Coordination and Redox Isomerization in the Reduction of a Uranium(III) Monoarene Complex

Synthetic studies on the redox chemistry of trivalent uranium monoarene complexes were undertaken with a complex derived from the chelating tris(aryloxide)arene ligand (^Ad,MeArO)₃mes^3?. Cyclic voltammetry of [{(^Ad,MeArO)₃mes}U^III] ( 1 ) revealed a nearly reversible and chemically accessible reduction at ?2.495 V vs. Fc/Fc⁺—the first electrochemical evidence for a formally divalent uranium complex. Chemical reduction of 1 indicates that reduction induces coordination and redox isomerization to form a uranium(IV) hydride, and addition of a crown ether results in hydride insertion into the coordinated arene to afford uranium(IV) complexes. This stoichiometric reaction sequence provides structural insight into the mechanism of arene functionalization at diuranium inverted sandwich complexes.     

Temperature dependence of methanol and ethanol vapor sorption in polyhedral oligomeric silsesquioxane (POSS) containing methacrylate membranes

This study aimed to determine the solubility and temperature dependence of methanol and ethanol vapor caused by the difference in the substituents of polyhedral oligomeric silsesquioxane (POSS)-containing polymethacrylate membranes and the spacer length between the backbone and POSS backbone. Vapor sorption of methanol and ethanol was measured at 25°C, 35°C, and 45°C for three kinds of POSS-containing polymer membranes, namely, poly(methacryl isobutyl POSS), poly(methacrylate isobutyl POSS), and poly(methacryl phenyl POSS). The primary structures of the three POSS-containing polymer chains were columnar. The solubility of alcohol vapor on the POSS-containing polymer membranes followed the mechanism of solid adsorption and not the general dissolution diffusion. The sorption amount at all three temperatures was related to the surface area of the cylindrical primary structure and the solid adsorption property of the alcohol molecule of the POSS substituent. The sorption amount increased because of the large surface area and adsorption property of alcohol molecules. Although a typical glassy polymer shows exothermic mixing and a rubbery polymer displays endothermic mixing, the sample with the POSS substituent of isobutyl group exhibited an unusual behavior of endothermic mixing despite being a glassy polymer.     

Photoluminescent Ferroelastic Molecular Crystals

Ferroelasticity has been reported for several types of molecular crystals, which show mechanical‐stress‐induced shape change under twinning and/or spontaneous formation of strain. Aiming to create materials that exhibit both ferroelasticity and light‐emission characteristics, we discovered the first examples of ferroelastic luminescent organometallic crystals. Crystals of arylgold(I)(N‐heterocyclic carbene)(NHC) complexes bend upon exposure to anisotropic mechanical stress. X‐ray diffraction analyses and stress‐strain measurements on these ferroelastic crystals confirmed typical ferroelastic behavior, mechanical twinning, and the spontaneous build‐up of strain. A comparison with single‐crystal structures of related gold‐NHC complexes that do not show ferroelasticity shed light on the structural origins of the ferroelastic behavior.     

Geometrical Evolution and Formation of the Photoproduct in the Cycloreversion Reaction of a Diarylethene Derivative Probed by Vibrational Spectroscopy

The geometrical evolution of the reactant and formation of the photoproduct in the cycloreversion reaction of a diarylethene derivative were probed using time-resolved absorption spectroscopies in the visible to near-infrared and mid-infrared regions. The time-domain vibrational data in the visible region show that the initially formed Franck-Condon state is geometrically relaxed into the minimum in the excited state potential energy surface, concomitantly with the low-frequency coherent vibrations. Theoretical calculations indicate that the nuclear displacement in this coherent vibration is nearly parallel to that in the geometrical relaxation. Time-resolved mid-infrared spectroscopy directly detected the formation of the open-ring isomer with the same time constant as the decrease of the closed-ring isomer in the excited state minimum. This observation reveals that no detectable intermediate, in which the population is accumulated, is present between the excited closed-ring isomer and the open-ring isomer in the ground state.     

Biosynthesis of Indole Diterpene Lolitrems: Radical‐Induced Cyclization of an Epoxyalcohol Affording a Characteristic Lolitremane Skeleton

Lolitrems are tremorgenic indole diterpenes that exhibit a unique 5/6 bicyclic system of the indole moiety. Although genetic analysis has indicated that the prenyltransferase LtmE and the cytochrome P450 LtmJ are involved in the construction of this unique structure, the detailed mechanism remains to be elucidated. Herein, we report the reconstitution of the biosynthetic pathway for lolitrems employing a recently established genome‐editing technique for the expression host Aspergillus oryzae. Heterologous expression and bioconversion of the various intermediates revealed that LtmJ catalyzes multistep oxidation to furnish the lolitrem core. We also isolated the key reaction intermediate with an epoxyalcohol moiety. This observation allowed us to establish the mechanism of radical‐induced cyclization, which was firmly supported by density functional theory calculations and a model experiment with a synthetic analogue.     

Recent Progress in Homogeneous Catalytic Dehydrogenation of Formic Acid

Recently, there has been a strong demand for technologies that use hydrogen as an energy carrier, instead of fossil fuels. Hence, new and effective hydrogen storage technologies are attracting increasing attention. Formic acid (FA) is considered an effective liquid chemical for hydrogen storage because it is easier to handle than solid or gaseous materials. This review presents recent advances in research into the development of homogeneous catalysts, primarily focusing on hydrogen generation by FA dehydrogenation. Notably, this review will aid in the development of useful catalysts, thereby accelerating the transition to a hydrogen-based society.     

Fiber-optic distributed measurement of polarization beat length using slope-assisted Brillouin optical correlation-domain reflectometry

Optical Review - We demonstrate distributed measurement of the polarization beat length along single-mode optical fibers (SMFs) using slope-assisted Brillouin optical correlation-domain...     

Proton Conduction at High Temperature in High-Symmetry Hydrogen-Bonded Molecular Crystals of RuIII Complexes with Six Imidazole-Imidazolate Ligands

A new H-bonded crystal [Ru^III(Him)₃(Im)₃] with three imidazole (Him) and three imidazolate (Im⁻) groups was prepared to obtain a higher-temperature proton conductor than a Nafion membrane with water driving. The crystal is constructed by complementary N−H⋅⋅⋅N H-bonds between the Ru^III complexes and has a rare Icy-c* cubic network topology with a twofold interpenetration without crystal anisotropy. The crystals show a proton conductivity of 3.08×10⁻⁵ S cm⁻¹ at 450 K and a faster conductivity than those formed by only HIms. The high proton conductivity is attributed to not only molecular rotations and hopping motions of HIm frameworks that are activated at ∼113 K, but also isotropic whole-molecule rotation of [Ru^III(Him)₃(Im)₃] at temperatures greater than 420 K. The latter rotation was confirmed by solid-state ²H NMR spectroscopy; probable proton conduction routes were predicted and theoretically considered.