Abstract:Many 2D covalent polymers synthesized as single layers on surfaces show inherent disorder, expressed for example in their ring-size distribution. Systems which are expected to form the thermodynamically favored hexagonal lattice usually deviate from crystallinity and include high numbers of pentagons, heptagons, and rings of other sizes. The amorphous structure of two different covalent polymers in real space using scanning tunneling microscopy is investigated. Molecular dynamics simulations are employed to ex… Show more
“…The formation of periodic porous metal− organic networks with topologies resembling those shown in Figures 9 and 11 has been demonstrated experimentally for molecules, such as dicarbonitrile linkers, 63 porphyrins, 64 1,3,5tris(4-bromophenyl)benzene 65 adsorbed on Ag(111), and for many other supramolecular systems on surfaces. 7 Aperiodic 2D multiporous networks have been, on the other hand, observed, for example, in the case of 1,3,5-tris-(4-bromophenyl)-benzene on Au(111) 66 and imine-based covalent organic frameworks. 67 The theoretical results presented in this work enabled us to formulate a few design principles, which relate to the internal structure of the anthracene building blocks.…”
Functionalized polycyclic aromatic hydrocarbons (PAHs) have been recently recognized as promising building blocks for surface-assisted polymerization reactions producing low-dimensional covalent structures with tailorable properties. In this work, we used the lattice Monte Carlo (MC) simulation method to predict the structure of the labile metal−(halogenated)anthracene connections preceding the formation of covalent polymers in the Ullmann-type coupling reaction occurring on catalytically active metallic surfaces. To that purpose, a coarse-grained model of mono-, di-, and trisubstituted anthracene monomers and two-coordinate metal atoms was proposed, in which these components were adsorbed on a triangular lattice. The formation of metal−organic nodes cementing the resulting superstructures was assumed to be dependent on the directionality of the short-range interactions assigned differently to PAH molecules. Our extensive MC simulations performed for the complete set of 50 positional isomers predicted various organometallic intermediates with morphologies ranging from cyclic oligomers, chains, ladders, ribbons to aperiodic networks and others. These results were compared with the analogous findings obtained for the smaller naphthalene unit. The outcome of the theoretical studies reported herein can be helpful in designing low-dimensional covalent polymers with tunable architecture and functions.
“…The formation of periodic porous metal− organic networks with topologies resembling those shown in Figures 9 and 11 has been demonstrated experimentally for molecules, such as dicarbonitrile linkers, 63 porphyrins, 64 1,3,5tris(4-bromophenyl)benzene 65 adsorbed on Ag(111), and for many other supramolecular systems on surfaces. 7 Aperiodic 2D multiporous networks have been, on the other hand, observed, for example, in the case of 1,3,5-tris-(4-bromophenyl)-benzene on Au(111) 66 and imine-based covalent organic frameworks. 67 The theoretical results presented in this work enabled us to formulate a few design principles, which relate to the internal structure of the anthracene building blocks.…”
Functionalized polycyclic aromatic hydrocarbons (PAHs) have been recently recognized as promising building blocks for surface-assisted polymerization reactions producing low-dimensional covalent structures with tailorable properties. In this work, we used the lattice Monte Carlo (MC) simulation method to predict the structure of the labile metal−(halogenated)anthracene connections preceding the formation of covalent polymers in the Ullmann-type coupling reaction occurring on catalytically active metallic surfaces. To that purpose, a coarse-grained model of mono-, di-, and trisubstituted anthracene monomers and two-coordinate metal atoms was proposed, in which these components were adsorbed on a triangular lattice. The formation of metal−organic nodes cementing the resulting superstructures was assumed to be dependent on the directionality of the short-range interactions assigned differently to PAH molecules. Our extensive MC simulations performed for the complete set of 50 positional isomers predicted various organometallic intermediates with morphologies ranging from cyclic oligomers, chains, ladders, ribbons to aperiodic networks and others. These results were compared with the analogous findings obtained for the smaller naphthalene unit. The outcome of the theoretical studies reported herein can be helpful in designing low-dimensional covalent polymers with tunable architecture and functions.
