a large variety of organic substrates along with related results from other leading groups reported in literature.