Date of Award
Master of Science
Sheng Dai, Konstantinos Vogiatzis
This thesis is mainly focused on studying molecular magnetism by inelastic neutron scattering (INS) and nuclear magnetic resonance (NMR) spectroscopy. Other techniques such as high-frequency electron paramagnetic resonance (HF-EPR) and DC magnetic susceptibility are also utilized to provide more comprehensive understanding. The sign and magnitude of axial zero-field splitting parameter D of Mn(TPP)X (H2TPP = tetraphenylporphyrin; X = Br and I) have been directly determined by INS and are consistent with the measurement of HF-EPR. Mn(TPP)F is EPR silent in both solid (5-290 K) and frozen solution (10 K in chloroform) state, making it different from its Br and I analogies. Studies of Mn(TPP)F suggest that molecules form a 1-D chain structure in solid-state through F- bridges, but extended research is needed to support this hypothesis. Ligand effect of a series of pseudo-tetrahedral CoII [positive two cobalt ion] complexes Co(EPh3)2X2 [cobalt triphenylphosphine chlorine] (E = P, X = CI, Br, I; E = As, X = I) was studied by variable-temperature and variable-magnetic-field INS. In this pseudo-tetrahedral CoII system, the anisotropy barriers do not change notably when the coordinating halide ligands change from lighter Cl to heaver Br and I. However, a significant increase of the axial anisotropy 2D value appears when substituting the phosphine with the arsine ligand. This work demonstrated that INS can provide opportunities to precisely probe the anisotropy barrier when it exceeds the range of HF-EPR. In addition, dynamics of group 10 metal complexes with macrocyclic amine N-heterocyclic carbene (NHC) ligands was studied by NMR.
Liu, Zhiming, "Studies of Molecular Magnetism and Dynamics by Inelastic Neutron Scattering and Nuclear Magnetic Resonance. " Master's Thesis, University of Tennessee, 2019.