Selenate—An internal chemical shift standard for aqueous ⁷⁷Se NMR spectroscopy

Abstract

The 77 Se NMR spectra of selenate were studied under various circumstances, such as concentration, pH, temperature, ionic strength, and D 2 O:H 2 O ratio, in order to examine its potential as a water-soluble internal chemical shift standard. The performance of selenate as a chemical shift reference and that of other attempted ones from the literature (dimethyl selenide, tetramethylsilane/TMS, and 3-(trimethylsilyl)propane-1-sulfonate/DSS) was also explored. The uncertainty in the resulting chemical shift relative to the effective spectral width is comparable to that of DSS. Compared to the currently prevalent water-soluble external chemical shift reference, selenic acid solution, the properties of internal selenate are much more favorable in terms of ease of use. We have also demonstrated that selenate can be used in reducing media, which is inevitable for the analysis of selenol compounds. Thus, it can be stated that sodium selenate is a robust internal chemical shift reference in aqueous media for 77 Se NMR measurements; the chemical shift of this reference in a solution containing 5 V/V% D 2 O at 25 C and 0.15 molÁdm À3 ionic strength is 1048.65 ppm relative to 60 V/V% dimethyl selenide in CDCl 3 and 1046.40 ppm relative to the 1 H signal of 0.03 V/V% TMS in CDCl 3 .In summary, a water-soluble, selenium-containing internal chemical shift reference compound was introduced for 77 Se NMR measurements for the first time in the literature, and with the aforementioned results all previous 77 Se measurements can be converted to a unified scale defined by the International Union of Pure and Applied Chemistry.

Synthesis and antioxidant activities of N-thiophenyl ebselenamines: a 77Se{1H} NMR mechanistic study

“…77 Se{ 1 H} NMR spectroscopy can be used as a practical tool to follow the redox progress of organoselenium compounds in an easy and direct way. 21 Mechanistic studies of ebselen 1 followed by 77 Se{ 1 H} NMR spectroscopy using thiols such as PhSH or GSH indicated that the Se–N bond is reductively cleaved to form the corresponding selenenyl sulphide intermediate, which further reacted with H 2 O 2 to produce selenol and selenenic acid as highly reactive intermediates. 13 f ,14 Furthermore, it has been demonstrated in phase II for the safety of noise-induced hearing loss and phase III for cerebral ischemia and bipolar disorder diseases.…”

Solvent effect on the 77Se NMR chemical shifts of diphenyl diselenides

“…Furthermore, an accurate and practical referencing protocol must be used to properly assign each signal. 57–59 For the 77 Se NMR spectra, different organic compounds (secondary standards) have been employed, 60 because Me 2 Se 60% v/v (primary standard; δ = 0.0 ppm) is volatile, toxic, and has a very bad smell.…”

“…45–56 Additionally, some 77 Se NMR investigations are performed under different experimental conditions, which could make the assignment of different signals somewhat troublesome because of the effect of the solvent on the chemical shift value. 45–60…”