Cobalt(III) Tetraazamacrocyclic Complexes with Pendant Amino Groups: Synthesis, Structure and Electrochemical Properties

Abstract

AbstractTwo isomeric cis‐2,9‐bis(aminomethyl)‐5,7,7,12,14,14‐hexamethyl‐1,4,8,11‐tetraazacyclotetradecane (1 and 2) and two 2‐aminomethyl‐2‐methyl‐1,4,8,11‐tetraazacyclotetradecane (3 and 4) cobalt(III) complexes have been prepared and characterised. During the synthesis of 2 a minor oxidation product 5 was formed. The structures of 3, 4 and 5 have been determined by X‐ray crystallography, and the UV/Vis spectra of 1−5 have been analysed. The average Co−N distances in 1 and 2 have been estimated from the correlation between the average Co−N bond lengths and position of the maximum absorption for hexaamine complexes given in literature. The electrochemical behaviour of 1−5 in neutral and acidic solutions has been studied by cyclic voltammetry. In complexes displaying electronic maxima at higher energy, cobalt(III) was reduced at more negative potentials. Small differences in the conformation of ligand between 3 and 4 explain the different behaviour of these complexes in acidic solutions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)