Determination of long-range scalar 1H-1H coupling constants responsible for polarization transfer in SABRE
Abstract
SABRE (Signal Amplification By Reversible Exchange) nuclear spin hyperpolarization method can provide strongly enhanced NMR signals as a result of the reversible association of small molecules with para-hydrogen (p-H2) at an iridium metal complex. The conversion of p-H2 singlet order to enhanced substrate proton magnetization within such complex is driven by the scalar coupling interactions between the p-H2 derived hydrides and substrate nuclear spins. In the present study these long-range homonuclear couplings are experimentally determined for several SABRE substrates using an NMR pulse sequence for coherent hyperpolarization transfer at high magnetic field. Pyridine and pyrazine derivatives appear to have a similar ∼1.2 Hz 4J coupling to p-H2 derived hydrides for their ortho protons, and a much lower 5J coupling for their meta protons. Interestingly, the 4J hydride-substrate coupling for five-membered N-heterocyclic substrates is well below 1 Hz.
- Publication:
-
Journal of Magnetic Resonance
- Pub Date:
- April 2016
- DOI:
- 10.1016/j.jmr.2016.01.012
- Bibcode:
- 2016JMagR.265...59E
- Keywords:
-
- Hyperpolarization;
- SABRE;
- J-modulation