Model for self-assembly of Br–H and Br–Br bonded Br₄Py molecules

Abstract

A model, based on the pairwise intermolecular halogen–hydrogen (Br–H) and halogen–halogen (Br–Br) bonding, is proposed to describe the self-assembly of Br4Py molecules into two different planar structures (Phase I and Phase II). The pair bonding interactions are calculated by the density functional theory for the two-molecule and four-molecule clusters. It is shown that about 60% of bonding strength is due to the electrostatic Br(top)–Br(belt) interactions, while the remaining originates from Br–H interactions. The obtained values of pair interactions are further used for Monte Carlo calculations. The model for these calculations is proposed on a square lattice. The two main pair interactions are needed for the emergence of the Phase I ordering, while the Phase II ordering is obtained using a single interaction. The obtained results explain the emergence of both phases.

On-Surface Synthesis of Graphene Nanoribbons: Photoelectron Spectroscopy Reveals Impact of Substrate Reactivity

“…Considering the molecular growth structures, , DBBA with a nominal thickness of 8 Å was deposited on the cooled substrates in order to obtain the on-surface structures. Despite the effect of the coverage on the self-assembled molecules, , with the chosen thickness (8 Å), our spectra match well with the published XPS results. , On Au(111) (Figure b, additional data in Figure S5a), with the temperature increasing from 200 to 420 K, the intensity of the C 1s peak decreases, while the peak position remains at the same BE; such a behavior suggests that desorption, but no chemical reactions, takes place. By increasing the temperature to ∼540 K, bromine atoms are detached from DBBA (Figure S5a), and the intensity of C 1s signal weakens, representing the occurrence of debromination reaction .…”

Theoretical insights into the interplay between metal–organic and covalent bonding in single-layer molecular networks formed by halogen dissociation

“…The latter species, usually a negligible number at higher temperatures, were omitted from the actual simulations, as their characteristic interactions are relatively weak. [33][34][35] Therefore, the simulated ensemble consisted only of debrominated species, which were initially randomly dispersed on the lattice. Their populations p 0 , p 1 , p 2 and p 3 (as normalized to N M ) were specifically chosen for each real temperature and used substrate.…”

“…30 The assemblies of symmetric tetratopic molecular building blocks were also extensively explored in the MC studies. [31][32][33][34] In the current work, we present a rather simple model for the assembly of both metal-organic and covalent single-layer molecular networks, taking Br 4 Py as the prototypical halogenated polyarene. The model is partially based on our previous works which have addressed molecular ensembles of intact 33 and dehalogenated 34 pyrene derivatives.…”

“…[31][32][33][34] In the current work, we present a rather simple model for the assembly of both metal-organic and covalent single-layer molecular networks, taking Br 4 Py as the prototypical halogenated polyarene. The model is partially based on our previous works which have addressed molecular ensembles of intact 33 and dehalogenated 34 pyrene derivatives. The growth of molecular networks is studied by performing the MC simulations.…”

“…30 The assemblies of symmetric tetratopic molecular building blocks were also extensively explored in the MC studies. 31–34…”