Enhanced host-guest interaction between [10]cycloparaphenylene ([10]CPP) and [5]CPP by cationic charges.

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Nanotechnology

Background:

• Cycloparaphenylenes (CPPs) are macrocyclic aromatic compounds with unique structures.
• Host-guest complexation is crucial for designing novel molecular architectures.
• Previous studies have explored neutral CPP-based host-guest systems.

Purpose of the Study:

• To synthesize and characterize the shortest double-layer carbon nanotube complex, [10]CPP⊃[5]CPP²⁺.
• To investigate the binding affinity of a dicationic CPP guest within a neutral CPP host.
• To elucidate the driving forces behind the enhanced complex stability.

Main Methods:

• Selective encapsulation of a dicationic [5]cycloparaphenylene ([5]CPP²⁺) by a neutral [10]cycloparaphenylene ([10]CPP).
• Association constant measurements in (CDCl₂)₂ at 25 °C.
• Electrochemical and photophysical analyses.
• Theoretical calculations.

Main Results:

• The formation of the shortest double-layer carbon nanotube, [10]CPP⊃[5]CPP²⁺.
• The dicationic complex ([10]CPP⊃[5]CPP²⁺) showed an approximately 20-fold higher association constant compared to the neutral complex ([10]CPP⊃[5]CPP).
• Evidence of partial electron transfer from [10]CPP to [5]CPP²⁺, indicating a charge-transfer interaction.

Conclusions:

• The enhanced association constant of the dicationic complex is attributed to charge-transfer interactions.
• This study demonstrates the potential of electrostatic and charge-transfer interactions in stabilizing supramolecular assemblies.
• The findings contribute to the understanding of host-guest chemistry with charged guests and the design of novel carbon nanotube-like structures.