One- and Two-Dimensional Polymorphism in a Hydrogen-Bonding Bis-Ureido-Squaramide.

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Organic Chemistry

Background:

• Bis-ureido-squaramide (USq) units are known for their hydrogen bonding capabilities.
• Controlling self-assembly and polymorphism in synthetic molecules is crucial for developing advanced materials.

Purpose of the Study:

• To design and characterize a novel bis-ureido-squaramide (USq) monomer.
• To investigate the self-assembly behavior of the USq monomer in solution and solid states.
• To explore the potential of USq as a building block for supramolecular materials.

Main Methods:

• Synthesis of the bis-USq monomer.
• Solution-phase studies using concentration and temperature variations.
• Microscopic observations (e.g., microscopy).
• Theoretical calculations (e.g., computational modeling).
• Solid-state characterization of polymorphs (e.g., X-ray diffraction, thermal analysis).

Main Results:

• The bis-USq monomer exists as a folded conformation stabilized by intramolecular hydrogen bonds in chloroform.
• Self-assembly leads to a 2D supramolecular polymer (AggA) driven by quadruple hydrogen bonds, π-π stacking, and van der Waals forces, not the expected main-chain polymers.
• The 2D assembly is preserved as a lamellar phase (1-Lam) in the solid state.
• Thermal treatment induces a phase transition to a more stable 1D columnar structure (1-Col).
• Both solid-state polymorphs share similar hydrogen bonding but differ in molecular packing.

Conclusions:

• The USq unit is a versatile moiety for constructing tunable supramolecular assemblies.
• The study highlights the complexity of self-assembly pathways and polymorphism in solution and solid states.
• This research provides a platform for developing new supramolecular materials with tailored properties.