Redox and optical properties of conjugated ferrocene oligomers

Internuclear electronic interactions in conjugated ferrocene oligomers disp lay unique redox and optical properties. I describe here recent research on the dependence of such properties on the number of ferrocene nuclei and on the structure of conjugated spacers. The neighboring-site interaction mode l explains the redox properties of oligo(ferrocene-1,1'diyl)s. The infrared (IR) spectra of carbonyl complex-bound biferrocene and terferrocene enligh ten the electronic structure in the mixed-valence states. Energy shifts of intervalence transfer (IT) in the mixed-valence states of oligo(ferrocene-1 ,1'-diyl)s resulting from changes in the oxidation state are rationalized b y taking into account the change in neighboring-site combination by photo-e lectron transfer, which delivers extra energy due to the strain in internuc lear distance. Oligo- and poly-(ferrocene-1,1'-diyl)s oxidized partially by tetracycanoethylene (TCNE) exhibit near-IR photoconductivity. Conjugated s pacer groups between ferrocene nuclei involving metal complex moieties affe ct the redox properties of ferrocene dimers significantly. The azo group ac ts as a distinctive spacer of which conjugation ability is changeable photo chemically.