SOLUTION PHASE CHEMISTRY OF LANTHANIDE COMPLEXES. 11.1:1 AND 1:2 LANTHANIDE COMPLEXES WITH NITRILOTRIACETIC ACID

Abstract

Abstract The solution phase coordination chemistry associated with the 1:1 and 1:2 complexes of lanthanide ions with nitrilotriacetic acid (NTA) has been studied by spectroscopic means. The Tb(III) luminescence intensities and lifetimes were found to be sensitive toward the solution phase properties, as was the hypersensitive absorption of the Ho(III) complexes. It was found that below neutral pH values, Ln(NTA) complexes were monomeric in nature and contained an average of 4.5 molecules of coordinated water. Above neutral pH, the Ln(NTA) complexes became self-associated into hydroxy bridged, oligomeric species. The Ln(NTA)2 complexes remained monomeric at all pH values, and contained one coordinated solvent molecule. In all cases, the coordination number of the lanthanide species was approximately nine.