Category Archives: Chemistry – An Asian Journal:

Operando imaging in electrocatalysis: insights into microstructural materials design

Posted on by
Operando imaging in electrocatalysis: insights into microstructural materials design

This review aims to highlight significant advancements in the application of operando imaging techniques to enhance the understanding of heterogeneous electrocatalytic reactions. We summarize the most recent mechanistic insights achieved through a range of operando imaging techniques, including electron microscopies, X-ray imaging, scanning probe microscopies, and various optical microscopies. Additionally, we put forward insights into emerging directions and prospects within this field.


Abstract

Electrocatalysis plays a pivotal role in renewable energy conversion and associated chemical production, enabling a variety of emerging sustainability technologies with societal impacts. Achieving marked improvement in electrocatalytic performance relies on a deep understanding of catalyst microstructures and catalytic mechanisms, with a particular emphasis on the detailed, spatiotemporally resolved characterizations of the underlying fundamental electrocatalytic processes. This fundamental need drives the development of operando imaging techniques, which improve the ability to detect dynamic structural changes in electrocatalysts and establish clear structure-performance relationships for morphologically complex, hierarchically structured catalytic materials. This review aims to highlight significant advancements in the application of operando imaging techniques to develop a deeper understanding of important heterogeneous electrocatalytic reactions critical for emerging sustainability technologies. We summarize the up-to-date key mechanistic insights regarding these reactions achieved through a range of operando imaging techniques, including electron microscopies, X-ray imaging techniques, scanning probe microscopies, and optical microscopies. We conclude by pointing out emerging directions and future prospects within the field of operando imaging in electrocatalysis.

Role of Halobenzene Guest Molecules in Modulating Room Temperature Phosphorescence of Benzophenone–Naphthalene Diimide Inclusion Crystals

Posted on by
Role of Halobenzene Guest Molecules in Modulating Room Temperature Phosphorescence of Benzophenone–Naphthalene Diimide Inclusion Crystals

In this study, inclusion crystals composed of a benzophenone-naphthalenediimide host (1) and halobenzene guests were developed, unveiling unique fluorescence and room temperature phosphorescence (RTP) properties. A 1 : 1 host-guest composition in these crystals was confirmed, and the effects of various guests, such as chlorobenzene, bromobenzene, and iodobenzene, on their luminescence were observed. Additionally, the influences of external heavy atom effects on the RTP properties of these crystals were discussed.


Abstract

Materials exhibiting room temperature phosphorescence (RTP) have recently emerged as a subject of significant interest. In this study, we successfully created inclusion crystals by introducing halobenzenes as guests into a host molecule combining benzophenone with naphthalene diimide. This approach led to the creation of fascinating fluorescence and RTP properties dependent on the guest molecules. Notably, crystals containing chlorobenzene showed cyan fluorescence, while those with iodobenzene displayed red RTP. This difference highlights the impact of the guest molecule on the luminescent properties, with the significant external heavy-atom effect of iodobenzene playing a key role in promoting efficient intersystem crossing between the excited singlet and triplet states. Crystals with bromobenzene exhibited a unique blend of fluorescence and RTP, both from benzophenone and naphthalene diimide, highlighting the moderate heavy-atom effect. These findings reveal composite materials with remarkably diverse and interesting optical characteristics.

Directionality of Halogen‐Bonds: Insights from 2D Energy Decomposition Analysis

Posted on by
Directionality of Halogen-Bonds: Insights from 2D Energy Decomposition Analysis

From Bigger to Smaller: Unraveling the influence of size and Pauli repulsion on halogen bond directionality. The potential energy landscape is shaped by anisotropic electron density through Pauli repulsion in larger halogens, whereas the influence of electrostatic forces on bond orientation becomes more pronounced in smaller halogens.


Abstract

Halogen bonds are typically observed to have a linear arrangement with a 180° angle between the nucleophile and the halogen bond acceptor X−R. This linearity is commonly explained using the σ-hole model, although there have been alternative explanations involving exchange repulsion forces. We employ two-dimensional Distortion/Interaction and Energy Decomposition Analysis to examine the archetypal H3N⋯X2 halogen bond systems. Our results indicate that although halogen bonds are predominantly electrostatic, their directionality is largely due to decreased Pauli repulsion in linear configurations as opposed to angled ones in the I2 and Br2 systems. As we move to the smaller halogens, Cl2 and F2, the influence of Pauli repulsion diminishes, and the energy surface is shaped by orbital interactions and electrostatic forces. These results support the role of exchange repulsion forces in influencing the directionality of strong halogen bonds. Additionally, we demonstrate that the 2D Energy Decomposition Analysis is a useful tool for enhancing our understanding of the nature of potential energy surfaces in noncovalent interactions.

