Phenylalanine-Based Amphiphilic Self-Assembled Materials: Gels or Crystals?

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Organic Chemistry

Background:

• Amphiphilic and bolamphiphilic amino acid derivatives are building blocks for supramolecular materials.
• The influence of aliphatic side chains on self-assembly is crucial for material properties.

Purpose of the Study:

• To investigate how varying aliphatic side chains in amino acid derivatives affect supramolecular material formation.
• To understand the relationship between molecular structure, hydrogen bonding, and self-assembly behavior.

Main Methods:

• Synthesis of N-lauroyl-L-phenylalanine (Lau-Phe-OH), N-palmitoyl-L-phenylalanine (Pal-Phe-OH), and N,N-azeloyl-L-diphenylalanine (Az-(Phe-OH)2).
• Characterization of self-assembled structures using X-ray diffraction.
• Assessment of gelation and crystallization properties.

Main Results:

• Pal-Phe-OH acts as an efficient gelator, while Az-(Phe-OH)2 forms crystals.
• Lau-Phe-OH initially forms metastable hydrogels that transform into crystals.
• X-ray diffraction revealed hetero-intermolecular hydrogen bonds in Lau-Phe-OH and Pal-Phe-OH, and homo-intermolecular hydrogen bonds in Az-(Phe-OH)2.
• Lau-Phe-OH exhibited higher molecular order than Pal-Phe-OH.

Conclusions:

• The reduced molecular order of Pal-Phe-OH is key to its supergelator efficiency.
• Hydrogen bonding patterns (hetero- vs. homo-) significantly influence the self-assembly outcome (gel vs. crystal).
• Aliphatic side chain length and structure dictate the formation of supramolecular materials.