Self-Assembled Nanostructures of Oligopyridine Molecules

Abstract

The high potential of self-assembly processes of molecular building blocks is reflected in the vast variety of different functional nanostructures reported in the literature. The constituting units must fulfill several requirements like synthetic accessibility, presence of functional groups for appropriate intermolecular interactions and depending on the type of self-assembly processsignificant chemical and thermal stability. It is shown that oligopyridines are versatile building blocks for two- and three-dimensional (2D and 3D) self-assembly. They can be employed for building up different architectures like gridlike metal complexes in solution. By the appropriate tailoring of the heterocycles, further metal coordinating and/or hydrogen bonding capabilities to the heteroaromatic molecules can be added. Thus, the above-mentioned architectures can be extended in one-step processes to larger entities, or in a hierarchical fashion to infinite assemblies in the solid state, respectively. Besides the organizational properties of small molecules in solution, 2D assemblies on surfaces offer certain advantages over 3D arrays. By precise tailoring of the molecular structures, the intermolecular interactions can be fine-tuned expressed by a large variety of resulting 2D patterns. Oligopyridines prove to be ideal candidates for 2D assemblies on graphite and metal sufaces, respectively, expressing highly ordered structures. A slight structural variation in the periphery of the molecules leads to strongly changed 2D packing motifs based on weak hydrogen bonding interactions. Such 2D assemblies can be exploited for building up host-guest networks which are attractive candidates for manipulation experiments on the single-molecule level. Thus, "erasing" and "writing" processes by the scanning tunneling microscopy (STM) tip at the liquid/solid interface are shown. The 2D networks are also employed for performing coordination chemistry experiments at surfaces.

Molecular Stacking Induced by Intermolecular C–H···N Hydrogen Bonds Leading to High Carrier Mobility in Vacuum‐Deposited Organic Films

“…Examples of the interactions between the B3PyMPM molecules and between the B4PyMPM molecules are shown in Figure a and 4b, respectively. Using molecules having a quite similar chemical structure, it was reported that the intermolecular C–H···N hydrogen bonds and the subsequent two‐dimensional networks were directly observed at the interface between a solution and a graphite surface by scanning tunnelling microscopy (STM) measurements 22–26. Therefore, we can suppose that the hydrogen bonds would be formed even in the vacuum‐deposited films (see Supporting Information Section 5 for details).…”

Control of Molecular Orientation in Organic Semiconductor Films using Weak Hydrogen Bonds

“…Note that asymmetric molecules such as molecules 4 – 6 exhibited almost random orientation even when they had a terpyridyl moiety at the end of the structure (Figure A). These results indicated that multiple H‐bonds formed via two terpyridyl moieties were absolutely essential for horizontal orientation to increase the possibility of forming oligomer‐like aggregates . For OLED applications, the formation of strong H‐bonds was not suitable because the strong molecular interaction tended to cause thin‐film crystallization, such as in 3 , leading to undesirable grain boundaries acting as traps and short circuits of the operating devices .…”

One-dimension-based spatially ordered architectures for solar energy conversion

“…56 Bottom-up approaches do the reverse, by assembling small particles like atoms or molecules into ordered nanostructures. 57 3.1.1 Top-down. Top-down strategies for nanomachining can be subdivided into two categories as illustrated in Fig.…”