Novel electrochemical behaviour of a nickel(II)–13-membered macrocyclic tetra-amine effected by a pendent phenol

Abstract

The cis-macrocyclic configuration in the phenol-pendant-[13]aneN₄[11-(2′-hydroxyphenyl)-1,4,7,10-tetra-aza-cyclotridecane] complex with Ni^II rapidly rearranges to a ‘square planar’ form upon oxidation to Ni^III at ca.+0.6 V vs. saturated calomel electrode (s.c.e.) with a subsequent occurrence of a new reversible Ni^II/III process at +0.30 V for the macrocycle with a pendent phenol and +0.26 V vs. s.c.e. for that with a pendent p-nitrophenol; the thus generated short-lived high-spin square-planar Ni^II complex returns to the initial folded Ni^II complex with a half-life time of 11.4 s (for the p-nitrophenol macrocycle) at 25 °C.