Structural Determination of Ionic Liquids with Theoretical Methods: C8mimBr and C8mimCl. Strength and Weakness of Current Force Fields

2010 ◽  
Vol 1 (7) ◽  
pp. 1095-1100 ◽  
Author(s):  
E. Bodo ◽  
L. Gontrani ◽  
A. Triolo ◽  
R. Caminiti
Keyword(s):  
Ionic Liquids ◽  
Force Fields ◽  
Structural Determination ◽  
Theoretical Methods

A Transferable, Polarisable Force Field for Ionic Liquids

2019 ◽  
Author(s):  
Kateryna Goloviznina ◽  
José N. Canongia Lopes ◽  
Margarida Costa Gomes ◽  
Agilio Padua
Keyword(s):  
Ionic Liquids ◽  
Force Field ◽  
Force Fields ◽  
Dipole Moments ◽  
Van Der Waals Interactions ◽  
First Principles Calculations ◽  
Ion Diffusion ◽  
Fixed Integer ◽  
Molecular Compounds ◽  
Induced Dipoles

A general, transferable polarisable force field for molecular simulation of ionic liquids and their mixtures with molecular compounds is developed. This polarisable model is derived from the widely used CL\&P fixed-charge force field that describes most families of ionic liquids, in a form compatible with OPLS-AA, one of the major force fields for organic compounds. Models for ionic liquids with fixed, integer ionic charges lead to pathologically slow dynamics, a problem that is corrected when polarisation effects are included explicitly. In the model proposed here, Drude induced dipoles are used with parameters determined from atomic polarisabilities. The CL\&P force field is modified upon inclusion of the Drude dipoles, to avoid double-counting of polarisation effects. This modification is based on first-principles calculations of the dispersion and induction contributions to the van der Waals interactions, using symmetry-adapted perturbation theory (SAPT) for a set of dimers composed of positive, negative and neutral fragments representative of a wide variety of ionic liquids. The fragment approach provides transferability, allowing the representation of a multitude of cation and anion families, including different functional groups, without need to re-parametrise. Because SAPT calculations are expensive an alternative predictive scheme was devised, requiring only molecular properties with a clear physical meaning, namely dipole moments and atomic polarisabilities. The new polarisable force field, CL\&Pol, describes a broad set set of ionic liquids and their mixtures with molecular compounds, and is validated by comparisons with experimental data on density, ion diffusion coefficients and viscosity. The approaches proposed here can also be applied to the conversion of other fixed-charged force fields into polarisable versions.<br>

Structural Determination of Certain Novel ER Complexes

2004 ◽  
Author(s):  
Ya-Ling Wu ◽  
Geoffrey L. Greene
Keyword(s):  
Structural Determination

Phytochemical Constituents of Annona reticulata and their Cytotoxic Activity

2020 ◽  
Vol 17 (3) ◽  
pp. 206-210
Author(s):  
Ty Viet Pham ◽  
Thang Quoc Le ◽  
Anh Tuan Le ◽  
Hung Quoc Vo ◽  
Duc Viet Ho
Keyword(s):  
Cytotoxic Activity ◽  
Cell Lines ◽  
Structural Determination ◽  
Phytochemical Investigation ◽  
Ic50 Values ◽  
Phytochemical Constituents ◽  
First Time ◽  
Annona Reticulata

A phytochemical investigation of the leaves of Annona reticulata led to the isolation and structural determination of β-sitosterol (1), ent-pimara-8(14),15-dien-19-oic acid (2), ent-pimara- 8(14),15-dien-19-ol (3), quercetin (4), quercetin 3-O-α-L-arabinopyranoside (5), and a mixture of quercetin 3-O-β-D-galactopyranoside (6a) and quercetin 3-O-β-D-glucopyranoside (6b). Of these, compounds 2 and 3 were isolated from the genus Annona for the first time. Compound 3 showed strong cytotoxicity against SK-LU-1 and SW626 cell lines with IC50 values of 17.64 ± 1.07 and 19.79 ± 1.41 μg mL-1, respectively.

