Systematic radical species control by electron push-pull substitution in the perylene-based D-π-A compounds

Area of Science:

• Materials Science
• Organic Chemistry
• Physical Chemistry

Background:

• Organic radical materials are known for high energy and reactivity, but controlling their radical species beyond stabilization is difficult.
• Existing research primarily focuses on stabilizing radical species, leaving design strategies for controlled radical generation underdeveloped.

Purpose of the Study:

• To explore a new strategy for controlling radical species in organic materials.
• To investigate the electronic push-pull effect on perylene-based donor-π-acceptors (D-π-A) to tune their properties from neutral to radical states.

Main Methods:

• Synthesized a series of perylene-based donor-π-acceptors (D-π-A) with varying electron-withdrawing and -donating R groups.
• Applied external electrical stimulus to transform D-π-A into radical cations ((D-π-A)˙+) and radical anions ((D-π-A)˙-) at redox-active sites.
• Utilized UV-Vis spectroscopy to observe changes in absorption peaks and spectral shifts.
• Employed Density Functional Theory (DFT) and Time-Dependent DFT (TD-DFT) calculations to analyze electronic structures and radical properties.

Main Results:

• Introduced electron-withdrawing and -donating R groups to control intramolecular interactions at the HOMO level, enabling radical species exploration.
• Observed new absorption peaks upon electrical stimulation, indicating the formation of radical cations and anions.
• Demonstrated that the absorption peaks of radical cations ((D-π-A)˙+) exhibit spectral shifts and intensity changes dependent on the R group, unlike radical anions ((D-π-A)˙-).
• DFT/TD-DFT data confirmed the variability of the radical cationic SOMO level.

Conclusions:

• A novel strategy for systematic control of radical species in organic materials was successfully developed using the electronic push-pull effect.
• The perylene-based D-π-A system provides a versatile platform for generating and tuning radical states.
• This approach offers new possibilities for designing advanced organic electronic materials with tailored properties.