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

Björk, Jonas

doi:10.1021/acs.jpcc.6b08755

Cited by 21 publications

(24 citation statements)

References 33 publications

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“…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).…”

Section: Resultsmentioning

confidence: 99%

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

et al. 2021

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Selective control on the topology of low-dimensional covalent organic nanostructures in on-surface synthesis has been challenging. Herein, with combined scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS), we report a successful topology-selective coupling reaction on the Cu(111) surface by tuning the thermal annealing procedure. The precursor employed is 1,3,5-tris(2-bromophenyl)benzene (TBPB), for which Ullmann coupling is impeded due to the intermolecular steric hindrance. Instead, its chemisorption on the Cu(111) substrate has triggered the ortho C–H bond activation and the following dehydrogenative coupling at room temperature (RT). In the slow annealing experimental procedure, the monomers have been preorganized by their self-assembly at RT, which enhances the formation of dendritic structures upon further annealing. However, the chaotic chirality of dimeric products (obtained at RT) and hindrance from dense molecular island make the fabrication of high-quality porous two-dimensional nanostructures difficult. In sharp contrast, direct deposition of TBPB molecules on a hot surface led to the formation of ordered porous graphene nanoribbons and nanoflakes, which is confirmed to be the energetically favorable reaction pathway through density functional theory-based thermodynamic calculations and control experiments. This work demonstrates that different thermal treatments could have a significant influence on the topology of covalent products in on-surface synthesis and presents an example of the negative effect of molecular self-assembly to the ordered covalent nanostructures.

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Section: Resultsmentioning

confidence: 99%

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

et al. 2021

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“…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.…”

Section: Discussionmentioning

confidence: 99%

“…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 …”

Section: Discussionmentioning

confidence: 99%

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

2019

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On-surface synthesis is appearing as an extremely promising research field aimed at creating new organic materials. A large number of chemical reactions have been successfully demonstrated to take place directly on surfaces through unusual reaction mechanisms. In some cases the reaction conditions can be properly tuned to steer the formation of the reaction products. It is thus possible to control the initiation step of the reaction and its degree of advancement (the kinetics, the reaction yield); the nature of the reaction products (selectivity control, particularly in the case of competing processes); as well as the structure, position, and orientation of the covalent compounds, or the quality of the as-formed networks in terms of order and extension. The aim of our review is thus to provide an extensive description of all tools and strategies reported to date and to put them into perspective. We specifically define the different approaches available and group them into a few general categories. In the last part, we demonstrate the effective maturation of the on-surface synthesis field by reporting systems that are getting closer to application-relevant levels thanks to the use of advanced control strategies.

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“…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…”

Section: Discussionmentioning

confidence: 99%

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

Cui

Wang

Bian

et al. 2021

Advanced Energy Materials

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Modulating the intrinsic catalytic activity of molecular catalysts to improve electrocatalytic performance is significant but challenging. Herein, a simple yet effective strategy to induce molecular flattening of Co (III) meso‐tetra (N‐methyl‐4‐pyridyl) porphyrine (Co‐TMPyP) by supramolecular assembly with chemically converted graphene (CCG) via synergistic electrostatic and π–π interactions is reported. This unique variation in molecular conformation leads to a shortened CoN coordination bond and enhanced electron transfer from the porphyrin macrocycle to the metal ion, thereby optimizing the electronic structure of the catalytic active center in Co‐TMPyP molecule. Thus, the flattened Co‐TMPyP on CCG (Co‐TMPyP/CCG) demonstrates remarkable electrocatalytic performance for the oxygen reduction reaction (ORR), hydrogen evolution reaction (HER), and oxygen evolution reaction (OER) simultaneously as a tri‐functional molecular catalyst for the first time with a high half‐wave potential of 0.824 V for ORR and a low overpotential for HER (320 mV) and OER (379 mV) at 10 mA cm–2, respectively, not only much better than the pristine Co‐TMPyP but also among the best results of molecular catalysts in each aspect of ORR, OER, and HER achieved thus far. As a practical demonstration, the Co‐TMPyP/CCG catalyst is used to assemble a rechargeable Zn–air battery, which shows the highest specific capacity (793 mAh g–1) and power density (225.4 mW cm–2) among all molecular catalyst‐based Zn–air batteries ever reported.

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

Cited by 21 publications

References 33 publications

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

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

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

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

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