Michael Garvey

Enhanced hydrogenation activity and diastereomeric interactions of methyl pyruvate co-adsorbed with R -1-(1-naphthyl)ethylamine on Pd(111)

Unmodified racemic sites on heterogeneous chiral catalysts reduce their overall enantioselectivity, but this effect is mitigated in the Orito reaction (methyl pyruvate (MP) hydrogenation to methyl lactate) by an increased hydrogenation reactivity. Here, this effect is explored on a R-1-(1-naphthyl)ethylamine (NEA)-modified Pd(111) model catalyst where temperature-programmed desorption experiments reveal that NEA accelerates the rates of both MP hydrogenation and H/D exchange. NEA+MP docking complexes are imaged using scanning tunnelling microscopy supplemented by density functional theory calculations to allow the most stable docking complexes to be identified. The results show that diastereomeric interactions between NEA and MP occur predominantly by binding of the C=C of the enol tautomer of MP to the surface, while simultaneously optimizing C=O····H2N hydrogen-bonding interactions. The combination of chiral-NEA driven diastereomeric docking with a tautomeric preference enhances the hydrogenation activity since C=C bonds hydrogenate more easily than C=O bonds thus providing a rationale for the catalytic observations.

Shear properties of potassium chloride films on iron obtained using density functional theory

Density functional theory is used to calculate the shear strength of a thin KCl film grown epitaxially on an Fe(100) substrate. It is first demonstrated that the calculations accurately reproduce the experimental values of the shear moduli of bulk KCl. The method is then extended to calculating the shear properties of a three-layer slab of KCl on an Fe(100) substrate, where shear is found to take place at the KCl-Fe(100) interface and the KCl essentially moves as a rigid body. The resulting calculated values of the shear strength at zero pressure along the [linear span]10[linear span] (79.8 MPa) and [linear span]11[linear span] (70.3 MPa) directions are in excellent agreement with the experimentally measured value of 65 ± 5 MPa.