A Benzene-1,3,5-Triaminyl Radical Fused with Zn II -Porphyrins: Remarkable Stability and a High-Spin Quartet Ground State.

A benzene-1,3,5-triaminyl radical fused with three ZnII -porphyrins was synthesized through a three-fold oxidative fusion reaction of 1,3,5-tris(ZnII -porphyrinylamino)benzene followed by oxidation with PbO2 as key steps. This triaminyl radical has been shown to possess a quartet ground state with a doublet-quartet energy gap of 3.1 kJ mol-1 by superconducting quantum interference device (SQUID) studies. Despite its high-spin nature, this triradical is remarkably stable, which allows its separation and recrystallization under ambient conditions. Moreover, this triradical can be stored as a solid for more than one year without serious deterioration. The high stability of the triradical is attributed to effective spin delocalization over the porphyrin segments and steric protection at the nitrogen centers and the porphyrin meso positions.