Free radicals in an adamantane matrix. XIII. Electron paramagnetic resonance study of sigma* -. pi. * orbital crossover in fluorinated pyridine anions. [X radiation]
Pentafluoropyridine,2,3,4,6-tetrafluoropyridine, 2,6-difluoropyridine, and 2-fluoropyridine anion radicals were produced by x irradiation of an adamantane matrix which was doubly doped with the aromatic precursors and Me/sub 3/NBH/sub 3/ and their EPR spectra obtained. The large fluorine hyperfine splitting constants (hfsc) of penta- and 2,3,4,6-tetrafluoropyridine anions and the small fluorine hfsc's of 2,6-di- and 2-fluoropyridine anions suggest that the former two are sigma radicals while the latter two are ..pi.. radicals. The sigma*-..pi..* orbital crossover phenomenon observed in these fluorinated pyridine anions is explained in terms of the combined effects of stabilization of sigma* orbitals and destabilization of ..pi..* orbitals. The EPR results show that nitrogen has a negligible contribution to the unpaired electron sigma* orbitals. INDO calculations were performed for the various states and the results compared with experiment.
- Research Organization:
- Univ. of Connecticut, Storrs
- OSTI ID:
- 7303489
- Journal Information:
- J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 99:13; ISSN JACSA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
400301* -- Organic Chemistry-- Chemical & Physicochemical Properties-- (-1987)
400600 -- Radiation Chemistry
ADAMANTANE
ALKANES
AZINES
BORANE
BORANES
BORON COMPOUNDS
CHEMICAL RADIATION EFFECTS
CHEMICAL REACTIONS
CHEMISTRY
CYCLOALKANES
DECOMPOSITION
ELECTROMAGNETIC RADIATION
ELECTRON SPIN RESONANCE
ELECTRONIC STRUCTURE
HETEROCYCLIC COMPOUNDS
HYDROCARBONS
IONIZING RADIATIONS
MAGNETIC RESONANCE
MATRIX ELEMENTS
ORGANIC COMPOUNDS
ORGANIC FLUORINE COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PYRIDINES
RADIATION CHEMISTRY
RADIATION EFFECTS
RADIATIONS
RADICALS
RADIOLYSIS
RESONANCE
X RADIATION