Self-Assembly and External Modulation of a Flexible Porphyrin Derivative on Highly Oriented Pyrolytic Graphite

Regulation of the Assembled Structure of a Flexible Porphyrin Derivative Containing Tetra Isophthalic Acids by Coronene or Different Pyridines

Based on previous research, a new coassembly formed by a porphyrin derivative (IPETPP), which contains a flexible substituent of m-phthalic acid, is observed with coronene (COR) molecules at a higher concentration. Besides, a fresh IPETPP self-assembly formed at a lower concentration and another new coassembly with COR molecules are obtained. Moreover, the addition of a series of bipyridines alters the diamond arrangement of IPETPP, which enhances the stability of the two-component structures. It is unprecedented that bipyridine derivatives break intermolecular hydrogen bonds containing m-phthalic acid substituents. All the coassemblies are investigated by scanning tunneling microscopy on a highly oriented pyrolytic graphite. Combined with density functional theory, the formation mechanism of the assembled structures is revealed. These results would contribute to understanding the interfacial crystal behaviors and probably provide an efficient pathway to regulate the binary structures.

Regulation of a Porphyrin Derivative Containing Two Symmetric Benzoic Acids by Different Pyridines

A porphyrin derivative called 5,15-di(4-carboxyphenyl)porphyrin (H₂DCPp) with carboxyl groups successfully self-assembled on a highly oriented pyrolytic graphite (HOPG) surface and its co-assembly structures with three kinds of pyridine molecules were investigated by scanning tunneling microscopy (STM) with atomic resolution. H₂DCPp arranged in a long-range ordered structure, and both 1,4-bis (pyridin-4-ylethynyl) benzene (BisPy), 4,4'-bipyridine (BP) and 1,3,5-tris(pyridin-4-ylethynyl) benzene (TPYB) molecules successfully regulated the host molecules as guest molecules. The well-organized model optimized by density functional theory (DFT) calculations reveals the detailed behavior of the assembly characteristics and regulation of porphyrin derivatives, which is helpful for the research and development of solar cells and nanodevices.

On-Surface Self-Assembled Structural Transformation Induced by Schiff Base Reaction and Hydrogen bonds

By utilizing scanning tunneling microscopy (STM), the self-assembled nanostructures of three characteristic aldehydes have been examined at the solution-solid interface. By introducing the active reactant 5-aminoisophthalic acid (5-AIPA), we succeeded in changing the self-assembled molecular structures through the condensation reaction and obtained the information on structural transformation in real time. The corresponding carboxyl conjugated derivatives were formed in situ and developed into the closely packed and ordered molecular architectures via hydrogen bonds at the solution-solid surface. The relevant simulations have been utilized to interpret the mechanisms of forming the nanostructures. The corresponding theoretical calculation is used to explain the reaction mechanism. Compared with the traditional ways, the on-surface condensation reaction in situ could not only provide a more convenient method for regulating the self-assembled architectures but also offer a promising strategy for building functional nanostructures and devices.

Progress in the self-assembly of porphyrin derivatives on surfaces: STM reveals

The latest progress in the assembly of porphyrin derivatives on solid surfaces.

Solvent-Dependent Self-Assemblies and Pyridine Modulation of a Porphyrin Molecule at Liquid/Solid Interfaces

On the highly oriented pyrolytic graphite (HOPG) surface, a new porphyrin molecule MT-4 containing a porphine core with six alkyl chains and two carboxyl groups has been explored using scanning tunneling microscopy (STM) technology. Solvent and pyridine regulation have been proved to be two effective ways to control and tune the supramolecular structure of MT-4 at interfaces. Different high-resolution STM (HR-STM) images with highly ordered and closely packed arrangements were gained at the corresponding liquid-solid interface, including phenyl octane (PO), 1-heptanoic acid (HA), and 1-hexanol. Except for the solvent effect, introducing pyridine derivatives such as 4,4'-vinylenedipyridine (DPE) and 4,4'-((1E,1'E)-(2,5-bis(octyloxy)-1,4-phenylene) bis(ethene-2,1-diyl)) dipyridine (PEBP-C8) is also effective to modulate the self-assembly of MT-4. With careful analysis of the STM pictures and the density functional theory (DFT) computational exploration, we figured out the molecular model, interaction energies, and self-assembly mechanism of each system at the interface. This work provides a simple and effective approach for quickly building diverse nanoarchitectures by utilizing different noncovalent interactions. Meanwhile, it would give a perspective to regulate and control self-assembly arrays for devising novel molecular-based materials through more optimal strategies.

