Journal of the American Chemical Society, Vol.126, No.38, 12090-12096, 2004
Mixed 1D-2D inorganic polymeric zinc ferrocenylphosphonate: Crystal structure and electrochemical study
Needs for ferrocene immobilization on robust host structures are considerable since derivative materials may find applications in medical areas, optical devices, or catalysis. Synthesis of phosphonate functionalized ferrocene allowed its subsequent inorganic polymerization with a zinc salt. The crystallographic structure of the compound obtained, Zn(HO(3)PFc)(2)(.)2H(2)O, shows a unique two-dimensional ferrocene arrangement anchored on a one-dimensional Zn-O-P-O-Zn backbone. The ferrocene packing in the title compound is very similar to the packing found in molecular ferrocene. The electroactivity of Zn(HO(3)PFc)(2).2H(2)O is thoroughly studied. It shows a reversible surface oxidation of ferrocene. Mossbauer spectroscopy for the oxidized compound shows an isomer shift of IS2b = 0.432 mm.s(-1) and a quadrupolar splitting of QS(2b) = 0.205 mm.s(-1), which is consistent with a stable S = 1/2 ferroceniurn state. The magnetic susceptibility study, Mossbauer spectroscopy, and galvanostatic titration show that only the ferrocene moieties present at the surface of the crystallites are reversibly oxidized. This observation is reinforced by a complex impedance study showing mainly resistive behavior and conductivity measurements indicating weak, thermally assisted, conductivity. The general properties of this compound demonstrate that phosphonato functionalization may be a useful approach for all fields concerned by immobilization of ferrocene.