Dimerized p-Semiquinone Radical Anions Stabilized by a Pair of Rare-Earth Metal Ions

Here we report stable p -quinone-radical-bridged rare-earth complexes involving the ligand tetramethylquinone (QMe 4 •- ). The complexes, {Y[(QMe 4 ) •- Cl 2 (THF) 3 ]} 2 ( 1 ) and {Gd[(QMe 4 ) •- Cl 2 (THF) 3 ]} 2 ( 2 ), where THF = tetrahydrofuran, are sufficiently stable that we can measure the single-crystal structures and perform magnetic and electron paramagnetic resonance measurements. These studies show the presence of a semiquinone form and that the magnetic interaction between the radicals in the dimer is strong and antiferromagnetic.