Density Functional Theory Study of Reaction Equilibria in Signal Amplification by Reversible Exchange.

The front cover artwork is provided by the groups of Prof. Thomas Theis (North Carolina State University) Prof. Volker Blum (Duke University).

Density Functional Theory Study of Reaction Equilibria in Signal Amplification by Reversible Exchange.

An in-depth theoretical analysis of key chemical equilibria in Signal Amplification by Reversible Exchange (SABRE) is provided, employing density functional theory calculations to characterize the likely reaction network. For all reactions in the network, the potential energy surface is probed to identify minimum energy pathways. Energy barriers and transition states are calculated, and harmonic transition state theory is applied to calculate exchange rates that approximate experimental values.

Rational ligand choice extends the SABRE substrate scope.

Here we report on chelating ligands for Signal Amplification By Reversible Exchange (SABRE) catalysts that permit hyperpolarisation on otherwise sterically hindered substrates. We demonstrate H enhancements of ∼100-fold over 8.5 T thermal for 2-substituted pyridines, and smaller, yet significant enhancements for provitamin B and caffeine.

Cation influence on exciton localization in homologue scheelites.

Homologue scheelite crystals CaWO4, SrWO4, and BaWO4 possess similar crystal and electronic structure, but their luminescence exhibits drastically different thermal stabilities. By measuring the temperature dependence of the decay time of the intrinsic luminescence and fitting it to a three level model, we have qualitatively shown the effective exciton radius to increase in the order CaWO4 → SrWO4 → BaWO4, which explains the differences in the thermal stability. The origin of the variation in the exciton radii is suggested to be related to differences in the excited state dynamics in these crystals.

G0W0 band structure of CdWO4.

The full quasiparticle band structure of CdWO4 is calculated within the single-shot GW (G0W0) approximation using maximally localized Wannier functions, which allows one to assess the validity of the commonly used scissor operator. Calculations are performed using the Godby-Needs plasmon pole model and the accurate contour deformation technique. It is shown that while the two methods yield identical band gap energies, the low-lying states are given inaccurately by the plasmon pole model.