β-Cyclodextrin-Assisted Intervalence Charge Transfer in Mixed-Valent [2]Rotaxane Complexes Having Metal Centers Linked by an Interrupted π-Electron System

FeII to RuIII electron transfer is initiated by the inclusion of saturated bridging ligands into the β-cyclodextrin (CD) cavity of [2]rotaxane complexes and is observed as an intervalence charge transfer (IVCT) band in the electronic spectra (see picture). The rotaxanes are synthesized by using RuIII and FeII complexes as stoppers, β-CD as the cyclic molecular head, and 4,4′-bipyridine derivatives with interrupted π-electron system as the bridging ligand between the metal centers.