Solvent-Dependent Core-Modified Rubyrin Self-Assembly at Liquid/Solid Interfaces

Scanning tunneling microscopy (STM) was utilized to disclose four novel core-modified rubyrin self-assembly behaviors on the highly-oriented pyrolytic graphite (HOPG) surface, of which N₂S₄-OR(1)/N₂Se₄-OR(2) had no phenanthrene pyrrole ring and N₂S₄-OR(3)/N₂Se₄-OR(4) had phenanthrene-fused pyrrole rings and meso-aryl substituents. It was discovered that the core-modified rubyrin could self-assemble into either face-on or edge-on monolayer structures selectively at the liquid/HOPG interface in different solvents. There was an obvious solvent-dependent self-assembly for N₂S₄-OR(3)/N₂Se₄-OR(4), which adopted an edge-on and face-on structure in 1-phenyloctane and 1-heptanoic acid solvents, respectively, whereas N₂S₄-OR(1)/N₂Se₄-OR(2) showed no obvious difference in the assembly structure, which both adopted a face-on structure in the two solvents. Density functional theory (DFT) calculations were also utilized to reveal the relevant self-assembly mechanisms. This study shows a typical solvent effect regulating core-modified rubyrin self-assembly, which is essential for porphyrin-based functional devices' design and manufacture.

Self-assembled flower structures formed by C3-symmetric aromatic carboxylic acids with meta-carboxyl groups

H₆BTE self-assembled into flower-like structures with two types of cavities at the HA/HOPG interface, and the guest molecule COR was only trapped in the A-type cavities at low and high concentrations of COR.

Advances in the regulation of bipyridine derivatives on two-dimensional (2D) supramolecular nanostructures

In this review, we discuss a series of two-dimensional (2D) supramolecular nanostructures prepared on highly oriented pyrolytic graphite (HOPG) by STM.

Assemblies of porphyrin and phthalocyanine derivatives studied by STM

Porphyrins and phthalocyanines are currently a prevalent topic with great potential due to their abundant photonic/electronic properties. The study of porphyrin or phthalocyanine supramolecular architectures on solid surfaces is laying the foundation for the further development of molecular electronics or other structures in applications. Above all, the invention of scanning tunneling microscopy (STM) has opened a new path to explore these concepts on surfaces. Self-assemblies on solid surfaces can be probed with STM at submolecular resolutions to disclose the conformations and arrangements of molecules on an individual molecule basis. In this paper, the progress of STM research on porphyrin and phthalocyanine derivatives over past ten years is reviewed. We introduce the self-assembled structures of different porphyrins or phthalocyanines. Throughout the review, the structures, thermodynamics, and dynamics have been emphasized, which are essential current and future research themes.

On-Surface Synthesis of Self-Assembled Monolayers of Benzothiazole Derivatives Studied by STM and XPS

On-surface synthesis has gradually become a prevalent approach to constructing two-dimensional functional monolayers on various substrates. In the present work, the synthesis of self-assembled monolayers (SAMs) of benzothiazole derivatives was conducted at the liquid/solid interface for the first time. Two kinds of nanostructures were achieved on the highly oriented pyrolytic graphite (HOPG) surface via the condensation reaction between aromatic aldehyde derivatives and 2-aminothiophenol (ATP). The formation of thiazole-based self-assemblies was revealed by scanning tunneling microscopy (STM) and further confirmed by X-ray photoelectron spectroscopy (XPS). The successful synthesis of the benzothiazole derivatives not only extends the scope of on-surface reactions but also can be applied in designing multifunctional SAMs at the interface.