Mesoscopic self-organization of a self-assembled supramolecular rectangle on highly oriented pyrolytic graphite and Au(111) surfaces

Abstract

A self-assembled supramolecular metallacyclic rectangle was investigated with scanning tunneling microscopy on highly oriented pyrolytic graphite and Au(111) surfaces. The rectangles spontaneously adsorb on both surfaces and self-organize into well ordered adlayers. On highly oriented pyrolytic graphite, the long edge of the rectangle stands on the surface, forming a 2D molecular network. In contrast, the face of the rectangle lays flat on the Au(111) surface, forming linear chains. The structures and intramolecular features obtained through high-resolution scanning tunneling microscopy imaging are discussed.metallacyclic macrocycle ͉ scanning tunneling microscopy ͉ molecular adlayer ͉ molecular orientation S elf-organization (1) and self-assembly (2) are critical and necessary processes in all living organisms and are of ever increasing importance in chemistry and material science. These processes will play a critical role in the so-called ''bottom-up'' strategy of nanofabrication. Therefore, understanding the organization of molecules on solid surfaces is important, both from a fundamental and applied perspective, for the construction of surface molecular nanostructures and nanodevices (3-13). A self-organized molecular pattern with control of structure and derived concomitant function could provide promising materials for the construction of nanodevices that cannot be prepared by conventional microfabrication. The arrangement of adsorbed molecules onto a surface depends on both intermolecular and molecule-surface interactions. For example, Hipps and colleagues (3, 4) prepared a self-organized 2D bifunctional structure on a Au (111) Metal-containing macrocycles with high symmetry and precise architecture are a new class of promising supramolecules for future application in nanotechnology because of their exact shape and size, as well as magnetic, photophysical, and electrostatic properties (14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27). In this article, we describe scanning tunneling microscopy (STM) studies of the self-assembled supramolecular metallacyclic rectangle, cyclobis [(1, ) 2 )anthracene)(1,4Ј-bis(4-ethynylpyridyl)benzene](PF 6 ) 4 , (Fig. 1) (28). The dimensions of a single rectangle molecule were independently determined to be 3.1 nm long by 1.2 nm wide, from the previously reported x-ray crystallographic data (28). The molecular adlayers were prepared on highly oriented pyrolytic graphite (HOPG) and Au(111) surfaces to investigate the effect of substrate on adlayer formation. The molecules self-organize into well ordered 2D adlayers on both surfaces, and high-resolution STM results clearly reveal an intact rectangle on both HOPG and Au (111) surfaces, but the symmetry and molecular orientation the molecules adopt depends on the substrate. Materials and MethodsChemicals. The PF 6 Ϫ salt of the rectangle was prepared analogously to the ClO 4 Ϫ salt previously reported (28), substituting KPF 6 for NaClO 4 .Substrates. HOPG (quality ZYB) was purchased from Digital Instruments (Santa Barbar...

Scanning tunneling microscopy of the formation, transformation, and property of oligothiophene self-organizations on graphite and gold surfaces

“…Linear and folded conformation of the molecules can be seen, as indicated by A and B, respectively. The results once again demonstrate the effect of the substrate on the molecular adlayer formation (21,35). Understanding the intermolecular interaction and molecule/ substrate is very important in fabricating devices by alkylsubstituted oligothiophene molecules.…”

“…On HOPG surface, the adlayer was prepared by depositing a drop (Ϸ2 l) of toluene solution containing Ϸ10 Ϫ5 M 4T-tm-8T or 4T-tm-4T onto freshly cleaved HOPG with an atomically flat surface (35). After evaporation of the solvent, the STM experiments were carried out in atmosphere with a Nanoscope IIIa scanning probe microscope (Digital Instruments).…”

“…STM tips were made from mechanically cut Pt/Ir wire (90/10). On the Au(111) surface, the molecular adlayers were prepared by immersing the single- crystal Au bead into the above-mentioned solution containing the sample molecules for 3-5 min (35,39). After formation of the molecular adlayer, the Au bead was thoroughly rinsed with Milli-Q water to remove the remnant molecules and mounted into the STM electrochemical cell.…”

Principles of molecular assemblies leading to molecular nanostructures

“…Comparative studies describing the adsorption of a single building block on two different substrates are relatively scarce [51]. Nevertheless, one readily expects that the substrate lattice and thus the registry effects will be different for different substrates, which implies that the strength of molecule-substrate interactions will also be different.…”

Two‐Dimensional Self‐Assembly of a Porphyrin–Polypyridyl Ruthenium(II) Hybrid on HOPG Surface through Metal–Ligand Interactions

“…[6] To achieve these goals, an efficient interaction between the porphyrin derivatives is required. Hydrogen bonding, [7,8] metal-ligand coordination [9][10][11] and conjugated p-bonding, [7,12] were used to construct ordered porphyrin derivative arrays, which led to the thermodynamically most stable structure and spontaneous self-repair. A large number of previous researches have mainly focused on the self-assembly of porphyrin derivatives on HOPG surface at a liquid/solid interface and at an air/solid interface in ambient and UHV conditions.…”