TY - JOUR
T1 - Nonpentacene Polarizing Agents with Improved Air Stability for Triplet Dynamic Nuclear Polarization at Room Temperature
AU - Kouno, Hironori
AU - Kawashima, Yusuke
AU - Tateishi, Kenichiro
AU - Uesaka, Tomohiro
AU - Kimizuka, Nobuo
AU - Yanai, Nobuhiro
N1 - Funding Information:
This work was partly supported by the PRESTO program on “Creation of Life Science Basis by Using Quantum Technology” from JST (grant number JPMJPR18GB), JSPS KAKENHI grant numbers JP17H04799, JP16H06513, and JP17J05046, and The Yoshida Foundation for the Promotion of Learning and Education. K.T. acknowledges partial support from the RIKEN Pioneering Project “Dynamic Structural Biology”.
Publisher Copyright:
© 2019 American Chemical Society.
PY - 2019/5/2
Y1 - 2019/5/2
N2 - Triplet dynamic nuclear polarization (triplet-DNP), a method to enhance nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) sensitivity using photoexcited triplet electrons, has great potential to hyperpolarize nuclear spins at room temperature. Since the first report of room-temperature triplet-DNP in 1990, pentacene has been the only and best option of triplet polarizing agent. However, the poor air stability of pentacene has severely limited the applicability of triplet-DNP. We report the first example of polarizing agents with significant air stability as well as high polarizing ability comparable to pentacene. The introduction of electron-withdrawing diaza-substitution to pentacene and tetracene reduces the lowest unoccupied molecular orbital level and endows much improved stability under the ambient conditions. Importantly, the diaza-substituted pentacene and tetracene offer similar, or even slightly better, 1 H NMR signal enhancement compared with pentacene in the prototypical triplet-DNP test using p-terphenyl crystals. This work removes one of the largest obstacles toward the application of triplet-DNP for the hyperpolarization of biological molecules.
AB - Triplet dynamic nuclear polarization (triplet-DNP), a method to enhance nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) sensitivity using photoexcited triplet electrons, has great potential to hyperpolarize nuclear spins at room temperature. Since the first report of room-temperature triplet-DNP in 1990, pentacene has been the only and best option of triplet polarizing agent. However, the poor air stability of pentacene has severely limited the applicability of triplet-DNP. We report the first example of polarizing agents with significant air stability as well as high polarizing ability comparable to pentacene. The introduction of electron-withdrawing diaza-substitution to pentacene and tetracene reduces the lowest unoccupied molecular orbital level and endows much improved stability under the ambient conditions. Importantly, the diaza-substituted pentacene and tetracene offer similar, or even slightly better, 1 H NMR signal enhancement compared with pentacene in the prototypical triplet-DNP test using p-terphenyl crystals. This work removes one of the largest obstacles toward the application of triplet-DNP for the hyperpolarization of biological molecules.
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U2 - 10.1021/acs.jpclett.9b00480
DO - 10.1021/acs.jpclett.9b00480
M3 - Article
C2 - 30933529
AN - SCOPUS:85065140348
SN - 1948-7185
VL - 10
SP - 2208
EP - 2213
JO - Journal of Physical Chemistry Letters
JF - Journal of Physical Chemistry Letters
IS - 9
ER -