Phosphorus-containing dendrimers with ferrocenyl units at the core, withinthe branches, and on the periphery

The synthesis of new ferrocene derivatives bearing phenoxy and/or formyl gr oups allows one to obtain phosphorus-containing dendrimers with ferrocene u nits at the core, within the branches, and at the periphery. Dendrimers wit h a ferrocene at the core were built from 1,1'-ferrocenedicarboxaldehyde up to the fourth generation. A marked dendritic effect is observed for this f amily of compounds; indeed, the ferrocenyl core is insulated from the outsi de in the largest dendrimers (32 or 64 CHO end groups), and the molecule is almost electrochemically inactive. The first dendrimers having three conse cutive ferrocene layers within the branches are also described; inner layer s are oxidized at the same potential, but the outer layer needs a higher po tential to be oxidized, owing to the presence of electron-withdrawing formy l groups. Dendrimers bearing ferrocenyl groups at the periphery are synthes ized up to the ninth generation. These compounds are the largest redox acti ve dendrimers ever synthesized; all these ferrocenyl units are oxidized at the same potential, showing that they are all equivalent and electrochemica lly independent. The exhaustive electrolysis furnishes multiferrocenium den drimers, which deposit onto electrodes as a stable and conducting film. The multiferrocenium dendrimers can be reduced again quantitatively to neutral dendrimers without apparent decomposition.