Category Archives: Chemistry – An Asian Journal:

Beyond Molecular Recognition: A Perylene Bisimide Derivative as a Functional Mimic of Chlorpyrifos

Posted on 4 October 2023 by

Supramolecular assemblies of PBI-SAH have been developed which could detect chlorpyrifos in the nanomolar range and could also mimic AChE inhibitory activity of CPF to show promising aptitude as ‘safe insecticide’.

Abstract

Supramolecular assemblies of perylene bisimide derivative (PBI-SAH) have been developed which show ‘turn-on’ detection of chlorpyrifos in aqueous media, apple residue and blood serum. Differently from the already reported fluorescent probes for the detection of CPF, PBI-SAH assemblies also show affinity for acetylcholinesterase (AChE) which endow the PBI-SAH molecules with mixed inhibitory potential to restrict the AChE catalysed hydrolysis of acetylthiocholine (ATCh) in MG-63 cell lines (in vitro) and in mice (in vivo). The molecular docking studies support the inhibitory activity of PBI-SAH assemblies and their potential to act as safe insecticide with high benefit to harm ratio. The insecticidal potential of PBI-SAH derivative has been examined against Spodoptera litura (S. litura) and these studies demonstrate its excellent insecticidal activity (100 % mortality in nineteen days). To the best of our knowledge, this is the first report regarding development of PBI-SAH assemblies which not only detect chlorpyrifos but also mimic AChE inhibitory activity of CPF to show promising aptitude as safe insecticide.

A PSCLC Pattern Prepared Based on Handedness Inversion for Anti‐counterfeiting

Posted on 4 October 2023 by nJinghua Zhao, nRunwei Yu, nLimin Wu, nYi Li, nWei Liu, nYonggang Yangn

Photochromic cholesteric liquid crystals (CLCs) were prepared, which could be applied for the preparation of colourful polymer-stabilized CLC (PSCLC) patterns. Based on handedness inversion, the obtained PSCLC patterns were suitably applied for anti-counterfeiting.

Abstract

Handedness inversion has been widely studied in supramolecular chemistry and material sciences. Herein, a photoisomerizable chiral dopant was synthesized, which could induce the formation of a cholesteric phase with right-handedness. The Bragg reflection band of the cholesteric liquid crystal (CLC) mixture shifted to the long wavelength with extending 365 nm UV light irradiation time. Based on this photochromic property, a colourful polymer-stabilized CLC (PSCLC) film was prepared using a grayscale mask. A handedness reversible CLC mixture was prepared using a mixture of this chiral dopant and S5011. With extending the UV light irradiation time, the handedness of the CLC mixture changed from right- to left-handedness. A patterned PSCLC film was prepared using this CLC mixture. Complementary images were observed under right- and left-handedness circularly polarized lights. The results shown here not only give us a better understanding the competition between photopolymerization and photoisomerization, but also lay the foundations for decoration and anti-counterfeiting.

Design and Synthesis of Artificial Nucleobases for Sequence‐Selective DNA Recognition within the Major Groove

Posted on 4 October 2023 by

Four new rigid heterocyclic binders for each canonic base pair have been designed and synthesized. In silico, their PNA adduct allows oligomerization into PNA strands with perfect complementarity to dsDNA, without any sequence restriction.

Abstract

We present the design and synthesis of artificial specific nucleobases, each one recognizing a single base pair within the major groove of duplex DNA. Computational calculations indicate that PNAs modified with these nucleobases enable the formation of highly stable triple helices with no sequence restrictions through multiple hydrogen bonding and π⋅⋅⋅π stacking interactions, without significantly widening the DNA double helix. New synthetic routes were developed to the structures of these fused heterocycles which have rarely been described in the literature. NMR titration experiments indicate specific hydrogen bonding at the Hoogsteen sites. The new building blocks allow the construction of four PNA monomers for each canonic base pair and their covalent connection to PNA oligomers. These can be designed complementary to any given DNA sequence. With high efficiency and relative simplicity of operation, the described methodologies and strategies hence form the basis for a new supramolecular ligand system targeting double-stranded DNA without strand invasion.

Temperature‐Responsive Pickering Double Emulsions Stabilized by Binary Microgels

Posted on 4 October 2023 by nXin Guan, nYunxing Li, nHang Jiang, nYing‐Lung Steve Tse, nTo Ngain

Oil-in-water-in-oil (O/W/O) Pickering double emulsions are stabilized by water and oil-swollen microgels. The binary microgels can efficiently reduce the interfacial tension and co-assemble on droplet surfaces. Owing to the thermal sensitivity of microgels, the destabilization of certain phases of double emulsions can be achieved by simply changing the ambient temperature.

