Sulfur, Selenium, and Tellurium NMR

Duddeck, H.

doi:10.1002/9780470034590.emrstm0543

Cited by 9 publications

(13 citation statements)

References 115 publications

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“…If one compares to previously published results, the chemical shift for a selenium atom only surrounded by selenium atoms in the middle of a chain of length larger than five is found at 864 ppm, very close to previously measured values for glassy selenium at 865 ppm. 21,38 Adding one arsenic atom as second neighbor will lower the chemical shift by 34 ppm, leading to chemical shifts of 830 and 796 ppm for selenium with one and two arsenic as second neighbors. The width at half-maximum of the a, 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 b and c Gaussian peaks was found to be 179 ppm, lower than the previously measured values which were probably affected by the presence of spinning sidebands.…”

Section: Resultsmentioning

confidence: 98%

“…20 However, as the 77 Se atoms are excessively sensitive to their environments, it is often observed that the chemical shifts of these broad lines vary with the composition of the sample, 20 precluding any simultaneous fitting of series of NMR spectra. Such an effect results from a dependence of the chemical shift with the nature of the second neighbors as was observed in 29 Si NMR studies of silicate glasses for example. 30,31 In the present study, we recorded quantitative natural abundance 77 Se NMR spectra of a series of five chalcogenide glasses with targeted compositions As 2 Se 3 , AsSe 2 , AsSe 3 , AsSe 4.5 and AsSe 6 and fitted them with a 6 components model (shown in Figure 1 and detailed in Table 1) to take into account, for the first time, the nature of the second neighbors, while limiting the number of assumptions in the fitting procedure.…”

Section: Introductionmentioning

confidence: 87%

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Structure of Arsenic Selenide Glasses Studied by NMR: Selenium Chain Length Distributions and the Flory Model

et al. 2015

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International audienceFive homogeneous arsenic selenide glasses with target compositions As 2 Se 3 , AsSe 2 , AsSe 3 , AsSe 4.5 , and AsSe 6 were studied quantitatively by 77 Se Carr−Purcell−Meiboom−Gill magic-angle spinning NMR and transmission electron microscopy−energy-dispersive X-ray spectroscopy. The entire set of NMR spectra is simultaneously fitted with six distinct environments taking into account the effect of first and second neighbors on the position of the 77 Se resonance. The selenium chains are bound at each end to trivalent arsenic atoms, and the chain length distribution can be modeled with the Flory theory, which is well-known in polymer science and is used here for the first time to model the probability of finding each selenium environment in a selenide glass. No arsenic homopolar bond is detected in our experiments. ■ INTRODUCTION Chalcogenide glasses exhibit a wide range of physical properties such as infrared transparency, high refractive indices, and reversible amorphous-to-crystal transitions and can be easily shaped into optical devices. 1−6 Among them, the arsenic selenide glasses As x Se 1−x are considered to be a promising family because glassy As 2 Se 3 is a good candidate for all-optical switching 7 or for use as a mid-infrared laser source; 8 in addition, arsenic selenide glasses can be used for optic fibers. 9 Recent studies also investigated the possibility of preparing these glasses using microwave heating. 10 Numerous attempts were made to draw a link between the changes in the physical properties of arsenic selenide and the evolution of its molecular structure as the arsenic content varies, both at room temperature 11,12 and when the temperature is increased, 13 during aging of the glass, 14 or when irradiated with a laser. 15 To gain some insight into the arsenic selenide glass structures, recent studies relied on molecular dynamics 16−18 combined with anomalous X-ray scattering 19 or 77 Se solid-state NMR 20−23 to characterize the environments and connectivity of selenium and arsenic atoms. Many of these studies hint toward the existence of a small amount of As−As homopolar bond 12,16 with tetravalent arsenic atoms linked to two arsenic and two selenium atoms. 19 Moreover, 77 Se NMR spectroscopy can quantify three distinct selenium environments (selenium atoms linked to two, one, or zero arsenic atoms) and shows that there is some disorder in the distribution of the lengths of the selenium chains that link arsenic atoms together, as opposed to what is inferred in the chain-crossing model (i.e., when the selenium chains are of similar lengths). 20,23 Interestingly, it was suggested that the Flory model, 24 which describes the distribution of chain lengths in organic polymers, could be applied to inorganic polymers (mostly silicates) because the underlying chemical phenomena share striking similarities, especially for glasses with covalent bonds and no ionic species. 25−27 The Flory theory provides a very simple model for the probability, P(n), of finding a chain of length n, ...

