Diruthenium(ii,iii) paddlewheel complexes: effects of bridging and axial ligands on anticancer properties

This article provides an overview of the application of diruthenium(ii,iii) paddlewheel complexes for anticancer purposes. The use of this coordinative construct is indeed attractive because it provides an excellent opportunity to combine the pharmacological properties of the dimetallic ruthenium center with those derived from the specific choice of ligands bearing a carboxylic function capable of coordination towards the Ru-Ru core. Indeed, the combination of carboxylate ligands with specific anticancer properties and the dimetallic center permits the production of new entities endowed with improved biological profiles. Additionally, these systems allow the simultaneous multiple deliveries of a drug to the target site. Nevertheless, in order to obtain the desired effects, it is mandatory to consider some relevant chemico-physical aspects such as the steric hindrance of the ligands or the possibility of their release under specific biological conditions that should be taken into account in the design of effective complexes. Accordingly, through various examples from the literature, the key features of this family of unconventional compounds are summarized here, also providing useful hints for the design of improved diruthenium(ii,iii) paddlewheel complexes.