Abstract

Microgels are excellent emulsifiers that can self-assemble to reduce interfacial tension and form a steric barrier at an oil-water interface. Herein, we report a two-step emulsification approach to prepare oil-in-water-in-oil (O/W/O) Pickering double emulsions through the dispersion of microgels in two immiscible phases. The stabilization mechanism depends on the uneven distribution and adsorption of hydrophilic water-swollen microgels and hydrophobic octanol-swollen microgels on either outer water droplets or inner oil droplets. Our results reveal that binary microgels outperformed single microgels in terms of interfacial tension reduction and emulsion stabilization. Notably, the binary microgel-stabilized Pickering double emulsions show excellent temperature responsiveness owing to the intrinsic thermal sensitivity of microgels. Consequently, the selective and rapid release of encapsulated substances in different phases can be achieved through the adjustment of the ambient temperature.

Synthesis of Difluoromethylated Alkenes via Copper‐Catalyzed Protodefluorination of β‐(Trifluoromethyl)styrenes

Posted on 4 October 2023 by nTao Dong, nYibin Ye, nYanhui Wang, nKelvin Pak Shing Cheung, nGavin Chit Tsuin

Under typical copper-catalyzed hydroboration conditions, β-(trifluoromethyl)styrenes demonstrate unusal reactivities by forming difluoromethylated alkenes via a net protodefluorination process. This is also distinct from trifluoromethyl alkenes with alkyl substituents where defluoroborylation products predominate.

Abstract

Under typical copper-catalyzed hydroboration conditions, β-(trifluoromethyl)styrenes demonstrate unusal reactivities by forming difluoromethylated alkenes via a net protodefluorination process. This is also distinct from trifluoromethyl alkenes with alkyl substituents where defluoroborylation products predominate.

Alkynyl‐Protected Bimetallic Nanoclusters with a Hybrid Mackay Icosahedral Ag42Cu12Cl Kernel and an Octahedral Ag22Cu12 Kernel

Posted on 4 October 2023 by nFeng Hu, nZong‐Jie Guan, nShang‐Fu Yuan, nQuan‐Ming Wangn

Two novel alkynyl-protected silver-copper nanoclusters (Ph₄P)₂[Ag₂₂Cu₁₂(C≡CR)₂₈] and (Ph₄P)₃[Ag₄₂Cu₁₂Cl(C≡CR)₃₆] (Ag₂₂Cu₁₂ and Ag₄₂Cu₁₂Cl) were obtained by using a weak reducing agent diphenylsilane (Ph₂SiH₂). For the first time, a hybrid 55-atom two-shell Mackay icosahedron was found in Ag₄₂Cu₁₂Cl. The incorporation of a chloride in the metal icosahedron contributes to the stability of the cluster due to electronic and geometric factors.

Abstract

A facile strategy that directly reduces alkynyl-silver precursors and copper salts for the synthesis of bimetallic nanoclusters using the weak reducing agent Ph₂SiH₂ is demonstrated. Two alkynyl-protected concentric-shell nanoclusters, (Ph₄P)₂[Ag₂₂Cu₁₂(C≡CR)₂₈] and (Ph₄P)₃[Ag₄₂Cu₁₂Cl(C≡CR)₃₆] (Ag₂₂Cu₁₂ and Ag₄₂Cu₁₂Cl, R=bis(trifluoromethyl)phenyl), were successfully obtained and characterized by single-crystal X-ray diffraction and electro-spray ionization mass spectrometry. For the first time, a hybrid 55-atom two-shell Mackay icosahedron was found in Ag₄₂Cu₁₂Cl, which is icosahedral M₅₄Cl instead of M₅₅. The incorporation of a chloride in the metal icosahedron contributes to the stability of the cluster from both electronic and geometric aspects. Alkynyl ligands show various binding-modes including linear “RC≡C−Cu−C≡CR” staple motifs.

Visible‐Light‐Mediated Synthesis of α‐Ketoamides via Oxidative Amination of 2‐Bromoacetophenones Using Eosin Y as a Photoredox Catalyst

Posted on 4 October 2023 by nKaushal Kishor, nNeha Sharma Prabhakar, nKrishna Nand Singhn

A visible light-mediated photoredox synthesis of α-ketoamides has been accomplished via an oxidative amination of 2-bromoacetophenones.

