On‐Surface Self‐Assembly of a C₃‐Symmetric π‐Conjugated Molecule Family Studied by STM: Two‐Dimensional Nanoporous Frameworks

Abstract

The on-surface self-assembled behavior of four C -symmetric π-conjugated planar molecules (Tp, T12, T18, and Ex) has been investigated. These molecules are excellent building blocks for the construction of noncovalent organic frameworks in the bulk phase. Their hydrogen-bonded 2D on-surface self-assemblies are observed under STM at the solid/liquid interface; these structures are very different to those in the bulk crystal. Upon combining the results of STM measurements and DFT calculations, the formation mechanism of different assemblies is revealed; in particular, the critical role of hydrogen bonding in the assemblies. This research provides us with not only a deep insight into the self-assembled behavior of these novel functional molecules, but also a convenient approach toward the construction of 2D multiporous networks.

The self-assembly and pyridine regulation of a hydrogen-bonded dimeric building block formed by a low-symmetric aromatic carboxylic acid

“…7–9 Especially, double hydrogen bonds (O–H⋯O) between aromatic carboxylic acid groups have been widely used in the construction of two-dimensional (2D) molecular networks at the liquid–solid interface. 10–15 For example, trimesic acid (TMA) is a typical building block with three symmetric distributed carboxylic acid groups which can form a varies of networks under different temperature and concentration conditions. 16–18 Other C 3 -symmetric tricarboxylic acid molecules with different aromatic rigid skeletons can also form typical hexagonal honey-comb porous networks, such as triphenylene-2,6,10-tricarboxylic acid (H 3 TTCA) and 1,3,5-tris(4-carboxyphenyl) benzene (BTB).…”

Hydrogen-bonded porous frameworks constructed by rigid π-conjugated molecules with carboxy groups

“…Firstly, four kinds of rigid and planar C 3 PIs with sides of two different lengths (Tp, T12, T18, and Ex) were designed, synthesized, and subjected to HOF construction [93]. Such C 3 PIs were expected to form a 2D H-HexNet with multi void spaces [94]. Moreover, the size and shape of the void can be varied by changing the side length of the C 3 PIs.…”

Halogen Bonds Fabricate 2D Molecular Self-Assembled Nanostructures by Scanning Tunneling Microscopy

“…Similar to 3D self-assembly processes, the molecular self-assembly process on surfaces can be controlled by balancing molecule-molecule and molecule-substrate interactions [46,47,[51][52][53]. The intermolecular non-covalent bond of XB with high directionality, moderate bond strength (5-30 kJ/mol), and its binding geometry has been used to fabricate 2D nanostructures [40,[54][55][56][57][58][59]. Because of the large size of the halogen atom and the existence of the σ-hole, XB is more sensitive to the steric hindrance and directionality than HB [4,60].…”