“…of the experimentally observed polymer networks were in satisfactory agreement with those of the simulated ones (c.f. figure 10) [106].…”
Section: (E) Composite Systemsmentioning
confidence: 99%
“…figure 10) [106]. Figure 9Small cut-out of the structure of a molecular dynamic simulation of approximately 5700 molecules of (1,3,5-tris-(4-bromophenyl)-benzene after approximately 240 ps [106]. The red spheres indicate the position of the central benzene ring, while the blue spheres correspond to the bromophenyl units.Figure 10Comparison of ring-size and αβγ cluster distributions for (1,3,5-tris-(4-bromophenyl)-benzene, from experiment, molecular dynamics (MD) simulations and expected from a mean-field model for size distributions Pfalse(α,β,γfalse)=Pα×Pβ×Pγ×ffalse(α,β,γfalse) (equation 1) [106].…”
Section: Examplesmentioning
confidence: 99%
“…Figure 9Small cut-out of the structure of a molecular dynamic simulation of approximately 5700 molecules of (1,3,5-tris-(4-bromophenyl)-benzene after approximately 240 ps [106]. The red spheres indicate the position of the central benzene ring, while the blue spheres correspond to the bromophenyl units.Figure 10Comparison of ring-size and αβγ cluster distributions for (1,3,5-tris-(4-bromophenyl)-benzene, from experiment, molecular dynamics (MD) simulations and expected from a mean-field model for size distributions Pfalse(α,β,γfalse)=Pα×Pβ×Pγ×ffalse(α,β,γfalse) (equation 1) [106]. An αβγ cluster corresponds to the three rings of sizes α, β and γ that intersect at a corner of the lattice, ffalse(α,β,γfalse) is the multiplicity (1, for ring index ααα; 3, for ring index ααβ, with α≠β; 6, for ring index αβγ, with α,β,γ all different), and Pα is the probability of an α-gon according to the observed ring-size histogram.…”
Structure prediction of stable and metastable polymorphs of chemical systems in low dimensions has become an important field, since materials that are patterned on the nano-scale are of increasing importance in modern technological applications. While many techniques for the prediction of crystalline structures in three dimensions or of small clusters of atoms have been developed over the past three decades, dealing with low-dimensional systems—ideal one-dimensional and two-dimensional systems, quasi-one-dimensional and quasi-two-dimensional systems, as well as low-dimensional composite systems—poses its own challenges that need to be addressed when developing a systematic methodology for the determination of low-dimensional polymorphs that are suitable for practical applications. Quite generally, the search algorithms that had been developed for three-dimensional systems need to be adjusted when being applied to low-dimensional systems with their own specific constraints; in particular, the embedding of the (quasi-)one-dimensional/two-dimensional system in three dimensions and the influence of stabilizing substrates need to be taken into account, both on a technical and a conceptual level.
This article is part of a discussion meeting issue ‘Supercomputing simulations of advanced materials’.
“…In recent years, vitreous 2D silica bilayer network [5,6], 2D germanium dioxide film [7][8][9], and monolayer amorphous carbon [10] have been prepared, and the structures are determined by atomic-resolution scanning tunneling microscopy (STM) or transmission electron microscopy (TEM) [11], which has a great significance to the fundamental understanding and material modification of amorphous solids in the future. Meanwhile, a series of 2D random molecular networks as glassy systems have also been obtained through non-covalent bonding [12][13][14][15][16][17] and non-reversible covalent bonding [18,19]. Various explanations have been proposed to explain the origin of the disordered appearance of molecular networks.…”
Unraveling the nature of complex condensed matter systems is of paramount importance in a variety of fields such as pharmacology and materials science. Here we report the synthesis, by the dynamic covalent chemistry (DCC), of a robust, continuous, and low-defect glassy covalent organic network (GCON). The direct imaging of the molecular structure clearly shows the amorphous nature of GCONs, which consists with the competing (nano) crystallite model, not Zachariasen continuous random networks (Z-CRN). Remarkably, the microscopic friction properties were measured on GCONs by atomic force microscopy (AFM), and the GCONs showed lower friction force in comparison with crystalline covalent organic frameworks (COFs).
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