The group is interested in designing transition metal complexes on predetermined shapes. Our particular focus has been on producing small molecules with helical shapes that can be used as supramolecular building blocks and asymmetric catalysts. One simple approach we have taken is to use a chiral backbone to support polyaromatic sidearms that can overlap to form mononuclear helical molecules. A general outline of some of this work is shown in the figure below, where the backbones are indicated in blue and the sidearms in red.
We have been successful in synthesizing a number of helical complexes using our design: some have one stable helical form, while others shows interconversion between diastereomeric right and left handed helices.
Two views of a left handed helical iron (II) complex.
Left Handed (M)
A number of different morphologies are seen for dinuclear complexes. Two metals can coordinate to a single ligand to form single stranded helices with or without bridging between the metal ions.
We are also able to generate polynuclear complexes by incorporating additional functionality into the ligands. Acid-functionalized salen ligands can generate a number of different types of complex depending on the conditions used for synthesis and crystallization.
In recent years, there has been considerable effort directed toward the use of chiral metal complexes as catalysts for a wide variety of asymmetric transformations. For example, it is often possible to transform an achiral substrate into a chiral product consisting almost entirely of one enantiomer. This type of transformation is extremely important for the synthesis of drugs and natural products, which usually contain at least one chiral center.
One focus of the group is the development of new transition-metal catalysts for stereoselective transformations, with a particularly emphasis on traditionally difficult oxidations: epoxidations, sulfoxidations, and hydroxylations.
Sustainable or ‘green’ chemistry is an interest in my research and teaching. Inorganic Techniques (CHM 657) is a laboratory course that offers several experiments in green chemistry and Case Studies in Green Chemistry (CHM 766) is a group-learning class that studies sustainable practices in the chemical industry.
1) Wiznycia, Alexander V.; Desper, John; Levy, Christopher J. “Zinc and iron complexes of a helix-directing (1R,2R)-cyclohexyl salen ligand with phenanthryl sidearms” Can. J. Chem. 2009, 87, 224-231.
2) Lalehzari, Azadeh; Desper, John; Levy, Christopher J. “Double-Stranded Monohelical Complexes from an Unsymmetrical Chiral Schiff-Base Ligand” Inorg. Chem. 2008, 47, 1120-1126.
3) Prema, Dipesh; Wiznycia, Alexander V.; Scott, Benjamin M. T.; Hilborn, Jessica; Desper, John; Levy, Christopher J. “Dinuclear zinc(II) complexes of symmetric Schiff-base ligands with extended quinoline sidearms” Dalton Trans. 2007, 4788-4796.
4) Wiznycia, Alexander V.; Desper, John; Levy, Christopher J. “Iron(II) and zinc(II) monohelical binaphthyl-salen complexes with overlapping benz[a]anthryl sidearms” Dalton Trans. 2007, 1520-1527.
5) Wiznycia, Alexander V.; Desper, John; Levy, Christopher J. “Monohelical Iron(II) and Zinc(II) Complexes of a (1R,2R)-Cyclohexyl Salen Ligand with Benz[a]anthryl Sidearms” Inorg. Chem. 2006, 45, 10034-10036.
6) Wiznycia, Alexander V.; Desper, John; Levy, Christopher J. “Iron(II) and Zinc(II) Monohelical Binaphthyl Salen Complexes” Chem. Commun. 2005, 4693.