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Proton reduction by [CoII(BPyPy2COH)(OH2)2]2+ (BPyPy2COH = [2,2'-bipyridin]-6-yl-di[pyridin-2-yl]methanol) proceeds through two distinct, pH-dependent pathways involving proton-coupled electron transfer (PCET), reduction and protonation steps. In this account we give an overview of the key mechanistic aspects in aqueous solution from pH 3 to 10, based on electrochemical data, time-resolved spectroscopy and ab initio molecular dynamics simulations of the key catalytic intermediates. In the acidic pH branch, a PCET to give a CoIII hydride is followed by a reduction and a protonation step, to close the catalytic cycle. At elevated pH, a reduction to CoI is observed, followed by a PCET to a CoII hydride, and the catalytic cycle is closed by a slow protonation step. In our simulation, both CoI and CoII–H feature a strong interaction with the surrounding solvent via hydrogen bonding, which is expected to foster the following catalytic step.

Nanotechnology, in order to become ultimately efficient, requires achieving the construction of elemental structures at the atomistic precision. One way toward this goal is using templated surfaces as support for directed synthesis. The nanomesh, a single-atom thick layer of hexagonal boron nitride on Rh(111) [Corso et al., Science 2004, 303, 217], has appeared as one candidate that provides a periodically corrugated structure on the nanometre scale. We present density functional theory studies where we investigate various properties of the nanomesh, ranging from intrinsic defects to covalent functionalisation with hydroxyl radicals. Further we study selective dehalogenation of an organic molecule (I6-CHP) on the nanomesh. This molecule adsorbs at particular sites of the template and has been activated for C–C coupling in recent experiments via dissociation of its halogen ligands. In all cases we find explicit templating effects, either in full agreement with experimental studies or predicting novel phenomena. The studies are evidence for the predictive power of modern electronic structure simulations and the insight that can be gained when used together with experiments on complex chemical structures.

The calculation of the electronic structure of large systems by methods based on density functional theory has recently gained a central role in molecular simulations. However, the extensive study of quantities like excited states and related properties is still out of reach due to high computational costs. We present a new implementation of a hybrid method, the Gaussian and Augmented-Plane-Wave (GAPW) method, where the electronic density is partitioned in hard and soft contributions. The former are local terms naturally expanded in a Gaussian basis, whereas the soft contributions are expanded in plane-waves by using a low energy cutoff, without loss in accuracy, even for all-electron calculations. For the calculation of excitation energies a recently developed, time-dependent density functional response theory (TD-DFRT) technique is joined with the GAPW procedure. We demonstrate the accuracy of the method by comparison with standard quantum chemistry calculations for a set of small molecules. To highlight the performance and efficiency of GAPW we show calculations on systems with several thousands of basis functions.