Synthesis and Magnetic Properties of (Pyrrolidin-1-oxyl)-(Nitronyl Nitroxide)/(Iminonitroxide)-Dyads.

Unlike extensively studied diradicals linked by π-conjugated systems, only a few studies have investigated weakly coupled diradicals linked by an sp3 carbon atom. Herein, we prepared pyrrolidin-1-oxyl-(nitronyl nitroxide)-dyad 5 and pyrrolidin-1-oxyl-iminonitroxide-dyad 6. From the observed temperature dependence of the magnetic susceptibility, 5 and 6 were determined to be in singlet ground states with 2Jintra /kB =-35.2 K and -13.6 K, respectively. From these results and theoretical calculations of related diradicals, the spin-polarization model counting the small spin density of the sp3 carbon atom could be used as a spin-prediction model.