Hexaphenylbenzene-Stabilized Luminescent Silver Nanoclusters: A Potential Catalytic System for the Cycloaddition of Terminal Alkynes with Isocyanides

A hexaphenylbenzene (HPB)-based derivative bearing thiol groups has been designed and synthesized that undergoes aggregation-induced emission enhancement in mixed aqueous media to form rodlike fluorescent aggregates. These rodlike aggregates behave as a “not quenched” probe for the detection of silver ions and further act as reactors and stabilizers for reducing-agent-free preparation of blue luminescent silver nanoclusters at room temperature. The utilization of fluorescent supramolecular aggregates for the preparation of Ag NCs in mixed aqueous media is unprecedented in the literature. Moreover, the wet chemical method that we are reporting in the present paper for the preparation of luminescent silver nanoclusters is better than the other methods reported in the literature. Further, these in situ generated Ag NCs showed exceptional catalytic activity in the preparation of pyrroles involving cocyclization of isocyanides and terminal alkynes. Interestingly, the catalytic efficiency of in situ generated Ag NCs was found to be better than the other catalytic systems reported in the literature

Hexaphenylbenzene-Based Fluorescent Aggregates for Ratiometric Detection of Cyanide Ions at Nanomolar Level: Set–Reset Memorized Sequential Logic Device

A hexaphenylbenzene-based receptor <b>3</b> has been synthesized that forms a fluorescent spherical aggregate in mixed aqueous media due to its aggregation-induced emission enhancement attributes. These fluorescent spherical aggregates show ratiometric response toward cyanide ions via nucleophilic addition and undergo deaggregation to form smaller nanoaggregates. In addition, the solution-coated paper strips of <b>3</b> can detect cyanide ions in the range of ∼2.6 ng/cm², thus, providing a simple, portable, and low-cost method for detection of cyanide ions in aqueous media. Receptor <b>3</b> also behaves as a set–reset memorized sequential logic circuit with chemical inputs of CN^– ions and trifluoroacetic acid or H⁺ (pH ≤ 3)

AIEE Active Donor–Acceptor–Donor-Based Hexaphenylbenzene Probe for Recognition of Aliphatic and Aromatic Amines

In the present investigation, an intramolecular charge transfer (ICT) and aggregation induced emission enhancement (AIEE) active donor–acceptor–donor (D-A-D) system <b>5</b> having fumaronitrile as the acceptor and hexaphenylbenzene (HPB) as the donor moieties joined through rotatable phenyl rings has been designed and synthesized that is highly emissive in the solid state and exhibits stimuli-responsive reversible piezochromic behavior upon grinding and heating. Because of its AIEE characteristics, HPB derivative <b>5</b> undergoes aggregation to form fluorescent aggregates in mixed aqueous media that exhibit ratiometric fluorescence response toward aliphatic amines (primary/secondary/tertiary) and turn-off response toward aromatic amines and hence differentiates between them. Further, the solution-coated portable paper strips of derivative <b>5</b> showed pronounced and sensitive response toward aromatic and aliphatic amines with a detection limit in the range of picogram and nanogram level, respectively

Polythiophene-Encapsulated Bimetallic Au-Fe₃O₄ Nano-Hybrid Materials: A Potential Tandem Photocatalytic System for Nondirected C(sp²)–H Activation for the Synthesis of Quinoline Carboxylates

Hetero-oligophenylene derivative <b>3</b> appended with thiophene moieties has been designed and synthesized which undergoes aggregation to form <i>J</i>-type fluorescent aggregates in in H₂O/THF (7/3) media. These aggregates served as reactors for the preparation of bimetallic Au-Fe₃O₄ NPs. During the reduction process, aggregates of derivative <b>3</b> were oxidized to the polythiophene species <b>4</b>. Interestingly, the polythiophene species <b>4</b>, having a fibrous morphology, served as a shape- and morphology-directed template for assembly of bimetallic Au-Fe₃O₄ NPs in a flower-like arrangement. Furthermore, polythiophene-encapsulated bimetallic <b>4</b>:Au-Fe₃O₄ nanohybrid materials served as an efficient and recyclable catalytic system for C­(sp²)–H bond activation of unprotected electron-rich anilines for the construction of synthetically versatile quinoline carboxylates via C–H activation, carbonylation, and subsequent annulation under mild and eco-friendly conditions (aqueous media, room temperature, visible-light irradiation, and aerial conditions)

Supramolecular Ensemble of a TICT-AIEE Active Pyrazine Derivative and CuO NPs: A Potential Photocatalytic System for Sonogashira Couplings

The donor–acceptor system <b>4</b> having pyrazine scaffold as an acceptor moiety coupled to donor amino groups through rotatable phenyl rings has been synthesized, which formed aggregates in aqueous media, exhibited copper induced restriction to intramolecular rotation, and served as a “not quenched” probe for the detection of copper­(II) ions. During this process, the aggregates of derivative <b>4</b> acted as reactors and stabilizers for the generation of CuO NPs and themselves became oxidized to form polyamine derivative <b>6</b>. Interestingly, the oxidized species <b>6</b> in combination with copper oxide nanoparticles served as light-harvesting antennas and exhibited excellent photocatalytic efficiency in Sonogashira coupling under mild and eco-friendly conditions (room temperature, aqueous media, aerial conditions, and visible light irradiation)

Characterizing Hydrogen-Bond Interactions in Pyrazinetetracarboxamide Complexes: Insights from Experimental and Quantum Topological Analyses

Experimental and topological analyses of dipalladium­(II) complexes with pyrazinetetracarboxamide ligands containing tetraethyl (<b>1</b>), tetrahexyl (<b>2</b>), and tetrakis­(2-hydroxyethyl) ethyl ether (<b>3</b>) are described. The presence of two very short O---O distances between adjacent amide carbonyl groups in the pincer complexes revealed two protons, which necessitated two additional anions to satisfy charge requirements. The results of the crystal structures indicate carbonyl O---O separations approaching that of low barrier hydrogen bonds, ranging from 2.413(5) to 2.430(3) Å. Solution studies and quantum topological analyses, the latter including electron localization function, noncovalent interaction, and Bader’s quantum theory of atoms in molecules, were carried out to probe the nature of the short hydrogen bonds and the influence of the ligand environment on their strength. Findings indicated that the ligand field, and, in particular, the counterion at the fourth coordination site, may play a subtle role in determining the degree of covalent association of the bridging protons with one or the other carbonyl groups