Conjugation‐Induced Spin Delocalization in Helical Chiral Carbon Radicals via Through‐Bond and Through‐Space Effects

Abstract

Abstract A class of highly stable hydrocarbon radicals with helical chirality are synthesized, which can be isolated and purified by routine column chromatography on silica gel. These carbon‐centered radicals are stabilized by through‐bond delocalization and intramolecular through‐space conjugation, which is evidenced by Density Functional Theory (DFT) calculation. The high stability enables to directly modify the carbon radical via palladium‐catalyzed cross‐coupling with the radical being untapped. The structures and optoelectronic properties are investigated with a variety of experimental methods, including Electron Paramagnetic Resonance (EPR), Ultraviolet Visisble Near Infrared (UV–vis–NIR) measurements, Cyclic Voltammetry (CV), Thermogravimetry Analysis (TGA), Circular Dichroism (CD) spectra, High‐Performance Liquid Chromatography (HPLC), and X‐ray crystallographic analysis. DFT calculations indicated that the 9‐anthryl helical radical is more stable than its tail‐to‐tail σ‐dimer over 13.2 kJ mol−1, which is consistent with experimental observations.

Keywords

• cross‐coupling reactions
• helical chirality
• stable carbon radicals
• through‐space delocalization