Intramolecular Magnetic Interaction of Spin-Delocalized Neutral Radicals through m-Phenylene Spacers.

A new diradical having two 4,8,10-trioxotriangulene (TOT) neutral radical units linked through an m-phenylene moiety was synthesized and characterized by ESR measurements. An electrochemical study showed that the diradical undergoes two one-electron reductions to generate corresponding dianion species, suggesting the electronic interaction between two TOT units through the π-conjugated spacer. A strong intramolecular interaction between the two TOT units gives rise to the spin-projected small hyperfine couplings in comparison with those of the monomer. Furthermore, the temperature dependent ESR measurement revealed that the dimer behaves as an S=1 species in the ground state with a ferromagnetic interaction of 2 J/kB =+7±3 K.