Paramagnetic Transition Metal Complexes for ParaCEST and ParaSHIFT Magnetic Resonance Applications.

摘要

Biomedical diagnostic methods including magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) can be employed to help study disease states as they develop. Both techniques rely on NMR spectroscopic principles to generate data. To overcome the inherent low sensitivity of NMR techniques, contrast agents utilizing paramagnetic metal ions have been long studied. These agents make use of the properties of the metal ion, such as the changes to electronic relaxation time that can be modulated through coordination chemistry, to enhance signal. The use of transition metal ions as contrast agents has received renewed interest recently.;The research in chapter 1 involves imidazole-appended oxa-azamacrocycle complexes of divalent iron, cobalt and nickel to generate contrast through chemical exchange saturation transfer (CEST). Results suggest that these ligands do not produce Fe(II) complexes that are sufficiently stable at neutral pH for generating a CEST effect, while the Co(II) and Ni(II) complexes generate optimum peak intensity and chemical exchange rates at physiologically relevant pH range (7.2).;Chapter 2 entails studies of the cage complex 1,8-dinitro-3,6,10,13,16,19-hexaazabicyclo-(6,6,6)eicosane cobalt trichloride, as an encapsulated metal ion. The Co(III) complex is reduced to the Co(II) complex, generating a paramagnetic cage complex with discernable resonances that were studied for paraSHIFT MRS application. Further, the synthesis of the complex was implemented into a teaching laboratory to demonstrate to inorganic chemistry students how paramagnetic metal ions can affect proton NMR spectra.;The third and final chapter of this thesis presents two different N-heterocyclic pendent groups, N-methylimidazole and 6-methyl methyl ester benzimidazole, which are attached to a diazacrown macrocycle. Complexes of Fe(II), Co(II) and Ni(II) are studied for applications in both MRI and MRS Complexes are compared to the complexes studied in chapter 1 that have imidazole pendents and also to amide and benzimidazole pendent groups that have been studied previously in the Morrow Lab.