Novel high-spin states in reduced dibenzoylbenzenes

While intermolecular spin-spin coupling most often is of antiferromagnetic nature, high-spin formation of metal-bridged monoketyl radicals has been known since the early 1960ʹs, but has not been used for creating higher spin multiplicities. We have succeeded in establishing high-spin formation in extended ketones upon metal reduction. In the known m-phenylene diketones novel quartet (S = 32) and quintet (S = 2) ground-state radicals could be identified and these can only arise from spin coupled dimers. The counter metal ion ligation is that strong that spin pairing and the formation of quinoid structures can even be overcome in the doubly charged p-phenylene diketones.