U n i v e r s i t y   o f   A r i z o n a   •  O l d   C h e m i s t r y  R o o m   1 0 8 b  •  5 2 0 / 6 2 6 - 3 3 8 7

Lanthanide ions and complexes occupy a special position in developing synthetic nucleases that function as catalysts for the hydrolytic cleavage of RNA or DNA.  Stimulated by the serendipitous isolation of a number of lanthanide complexes that feature the common active-site structure of dinuclear metallo-phosphodiesterases, we have been attempting the rational design and synthesis of polynuclear lanthanide–hydroxo species via ligand-controlled hydrolysis of the lanthanide ions. The efforts yielded a series of highly sophisticated yet structurally well-defined lanthanide–hydroxo complexes. In addition to their potential applications for the study of biomimetic catalysis of phosphate diester cleavage, these high-nuclearity complexes may, with appropriate further development, be used as contrast-enhancing agents in biomedical imaging procedures.