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Terminal Group Effect on Two-Dimensional Self-Assembly of Fluorenone-Based Liquid Crystals at the Solid/Liquid
Songyao Zhang1, Shibo Chen2, Tao Ma2
1College of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, People's Republic of China.
Langmuir : the ACS Journal of Surfaces and Colloids
|January 9, 2024
Summary
Researchers studied fluorenone derivatives (FE and FEC) self-assembly using scanning tunneling microscopy (STM) and density functional theory (DFT). FE showed concentration-dependent structures, while FEC formed oval shapes via hydrogen bonds, revealing key intermolecular forces.
Area of Science:
- Materials Science
- Supramolecular Chemistry
- Surface Science
Background:
- Fluorenone derivatives are key components in advanced materials.
- Understanding molecular self-assembly is crucial for designing functional materials.
- Polycatenars with polar moieties exhibit complex self-assembly behaviors.
Purpose of the Study:
- To investigate the self-assembly of two fluorenone-based derivatives (FE and FEC) at the 1-octanoic acid/highly oriented pyrolytic graphite (HOPG) interface.
- To elucidate the influence of concentration and terminal groups on self-assembly structures.
- To determine the driving forces behind the observed molecular packing.
Main Methods:
- Scanning Tunneling Microscopy (STM) to visualize self-assembled structures.
- Density Functional Theory (DFT) calculations to understand intermolecular interactions.
- Controlled variation of molecular concentration at the liquid-solid interface.
Main Results:
- FE exhibited concentration-dependent polymorphic self-assembly, forming dimers, bracket-like, and ribbon-like structures.
- FEC exclusively formed oval-shaped structures through intermolecular N···H-O hydrogen bonds with solvent molecules.
- STM and DFT collectively identified van der Waals forces, dipole-dipole interactions, and hydrogen bonding as primary stabilization forces.
Conclusions:
- The study clarifies the role of intermolecular interactions and conformational effects in the formation of molecular packing structures.
- Findings provide molecular-level insights into the self-assembly of polar polycatenars.
- The research contributes to the understanding of liquid crystal properties arising from molecular packing.
