De Novo Structure-Based Design of Bis-amidoxime Uranophiles

This paper presents a computational approach to the deliberate design of host architectures that recognize and bind specific guests. De novo molecule building software, HostDesigner, is interfaced with molecular mechanics software, PCModel, providing a tool for generating and screening millions of potential structures. The efficacy of this computer-aided design methodology is illustrated with a search for bis-amidoxime chelates that are structurally organized for complexation with the uranyl cation

De Novo Structure-Based Design of Ion-Pair Triple-Stranded Helicates

We present a generalized approach toward the design of ion-pair ML₃A helicates assembled by coordination of metal cations (M) and anions (A) by ditopic chelating ligands (L). This computational approach, based on de novo structure-based design principles implemented in the HostDesigner software, led to identification of synthetically accessible ditopic ligands that are structurally encoded to form charge-neutral ion-pair helicates with FeSO₄ or LnPO₄

Liberalization Of Account Of Operations With Capital And Violation Of Financial Stability

У статті досліджено вплив процесів фінансової лібералізації на стан макроекономічної та фінансової стійкості, альтернативні позиції щодо використання інструментів контролю над капіталом з метою нейтралізації проциклічного впливу міжнародних потоків капіталу.In the article influence of processes of financial liberalization is investigational on the state of macroeconomic and financial firmness, alternative positions in relation to the use of control instruments above a capital with the aim of neutralization of проциклічного influence of international streams of capital

Computer-Aided Design of Interpenetrated Tetrahydrofuran-Functionalized 3D Covalent Organic Frameworks for CO₂ Capture

Using computer-aided design, several interpenetrated imine-linked 3D covalent organic frameworks with diamondoid structures were assembled from tetrakis-4-formylphenylsilane as the tetrahedral node, and 3<i>R</i>,4<i>R</i>-diaminotetrahydrofuran as the link. Subsequently, the adsorption capacity of CO₂ in each framework was predicted using grand canonical Monte Carlo simulations. At ambient conditions, the 4-fold interpenetrated framework, with disrotatory orientation of the tetrahedral nodes and diaxial conformation of the linker, displayed the highest adsorption capacity (∼4.6 mmol/g). At lower pressure, the more stable 5-fold interpenetrated framework showed higher uptake due to stronger interaction of CO₂ with the framework. The contribution of framework charges to CO₂ uptake was found to increase as the pore size decreases. The effect of functional group was further explored by replacing the ether oxygen with the CH₂ group. Although no change was observed in the 1-fold framework, the CO₂ capacity at 1 bar decreased by ∼32% in the 5-fold interpenetrated framework. This work highlights the need for a synergistic effect of a narrow pore size and a high density of ether-oxygen groups for high-capacity CO₂ adsorption

Design Criteria for Polyazine Extractants To Separate An^III from Ln^III

Although polyazine extractants have been extensively studied as agents for partitioning trivalent actinides from lanthanides, an explanation for why certain azine compositions succeed and others fail is lacking. To address this issue, density functional theory calculations were used to evaluate fundamental properties (intrinsic binding affinity for a representative trivalent f-block metal, basicity, and hardness) for prototype azine donors pyridine, pyridazine, pyrimidine, pyrazine, 1,2,3-triazine, 1,2,4-triazine, and 1,3,5-triazine, as well as perform conformational analyses of bisazine chelates formed by directly connecting two donors together. The results provide criteria that both rationalize the behavior of known extractants, TERPY, TPTZ, hemi-BTP, BTP, BTBP, and BTPhen, and predict a new class of extractants based on pyridazine donor groups

Molecular Dynamics Simulation of Tri-<i>n</i>-butyl-Phosphate Liquid: A Force Field Comparative Study

Molecular dynamics (MD) simulations were conducted to compare the performance of four force fields in predicting thermophysical properties of tri-<i>n</i>-butyl-phosphate (TBP) in the liquid phase. The intramolecular force parameters used were from the Assisted Model Building with Energy Refinement (AMBER) force field model. The van der Waals parameters were based on either the AMBER or the Optimized Potential for Liquid Simulation (OPLS) force fields. The atomic partial charges were either assigned by performing quantum chemistry calculations or utilized previously published data, and were scaled to approximate the average experimental value of the electric dipole moment. Canonical ensemble computations based on the aforementioned parameters were performed near atmospheric pressure and temperature to obtain the electric dipole moment, mass density, and self-diffusion coefficient. In addition, the microscopic structure of the liquid was characterized via pair correlation functions between selected atoms. It has been demonstrated that the electric dipole moment can be approximated within 1% of the average experimental value by virtue of scaled atomic partial charges. The liquid mass density can be predicted within 0.5–1% of its experimentally determined value when using the corresponding charge scaling. However, in all cases, the predicted self-diffusion coefficient is significantly smaller than a commonly quoted experimental measurement; this result is qualified by the fact that the uncertainty of the experimental value was not available

