Toward a fuzzy atom view within the context of the quantum theory of atoms in molecules: quasi-atoms

The notion of quasi-atoms is introduced within the context of the quantum theory of atoms in molecules. Being a subset of the quantum divided basins that were introduced previously, quasi-atoms are the quantum subsystems that are practically indistinguishable from the topological atoms; thus, revealing the continuous evolution of quantum divided basins into topological atoms. This indistinguishability is rooted in the limited accuracy of chemical observations; they are not sensitive to discriminate a topological atom from its associated quasi-atoms. In this regard, it is disclosed that the set of quantum atoms is in a wide-range including members other than topological atoms; the quasi-atoms are concrete examples. Finally, the idea of the fuzzy set of atoms that is foreign to the disjoint partitioning schemes for which the orthodox QTAIM is a classic example is extended employing the set of quasi-atoms.     

The quantum divided basins: A new class of quantum subsystems

The rigorous theory of the quantum divided basins (QDB), the quantum subsystems emerging from the net zero‐flux equation, is considered in this article. This framework, the quantum theory of proper open subsystems, is derived from the extension of the quantum theory of atoms in molecules to encompass the new class of quantum subsystems. It is demonstrated that the regional hypervirial theorem and the associated regional observables as well as the subsystem variational procedure are all expressible for the QDB. The history of QDB is briefly reviewed and the bundles, which were introduced by other researchers, are offered as typical examples whereas new examples of QDB (not yet mentioned in literature) are also presented. Based on some model systems as well as the nitrogen molecule, the regional properties and the morphologies of typical QDB are scrutinized. It is also demonstrated that the QDB may be used to study the fine structure of the electron localization and delocalization. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

The quantum theory of atoms in positronic molecules: A case study on diatomic species

This article presents the first systematic study of a series of diatomic positronic species using the recently proposed regional approach: the quantum theory of atoms in positronic molecules (QTAIPM). This survey includes the LiH,e⁺, NaH,e⁺, LiF,e⁺, NaF,e⁺, BeO,e⁺, MgO,e⁺, CN^?,e⁺, and OH^?,e⁺ species as typical examples. The computational algorithm of the whole analysis is communicated and reviewed in detail. The topological analysis of the joint density distribution reveals topological structures similar to those observed for the purely electronic systems; that is, each system decomposes into two quantum atoms. By considering some of the regional properties of these quantum atoms, it is demonstrated that the positron affects them seriously through two different mechanisms: direct and indirect contributions, the latter refers to electronic and geometric relaxations. The computational results clearly reveal the fact that the regional properties of the quantum atoms of positronic molecules are not deducible from their purely electronic counterparts; thus, an independent analysis is required for each positronic molecule. The positronic population is considered as a typical regional property showing that the attachment of a positron to a purely electronic system enhances the polarization of the electronic distribution. The concept of regional positron affinities is also introduced and discussed as a nonroutine application of the QTAIPM. The results of this article set the stage for further study on the quantum atoms of polyatomic positronic species. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

A Simple and Convenient Strategy for the Synthesis of Tolanophanes: Synthesis,Characterization and Conformational Analysis of a Novel Tolanophane

The bromination/dehydrobromination of stilbenophanes as a practical, simple and efficient strategy is applied to the synthesis of tolanophanes 1a (n = 2) and 1b (n = 4). The method is significantly superior to the reported methods. A careful conformational study on a novel tolanophane 1b showed that the relative stability of its conformers is directly linked to both twist angle between the two arene rings and the orientation of the alkoxy groups. The strong interaction between 1b and CDCl₃ at ? 60°C is an unusual feature that is attributed to high restriction in its molecular motion.     

Preparation of Magnetic-Activated Carbon Nanocomposite and Its Application for Dye Removal from Aqueous Solution

A nanocomposite of activated carbon and iron oxide was prepared and characterized by x-ray diffraction and scanning electron microscopy methods. The prepared magnetic nanocomposite can be separated easily from water by an external magnet. The prepared magnetic nanocomposite was used as adsorbent for removal of Bismarck Brown (B.B.) as a dye pollutant from water. The adsorption studies include both equilibrium and kinetic aspects, and the results were modeled with different equations. The obtained results indicate that the prepared magnetic nanocomposite of iron oxide and activated carbon is one of the best adsorbents for the removal of B.B. from aqueous solution.     

A computational study on some viable targets for gas-phase synthesis of metal complexes of the cyclic (B6C)-2 and their bonding pattern

In this account, a detailed computational study is conducted to verify the geometric, energetic, and electronic properties of the planar cyclic (B 6C) (-2) (as the simplest carrier of hexacoordinate carbon) within some metal complexes. The [M(B 6C)] ((-)) (M = Li, Na, K) and [M(B 6C)] (M = Be, Mg, Ca) series are employed for this purpose. Relevant ab initio calculations at both DFT and post-HF levels vividly demonstrate that this dianion is stabilized considerably in the electric field generated by cations, whereas the geometrical and electronic properties of this ring remain almost intact in these complexes. The complementary topological analysis of charge densities confirms that cyclic (B 6C) (-2) within these complexes exhibits the same topological patterns as the naked dianion, thus confirming the presence of an unusual charge density distribution in this dianion. An electrostatic model is proposed that not only qualitatively but also quantitatively explains the observed computational trends in these complexes. This model successfully traces the polarization of the central carbon atom of the ring in the presence of a hard, multiply charged cation. To facilitate experimental detection, the photoelectron spectra of the [M(B 6C)] ((-)) (M = Li, Na, K) series are computed and the dominant features are extracted. Although considered species are not global minima on their potential energy hypersurfaces, their kinetic stabilities are verified and demonstrated unequivocally.     

Loading of ZIF-67 on silk with sustained release of iodine as biocompatible antibacterial fibers

Antibacterial fibers have great potential in numerous applications, including bandages, surgical robes, and surgical sutures, and play a significant role in our everyday lives. Here, zeolitic imidazolate framework-67 was synthesized using a green method on silk fibers through a layer-by-layer process under ultrasonic irradiation (ZIF-67@silk [U]) and without ultrasonic irradiation (ZIF-67@silk [B]). Then, iodine was loaded on ZIF-67@silk samples and were assessed as antibacterial fibers with iodine release. Four samples of ZIF-67@silk and I₂@ZIF-67@silk were characterized by FT-IR, PXRD, FE-SEM, TGA, BET, and UV–Vis spectroscopy. Finally, antibacterial activity of ZIF-67@silk (B and U) and I₂@ZIF-67@silk (B and U) on Staphylococcus aureus as Gram-positive bacteria and Escherichia coli as Gram-negative bacteria was investigated. In addition to ZIF-67@silk samples, iodine-loaded samples showed excellent antimicrobial facility.