Use our NMR service that provides 77Se NMR and many other
77Selenium (77Se) is a low sensitivity spin ½ nucleus that yields narrow lines over a very
wide chemical shift range. Each type of selenium compound has its characteristic
chemical shift range (fig. 1).
Fig. 1. Chemical shift ranges for selenium NMR
Selenium NMR (fig. 2) is used extensively in the study of organoselenium compounds such as selenoxanthenone (fig.
3) and for studies of selenium binding to proteins.
Fig. 2. Proton decoupled 77Se-NMR spectrum of selenoxanthenone (0.1 M) in
Fig. 3. Molecular structure of selenoxanthenone
Selenium often shows couplings to other nuclei,
31P, etc. It also displays homonuclear couplings with three-bond
selenium-selenium couplings between 10 and 100 Hz that depend on stereochemistry. Selenium couplings to protons can
be removed by decoupling as in fig. 2. The coupled spectrum of selenoxanthenone (fig. 4) shows a three bond
coupling to H1 (3JSe,H) of 11.6 Hz, four bond coupling to H2
(4JSe,H) of 2.2 Hz and five bond to H3 (5JSe,H) of 1.2 Hz.
A six bond coupling was not observed although it is expected to be about 0.5 Hz.
Fig. 4. 77Se-NMR spectrum of selenoxanthenone (0.1 M) in
CDCl3 showing proton coupling
The selenium couplings are also observed as satellites in the proton spectrum (fig. 5). They only appear as
satellites because the abundance of 77Se is only 7.63%.
Fig. 5. 1H-NMR spectrum of selenoxanthenone (0.1 M) in
CDCl3 showing 77Se coupling
13C coupling is manifested as small satellite signals in the 77Se spectrum (fig. 6). Here
couplings up to three bonds are observed. One bond coupling constants are in the region of 100 Hz, 2 and 3 bond
couplings range from 5 to 35 Hz and longer range couplings are less than 3 Hz.
Fig. 6. Proton decoupled 77Se-NMR spectrum of selenoxanthenone
(0.1 M) in CDCl3 showing satellites arising from 13C coupling
Selenium carbon coupling is also seen as satellite signals in the 13C-NMR
spectrum (fig. 7).
Fig. 7. Proton decoupled 13C-NMR spectrum of selenoxanthenone
(0.1 M) in CDCl3 showing satellites arising from 77Se coupling
Properties of 77Se
(Click here for explanation)
|Chemical shift range||3000 ppm, from -1000 to 2000|
|Frequency ratio (Ξ)||19.071513%|
|Linewidth of reference||~0.5 Hz|
|T1 of reference||~30 s|
|Receptivity rel. to 1H at natural abundance||5.37 × 10-4|
|Receptivity rel. to 1H when enriched||7.04 × 10-3|
|Receptivity rel. to 13C at natural abundance||3.15|
|Receptivity rel. to 13C when enriched||41.3|
Some of the materials mentioned here are very dangerous. Ask a qualified
chemist for advice before handling them. Qualified chemists should check the relevant safety literature
before handling or giving advice about unfamiliar substances. NMR solvents are toxic and most are
flammable. Specifically, selenium compounds are toxic or very toxic, work in a hood and use appropriate gloves and
protective clothing. Latex gloves are insufficient protection against organoselenium compounds.
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