Thermodynamics of an Electrocyclic Ring-Closure Reaction on Au(111)

Abstract

We have computationally studied the effects of temperature on the reaction pathway of an electrocyclic ring-closure reaction on the Au(111) surface, particularly focusing on thermodynamic aspects of the reaction. The electrocyclic ring-closure is accompanied by a series of dehydrogenation steps, and while it is found that temperature, in terms of vibrational entropy and enthalpy, has a reducing effect on most energy barriers, it does not alter the qualitative appreciation of the reaction kinetics. However, it is found that the way the abstracted hydrogen atoms are treated is crucial for the thermodynamics of the reaction. The overall reaction is highly endothermic, but becomes thermodynamically favorable due to the entropy gain of the hydrogen byproducts, which desorb associatively from the surface as H 2 . The study provides new outlooks for the theoretical treatment of reactions related to on-surface synthesis, anticipated to be instructive for future studies.

Topology Selectivity in On-Surface Dehydrogenative Coupling Reaction: Dendritic Structure versus Porous Graphene Nanoribbon

“…In the enthalpic path, the cleavages of C–H bonds of 5 and 6 are both endothermic reactions with corresponding energies of +0.58 eV and +1.23 eV, respectively. However, the free energy decrease from entropy increase was not considered in the calculations, which is ∼0.64 eV for each split-off hydrogen atom at the given condition, according to previous computational studies. − Therefore, the reaction forming molecule 5′ should be exergonic (∼−0.06 eV), while for molecule 6′ is endergonic (∼+0.59 eV). In the view of kinetics, the reaction barriers for the activations of the target C–H bond (a target C–H bond refers in particular to the ortho C–H bond of the radical site) in 5 (1.06 eV) is much lower than that of 6 (1.97 eV).…”

Controlling a Chemical Coupling Reaction on a Surface: Tools and Strategies for On-Surface Synthesis

“…Also, the importance of entropic effects is yet poorly studied and certainly underestimated. 433 Importantly, the time scale has not yet been explored, but some aspects of the dynamics of the reactions may in the future be accessible through appropriate experimental developments. 434 The expected application fields for on-surface synthesis are broad and numerous.…”

“…Despite various efforts to grow covalent patterns at the micrometer scale or more, the domain sizes are usually still limited to the range of a few tens of nanometers. Also, the importance of entropic effects is yet poorly studied and certainly underestimated . Importantly, the time scale has not yet been explored, but some aspects of the dynamics of the reactions may in the future be accessible through appropriate experimental developments …”

Supramolecular Modulation of Molecular Conformation of Metal Porphyrins toward Remarkably Enhanced Multipurpose Electrocatalysis and Ultrahigh‐Performance Zinc–Air Batteries

“…E ZPE is the zero-point energy that can be calculated using E ZPE = 1/2Σhv, in which v is the vibrational frequency of a normal mode and h is the Planck constant. S is the entropy that can be calculated as [46] S T k…”