One-way biohydrogen transfer for oxidation of sec-alcohols

Quasi-irreversible oxidation of sec-alcohols was achieved via biocatalytic hydrogen transfer reactions using alcohol dehydrogenases employing selected ketones as hydrogen acceptors, which can only be reduced but not oxidized. Thus, only 1 equiv of oxidant was required instead of a large excess. For the oxidation of both isomers of methylcarbinols a single nonstereoselective short-chain dehydrogenase/reductase from Sphingobium yanoikuyae was identified and overexpressed in E. coli.     

Desymmetrizing Heteroleptic [Cu(P^P)(N^N)][PF6] Compounds: Effects on Structural and Photophysical Properties,and Solution Dynamic Behavior

The preparation, characterization and electrochemical and photophysical properties of a series of desymmetrized heteroleptic [Cu(P^P)(N^N)][PF₆] compounds are reported. The complexes incorporate the chelating P^P ligands bis(2-(diphenylphosphanyl)phenyl)ether (POP) and (9,9-dimethyl-9H-xanthene-4,5-diyl)bis(diphenylphosphane) (xantphos), and 6-substituted 2,2′-bipyridine (bpy) derivatives with functional groups attached by –(CH₂)_n– spacers: 6-(2,2′-bipyridin-6-yl)hexanoic acid (1), 6-(5-phenylpentyl)-2,2′-bipyridine (2) and 6-[2-(4-phenyl-1H-1,2,3,triazol-1-yl)ethyl]-2,2′-bipyridine (3). [Cu(POP)(1)][PF₆], [Cu(xantphos)(1)][PF₆], [Cu(POP)(2)][PF₆], [Cu(xantphos)(2)][PF₆], and [Cu(xantphos)(3)][PF₆] have been characterized in solution using multinuclear NMR spectroscopy, and the single crystal structure of [Cu(xantphos)(3)][PF₆]^.0.5Et₂O was determined. The conformation of the 6-[2-(4-phenyl-1H-1,2,3,triazol-1-yl)ethyl]-substituent in the [Cu(xantphos)(3)]⁺ cation is such that the α- and β-CH₂ units reside in the xanthene ‘bowl’ of the xantphos ligand. The 6-substituent desymmetrizes the structure of the [Cu(P^P)(N^N)]⁺ cation and this has consequences for the interpretation of the solution NMR spectra of the five complexes. The NOESY spectra and EXSY cross-peaks provide insight into the dynamic processes operating in the different compounds. For powdered samples, emission maxima are in the range 542–555 nm and photoluminescence quantum yields (PLQYs) lie in the range 13–28%, and a comparison of PLQYs and decay lifetimes with those of [Cu(xantphos)(6-Mebpy)][PF₆] indicate that the introduction of the 6-substituent is not detrimental in terms of the photophysical properties.     

Measurement of the beta+ and orbital electron-capture decay rates in fully ionized, hydrogenlike, and heliumlike 140Pr ions

We report on the first measurement of the beta+ and orbital electron-capture decay rates of 140Pr nuclei with the simplest electron configurations: bare nuclei, hydrogenlike, and heliumlike ions. The measured electron-capture decay constant of hydrogenlike 140Pr58+ ions is about 50% larger than that of heliumlike 140Pr57+ ions. Moreover, 140Pr ions with one bound electron decay faster than neutral 140Pr0+ atoms with 59 electrons. To explain this peculiar observation one has to take into account the conservation of the total angular momentum, since only particular spin orientations of the nucleus and of the captured electron can contribute to the allowed decay.     

Aggregation-Induced Dual Phosphorescence from (o-Bromophenyl)-Bis(2,6-Dimethylphenyl)Borane at Room Temperature

Designing highly efficient purely organic phosphors at room temperature remains a challenge because of fast non-radiative processes and slow intersystem crossing (ISC) rates. The majority of them emit only single component phosphorescence. Herein, we have prepared 3 isomers (o, m, p-bromophenyl)-bis(2,6-dimethylphenyl)boranes. Among the 3 isomers ( o -, m - and p - BrTAB ) synthesized, the ortho-one is the only one which shows dual phosphorescence, with a short lifetime of 0.8 ms and a long lifetime of 234 ms in the crystalline state at room temperature. Based on theoretical calculations and crystal structure analysis of o - BrTAB , the short lifetime component is ascribed to the T₁^M state of the monomer which emits the higher energy phosphorescence. The long-lived, lower energy phosphorescence emission is attributed to the T₁^A state of an aggregate, with multiple intermolecular interactions existing in crystalline o - BrTAB inhibiting nonradiative decay and stabilizing the triplet states efficiently.     

