Lattice Dynamics and Bistability of Electronically Labile Complexes

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This award in the Inorganic, Bioinorganic, and Organometallic Chemistry Program supports research by Dr. David N. Hendrickson of the Chemistry Department, University of California at San Diego, on lattice dynamics and bistability of electronically labile complexes. Detailed studies will be carried out on transition metal complexes that have two or more electronic states that are close in energy. For compounds in which vibrational modes are closely coupled with electronic modes, changes in crystal lattice parameters such as those caused by modifying solvent or counter ions can result in spin-crossover or phase transitions in response to changes in light or other external parameters. A primary goal of this project is to characterize magnetic bistability in molecular species. Specifically the magnetic behavior of a series of dodecamanganese-oxo-carboxylate complexes will be probed to characterize the factors affecting the potential-energy barrier and the mechanism of resonant magnetization tunneling in these single-molecule magnets compounds. Investigation of photoinduced valence tautomerization in cobalt complexes and spin crossover in opically sensitive iron complexes will continue. Methods will then be sought to attach these species to a functionalized surface or polymer. The long-term goal of this project is to develop molecules or collections of molecules for use in electronic circuits and devices. In this research, compounds containing a small number of metal atoms will be tested for sensitivity and specificity of response to external physical stimuli. Only a few examples of molecules in which the magnetic field changes in response to changes in external magnetic field are known. In this investigation additional examples will be prepared and the factors that control their behavior will be determined. These results can lead to nanoscale devices which change spin, number of electrons, or magnetic properties in response to electric, magnetic, optical, or thermal changes. Many applications as switches or for information storage can be envisioned. In addition to the scientific content, an important aspect of this project is the training of young scientists.