Diruthenium Complexes with -Extended Bridging Bis(alkenyl)arylene Ligands, A Derived Metallamacrocycle, and Their Oxidized Forms

We report on dinuclear alkenylruthenium complexes with pi-extended trans,trans-distyrylbenzene (1-V) or 1,4-(2-phenylethynyl)benzene (1-A) linkers akin to oligophenylvinylene and oligophenylethynylene oligomers (OPV-3 and OPE-3, respectively) and the macrocylic analogue 2-A. All compounds were characterized by NMR spectroscopy and high-resolution ESI-MS. Their electrochemical and spectroscopic properties were examined. The efficacy of intramolecular through-bond electron transfer in their mixed-valent, one-electron-oxidized radical cations was probed by UV/vis/NIR and EPR spectroscopy as well as by density functional theory calculations. The terminally appended diruthenium tags of the present compounds add IR spectroscopy to the available toolbox and provide resolved hyperfine splittings to the P-31 nuclei in the EPR spectra of their one- and two-electron-oxidized radical cations and dications. Our results indicate charge localization on one {Ru}-CH=CHAr site on the IR time scale for [1-A](center dot+) and [2-A](center dot center dot 2+) and a small degree of charge delocalization in [1-V](center dot+). On the slower time scale of EPR spectroscopy, [1-V](center dot+) and [1-A](center dot+) become valence-detrapped or nearly so. The near breakdown of electronic coupling on fast time scales is also indicated by the finding that the chromophores present in [1-V](center dot+) and [1-V](2+), in [1-A](center dot+) and [1-A](2+), and in [2-A](center dot center dot 2+) and [2-A](4+) are mutually identical.