Larry morris

Heisenberg exchange coupling is a phenomenon that occurs when two or more unpaired spins are in energetic proximity and interact via an orbital mechanism. This phenomenon is exhibited in many molecules, compounds and complexes; however, I am interested in studying paramagnetic transition metals bonded to a single semiquinone moiety.  Semiquinones are bidentate, radical containing ligands. Transition metal cations of interest are Ni^II and Cr^III; these cations were chosen because when interacting with a semiquinone ligand, they produce ferromagnetic (parallel spin alignment) and antiferromagnetic (antiparallel spin alignment) exchange coupling, respectively.  If substituents are placed on the semiquinone ligand, then the unpaired spin density will be polarized either towards or away from the paramagnetic transition metal.  Locating the spin density in these transition metal-semiquinone complexes will aid in determining their chemical reactivity and the rational design of molecular magnetic materials.  A variety of techniques are employed to study these ligand-metal interactions including EPR spectroscopy, crystallography, theoretical calculations and magnetometry.