Tuning electronic interactions in mixed valence ruthenium systems incorporating thiacrown ligands

This review outlines the synthesis and properties of mono and oligonuclear polypyridyl ruthenium complexes incorporating a range of S3 and S4 thiacrown ligands, focusing on the mixed valence complexes that have been produced in these studies. This work has revealed that the chemical, electrochemical, and electronic properties of the metal centers are modulated by the nature of the coordinated thiacrown ligand. In particular the back-bonding properties of the ligands mean that they strongly stabilize the ruthenium(II) state and also produce metal centers that are relatively kinetically labile. These distinctive electronic properties have been exploited in the construction of mixed valence systems with unusual electrochemical properties and also facilitated the self-assembly of oligonuclear molecular architectures with multiple accessible oxidation states. Computational studies on the isovalent and mixed valence complexes reflect the experimental data by indicating that, within a series of S4 coordinated dinuclear complexes, the properties of the mixed valence state are subtly dependent on the cavity size of the coordinated thiacrown.