Macrocyclic complexes: Synthesis and characterization of cobalt(II), nickel(II) and copper(II) complexes with [14]1,4,5,7,8,11,12,14-octaaza-2,3,9,10-tetraoxo-1,4,5,6,6,7,8,11,12,13,13,14-dodecahydrocyclotetradecane (OTCT)

A series of macrocyclic complexes of the titled ligand have been isolated by the action of formaldehyde (H 2 CO) on bis-(1,4-diamino-1,4-diaza-2,3-dioxobutane) complexes of cobalt(II), nickel(II) and copper(II). The coordination template effect governs the steric course of the reaction. The structures of the complexes have been elucidated on the basis of IR, electronic, ESR spectral data, magnetic properties, electrochemical studies and thermal data. Electrochemical studies show that all the complexes show two well defined reduction curves corresponding to the formation of species where the metal ion can be formally assigned an oxidation state of +I and zero respectively.