Spectroscopic and Electrochromic Behavior of a Pentanuclear Cyanoiron(Ii)-Polyimine Supermolecule and Its Corresponding Prussian Blue Film

Abstract

A novel pentanuclear iron(II)-polyimine complex containing four pentacyanoferrate(II) groups attached to peripheral pyridine residues has been synthesized, exhibiting a characteristic iron-to-pyridine charge-transfer band at 395 nm, in addition to the iron-to-polyimine charge-transfer bands at 490 and 600 nm. The corresponding Mössbauer spectrum has been deconvoluted in terms of two symmetric doublets of 4:1 relative intensities, respectively, at IS = 0.345 and 0.021 mm/s and QS = 0.841 and 0.845 mm/s, associated with the pentacyanoferrate(II) and the iron(II)-polyimine centers. The peripheral groups can be reversibly oxidized at 0.38 V, in aqueous solution, leading to the decay of the 395 nm band. This process is not accessible in the corresponding Prussian-blue film; instead, the electrochromic behavior observed in this case reflects the changes in the intervalence-transfer band at 750 nm, accompanying the electrochemical process at 0.4 V associated with the Fe^III/II redox couple in the matrix.

Key Words:

• cyanoiron-complex
• iron-polyimine complex
• electrochromism
• Prussian blue film
• spectroelectrochemistry