A Redox-Active Dinuclear Platinum Complex Exhibiting Multicolored Electrochromism and Luminescence

A redox series of cyclometalated platinum complexes based on a dinuclear motif linked by acetamidato (aam) bridging ligands, [Pt-2(mu-aam)(2)(ppy)(2)] (ppy(-) = 2-phenylpyridinate ion), has been synthesized. The complexes in this series are easily oxidized and reduced by both electrochemical and chemical methods, and this is accompanied by multistep changes in their optical properties, that is, multiple color changes and luminescence. Isolation of the complexes and the structural determination of three oxidation states, +2, +2.33, and +3, have been achieved. The mixed-valent complex, with an average oxidation state of +2.33, forms a trimer based on the dinuclear motif. The mixed-valent complex has a characteristic color owing to intervalence transitions in the platinum chain. In contrast, the divalent complex exhibits strong red phosphorescence originating from a triplet metal-metal-toligand charge transfer ((MMLCT)-M-3) state. This study demonstrates the unique chromic behavior of a redox-active and luminescent platinum complex.