Tetraazacyclophanes by palladium-catalyzed aromatic amination. Geometrically defined, stable, high-spin diradicals

[GRAPHICS] Neutral tetraazacyclophanes were prepared in a one-step palladium-catalyzed amination reaction, Simple oxidation of these materials creates dication diradicals that are stable at room temperature and that are geometrically well defined. The electronic and magnetic properties of the dications were investigated by CV, UV-vis, and EPR spectroscopy. These spectral data and solution phase magnetic susceptibility measurements indicate high spin ground states in certain media. EPR zero field splitting parameters for the diradical suggest that the distance between the two radical sites can be approximated simply by the distance between alternating nitrogens in the macrocycle.