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Heteronuclear Cross‐Relaxation Effects in the NMR Spectroscopy of Hyperpolarized Targets
Author(s) -
Donovan Kevin J.,
Lupulescu Adonis,
Frydman Lucio
Publication year - 2014
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201300857
Subject(s) - heteronuclear molecule , nuclear magnetic resonance spectroscopy , chemistry , relaxation (psychology) , nuclear magnetic resonance , transverse relaxation optimized spectroscopy , spectroscopy , spin–lattice relaxation , chemical physics , fluorine 19 nmr , stereochemistry , physics , psychology , social psychology , quantum mechanics , nuclear quadrupole resonance
Dissolution dynamic nuclear polarization (DNP) enables high‐sensitivity solution‐phase NMR experiments on long‐lived nuclear spin species such as 15 N and 13 C. This report explores certain features arising in solution‐state 1 H NMR upon polarizing low‐γ nuclear species. Following solid‐state hyperpolarization of both 13 C and 1 H, solution‐phase 1 H NMR experiments on dissolved samples revealed transient effects, whereby peaks arising from protons bonded to the naturally occurring 13 C nuclei appeared larger than the typically dominant 12 C‐bonded 1 H resonances. This enhancement of the satellite peaks was examined in detail with respect to a variety of mechanisms that could potentially explain this observation. Both two‐ and three‐spin phenomena active in the solid state could lead to this kind of effect; still, experimental observations revealed that the enhancement originates from 13 C→ 1 H polarization‐transfer processes active in the liquid state. Kinetic equations based on modified heteronuclear cross‐relaxation models were examined, and found to well describe the distinct patterns of growth and decay shown by the 13 C‐bound 1 H NMR satellite resonances. The dynamics of these novel cross‐relaxation phenomena were determined, and their potential usefulness as tools for investigating hyperpolarized ensembles and for obtaining enhanced‐sensitivity 1 H NMR traces was explored.