Terminal Diazirines Enable Reverse Polarization Transfer from ¹⁵N₂ Singlets

Abstract

Diazirine moieties are chemically stable and have been incorporated into biomolecules without impediment of biological activity.T he 15 N 2 labeled diazirines are appealing motifs for hyperpolarization supporting relaxation protected states with long-lived lifetimes.The (-CH 15 N 2 )diazirine groups investigated here are analogues to methyl groups,w hich provides the opportunity to transfer polarization stored on arelaxation protected (-CH 15 N 2 )moiety to 1 H, thus combining the advantages of long lifetimes of 15 Np olarization with superior sensitivity of 1 Hdetection. Despite the proximity of 1 H to 15 Nnuclei in the diazirine moiety, 15 NT 1 times of up to (4.6 AE 0.4) min and singlet lifetimes T s of up to (17.5 AE 3.8) min are observed. Furthermore,w ef ound terminal diazirines to support hyperpolarized 1 H 2 singlet states in CH 2 groups of chiral molecules.T he singlet lifetime of 1 Hs inglets is up to (9.2 AE 1.8) min, thus exceeding 1 HT 1 relaxation time (at 8.45 T) by afactor of % 100.

<i>Geminal</i> parahydrogen-induced polarization: accumulating long-lived singlet order on methylene proton pairs

“…There are two main modes of PHIP: (i) in hydrogenative PHIP, the strongly enhanced nuclear singlet order of para-enriched H 2 gas is substantially conserved through a pairwise catalytic transfer of the hydrogen pair onto a product molecule (Bowers and Weitekamp, 1987;Natterer and Bargon, 1997;Reineri et al, 2015). The high degree of nuclear singlet order in the hydrogenation product is converted into enhanced nuclear magnetization by symmetry-breaking nuclear spin interactions; (ii) in the sig-L. Dagys et al: Geminal PHIP: accumulating long-lived singlet order on methylene protons nal amplification by reversible exchange (SABRE) method, reversible chemical processes are used to transfer the nuclear singlet order onto the target molecules (Adams et al, 2009;Theis et al, 2014;Truong et al, 2015;Lindale et al, 2019;Zhang et al, 2019). PHIP has several advantages over alternative hyperpolarization techniques, such as its low cost, its compact and simple equipment requirements, and its ability to produce relatively large amounts of hyperpolarized material in a short time.…”

Singlet-Contrast Magnetic Resonance Imaging

“…We expect this imaging method to be extended to alternative PHIP systems 64 , or other nuclear spin species, e.g. 15 N or 13 C singlet pairs [65][66][67][68] , which are known to be long-lived in aqueous solution.…”

Infinite-order perturbative treatment for quantum evolution with exchange

“…On the forefront of magnetic resonance techniques are hyperpolarization methods (11)(12)(13)(14)(15), which overcome the intrinsically low signal-to-noise limits by distilling spin order from an external source. Of particular interest over the past decade is signal amplification by reversible exchange (SABRE) (5,(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31), in which the singlet order of parahydrogen is converted into observable magnetization or more complex spin states on target ligands during transient interactions with an iridium catalyst ( Fig. 1A).…”