Chemistry Faculty
Research Interests
Coordination and Bioinorganic Chemistry; Biophysical Chemistry-The design of specific chelating agents for metal ions has a wide array of applications and can parallel the approach taken by nature
Professor Raymond's research interests range from biochemistry and metals in medicine to physical inorganic chemistry. The underlying theme of the research projects is the question of metal-ligand specificity of interaction in coordination and bioinorganic chemistry. The specific current research areas are:
- Iron Chelation Chemistry. Synthetic analogs of the siderophores are being produced to prepare sequestering agents specific for ferric ion. A general interest in the coordination chemistry of iron transport and storage proteins has several applications. The coordination chemistry of iron in transferrin and ferritin is of relevant for the potential treatment of diseases, particularly anemias. For some time we have also developed iron sequestering agents as potential new therapeutic agents for iron chelation therapy to treat human iron overload as occurs particularly in b-thalassemia major (Cooley's Anemia).
- Supramolecular Chemistry. The Raymond group has developed a predictive design strategy resulting in the synthesis of various high-symmetry coordination clusters including M2L3 helicates and mesocates, M4L6 and M4L4 tetrahedra, M6L6 and M8L8 cylinders, and M8L6 octahedra. These examples all focus on the coordination of three bidentate chelators to a tri- or tetravalent metal ion in a pseudo-octahedral fashion at the apices of the clusters to generate local three-fold symmetry at these metal centers. These chelators are contained in rigid, symmetric multi(bidentate)-ligands which supply the other symmetry elements of the cluster (2-fold, 3-fold, or mirror plane). By simultaneously fulfilling the symmetry requirements of both the ligand and metal centers, discrete high-symmetry clusters are generated under thermodynamic control. We are exploring the self-assembly of new clusters, thermodynamics and kinetics of cluster formation and host-guest interactions, electrochemistry, luminescence, ligand exchange, and chiral resolution and isomerization in the context of these supramolecular clusters.
- Lanthanide Coordination Chemistry. The use of paramagnetic metal complexes as image enhancing agents in magnetic resonance imaging (MRI) is opening up a new field of coordination chemistry. The group is involved in the synthesis and characterization of such compounds, particularly Gd(III) complexes. One such agent is now the number 2 MRI enhancement agent in chemical use. Raymond and coworkers have been working on hydroxypyridinone and mixed hydroxypyridinone-terephthalamide based complexes that show promise due to their higher relaxivity. This increase in relaxivity is due to both an increase in the number of coordinated water molecules and near-optimal water exchange rates. The high stability of the complex, and the high selectivity of the ligand for Gd(III) over physiologically available metals such as Zn(II) and Ca(II) predicts low toxicity for our complexes. Work is currently in progress to further increase relaxivity using these ligand systems as well as to understand their advantageous water-exchange kinetics. Fluorescent lanthanide agents are being developed for other kinds of imaging or analysis.
- Actinide Coordination Chemistry. The similarities in the chemical properties and the biological transport and distribution properties of Fe(III) and Pu(IV) explain much of the behavior of plutonium in vivo. In particular, Fe(III) have similar charge to ionic size ratios and hydrolysis properties. These similarities inspired a biomimetic approach to the development of preorganized multidentate sequestering agents for Pu(IV) based on the chelating units found in siderophores, naturally occurring highly selective Fe(III) sequestering agents. The aim of this project is to continue to study the coordination and solution behaviors of ligands for actinide decorporation and selective extraction based on siderophores. This project is the result of a collaborative effort in inorganic chemistry, synthetic organic chemistry, and actinide biology, and incorporates the design, synthesis, structural and thermodynamic characterization of ligands and their metal complexes with actinides and lanthanides and the evaluation of these compounds in metal ion separations. We use a variety of characterization techniques including spectrophotometric titrations, extractions, Extended X-ray Absorbance Fine Structure and X-ray diffraction.
Biography
Professor, born 1942; B. A. Reed College (1964); Ph. D. Northwestern University (1968); Sloan Fellow (1971); Visiting Professor, Stanford University (1973); Visiting Professor, Australian National University (1974); Miller Professor, Berkeley (1977); Visiting Professor, University Louis Pasteur, Strasbourg (1980); Guggenheim Fellow (1980); E. O. Lawrence Award (1984); Alexander von Humboldt Award for U.S. Senior Scientists (1992); ACS Alfred Bader Award in Bioinorganic Chemistry (1994); Chemistry Department Chairman (1993-1996); Member ACA, AAAS, ACS; Faculty Senior Scientist, Chemical Sciences Division, Lawrence Berkeley National Laboratory.
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