A CONVENIENT METHOD FOR THE SYNTHESIS OF MACROCYCLIC DIOXOTETRAAMINE LIGANDS BEARING PENDENT COORDINATING GROUPS AND THE PROPERTIES OF THEIR COPPER(II) COMPLEXES

A novel, simple approach to the synthesis of macrocyclic dioxotetraami ne ligands bearing pendent coordinating groups is described. Reduction of 2H-1-benzopyran-3-carboxylic acid 2-oxo-ethyl ester or its derivat ives with sodium borohydride and then aminolysing the products with tr iethy]enetetraamine, without isolation of intermediates, leads to xyl) -benzyl-1,4,7,10-tetraazacyclotridecane-11,13- dione or the correspond ing macrocyclic ligand. The ligands were characterized by elemental an alysis, IR, H-1 NMR and MS. The ligands can be triprotonated including the phenolate. Five-coordinated [Cu(H(-2)L)](-) and four-coordinated [Cu(H(-1)L)] complexes were found to form in aqueous solution, i.e., t he phenolic group can be coordinated to the copper(II) ion. Formation constants of the copper(II) complexes were determined by pH titration. These copper(II) complexes have axial symmetry according to their EPR spectra; the EPR parameters were obtained by computer fitting. Two re dox processes appeared in the cyclic voltammogram in the range of -0.1 to -0.8 V (versus SCE); one is the oxidation of phenol hydroxyl and t he other is the oxidation of a Cu(II) complex to a Cu(II) complex. Ele ctron-withdrawing substituents increase the oxidation potential.