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

摘要

A novel, simple approach to the synthesis of macrocyclic dioxotetraamine ligands bearing pendent coordinating groups is described. Reduction of 2H-1-benzopyran-3-carboxylic acid 2-oxo-ethyl ester or its derivatives with sodium borohydride and then aminolysing the products with triethy]enetetraamine, without isolation of intermediates, leads to 12-(2'-hydroxyl)-benzyl-1,4,7,10-tetraazacyclotridecane-11,13- dione or the corresponding macrocyclic ligand. The ligands were characterized by elemental analysis, 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., the 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 redox 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 the other is the oxidation of a Cu(II) complex to a Cu(II) complex. Electron-withdrawing substituents increase the oxidation potential. [References: 48]