Stable Mixed-Valent Radicals from Platinum(II) Complexes of a Bis(dioxolene) Ligand

Three diplatinum(II) complexes [{PtL}2(μ-thea)] (H 4thea=2,3,6,7-tetrahydroxy-9,10-dimethyl-9,10-dihydro-9, 10-ethanoanthracene) have been prepared, with diphosphine or bipyridyl "L" co-ligands. One-electron oxidation of these complexes gave radical cations containing a mixed-valent [thea .]3- ligand with discrete catecholate and semiquinonate centers separated by quaternary methylene spacers. The electronic character of these radicals is near the Robin-Day class II/III border determined by UV/Vis/NIR and EPR spectroscopies. Crystal-structure determinations and a DFT calculation imply that oxidation of the thea 4- ligand may lead to an increased through-space interaction between the dioxolene π systems. Electron hopping: Diplatinum complexes, such as the one shown here, are readily oxidized to mixed-valent catechol/semiquinone radical species, some of which can be crystallized at room temperature. The dioxolene rings in the radical products are moderately strongly coupled by EPR and UV/Vis/NIR spectroscopies, despite being separated by saturated methylene spacers. © 2014 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.