Novel fluorinated amino-stilbenes and their solid-state photodimerization

We synthesized a series of polyfluoro-amino-stilbenes in satisfactory yields by Wittig reaction of 4-piperazinyl-benzalhehydes with pentafluoro-benzylidene-triphenyl-phosphorane and we analyzed the photochemical behavior of these stilbenes in the solid state; thanks to arene-perfluoroarene pi-pi interactions, some of them have shown a good propensity to give the corresponding cyclobutane photodimers in quantitative yields. The photocyclization is reversible both in solution and in polymeric matrix, affording the corresponding stilbenes with different cis-trans stereo-selectivity.