On-Surface Crystallization Behaviors of H-Bond Donor-Acceptor Complexes at Liquid/Solid Interfaces

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Surface Science

Background:

• Understanding the self-assembly and crystallization of molecules on surfaces is crucial for designing advanced materials.
• Two-dimensional (2D) crystallization offers a unique platform for controlling molecular organization and properties.
• Supramolecular liquid crystals exhibit complex phase behaviors influenced by molecular structure and intermolecular interactions.

Purpose of the Study:

• To investigate the 2D crystallization behaviors of A-TPC_n, T3C₄, and their hydrogen-bonded complexes (T3C₄@TPC_n).
• To elucidate the influence of deposition sequence on the formation of cage-ball structures.
• To explore the coexistence and stability of lattice defects within 2D crystalline networks.

Main Methods:

• Scanning Tunneling Microscopy (STM) for real-space observation of surface structures.
• Density Functional Theory (DFT) calculations for theoretical analysis of molecular interactions and stability.
• Controlled deposition techniques to study the effect of sequence on self-assembly.

Main Results:

• A-TPC₄, A-TPC₁₀, and T3C₄ form distinct self-assembled structures (dumbbell, arrays, zigzag).
• T3C₄@TPC₄ and T3C₄@TPC₆ form cage-ball structures, while T3C₄@TPC₁₀ does not.
• Deposition sequence significantly impacts the filling rate of cage-ball structures; T3C₄ deposited first leads to higher filling.
• Lattice defects coexist with cage-ball structures and exhibit comparable thermodynamic stability.

Conclusions:

• The study provides a comprehensive understanding of 2D crystallization mechanisms for supramolecular liquid crystals.
• The findings highlight the critical role of deposition sequence in directing self-assembly and controlling nanostructure formation.
• The observed coexistence and stability of lattice defects offer insights into the dynamic nature of 2D crystalline networks.