Dual association modes of the 2,5,8-tris(pentafluorophenyl)phenalenyl radical.

The 2,5,8-tris(pentafluorophenyl)phenalenyl radical was obtained by a straightforward synthesis in 11 steps from 2,7-dibromonaphthalene. This radical crystallized as a σ dimer from a solution in MeCN and as a π-stack from a melted liquid. The π stack was not confined to dimerization, but extended into a uniform 1D stack with an interplanar distance of 3.503 Å. This unique duality in association mode arose from the thermodynamic stability of the phenalenyl moiety.