The Relationship between NMR Chemical Shifts of Thermally Polarized and Hyperpolarized 89Y Complexes and Their Solution Structures

Recently developed dynamic nuclear polarization (DNP) technology offers the potential of increasing the NMR sensitivity of even rare nuclei for biological imaging applications. Hyperpolarized Y-89 is an ideal candidate because of its narrow NMR linewidth, favorable spin quantum number (I=1/2 ), and long longitudinal relaxation times (T-1). Strong NMR signals were detected in hyperpolarized Y-89 samples of a variety of yttrium complexes. A dataset of Y-89 NMR data composed of 23 complexes with polyaminocarboxylate ligands was obtained using hyperpolarized Y-89 measurements or H-1,Y-89-HMQC spectroscopy. These data were used to derive an empirical equation that describes the correlation between the Y-89 chemical shift and the chemical structure of the complexes. This empirical correlation serves as a guide for the design of Y-89 sensors. Relativistic (DKH2) DFT calculations were found to predict the experimental Y-89 chemical shifts to a rather good accuracy.