Control of a two-dimensional molecular structure by cooperative halogen and hydrogen bonds

Abstract

The cooperative effect of hydrogen and halogen bonds on the two-dimensional (2D) molecular arrangement on highly oriented pyrolytic graphite (HOPG) was studied by scanning tunneling microscopy. The terephthalic acid (TPA) molecule, which has two carboxyl g roups attached at the para positions of a benzene ring, formed a one-dimensional (1D) linear non-covalent network structure on HOPG by hydrogen bonds between the carboxyl groups of neighboring molecules. However, unlike the TPA molecule, Br substituted TPA molecules were found to form different non-covalent network structures. Owing to Br … O halogen and hydrogen bonds, bromo-substituted TPA (2-bromoterephthalic acid) formed a 1D ladder-like non-covalent network structure, whereas dibromo-substituted TPA (2,5-dibromoterephthalic acid) formed a 2D non-covalent lattice network on HOPG. These results strongly indicate that Br … O halogen significantly contribute to determine the molecular assembly as well as hydrogen bonds for molecules containing bromine groups and hydrogen bonding groups. These results provided deep fundamental insight into the cooperative effect of halogen and hydrogen bonds in 2D molecular assembly. In addition, we have demonstrated that these interactive bonds are promising for the precise design of 2D molecular architectures.

Combining high-resolution scanning tunnelling microscopy and first-principles simulations to identify halogen bonding

“…Halogen bonds can also involve halogen atoms acting simultaneously as both donor and acceptor 11,16,17,23,24 , with the positive electrostatic potential of the sigma hole oriented towards the central 'belt' of negative electrostatic potential found on an adjacent halogen atom. Alternatively, nitrogen 10,12,13,19 and oxygen 17,[25][26][27] atoms act as acceptor sites in heteromolecular assemblies.…”

Fluorinated carboxylic acids as powerful building blocks for the formation of bimolecular monolayers

“…TPA is a prototypical molecule used to study hydrogen-bond-controlled self-assembly, and its ability to form ordered homomolecular monolayers is well known. [22][23][24][25][26][27][28][29][30][31][32][33] As the homomolecular self-assembly of TPA (Fig. S1 and Fig.…”

“…S1 and Fig. S2) has been extensively studied at the heptanoic acid/highly oriented pyrolytic graphite (HOPG) interface, [22][23][24][25] we decided to investigate the assembly of F4TPA at the same interface. However, despite multiple attempts performed with a range of different solution concentrations, we never observed any evidence for the homomolecular self-assembly of F4TPA (see ESI †).…”

One “Click” access to self-complementary molecular modules for halogen bonding

“…[1][2][3] First recognized as an effective tool in crystal engineering, 4,5 the application of XB is nowadays moving towards a wide range of elds encompassing organocatalysis, 6 biology and drug design, [7][8][9][10] anion transport and recognition, [11][12][13][14][15] and materials science. [16][17][18][19][20][21][22][23] According to the IUPAC denition, 24 XB is an attractive non-covalent interaction occurring between an electrophilic halogen atom in a molecule and a nucleophile. The ability of halogen atoms to act as electrophiles relies on the anisotropic distribution of the electron density around halogen atoms involved in covalent bonds with one or more atoms: 25 a cap of positive electrostatic potential (the so-called s-hole 26 ) is generated on the elongation of each covalent bond, and is responsible for the interaction with nucleophiles.…”