Multicomponent assembly of cavitand-based polyacylhydrazone nanocapsules.

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Nanotechnology

Background:

• Cavitands are versatile molecular hosts with tunable properties.
• Polyacylhydrazone linkages offer dynamic and reversible covalent bonds for self-assembly.
• Nanocapsules represent promising scaffolds for various applications, including drug delivery and molecular encapsulation.

Purpose of the Study:

• To report the synthesis of diverse di-, tetra-, and hexacavitand polyacylhydrazone nanocapsules.
• To investigate the self-assembly mechanisms and structural diversity of these nanocapsules.
• To characterize the size and internal structure of the synthesized nanocapsules.

Main Methods:

• Thermodynamically controlled synthesis utilizing cavitands and dihydrazides or trihydrazides.
• Varying stoichiometric ratios of building blocks to control nanocapsule formation.
• Diffusion Nuclear Magnetic Resonance (NMR) spectroscopy and force field calculations for structural and dimensional analysis.

Main Results:

• Successful synthesis of [2+4]-, [4+8]-, and [6+12]-nanocapsules through reactions involving tetraformyl cavitands and dihydrazides.
• Formation of [2+4]- and [6+8]-nanocapsules in varying ratios when using trihydrazides, dependent on reactant ratios and building block nature.
• Solvodynamic radii of hexacavitand nanocapsules measured via NMR range from 1.6 to 2.5 nm, consistent with computational estimates.
• Evidence of solvent-filled, spherical interiors within the nanocapsules, with dimensions similar to small proteins.

Conclusions:

• Thermodynamic control enables the rational synthesis of structurally diverse polyacylhydrazone nanocapsules.
• The conformational strain of acylhydrazone linkages influences the product ratios and assembly outcomes.
• Synthesized nanocapsules possess well-defined, spherical interiors suitable for encapsulating guest molecules, akin to biological systems.