Unraveling Reactivity Pathways: Dihydrogen Activation and Hydrogenation of Multiple Bonds by Pyramidalized Boron‐Based Frustrated Lewis Pairs

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Unraveling Reactivity Pathways: Dihydrogen Activation and Hydrogenation of Multiple Bonds by Pyramidalized Boron-Based Frustrated Lewis Pairs

A DFT-based study explores the H2 activation by pyramidalized boron-based B/E-FLP (E=N, P, As, Sb and Bi, etc.) systems. The study also highlights the hydrogenation process of multiple bonds with the help of B/N-FLP.


Abstract

The activation of H2 by pyramidalized boron-based frustrated Lewis Pairs (FLPs) (B/E-FLP systems where “E” refers to N, P, As, Sb, and Bi) have been explored using density functional theory (DFT) based computational study. The activation pathway for the entire process is accurately characterized through the utilization of the activation strain model (ASM) of reactivity, shedding light on the underlying physical factors governing the process. The study also explores the hydrogenation process of multiple bonds with the help of B/N-FLP. The research findings demonstrate that the liberation of activated dihydrogen occurs in a synchronized, albeit noticeably asynchronous, fashion. The transformation is extensively elucidated using the activation strain model and the energy decomposition analysis. This approach suggests a co-operative double hydrogen-transfer mechanism, where the B−H hydride triggers a nucleophilic attack on the carbon atom of the multiple bonds, succeeded by the migration of the protic N−H.

Enhanced Photocatalytic H2 Generation by Light‐Induced Carbon Modification of TiO2 Nanotubes

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Enhanced Photocatalytic H2 Generation by Light-Induced Carbon Modification of TiO2 Nanotubes

A closer examination of the role and impact of carbon within TiO2 nanotubes on H2 evolution and photoelectrochemical performance was carried out. Carbon is inherently present in nanotubes as remnant organic electrolyte used in the anodization processes. This residue serves as a carbon source during annealing in air, and when exposed to UV light, the carbon undergoes modification, thus resulting in enhanced photocatalytic efficiency.


Abstract

Titanium dioxide (TiO2) is the material of choice for photocatalytic and electrochemical applications owing to its outstanding physicochemical properties. However, its wide bandgap and relatively low conductivity limit its practical application. Modifying TiO2 with carbon species is a promising route to overcome these intrinsic complexities. In this work, we propose a facile method to modify TiO2 nanotubes (NTs) based on the remnant organic electrolyte retained inside the nanotubes after the anodization process, that is, without removing it by immersion in ethanol. Carbon-modified TiO2 NTs (C-TiO2 NTs) showed enhanced H2 evolution in photocatalysis under UV illumination in aqueous solutions. When the C-TiO2 NTs were subjected to UV light illumination, the carbon underwent modification, resulting in higher measured photocurrents in the tube layers. After UV illumination, the IPCE of the C-TiO2 NTs was 4.4-fold higher than that of the carbon-free TiO2 NTs.

In situ Investigations of the Formation Mechanism of Metastable γ‐BiPd Nanoparticles in Polyol Reductions

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In situ Investigations of the Formation Mechanism of Metastable γ-BiPd Nanoparticles in Polyol Reductions

The formation of γ-BiPd in a polyol process has been monitored by X-ray powder diffraction, light scattering, and in situ measurements of redox potential and pH value. Palladium nanoparticles are formed as primary reaction product followed by a successive reduction of bismuth cations and a diffusion-controlled formation of the intermetallic target phase.


Abstract

Synthesizing intermetallic phases containing noble metals often poses a challenge as the melting points of noble metals often exceed the boiling point of bismuth (1560 °C). Reactions in the solid state generally circumvent this issue but are extremely time consuming. A convenient method to overcome these obstacles is the co-reduction of metal salts in polyols, which can be performed within hours at moderate temperatures and even allows access to metastable phases. However, little attention has been paid to the formation mechanisms of intermetallic particles in polyol reductions. Identifying crucial reaction parameters and finding patterns are key factors to enable targeted syntheses and product design. Here, we chose metastable γ-BiPd as an example to investigate the formation mechanism from mixtures of metal salts in ethylene glycol and to determine critical factors for phase formation. The reaction was also monitored by in situ X-ray diffraction using synchrotron radiation. Products, intermediates and solutions were characterized by (in situ) X-ray diffraction, electron microscopy, and UV-Vis spectroscopy. In the first step of the reaction, elemental palladium precipitates. Increasing temperature induces the reduction of bismuth cations and the subsequent rapid incorporation of bismuth into the palladium cores, yielding the γ-BiPd phase.

