Zinc Oxide–Porphyrin Hybrid Rhombuses: Catalytically Active Microstructures via Self‐Assembly

A novel self‐assembled organic–inorganic hybrid structure consisting of zinc oxide and two oppositely charged porphyrins, showing significantly enhanced photocatalytic activity, is presented. Electrostatic self‐assembly of the cationic tetra‐(N‐methyl‐4‐pyridyl)porphyrin (TMPyP) with preformed assemblies of ZnO nanorods and the anionic tetra‐(4‐sulfonatophenyl)porphyrin (TPPS) in ethanol results in porphyrin microrhombuses decorated with ZnO nanorods. The structure formation is followed spectroscopically. The shape of the microrhombuses and the number of attached ZnO nanoparticles can be tuned through the porphyrin ratio TMPyP/TPPS. An enhanced and selective catalytic activity is found, giving insight into the degradation mechanism. Due to the tool‐box principle and its versatility, the concept may have great impact in fields such as solar‐energy conversion and optoelectronics.     

Backward iteration in strongly convex domains

We prove that a backward orbit with bounded Kobayashi step for a hyperbolic, parabolic or strongly elliptic holomorphic self-map of a bounded strongly convex C² domain in Cd necessarily converges to a repelling or parabolic boundary fixed point, generalizing previous results obtained by Poggi-Corradini in the unit disk and by Ostapyuk in the unit ball of Cd.     

Kinetic study of specific base catalyzed hydrolysis of ethyl acrylate in water-ethanol binary system

Kinetic study of hydroxide anion catalyzed hydrolysis of ethyl acrylate has been carried in ethanol-water (10–50% v/v) binary systems at the temperature range 30 ± 0.1, 35 ± 0.1, 40 ± 0.1, and 45 ± 0.1°C. Calculated specific rate constant values decreases with increasing proportion of ethanol at all temperatures. The observed retardation of a base catalyzed hydrolysis reaction is explained on the basis of fact that the formation of polarized transition state is disfavored with increase in % of ethanol. The relation between the change in dielectric constant due to variation in binary mixtures and change in specific rate constant are explained on the basis of electrostatic and non electrostatic contributions of solvent mixtures. The variation of ΔG*, ΔH*, ΔS* with solvent composition and the specific effect of water on the reaction rate kinetics are also discussed.     

Synthesis of 2t-Substituted-1r,3c-BIS(2′-Hydroxy-5-Substituted-Benzyl)-Imidazolidines by Reaction of 1,3-BIS(2′-Hydroxy-5′-Substituted-Benzyl)-Imidazolidines with Aromatic Aldehydes

A one-step synthesis of 2t-substituted-1r,3c-bis(2′-hydroxy-5′- substituted-benzyl)-imidazolidines from 1,3-bis(2′-hydroxy-5′-substituted-benzyl)-imidazolidines and aromatic aldehydes is reported. The relative stereochemistry of the five-membered ring was evident from ¹H NMR measurements combined with MMX calculations.     

Biocatalytic organic synthesis of optically pure (S)-scoulerine and berbine and benzylisoquinoline alkaloids

A chemoenzymatic approach for the asymmetric total synthesis of the title compounds is described that employs an enantioselective oxidative C-C bond formation catalyzed by berberine bridge enzyme (BBE) in the asymmetric key step. This unique reaction yielded enantiomerically pure (R)-benzylisoquinoline derivatives and (S)-berbines such as the natural product (S)-scoulerine, a sedative and muscle relaxing agent. The racemic substrates rac-1 required for the biotransformation were prepared in 4-8 linear steps using either a Bischler-Napieralski cyclization or a C1-Cα alkylation approach. The chemoenzymatic synthesis was applied to the preparation of fourteen enantiomerically pure alkaloids, including the natural products (S)-scoulerine and (R)-reticuline, and gave overall yields of up to 20% over 5-9 linear steps.     

Spectrofluorimetric Method for Determination and Validation of Cefixime in Pharmaceutical Preparations Through Derivatization with 2-Cyanoacetamide

A simple, sensitive and accurate method has been developed for spectrofluorimetric determination of cefixime in pure form and pharmaceutical preparations. The method is based on the reaction of cefixime with 2-cyanoacetamide in the presence of 21% ammonia at 100 °C. The fluorescent reaction product showed maximum fluorescence intensity at λ 378 nm after excitation at λ 330 nm. The factors affecting the derivatization reaction were carefully studied and optimized. The fluorescence intensity versus concentration plot was rectilinear over the range of 0.02 to 4 μg mL⁻¹ with correlation coefficient of 0.99036. The limit of detection (LOD) and limit of quantification (LOQ) was found to be 2.95 ng mL⁻¹ and 9.84 ng mL⁻¹, respectively. The proposed method was validated statistically and through recovery studies. The method was successfully applied for the determination of cefixime in pure and dosage form with percent recoveries from 98.117% to 100.38%. The results obtained from the proposed method have been compared with the official HPLC method and good agreement was found between them.     

Spectrofluorimetric Protocol for Ceftriaxone in Commercial Formulation and Human Plasma After Condensation with Formaldehyde and Ethyl Acetoacetate

A new spectrofluorimetric method has been developed and validated for the quantification of ceftriaxone in bulk powder, pharmaceutical formulations and spiked human plasma. The developed method is reproducible, accurate, sensitive and cost effective. In this method, ceftriaxone was converted into a fluorescent compound by reacting with 0.8 M ethyl acetoacetate and 25% formaldehyde in a buffered medium (pH = 4.2) at 90 °C. The excitation and emission wavelengths of the fluorescent reaction product are 316 nm and 388 nm respectively. Optimization of the experimental conditions affecting the condensation reaction were carefully carried out and the optimum experimental conditions were incorporated in the procedure. The developed method has a broad linear range (0.2–20 μg mL⁻¹) with a correlation coefficient of 0.9992. The limit of detection (LOD) and limit of quantification (LOQ) was found to be 1.94 × 10⁻² μg mL⁻¹ and 6.47 × 10⁻² μg mL⁻¹ respectively. The common excipients and co-administered drugs were investigated for their interferences effect in the assay. The developed method was validated statistically through recovery studies and successfully applied to ceftriaxone determination in bulk powder, pharmaceutical formulations and spiked human plasma samples. The percent recoveries were found to be in the range of 99.04–100.26% for bulk powder, 98.88–99.92% for pharmaceutical formulations and 94.22–98.48% for spiked human plasma. The results were verified by comparing with reference literature HPLC method and were found in good agreement.     

Lithium-ion Mobility in Li6B18(Li3N) and Li Vacancy Tuning in the Solid Solution Li6B18(Li3N)1−x(Li2O)x

All-solid-state batteries are promising candidates for safe energy-storage systems due to non-flammable solid electrolytes and the possibility to use metallic lithium as an anode. Thus, there is a challenge to design new solid electrolytes and to understand the principles of ion conduction on an atomic scale. We report on a new concept for compounds with high lithium ion mobility based on a rigid open-framework boron structure. The host–guest structure Li₆B₁₈(Li₃N) comprises large hexagonal pores filled with Li₇N] strands that represent a perfect cutout from the structure of α-Li₃N. Variable-temperature ⁷Li NMR spectroscopy reveals a very high Li mobility in the template phase with a remarkably low activation energy below 19 kJ mol⁻¹ and thus much lower than pristine Li₃N. The formation of the solid solution of Li₆B₁₈(Li₃N) and Li₆B₁₈(Li₂O) over the complete compositional range allows the tuning of lithium defects in the template structure that is not possible for pristine Li₃N and Li₂O.