Heterogeneous catalysts for NMR/MRI enhancement via signal amplification by reversible exchange (SABRE)
Heterogeneous iridium catalysts for nuclear spin polarization enhancement in solution via signal amplification by reversible exchange are provided. Also provided are methods for preparing heterogeneous iridium catalysts, and methods of using heterogeneous iridium catalysts for nuclear spin polarization enhancement in solution via signal amplification by reversible exchange.
1. A heterogeneous catalyst of formula (I),
wherein,
is a solid support;
L is a bond or a linker; and
Cat has formula:
wherein R 1 and R 2 are each independently selected from aryl, heteroaryl, arylalkyl, heteroarylalkyl, wherein said aryl, heteroaryl, arylalkyl, and heteroarylalkyl are each independently unsubstituted or substituted with one or more suitable substituents; R 3 and R 4 are each independently selected from hydrogen and alkyl; R 5 is halogen or pyridinyl, wherein said pyridinyl is unsubstituted or substituted with one or more suitable substituents; provided that one R 1 , R 2 , R 3 , R 4 , and R 5 links to the solid support via L;
wherein each suitable substituent is independently selected from the group consisting of perfluoroalkyl, perfluoroalkoxy, alkyl, alkenyl, alkynyl, hydroxy, halo, oxo, mercapto, alkylthio, alkoxy, nitro, azidealkyl, aryl, heteroaryl, aryloxy, heteroaryloxy', aralkyl, heteroaralkyl, aralkoxy, heteroaralkoxy, HO—(C═O)—, heterocylic, cycloalkyl, amino, alkylamino, dialkylamino, carbamoyl, alkylcarbonyl, alkylcarbonyloxy, alkoxycarbonyl, alkylaminocarbonyl, dialkylamino carbonyl, arylcarbonyl, aryloxycarbonyl, alkylsulfonyl, and arylsulfonyl.
2. The catalyst of claim 1 , wherein formula (II) has formula:
where X − is a non-coordinating anion.
3. The catalyst of claim 1 , wherein formula (II) has formula:
4. The catalyst of claim 1 , wherein the solid support is selected from a nanoparticle, a titanium dioxide nanoparticle, silica, a polymer microbead, and a polystyrene microbead.
5. The catalyst of claim 1 , wherein L is a bond.
6. The catalyst of claim 1 , wherein L is a linker, wherein the linker is derived from an amino acid or 4-dimethylamino-pyridine.
7. The catalyst of claim 1 , wherein R 1 is mesityl.
8. The catalyst of claim 1 , wherein R 2 is mesityl.
9. The catalyst of claim 1 , wherein R 3 and R 4 are each hydrogen.
10. The catalyst of claim 1 , wherein R 5 is chloro.
11. The catalyst of claim 1 , wherein R 5 is an unsubstituted or substituted pyridinyl.
12. The catalyst of claim 1 , having formula (I-a),
wherein Mes is mesityl; and X − is a non-coordinating anion.
13. The catalyst of claim 1 , having formula (I-b),
wherein Mes is mesityl; and X − is a non-coordinating anion.
14. The catalyst of claim 1 , having formula (I-c),
wherein Mes is mesityl; and X − is a non-coordinating anion.
15. The catalyst of claim 14 , wherein the solid support is a TiO 2 nanoparticle.
16. The catalyst of claim 1 , having formula (I-d),
wherein Mes is mesityl; X − is a non-coordinating anion; and the solid support is polystyrene.
17. The catalyst of claim 1 , having formula (I-e),
wherein Mes is mesityl; and X − is a non-coordinating anion.
18. The catalyst of claim 1 , having formula (I-f),
wherein Mes is mesityl; X − is a non-coordinating anion; and the solid support is a TiO 2 nanoparticle.