Ni(0) catalysed homo-coupling reactions: a novel route towards the synthesis of multinuclear ruthenium polypyridine complexes featuring made-to-order properties.

A new synthetic procedure for the efficient preparation of dinuclear ruthenium(II) polypyridyl complexes is reported. The compounds synthesised are [(bpy)2Ru(BPBT)Ru(bpy)2](PF6)2 and [(bpy)2Ru(BPZBT)Ru(bpy)2](PF6)2 (bpys2,29-bipyridine; H2BPBTs5,59- bis(pyridin-2-yl)-3,39-bis(1,2,4-triazole); H2BPZBTs5,59-bis(pyrazin-2-yl)-3,39-bis(1,2,4-triazole). Electrochemical experiments show that the two dinuclear systems investigated exhibit pH switchable intercomponent interactions

Synthesis, photophysical and redox behaviour of unsymmetrical binuclear Ru(II) complexes based on tris(1-pyrazolyl)methane

Six new unsymmetrical achiral complexes of RuII containing the tripodal ligand tris(1-pyrazolyl)methan (tpm) on both metal centers have been prepared and fully characterized. Their general formula is [CLa(tpm)Ru(μBL)Ru(tpm)CLb]4+, were CLa and CLb represent two different chelating ligands (2,2′-bipyridine (bpy), 1,10-phenanthroline (phen) or 2,2′-biquinoline (biq)); BL can be 4,4′-bipyridine (4,4′-bpy) or pirazine (pz). The structures of the new species have been elucidated by 1H NMR, COSY and NOESY spectroscopy. Electrochemical, UV–Vis spectroscopical, luminescence, and spectroelectrochemical properties have been investigated for all the binuclear complexes. For two representative species DFT calculations were carried out. The experimental data have been thoroughly interpreted in terms of the role played by each constituent subunit within the assemblies. These results add comparative pieces of information to the knowledge of the properties of the RuII-based complexes

Near infra-red emitting Ru(II) complexes of tridentate ligands: electrochemical and photophysical consequences of a strong donor ligand with large bite angles

A novel N^N^N tridentate ligand dgpy (dgpy = 2,6-diguanidylpyridine) was synthesized by a Pd-catalyzed C-N bond-forming reaction. A novel family of [RuII(tpy')(dgpy)](PF6)2 (1 and 2) or [RuII(dpt')(dgpy)](PF6)2 (3 and 4) (tpy' = substituted-2,2′:6′,2′-terpyridine, dpt' = substituted-2,4-dipyrid-2′-yl-1,3,5-triazine) complexes are reported. The dgpy ligand (80%) and the heteroleptic complexes 1-4 (37-60%) were obtained in modest to good yields. The dgpy ligand and its complexes were fully characterized by a variety of techniques including X-ray crystallography and density functional theory (DFT). In cyclic voltammetric studies, the complexes exhibit a RuIII/II couple, which is 600-800 mV less positive than the RuIII/II couple in [Ru(tpy)2]2+. The 1MLCT absorption maxima of all the complexes (620-740 nm) are considerably red-shifted as compared to that of [Ru(tpy)2]2+ (474 nm). The 3MLCT emission maxima of complexes 1 and 2 are also red-shifted by about 270 nm compared to that of [Ru(tpy)2]2+ (629 nm) at room temperature (298 K), whereas the corresponding maxima for complexes 3 and 4 are shifted by about 330 nm at 77 K. The relative trends in redox potentials and 1MLCT maxima are in good agreement with DFT and TD-DFT calculations. Complexes 1 and 2 emit from a RuII-to-tpy 3MLCT state, which is rarely the emitting state at λ > 850 nm in [Ru(tpy)(N^N^N)]2+ complexes when the ancillary ligand is neutral. Complexes 1 and 2 also exhibit long excited-state lifetimes (τ ∼ 100 ns) at room temperature with associated quantum yield (Φ) of 0.001. The reported τ and Φ values are approximately 400-500 times and 1000 times higher compared to those of [Ru(tpy)2]2+ (τ = 0.25 ns, Φ ≤ 5 × 10-6), respectively. Complexes 3 and 4 emit from a RuII-to-dpt 3MLCT state, albeit only at 77 K (τ = 0.25 ns) due to rapid deactivation of their 3MLCT state according to the energy-gap law. The improved photophysical properties of the complexes are consequences of enlarged separation of the 3MLCT-3MC states, due to the strong donation and larger bite angles of the dgpy ligand