Stereochemistry of 2D Molecular Crystallization

Ernst, Karl‐Heinz

doi:10.2533/chimia.2014.49

Cited by 4 publications

(3 citation statements)

References 28 publications

(31 reference statements)

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“…Alternatively, adsorbed chiral molecules may bestow chirality on metal surfaces. With relatively inert metals such as copper, it has been shown that the adsorption of chiral molecules can lead to the formation of many ordered homochiral structures. − Perhaps more interestingly, on the surface of more active metals such as Pt or Pd, chiral sites can be generated via the adsorption of submonolayer coverages of “templating” chiral molecules. − In that case, it is presumed that the adsorbates form supramolecular structures on the surface containing chiral pockets that can act as enantioselective adsorption sites for other adsorbates. Unfortunately, as mentioned before, these ideas generated from experiments using model systems are yet to translate into the design of realistic enantioselective catalysts.…”

Section: Selectivitymentioning

confidence: 99%

The Surface Chemistry of Metal-Based Hydrogenation Catalysis

2017

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The promotion of hydrogenation reactions by transitionmetal-based heterogeneous catalysts was established many decades ago but is still quite common in the chemical industry. Because of their importance, these processes have been studied in great detail from both fundamental and practical points of view, and much has been learned about them. However, some key questions remain unanswered, and solutions to specific industrial needs are still pending. In this Perspective, we discuss the state-of-the-art of our understanding of some of the fundamental issues associated with hydrogenation catalysis. From the mechanistic point of view, we use the example of olefin hydrogenation to assess the status of our knowledge on the adsorption of the organic reactants, the role that the strongly adsorbed carbonaceous deposits that form during reaction play in defining the catalytic kinetics, the mechanistic details of the hydrogen dissociative uptake and surface mobility during reaction, and the dynamic changes of the structure of the surface induced by the catalytic conditions. We then introduce the issue of selectivity in connection with the hydrogenation of alkynes, dienes, trienes, and aromatics; unsaturated aldehydes and imines; and cases where hydrogenation competes with other types of reactions such as dehydrogenations, skeletal rearrangements, cyclizations, and hydrogenolysis. Two general approaches to the control of selectivity are discussed: via the tuning of the structure of the catalytic surface, which can now be addressed by using nanoparticles with specific sizes and shapes, and by modifying the electronic properties of the metal, via the addition of a second element. Finally, we make reference to the interest in designing enantioselective hydrogenation processes using heterogeneous metal catalysts, and we briefly summarize the ideas that have developed from surface-science studies toward this goal and the advances made in understanding the most promising approach to date, which involves the addition of molecular chiral modifiers to the reaction mixtures.

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Section: Selectivitymentioning

confidence: 99%

The Surface Chemistry of Metal-Based Hydrogenation Catalysis

2017

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“…Recently, chiral recognition in the two dimensional (2D) self-assembly of helicenes on metal surfaces has attracted a great deal of interest. It is also a modern approach for understanding the fundamental steps in the crystallization of racemates [2,6,11,12,13]. For instance, the self-assembly of [7]H and its derivatives have been studied systematically on various metal surfaces, in both enantiopure and racemic forms ( rac ), revealing that a homochiral trimer or tetramer with three- or four-fold symmetry [14,15,16], and heterochiral dimers constituted the building blocks of the corresponding assemblies [15,17,18].…”

Section: Introductionmentioning

confidence: 99%

Chiral Recognition of Hexahelicene on a Surface via the Forming of Asymmetric Heterochiral Trimers

Zhang

Liu

Shen

et al. 2019

IJMS

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Chiral recognition among helical molecules is of essential importance in many chemical and biochemical processes. The complexity necessitates investigating manageable model systems for unveiling the fundamental principles of chiral recognition at the molecular level. Here, we reported chiral recognition in the self-assembly of enantiopure and racemic hexahelicene on a Au(111) surface. Combing scanning tunneling microscopy (STM) and atomic force microscopy (AFM) measurements, the asymmetric heterochiral trimers were observed as a new type of building block in racemic helicene self-assembly on Au(111). The intermolecular recognition of the heterochiral trimer was investigated upon manual separation so that the absolute configuration of each helicene molecule was unambiguously determined one by one, thus confirming that the trimer was “2+1” in handedness. These heterochiral trimers showed strong stability upon different coverages, which was also supported by theoretical calculations. Our results provide valuable insights for understanding the intermolecular recognition of helical molecules.

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“…The recent progress in the experimental realization of complex surface tessellations on an atomic and molecular level [7][8][9][10][11][12][13][14] is driven by the intriguing physical [15][16][17][18][19][20][21][22] and chemical 23 properties of these systems. In this respect, the supramolecular chemistry offers tools for engineering of distinct self-assembled surface geometries that present an expression of semiregular [24][25][26][27][28][29][30] , fractal [31][32][33][34][35] , quasicrystalline [36][37][38][39] , and random [3][4][5][6] tilings.…”

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confidence: 99%

Complex k-uniform tilings by a simple bitopic precursor self-assembled on Ag(001) surface

et al. 2020

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The realization of complex long-range ordered structures in a Euclidean plane presents a significant challenge en route to the utilization of their unique physical and chemical properties. Recent progress in on-surface supramolecular chemistry has enabled the engineering of regular and semi-regular tilings, expressing translation symmetric, quasicrystalline, and fractal geometries. However, the k-uniform tilings possessing several distinct vertices remain largely unexplored. Here, we show that these complex geometries can be prepared from a simple bitopic molecular precursor-4,4'-biphenyl dicarboxylic acid (BDA)by its controlled chemical transformation on the Ag(001) surface. The realization of 2-and 3-uniform tilings is enabled by partially carboxylated BDA mediating the seamless connection of two distinct binding motifs in a single long-range ordered molecular phase. These results define the basic self-assembly criteria, opening way to the utilization of complex supramolecular tilings.

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Stereochemistry of 2D Molecular Crystallization

Cited by 4 publications

References 28 publications

The Surface Chemistry of Metal-Based Hydrogenation Catalysis

The Surface Chemistry of Metal-Based Hydrogenation Catalysis

Chiral Recognition of Hexahelicene on a Surface via the Forming of Asymmetric Heterochiral Trimers

Complex k-uniform tilings by a simple bitopic precursor self-assembled on Ag(001) surface

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