A new multifunctional ferrocenyl-substituted ferrocenophane derivative: optical and electronic properties and selective recognition of Mg2+ ions |
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Authors: | Lopez Juan Luis Tárraga Alberto Espinosa Arturo Velasco M Desamparados Molina Pedro Lloveras Vega Vidal-Gancedo José Rovira Concepció Veciana Jaume Evans David J Wurst K |
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Institution: | Universidad de Murcia, Departamento de Química Orgánica, Facultad de Química, Campus de Espinardo, 30100 Murcia, Spain. |
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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 M?ssbauer 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. |
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Keywords: | electrochemistry electron transfer metallocenes molecular recognition Mössbauer spectroscopy |
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