A Comparative Analysis of the Global Electrophilicity Power of Some Cationic Dyes. Understanding Selective Removal Dyes From Mixture Solution

Some bibliographic findings of dyes' adsorption from a mixture state suggest that certain dyes are more likely to be adsorbed first on the adsorbent surface than others, and therefore attracted strongly to the adsorbent surface. To explain the phenomenon, DFT calculations are applied. In this fact, the global electrophilicity index ω of some cationic dyes has been evaluated. The results show that, for studied electrophilic dyes, the molecule with the greatest global electrophilicity power is favored to be adsorbed on the surface's anionic sites. In addition, local electrophilic Parr and Fukui functions were introduced to characterize the most reactive adsorption sites properly and indicate successfully the same adsorption centers. The success of DFT calculations in explaining and predicting the selective dye was assessed.

Tailoring the cationic and anionic sites of LaFeO3-based perovskite generates multiple vacancies for efficient water oxidation

electrocatalysts for designing highly active and durable electrocatalysis for oxygen evolution reaction (OER). Herein, we successfully enable LaFeO3 (denoted LFO) perovskite with impressive OER activity by systematically tailoring the Fe...

Efficient separation of xylene isomers by a guest-responsive metal–organic framework with rotational anionic sites

The separation of xylene isomers (para-, meta-, orth-) remains a great challenge in the petrochemical industry due to their similar molecular structure and physical properties. Porous materials with sensitive nanospace and selective binding sites for discriminating the subtle structural difference of isomers are urgently needed. Here, we demonstrate the adaptively molecular discrimination of xylene isomers by employing a NbOF52−-pillared metal–organic framework (NbOFFIVE-bpy-Ni, also referred to as ZU-61) with rotational anionic sites. Single crystal X-ray diffraction studies indicate that ZU-61 with guest-responsive nanospace/sites can adapt the shape of specific isomers through geometric deformation and/or the rotation of fluorine atoms in anionic sites, thereby enabling ZU-61 to effectively differentiate xylene isomers through multiple C–H···F interactions. ZU-61 exhibited both high meta-xylene uptake capacity (3.4 mmol g−1) and meta-xylene/para-xylene separation selectivity (2.9, obtained from breakthrough curves), as well as a favorable separation sequence as confirmed by breakthrough experiments: para-xylene elute first with high-purity (≥99.9%), then meta-xylene, and orth-xylene. Such a remarkable performance of ZU-61 can be attributed to the type anionic binding sites together with its guest-response properties.

Synthesis of a New Class of Spirooxindole–Benzo[b]Thiophene-Based Molecules as Acetylcholinesterase Inhibitors

A series of new oxindole-based spiro-heterocycles bearing the benzo[b]thiophene motif were synthesized via a 1,3-dipolar cycloaddition reaction and their acetylcholinesterase (AChE) inhibitory activity was evaluated. All the synthesized compounds exhibited moderate inhibitory activities against AChE, while IIc was found to be the most active analog with an IC50 value of 20,840 µM·L−1. Its molecular structure was a 5-chloro-substituted oxindole bearing benzo[b]thiophene and octahydroindole moieties. Based on molecular docking studies, IIc was strongly bound to the catalytic and peripheral anionic sites of the protein through hydrophilic, hydrophobic, and π-stacking interactions with Asp74, Trp86, Tyr124, Ser125, Glu202, Ser203, Trp236, Trp286, Phe297, Tyr337, and Tyr341. These interactions also indicated that the multiplicity of the IIc aromatic core significantly favored its activity.

Anionic polymerization of acrylic thioester by using organic base

An acrylic thioester is polymerized with organic bases as the initiators via zwitterionic mechanisms involving propagation at the anionic sites.

Zeta Potential of Pyrite Particles in Concentrated Solutions of Monovalent Seawater Electrolytes and Amyl Xanthate

Charge screening and adsorption capacity of monovalent ions onto pyrite (Py) in aqueous suspensions and the effect of potassium amyl xanthate (PAX) has been studied by measuring the changes in zeta potential (zp) versus pH with streaming potential. PAX addition in the absence of salts leads to an increase in |zp| suggesting dissolution of the surface ferric hydroxides and recovery of bare Py, corroborating existing theories. In the presence of salt, addition of PAX at pH > 6, for which hydroxides interference in not expected, has little effect over the zp, except when Li is present. The water network around the polar head of PAX is expected to be similar to that of hydrated Li+ facilitating the linkage between them and, thus, the formation of Li-mediated Py–PAX bridges. We speculate that these bridges lead to a xanthate shield around anionic sites on Py, decreasing |zp|. An increased PAX dose amplifies the effect of Li as a Py activator but only at low salt. At high salt concentrations, >0.01 M, PAX molecules do not find room to percolate to the surface of Py. Results for monovalent cations should improve our understanding of copper flotation processes in the presence of Py in saltwater.

Interaction of a Cationic Surfactant with an Oppositely Charged Polymer

The interactions between the cationic surfactant Dodecyltrimethylammonium Bromide (DTAB) and anionic polymer sodium carboxymethyl cellulose (Na-CMC) in aqueous medium were studied at 300K over different concentrations of Na-CMC by tensiometry, conductometry, viscometry, turbidimetry and fluorimetry. Aggregation of surfactant was attained in two steps, the first being the monomeric adsorption of surfactants on anionic sites of the polymer saturating at lower concentrations of surfactant and the second one being the formation of micelles by surfactants at higher concentrations. Mainly, two types of interactions prevailed throughout namely, electrostatic and hydrophobic interactions. Due to the variation of the interactions depending on the concentrations of polymer, there has been considerable differences in the behavioural pattern of the profiles for the lower concentrations of polymer compared to that of the upper ones.