Energy Barrier: Focus on the Essential: Extracting the Decisive Energy Barrier of a Complex Process (Adv. Mater. Interfaces 20/2019)

Increasing the Templating Effect on a Bulk Insulator Surface: From a Kinetically Trapped to a Thermodynamically More Stable Structure

Molecular self-assembly, governed by the subtle balance between intermolecular and molecule- surface interactions, is generally associated with the thermodynamic ground state, while the competition between kinetics and thermodynamics during its formation is often neglected. Here, we present a simple model system of a benzoic acid derivative on a bulk insulator surface. Combining high-resolution non-contact atomic force microscopy experiments and density functional theory, we characterize the structure and the thermodynamic stability of a set of temperature-dependent molecular phases formed by 2,5-dihydroxybenzoic acid molecules, self- assembled on the insulating calcite (10.4) surface. We d…

On-surface synthesis on a bulk insulator surface

On-surface synthesis has rapidly emerged as a most promising approach to prepare functional molecular structures directly on a support surface. Compared to solution synthesis, performing chemical reactions on a surface offers several exciting new options: due to the absence of a solvent, reactions can be envisioned that are otherwise not feasible due to the insolubility of the reaction product. Perhaps even more important, the confinement to a two-dimensional surface might enable reaction pathways that are not accessible otherwise. Consequently, on-surface synthesis has attracted great attention in the last decade, with an impressive number of classical reactions transferred to a surface as…

Focus on the Essential: Extracting the Decisive Energy Barrier of a Complex Process

Molecular processes at surfaces can be composed of a rather complex sequence of steps. The kinetics of even seemingly simple steps are demonstrated to depend on a multitude of factors, which prohibits applying a simple Arrhenius law. This complexity can make it challenging to experimentally determine the kinetic parameters of a single step. However, a molecular-level understanding of molecular processes such as structural transitions requires elucidating the atomistic details of the individual steps. Here, a strategy is presented to extract the energy barrier of a decisive step in a very complex structural transition by systematically addressing all factors that impact the transition kineti…

Mechanisms of covalent dimerization on a bulk insulating surface

Combining density functional theory and high resolution NC-AFM experiments, we have studied the on surface reaction mechanisms' responsible for the covalent dimerization of 4-iodobenzoic acid (IBA) organic molecules on the calcite (10.4), insulating surface. When annealed at 580 K, the Molecules assemble in one-dimensional chains of covalently bound dimers: The chains have a unique orientation and result from a complex set of processes, including a nominally rather. costly double dehalogenation reaction followed by dimerization. First, focusing on the latter two processes and using the nudged elastic band method, we analyze a number of possible mechanisms involving one and two molecules, an…