INTERMOLECULAR MAGNETIC-INTERACTIONS IN 2,4,6-TRI(TERT-BUTYL)PHENOXY AND 2,6-DI(TERT-BUTYL)-4-TRITYLPHENOXY RADICALS

Variable temperature magnetic susceptibility and electron paramagnetic resonance studies of neat solid-state samples of 2,4,6-tri(tert-butyl )phenoxy radicals (3) and 2,6-di(tert-butyl)-4-tritylphenoxy radicals (4) showed antiferromagnetic coupling in both materials. Spin counts i ndicated appreciable dimerization of radical content in both species ( up to ca. 70%) but the remaining spins in each sample were well descri bed by a model of antiferromagnetically exchange-coupled Heisenberg S= 1/2 dimers. Antiferromagnetic behaviour was more pronounced in 3 than in 4, with exchange constants for these being ca. -7 and -1 K, respect ively. There is evidence for substantial numbers of isolated radical s pin sites in 3 but not in 4, with the Weiss constants for these being -2.4 and -0.85 K, respectively. The changes in behaviour from 3 to 4 a re attributable to changes in the average inter-radical distance, indu ced by the large 4-trityl group in 4.