Simple, general, and efficient synthesis of meso-substituted borondipyrromethenes from a single platform

An unprecedented synthesis of 8-substituted-borondipyrromethenes is described starting from 8-thiomethylbodipy 1. Aryl, heteroaryl, alkenyl, and organometallic boronic acids smoothly reacted with 1 in the presence of a catalytic amount of Pd(0) and a stoichiometric amount of Cu(I)-2-thienylcarboxylate under neutral conditions to give the corresponding Bodipy analogues in good to quantitative yields (20 examples). A remarkable reactivity was observed in some cases, e.g., ferrocenylboronic acid gave the product in 98% isolated yield after only 10 min at 55 degrees C.     

Silicone rod extraction of pharmaceuticals from water

Silicone elastomer (in the form of a flexible rod) is one of the materials currently tested for use in analytical extraction techniques and passive sampling devices. We investigated the applicability of this material for the enrichment of selected polar pharmaceuticals (antipyrine, carbamazepine, diclofenac, ibuprofen, bezafibrate) from water. Time-resolved batch extraction tests (up to five weeks in duration) were performed in stirred water samples ( approximately 0.5 L) with 2-cm-long silicone rod pieces. After re-extraction of trapped compounds with methanol, analysis was performed using liquid chromatography coupled with mass spectrometry. Distribution equilibrium was reached after a test duration of seven days. The silicone rod/water partition coefficients of the investigated pharmaceuticals range from 4 (antipyrine) to 1250 (diclofenac), and are related to the hydrophobicity of the compound. Enrichment of these pharmaceuticals in the silicone rod is lower than for other compound classes (chlorinated and polycyclic hydrocarbons).     

Lower branch coherent states in shear flows: transition and control

Lower branch coherent states in plane Couette flow have an asymptotic structure that consists of O(1) streaks, O(R(-1)) streamwise rolls and a weak sinusoidal wave that develops a critical layer, for large Reynolds number R. Higher harmonics become negligible. These unstable lower branch states appear to have a single unstable eigenvalue at all Reynolds numbers. These results suggest that lower branch coherent states control transition to turbulence and that they may be promising targets for new turbulence prevention strategies.     

Synergizing Electron and Heat Flows in Photocatalyst for Direct Conversion of Captured CO2

We report a ternary hybrid photocatalyst architecture with tailored interfaces that boost the utilization of solar energy for photochemical CO₂ reduction by synergizing electron and heat flows in the photocatalyst. The photocatalyst comprises cobalt phthalocyanine (CoPc) molecules assembled on multiwalled carbon nanotubes (CNTs) that are decorated with nearly monodispersed cadmium sulfide quantum dots (CdS QDs). The CdS QDs absorb visible light and generate electron-hole pairs. The CNTs rapidly transfer the photogenerated electrons from CdS to CoPc. The CoPc molecules then selectively reduce CO₂ to CO. The interfacial dynamics and catalytic behavior are clearly revealed by time-resolved and in situ vibrational spectroscopies. In addition to serving as electron highways, the black body property of the CNT component can create local photothermal heating to activate amine-captured CO₂, namely carbamates, for direct photochemical conversion without additional energy input.     

Homogenization of layered materials with rigid components in single-slip finite crystal plasticity

We determine the effective behavior of a class of composites in finite-strain crystal plasticity, based on a variational model for materials made of fine parallel layers of two types. While one component is completely rigid in the sense that it admits only local rotations, the other one is softer featuring a single active slip system with linear self-hardening. As a main result, we obtain explicit homogenization formulas by means of \(\Gamma \)-convergence. Due to the anisotropic nature of the problem, the findings depend critically on the orientation of the slip direction relative to the layers, leading to three qualitatively different regimes that involve macroscopic shearing and blocking effects. The technical difficulties in the proofs are rooted in the intrinsic rigidity of the model, which translates into a non-standard variational problem constraint by non-convex partial differential inclusions. The proof of the lower bound requires a careful analysis of the admissible microstructures and a new asymptotic rigidity result, whereas the construction of recovery sequences relies on nested laminates.