Synthesis and characterization of bis-[PcRu(CO)][Ru2(ap)4(C≡CC5H4N)2]

A tetra-ruthenium complex containing two ruthenium( II) phthalocyanines and one metal-metal bonded diruthenium(III,III) unit was synthesized and investigated as to its electrochemical and spectroscopic properties in non-aqueous media. The title compound, represented as bis-[PcRu(CO)][ Ru-2(ap)(4)(C equivalent to CC5 H4N)(2)], where ap = 2-anilinopyridinate anion and Pc = the dianion of tetra-tert-butylphthalocyanine, was assembled by axial coordination of two PcRu(CO) macrocycles to pyridine groups of the complex which were themselves linked to the diruthenium(III, III) unit via alkyne groups. The tetra-ruthenium complex was characterized in solution and in the solid state by H-1 NMR, UV-visible and IR spectroscopies, mass spectrometry and cyclic voltammetry while thin-layer UV-visible spectroelectrochemistry was used to study the site of electron transfer. Eight redox processes occur in CH2Cl2 or benzonitrile, four of which can be assigned to the macrocycles of PcRu(CO) and four to the central diruthenium unit of the molecule. The electrochemical and spectroscopic data suggest a weak electronic interaction between the diruthenium unit of [Ru-2(ap)(4)(C=CC5H4N)(2)] and the two externally linked Ru(II) phthalocyanines of the title compound.