Exploring the Complexity of Supramolecular Interactions for Patterning at the Liquid–Solid Interface

Abstract

The use of self-assembly to fabricate surface-confined adsorbed layers (adlayers) from molecular components provides a simple means of producing complex functional surfaces. The molecular self-assembly process relies on supramolecular interactions sustained by noncovalent forces such as van der Waals, electrostatic, dipole-dipole, and hydrogen bonding interactions. Researchers have exploited these noncovalent bonding motifs to construct well-defined two-dimensional (2D) architectures at the liquid-solid interface. Despite myriad examples of 2D molecular assembly, most of these early findings were serendipitous because the intermolecular interactions involved in the process are often numerous, subtle, cooperative, and multifaceted. As a consequence, the ability to tailor supramolecular patterns has evolved slowly. Insight gained from various studies over the years has contributed significantly to the knowledge of supramolecular interactions, and the stage is now set to systematically engineer the 2D supramolecular networks in a "preprogrammed" fashion. The control over 2D self-assembly of molecules has many important implications. Through appropriate manipulation of supramolecular interactions, one can "encode" the information at the molecular level via structural features such as functional groups, substitution patterns, and chiral centers which could then be retrieved, transferred, or amplified at the supramolecular level through well-defined molecular recognition processes. This ability allows for precise control over the nanoscale structure and function of patterned surfaces. A clearer understanding and effective use of these interactions could lead to the development of functional surfaces with potential applications in molecular electronics, chiral separations, sensors based on host-guest systems, and thin film materials for lubrication. In this Account, we portray our various attempts to achieve rational design of self-assembled adlayers by exploiting the aforementioned complex interactions at the liquid-solid interface. The liquid-solid interface presents a unique medium to construct flawless networks of surface confined molecules. The presence of substrate and solvent provides an additional handle for steering the self-assembly of molecules. Scanning tunneling microscopy (STM) was used for probing these molecular layers, a technique that serves not only as a visualization tool but could also be employed for active manipulation of molecules. The supramolecular systems described here are only weakly adsorbed on a substrate, which is typically highly oriented pyrolytic graphite (HOPG). Starting with fundamental studies of substrate and solvent influence on molecular self-assembly, this Account describes progressively complex aspects such as multicomponent self-assembly via 2D crystal engineering, emergence, and induction of chirality and stimulus responsive supramolecular systems.

Evolution of Graphene Molecules: Structural and Functional Complexity as Driving Forces behind Nanoscience

“…Additionally, STM was accompanied by scanning tunneling spectroscopy (STS) to gather information on the electronic structure of the surface-immobilized PAHs and to compare this information with the outcome of other spectroscopic characterization. 37,38 Scheme 4: From non-planar polyphenylene precursors to disc-type graphene molecules.…”

Effects of Alkyl Chain Length and Hydrogen Bonds on the Cooperative Self‐Assembly of 2‐Thienyl‐Type Diarylethenes at a Liquid/Highly Oriented Pyrolytic Graphite (HOPG) Interface

“…[1][2][3][4][5][6][7][8] Two-dimensionalc rystal engineering at liquid/solid interfaces has attracted growing attention in the last decade. [9][10][11][12][13][14][15] To efficiently design and predict the formationo ft hermodynamically stable molecular ordering formed through self-assembly processes, interplays of various interactions,s uch as molecule-substrate interactions,i ntermoleculari nteraction, [16][17][18][19][20] solvent effects, [21][22][23][24][25] and the balance of enthalpy and entropyt erms, [26][27][28][29] must be taken into account.…”

“…[1,26,29,[47][48][49][50][51][52] For precise control over the dynamics of stimuli-responsive nanostructures, an insight into the self-assembly process is of particular significance. [53] We previously reported the photoinduced formation and disappearance of 2D molecular ordering composed of ap hotochromic 2-thienyl-type diarylethene derivative.…”

An STM Investigation on a Metal Induced Structural Evolution of an m-Substituted Bipyridine Derivative on Highly Oriented Pyrolytic Graphite

“…[1][2][3][4] Among all patterns prepared via "bottom-up" routes, the surface confined self-assemblies constituted by molecules have attracted intensive interests, contributable to their potential applications in engineering functional surfaces. [4][5][6][7][8][9][10] To achieve appropriate functionality of the self-assembly decorated surface, the precise arrangement of block molecules on substrate is highly desired, considering the intimate relationship between the low-dimensional surface confined nanopatterns and the performance of the obtained surfaces. [1,9,[11][12][13][14][15][16][17][18][19][20] In this case, the design concept based on the on-surface metal-organic coordination is handy, for its capacity in obtaining the surface confined nanostructures with regular patterns.…”