Synthesis and Characterization of Transition Metal and Main Group Complexes with Unusual Bonding and Physical Properties

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With the support of the Chemical Synthesis Program of the Chemistry Division, Professor Philip Power and his group at the Chemistry Department at the University of California-Davis will investigate the chemical and physical properties of low-coordinate transition and main group complexes stabilized by large ligands. This award will allow exploration of the synthesis of new examples of stable two-coordinate, open-shell transition metal species having d(1)-d(9) electron configurations. Several new types of ligands will be used to stabilize them making use of a combination of steric and dispersive forces. The new, linear complexes will have increased metal accessibility and high reactivity because of the low number of metal ligands. The linear coordination will also exert a powerful effect on their magnetic properties and their ability to exhibit single molecule magnetism (SMM). In essence, their linear geometry will maximize orbital contributions to the magnetic moment. This will have a large effect on the extent of zero-field splitting and hence the barriers to spin-reversal. The factors that affect the barrier to spin reversal (ligand, metal oxidation state etc.) will be investigated systematically to maximize it and induce SMM at room temperature. The transition metal work will be paralleled by work on low-oxidation state main group complexes with similar ligands. The primary objective is an understanding on how dispersion forces between the ligands affect the structures of the compounds by imposing specific geometries in both the main group and transition metal species. A magnetic molecule (i. e., a molecule containing unpaired electrons) can behave, in principle, like an ordinary bar magnet if the spins of the individual unpaired (miniature bar magnets) electrons are aligned and kept aligned in a specific direction. In practice such behavior is unknown at room temperature because the spins of the electrons can flip rapidly between opposite directions such that permanent magnetism is lost. The design of molecules that maximize the spin flip barrier sufficiently to enable the molecular magnets to maintain their alignment at room temperature is a formidable problem. Overcoming this difficulty will impact numerous physical phenomena that depend on electromagnetic effects. The proposed research will help to understand the factors that control the barrier by a systematic investigation of how the atoms or groups of atoms attached to the metal affect the barriers to spin flip. The research will also involve the training of several undergraduate, graduate and post-doctoral students in a wide spectrum of physico-chemical techniques. Students will acquire skills ranging from the synthesis of highly air and moisture sensitive compounds to conduction sophisticated investigations of magnetic properties. Students will also be exposed to national and international collaborations to broaden their experience and education.