Abstract
Four divinylphenylene-bridged diruthenium complexes [{Ru(CO)(P
Pr
(L-
)}
-CH=CH-C
-CH=CH-1,4)] (
with
-chelating 2-hydroxypyridine and 2-hydroxy- or 8-hydroxyquinoline ligands are presented. They were studied by NMR spectroscopy, electrochemical methods and, in their neutral and oxidized states, by IR, UV/Vis/NIR and, if applicable, by EPR spectroscopy. The experimental studies are complimented by (TD-)DFT calculations. Our results indicate that the pyridine-olate complexes
exist as three isomers with a ratio of about 78:20:2 that differ with respect to the orientation of the
and
donors relative to the CO and alkenyl ligands in the equatorial coordination plane. Only the isomer with both imine
donors
to the alkenyl ligand is observed for complexes
with quinolinato ligands. All complexes undergo two consecutive, chemically and electrochemically reversible one-electron oxidations at low potentials. Our results indicate strong contributions of the divinylphenylene bridge to the redox processes and an even delocalization of the electron hole and the unpaired spin density over the entire π-conjugated divinylphenylene diruthenium backbone with only minor involvement of the peripherally attached
donor ligands.