Electrochemical and spectroscopic studies on nickel(II/III) complexes with novel 14-membered hexaaza macrocycle functionalized with propenyl groups

Abstract

A nickel(II) macrocyclic complex functionalized with propenyl groups, [Ni(1,8-di( n-propenyl)-1,3,6,8,10,13-hexaazacyclotetradecane)] 2+ {abbreviated as [Ni(A)] 2+}, has been synthesized by a simple template condensation reaction of the Ni 2+ ion, ethylenediamine, allylamine and formaldehyde in methanol. Spectral and electrochemical properties of the [Ni(A)] 2+ complex in various media have been investigated and compared with those of [Ni(1,8-dialkyl-1,3,6,8,10,13-hexaazacyclotetradecane)] 2+ complexes. The interaction of olefinic groups appended to the macrocycle with the nickel metal center is recognized by the spectral and electrochemical studies; in acetonitrile solution, the molar extinction coefficient of [Ni(A)] 2+ at λ max=458 nm grows up gradually and attains a maximum, and at the same time the cyclic voltammetric peak currents for the [Ni(A)] 2+/3+ redox couple decrease slowly with a concomitant growth of a new redox wave at more positive potentials. The first-order kinetic rate constants for the time dependent decrease of the peak currents of [Ni(A)] 2+/3+ redox couple are determined.