Complexation of a macrocyclic ligand, 2,6-di (N-methyl)formamide-calix[4]pyridine, with Eu(III) and extraction of Eu(III) and Am(III)

2018 ◽  
Vol 106 (4) ◽  
pp. 301-310
Author(s):  
Lina Lü ◽  
Jun Liu ◽  
Yanqiu Yang ◽  
Kun Li ◽  
Sheng Hu ◽  
...  
Keyword(s):  
Aqueous Phase ◽  
Macrocyclic Ligand ◽  
Macrocyclic Compound ◽  
Aprotic Solvents ◽  
Computational Studies ◽  
Computational Results ◽  
Binding Ability ◽  
Protic Solvents ◽  
Aqueous Acidity ◽  
The Eu

AbstractComplexation of a new macrocyclic compound, 2,6-dimethylformamide-calix[4]pyridine (L1), with Eu(III) was studied by spectrophotometry. Stability constants of the Eu(III)/L1complex in different solvents were determined. The results reveal thatL1forms moderately strong complexes with Eu(III) and other lanthanides in aprotic solvents and shows little binding ability with transition metals. Moreover, the binding strength ofL1weakens significantly in protic solvents. Using 2-bromodecanoic acid as the synergistic reagent,L1extracts Am(III) and Eu(III) successfully with a separation factor of SFAm/Eu=1.3, and the distribution ratios of Am(III) and Eu(III) increases as the aqueous acidity is decreased. DFT computational studies were conducted to corroborate the solvent extraction data, and compare the coordination properties of Am(III)/Eu(III) complexes withL1and a related, 2,6-diformamide-calix[4]pyridine (L2). The computational results suggest thatL2could form stable complexes [ML]3+and ML(NO3)3[where M represent Am(III) or Eu(III)] in aqueous phase, in sharp contrast to the case ofL1where such complexes in aqueous phase are not stable.

Anion effect on alkali ion-crown complex formation in a moderately concentrated solutions: A sensitive probe of hidden interionic interactions operating in dissociating protic solvents

1990 ◽  
Vol 55 (5) ◽  
pp. 1149-1161
Author(s):  
Jiří Závada ◽  
Václav Pechanec ◽  
Oldřich Kocián
Keyword(s):  
Hydrogen Bond ◽  
Complex Formation ◽  
Charge Density ◽  
Macrocyclic Ligand ◽  
Simple Explanation ◽  
Anion Effect ◽  
Protic Solvents ◽  
The Individual ◽  
Alkali Salts ◽  
Alkali Ion

A powerful anion effect destabilizing alkali ion-crown complex formation has been found to operate in moderately concentrated protic (H2O, CH3OH, C2H5OH) solution, following the order HO- > AcO- > Cl- > Br- > NO3- > I- > NCS-. Evidence is provided that the observed effect does not originate from ion-pairing. A simple explanation is provided in terms of concordant hydrogen bond bridges of exalted stability between the gegenions, M+···OR-H···(OR-H)n···OR-H···A-. It is proposed that encapsulation of alkali ion by the macrocyclic ligand leads to a dissipation of the cation charge density destroying its ability to participate in the hydrogen bond bridge. An opposition against the alkali ion-crown complex formation arises accordingly in the solution in dependence on strength of the hydrogen bridge; for a given cation, the hydrogen bond strength increases with increasing anion charge density from NCS- to HO-(RO-). It is pointed out, at the same time, that the observed anion effect does not correlate with the known values of activity coefficients of the individual alkali salts which are almost insensitive to anion variation under the investigated conditions. As a resolution of the apparent paradoxon it is proposed that, in absence of the macrocyclic ligand, the stabilizing (concordant) bonding between the gegenions is nearly balanced by a destabilizing (discordant) hydrogen bonding between the ions of same charge (co-ions). Intrinsic differences among the individual salts are thus submerged in protic solvents and become apparent only when the concordant bonding is suppressed in the alkali ion-crown complex formation.

scholarly journals Reactivity of cyclohex-1-enylcarboxylic and 2-methylcyclohex-1-enylcarboxylic acids with diazodiphenylmethane in aprotic solvents

