Ni, Pd, and Pt complexes of a tetradentate dianionic thiosemicarbazone-based O

New tetradentate phenolate O^N^N^S thiosemicarbazone (TSC) ligands and their Ni(ii), Pd(ii) and Pt(ii) complexes were studied. The diamagnetic and square planar configured orange or red complexes show reversible reductive electrochemistry and in part reversible oxidative electrochemistry at very moderate potentials. DFT calculations show essentially pyridyl-imine centred lowest unoccupied molecular orbitals (LUMO) while the highest occupied molecular orbitals (HOMO) receive contributions from the phenolate moiety, the metal d orbitals and the TSC thiolate atom in keeping with UV-vis spectroelectrochemistry. DFT calculations in conjunction with IR spectra showed details of the molecular structures, the UV-vis absorptions were modelled through TD-DFT calculation with very high accuracy. UPS is fully consistent with UV-vis absorption and TD-DFT calculated data and shows decreasing HOMO-LUMO gaps along the series Pd > Pt > Ni.

Absolute energy level positions in tin- and lead-based halide perovskites.

Metal halide perovskites are promising materials for future optoelectronic applications. One intriguing property, important for many applications, is the tunability of the band gap via compositional engineering. While experimental reports on changes in absorption or photoluminescence show rather good agreement for different compounds, the physical origins of these changes, namely the variations in valence and conduction band positions, are not well characterized. Here, we determine ionization energy and electron affinity values of all primary tin- and lead-based perovskites using photoelectron spectroscopy data, supported by first-principles calculations and a tight-binding analysis. We demonstrate energy level variations are primarily determined by the relative positions of the atomic energy levels of metal cations and halide anions and secondarily influenced by the cation-anion interaction strength. These results mark a significant step towards understanding the electronic structure of this material class and provides the basis for rational design rules regarding the energetics in perovskite optoelectronics.

Bistacrines as potential antitrypanosomal agents.

Human African Trypanosomiasis (HAT) is caused by two subspecies of the genus Trypanosoma, namely Trypanosoma brucei rhodesiense and Trypanosoma brucei gambiense. The disease is fatal if left untreated and therapy is limited due to only five non-adequate drugs currently available. In preliminary studies, dimeric tacrine derivatives were found to inhibit parasite growth with IC50-values in the nanomolar concentration range. This prompted the synthesis of a small, but smart library of monomeric and dimeric tacrine-type compounds and their evaluation of antiprotozoal activity. Rhodesain, a lysosomal cathepsin-L like cysteine protease of T. brucei rhodesiense is essential for parasite survival and likely target of the tacrine derivatives. In addition, the inhibition of trypanothione reductase by bistacrines was found. This flavoprotein oxidoreductase is the main defense against oxidative stress in the thiol redox system unique for protozoa.

Novel lead compounds in pre-clinical development against African sleeping sickness.

Human African trypanosomiasis (HAT), also known as African sleeping sickness, is caused by parasitic protozoa of the genus Trypanosoma. As the disease progresses, the parasites cross the blood brain barrier and are lethal for the patients if the disease is left untreated. Current therapies suffer from several drawbacks due to e.g. toxicity of the respective compounds or resistance to approved antitrypanosomal drugs. In this review, the different strategies of drug development against HAT are considered, namely the target-based approach, the phenotypic high throughput screening and the drug repurposing strategy. The most promising compounds emerging from these approaches entering an in vivo evaluation are mentioned herein. Of note, it may turn out to be difficult to confirm in vitro activity in an animal model of infection; however, possible reasons for the missing efficacy in unsuccessful in vivo studies are discussed.

Bistacrine derivatives as new potent antimalarials.

Linking two tacrine molecules results in a tremendous increase of activity against Plasmodia in comparison to the monomer. This finding prompted the synthesis of a library of monomeric and dimeric tacrine derivatives in order to derive structure-activity relationships. The most active compounds towards chloroquine sensitive Plasmodium strain 3D7 and chloroquine resistant strain Dd2 show IC50 values in the nanomolar range of concentration, low cytotoxicity and target the cysteine protease falcipain-2, which is essential for parasite growth.

Rio de La Plata como territorio

El libro abarca varias áreas temáticas. En el primer gruo de temas nos relatan l historia de la región, desde aquellos dias primigenios del supercontinente de gondwana hasta el momento actual, pasando por la gran penetración marina y los enormes y larguisimos procesos que fueron constituyendo la arquitectura geologica e hidrica de la cuenca. Se caracteriza la climatologia de la cuenca y se ocupan del Delta, tambien se trabaja sobre la vegetación y fauna silvestre. Un segundo grupo recorre la historia de nuestra Ribera. El tercer grupo se ocupa de la navegacion comercial y de los puertos. Un cuarto rupo incluye la visión de los navegantes, con la visión desde el puente a lo largo de una vida de practicaje en el Rio. Tambié se tratan sobre el deporte en el Rio, el de la vela y el del remo y sobre la arquitectura ribereña. Dos trabjos versan sbre l relion agua-hombre. Un grupo nutrido de aprtes se refiere a grandes obras que se propone realizar sobre el Rio. Por último, la recopilación se cierra con tres visiones desde Brasil sobre la cuenca

Rio de La Plata como territorio

El libro abarca varias áreas temáticas. En el primer gruo de temas nos relatan l historia de la región, desde aquellos dias primigenios del supercontinente de gondwana hasta el momento actual, pasando por la gran penetración marina y los enormes y larguisimos procesos que fueron constituyendo la arquitectura geologica e hidrica de la cuenca. Se caracteriza la climatologia de la cuenca y se ocupan del Delta, tambien se trabaja sobre la vegetación y fauna silvestre. Un segundo grupo recorre la historia de nuestra Ribera. El tercer grupo se ocupa de la navegacion comercial y de los puertos. Un cuarto rupo incluye la visión de los navegantes, con la visión desde el puente a lo largo de una vida de practicaje en el Rio. Tambié se tratan sobre el deporte en el Rio, el de la vela y el del remo y sobre la arquitectura ribereña. Dos trabjos versan sbre l relion agua-hombre. Un grupo nutrido de aprtes se refiere a grandes obras que se propone realizar sobre el Rio. Por último, la recopilación se cierra con tres visiones desde Brasil sobre la cuenca