title: Redox-active pH-responsive molecules: ferrocenylphosphonic acid, ferrocenylmethylphosphonic acid and 1,1'-ferrocenylbisphosphonic acid. Structural determination of FcPO3Na2.5H2O.
abstract: The acidity constants of the reduced and oxidized species of ferrocenylphosphonic acids FcPO3H2, FcCH2PO3H2 and fc(PO3H2)2 (Fc = (eta5-C5H5)Fe(eta5-C5H4), fc = (eta5-C5H4)Fe(eta5-C5H4)) in water have been evaluated by potentiometric, 31P NMR, and electrochemical methods. The oxidized forms are more acidic than the reduced ones. The interaction between the redox centre and the charged oxygen atoms of the phosphonate group is shown to be electrostatic. The maximum oxidation shift DeltaE between the protonated and unprotonated species increases with the number of charges of the substrate and decreases with the increase of the distance between the ferrocenyl centre and the oxygen atoms of the phosphonate group. The structure of FcPO3Na2.5H2O is determined. The compound crystallizes in the monoclinic system. It is lamellar with an inorganic layer formed by tetramers Na4O14, the ferrocenyl groups occupying the interlamellar space.
authors.affiliation: Laboratoire de Chimie Moléculaire et Organisation du Solide, CNRS UMR 5637, Université Montpellier 2, Place Eugène Bataillon, Case courrier 007, 34095 Montpellier cedex 05, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Oms
authors.forename: Arie
authors.initials: A
authors.lastname: van der Lee
authors.forename: Jean
authors.initials: J
authors.lastname: Le Bideau
authors.forename: Dominique
authors.initials: D
authors.lastname: Leclercq