Effect of chelate cycle size on the structure and stability of neodymium complexonates

Neodymium complexes with ethylenediamine-N,N'-dimalonic, ethylenediamine-N,N'-disuccinic, trans-1,2-diaminocyclohexane-N,N'-dimalonic, trans-1,2-diaminocyclohexane-N,N'-disuccinic acids are studied spectrographically to investigate the effect of the size of chelate cycles on the structure and stability of neodymium complexonates. It is shown that six-membered cycles are more stable and they are closed up rather than fine-membered ones. Enlargement of the cycles results in the changes in structure of complex and formation of complexes with different types of ligand coordination. For asymmetric ligands low-dentate low-stable complex appear. The advantage of six-membered cycles leading to formation of stronger complexes is realized only in symmetrical ligands