25-30 August 2019
Henry Ford Building
Europe/Berlin timezone

Triplet Dynamic Nuclear Polarization of Metal-Organic Frameworks

Not scheduled
4h
Harnack House and Henry Ford Building

Harnack House and Henry Ford Building

Board: 134
Poster Posters

Speaker

Mr Saiya Fujiwara (Department of Chemistry and Biochemistry, Graduate School of Engineering, Center for Molecular Systems (CMS), Kyushu University)

Description

Nuclear magnetic resonance (NMR) spectroscopy and magnetic resonance imaging (MRI) are versatile methods in modern chemistry and biology fields. Nevertheless, they suffer from intrinsically limited sensitivity due to the low nuclear spin polarization at ambient temperature. One of the promising methods to overcome this limitation is dynamic nuclear polarization (DNP). In particular, DNP based on photoexcited triplet electrons (triplet-DNP) has the potential to hyperpolarize nuclear spins of target substrates in the low magnetic field at room temperature. Room-temperature triplet-DNP has provided high enhancements in organic crystals such as p-terphenyl. However, it remains difficult for such organic crystals to accommodate target molecules to be monitored. While amorphous solids such as o-terphenyl were employed as host matrices to accommodate target substrates, the flexible structure requires the cooling of the sample for triplet-DNP (∼120 K). Therefore, despite these efforts, it remains a grand challenge to develop a room-temperature triplet-DNP system with accessibility for polarizing targets. In this work, we report the first example of triplet-DNP of nanoporous metal-organic frameworks (J. Am. Chem. Soc. 2018, 140, 15606-15610). We modified the typical polarizing agent pentacene with metal-coordinating carboxylate moieties (4,4′-(pentacene-6,13-diyl)dibenzoic acid (PDBA)) for its introduction into MOFs. A relatively long 1H T1 has been reported for a prototypical diamagnetic Zn2+-based MOF, [Zn(MeIM)2]n (ZIF-8; MeIM = 2-methylimidazolate). A partial deuteration of MeIM ligands allows the elongation of T1 of partially deuterated D-ZIF-8. Polarization transfer from PDBA triplet electrons to 1H nuclei in D-ZIF-8 resulted in a clear enhancement (ε = 58) of 1H NMR signals of D-ZIF-8 at a low magnetic field of 0.67 T and room temperature.

Primary authors

Mr Saiya Fujiwara (Department of Chemistry and Biochemistry, Graduate School of Engineering, Center for Molecular Systems (CMS), Kyushu University) Dr Tateishi Kenichiro (Cluster for Pioneering Research, RIKEN, RIKEN Nishina Center for Accelerator-Based Science) Prof. Uesaka Tomohiro (Cluster for Pioneering Research, RIKEN, RIKEN Nishina Center for Accelerator-Based Science) Ms Ideta Keiko (Institute for Materials Chemistry and Engineering, Kyushu University) Prof. Kimizuka Nobuo (Department of Chemistry and Biochemistry, Graduate School of Engineering, Center for Molecular Systems (CMS), Kyushu University) Prof. Yanai Nobuhiro (Department of Chemistry and Biochemistry, Graduate School of Engineering, Center for Molecular Systems (CMS), Kyushu University)

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