Ruthenium ammine/crown ether interactions in solution: effects of modification of both guest and host on the strength of second-sphere complexation

The effects of host (crown ether) size and structure and guest (ruthenium complex) oxidation state and primary ligand environment on binding strength were reported. It was found that binding increases with increased size and flexibility of the crown ether. It also increases with increased availability of ammine ligands, higher oxidation state and increased Lewis acidity of the guest. Small amounts of crown ether can also have substantial effects upon metal-ligand and metal-metal charge-transfer interactions.