Evaluation Of Solvent Effects Research Articles

Evaluation of solvent effects on the DPPH reactivity for determining the antioxidant activity in oil matrix.

The online version contains supplementary material available at 10.1007/s10068-020-00874-9.

Dye sensitized solar cell action of Sn(IV)tetrakis(4-pyridyl) porphyrins as a function of axial ligation and pyridine protonation

This contribution reports on the photosensitizing competence of Sn(IV)tetrakis(4-pyridyl)porphyrins (SnTP) for potential applications in dye sensitized solar cell (DSSC). The photosensitization of SnTPs is accounted on the basis of different axial ligands (OH−, Cl−, and H2O) and the pyridine protons. The qualitative information on the photovoltaic performance of the sensitizers is obtained at B3LYP/6-31+G(d) level of theory with LANL2DZ basis set for Sn atom through the calculation of parameters such as free energy change of electron injection ( $$\Delta G^{\text{inject}}$$ ) and regeneration ( $$\Delta G^{\text{reg}}$$ ), oxidation potentials, exciton binding energy, open-circuit voltage, light harvesting efficiency and quantum reactivity descriptors. The evaluation of solvent effects is carried out in Tetrahydrofuran (THF) and Dimethylformamide (DMF) solutions employing conductor-like polarizable continuum model (C-PCM). The overall results emphasize that the enhanced photo-sensing action can be achieved by the Sn complexes having OH− and Cl− ligands without pyridine protonation. Axial ligation and pyridine protonation significantly affect the electronic excitation properties of Sn complexes. The overall results recommend the application of [(OH−)Sn(OH−)TP] and [(Cl−)Sn(Cl−)TP] photosensitizers in dye sensitized solar cells.

An evaluation of solvent effects and ethanol oxidation.

Understanding liquid-metal interfaces in catalysis is important, as the liquid can speed up surface reactions, increase the selectivity of products, and open up new favorable reaction pathways. In this work we modeled using density functional theory various steps in ethanol oxidation/decomposition over Rh(111). We considered implicit (continuum), explicit, and hybrid (implicit combined with explicit) solvation approaches, as well as two solvents, water and ethanol. We focused on modeling adsorption steps, as well as C-C/C-H bond scission and C-O bond formation reactions. Implicit solvation had very little effect on adsorption and reaction free energies. However, using the explicit and hybrid models, some free energies changed significantly. Furthermore, ethanol solvent had a more considerable impact than water solvent. We observed that preferred reaction pathways for C-C scission changed depending on the solvation model and solvent choice (ethanol or water). We also applied the bond-additivity solvation method to calculate heats of adsorption. Heats of adsorption and reaction using the bond-additivity model followed the same trends as the other solvation models, but were ∼1.1 eV more endothermic. Our work highlights how different solvation approaches can influence analysis of the oxidation/decomposition of organic surface species.

Evaluation of Solvent Effect (Methanol: Water Mixture) on the Phenolic Content and Antioxidant Activities of Stachys turcomanica Trautv

Background: The genus of Stachys with 300 species belongs to Lamiaceae family and this genus has 34 species in Iran. Stachys turcomanica Trautv is native to Iran and it used for treatment of infectious, rheumatic and inflammatory diseases in traditional medicine. The effect of solvent (methanol in water: 0, 20, 50, 80 and 100 %) on the extraction of antioxidant compounds from S. turcomanica were investigated using various in vitro assays. Methods: The antioxidant activities of extracts were studied via three methods: FRAP (ferric reducing antioxidant power), DPPH (2, 2-diphenyl-1-picrylhydrazyl) and beta-carotene linoleic acid bleaching. Results: The results of present work revealed that the solvent combinations have effects on the extraction of phenolic compounds and antioxidant properties. The relative methanol/water ratio of 80:20 v/v was effective solvent in the extracting of phenolic compounds. Also, there was a good correlation between antioxidant activity and total phenolic content S. turcomanica extracts. Conclusion: The results demonstrated methanol/water (80:20) ratio was the best solvent to release of many secondary metabolites from S. turcomanica for future studies, which could provide natural sources of antioxidant compounds.

Evaluation of solvent effect on the amine-based CO2 absorbents by theory and experiment

The three-dimensional reference interaction site model (3D-RISM) integral equation is applied to predict the hydration free-energies and solution enthalpies at infinite dilution for amines and alkanolamines. In particular, the closure equation for 3D-RISM is integrated with the bridge functions derived from minimizing the hard-sphere free-energy functional for different interactions. The density distributions of water molecules around different solute molecules are calculated to intuitively describe the solvent effects. The solution enthalpies and hydration free-energies are then determined by the density distributions. Meanwhile, the solution enthalpies for some alkanolamines with low volatility are measured, and the values at infinite dilution are thereby obtained through extrapolation. It is shown that the theoretical predictions are generally in agreement with the experimental results, suggesting that the current theoretical approach is reasonable to quantitatively evaluate the solvent effect of various amine-based CO2 absorbents.

