The Indigo Isomer Epindolidione as a Redox‐Active Bridging Ligand for Diruthenium Complexes

Epindolidione (H2L), a heteroatom-modified analogue of tetracene and structural isomer indigo, forms dinuclear complexes with [RuX2]2+, X=bpy (2,2′-bipyridine, [1]2+) or pap (2-phenylazopyridine, [2]2+), in its doubly deprotonated bridging form μ-L2−. The dications compounds meso-[1](ClO4)2 meso-[2](ClO4)2, [X2Ru(μ-L)RuX2](ClO4)2, contain five-membered chelate rings N-C−C-O-RuII π bridged metals at an intramolecular distance 7.19 Å. Stepwise reversible oxidation reduction is mainly ligand centered (oxidation: L2−; reduction: X), as deduced from EPR one-electron oxidized reduced intermediates UV/Vis/NIR spectroelectrochemistry, supported by TD-DFT calculation results. results for [1](ClO4)2 [2](ClO4)2 are qualitatively similar to the ones observed indigo-bridged isomers their six-membered ring structures, confirming suitability both systems molecular electronics applications, low-energy absorptions, multiple electron transfers.