Abstract
AbstractSyntheses and photochromic properties of 1,2‐dicyano[2.n]metacyclophan‐1‐enes are described. Dicyanometacyclophan‐1‐enes have been prepared by novel intramolecular coupling reaction of 1,n‐bis[(cyanomethyl)phenyl]alkanes in the presence of phase transfer catalyst. The photocyclization reaction of the prepared metacyclophan‐1‐enes took place upon irradiation with UV light and the pale yellow solution turned to violet due to the formation of the closed forms. The spectra and the color of the solutions returned to the initial states by the visible irradiation. The lifetimes of the closed forms were dependent on the chain length (n). As the chain length is shorter, the lifetime becomes longer. This is due to the steric energy of metacyclophan‐1‐ene. Hence, it becomes possible to control the thermal stability of the photoisomer by the change of chain length (n). The quantum yield for photocyclization reaction is the highest among 1,2‐dicyanodiarylethene family, since the conformation of the metacyclophan‐1‐ene is fixed to the photoactive form. Synthesis and photochromic properties of 1,2‐ dicyano[2.n]metacyclophan‐1‐enes bearing various kinds of substituents are also described. Copyright © 2007 John Wiley & Sons, Ltd.
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