Rigid ferrocenophane and its metal complexes with transition and alkaline-earth metal ions


The rigid [6]ferrocenophane, L(1), was synthesised by condensation of 1,1'-ferrocene dicarbaldehyde with trans-1,2-diaminocyclohexane in high dilution at r.t. followed by reduction. When other experimental conditions were employed, the [6,6,6]ferrocenephane (L(2)) was also obtained. Both compounds were characterised by single crystal X-ray crystallography. The protonation of L(1) and its metal complexation were evaluated by the effect on the electron-transfer process of the ferrocene (fc) unit of L(1) using cyclic voltammetry (CV) and square wave voltammetry (SWV) in anhydrous CH(3)CN solution and in 0.1 M (n)Bu(4)NPF(6) as the supporting electrolyte. The electrochemical process of L(1) between 300 and 900 mV is complicated by amine oxidation. On the other hand, an anodic shift from the fc/fc(+) wave of L(1) of 249, 225, 81 and 61 mV was observed by formation of Zn(2+), Ni(2+), Pd(2+) and Cu(2+) complexes, respectively. Whereas Mg(2+) and Ca(2+) only have with L(1) weak interactions and they promote the acid-base equilibrium of L(1). This reveals that L(1) is an interesting molecular redox sensor for detection of Zn(2+) and Ni(2+), although the kinetics of the Zn(2+) complex formation is much faster than that of the Ni(2+) one. The X-ray crystal structure of [PdL(1)Cl(2)] was determined and showed a square-planar environment with Pd(II) and Fe(II) centres separated by 3.781(1) angstrom. The experimental anodic shifts were elucidated by DFT calculations on the [ML(1)Cl(2)] series and they are related to the nature of the HOMO of these complexes and a four-electron, two-orbital interaction. (C) 2010 Elsevier Ltd. All rights reserved.



subject category

Chemistry; Crystallography


Cui, XL; Delgado, R; Costa, J; Drew, MGB; Costa, PJ; Felix, V

our authors


The authors acknowledge the financial support from Fundacao para a Ciencia e Tecnologia (FCT) with co-participation of the European Community funds FEDER, for the financial support under project PTDC/QUI/56569/2004. X.C. and P.J.C. thank FCT for the post-doctoral Grants No SFRH/BPD/1502/2000 and SFRH/BPD/27082/2006, respectively. M.G.B. Drew thanks the University of Reading and the EPSRC (U.K) for funds for the Marresearch Image Plate and Oxford Diffraction X-Calibur diffractometers.

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