2000 ◽  
Vol 65 (12) ◽  
pp. 839-846
Author(s):  
Jasmina Nikolic ◽  
Gordana Uscumlic ◽  
Vera Krstic
Keyword(s):  
Hydrogen Bond ◽  
Rate Constants ◽  
Kinetic Data ◽  
Linear Regression Analysis ◽  
Spectroscopic Method ◽  
Reaction Rates ◽  
Aprotic Solvents ◽  
Experimental Conditions ◽  
Hydrogen Bond Acceptor ◽  
Protic Solvents

Rate constants for the reaction of diazodiphenylmethane with cyclohex-1-enylcarboxylic acid and 2-methylcyclohex-1-enylcarboxylic acid were determined in nine aprotic solvents, as well as in seven protic solvents, at 30?C using the appropriate UV-spectroscopic method. In protic solvents the unsubsituted acid displayed higher reaction rates than the methyl-substituted one. The results in aprotic solvents showed quite the opposite, and the reaction rates were considerably lower. In order to explain the obtained results through solvent effects, reaction rate constants (k) of the examined acids were correlated using the total solvatochromic equation of the form: log k=logk0+s?*+a?+b?, where ?* is the measure of the solvent polarity, a represents the scale of the solvent hydrogen bond donor acidities (HBD) and b represents the scale of the solvent hydrogen bond acceptor basicities (HBA). The correlation of the kinetic data were carried out by means of multiple linear regression analysis and the opposite effects of aprotic solvents, as well as the difference in the influence of protic and aprotic solvents on the reaction of the two examined acids with DDM were discussed. The results presented in this paper for cyclohex-1-enylcarboxylic and 2-methylcyclohex-1-enylcarboxylic acids were compared with the kinetic data for benzoic acid obtained in the same chemical reaction, under the same experimental conditions.

Solvent effects on the decarboxylation of trichloroacetic acid: insights from ab initio molecular dynamics simulations

2018 ◽  
Vol 20 (34) ◽  
pp. 21988-21998 ◽  
Author(s):  
Guilherme C. Q. da Silva ◽  
Thiago M. Cardozo ◽  
Giovanni W. Amarante ◽  
Charlles R. A. Abreu ◽  
Bruno A. C. Horta
Keyword(s):  
Molecular Dynamics ◽  
Ab Initio ◽  
Molecular Dynamics Simulations ◽  
Solvent Effects ◽  
Trichloroacetic Acid ◽  
Ab Initio Molecular Dynamics ◽  
Aprotic Solvents ◽  
Protic Solvents ◽  
Dynamics Simulations ◽  
Kinetics Of

The kinetics of trichloroacetic acid (TCA) decarboxylation strongly depends on the solvent in which it occurs, proceeding faster in polar aprotic solvents compared to protic solvents.

Computational Modeling and Validation of the Encapsulation of Plastic Packages by Transfer Molding

1999 ◽  
Vol 122 (2) ◽  
pp. 138-146 ◽  
Author(s):  
L. Nguyen ◽  
C. Quentin ◽  
W. Lee ◽  
S. Bayyuk ◽  
S. A. Bidstrup-Allen ◽  
...  
Keyword(s):  
Computational Modeling ◽  
Experimental Measurements ◽  
Computational Studies ◽  
Computational Results ◽  
Flow Front ◽  
Transfer Molding ◽  
Plastic Packages ◽  
Encapsulation Process ◽  
Computational Predictions ◽  
Good Agreement

This paper presents, discusses, and compares results from experimental and computational studies of the plastic encapsulation process for a 144-lead TQFP package. The experimental results were obtained using an instrumented molding press, while the computational predictions were obtained using a newly-developed software for modeling transfer molding processes. Validation of the software is emphasized, and this was done mainly by comparing the computational results with the corresponding experimental measurements for pressure, temperature, and flow front advancement in the cavities and runners. The experimental and computational results were found to be in good agreement, especially for the flow-front shapes and locations. [S1043-7398(00)00502-8]

