Captodative Approach to Stable Nitrogen-Centered Radicals, Anions, and Cations Exhibiting Near-Infrared...

Area of Science:

• Materials Science
• Organic Chemistry
• Electrochemistry

Background:

• Redox interconversion of nitrogen oxidation states is key for stimuli-responsive materials.
• Interconversion via electron transfer is challenging due to reactive nitrogen species: aminyl radicals, amide anions, and nitrenium cations.

Purpose of the Study:

• To stabilize and interconvert aminyl radicals, amide anions, and nitrenium cations within a single molecular scaffold.
• To explore the potential of a captodative approach for stabilizing reactive nitrogen species.
• To investigate the resulting material properties, including electrochromism.

Main Methods:

• Synthesis of a 9,10-dihydroacridine derivative with specific nitrogen doping and imide substitutions.
• Generation of an aminyl radical via hydrogen abstraction using lead dioxide (PbO2).
• Controlled electron transfer to generate amide anions and nitrenium cations.
• Spectroscopic analysis to characterize the nitrogen species and their redox states.

Main Results:

• A stable 9,10-dihydroacridine derivative successfully stabilized aminyl radicals, amide anions, and nitrenium cations under ambient conditions.
• Redox interconversion between the amide anion and nitrenium cation induced significant changes in near-infrared (NIR) absorption.
• The molecule exhibited electrochromism in the NIR region (up to 1050 nm) due to switching aromaticity.

Conclusions:

• The captodative strategy effectively stabilizes highly reactive nitrogen-centered radical and ionic species.
• This work opens new avenues for designing advanced stimuli-responsive materials and molecular switches.
• The observed NIR electrochromism highlights the potential for applications in optical devices and sensors.