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

Six new unsymmetrical achiral complexes of Ru-II 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(mu BL) Ru(tpm) CLb](4+), were CLa and CLb represent two different chelating ligands (2,2'-bipyridine (bpy), 1,10-phenanthroline (phen) or 2,20-biquinoline (biq)); BL can be 4,4'-bipyridine (4,4'-bpy) or pirazine (pz). The structures of the new species have been elucidated by H-1 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 Ru-II-based complexes. (C) 2012 Elsevier B.V. All rights reserved.