Tautomerism of 5-nitro-2-furylnitromethane

1981 ◽  
Vol 46 (12) ◽  
pp. 3122-3127
Author(s):  
Iva Sroková ◽  
Pavel Vetešník ◽  
Adolf Jurášek ◽  
Jaroslav Kováč
Keyword(s):  
Kinetic Study ◽  
Temperature Dependence ◽  
Thermodynamic Parameters ◽  
Rate Constants ◽  
Strong Acid ◽  
Ion Pair ◽  
Aprotic Solvents ◽  
Protic Solvents ◽  
Parallel Reactions ◽  
Experimental Values

UV study of properties of 5-nitro-2-furylnitromethane (I) in various solvents has shown that this compound is a very strong acid (pKa 3.98) forming an ion pair in protic solvents (water, alcohols) and existing exclusively as nitro-form in aprotic solvents (tetrachloromethane, chloroform, n-hexane, diethyl ether, dioxane). Kinetic study of tautomerism in water has given experimental values of combined rate constants of parallel reactions. Thermodynamic parameters of the tautomeric transformations have been calculated from temperature dependence of the rate constants.

A Computational Perspective on Molecular Recognition by Galectins

2021 ◽  
Vol 28 ◽  
Author(s):  
Reyes Núñez-Franco ◽  
Francesca Peccati ◽  
Gonzalo Jiménez-Osés
Keyword(s):  
Binding Energies ◽  
Computational Studies ◽  
Computational Results ◽  
Future Perspectives ◽  
Computational Approaches ◽  
Simulation Techniques ◽  
Small Molecule Ligands ◽  
Ligand Interactions ◽  
Entropy Effects ◽  
Mature Field

: This article presents an overview of recent computational studies dedicated to the analysis of binding between galectins and small-molecule ligands. We first present a summary of the most popular simulation techniques adopted for calculating binding poses and binding energies, and then discuss relevant examples reported in the literature for the three main classes of galectins (dimeric, tandem and chimera). We show that simulation of galectin-ligand interactions is a mature field which has proven invaluable for completing and unraveling experimental observations. Future perspectives to further improve the accuracy and cost-effectiveness of existing computational approaches will involve the development of new schemes to account for solvation and entropy effects, which represent the main current limitations to the accuracy of computational results.

Complexation of diazinon, an organophosphorus pesticide, with α-, β-, and γ-cyclodextrin — NMR and computational studies

2006 ◽  
Vol 84 (4) ◽  
pp. 702-708 ◽  
Author(s):  
Doreen Churchill ◽  
Jason Chiu Fung Cheung ◽  
Yong Sung Park ◽  
Vedene H Smith ◽  
Gary vanLoon ◽  
...  
Keyword(s):  
Molecular Mechanics ◽  
Density Functional ◽  
Organophosphorus Pesticides ◽  
Organophosphorus Pesticide ◽  
Binding Constants ◽  
Computational Studies ◽  
Computational Results ◽  
Isopropyl Group ◽  
Functional Theory ◽  
Clear Differentiation

Complexation of the organophosphorus pesticide, diazinon, with α-, β- and γ- cyclodextrin has been investigated through NMR and computational methodologies. Binding constants (Kb) determined by 1H and 31P NMR follow the order γ-CD > α-CD = β-CD, in contrast with reported Kb data for other pesticides and thus indicative of steric encumbrance by the isopropyl group in diazinon being an important factor influencing binding constants. The interaction of diazinon with the CDs has also been investigated through computational studies via molecular dynamics – molecular mechanics (MD–MM2) and density functional theory (DFT), B3LYP/6-31G*. It is shown that the most favorable orientation in binding corresponds to the hydrophobic heterocyclic residue of diazinon being pulled deepest into the CD cavity, in agreement with the experimentally determined order of binding constants. Moreover, the computations show that it is only with γ-CD that the heterocyclic residue of diazinon and the phosphoryl residue are both largely encrypted in the CD cavity, marking a clear differentiation with α-CD and β-CD where the phosphoryl residue is located largely outside the cavity. Thus, the computational results are in essential agreement with the experimental binding constants where γ-CD stands out with the highest Kb value. Our work could point to the potential usefulness of computational studies to be undertaken in tandem with experimental work in environmental situations such as soil remediation.Key words: organophosphorus pesticides, diazinon complexation, cyclodextrins, computational studies, molecular mechanics.

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