Total Synthesis of (±)‐20‐epi‐Kopsiyunnanine K: A Domino and Stereocontrolled Approach

Posted on by
Total Synthesis of (±)-20-epi-Kopsiyunnanine K: A Domino and Stereocontrolled Approach

A domino double cyclization of N-benzyltryptyl-4-pentenamide has been developed for rapid assembly of a novel azepane-fused tetrahydro-β-carboline framework. With a serendipitous stereocontrolled alkylation, the total synthesis of (±)-20-epi-Kopsiyunnanine K have been successfully accomplished.


Abstract

A one-pot route to a novel azepane-fused tetrahydro-β-carboline framework from tryptyl-4-pentenamide derivatives has been developed, featuring the Rh-catalyzed hydroformylation double cyclization. Subsequent alkylation in the tetracyclic system proceeded stereoselectively to form a quaternary carbon. The synthesis of (±)-20-epi-kopsiyunnanine K was accomplished through the strategy.

Bi‐ and tridentate coordination behaviour of a novel bis(phosphinimino)methanide ligand

Posted on by
Bi- and tridentate coordination behaviour of a novel bis(phosphinimino)methanide ligand

Time for new functional groups: A new ferrocenyl-functionalized bis(phosphinimino)methane ligand with redox-active properties was synthesized and introduced into tetrylene chemistry, leading to unprecedented coordination behaviour.


Abstract

Herein, we report the synthesis of a novel ferrocenyl-functionalized bis(phosphinimino)methane ligand (CH2(PPh2NFc)2). Deprotonation of CH2(PPh2NFc)2 with KN(SiMe3)2 gave the dimeric species [K{CH(PPh2NFc)2}]2, which was further reacted with ECl2 (E=Ge, Sn) to yield the tetrylene compounds [{CH(PPh2NFc)2}ECl]. The ligand and the resulting tetrylenes were examined for their electrochemical properties with the aid of cyclic voltammetry. Furthermore, the reaction of the tetrylenes [{CH(PPh2NFc)2}ECl] with [AuC6F5(tht)] resulted in the bimetallic complexes [{(AuC6F5)CH(PPh2NFc)2}ECl] with an unusual Au coordination on the ligand backbone.

Rapid and Practical Synthesis of gem‐Dibromoalkanes from Aldehydes by Tribromide Reagent

Posted on by
Rapid and Practical Synthesis of gem-Dibromoalkanes from Aldehydes by Tribromide Reagent

A rapid and practical synthesis of gem-dibromoalkanes has been developed. A variety of alkyl and aromatic aldehydes are converted into their corresponding gem-dibromoalkanes within 10 minutes by using tribromide reagent. The protocol is also appliable to the bromination of alcohols, accessing alkyl bromides with inversion of configuration.


Abstract

gem-Dibromoalkanes are important synthetic building block in organic chemistry, but their preparation is still troublesome. Herein, we have developed a simple and practical protocol for the synthesis of gem-dibromoalkanes from aldehydes using tetrabutylammonium tribromide and triphenyl phosphite. A variety of alkyl and aromatic aldehydes can be transformed into the corresponding products within 10 minutes. This protocol is also applicable to alcohols, and the configuration of chiral alcohol is inverted during the process with excellent enantiopurity.

Water vs. Organic Solvents: Water‐Controlled Divergent Reactivity of 2‐Substituted Indoles

Posted on by
Water vs. Organic Solvents: Water-Controlled Divergent Reactivity of 2-Substituted Indoles

Selective oxime formation of 2-substituted indoles and malonates has been developed. Notwithstanding lack of ability to dissolve reactants, water exhibited superior performance to other media. 2-Methoxyethyl nitrite, which has been tailored for reactions in water, empowered this protocol. Chemoselective transformations of the products opens up access to a new chemical library. These results support the power of running organic reactions in water.


