Bis-Gadolinium Complexes for Solid Effect and Cross Effect Dynamic Nuclear Polarization.
High-spin complexes act as polarizing agents (PAs) for dynamic nuclear polarization (DNP) in solid-state NMR spectroscopy and feature promising aspects towards biomolecular DNP. We present a study on bis(Gd-chelate)s which enable cross effect (CE) DNP owing to spatial confinement of two dipolar-coupled electron spins. Their well-defined Gd⋅⋅⋅Gd distances in the range of 1.2-3.4 nm allowed us to elucidate the Gd⋅⋅⋅Gd distance dependence of the DNP mechanism and NMR signal enhancement. We found that Gd⋅⋅⋅Gd distances above 2.1 nm result in solid effect DNP while distances between 1.2 and 2.1 nm enable CE for1H,13C, and15N nuclear spins. We compare 263 GHz electron paramagnetic resonance (EPR) spectra with the obtained DNP field profiles and discuss possible CE matching conditions within the high-spin system and the influence of dipolar broadening of the EPR signal. Our findings foster the understanding of the CE mechanism and the design of high-spin PAs for specific applications of DNP.
Goethe-Universität Frankfurt am Main, Institut für Physikalische und Theoretische Chemie, Institut für Biophysikalische Chemie und Biomolekulares Magnetresonanzzentrum (BMRZ), Max-von-Laue-Strasse 7-9, 60438, Frankfurt am Main, Germany.
Monu
0000-0001-5564-2578
M
Kaushik
Fakultät für Chemie und Centrum für Molekulare Materialien (CM2), Universität Bielefeld, Universitätsstrasse 25, 33615, Bielefeld, Germany.
Mian
0000-0001-6943-6636
M
Qi
Fakultät für Chemie und Centrum für Molekulare Materialien (CM2), Universität Bielefeld, Universitätsstrasse 25, 33615, Bielefeld, Germany.
Adelheid
0000-0001-8453-1439
A
Godt
Goethe-Universität Frankfurt am Main, Institut für Physikalische und Theoretische Chemie, Institut für Biophysikalische Chemie und Biomolekulares Magnetresonanzzentrum (BMRZ), Max-von-Laue-Strasse 7-9, 60438, Frankfurt am Main, Germany.
Björn
0000-0003-3937-9137
B
Corzilius
cross effect; dynamic nuclear polarization; gadolinium complexes; polarizing agent; solid-state NMR spectroscopy