Synthesis and photochromic properties of 1,2-dicyano[2.n]metacyclophan-1-enes

Novel synthesis and the photochromic properties of 1,2-dicyano[2.n]metacyclophan-1-enes are reported. The intramolecular cyclization of bis(cyanomethyl)arenes successfully afforded 1,2-dicyano[2.n]metacyclophan-1-enes in good yield. The obtained cyclophanes show photochromism and the lifetime of the colored form is dependent on the chain length (n).