Ferrocenes and molecular recognition

Anion recognition continues to attract considerable research interest. 

This interest may be attributed to the biological role played by anions. For example, enzymatic binding and reactions with ATP are the basis of the free energy in metabolism and the majority of enzymes act on anionic substrates. Several classes of artificial anion receptors have been reported, capable of not only binding but also of electrochemically recognizing anions. Such receptors have a potential application in the production of electrochemical anion sensors. 

Studies of linked metallocenes enabled the construction of a range of molecules comprising more than one metallocene unit. In particular, the interactions between metal centers have been studied. Several potential applications of such metallocene systems can be envisaged. For example, metallocene polymers can lead to interesting low-dimensional conductors. Distinct Fe and Fe sites in various monooxidized biferrocenes, between which electron transfer can take place, can lead to semiconductivity. Several studies have cen- 

Ziegler-Natta catalysts have long remained the only organometallic catalysts in macromolecular chemistry. The area was revolutionized by the discovery that zirconocene derivatives catalyze the polymerization of propene. At the same time, strong industrial interest has prompted a worldwide development in the field. The first polymers based on metallocene-type catalysts have recently appeared on the market under the names Hostacen (Hoechst AG), Exact (Exxon), and Affinity (Dow). The metals zirconium and hafnium appear to be the most important metals in synthetic preparations. 

The transition-metal-catalyzed ring-opening polymerization of silicon-bridged, strained, ring-tilted ferrocenophans yields polyferrocenylsilanes with intriguing properties.  

---