Giant Cavity Macrocycle: Synthesis, Structure, and Its Complexation with Pagoda[5]arene

Area of Science:

• Supramolecular Chemistry
• Organic Chemistry
• Materials Science

Background:

• Pillar[n]arenes are macrocyclic hosts with tunable cavity sizes.
• Naphthalene diimides are electron-deficient guests often used in host-guest chemistry.
• Developing novel host molecules with high selectivity is crucial for molecular recognition.

Purpose of the Study:

• To synthesize and characterize a novel stretched hexagon structure naphthalene diimides-extended-pillar[6]arene (1).
• To investigate the host-guest binding properties of 1, particularly its selectivity.
• To elucidate the key interactions responsible for the formation of stable supramolecular complexes.

Main Methods:

• Synthesis of the naphthalene diimides-extended-pillar[6]arene macrocycle.
• Spectroscopic characterization (NMR, Mass Spectrometry).
• Binding studies using techniques like titration and X-ray crystallography to determine selectivity and complex structure.

Main Results:

• A novel stretched hexagon structure naphthalene diimides-extended-pillar[6]arene (1) was successfully synthesized.
• Compound 1 possesses a giant cavity size (18.769 Å width, 17.109 Å height).
• 1 demonstrated highly selective binding of pagoda[5]arene over pillar[5]arene and prism[5]arene.

Conclusions:

• The synthesized macrocycle 1 is a promising host molecule for selective guest recognition.
• Size matching between the host cavity and the guest molecule is a critical factor for binding.
• Charge transfer interactions significantly contribute to the stability of the observed ring-in-ring complexes.