Lanthanide-organic ligand interaction

Choppin [24] examined some aspects of lanthanide-organic ligand interaction in aqueous solutions. An interpretation of thermodynamic parameters (AG, AH and AS) of complexation have been given in terms of hydration, inner versus outer sphere character, stability vs. chelate ring size and ligand charge polarization. 

For both of these ligands the complexes formed when the acetates, chlorides, nitrates, and thiocyanates are used as the starting materials have a smaller number of organic ligands, coordination of some or all of the anions (the structure of the ten-coordinate complex [La(o-phen)2(N03)3] has been discussed earlier, section 3.9), and perhaps may be solvated as well (Forsberg, 1973). Most of the preparations can be carried out in aqueous or anhydrous ethanol. The existence of the lanthanide-nitrogen bond is clearly implied in these compounds and the infrared spectra (Sinha, 1964) and ultimately, complete structure determination, have verified that this interaction does take place. It should also be noted that both of these molecules form adducts with the tris-j8-diketone complexes and the structures of two of these with ortho-phenanthroline have been determined (Watson et al., 1972 Cunningham, 1973). 

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