Iridium Cyclooctene Complex Forms a Hyperpolarization Transfer Catalyst Before Converting to a Binuclear C-H Bond Activation Product Responsible for Hydrogen Isotope Exchange

[IrCl(COE)2]2 ( 1 ) reacts with pyridine and H2 to form crystallo-graphically characterized IrCl(H)2(COE)(py)2 ( 2 ). 2 undergoes pyridine loss to form 16-electron IrCl(H)2(COE)(py) (3) with equivalent hydride ligands. When this reaction is studied with parahydrogen, 1 efficiently achieves the hyperpolarization of free pyridine (and nicotinamide, nicotine, 5-aminopyrimidine and 3,5-lutudine) via signal amplification by reversible exchange (SABRE) and hence reflects a simple and readily available precatayst for this process. 2 reacts further over 48 hrs at 298 K to form crystallographically characterized (Cl)(H)(py)(μ-Cl)(μ-H)(κ-μ-NC5H4)Ir(H)(py)2 (4). This dimer is shown to be active in the hydrogen isotope exchange process that is used in radiophar-maceutical preparations. Furthermore, while [Ir(H)2(COE)(py)3]PF6 ( 6 ) forms on addition of AgPF6 to 2 , its stability precludes its efficient involvement in SABRE

Cardiac MRI to Investigate Myocardial Scar and Coronary Venous Anatomy Using a Slow Infusion of Dimeglumine Gadobenate in Patients Undergoing Assessment for Cardiac Resynchronization Therapy

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η2-Alkene complexes of [Rh(PONOP-iPr)(L)]+ cations (L = COD, NBD, Ethene). Intramolecular alkene-assisted hydrogenation and dihydrogen complex [Rh(PONOP-iPr)(η-H2)].

Rhodium-alkene complexes of the pincer ligand κ3-C5H3N-2,6-(OPiPr2)2 (PONOP-iPr) have been prepared and structurally characterized: [Rh(PONOP-iPr)(η2-alkene)][BArF4] [alkene = cyclooctadiene (COD), norbornadiene (NBD), ethene; ArF = 3,5-(CF3)2C6H3]. Only one of these, alkene = COD, undergoes a reaction with H2 (1 bar), to form [Rh(PONOP-iPr)(η2-COE)][BArF4] (COE = cyclooctene), while the others show no significant reactivity. This COE complex does not undergo further hydrogenation. This difference in reactivity between COD and the other alkenes is proposed to be due to intramolecular alkene-assisted reductive elimination in the COD complex, in which the η2-bound diene can engage in bonding with its additional alkene unit. H/D exchange experiments on the ethene complex show that reductive elimination from a reversibly formed alkyl hydride intermediate is likely rate-limiting and with a high barrier. The proposed final product of alkene hydrogenation would be the dihydrogen complex [Rh(PONOP-iPr)(η2-H2)][BArF4], which has been independently synthesized and undergoes exchange with free H2 on the NMR time scale, as well as with D2 to form free HD. When the H2 addition to [Rh(PONOP-iPr)(η2-ethene)][BArF4] is interrogated using pH2 at higher pressure (3 bar), this produces the dihydrogen complex as a transient product, for which enhancements in the 1H NMR signal for the bound H2 ligand, as well as that for free H2, are observed. This is a unique example of the partially negative line-shape effect, with the enhanced signals that are observed for the dihydrogen complex being explained by the exchange processes already noted

Molecular MRI in the Earth's Magnetic Field Using Continuous Hyperpolarization of a Biomolecule in Water

In this work, we illustrate a method to continuously hyperpolarize a biomolecule, nicotinamide, in water using parahydrogen and signal amplification by reversible exchange (SABRE). Building on the preparation procedure described recently by Truong et al. [ J. Phys. Chem. B, 2014, 118, 13882-13889 ], aqueous solutions of nicotinamide and an Ir-IMes catalyst were prepared for low-field NMR and MRI. The 1H-polarization was continuously renewed and monitored by NMR experiments at 5.9 mT for more than 1000 s. The polarization achieved corresponds to that induced by a 46 T magnet (P = 1.6 × 10-4) or an enhancement of 104. The polarization persisted, although reduced, if cell culture medium (DPBS with Ca2+ and Mg2+) or human cells (HL-60) were added, but was no longer observable after the addition of human blood. Using a portable MRI unit, fast 1H-MRI was enabled by cycling the magnetic field between 5 mT and the Earth's field for hyperpolarization and imaging, respectively. A model describing the underlying spin physics was developed that revealed a polarization pattern depending on both contact time and magnetic field. Furthermore, the model predicts an opposite phase of the dihydrogen and substrate signal after one exchange, which is likely to result in the cancelation of some signal at low field

First evidence of mutualism between ancient plant lineages (Haplomitriopsida liverworts) and Mucoromycotina fungi and its response to simulated Palaeozoic changes in atmospheric CO2

© 2014 The Authors. New Phytologist © 2014 New Phytologist Trust. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. The attached file is the published version of the article

Long-lived States to Sustain SABRE Hyperpolarised Magnetisation

The applicability of the magnetic resonance (MR) technique in the liquid phase is limited by poor sensitivity and short nuclear spin coherence times which are insufficient for many potential applications. Here we illustrate how it is possible to address both of these issues simultaneously by harnessing long-lived hyperpolarised spin states that are formed by adapting the Signal Amplification by Reversible Exchange (SABRE) technique. We achieve more than 4 % net 1H-polarisation in a long-lived form that remains detectable for over ninety seconds by reference to proton pairs in the biologically important molecule nicotinamide and a pyrazine derivative whose in vivo imaging will offer a new route to probe disease in the futur