Simultaneous bridge-localized and mixed-valence character in diruthenium radical cations featuring diethynylaromatic bridging ligands

J Am Chem Soc. 2011 Nov 16;133(45):18433-46. doi: 10.1021/ja207827m. Epub 2011 Oct 24.

Abstract

A series of bimetallic ruthenium complexes [{Ru(dppe)Cp*}(2)(μ-C≡CArC≡C)] featuring diethynylaromatic bridging ligands (Ar = 1,4-phenylene, 1,4-naphthylene, 9,10-anthrylene) have been prepared and some representative molecular structures determined. A combination of UV-vis-NIR and IR spectroelectrochemical methods and density functional theory (DFT) have been used to demonstrate that one-electron oxidation of compounds [{Ru(dppe)Cp*}(2)(μ-C≡CArC≡C)](HC≡CArC≡CH = 1,4-diethynylbenzene; 1,4-diethynyl-2,5-dimethoxybenzene; 1,4-diethynylnaphthalene; 9,10-diethynylanthracene) yields solutions containing radical cations that exhibit characteristics of both oxidation of the diethynylaromatic portion of the bridge, and a mixed-valence state. The simultaneous population of bridge-oxidized and mixed-valence states is likely related to a number of factors, including orientation of the plane of the aromatic portion of the bridging ligand with respect to the metal d-orbitals of appropriate π-symmetry.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cations / chemistry
  • Free Radicals / chemistry
  • Hydrocarbons, Aromatic / chemistry*
  • Ligands
  • Models, Molecular
  • Molecular Structure
  • Organometallic Compounds / chemistry*
  • Quantum Theory
  • Ruthenium / chemistry*

Substances

  • Cations
  • Free Radicals
  • Hydrocarbons, Aromatic
  • Ligands
  • Organometallic Compounds
  • Ruthenium