Extending Metal-Capped Polyynediyl Molecular Wires by Insertion of Inorganic Metal Units

Several symmetric and asymmetric bis(metalla-diynediyl)ruthenium(II) complexes of the general formula trans-{LxRu}C≡CC≡C{Ru(dppe)2}C≡CC≡C{RuL′y} (Lx, L′y = (PPh3)2Cp, (dppe)Cp, (dppe)Cp*), containing Ru(dppe)2 as the central linking group, have been successfully synthesized and characterized spectroscopically. DFT calculations show that their HOMO’s are delocalized over the Ru–C4–Ru–C4–Ru chain, suggesting that there is electronic interaction between the terminal RuLx groups through the C4 chains and the Ru(dppe)2 center. Limited electrochemical measurements reveal that the complexes undergo a series of five stepwise reversible or quasi-reversible oxidation processes.