Further investigation on preparation, structure and electrochemical properties of N-alkyl- and N-aryl-2-aza-[3]-ferrocenophanes

The reactions of 1,1'-bis(hydroxymethyl)ferrocene with primary amines such as 6-aminohexanol, cyclohexylamine, 4-phenylbutylamine, 2-isopropylaniline, 4-(trifluoromethyl)benzylamine, and 1-aminomethylferrocene in the presence of [RuCl2(PPh3)(3)] catalyst led to intermolecular condensation of the CH2OH and NH2 groups to afford N-alkyl or N-aryl substituted 2-aza-[3]-(1,1')-ferrocenophanes. Cyclic voltammograms of the obtained N-alkyl-2-aza-[3]-(1,1')-ferrocenophanes exhibit reversible redox of the Fe center at E-1/2 = -0.01 - +0.04 V (vs Ag+/Ag) and subsequent irreversible oxidation of the amino group of the ligand at E-ox = 0.41-0.44 V. N-(4-Hydroxyphenyl)-2-aza-[3]-(1,1')-ferrocenophane shows two pairs of reversible electrochemical oxidation and reduction at E-1/2 = 0.04 and 0.44 V. The latter potential is significantly lower than the corresponding electrochemical oxidation of N-aryl-2-aza-[3]-(1,1')-ferrocenophanes (0.68-0.75 V). The N-alkyl-2-aza-[3]-(1,1')-ferrocenophanes react with MeI to cause methylation of the amino group to produce cationic 2-aza-[3]-(1,1')-ferrocenophanes containing a quaternary nitrogen center. The iodo counter anion is easily replaced with BF4- or PF6-. Cyclic voltammograms of the cationic ferrocenophanes show the redox between ferrocene and ferrocenium at E-1/2 = 0.37-0.42 V.