Dinuclear Ruthenium Complex Based on a π‑Extended Bridging Ligand with Redox-Active Tetrathiafulvalene and 1,10-Phenanthroline Units

The synthesis of a π-extended bridging ligand with both redox-active tetrathiafulvalene (TTF) and 1,10-phenanthroline (phen) units, namely, bis­(1,10-phenanthro­[5,6-b])­tetrathiafulvalene (BPTTF), was realized via a self-coupling reaction. Using this ligand and Ru­(tbbpy)₂Cl₂ (tbbpy = 4,4′-di-tert-butyl-2,2′-bipyridine), the dinuclear ruthenium­(II) compound [{Ru­(tbbpy)₂}₂(BPTTF)]­(PF₆)₄ (1) has been obtained by microwave-assisted synthesis. Structural characterization of 1 revealed a crossed arrangement of the TTF moieties on adjacent dimers within the crystal structure. The optical and redox properties of 1 were investigated using electrochemical, spectroelectrochemical, electron paramagnetic resonance (EPR), and absorption spectroscopic studies combined with theoretical calculations. One exhibits a rich electrochemical behavior owing to the multiple redox-active centers. Interestingly, both the ligand BPTTF and the ruthenium compound 1 are EPR-active in the solid state owing to intramolecular charge-transfer processes. The results demonstrate that the TTF-annulated bis­(phen) ligand is a promising bridging ligand to construct oligomeric or polymeric metal complexes with multiple redox-active centers.