Molecular batteries: Ferrocenylsilylation of dendrons, dendritic cores, and dendrimers: New convergent and divergent routes to ferrocenyl dendrimers with stable redox activity

The ferrocenylsilylation of the phenol triallyl dendron 2, of the phenol no naallyl dendron 4, and of the 9-, 27-, 81-, and 243-allyl dendrimers 7-10 ( monitored by the disappearance of the signals of the olefinic protons in H- 1 NMR spectra) has been achieved using ferrocenyldimethylsilane 1 and Karst edt's catalyst in diethyl ether at 40 degrees C, yielding the corresponding ferrocenyl dendrons and dendrimers. An alternative convergent synthesis of the nonaferrocenyl dendron 5 was carried out by reaction of the triferroce nyl dendron 2 with a protected triododendron followed by deprotection. Reac tion of the nonaferrocenyl dendron 5 with hexakis(bromomethyl)benzene gave the 54-ferrocenyl dendron 6. All the ferrocenyl dendron and dendrimers prod uce a chemically and electrochemically reversible ferrocenyl oxidation wave at seemingly the same potential. Stable platinum electrodes modified with the high ferrocenyl dendrimers were fabricated. The soluble orange-red ferr ocenyl dendrimers can also be oxidized in CH2Cl2 by [NO][PF6] to the insolu ble deep blue polyferrocenium dendrimers. For instance, the: 243-ferroceniu m dendrimer has been characterized by its Mossbauer spectrum, which is of t he same type as that of ferrocenium itself. The ferrocenium dendrimers can be reduced without any decomposition back to the ferrocenyl dendrimer, indi cating that these multielectronic redox-stable dendrimers behave as molecul ar batteries.