Secondary 3‐Chloropiperidines: Powerful Alkylating Agents

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Secondary 3-Chloropiperidines: Powerful Alkylating Agents

The synthesis of secondary 3-chloropiperidines and highly strained bicyclic aziridines is reported, including a new method for the selective mono-chlorination of unsaturated primary amines. The novel compounds, which closely resemble natural alkylating agents, proved to be more active than previously reported 3-chloropiperidines in a DNA cleavage assay, highlighting their potential as powerful alkylating agents.


Abstract

In previous works, we demonstrated that tertiary 3-chloropiperidines are potent chemotherapeutics, alkylating the DNA through the formation of bicyclic aziridinium ions. Herein, we report the synthesis of novel secondary 3-chloropiperidine analogues. The synthesis incorporates a new procedure to monochlorinate unsaturated primary amines utilizing N-chlorosuccinimide, while carefully monitoring the temperature to prevent dichlorination. Furthermore, we successfully isolated highly strained bicyclic aziridines by treating the secondary 3-chloropiperidines with a sufficient amount of base. We conclude this work with a DNA cleavage assay as a proof of principle, comparing our previously known substrates to the novel compounds. In this, the secondary 3-chloropiperidine as well as the isolated bicyclic aziridine, proved to be more effective than their tertiary counterpart.

Hydrogen Production via Methane Decomposition over Alumina Doped with Titanium Oxide‐Supported Iron Catalyst for Various Calcination Temperatures

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Hydrogen Production via Methane Decomposition over Alumina Doped with Titanium Oxide-Supported Iron Catalyst for Various Calcination Temperatures

Iron metal was used for hydrogen production via methane decomposition using alumina as support; furthermore, to overcome the drawback of alumina, titanium dioxide was added at 20 %, considering various calcination temperatures. The results show that adding 20 % of TiO2 to alumina enhances the activity of catalysts for hydrogen production and stability. Carbon was produced as carbon nanotubes (CNT).


Abstract

The decomposition of methane has been chosen as an alternative method for producing hydrogen. In this study, 20 % Fe was used as the active metal part of the catalyst. To better comprehend the impact of the supporting catalytic properties, alumina and titania-alumina composite were investigated as supports. Iron-based catalysts were prepared by impregnation method and then calcined at different temperatures (300 °C, 500 °C, and 800 °C). The catalysts were examined at 800 °C under atmospheric pressure with a 15 mL/min total flow rate and 2 : 1 CH4 to N2 feed ratio. The textural and morphological characteristics of the fresh calcined and spent catalysts were investigated. The catalytic activity and stability data demonstrated that Fe supported over TiO2-Al2O3 calcined at 500 °C performed the best of all evaluated catalysts with a more than 80 % hydrogen yield. The Raman spectra result showed that graphitic carbon was produced for all used titanium dioxide catalysts. Moreover, according to transmission electron microscopy (TEM) results, the carbon deposited on the catalysts’ surface is carbon nanotubes (CNT).

Fabricating Quasiperiodic Tilings with Thermal‐Scanning Probe Lithography

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Fabricating Quasiperiodic Tilings with Thermal-Scanning Probe Lithography


Abstract

We outline an approach to fabricate nanoscale artificial quasiperiodic tilings with thermal-scanning probe lithography. Quasiperiodic tilings such as the Ammann-Beenker, Square Fibonacci tiling, and Penrose are fabricated and imaged with thermal-conductance feedback microscopy, followed by electron microscopy. The design implementation, chemical, and physical challenges involved in fabricating such artificial systems using nanolithography are discussed. Additionally, the potential applications of fabricated quasiperiodic tilings are explored.