Dispersive Liquid-Liquid Microextraction Based on Ionic Liquid and Spectrophotometric Determination of Bilirubin in Biological Samples

2020 ◽  
Vol 16 (5) ◽  
pp. 652-659
Author(s):  
Asiye A. Avan ◽  
Hayati Filik
Keyword(s):  
Ionic Liquid ◽  
Ionic Liquids ◽  
Biological Samples ◽  
Urine Samples ◽  
Spectrophotometric Detection ◽  
Full Color ◽  
Dispersive Liquid Liquid Microextraction ◽  
Urine And Serum ◽  
Liquid Microextraction

Background: An Ionic Liquid-based based Dispersive Liquid-Liquid Microextraction (IL-DLLME) method was not applied to preconcentration and determination of bilirubin. Ionic Liquids (ILs) are new chemical compounds. In recent years, Ionic Liquids (ILs) have been employed as alternative solvents to toxic organic solvents. Due to these perfect properties, ILs have already been applied in many analytical extraction processes, presenting high extraction yield and selectivity for analytes. Methods: In this study, IL-DLLME was applied to biological samples (urine and serum) for the spectrophotometric detection of bilirubin. For bilirubin analysis, the full-color development was based on the reaction with periodate in the presence of hydrochloric acid. The high affinity of bilirubin for the ionic liquid phase gave extraction percentages above 98% in 0.3 M HCl solution. Results: Several IL-extraction parameters were optimized and room temperature ionic liquid 1-butyl- 1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide and ethanol were used as extraction and disperser solution. The linear range was found in the range of 0.5-6.0 μM (0.3-3.5 μg mL-1) and the limits of detection of the proposed method was 0.5 μM (0.3 μg mL-1). The proposed method was applied for the preconcentration and separation of trace bilirubin in real urine samples. Also, the recoveries for bilirubin in spiked biological samples (urine and serum) were found to be acceptable, between 95-102%. Conclusion: The proposed IL-DLLMEapproach was employed for the enrichment and determination of trace levels of bilirubin in urine samples using NaIO4 as an oxidizing agent and Uv-vis spectrophotometric detection. The periodate oxidation of bilirubin is rapid, effective, selective, and simple to perform. The method contains only HCl, NaOI4, and an anionic surfactant. The method may be useful for economizing in the consumption of reagents in bilirubin determining. The IL-DLLMEmethod ensures a high yield and has a low toxicity no skin sensitization, no mutagenicity and no ecotoxicity in an aquatic environment since only very low quantities of an IL is required. For full-color formation, no any extra auxiliary reagents are required. Besides, the IL-DLLME technique uses a low-cost instrument such as Uv-vis which is present in most of the medical laboratories.

Structural Determination of the Hydrofullerene C60D36 by Neutron Diffraction

1998 ◽  
Vol 54 (3) ◽  
pp. 345-350 ◽  
Author(s):  
L. E. Hall ◽  
D. R. McKenzie ◽  
R. L. Davis ◽  
M. I. Attalla ◽  
A. M. Vassallo
Keyword(s):  
Neutron Diffraction ◽  
Density Function ◽  
Diffraction Data ◽  
Fourier Transformation ◽  
Structural Determination ◽  
Molecular Models ◽  
Reduced Density ◽  
C Nmr

A mixture of C60D36 with 24.5 \pm 4.5% C60 by weight has been analysed by neutron diffraction techniques. The diffraction data was converted to a reduced density function G(r) by Fourier transformation. The C60 component of the G(r) was subtracted out. This enabled a comparison for five molecular models of C60D36, with symmetries T, Th , S 6 and two D 3 d isomers, with the experimental G(r). This specimen of C60D36 was found to be best described by a T symmetry isomer, in agreement with 13C NMR and IR data for C60H36 [Attalla et al. (1993). J. Phys. Chem. pp. 6329–6331].

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