A new ditopic receptor containing tetraazamacrocyclic and crown ether fragments. Synthesis, spectral characteristics, and redox behavior

Abstract

Abstract A new ditopic molecule consisting of nickel azamacrocyclic and crown ether subunits has been synthesized via Schiff base condensation between formylbenzo-15-crown-5 and the pendant amino group of nickel(II) tetraazamacrocyclic complex. The structure of this compound has been confirmed by elemental analysis, IR, electronic absorption spectrocopy, and FAB mass spectrometry. A substantial cathodic shift of the Ni(III)/Ni(II) redox potential was observed for this ditopic molecule in the presence of ammonium salts. This is in contrast to the ammonium ion induced anodic shifts observed for other ditopic molecules containing crown ether and redox active fragments. The interactions of parent monomacrocyclic and ditopic nickel(III) complexes with some bifunctional reductants were investigated. The electrochemical and kinetic results were explained in terms of an “open”—“closed” conformational equilibrium for the bis-macrocyclic molecule and supramolecular complex formation through two-centered substrate—r...