Photoinduced Electron Transfer in Inclusion Complexes of Carbon Nanohoops

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Photochemistry

Background:

• Photoinduced electron transfer (PET) in carbon materials is crucial for light energy conversion.
• Carbon materials like fullerenes and cycloparaphenylenes (CPPs) exhibit unique electronic properties suitable for PET research.
• These materials are vital components in photovoltaic devices, serving as transport layers, electrodes, or additives.

Purpose of the Study:

• To investigate the impact of structural modifications on PET efficiency in carbon nanohoop-fullerene inclusion complexes.
• To understand how altering host and guest molecules influences charge separation and recombination dynamics.
• To computationally design novel carbon nanohoop systems for optimized photoactive applications.

Main Methods:

• Utilized time-dependent density-functional theory (TD-DFT) with the Tamm-Dancoff approximation (TDA) and CAM-B3LYP functional for excited state calculations.
• Employed nonadiabatic electron transfer theory to quantify electron transfer rates.
• Modeled charge separation and recombination in synthesized and computationally designed inclusion complexes.

Main Results:

• Incorporating π-conjugated fragments or antiaromatic units into carbon nanohoops alters photophysical properties and introduces new charge transfer states.
• Perfluorination transforms nanohoops from electron donors to acceptors; vacancy defects hinder PET, while extended π-systems enhance donor properties.
• The aromaticity of nanohoop units dictates electron transfer direction, with aromatic units typically acting as donors and antiaromatic units as acceptors.

Conclusions:

• Structural modifications of carbon nanohoops, including π-conjugation, perfluorination, and antiaromaticity, provide effective control over PET efficiency.
• Charged fullerenes demonstrate superior electron acceptor capabilities compared to neutral C60.
• Strategic design of donor-acceptor systems, considering charge location and solvent polarity, can lead to enhanced photovoltaic performance with tunable charge transfer bands.