The Conformational Behaviour of Fluorinated Tetrahydrothiopyran.

We present a comprehensive study on the conformational behavior of diversely substituted 4-fluorotetrahydrothiopyran derivatives. Through quantum chemical simulations including DFT as well as NBO and NPA analysis, we elucidate the pivotal role of electrostatic interactions, occasionally complemented by hyperconjugative interactions, in stabilizing axial fluorine conformers. Less polar conformers were occasionally obtained, attributed to the interplay of electrostatic and hyperconjugative interactions.

From medium to endoplasmic reticulum: Tracing anticancer phenolato titanium(IV) complex by F NMR detection.

Titanium(IV) complexes of diaminobis(phenolato)-bis(alkoxo) ligands are promising anticancer drugs, showing marked in-vivo efficacy with no toxic side-effects in mice, hence, it is of interest to elucidate their mechanism of action. Herein, we employed a fluoro-substituted derivative, FenolaTi, for mechanistic analysis of the active species and its cellular target by quantitative F NMR detection to reveal its biodistribution and reactivity in extracellular and intracellular matrices. Upon administration to the serum-containing medium, FenolaTi interacted with bovine serum albumin.

Thallium chemical shift referencing.

Thallium chemical shifts are very sensitive to chemical and physical conditions. This makes accurate chemical shift referencing difficult. Therefore, chemical shifts are usually referenced to the H reference multiplied by a standard factor.

Magnetic susceptibility measurement by NMR: 1. The temperature dependence of TMS.

Usually a dedicated susceptometer is needed to measure diamagnetism accurately. An NMR spectrometer is more readily available in most chemistry departments but till now has been inaccurate for measuring diamagnetism. An improved NMR method is introduced to measure the magnetic susceptibility, or diamagnetism with similar absolute accuracy as other methods.

Cavitation energies can outperform dispersion interactions.

The accurate dissection of binding energies into their microscopic components is challenging, especially in solution. Here we study the binding of noble gases (He-Xe) with the macrocyclic receptor cucurbit[5]uril in water by displacement of methane and ethane as H NMR probes. We dissect the hydration free energies of the noble gases into an attractive dispersive component and a repulsive one for formation of a cavity in water.

Docosahexaenoic acid triglyceride-based microemulsions with an added dendrimer - Structural considerations.

Omega fatty acids, mainly the triglyceride of docosahexaenoic acid (TG-DHA), are considered important nutraceuticals. These compounds are water-insoluble and their transport across membranes depends on their carriers. Dendrimers are known as drug carriers across cell membranes and also as permeation enhancers.

High accuracy NMR chemical shift corrected for bulk magnetization as a tool for structural elucidation of microemulsions. Part 2 - Anionic and nonionic dilutable microemulsions.

In our previous report we suggested a new analytical tool, high accuracy NMR chemical shift corrected for bulk magnetization as a supplementary tool to study structural transitions and droplet size and shape of dilutable microemulsions. The aim of this study was to show the generality of this technique and to demonstrate that in almost any type of microemulsion this technique provides additional valuable structural information. The analysis made by the technique adds to the elucidation of some structural aspects that could not be clearly determined by other classical techniques.

High accuracy NMR chemical shift corrected for bulk magnetization as a tool for structural elucidation of dilutable microemulsions. Part 1 - Proof of concept.

In microemulsions, changes in droplet size and shape and possible transformations occur under various conditions. They are difficult to characterize by most analytical tools because of their nano-sized structure and dynamic nature. Several methods are usually combined to obtain reliable information, guiding the scientist in understanding their physical behavior.

New insights into the microemulsion-based chromatographic NMR resolution mechanism and its application to fragrance/flavor molecules.

The NMR chromatography method is applied to a class of molecules with similar physical properties. We correlate the separation ability of microemulsions to the physical properties of the analyzed molecules. Flavor and aroma compounds are very widespread.

NMR chromatography using microemulsion systems.

NMR spectroscopy is an excellent tool for structural analysis of pure compounds. However, for mixtures, it performs poorly because of overlapping signals. Diffusion ordered NMR spectroscopy (DOSY) can be used to separate the spectra of compounds with widely differing molecular weights, but the separation is usually insufficient.

NMR spectroscopic study of the Murex trunculus dyeing process.

It is widely accepted that indigo dyes derived from Murex trunculus were used to produce the biblical dyes tekhelet and argaman. We describe a method of following the debromination of natural leucoindigos and their binding to wool using NMR spectroscopy. Debromination is observed prior to reaction with the wool and prior to oxidation.

High-resolution NMR "chromatography" using a liquids spectrometer.

NMR spectroscopy is an excellent tool for the structural analysis of pure compounds. However, for mixtures it performs poorly because of overlapping signals. Diffusion can be used to separate compounds of widely differing molecular weight but the amount of separation is usually insufficient.

Effect of sodium diclofenac loads on mesophase components and structure.

We studied the effect of a model electrolytic drug on intermolecular interactions, conformational changes, and phase transitions in structured discontinuous cubic QL lyotropic liquid crystals. These changes were due to competition with hydration of the lipid headgroups. Structural changes of the phase induced by solubilization loads of sodium diclofenac (Na-DFC) were investigated by directly observing the water, ethanol, and Na-DFC components of the resulting phases using 2H and 23Na NMR.

