The electronic structures of diruthenium complexes containing an oligo(phenylene ethynylene) bridging ligand, and some related molecular structures

The complexes [{Cp′(L2)Ru}C≡CC6H4C≡CC6H2(OMe)2C≡CC6H4C≡C{Ru(L2)Cp′}](L2 = (PPh3)2, Cp′ = Cp; L2 = dppe, Cp′ = Cp*) in which the metal centres are bridged by an oligomeric phenylene ethynylene (OPE) ligand have been prepared and the electronic structure of these representative ruthenium-capped OPEs investigated using a combination of electrochemical, UV-vis-NIR and IR spectroelectrochemical methods, and DFT-based calculations. The diruthenium complexes are oxidised to the thermodynamically stable dications [Cp′Ru(L2)C≡CC6H4C≡CC6H2(OMe)2C≡CC6H4C≡CRu(L2)Cp′]2+, which on the basis of the spectroelectrochemical and computational results can be described in terms of two non-interacting Ru(C≡CAr)(L2)Cp′ moieties. X-ray structures of the oligophenyleneethynylene HC≡CC6H4C≡CC6H2(OMe)2C≡CC6H4C≡CH, the bis(gold) complex Ph3PAuC≡CC6H4C≡CC6H2(OMe)2C≡CC6H4C≡CAuPPh3 and the precursor 1-ethynyl-4-(trimethylsilylethynyl)benzene are also reported.