Analysis of a tripartite entanglement distribution switch

Queueing Systems - We study a quantum switch that distributes tripartite entangled states to sets of users. The entanglement switching process requires two steps: First, each user attempts to...     

Ion solvation by channel carbonyls characterized by 17O solid-state NMR at 21 T

Recently available ultrahigh magnetic fields offer new opportunities for studies of quadrupole nuclei in biological solids because of the dramatic enhancement in sensitivity and resolution associated with the reduction of second-order quadrupole interactions. Here, we present a new approach for understanding the function and energetics of ion solvation in channels using solid-state 17O NMR spectroscopy of single-site 17O-labeled gramicidin A. The chemical shift and quadrupole coupling parameters obtained in powder samples of lyophilized material are similar to those shown in the literature for carbonyl oxygens. In lipid bilayers, it is found that the carbonyl 17O anisotropic chemical shift of Leu10, one of the three carbonyl oxygens contributing to the ion binding site in gramicidin A, is altered by 40 ppm when K+ ion binds to the channel, demonstrating a high sensitivity to such interactions. Moreover, considering the large breadth of the carbonyl 17O chemical shift (>500 ppm), the recording of anisotropic 17O chemical shifts in bilayers aligned with respect to magnetic field B0 offers high-quality structural restraints similar to 15N and 13C anisotropic chemical shifts.     

Keggin ion mediated synthesis of hydrophobized Pd nanoparticles for multifunctional catalysis

Development of simple and reliable protocols for the synthesis of organically soluble catalytically active metal nanoparticles is an important aspect of research in nanomaterials. We demonstrate herein the formation of Pd nanoparticles by reduction of aqueous Pd(NO(3))(2) by photoexcited Keggin ions (phosphotungstate anions). This results in the formation of Pd nanoparticles capped with with Keggin ions that render the particles negatively charged. The Keggin ion capped Pd nanoparticles may then be phase transferred into nonpolar organic solvents such as toluene by electrostatic complexation with cationic surfactants such as octadecylamine at the liquid-liquid interface. This results in a new class of catalyst wherein both the Pd core and Keggin ion shell may be used in a range of catalytic reactions leading to a truly multifunctional catalyst dispersible in organic solvents.     

NMR Reveals That a Highly Reactive Nonheme FeIV=O Complex Retains Its Six-Coordinate Geometry and S=1 State in Solution

The [Fe^IV(O)(Me₃NTB)]²⁺ (Me₃NTB=tris[(1-methyl-benzimidazol-2-yl)methyl]amine) complex 1 has been shown by Mössbauer spectroscopy to have an S=1 ground state at 4 K, but is proposed to become an S=2 trigonal-bipyramidal species at higher temperatures based on a DFT model to rationalize its very high C−H bond-cleavage reactivity. In this work, ¹H NMR spectroscopy was used to determine that 1 does not have C₃-symmetry in solution and is not an S=2 species. Our results show that 1 is unique among nonheme Fe^IV=O complexes in retaining its S=1 spin state and high reactivity at 193 K, providing evidence that S=1 Fe^IV=O complexes can be as reactive as their S=2 counterparts. This result emphasizes the need to identify factors besides the ground spin state of the Fe^IV=O center to rationalize nonheme oxoiron(IV) reactivity.     

“Dial-In” Emission from a Unique Flexible Material with Polarization Tuneable Spectral Intensity

The development of organic photoluminescent materials, which show promising roles as catalysts, sensors, organic light-emitting diodes, logic gates, etc., is a major demand and challenge for the global scientific community. In this context, a photoclick polymerization method is adopted for the growth of a unique photoluminescent three-dimensional (3D) polymer film, E, as a model system that shows emission tunability over the range 350–650 nm against the excitation range 295–425 nm. The DFT analysis of energy calculations and π-stacking supports the spectroscopic observations for the material exhibiting a broad range of emission owing to newly formed chromophoric units within the film. Full polarization spectroscopic Mueller matrix studies were employed to extract and quantify the molecular orientational order of both the ground (excitation) and excited (emission) state anisotropies through a set of newly defined parameters, namely the fluorescence diattenuation and fluorescence polarizance. The information contained in the recorded fluorescence Mueller matrix of the organic polymer material provided a useful way to control the spectral intensity of emission by using pre- and post-selection of polarization states. The observation was based on the assumption that the longer lifetime of the excited dipolar orientation is attributed to the compactness of the film.     

