Unusual Physical Properties of Molybdenum Tris-Dithiolenes

Posted May 7th, 2010 at 2:42 pm.

Anna Merkle

Mentor: Dr. Sharon Burgmayer

Molybdenum tris-dithiolene compounds, Figure 1, have been researched for many years. These compounds are models for molybdenum cofactors in molybdenum enzymes, which are responsible for electron transfer reactions in all organisms. Electrons hold the bonds between atoms together, and are therefore important for chemists to understand. The configuration of electrons, which can be paired or unpaired, determines the physical properties of molecules. Unpaired electrons cause magnetic behavior to occur while unpaired electrons have not magnetic behavior. A molecule with unpaired electrons is considered paramagnetic while a molecule with only paired electrons is considered diamagnetic.

Crystal Field Theory predicts molybdenum tris-dithiolene to be a diamagnetic compound due to its known trigonal prismatic geometry as shown in Figure 2. However, when these compounds are placed in a magnetic field they are shown to be paramagnetic — that is they are consistent with compounds that have unpaired electrons. The majority of the summer research will focus on this unusual physical property and the reasons behind the unusual behavior.

In order to focus on molybdenum tris-dithiolenes and their magnetic properties the complex molecules must be synthesized. Different substituents (R-groups) will be analyzed to see whether the difference in size causes unexpected magnetism to occur in the molecules. After these molecules are synthesized the lab will try and crystallize the molecules in order to characterize the molecules using X-ray crystallography and X-ray diffraction. Previously there has been very little success in crystallizing these complex compounds and thus no concrete results as to why the molecules are paramagnetic. Hopefully this summer there will be better success in crystallizing the molecules. The structure of the complex molecules is most likely what is causing the unusual paramagnetic readings, and completely understanding the structure of the molecules will help the lab interpret the unusual physical property observed.










Figure 1: Molybdenum tris-dithiolene.

Figure 2: A trigonal prismatic structure.

Filed under: 2005,Burgmayer, Dr. Sharon,Merkle, Anna by Ann Dixon

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