How Amidoximate Binds the Uranyl Cation

This study identifies how the amidoximate anion, AO, interacts with the uranyl cation, UO₂²⁺. Density functional theory calculations have been used to evaluate possible binding motifs in a series of [UO₂(AO)_<i>x</i>(OH₂)_<i>y</i>]^2–<i>x</i> (<i>x</i> = 1–3) complexes. These motifs include monodentate binding to either the oxygen or the nitrogen atom of the oxime group, bidentate chelation involving the oxime oxygen atom and the amide nitrogen atom, and η² binding with the N–O bond. The theoretical results establish the η² motif to be the most stable form. This prediction is confirmed by single-crystal X-ray diffraction of UO₂²⁺ complexes with acetamidoxime and benzamidoxime anions

Bipyrrole-Strapped Calix[4]pyrroles: Strong Anion Receptors That Extract the Sulfate Anion

Cage-type calix­[4]­pyrroles <b>2</b> and <b>3</b> bearing two additional pyrrole groups on the strap have been synthesized. Compared with the parent calix[4]­pyrrole (<b>1</b>), they were found to exhibit remarkably enhanced affinities for anions, including the sulfate anion (TBA⁺ salts), in organic media (CD₂Cl₂). This increase is ascribed to participation of the bipyrrole units in anion binding. Receptors <b>2</b> and <b>3</b> extract the hydrophilic sulfate anion (as the methyltrialkyl­(C_8–10)­ammonium (A336⁺) salt) from aqueous media into a chloroform phase with significantly improved efficiency (>10-fold relative to calix[4]­pyrrole <b>1</b>). These two receptors also solubilize into chloroform the otherwise insoluble sulfate salt, (TMA)₂SO₄ (tetramethylammonium sulfate)

Pyrrole- and Naphthobipyrrole-Strapped Calix[4]pyrroles as Azide Anion Receptors

The binding interactions between the azide anion (N₃^–) and the strapped calix[4]­pyrroles <b>2</b> and <b>3</b> bearing auxiliary hydrogen bonding donors on the bridging moieties, as well as of normal calix[4]­pyrrole <b>1</b>, were investigated via ¹H NMR spectroscopic and isothermal titration calorimetry analyses. The resulting data revealed that receptors <b>2</b> and <b>3</b> have significantly higher affinities for the azide anion in organic media as compared with the unfunctionalized calix[4]­pyrrole <b>1</b> and other azide receptors reported to date. Single crystal X-ray diffraction analyses and calculations using density functional theory revealed that receptor <b>2</b> binds CsN₃ in two distinct structural forms. As judged from the metric parameters, in the resulting complexes one limiting azide anion resonance contributor is favored over the other, with the specifics depending on the binding mode. In contrast to what is seen for <b>2</b>, receptor <b>3</b> forms a CsN₃ complex in 20% CD₃OD in CDCl₃, wherein the azide anion is bound only vertically to the NH protons of the calix[4]­pyrrole and the cesium cation is complexed within the cone shaped-calix[4]­pyrrole bowl. The bound cesium cation is also in close proximity to a naphthobipyrrole subunit present in a different molecule, forming an apparent cation-π complex

Pyrrole- and Naphthobipyrrole-Strapped Calix[4]pyrroles as Azide Anion Receptors

The binding interactions between the azide anion (N₃^–) and the strapped calix[4]­pyrroles <b>2</b> and <b>3</b> bearing auxiliary hydrogen bonding donors on the bridging moieties, as well as of normal calix[4]­pyrrole <b>1</b>, were investigated via ¹H NMR spectroscopic and isothermal titration calorimetry analyses. The resulting data revealed that receptors <b>2</b> and <b>3</b> have significantly higher affinities for the azide anion in organic media as compared with the unfunctionalized calix[4]­pyrrole <b>1</b> and other azide receptors reported to date. Single crystal X-ray diffraction analyses and calculations using density functional theory revealed that receptor <b>2</b> binds CsN₃ in two distinct structural forms. As judged from the metric parameters, in the resulting complexes one limiting azide anion resonance contributor is favored over the other, with the specifics depending on the binding mode. In contrast to what is seen for <b>2</b>, receptor <b>3</b> forms a CsN₃ complex in 20% CD₃OD in CDCl₃, wherein the azide anion is bound only vertically to the NH protons of the calix[4]­pyrrole and the cesium cation is complexed within the cone shaped-calix[4]­pyrrole bowl. The bound cesium cation is also in close proximity to a naphthobipyrrole subunit present in a different molecule, forming an apparent cation-π complex