ESR Evidence for Proton Tunneling from a Positive Hole through Intermolecular Hydrogen Bond in Irradiated Single Crystals of Carboxylic Acids

Publisher Website
Google Scholar
Abstract
It has been found that an irradiated single crystal of potassium hydrogen fumarate-d2 (K+−OOC–CD=CD–COOH) gives two kinds of carboxyl radical, OOC–CD=CD–COO−· [Oσ(I)] and · OOC–CD=CD–COOH[Oσ(II)]. Evidence has been obtained for Oσ(I) being formed from the positive hole at the COOH end by proton tunneling to the neighboring COO− group through the intermolecular hydrogen bond. The dipolar tensor calculated for the transferred proton agrees well with the observed tensor in both the principal values and directions. Oσ(II) formed by loss of an electron from the COO− group gives the hyperfine coupling to the proton which belongs to the neighboring COOH group. Agreement between the observed and calculated dipolar tensors is also fairly good.