title: Extension of conjugation: probing anion binding strength and reporter mechanisms in (phenyl)cyclopentadienyl and indenyl receptors.
abstract: Two families of novel organo-iron functionalized boranes have been developed for anion binding/detection. Synthetically simple phenylferrocene systems, while stable to air and moisture, possess similar binding affinities to FcBMes2 and no workable discrimination between F(-) and CN(-). In addition, reduced electronic communication between receptor and reporter sites brought about by a lack of conformational rigidity means that photochemical and electrochemical responses to anion binding are intrinsically weak. Receptors based on a more rigid indenyl framework are available in two steps from organic precursors (in ca. 50% yield), and feature intrinsically higher binding constants for F(-) and especially CN(-), consistent with the lower LUMO energies implied by extended conjugation. One such system, (4-dimesitylboryl-indenyl)cyclopentadienyl-iron(ii), can be shown to bind cyanide in protic media with an accompanying green to red/pink colour change. Extremely high selectivity over fluoride and hydroxide and a detection limit of ca. 10 ppm represent a highly desirable combination among borane derived cyanide receptors.
authors.affiliation: Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford, OX1 3QR, UK. Simon.Aldridge@chem.ox.ac.uk.
authors.forename: Rémi
authors.initials: R
authors.lastname: Tirfoin
authors.forename: Joseph A B
authors.initials: JA
authors.lastname: Abdalla
authors.forename: Simon
authors.initials: S
authors.lastname: Aldridge
mesh_terms: D001880:Boranes / Q000138:chemical synthesis / Q000737:chemistry*; D018360:Crystallography, X-Ray; D003517:Cyclopentanes / Q000138:chemical synthesis / Q000737:chemistry*; D005296:Ferrous Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D054879:Halogenation; D000075163:Metallocenes; D008958:Models, Molecular
chemical_list: D001880:Boranes; D003517:Cyclopentanes; D005296:Ferrous Compounds; D000075163:Metallocenes; C004998:ferrocene