Evaluation of solvent effect on the extraction of phenolic compounds and antioxidant capacities from the berries: application of principal component analysis.

BackgroundThis study evaluated the effect of the solvent on the extraction of antioxidant compounds from black mulberry (Morus nigra), blackberry (Rubus ulmifolius) and strawberry (Fragaria x ananassa). Different extracts of each berry were evaluated from the determination of total phenolic content, anthocyanin content and antioxidant capacity, and data were applied to the principal component analysis (PCA) to gain an overview of the effect of the solvent in extraction method.ResultsFor all the berries analyzed, acetone/water (70/30, v/v) solvent mixture was more efficient solvent in the extracting of phenolic compounds, and methanol/water/acetic acid (70/29.5/0.5, v/v/v) showed the best values for anthocyanin content. Mixtures of ethanol/water (50/50, v/v), acetone water/acetic acid (70/29.5/0.5, v/v/v) and acetone/water (50/50, v/v) presented the highest antioxidant capacities for black mulberries, blackberries and strawberries, respectively.ConclusionAntioxidants extractions are extremely affected by the solvent combination used. In addition, the obtained extracts with the organic solvent-water mixtures were distinguished from the extracts obtained with pure organic solvents, through the PCA analysis.Electronic supplementary materialThe online version of this article (doi:10.1186/s13065-014-0048-1) contains supplementary material, which is available to authorized users.

Evaluation of solvent effects on protonation using NMR spectroscopy: Implication in salt formation

Investigation of the use of solution NMR spectroscopy to determine the effect of organic solvents on chemical shift changes in bases on addition of acids is reported. This information can be useful in the evaluation of solvents and counterion selection for salt formation. 1H and 15N chemical shift changes in three bases (pyrazine, phthalazine, and pyridine) on the addition of acids (1:1 ratio) were determined in various solvents. The effect of acid strength on chemical shift changes was examined. 1H and 15N chemical shift changes indicated protonation (salt formation). The media used affected the observed chemical shift changes. In D 2O the data followed the Δp K a (base–acid) general rule, that the p K a value of the acids should be 2 units lower than the p K a of the base to ensure proton transfer. Protonation, as measured by chemical shift changes using solution NMR spectroscopy, provided novel insight on potential salt formation in different media. Solution NMR spectroscopy appears to be a useful tool to evaluate counter ion and solvent selection for salt formation reaction.

Evaluation of solvent effects on drug release from injectable phase sensitive liquid implant systems

Bu çalışmanın amacı, in situ oluşan enjektabl implantlardan granisetron hidroklorür salımına çözücü türünün etkilerinin incelenmesidir. Formülasyonlar ağırlıkça %32 poli(DL-laktid-ko-glikolid) 50:50 (Resomer RG 502), %64 çözücü ve 4% etkin madde içermektedir. Kullanılan çözücüler, azalan hidrofillik sırasına göre dimetilsülfoksit (DMSO), N-metil-2-pirolidon (NMP), tetraglikol (TG), propilen karbonat (PC), triasetin (TA) ve benzyl benzoat (BB)`tır. Formülasyonların 20G iğnelerden enjekte edilebilirliği saptandıktan sonra, in vitro çözünme hızı testi su banyosunda (30 dev/dak) yürütülmüş ve numuneler spektrofotometrik olarak analiz edilmiştir. Etkin madde salım profilleri, başlangıç doz boşalmasının hidrofobik çözücülerin kullanılmasıyla BB>TA>PC sıralamasında azaldığını ve hidrofilik çözücülerin kullanılmasıyla DMSO>NMP>TG sıralamasında arttığını göstermiştir. Takip eden salımda birinci haftada, DMSO doz boşalmasına (99.1%) neden olurken, BB ve TA çok yavaş salıma neden olmuştur. BB ve TA üç haftada üç-fazlı profiller göstermiştir. NMP ve TG, DMSO ve PC arasında yer alan benzer profiller vermiştir. PC, birinci günde %25`ten sonra nispeten düzenli salım vermiştir. Salım kinetikleri çoğunlukla Higuchi kinetik modeline uymuştur. Sonuçlar faz duyarlı polimerlerin, orta hidrofobluktaki çözücüler ile kombinasyonlarının enjektabl implant sistemlerden 21 gün boyunca etkin madde salımının düzenlenmesinde yararlı olabileceğini göstermiştir

Quantitative analysis of bilobalide and ginkgolides from Ginkgo biloba leaves and Ginkgo products using (1)H-NMR.

