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A CW‐EPR, ENDOR and special TRIPLE resonance study of a novel magnesium ketyl radical
Author(s) -
Murphy Damien M.,
McDyre Lucia E.,
Carter Emma,
Stasch Andreas,
Jones Cameron
Publication year - 2011
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.2721
Subject(s) - ketyl , chemistry , electron paramagnetic resonance , benzophenone , hyperfine structure , magnesium , resonance (particle physics) , radical , nuclear magnetic resonance , crystallography , photochemistry , atomic physics , organic chemistry , physics
In this paper, the paramagnetic properties of a novel magnesium ketyl radical (compound 1), formed by reduction of benzophenone with a dimeric Mg(I) complex in the presence of dimethylaminopyridine, are described. Using CW EPR, ENDOR and special TRIPLE resonance, the spin distribution in the radical has been explored at variable temperatures (200–298 K). At 298 K, most of the unpaired spin is found to be confined to the (OCPh 2 • ) fragment based on the hyperfine couplings (hfc's) of o ‐H = 8.30, m ‐H = 3.00 and p ‐H = 9.95 MHz. Smaller hfc's to 25 Mg (5.54 MHz) and 14 N DMAP (0.90 MHz) were also evidenced in the 298 K EPR spectrum, indicating some spin delocalisation onto the Mg(Nacnac)(DMAP) fragment. At lower temperatures, restricted rotations of the diphenyl rings create an inequivalent spin distribution in the two rings, with o 1 ‐H = 8.80, o 2 ‐H = 7.85, m ‐H = 3.00 and p ‐H = 10.00 MHz. Copyright © 2011 John Wiley & Sons, Ltd.