Lights and Shadows of DMSO as Solvent for Tin Halide Perovskites

In 2020 dimethyl sulfoxide (DMSO), the ever-present solvent for tin halide perovskites, was identified as an oxidant for Sn^II. Nonetheless, alternatives are lacking and few efforts have been devoted to replacing it. To understand this trend it is indispensable to learn the importance of DMSO on the development of tin halide perovskites. Its unique properties have allowed processing compact thin-films to be integrated into tin perovskite solar cells. Creative approaches for controlling the perovskite crystallization or increasing its stability to oxidation have been developed relying on DMSO-based inks. However, increasingly sophisticated strategies appear to lead the field to a plateau of power conversion efficiency in the range of 10–15 %. And, while DMSO-based formulations have performed in encouraging means so far, we should also start considering their potential limitations. In this concept article, we discuss the benefits and limitations of DMSO-based tin perovskite processing.     

Transparent carbon nanotube-based driving electrodes for liquid crystal dispersion display devices

We report the fabrication of transparent rigid or flexible liquid crystal dispersion displays driven by electrodes prepared from coating inert substrates with stable aqueous suspensions of single-walled carbon nanotubes (SWNTs) or multiple-walled carbon nanotubes (MWNTs). The SWNT-coated electrodes exhibit a dense nanotube network with a sheet resistivity ( 25 k) about one decade lower than that of their MWNT counterparts. The electro-optical performance of the SWNT-based devices is at least equivalent to that of an indium tin oxide-based display, whereas those driven by MWNT electrodes operate at slightly higher threshold and saturation voltages. The novel, flexible display devices can be repeatedly bent without any noticeable loss of physical characteristics. PACS 42.79.Kr; 61.46.+w; 81.07.De     

Influence of chain structure on crystal polymorphism of poly(lactic acid). Part 1: effect of optical purity of the monomer

The influence of chain structure on crystal polymorphism of poly(lactic acid) (PLA) with high l-lactic acid content (97.8–100 %) is detailed in this contribution. Upon usual processing conditions of PLA, only α and α′ crystals grow, which makes these two polymorphs of major interest for research. The two crystal modifications have similar chain packing, which complicates their quantitative analysis by diffraction methods. The two crystal modifications are instead easily identified by analysis of the crystallization kinetics, which varies not only with temperature, but also with crystal polymorphism. The dependence of the rate of ordering on temperature shows two distinct maxima around 105–110 and 120–125 °C, which are related to growth of α′ and α crystals, respectively. Addition of d-lactic acid co-units leads to a decrease of the overall crystallization rate of PLA, as well as of the rate of spherulite growth (G) of both the crystal modifications. The relative crystallization rates of α and α′ forms are highly affected by stereoregularity, especially in the PLA grades that have a high crystallization rate. A high d-lactic acid content results not only in an overall slower crystal growth, but also in a varied temperature range where each of the two crystal modifications prevail, with a shift to lower temperatures of both the maxima of the G vs. temperature plots, indicating that inclusion of d-lactic acid units in the PLA chain affects crystallization rate of both α and α′ crystal modifications.     

Tuning the Reactivity of a Heterogeneous Catalyst using N-Heterocyclic Carbene Ligands for C−H Activation Reactions

We report the dramatic impact of the addition of N-heterocyclic carbenes (NHCs) on the reactivity and selectivity of heterogeneous Ru catalysts in the context of C−H activation reactions. Using a simple and robust method, we prepared a series of new air-stable catalysts starting from commercially available Ru on carbon (Ru/C) and differently substituted NHCs. Associated with C−H deuteration processes, depending on Ru/C-NHC ratios, the chemical outcome can be controlled to a large extent. Indeed, tuning the reactivity of the Ru catalyst with NHC enabled: 1) increased chemoselectivity and the regioselectivity for the deuteration of alcohols in organic media; 2) the synthesis of fragile pharmaceutically relevant deuterated heterocycles (azine, purine) that are otherwise completely reduced using unmodified commercial catalysts; 3) the discovery of a novel reactivity for such heterogeneous Ru catalysts, namely the selective C-1 deuteration of aldehydes.     

Enantioselective straightforward access to benzo[b]thiophene analogs of Azatoxin

Horner-Wadsworth Emmons olefination followed by asymmetric hydrogenation allowed the first synthetic access to the chiral thiotryptophan with good enantiomeric excess. Oxazolidinone formation followed by a Pictet–Spengler condensation provided the benzothiophenic analog of Azatoxin.     

Tetraacylation of isobutene: first synthesis of 1,3,6,8-tetramethyl-2,7-naphthyridine

The tetxaacetylation of isobutene has been perfomed in AlCl₃/AcCl. Treatment of the crude reaction medium with liquid ammonia yields the title compound.