Selenium-77 nuclear magnetic resonance studies. 3. Chemical shifts of ionic, N- and Se-coordinated selenocyanate

Experimental 77Se NMR parameters for 17 selenium-containing compounds have been determined by analysis of 77Se solid-state NMR spectra. These are compared to values obtained from first-principles gauge including projector augmented wave (or GIPAW) calculations performed on geometry-optimized crystal structures. Good agreement is observed between experimental and calculated values across a wide chemical shift range, enabling assignment of the experimental 77Se NMR spectra for compounds containing more than one crystallographically distinct selenium site. Calculations for isolated molecules extracted from the optimized structure reveal that intermolecular interactions have a relatively small effect on isotropic shifts in general, but larger effects on the chemical shift anisotropy are observed for some compounds. Further calculations for a model structure give insight into the effects of local bonding geometry on the 77Se chemical shift in a diselenide linkage. The 77Se chemical shift is found to be highly sensitive to torsional angles that define the geometry of the diselenide linkage, and this leads to an understanding of the origins of the large chemical shift differences observed between chemically equivalent selenium sites for one of the compounds studied in this work.

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“… a All values are quoted in ppm. b Reference . c Reference . d Reference . e This work. f Reference . g Reference . h Reference . i Reference . …”

Section: Resultsmentioning

confidence: 99%

⁷⁷Se Solid-State NMR of Inorganic and Organoselenium Systems: A Combined Experimental and Computational Study

et al. 2011

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“…In DMSO solutions, ionic interactions to the nitrogen atom increase the shielding from −273 ppm for SeCN - to −318 ppm for a zinc complex with SeCN - . Interactions to the selenium end, exemplified by a mercury complex, decrease the shielding to −191 ppm . In contrast to the large shifts observed for the nitrogen and chalcogen nuclei, the 13 C resonances in SCN - and SeCN - are not very sensitive to bonding at either end of these anions …”

Section: Introductionmentioning

confidence: 85%

Solvation of SCN^- and SeCN^- Anions in Hydrogen-Bonding Solvents

1996

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The primary solvation sphere surrounding the thiocyanate or the selenocyanide anion in protic solvents, such as methanol, N-methylformamide and formamide, forms intimate hydrogen bonds with these anions. These interactions perturb the electron density and vibrational modes of these anions and can therefore be studied by NMR and infrared spectroscopies. In neat solutions, these solvents form hydrogen bonds to the nitrogen end along the molecular axis and nonaxially to the π cloud of the C−N bond, although a substantial proportion of the anions is not hydrogen bonded. In nitromethane solutions, the thiocyanate and selenocyanide anions form weak complexes with methanol and the amide solvents (K < 1 M-1), which is an order of magnitude smaller than that of OCN- with the same solvents, determined in our previous investigation of the cyanate anion. The remarkable differences in the solvation of these singly charged anions can be understood by theoretical calculations of their electrostatic potentials.

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“…5. The isotropic 77 Se chemical shift is comparable to that of KSeCN measured in solution (6). The experimental spectra of the selenocyanates were simulated via a non-linear least-square implementation of the method of Herzfeld and Berger (29); the resulting data are summarized in Table 1.…”

Section: Selenium-77 Nmr Spectramentioning

confidence: 90%

“…Carbon-13 and nitrogen-14 or -15 NMR results for selenocyanates have been discussed in several reviews (3,4). The coordination of metal atoms with several selenocyanate anions has been investigated by solution NMR (5,6). An analogous study of the thiocyanate anion in copper(I) complexes was conducted using solid-state 13 C NMR (7).…”

Section: Introductionmentioning

confidence: 99%

Nuclear magnetic shielding tensors for the carbon, nitrogen, and selenium nuclei of selenocyanates - a combined experimental and theoretical approach

Bernard¹,

Eichele²,

Wu³

et al. 2000

Can. J. Chem.

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The principal components of the carbon, nitrogen, and selenium chemical shift (CS) tensors for several solid selenocyanate salts have been determined by NMR measurements on stationary or slow magic-angle-spinning powder samples. Within experimental error, all three CS tensors are axially symmetric, consistent with the expected linear geometry of these anions. The spans (Ω) of the carbon and selenium CS tensors for the selenocyanate anion (SeCN-) are approximately 300 and 800 ppm, respectively, much less than the corresponding values for carbon diselenide (CSe2). This difference is a consequence of the difference in the CS tensor components perpendicular to the C infiniti symmetry axes in these systems. Ab initio calculations show that the orbital symmetries of these compounds are a significant factor in the shielding. For CSe2, efficient mixing of the σ and π orbitals results in a large paramagnetic contribution to the total shielding of the chemical shielding tensor components perpendicular to the molecular axis. Such mixing is less efficient for the SeCN-, resulting in a smaller paramagnetic contribution and hence in greater shielding in directions perpendicular to the molecular axis.Key words: selenocyanates, solid-state NMR, carbon shielding tensors, nitrogen shielding tensors, selenium shielding tensors, ab initio calculations.

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Selenium-77 nuclear magnetic resonance studies. 3. Chemical shifts of ionic, N- and Se-coordinated selenocyanate

Cited by 15 publications

References 15 publications

⁷⁷Se Solid-State NMR of Inorganic and Organoselenium Systems: A Combined Experimental and Computational Study

⁷⁷Se Solid-State NMR of Inorganic and Organoselenium Systems: A Combined Experimental and Computational Study

Solvation of SCN^- and SeCN^- Anions in Hydrogen-Bonding Solvents

Nuclear magnetic shielding tensors for the carbon, nitrogen, and selenium nuclei of selenocyanates - a combined experimental and theoretical approach

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Selenium-77 nuclear magnetic resonance studies. 3. Chemical shifts of ionic, N- and Se-coordinated selenocyanate

Cited by 15 publications

References 15 publications

77Se Solid-State NMR of Inorganic and Organoselenium Systems: A Combined Experimental and Computational Study

77Se Solid-State NMR of Inorganic and Organoselenium Systems: A Combined Experimental and Computational Study

Solvation of SCN- and SeCN- Anions in Hydrogen-Bonding Solvents

Nuclear magnetic shielding tensors for the carbon, nitrogen, and selenium nuclei of selenocyanates - a combined experimental and theoretical approach

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Product

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⁷⁷Se Solid-State NMR of Inorganic and Organoselenium Systems: A Combined Experimental and Computational Study

⁷⁷Se Solid-State NMR of Inorganic and Organoselenium Systems: A Combined Experimental and Computational Study

Solvation of SCN^- and SeCN^- Anions in Hydrogen-Bonding Solvents