1H-NMR spectrometry was applied to the quantitative analysis of the bilobalide, ginkgolides A, B, and C in Ginkgo biloba leaves and six kinds of commercial Ginkgo products without any chromatographic purification. The experiment was performed by the analysis of each singlet H-12, which were well separated in the range of delta 6.0-7.0 in the (1)H-NMR spectrum. However, the H-12 protons of bilobalide and ginkgolides may have overlapped with H-6 or H-8 protons of the Ginkgo flavonoids. Therefore, the optimum (1)H-NMR solvent for the analysis of the compound was selected through the evaluation of solvent effects on the resolution of these signals from the compounds. Acetone-d(6)-benzene-d(6) (50 : 50) was found to be the best one among the solvents evaluated. The quantity of the compounds was calculated by the relative ratio of the intensity of each compound to the known amount of internal standard (25 microgram), phloroglucinol. This method allows rapid and simple quantitation of underivatized bilobalide and ginkgolides in 5 min without any pre-purification steps.

Evaluation of Solvent Effects in Isotropic and Anisotropic Dielectrics and in Ionic Solutions with a Unified Integral Equation Method: Theoretical Bases, Computational Implementation, and Numerical Applications

We present the full implementation of the integral equation formalism (IEF) we have recently formulated to treat solvent effects. The method exploits a single common approach for dielectrics of very different nature: standard isotropic liquids, intrinsically anisotropic media like liquid crystals, and ionic solutions. We report here an analysis of its both formal and technical details as well as some numerical applications addressed to state the achieved generalization to all kinds of molecular solutes and to show the equally reliable performances in treating such different environmental systems. In particular, we report, for isotropic liquids, data of solvation free energies and static (hyper)polarizabilities of various molecular solutes in water, for anisotropic dielectrics, a study of an SN2 reaction, and finally, for ionic solution, a study of some structural aspects of ion pairing.

Charge transfer spectra of organometallic complexes—IX. Evaluation of solvent effects on the electron donor—acceptor interactions between trimethyltinisothiocyanate and iodine

Abstract Charge transfer energies of trimethyltinisothiocyanate—iodine complexes in solution are found to depend on the nature of the solvent. The relationship of these solvent shifts with various solvent properties, and is discussed. Stabilization energies of the excited states in the different solvents are determined using the Onsager theory of dielectrics.

Evaluation of solvent effects on the dissociation of aliphatic carboxylic acids in aqueousN,N-dimethylformamide mixtures according to the scaled particle theory

The standard Gibbs energies of transfer, ΔGt° from water to water–N,N-dimethylformamide mixtures for the dissociation process of several organic acids (formic, acetic, propionic, n-butyric, isobutyric, n-valeric, isovaleric, 2-methylbutyric and trimethylacetic acids) obtained from the pKa* values are discussed in terms of the extended Scaled Particle Theory from quantum mechanical calculations in order to estimate the cavity and electrostatic contributions. The residual energy term was correlated with the hydrogen bond acceptor density and the Kamlet–Taft β parameters. The main contribution to ΔGt° was due to dipolar and specific interactions.

Homolytic Substitution in Trialkyltin Iodides by Photochemically Generated Iodine Atoms. IV. Evaluation of Solvent Effects on the Electron Donor Acceptor Complexes and the Reactivity of Alkylmetals

AbstractThe spectrophotometric properties of the trialkyltiniodide‐iodine charge transfer complexes in solution are found to depend on the nature of the solvent. The correlations of these solvent shifts of the absorption bands with various solvent properties are discussed within the frame of the Onsager model of dielectrics. Thus data like dipole moments and stabilization energies of excited states can be obtained.Furthermore a kinetic study of the reactivity of three trialkyltin iodides with iodine atoms has been made in different solvents. The correlation between the absolute rate constants and the polarity (dielectric constant) of the medium suggests increasing solvation of the activated complex with increasing bulkyness of the alkylsubstituent.The solvent free energy of the initial reactant, the excited CT complex, could be calculated from two independently obtained differences of free energies, i.e. the solvent free energy Esolvent going from the standard solvent to the actual solvents and δΔGsolv,x≠' determined from kinetic experiments at different temperatures.

Viscosimetric evaluation of solvent effects

The intrinsic viscosities of methylene blue, glucose and dextran were determined in various solvents. They are linear againstY Winstein-Grunwald solvent parameters. The relation observed offers an alternative route of the evaluation of the solvent effects by means of viscosimetric measurements.

Evaluation of solvent effects in electronic spectra

Applicability of the Buckingham cross-term f(D,n2) = (D -1) (n2 - 1)/(2D + 1) (2n2 + 1) for evaluation of solvent shifts has been tested using 12 original and 4 published data sets concerning solvent effects in electronic spectra. The results are compared with correlation of the same data with the Bakshiev equation. Influence of the cross-term on the solvent shifts is dominant with the systems showing no direction change of the molecular dipole moment during excitation. Mutual dependence has been found between the cross-term and the Taft solvent factors π at the 90% significance level.