Abstract

An oxidative amination of 2-bromoacetophenones has been accomplished to provide α-ketoamides by using photoredox catalysis with air as oxidant. The reactants are readily accessible, and the method is endowed with broad substrate scope and good functional group tolerance. The practicality of the approach is also shown by a gram-scale reaction.

Heat‐ and Pressure‐driven Room‐temperature Polymorphic Transition Accompanied with Switchable SHG Signal in a New Chiral Hexagonal Perovskite

Posted on 4 October 2023 by

Herein, we report a new chiral hexagonal perovskite, (R-hmpi)[CdCl₃] (1), which can be long-term stable yet easily interconvertible between two ordered crystalline phases (1 α and 1 β) at a pressure of ~12 MPa and a temperature of 120 °C. The two phases exhibit significantly distinct second-harmonic-generation signals because of different distorted degrees of inorganic chains.

Abstract

Endowing room-temperature polymorphs with both long-term stability and easy interconvertibility is a big challenge due to the complexity of intermolecular interactions. Herein, we present a chiral hexagonal perovskite (R-3-hydroxy-1-methylpiperidinium)[CdCl₃] having two room-temperature crystalline forms featuring obviously distinct second-harmonic-generation (SHG) signals with a high switching contrast of ~18 times. The two room-temperature forms could be long-term stable yet easily interconvertible through an irreversible thermal-induced phase transition and a pressure-driven backward transition, by switching hydrogen bonds via collective reorientation of ordered homochiral cations. Based on the essential role of homochiral organic cations in inducing switchable hydrogen bond linkages, this present instance provides good evidence that relatively irregular organic cations could induce more obvious inorganic chain deformations, thus endowing polymorphs with significantly different SHG signals at room temperature.

Design of Glycopolymers for Controlling the Interactions with Lectins

Posted on 4 October 2023 by nMasanori Nagao, nHikaru Matsumoto, nYoshiko Miuran

Carbohydrates are involved in our life activities through binding to corresponding lectins. Glycopolymer is one of the classes of the emerging materials in recent years that mimic the functions of the glycoconjugates on the cells. This review summarizes the research over the past decade on the design of glycopolymers with a focus on controlling the interactions with lectins.

Abstract

Carbohydrates are involved in life activities through the interactions with their corresponding proteins (lectins). Pathogen infection and the regulation of cell activity are controlled by the binding between lectins and glycoconjugates on cell surfaces. A deeper understanding of the interactions of glycoconjugates has led to the development of therapeutic and preventive methods for infectious diseases. Glycopolymer is one of the classes of the materials present multiple carbohydrates. The properties of glycopolymers can be tuned through the molecular design of the polymer structures. This review focuses on research over the past decade on the design of glycopolymers with the aim of developing inhibitors against pathogens and manipulator of cellular functions.

Synthesis, Molecular Packing and Semiconductor Properties of V‐Shaped N‐Heteroacene Dimers

Posted on 4 October 2023 by nYongming Xiong, nQi Gong, nQian Miaon

New V-shaped π-scaffolds are constructed by fusing two N-heteroacene units with either a rigid or flexible eight-membered ring. Their crystals exhibit interesting π-π interaction modes, which are dependent on the central connecting units and substituting groups. These π-π interactions between the V-shaped π-scaffolds have enabled the molecules to function as organic semiconductors in solution-processed field effect transistors.

Abstract

This article presents two groups of V-shaped π-scaffolds that consist of two N-heteroacene units fused with either a rigid or flexible eight-membered ring. These rigid and flexible N-heteroacene dimers were synthesized through the condensation of tetraphenylenetetraone with the corresponding diamine and the Pd-catalyzed cross-coupling of tetrabromodibenzo[a,e]cyclooctatetraene with the corresponding diamine, respectively. A comparison of electronic structures and properties of the two groups of V-shaped N-heteroacene dimers shows subtle difference between the rigid and flexible eight-membered ring linkers in forming extended π-systems. X-ray crystallography of these V-shaped molecules has revealed interesting π-π interaction modes, which are dependent on the central connecting units and substituting groups. These π-π interactions between the V-shaped π-scaffolds have enabled the molecules to function as organic semiconductors in solution-processed field effect transistors.