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. A π‐conjugated neutral diradical of 4,8,10‐trioxotriangulene (TOT) linked through the m‐phenylene spacer was synthesized. The electronic spin and SOMO of the TOT units delocalized over the whole molecular skeleton through the π‐spacer, and the dimer showed strong intramolecular electronic and magnetic interactions. ESR measurements revealed the S=1 ground state of the dimer with a ferromagnetic interaction of 2 J/kB=+7±3 K.