title: Unusual coordination environment for barium cations in ion recognition conducting poly[Ni(salen)(receptor)] films.
abstract: [Ni( salen)] complexes bearing different crown ether receptors were electropolymerized to give films whose voltammetric signatures responded to Ba2+. In line with DFT calculations, X-ray absorption spectroscopy (XAS) near the Ni K-edge showed the nickel local environment in the monomers and their corresponding polymers (in the presence or absence of barium) to be identical. However, the expectation of crown size-dependent barium local environment (based on geometry and donor atom availability) was not found. XAS near the Ba K-edge showed that Ba2+ in the films coordinated to only two oxygen donors, irrespective of crown size. This surprisingly low coordination number (compared to solution species) is accompanied by a higher barium/crown ratio than the anticipated 1:1 stoichiometry. The implications of these effects for design and performance of sensors based on metal ion recognition chemistry are discussed.
authors.affiliation: Department of Chemistry, University of Leicester, University Road, Leicester, UK.
authors.forename: J
authors.initials: J
authors.lastname: Tedim
authors.forename: R
authors.initials: R
authors.lastname: Bessada
authors.forename: S
authors.initials: S
authors.lastname: Patrício
authors.forename: A L
authors.initials: AL
authors.lastname: Magalhães
authors.forename: C
authors.initials: C
authors.lastname: Freire
authors.forename: S J
authors.initials: SJ
authors.lastname: Gurman
authors.forename: A R
authors.initials: AR
authors.lastname: Hillman