Title Page
Contents
LIST OF ABBREVIATIONS 13
ABSTRACT 15
Ⅰ. Introduction 17
1.1. NMR Spectroscopy 17
1.2. Hyperpolarization 19
1.2.1. para-Hydrogen induced polarization (PHIP) 20
1.2.2. SABRE 21
1.2.3. New iridium catalysts for SABRE 23
1.2.4. Target substrates for SABRE 24
Ⅱ. Method 25
2.1. Generation of 50% para-Hydrogen 25
2.2. SABRE 25
2.2.1. SABRE with monodentate N-heterocyclic carbene (NHC) based iridium catalysts (Figure 4) 26
2.2.2. SABRE with bidentate NHC based iridium catalysts (Figure 5) 27
2.3. Calculation of NMR polarization enhancement 28
Ⅲ. Results and Discussion 30
3.1. Synthesis of NHC ligand and iridium complex 30
3.1.1. Preparation of monodentate NHC-based iridium catalysts 30
3.1.2. Preparation of bidentate NHC-based iridium catalyst 32
3.2. SABRE using NHC-based Iridium complexes 34
3.2.1. The efficiency of monodentate NHC-based iridium catalyst for SABRE 34
3.2.2. The efficiency of bidentate NHC-based iridium catalyst for SABRE 43
Ⅳ. Conclusion 49
Ⅴ. Experimental Section 51
5.1. General information 51
5.2. Reagent 52
5.3. Synthesis 54
5.4. Spectrum 60
Ⅵ. Reference 70
국문요약 74
Table 1. The synthesis of bis-(NHC) ligands 32
Table 2. The synthesis of iridium catalysts with bis-(NHC) ligands 33
Table 3. Average axial and equatorial bond lengths after optimization of catalyst-substrate(5)-parahydrogen complexes 43
Figure 1. Nuclear spin states in response to an applied magnetic field(B₀) (a) and the spin-state energy separation as a function of the applied magnetic field (b) 18
Figure 2. The concept of hyperpolarization. Populations of nuclear spin states in thermal equilibrium (left) and hyperpolarized state (right) 20
Figure 3. The spin configuration of the hydrogen (a) and Equilibrium concentration profile of both ortho-H₂ and para-H₂ at different temperatures (b) 21
Figure 4. The structures of iridium catalysts with monodentate N-heterocyclic carbene ligands 26
Figure 5. The structures of iridium catalysts with bidentate N-heterocyclic carbene ligands 27
Figure 6. Schematic diagram of a home-built para-hydrogen generator. 29
Figure 7. [Ir(COD)(IMes)Cl] (1) catalyst structure (a), Substrates for SABRE with catalyst 1 and its polarization number with different substrates and different... 36
Figure 8. Catalyst 2 structure (a), Substrates for SABRE with catalyst 2 and its polarization number with different substrates and different magnetic field (b)... 38
Figure 9. Catalyst 3 structure (a), Substrates for SABRE with catalyst 3 and its polarization number with different substrates and different magnetic field (b)... 40
Figure 10. Polarized (black color)/unpolarized (red color) spectra of isonicotinic acid hydrazide employing catalyst 3 41
Figure 11. Optimized structure of activated iridium catalyst with substrate and para-H₂ 42
Figure 12. The structures of substrates (a) and ¹H NMR signal amplification at the specific positions of substrates employing catalyst 4 (b), 5 (c), and 6 (d) 45
Figure 13. ¹H spectrum of nomal (black color) and hyperpolarized nicotinic acid (red color) employing the catalysts 4 (b),5 (c), and 6 (d) under various magnetic field 46
Figure 14. The structure of caffeine (a) and amplification of caffeine depending on catalyst concentration (b) 47
Figure 15. ¹H spectrum of normal (black color) and hyperpolarized caffeine (red color) employing the catalysts 4 (a),5 (b), and 6 (c) under earth's magnetic field 48
Scheme 3. General SABRE mechanism 22
Scheme 4. The reaction of IMes ligand and [Ir(COD)Cl]₂ 31
Scheme 5. The synthesis of dibenzyl (benz)imidazolium iridium complexes 31
Equation 1. Calculation of ¹H polarization enhancement (ε). 28