Unprecedented radical-radical reaction of a [2.2]paracyclophane derivative containing an imidazolyl radical moiety

Pseudogem-DPIM-DPI[2.2]PC dimer (3), with a C-N bond between the [2.2]paracyclophane ([2.2]PC) moiety and the imidazole ring, was synthesized. This is the first crystallographic observation of a highly sterically constrained 1-ene-2,5-cyclohexadiene structure for a [2.2]PC derivative. Compound 3 shows a photochromic behavior, exhibiting a color change from pale yellow to green upon either UV or visible light irradiation, both in the solid state and in solution at room temperature.