SDS/Ac2O/H2O: Surfactant‐Mediated Cleavage of Imines with Acetic Anhydride to Carbonyls and Acetanilides in Water

Surfactant (SDS)‐mediated cleavage of imines was achieved with acetic anhydride to the corresponding carbonyls (aldehydes and ketones) and acetanilides in water at 25–30°C with very good to excellent yields, thus contributing significantly to the green chemistry concept.     

Lipase mediated separation of triterpene structural isomers, α- and β-amyrin

Pentacyclic triterpenoids α- and β-amyrin possess a wide range of biological and pharmacological activities. High structural similarity between these two structural isomers makes their chromatographic separation an ineffective and tedious choice. In this study, Candida rugosa lipase catalyzed separation protocol for the isolation of individual isomers has been developed. In the presence of vinyl acetate as the acyl donor, Candida rugosa lipase carried out acetylation of β-amyrin more efficiently as compared to α-amyrin leading to a kinetic separation. The conditions of transesterification reaction were optimized systematically, which was utilized to separate α- and β-amyrin from a mixture obtained from the latex of Plumeria obtusa.     

Nickel(II)-Mediated Reversible Thiolate/Disulfide Conversion as a Mimic for a Key Step of the Catalytic Cycle of Methyl-Coenzyme M Reductase

According to the well-accepted mechanism, methyl-coenzyme M reductase (MCR) involves Ni-mediated thiolate-to-disulfide conversion that sustains its catalytic cycle of methane formation in the energy saving pathways of methanotrophic microbes. Model complexes that illustrate Ni-ion mediated reversible thiolate/disulfide transformation are unknown. In this paper we report the synthesis, crystal structure, spectroscopic properties and redox interconversions of a set of Ni^II complexes comprising a tridentate N₂S donor thiol and its analogous N₄S₂ donor disulfide ligands. These complexes demonstrate reversible Ni^II-thiolate/Ni^II-disulfide (both bound and unbound disulfide-S to Ni^II) transformations via thiyl and disulfide monoradical anions that resemble a primary step of MCR's catalytic cycle.     

Recent advances of lead-free metal halide perovskite single crystals and nanocrystals: synthesis,crystal structure,optical properties,and their diverse applications

Lead halide hybrid perovskites have received massive research attention because of their unique inherent photophysical properties that driven them for potential application in the fields of photovoltaics, light-emitting devices, lasing, X-ray detector, and so on. Perovskite single crystals and nanocrystals are generally synthesized via various low-cost solution-processed techniques. The emergence of simple growth approaches of perovskite structures enable to fabricate low-cost and highly efficient devices. However, toxicity of Pb atoms and instability of perovskite structures obstruct further commercialization of these technologies. Recent efforts have been shifted to discover novel, eco-friendly, and stable lead-free metal halide perovskite (LFHP) materials and exploring their different growth processes for various device applications. This review aims to provide an up-to-date analysis of recent progress report on LFHPs and will mainly focus on their growth processes in the single crystalline and nanocrystalline forms. This review also tries to understand how the perovskite crystal structure impacts on their fundamental properties. In addition, we discuss the current progress in various field of applications and their future aspects.     

A vicarious one-pot transformation of a fluorocyclitol to a polycyclitol: observation of a formal 4-fold axial-equatorial epimerization on a conformationally locked scaffold

A conformationally locked fluoropentol undergoes an interesting transformation to (trans,anti,trans,anti,trans)-perhydro-2,3,4a,6,7,8a-naphthalenehexol essentially under conditions of base-induced transesterification. The proposed rationale for the observed metamorphosis involves a nucleophilic displacement of fluoride, and subsequent stereo- and regioselective anti-Fürst-Plattner-type ring-opening of the epoxide thus formed.