The following have been demonstrated as solution equilibria, with detectable population of several isomers. [GRAPHICS] erification or for RNA cleavage. Replacement of one of the amide coordinating groups to form a new heptadentate ligand yields a europium(III) complex ([Eu(NBAC)](3+)) that is a very active catalyst for phosphate diester transesterification at 37 degrees C, pH 7.40. Laser-induced luminescence is used to study the number of bound water molecules and self-association of the [Eu(NBAC)](3+) complex as well as the dissociation of the complex in the presence of competing ligands. [GRAPHICS]