Development and Application of (Stable Radical)-substituted Radical Ions

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Radical-substituted radical ions with strongly ferromagnetic intramolecular interaction are attractive species as spin-building blocks of magnetic materials. In most cases, these species are unstable. We have recently prepared, for the first time, nitronyl nitroxide-substituted dihydrophenazine radical cation, which is a stable compound at room temperature under aerated conditions and has a strongly ferromagnetic intramolecular interaction of J>700K. In order to construct magnetic materials based on the radical-substituted radical ions, we aim at preparing several derivatives of this class of compounds. The following guidelines are taken for the purpose ; 1) the readily oxidizable and reducible π-system which should give stable radical ions are essential, 2) the π-system radical ions should have a large spin density at the carbon atoms on which stable radical is introduced, 3) the π-system radical ions are hoped to have a property giving good quality of crystals. The requirement 2) is … More important to get a strong ferromagnetic nature between the attached radical and radical ion spins. The requirement 3) is critical to develop the magnetic materials.We have examined various radical cations such as p- and m-phenylene bridged dihydrophenazine derivatives, benzoxazinophenoxazines, benzothiazinophenoxazines, and heteroatom-bridged planar triphenylamine derivatives, and radical anions such as thienoqunoid radical anions involving those with 1,4-diazacyclopentadien-2-ylidene terminals and dicyanomethylene terminals. All these compounds are new compounds. We could isolate the radical cation species in all cases. For the radical anions, the thienoqunoids with dicyanomethylene terminals were found to be stable : Thus, the requirements 1) and 2) were satisfied but the requirement 3) was hard to satisfy for most cases. Fortunately, the trisoxytriphenylamine (TOT) radical cation gave good crystals in various conditions. We synthesized nitronyl nitroxide-substituted TOT. Then, we could readily isolate nitronyl nitroxide-substituted TOT radical cations as PF_6, GaCl_4, and FeCl_4 salts. For dihydrophenazine derivatives, we have succeeded to prepare verdazyl-substituted dihydrophenaznines as similar salts. Application of these compounds as purely organic magnetic systems are planned. Less