Further conventions for NMR shielding and chemical shifts (IUPAC Recommendations 2008).

IUPAC has published a number of recommendations regarding the reporting of nuclear magnetic resonance (NMR) data, especially chemical shifts. The most recent publication [Pure Appl. Chem.

Further conventions for NMR shielding and chemical shifts IUPAC recommendations 2008.

IUPAC has published a number of recommendations regarding the reporting of nuclear magnetic resonance (NMR) data, especially chemical shifts. The most recent publication [Pure Appl. Chem.

Standardization of chemical shifts of TMS and solvent signals in NMR solvents.

The standard for chemical shift is dilute tetramethylsilane (TMS) in CDCl3, but many measurements are made relative to TMS in other solvents, the proton resonance of the solvent peak or relative to the lock frequency. Here, the chemical shifts of TMS and the proton and deuterium chemical shifts of the solvent signals of several solvents are measured over a wide temperature range. This allows for the use of TMS or the solvent and lock signal as a secondary reference for other NMR signals, as compared with dilute TMS in CDCl3 at a chosen temperature; 25 degrees C is chosen here.

Measurement of magnetic susceptibility and calculation of shape factor of NMR samples.

A method for accurate measurement of magnetic susceptibility and determination of the shape factor in an NMR tube is shown. The combination of accurate shape factor determination with susceptibility measurement leads to improved accuracy when measuring chemical shift. This is important for comparing samples in different solvents or under different conditions, such as temperature, solvent, and pH.

Temperature dependence of the 1H chemical shift of tetramethylsilane in chloroform, methanol, and dimethylsulfoxide.

The chemical shift of tetramethylsilane (TMS) is usually taken to be zero. However, it does vary slightly with temperature, having obvious implications for studies of temperature effects on chemical shifts. In this work, we measure the variation in the chemical shift of TMS with temperature in three solvents, CDCl3, CD3OD, and DMSO-d6, relative to the resonant frequency of 3He gas, which can be reasonably assumed to be temperature independent.

Ball-and-socket stacking of supercharged geodesic polyarenes: bonding by interstitial lithium ions.

Unprecedented supramolecular stacks of highly reduced geodesic pi-systems were prepared by the reduction of the derivatized fullerenes Me(5)C(60)H and Ph(5)C(60)H and corannulene with lithium metal (R(5)C(60)(5)(-)/Cor(4)(-)/9Li(+)). The host--guest assemblies form because of the enhanced electrostatic interactions between the lithium cations and the anionic moieties, in addition to the structural compatibility between the curved hydrocarbons. The high stability of these new supramolecular assemblies (heterodimers) enables the introduction of another organization motif to the system.

Variations on the chemical shift of TMS.

The chemical shift of TMS is commonly assumed to be zero. However, it varies by over 1 ppm for 1H and 4 ppm for 13C and shows a correlation with the physical properties of the solvent. Using the commonly accepted convention that TMS always resonates at zero leads to significant errors when comparing chemical shifts in different solvents.

Stereodynamics and characterization of the hexa(4-n-dodecylbiphenylyl)benzene hexaanion that includes a twisted benzene core.

Hexa(4-n-dodecylbiphenylyl)benzene (HDBB) was reduced by a series of alkali metals in THF under high vacuum. Three reduction states were identified by NMR spectroscopy, namely the dianion, tetraanion and hexaanion. The NMR spectra of HDBB(6-) revealed a remarkable distortion of symmetry, which is interpreted by adoption of a twisted conformation of the central benzene ring and a slow rotation of the inner phenylene rings of the biphenyl units.

Self-diffusion nuclear magnetic resonance, microstructure transitions, and solubilization capacity of phytosterols and cholesterol in Winsor IV food-grade microemulsions.

Microemulsions are of growing interest to the food industry as vehicles for delivering and enhancing solubilization of natural food supplements with nutritional and health benefits. The incorporation of molecular phytosterols, cholesterol-lowering agents, in food products is of great interest to the food industry. In this work is demonstrated the use of water dilutable food-grade microemulsions consisting of ethoxylated sorbitan ester (Tween 60), water, R-(+)-limonene, ethanol, and propylene glycol as vehicles for enhancing the phytosterols solubilization.

Food-grade microemulsions based on nonionic emulsifiers: media to enhance lycopene solubilization.

Water-dilutable food-grade microemulsions consisting of ethoxylated sorbitan esters, and in some cases blended with other emulsifiers, water, (R)-(+)-limonene, ethanol, and propylene glycol, have been prepared. These microemulsions are of growing interest to the food industry as vehicles for delivering and enhancing solubilization of natural food supplements with nutritional and health benefits. Lycopene, an active natural lipophilic antioxidant from tomato, has solubilized in water-in-oil, bicontinuous, and oil-in-water types of microemulsions up to 10 times the oil [(R)-(+)-limonene] dissolution capacity.

Two helium atoms inside fullerenes: probing the internal magnetic field in C60(6-) and C70(6-).

A 3He NMR resonance of C606- containing He is assigned to He2@C606-, thus showing that C60 can also accommodate two helium atoms. The ratio of the di-helium compound relative to the mono- is 1:200, 10 times lower than the equivalent counterpart of C70. The 3He NMR chemical shift of He2@C606- is 0.