Perchloro-2,5,8-triazaphenalenyl radical.

[reaction: see text] The unusually stable perchloro-2,5,8-triazaphenalenyl radical 1 and its twisted dechlorinated dimer 2 were synthesized and characterized by ESR spectroscopy and X-ray crystallography. The X-ray structure of dimer 2 shows that the double bond connecting the two triazaphenalene systems is strongly twisted. Dimer 2 has a dramatic color shift from the solid state to solution, which may be due to a change of the twisting angle between both states.