[Ru(bipy)(CN)4]2− and its derivatives: Photophysical properties and its use in photoactive supramolecular assemblies

This review describes the intriguing properties of the complex anion [Ru(bipy)(CN)4]2−, whose redox and photophysical properties are strongly solvent-dependent. This complex and its analogues and derivatives are proving to be of particular value as components of polynuclear assemblies because of the ease with which they associate with other species by either hydrogen-bonding via the cyanides, or by direct ligation of the cyanide ligands to other metal ions. The strong solvatochromism means that the ability of the complex to act as an energy or electron donor in its 3MLCT excited state can be switched over a wide range, a feature which has so far only been exploited in a few instances.