title: A new multifunctional ferrocenyl-substituted ferrocenophane derivative: optical and electronic properties and selective recognition of Mg2+ ions.
abstract: The synthesis, characterisation, and X-ray structure of a new strained asymmetric diferrocene derivative (2) is reported. Compound 2 acts as a highly specific electrochemical and optical Mg(2+) ion sensor, as revealed by spectroscopic and electrochemical techniques. Thus, in the presence of Mg(2+), a new redox peak appears in the cyclic voltammogram (CV) that is anodically shifted compared to the E(1/2) of the free receptor (DeltaE(1/2)=340 mV). Diferrocene derivative 2 also gives a highly visual response upon addition of Mg(2+), namely a change of colour from orange to deep purple. In addition, compound 2 does not show any significant sensing activity in the presence of Ca(2+) or alkaline ions. On protonation, it is converted into the stable diferrocenylcarbenium salt 4, in which two different modes of stabilisation of the alpha-carbocationic centre are clearly demonstrated by a combination of (1)H NMR and (57)Fe Mössbauer spectroscopic measurements. Finally, by a partial (chemical or electrochemical) oxidation, compound 2 forms the asymmetric mixed-valence species 2(+), which can be isolated as the solid salt 6 by using CF(3)SO(3) (-) as a counterion. This mixed-valence species shows a fast intramolecular electron-transfer process, as ascertained by several spectroscopic techniques.
authors.affiliation: Universidad de Murcia, Departamento de Química Orgánica, Facultad de Química, Campus de Espinardo, 30100 Murcia, Spain.
authors.forename: Juan Luis
authors.initials: JL
authors.lastname: Lopez
authors.forename: Alberto
authors.initials: A
authors.lastname: Tárraga
authors.forename: Arturo
authors.initials: A
authors.lastname: Espinosa
authors.forename: M Desamparados
authors.initials: MD
authors.lastname: Velasco
authors.forename: Pedro
authors.initials: P
authors.lastname: Molina
authors.forename: Vega
authors.initials: V
authors.lastname: Lloveras
authors.forename: José
authors.initials: J
authors.lastname: Vidal-Gancedo
authors.forename: Concepció
authors.initials: C
authors.lastname: Rovira
authors.forename: Jaume
authors.initials: J
authors.lastname: Veciana
authors.forename: David J
authors.initials: DJ
authors.lastname: Evans
authors.forename: K
authors.initials: K
authors.lastname: Wurst
mesh_terms: D004583:Electrons; D005296:Ferrous Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D008274:Magnesium / Q000737:chemistry*; D000075163:Metallocenes; D008956:Models, Chemical; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis*
chemical_list: D005296:Ferrous Compounds; D000075163:Metallocenes; D009942:Organometallic Compounds; D008274:Magnesium; C004998:ferrocene