[Mo2 S12 ]2- Complex as a Precursor for In-situ Generation of Molybdenum Sulfide Catalyst During the H2 Evolution.

For decades, the sulfido molybdenum complexes like [MoS4 ]2- , [Mo2 S12 ]2- , [Mo3 S13 ]2- have gained great attention because of their chemical versatility as well as their structural similarity to the edge-plan of the molybdenum disulfide (MoS2 ) which shows promising catalytic ability for the H2 generation. In this work, we report on the investigation of the dinuclear complex [Mo2 S12 ]2- in both organic and aqueous solution. We demonstrate that [Mo2 S12 ]2- is not intact during the H2 evolution catalysis when it is assayed as a homogeneous catalyst in an electrolyte solution (e. g. in DMF or water solvent) nor when it is immobilized on an electrode surface (e. g. mesoporous carbon black). It transforms into the polymeric amorphous molybdenum sulfide [MoS] which subsequently acts as an actual catalyst. We discuss on the possible [Mo2 S12 ]2- to [MoS] transformation mechanism by employing an arsenal of electrochemical analysis, spectroscopic analyses and microscopic analyses. Effects of the electrochemical operating conditions to the [Mo2 S12 ]2- to [MoS] transformation as well as to the chemical nature and the catalytic performance of the [MoS] product are also emphasized.

Electrocatalytic H2 evolution using binuclear cobalt complexes as catalysts.

We report herein on the use of two binuclear cobalt complexes with the N,N'-bis(salicylidene)-phenylmethanediamine ligand as catalysts for the H2 evolution in DMF solution with acetic acid as proton source. Both experimental analyses (electrochemical analysis, spectroscopy analysis) and theoretical analysis (foot-of-the wave analysis) were employed. These catalysts required an overpotential of ca. 470 mV to catalyze the H2 evolution and generated H2 gas with a faradaic efficiency of 85-95% as calculated on the basis of after 5 hour bulk electrolysis. The kinetic investigation showed the maximal TOF value of 50 s-1 on the basis of an ECEC mechanism. Two cobalt centers, standing at a long distance of 4.175 Å, operated independently during catalysis without a synergetic effect or cooperation capability.

Alkoxyamines Designed as Potential Drugs against Plasmodium and Schistosoma Parasites.

Malaria and schistosomiasis are major infectious causes of morbidity and mortality in the tropical and sub-tropical areas. Due to the widespread drug resistance of the parasites, the availability of new efficient and affordable drugs for these endemic pathologies is now a critical public health issue. In this study, we report the design, the synthesis and the preliminary biological evaluation of a series of alkoxyamine derivatives as potential drugs against Plasmodium and Schistosoma parasites. The compounds (RS/SR)-2F, (RR/SS)-2F, and 8F, having IC50 values in nanomolar range against drug-resistant P. falciparum strains, but also five other alkoxyamines, inducing the death of all adult worms of S. mansoni in only 1 h, can be considered as interesting chemical starting points of the series for improvement of the activity, and further structure activity, relationship studies. Moreover, investigation of the mode of action and the rate constants kd for C-ON bond homolysis of new alkoxyamines is reported, showing a possible alkyl radical mediated biological activity. A theoretical chemistry study allowed us to design new structures of alkoxyamines in order to improve the selectivity index of these drugs.