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Iridium α ‐Carboxyimine Complexes Hyperpolarized with para ‐Hydrogen Exist in Nuclear Singlet States before Conversion into Iridium Carbonates
Author(s) -
Tickner Ben. J.,
Iali Wissam,
Roy Soumya S.,
Whitwood Adrian C.,
Duckett Simon B.
Publication year - 2019
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201800829
Subject(s) - chemistry , iridium , imine , singlet state , hydride , photochemistry , amine gas treating , imes , medicinal chemistry , hydrogen , carbene , organic chemistry , catalysis , physics , nuclear physics , excited state
The formation and hyperpolarization of an [Ir(H) 2 (amine)(IMes)(η 2 ‐imine)]Cl complex that can be created in a hyperpolarized nuclear singlet state is reported. These complexes are formed when an equilibrium mixture of pyruvate, amine (benzylamine or phenylethylamine), and the corresponding imine condensation product, react with preformed [Ir(H) 2 (amine) 3 (IMes)]Cl. These iridium α‐carboxyimine complexes exist as two regioisomers differentiated by the position of amine. When examined with para ‐hydrogen the hydride resonances of the isomer with amine trans to hydride become strongly hyperpolarized. The initial hydride singlet states readily transfer to the corresponding 13 C 2 state in the labelled imine and exhibit magnetic state lifetimes of up to 11 seconds. Their 13 C signals have been detected with up to 420 fold signal gains at 9.4 T. On a longer timescale, and in the absence of H 2 , further reaction leads to the formation of neutral carbonate containing [Ir(amine)(η 2 ‐CO 3 )(IMes)(η 2 ‐imine)]. Complexes are characterized by, IR, MS, NMR and X‐ray diffraction.