A donor–acceptor coupling unit modulates the spin coupling effect of a stable diradical

Abstract

This study presents the synthesis and characterization of a highly conjugated stable diradical molecule composed of a donor–acceptor coupling unit. The optical, electrochemical, and spintronic properties of this molecule were comprehensively investigated. Triphenylamine served as the electron donor, while 2,1,3-benzothiadiazole was utilized as the electron acceptor for constructing the backbone of the diradical molecule. Two pendant nitronyl nitroxide radicals were incorporated onto the triphenylamine moiety. A comparative study between our diradical molecule and a reference counterpart with only a donor group as the coupling unit revealed intriguing differences in optical properties and singlet-to-triplet energy gap. Our findings demonstrate that the D–A effect induces intramolecular charge polarization on the coupling unit, which subsequently influences the spin–spin interactions of the diradical molecules. Thus, our results offer novel insights into the effective preparation of fully conjugated and stable diradicals, as well as providing a convenient approach for tuning the spintronic and magnetic properties of diradical materials.