Synthesis and characterization of hexadentate cobalt(III) complexes with new edta-type ligands. Part 4. Circular dichroism of the trans(O5O6) isomer of a cobalt(III) complex of 1,3-propanediamine-N, N, N′-triacetic-N′-3-propionic acid

One of two geometrical isomers of the hexadentate cobalt(III) complex with 1,3-propanediamine- N , N , N ′-triacetate- N ′-3-propionate ion (1,3-pd3ap) has been prepared and resolved. The NMR, electronic absorption and circular dichroism (CD) spectra were used to characterize the complex. The 1 H and 13 C NMR spectra of this geometrical isomer indicate that its six-membered propionate chelate ring is bound axially to the cobalt(III) ion, trans (O 5 O o )-[Co(1,3-pd3ap)] − . The (−) 546 - trans (O 5 O o )-[Co(1,3-pd3ap)] − complex, with a positive CD peak at lowest energy in the first spin-allowed absorption band region is tentatively assigned the Λ absolute configuration. Spectral data for this complex are discussed in relation to those of other [Co(edta-type)] − complexes which vary the size of carboxylate arms in the same way but maintain a six-membered diamine ring.