Claudio Luis Donnici

In this work; resistive moisture sensors were obtained by dip coating sulfonated polycarbonate (SPC) onto silver interdigitated electrodes. Commercial polycarbonate was sulfonated with acetyl sulphate at two different sulfonation degrees corresponding to 9.0 and 18.0 mole %. Impedance spectroscopy was used to investigate the humidity sensing properties at controlled relative humidity (RH%) environments generated from standard saline solutions in the range of 11–90 RH%. For the highest sulfonated sample; in the RH% range investigated (11 to 90%); the sensor impedance changed from 4.7 MΩ to 18 kΩ. Humidity sensors made from sulfonated polycarbonate showed exponential decay behavior of the impedance at constant frequency with the environmental relative humidity. Sample 9SPC presented dielectric relaxation response for environmental humidity between 58 and 90 RH% while sample 18SPC presented dielectric relaxation response for the entire measured range between 11 and 90 RH%. Sulfonated polycarbonate could be a promising material for the fabrication of simple and cheap humidity-sensing sensors for the assessment of relative humidity of the surrounding environment, as suggested by experimental results.

Summary: The in vitro antifungal activity of ruthenium dithiocarbamate compounds (1–5) was investigated and assessed for its activity against seven different species of Aspergillus (Aspergillus clavatus, Aspergillus flavus, Aspergillus fumigatus, Aspergillus niger, Aspergillus nomius, Aspergillus tamarii and Aspergillus terreus). Analysis of in vitro susceptibility was performed using broth microdilution assay following the Clinical and Laboratory Standards Institute guidelines for filamentous fungi. The cytotoxicity was evaluated using 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide assay. Aspergillus clavatus and A. fumigatus were more susceptible species for complexes 1 and 2. Other complexes showed excellent minimum inhibitory concentration (4–64 μg ml⁻¹) against most microorganisms. Complexes 1 and 2 are respectively 180‐ and 95‐fold more active than the corresponding free ligands against A. clavatus and the complex 5 is 46‐fold more active than free ligand against A. niger. Aspergillus niger was more susceptible to the action of the complexes 1 and 5 (16 μg ml⁻¹). A low cytotoxic activity (IC₅₀ > 10⁻⁶ mol l⁻¹) on normal mammalian cells (BHK‐21) to the evaluated complexes was measured. Ruthenium complexes are promising antifungal agents against the development of novel effective drug against different species of Aspergillus; however, for A. nomius and A. terreus, they were not active in the highest concentration tested.

The study on reactivity of several α-substituted α-sulfonyl malonates toward 1,4-diazabicyclo[2.2.2]octane (DABCO) and Bu₃N is described. The reactivity with DABCO revealed the possible competition between decarbalkoxylation and unexpected desulfonylation, depending on the α-substituent, because of sterical hindrance around the electrophilic centers (SO₂ and CO₂R). The derivatives with crowded α-substituents suffer selective desulfonylation, and a novel and efficient desulfonylation method can be proposed. The dependence of the reactivity of α-sulfonyl malonates on the sterical hindrance around the electrophilic centers is confirmed by conformational analysis (Macromodel/MM2∗ and Mopac/MP3). The carbanionic mechanism is proved because the corresponding protonated, deuterated, and sulfenylated products were obtained by addition of the corresponding electrophilic agents. Bu₃N showed itself to be a novel selective decarbalkoxylation agent for any α-substituted α-sulfonyl malonate.