Stable Spiro‐Fused Diarylaminyl Radicals: A New Type of a Neutral Mixed‐Valence System

• Published in: Chemistry : a European journal Vol. 29; no. 43; pp. e202301250 - n/a
• Main Authors: Sentyurin, Vyacheslav V., Levitskiy, Oleg A., Bogdanov, Alexey V., Yankova, Tatiana S., Dorofeev, Sergey G., Lyssenko, Konstantin A., Gontcharenko, Victoria E., Magdesieva, Tatiana V.
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01.08.2023
• Subjects: Chemistry; Electron transfer; Materials science; mixed-valence compounds; Radicals; redox chemistry; spiro compounds; electron transfer; radicals; spiro compounds; mixed-valence compounds; redox chemistry
• ISSN: 0947-6539; 1521-3765; 1521-3765
• DOI: 10.1002/chem.202301250

A new type of neutral mixed‐valence system was synthesized using a facile one‐pot procedure. The spiro‐conjugated framework is additionally “fastened” with a biphenyl bridge, which does not directly participate in spin delocalization but makes the molecule stable and influences the reorganization energy and the energy barrier of the intramolecular electron transfer. The in‐depth experimental and quantum‐chemical study allowed determining the radicals as the Class II Robin‐Day‐mixed‐valence systems. The structure of the radicals was confirmed by the X‐ray data, which are relatively rare for Class II MV molecules. Advanced properties of the radicals, such as an ambipolar redox behavior and panchromatic absorption in the visible and NIR regions, along with their stability, make them of interest for materials science. All radicals demonstrate the SOMO‐HOMO inversion phenomenon, which was supported by the DFT and the experimental study. The first example of stable spiro‐fused diarylaminyl radicals that are radical cations with the “canceled charge” was obtained. The radicals belong to Class II Robin‐Day neutral mixed‐valence systems that are rare. They are valuable models to mimic natural electron transfer reactions promoting a deeper understanding of their mechanism. The advanced properties of the radicals make them of potential interest in materials science.