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 <i>trans</i>-{L_<i>x</i>Ru}­CCCC­{Ru­(dppe)₂}­CCCC­{RuL′_<i>y</i>} (L_<i>x</i>, L′_<i>y</i> = (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 RuL_<i>x</i> 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