Dynamic nuclear polarization and overhauser shift on C 60 — Radical anion salts

Abstract

Electronic and magnetic properties of C 60-tetraphenylphosphonium radical anion salts have been studied with the help of magnetic resonance technique. By applying the Overhauser shift method the Dynamic Nuclear Polarization, nuclear spin-lattice relaxation times and Overhauser shift have been determined simultaneously. The very short nuclear spin-lattice relaxation times of 13 C and 1 H are caused mainly by localized electronic moments rather than by the relaxation via conduction electrons. The 13 C NMR signals from “bucky-balls” and phenyl groups of counterions can be separated. The results point to the incomplete charge transfer from the counterion to C 60 molecule resulting in a large Overhauser shift signal from protons and carbon nuclei of the counterion.