Synthesis and characterization of hexadentate cobalt(III) complexes with new edta-type ligands Part 3. Circular dichroism of cobalt(III) complexes of ethylenediamine- N,N,N′-triacetic- N′-3-propionic acid and ethylenediamine- N,N,-diacetic- N′,N′-di-3-propionic acid

Abstract

Cobalt(III)complexes with the hexadentate ligands, ethylenediamine- N,N,N′-triacetate- N′-3-propionate(ed3ap) and ethylenediamine- N,N-diacetate- N′,N′-di-3-propionate ion (u-eddadp), have been prepared, chromatographically separated and resolved. Only one of two geometrical isomers of the [Co(ed3ap)] − complex was isolated. A 1H NMR spectrum of this isomer, trans(O 5)-[Co(ed3ap)] −, indicates that its six-membered propionate chelate ring is bound equatorially to the cobalt(III) ion. There is no similar structural variation possible for the hexadentate u-eddadp ligand. (−) 546- trans(O 5)-[Co(ed3ap)] − and (+ ) 546-[Co(u-eddadp)] − complexes with a positive CD peak at lowest energy in the first spin-allowed absorption band region are tentatively assigned the A absolute configuration. Spectral data of these complexes are discussed in relation to those of other [Co(edta-type)] − complexes of known structure.