Reversible hyperpolarization of ketoisocaproate using sulfoxide-containing polarization transfer catalysts

TY - JOUR

T1 - Reversible hyperpolarization of ketoisocaproate using sulfoxide-containing polarization transfer catalysts

AU - Tickner, Benjamin

AU - Ahwal, Fadi

AU - Whitwood, Adrian C.

AU - Duckett, Simon B.

N1 - © 2020 The Authors

PY - 2020/11/26

Y1 - 2020/11/26

N2 - The substrate scope of sulfoxide-containing magnetisation transfer catalysts is extended to hyperpolarize α-ketoisocaproate and α-ketoisocaproate-1-[13C]. This is achieved by forming [Ir(H)2(κ2-ketoisocaproate)(N-heterocyclic carbene)(sulfoxide)] which transfers latent magnetism from p-H2 via the signal amplification by reversible exchange (SABRE) process. The effect of polarization transfer field on the formation of enhanced 13C magnetization is evaluated. Consequently, performing SABRE in a 0.5 µT field enabled most efficient magnetisation transfer. 13C NMR signals for α-ketoisocaproate-1-[13C] in methanol-d4 are up to 985-fold more intense than their traditional Boltzmann derived signal intensity (0.8% 13C polarisation). Single crystal X-ray diffraction reveals the formation of the novel catalyst decomposition products [Ir(µ-H)(H)2(IMes)(SO(Ph)(Me)2)]2 and [(Ir(H)2(IMes)(SO(Me)2))2(µ-S)] when the sulfoxides methylphenylsulfoxide and dimethylsulfoxide are used respectively.

AB - The substrate scope of sulfoxide-containing magnetisation transfer catalysts is extended to hyperpolarize α-ketoisocaproate and α-ketoisocaproate-1-[13C]. This is achieved by forming [Ir(H)2(κ2-ketoisocaproate)(N-heterocyclic carbene)(sulfoxide)] which transfers latent magnetism from p-H2 via the signal amplification by reversible exchange (SABRE) process. The effect of polarization transfer field on the formation of enhanced 13C magnetization is evaluated. Consequently, performing SABRE in a 0.5 µT field enabled most efficient magnetisation transfer. 13C NMR signals for α-ketoisocaproate-1-[13C] in methanol-d4 are up to 985-fold more intense than their traditional Boltzmann derived signal intensity (0.8% 13C polarisation). Single crystal X-ray diffraction reveals the formation of the novel catalyst decomposition products [Ir(µ-H)(H)2(IMes)(SO(Ph)(Me)2)]2 and [(Ir(H)2(IMes)(SO(Me)2))2(µ-S)] when the sulfoxides methylphenylsulfoxide and dimethylsulfoxide are used respectively.

U2 - 10.1002/cphc.202000825

DO - 10.1002/cphc.202000825

M3 - Article

SN - 1439-4235

JO - ChemPhysChem

JF - ChemPhysChem

M1 - 202000825R1

ER -