Ammonium redox-responsive receptors containing multiple ferrocene and quinone redox-active centres attached to di- and tri-aza crown ether macrocycles
- 1 January 1993
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in J. Chem. Soc., Dalton Trans.
- No. 14,p. 2107-2116
- https://doi.org/10.1039/dt9930002107
Abstract
Eight new redox-active di- and tri-aza crown ether macrocyclic ligands containing multiple ferrocene and quinone moieties have been prepared, including the first reported mixed ferrocene–quinone macrocyclic ligand. Solution 1H and 13C NMR complexation studies suggest these ligands form 1:1 stoichiometric complexes with ammonium as guest cation. Single-crystal structures of the hydrogen hexafluorophosphate salt of 7,16-bis(ferrocenylmethyl)-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane and the ammonium complex of 4,10,16-tris(ferrocenylmethyl)-1,7,13-trioxa-4,10,16-triazacyclooctadecane have also been determined. Electrochemical investigations reveal the respective ferrocene–ferrocenium redox couples of most of the ligands are perturbed to more positive potentials on co-ordination of NH4 + and K+ guest cations. The above tris(ferrocenylmethyl) ligand selectively binds and electrochemically recognises NH4 + in the presence of equimolar concentrations of K+. Secondary amide-linked ferrocene aza crown ether ligands electrochemically sense the NH4 + guest cation primarily via host ferrocenecarboxide carbonyl oxygen–H–NH3 + hydrogen-bonding electrostatic interactions.Keywords
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