Hyperpolarizing DNA Nucleobases via NMR Signal Amplification by Reversible Exchange.

The present work investigates the potential for enhancing the NMR signals of DNA nucleobases by parahydrogen-based hyperpolarization. Signal amplification by reversible exchange (SABRE) and SABRE in Shield Enables Alignment Transfer to Heteronuclei (SABRE-SHEATH) of selected DNA nucleobases is demonstrated with the enhancement () of H, N, and/or C spins in 3-methyladenine, cytosine, and 6-O-guanine. Solutions of the standard SABRE homogenous catalyst Ir(1,5-cyclooctadeine)(1,3-bis(2,4,6-trimethylphenyl)imidazolium)Cl ("IrIMes") and a given nucleobase in deuterated ethanol/water solutions yielded low H values (≤10), likely reflecting weak catalyst binding.

Biomimetic Metal-Free Hydride Donor Catalysts for CO Reduction.

The catalytic reduction of carbon dioxide to fuels and value-added chemicals is of significance for the development of carbon recycling technologies. One of the main challenges associated with catalytic CO reduction is product selectivity: the formation of carbon monoxide, molecular hydrogen, formate, methanol, and other products occurs with similar thermodynamic driving forces, making it difficult to selectively reduce CO to the target product. Significant scientific effort has been aimed at the development of catalysts that can suppress the undesired hydrogen evolution reaction and direct the reaction toward the selective formation of the desired products, which are easy to handle and store.

Photophysics of nanographenes: from polycyclic aromatic hydrocarbons to graphene nanoribbons.

Graphene quantum dots (GQDs) and nanoribbons (GNRs) are classes of nanographene molecules that exhibit highly tunable photophysical properties. There have been great strides in recent years to advance our understanding of nanographene photophysics and develop their use in light-harvesting systems, such as artificial photosynthesis. Here, we review the latest studies of GQDs and GNRs which have shed new light onto their photophysical underpinnings through computational and advanced spectroscopic techniques.

Kinetics of Hydride Transfer from Catalytic Metal-Free Hydride Donors to CO.

Selective reduction of CO to formate represents an ongoing challenge in photoelectrocatalysis. To provide mechanistic insights, we investigate the kinetics of hydride transfer (HT) from a series of metal-free hydride donors to CO. The observed dependence of experimental and calculated HT barriers on the thermodynamic driving force was modeled by using the Marcus hydride transfer formalism to obtain the insights into the effect of reorganization energies on the reaction kinetics.

Facile Removal of Homogeneous SABRE Catalysts for Purifying Hyperpolarized Metronidazole, a Potential Hypoxia Sensor.

We report a simple and effective method to remove IrIMes homogeneous polarization transfer catalysts from solutions where NMR Signal Amplification By Reversible Exchange (SABRE) has been performed, while leaving intact the substrate's hyperpolarized state. Following microTesla SABRE hyperpolarization of N spins in metronidazole, addition of SiO microparticles functionalized with 3-mercaptopropyl or 2-mercaptoethyl ethyl sulfide moieties provides removal of the catalyst from solution well within the hyperpolarization decay time at 0.3 T ( >3 mins)-and enabling transfer to 9.

Imaging of Biomolecular NMR Signals Amplified by Reversible Exchange with Parahydrogen Inside an MRI Scanner.

The Signal Amplification by Reversible Exchange (SABRE) technique employs exchange with singlet-state parahydrogen to efficiently generate high levels of nuclear spin polarization. Spontaneous SABRE has been shown previously to be efficient in the milli-Tesla and micro-Tesla regimes. We have recently demonstrated that high-field SABRE is also possible, where proton sites of molecules that are able to reversibly coordinate to a metal center can be hyperpolarized directly within high-field magnets, potentially offering the convenience of hyperpolarization-based spectroscopy and imaging without sample shuttling.

Heterogeneous Microtesla SABRE Enhancement of N NMR Signals.

The hyperpolarization of heteronuclei via signal amplification by reversible exchange (SABRE) was investigated under conditions of heterogeneous catalysis and microtesla magnetic fields. Immobilization of [IrCl(COD)(IMes)], [IMes=1,3-bis(2,4,6-trimethylphenyl), imidazole-2-ylidene; COD=cyclooctadiene] catalyst onto silica particles modified with amine linkers engenders an effective heterogeneous SABRE (HET-SABRE) catalyst that was used to demonstrate a circa 100-fold enhancement of N NMR signals in N-pyridine at 9.4 T following parahydrogen bubbling within a magnetic shield.