Abstract

Water is not a good solvent for most organic compounds, yet water can offer many benefits to some organic reactions, hence enriching organic chemistry. Herein, the unique divergent reactivity of 2-substituted indoles with ⋅NO sources is presented. The amount of water solvent was harnessed for a scalable, benign, and expedient synthesis of indolenine oximes, albeit with water's inability to dissolve the reactants. 2-Methoxyethyl nitrite, which has been tailored for reactions in water, empowered this protocol by enhancing the product selectivity. We further report on chemoselective transformations of the products that rely on their structural features. Our findings are expected to offer access to an underexplored chemical space. The platform is also applicable to oximinomalonate synthesis. Mechanistic studies revealed the important role of water in the reversal of stability between oxime and nitroso compounds, promoting the proton transfer.

Ligand‐ and metal‐exchange reactions of robust nickel complexes with pentagonal bipyramidal structures

Posted on by
Ligand- and metal-exchange reactions of robust nickel complexes with pentagonal bipyramidal structures

Nickel complexes with rare pentagonal bipyramidal structures were synthesized via ligand-exchange reactions. The complexes were water- and acid-resistant. With the aid of theoretical calculations, the crystal structures showed that the pentagonal bipyramidal structures comprised electrostatic rings of cyclic pentapyridyls and threaded linear metal complexes.


Abstract

The coordination chemistries of transition metal complexes with pentagonal bipyramidal geometries were investigated, and the highly stable nature of a cyclic pentapyridyl ligand was disclosed. A NiCl2 complex with the pentapyridyl ligand was found to be stable toward water and acidic conditions. The stable complex underwent ligand-exchange reactions with nucleophilic reagents, and a series of pentagonal bipyramidal complexes with different apical ligands was prepared. Crystallographic analyses with the aid of theoretical calculations revealed that the complexes were constructed by electrostatic threading of a divalent linear nickel complex into the ring of the neutral, cyclic pentapyridyl, which resulted in robust water- and acid-resistant complexes with unique pentagonal bipyramidal structures. A reductive metal exchange reaction was then discovered, which enabled “linear divalent metal + electrostatic ring” formulations with different metal atoms.

HSA over BSA: Selective detection of Human Serum Albumin via a naphtho [2,1‐b] furan‐based system

Posted on by
HSA over BSA: Selective detection of Human Serum Albumin via a naphtho [2,1-b] furan-based system

Development of a naphtho[2,1-b] furan probe for fluorescence-assisted micromolar detection of Human Serum Albumin (HSA). The probe displays exclusive selectivity towards HSA compared to its congeners from other mammalian/non-mammalian sources. Its unique behavior is analyzed using anisotropy and time-resolved studies. The practical application of the probe is demonstrated in HSA-spiked human urine samples.


Abstract

Human serum albumin (HSA) is an important biomarker that can be used for the early diagnosis of many diseases. In this work, a TICT probe bearing fused naphtho-furan scaffold (NPNF) was developed and employed in the selective turn-on sensing of HSA. The probe's selectivity towards HSA was observed using steady-state fluorescence experiments, with limit of quantitation in micromolar levels. NPNF's capability to exclusively detect HSA over BSA was further studied/rationalized using anisotropy and time-resolved studies. Molecular docking was used to shed light on the location of NPNF in the subdomain IB of HSA. The practical application of the probe was also demonstrated by the detection of HSA in urine and the HSA-assisted detection of cerium.

Cascade Synthesis of New Indole‐Containing Pentacyclic Scaffolds Mediated by Aryl and Iminyl Radicals

Posted on by
Cascade Synthesis of New Indole-Containing Pentacyclic Scaffolds Mediated by Aryl and Iminyl Radicals

A five-step approach was developed for the synthesis of a series of substituted indole-pyrido-indene pentacyclic compounds. Reaction proceeded via domino radical-mediated processes in the presence of the radical reagents LDA/TTMSS and AIBN/TTMSS.


Abstract

A five-step approach, starting from simple 1,5-disubstituted indoles, has been implemented for the synthesis of diversely substituted indole-pyrido-indene pentacyclic compounds up to 54 % yield via domino radical-mediated processes in the presence of the radical reagents DLP/TTMSS and AIBN/TTMSS. Reactions proceeded with diverse key starting radical cyano-precursors strategically synthesized which were subsequently transformed into the target pentacyclic compounds through an aryl/iminyl radical-mediated domino reactions sequence. In addition to the routine spectroscopic techniques, the structure of radical precursors, as well as, the target pentacyclic products were unequivocally established by single crystal X-ray diffraction, confirming the effectiveness of the proposed synthetic sequence.