1H and 14N ENDOR spectra of tert-butylphenylnitroxide

1988 ◽  
Vol 66 (8) ◽  
pp. 1862-1866 ◽  
Author(s):  
Jun Yamauchi ◽  
Yasuo Deguchi
Keyword(s):  
Hyperfine Coupling ◽  
Hyperfine Coupling Constant ◽  
Coupling Constants ◽  
Molecular Orbital Calculations ◽  
Triple Resonance ◽  
Coupling Constant ◽  
Nitroxide Radicals ◽  
Experimental Conditions ◽  
Electron Detection ◽  
Anisotropic Hyperfine

1H and 14N ENDOR spectra of tert-butylphenylnitroxide were observed in ethylbenzene solution. The experimental conditions for detecting optimum 1H and 14N ENDOR lines were quite different. The 1H hyperfine coupling constants and their signs are discussed from the viewpoints of molecular orbital calculations, general triple resonance, CRISP (cross relaxation intensity sequence pattern) method, and steric hindrance. In view of the large anisotropic hyperfine interaction between the nitrogen and the unpaired electron, detection of 14N ENDOR in nitroxide radicals is rather difficult, so that a TM110 mode cavity was utilized in this experiment. The observed 14N hyperfine coupling constant 11.86 G at −80 °C is one of the smallest values observed to date for nitroxide radicals.

scholarly journals Performance of the DLPNO-CCSD and Recent DFT Methods in the Calculation of Isotropic and Dipolar Contributions to 14N Hyperfine Coupling Constants of Nitroxide Radicals

2021 ◽  
Author(s):  
Oleg Gromov
Keyword(s):  
Hyperfine Coupling ◽  
Coupling Constants ◽  
Density Functionals ◽  
Nitroxide Radicals ◽  
Dft Methods ◽  
Absolute Deviation ◽  
Anisotropic Hyperfine ◽  
Ccsd Method ◽  
Vibrational Correction ◽  
Good Agreement

Abstract In the present study, the performance of a set of density functionals: BP86, PBE, OLYP, BEEF, PBEpow, TPSS, SCAN, PBEGXPBE, M06L, MN15L, B3LYP, PBE0, mPW1PW, B97, BHandHLYP, mPW1PW, HSE06, B98, TPSS0, PBE1KCIS, SCAN0, M06, M06-2X, MN15, CAM-B3LYP, ωB97x, B2PLYP, and the B3LYP/N07D and PBE/N07D schemes in the calculation of the 14N anisotropic hyperfine coupling (HFC) constants of a set of 23 nitroxide radicals is evaluated. The results are compared with those obtained with the DLPNO-CCSD method and experimental HFC values. Harmonic contribution to the 14N HFC vibrational correction was calculated at the revPBE0/def2-TZVPP level and included in the evaluation. With the vibrational correction, the DLPNO-CCSD method yielded HFC values in good agreement with the experiment (MAD = 0.3 G for the dipole-dipole contribution and MAD = 0.8 G for the contact coupling contribution). The best DFT results are obtained using the M06 functional with mean absolute deviation (MAD) = 0.2 G for the dipole-dipole contribution and MAD = 0.7 G for the contact coupling contribution. In general, vibrational correction significantly improved most DFT functionals' performance but did not change its overall ranking.

A [3Fe–3S]3+ cluster with exclusively μ-sulfide donors

2016 ◽  
Vol 52 (6) ◽  
pp. 1174-1177 ◽  
Author(s):  
Yousoon Lee ◽  
Ie-Rang Jeon ◽  
Khalil A. Abboud ◽  
Ricardo García-Serres ◽  
Jason Shearer ◽  
...  
Keyword(s):  
Mössbauer Spectroscopy ◽  
Ground State ◽  
Hyperfine Coupling ◽  
Mossbauer Spectroscopy ◽  
Variable Temperature ◽  
Coupling Constants ◽  
Hyperfine Coupling Constants ◽  
Mößbauer Spectroscopy ◽  
Pyramidal Geometry ◽  
Anisotropic Hyperfine

A [3Fe–3(μ-S)]3+ cluster is reported in which each ferric center has a distorted trigonal pyramidal geometry, with an S = 1/2 ground state for the cluster and unusually anisotropic hyperfine coupling constants as determined by variable temperature magnetometry and Mössbauer spectroscopy.

The β-phosphorus hyperfine coupling constant in nitroxides: 6. Solvent effects in non-cyclic nitroxides

2016 ◽  
Vol 14 (15) ◽  
pp. 3729-3743 ◽  
Author(s):  
Gérard Audran ◽  
Lionel Bosco ◽  
Paulin Nkolo ◽  
Raphael Bikanga ◽  
Paul Brémond ◽  
...  
Keyword(s):  
Solvent Effects ◽  
Hyperfine Coupling ◽  
Hyperfine Coupling Constant ◽  
Coupling Constant ◽  
The Impact

The impact of the solvent on aP and aN decreases strikingly upon increasing both the bulkiness and the polarity of the substituents around the nitroxyl moiety.

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