Gating the Trafficking of Molecules across Vesicular Membrane Composed of Dual-Cavity Baskets

Gating the Trafficking of Molecules across Vesicular Membrane Composed of Dual-Cavity Basket

Anion-Redox Mechanism of MoO(S₂)₂(2,2′-bipyridine) for Electrocatalytic Hydrogen Production

Redox processes of molybdenum-sulfide (Mo-S) compounds are important in the function of materials for various applications from electrocatalysts for the hydrogen evolution reaction (HER) to cathode materials for batteries. Our group has recently described a series of Mo-S molecular HER catalysts based on a MoO­(S₂)₂L₂ structural motif. Herein, reductive pathways of MoO­(S₂)₂bpy (Mo-bpy) (bpy = 2,2′-bipyridine) are presented from both experimental and theoretical studies. We tracked chemical reduction of Mo-bpy with UV–vis spectroscopy using sodium napthalenide (NaNpth) as the reducing agent and found that Mo-bpy undergoes anionic persulfide reduction to form the tetragonal Mo­(VI) complex [MoOS₃]^2–. We also identified silver mercury amalgam as an inert working electrode (WE) for spectroectrochemical (SEC) studies. UV–vis spectra in the presence of trifluoroacetic acid with an applied potential confirmed that Mo-bpy maintains its structure during catalytic cycling. Finally, theoretical catalytic reaction pathways were explored, revealing that Mo=O may function as a proton relay. This finding together with the observed anion reduction as the redox center is of broad interest for amorphous Mo-S (a-MoS_<i>x</i>) electrocatalytic materials and anion-redox chalcogel battery materials

Electron Transfer Kinetics of a Series of Bilayer Triphenylamine–Oligothiophene–Perylenemonoimide Sensitizers for Dye-Sensitized NiO

A series of triphenylamine (TPA)–oligothiophene–perylenemonoimide (PMI) molecules, denoted as the BH dyes, which mimic membrane lipid bilayers to enable stable operation of dye-sensitized NiO photocathodes under extremely acidic (pH = 0) conditions, have been recently reported for solar hydrogen production. In this work, we systematically study the photophysical properties of the BH series molecules with various lengths of π-linkers in solution via density functional theory (DFT) calculations and time-resolved spectroscopic techniques. When dissolved in DMF, the molecules undergo ultrafast intramolecular charge transfer within 1 ps upon photoexciation. The charge-separated state then recombines within tens of picoseconds. The electron transfer kinetics of dye-sensitized mesoporous NiO photocathodes exhibit both fast and slow charge recombination processes (70 ps and 4.5 μs, respectively, for BH4). The effect of various lengths of π-linkers is modeled with a spatial attenuation factor of 0.20 Å^–1 with a longer spatial separation of charge recombination centers, giving rise to a slower recombination rate between the reduced dye species and NiO surface

Assembly and Folding of Twisted Baskets in Organic Solvents

A synthetic method for obtaining enantiopure and twisted baskets of type (<i>P</i>)-<b>3</b> is described. These chiral cavitands were found to fold quinoline gates, at the rim of their twisted platform, in acetonitrile and give molecular capsules that assemble into large unilamellar vesicles. In a less polar dichloromethane, however, cup-shaped (<i>P</i>)-<b>3</b> packed into vesicles but with the quinoline gates in an unfolded orientation. The ability of twisted baskets to form functional nanostructured materials could be of interest for building stereoselective sensors and catalysts