Syntheses, structures, and electrochemical properties of three complexes based on 5-ferrocenylpentanoic acid

Three new complexes, [Co(OOC(CH2)4Fc)2(4,4′-bipy)(H2O)2]n (1), [Cd(OOC(CH2)4Fc)2(4,4′-bipy)(H2O)2]n (2), and {[Co(η2-OOC(CH2)4Fc)2(bbbm)]·(CH3OH)}n (3) [bbbm = 1,1′-(1,4-butanediyl)bis-1H-benzimidazole, Fc = (η5-C5H4)Fe(η5-C5H4)], were obtained from the corresponding metal salts with the primary ligand 5-ferrocenylpentanoic acid and the subsidiary N-heterocyclic ligands, and their structures were fully characterized. X-ray diffraction analyses reveal that all of the complexes display 1-D chain structure and complexes 1 and 2 are isostructural. The electrochemical properties of complexes 1-3 and 5-ferrocenylpentanoic acid have been investigated in DMF solution. The results show that the half-wave redox potentials of the three complexes are close to the 5-ferrocenylpentanoic acid, which indicates that the coordination of the metal ions does not have significant effects on the redox potential of the 5-ferrocenylpentanoic acid ligand. Further investigations suggest that the redox processes of 5-ferrocenylpentanoic acid and complexes 1-3 are all chemically quasi-reversible processes and controlled by diffusion.