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Section: Resultsmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 87%

Structure of Arsenic Selenide Glasses Studied by NMR: Selenium Chain Length Distributions and the Flory Model

et al. 2015

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“…These results exalt the advantages of multinuclear NMR spectroscopy because of the substantial ∆ δ RS values and no overlapping of the signals. 77 Se and 125 Te NMR have great potential due to the characteristics of selenium and tellurium nuclei, such as a wide spectral window, I = ½, reasonably high natural abundance, and no significant nuclear Overhauser effect (nOe) . These great features can be witnessed by observing the 125 Te‐{ 1 H} NMR spectra of Naproxen ester formed from chalcogen containing secondary alcohol 1h (Figure ).…”

Section: Resultsmentioning

confidence: 99%

NMR chiral discrimination of chalcogen containing secondary alcohols

et al. 2018

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Here, we report the general strategies by which NMR spectroscopy can be used to determine the enantiopurity and absolute configuration of chalcogen containing secondary alcohols, including the evaluation of the use of chiral solvating and chiral derivatizing agents. The BINOL/DMAP ternary complex demonstrated a simple and fast protocol for determining enantiopurity. The drug Naproxen afforded a stable, nonhygroscopic, and readily available chiral derivatizing agent (CDA) for NMR chiral discrimination of chalcogen containing secondary alcohols. The chiral recognition by CDA and chiral solvating agent (CSA) was assessed using 1H, 77Se‐{1H}, and 125Te‐{1H} NMR spectroscopy. A simple model for the assignment of the absolute configuration from NMR data is presented.

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“…Finally, evaluating the 77 Se-{ 1 H} NMR analysis a new signal arisen at 1430.0 ppm, probably related to the Se-F bonding formation. 21,31 When the 19 F NMR experiment was performed employing 0.075 mmol of 2a with 0.075 mmol of SelectFluor®, similarly to the reaction conditions, a signal at À46.5 ppm was detected. But, the 77 Se-{ 1 H} NMR experiment did not show new peak, only regarding to the diphenyl diselenide compound.…”

Section: Entry 4)mentioning

confidence: 99%

Synthesis of 3-selanylbenzo[b]furans promoted by SelectFluor®

et al. 2020

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A simple and practical protocol for the synthesis of 3-selanyl-benzo[b]furans mediated by the SelectFluor® reagent was developed. This novel methodology provided a greener alternative to generate 3-substitutedbenzo[b]furans via a metal-free procedure under mild conditions. The intramolecular cyclization reaction was carried out employing an electrophilic selenium species generated in situ through the reaction between SelectFluor® and organic diselenides. The formation of this electrophilic selenium species (RSe-F) was confirmed by heteronuclear NMR spectroscopy, and its reactivity was explored. Scheme 2 Substrate scope for the synthesis of 3-organylselanylbenzo[b]furans 3a-k. Scheme 3 Chalcogenide scope for the synthesis of 3-chalcogenylbenzo[b]furans 3l-m.This journal is Scheme 7 Plausible mechanism routes for the synthesis of 3-organylselanyl-benzo[b]furans 3.This journal is

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Sulfur, Selenium, and Tellurium NMR

Cited by 9 publications

References 115 publications

Structure of Arsenic Selenide Glasses Studied by NMR: Selenium Chain Length Distributions and the Flory Model

Structure of Arsenic Selenide Glasses Studied by NMR: Selenium Chain Length Distributions and the Flory Model

NMR chiral discrimination of chalcogen containing secondary alcohols

Synthesis of 3-selanylbenzo[b]furans promoted by SelectFluor®

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