Synthesis, mass spectrometry, and spectroscopic properties of a dinuclear ruthenium complex comprising a 20 Å long fully aromatic bridging ligand

The luminescent dinuclear ruthenium complex [(bpy)(2)Ru(bqpy)Ru(bpy)(2)](4+) (1) comprising the 20 Angstrom long fully aromatic bridging ligand bqpy has been synthesized by successive reactions from suitable precursor complexes. Investigations in electrospray mass spectrometry and H-1 NMR spectroscopy have indicated the formation of supramolecular aggregates by strong pi-stacking of the large aromatic parts. Despite the extended aromatic character of the bqpy bridging ligand, electrochemical and spectroscopic studies of the dinuclear complex have shown that the complex is composed of four noninteracting parts: two Ru(bpy)(3)(2+)-type units bridged by two bqpy-localized fragments similar to two fused phenazine moieties.