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Inne
Toward an understanding of the ambiguous electron paramagnetic resonance spectra of the iminoxy radical from o-fluorobenzaldehyde oxime: density functional theory and ab initio studies.
Autorzy
Rok wydania
2015
Czasopismo
Journal of Physical Chemistry A
Numer woluminu
119
Strony
9109-9120
DOI
10.1021/acs.jpca.5b06143
Kolekcja
Język
Angielski
Typ publikacji
Artykuł
Iminoxy radicals (R1R2C═N—O•) possess an inherent ability to exist as E and Z isomers. Although isotropic hyperfine couplings for the species with R1 = H allow one to distinguish between E and Z, unequivocal assignment of the parameters observed in the EPR spectra of the radicals without the hydrogen atom at the azomethine carbon to the right isomer is not a simple task. The iminoxyl derived from o-fluoroacetophenone oxime (R1 = CH3 and R2 = o-FC6H5) appears to be a case in point. Moreover, for its two isomers the rotation of the o-FC6H5 group brings into existence the syn and anti conformers, depending on the mutual orientation of the F atom and C═N—O• group, making a description of hyperfine couplings to structure even more challenging. To accomplish this, a vast array of theoretical methods (DFT, OO-SCS-MP2, QCISD) was used to calculate the isotropic hyperfine couplings. The comparison between experimental and theoretical values revealed that the E isomer is the dominant radical form, for which a fast interconversion between anti and syn conformers is expected. In addition, the origin of the significant AF increase with solvent polarity was analyzed.
Adres publiczny
http://dx.doi.org/10.1021/acs.jpca.5b06143