Type of Document	Dissertation
Author	Zipse, David
Author's Email Address	dzipse@chem.fsu.edu
URN	etd-09092004-172738
Title	Excited States and Electrical Properties of Fe(III) and V(IV) Clusters
Degree	Doctor of Philosophy
Department	Chemistry and Biochemistry, Department of
Advisory Committee	Advisor Name Title Naresh Dalal Committee Chair Kenneth Goldsby Committee Member Oliver Steinbock Committee Member Stephan von Molnar Committee Member
Keywords	Electrical Transport Magnetic Resonance Single Molecule Magnets Excited States
Date of Defense	2004-07-12
Availability	unrestricted
Abstract This dissertation describes the characterization of the magnetic and electrical properties of a unique class of transition metal complexes known as single-molecule magnets (SMMs). The experimental work of this dissertation is focused on the SMMs [(C6H15N3)6Fe8O2(OH)12]Br7(H2O)Br •8H2O (Fe8Br8), K6[V15As6O42(H2O)] • 8H2O (V15), as well as the analogous cluster compounds [NH(C2H5)3]4[V84.5+V44+As8O40(H2O)]•H2O (V12) and [(C6H15N3)4Fe4O(OH)5]I7 • 2.5 H2O (Fe4). SMMs are transition metal cluster complexes that exhibit single-molecule hysteresis and quantum tunneling of the magnetization (QTM). Fe8Br8 is one of the best characterized SMMs with its ground state spin S = 10, while V15 exhibits SMM behavior with a spin of S = ½. The foci of our investigations were the single-spin model in Fe8Br8, the basic electrical properties of V15 and V12, and the synthesis and characterization of the analogous cluster compound Fe4. Chapter 2 describes the characterization (magnetic parameters and energetic location) of the S = 9 excited state in Fe8Br8 by high field electron paramagnetic resonance, while Chapter 3 focuses on the measurement of the unpaired electron density distribution in Fe8Br8 as determined by 81Br solid state NMR. Both of these chapters bring into question the validity of the currently accepted single-spin model for Fe8Br8. Chapter 4 details the dielectric relaxation properties of V15 as determined by an ac impedance method. The semiconductive behavior of both V15 and V12 is described in Chapter 5, along with its comparison to optical absorption measurements, while the synthesis and magnetic characterization of the new cluster compound Fe4 is described in Chapter 6. The summary and main conclusions are presented in Chapter 7. The results presented herein should make a significant contribution to the fundamental understanding of the mechanism of quantum tunneling in Fe8Br8 and the basic electrical properties of SMMs for their potential use in future applications.
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