Synthesis, structure and anion co-ordination chemistry of a novel macrocyclic cobaltocenium receptor

Abstract

A new macrocyclic amide-substituted cobaltocenium receptor, 1,1′-[(ethylenedioxy)bis(ethyleneaminocarbonyl)]cobaltocenium hexafluorophosphate 2 has been prepared and its single-crystal X-ray structure determined. Proton NMR anion co-ordination studies revealed that 2 and other new acyclic cobaltocenium derivatives complex chloride and bromide anions with 1:1 stoichiometry. Comparative stability constant evaluations imply that the macrocyclic receptor 2 forms halide complexes of greatest thermodynamic stability, suggestive of a ‘macrocyclic anion effect’. Cyclic voltammetric investigations showed the cobaltocenium receptors to electrochemically recognise halide anions.