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Extended Metal Atom Chains (EMACs) are compounds that consist of three or more metal atoms that are directly bonded with the support of equatorial organic ligands. This dissertation is focused on the high frequency electron magnetic resonance study of trimetal complexes, the simplest form of EMACs before moving to study of longer chains. Chapter 3 presents the detailed cw-EPR and ac/dc magnetic susceptibility studies of symmetrical trichromium Cr3(dpa)4Cl2. Large negative zero-field splitting parameter D and frequency dependence of imaginary part of magnetic susceptibility indicate the single molecule magnet nature of this complex. The spin dynamics in Cr3(dpa)4Cl2 is studied in Chapter 4, which revealed the longest spin spin relaxation time T2 reported so far in concentrated molecular magnet. The strong angular dependence of T2 was also identified for the first time, providing us a unique way of tuning T2 by adjusting the orientation of magnetic field relative to the sample crystal. Chapter 5 describes the detailed cw-EPR study of an unsymmetrical trichromium compound Cr3(dpa)4ClBF4. Very similar magnetic properties were found as compared to its parent symmetrical counterpart Cr3(dpa)4Cl2 and the origin of this similarity was explored experimentally and theoretically from DFT calculations. Chapter 6 discusses the cw-EPR results on hetermetallic complexes CrCrMn(dpa)4Cl2 and MoMoMn(dpa)4Cl2. It was found that the seemly innocent diamagnetic Cr Cr and Mo Mo units are actually playing an important role in influencing the magnetic properties of Mn2+ center. Chapter 7 displays our efforts to expand the one dimensional trimetal complexes into multi-dimensions Prussian blue analogues through the [Fe/Co(CN)6]3- cyanide linkage. Interesting electronic and magnetic properties will be presented. Chapter 8 describes a summary of main results, which should contribute to the advancement and fundamental understanding of EMACs.
Anisotropy, Electron Paramagnetic Resonance, Magnetic Susceptibility, Single Molecule Magnet, Spin Crossover, Zero Field Splitting
Date of Defense
March 4, 2013.
A Dissertation submitted to the Department of Chemistry and Biochemistry in partial fulfillment of the requirements for the degree of Doctor of Philosophy.
Includes bibliographical references.
Naresh S. Dalal, Professor Directing Dissertation; James S. Brooks, University Representative; Mykhailo Shatruk, Committee Member; Sir Harold W. Kroto, Committee Member.
Florida State University
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