Photochromic behavior of a bisthienylethene bearing Cu(I)-1,10-phenanthroline complexes

A novel diarylethene having a 1,10-phenanthroline unit at each end of the molecule has been synthesized. Among the metal ions, it formed a stable complex with Cu(I) ions in acetonitrile. Rational structures of the Cu(I) complexes of the colorless and the photo-generated blue form have been given by PM3 semiempirical molecular orbital calculations to be 2:2 cyclic complexes for both isomers, with the complex of the open form belonging to the C2 symmetry group while the complex of the closed form belongs to the D2 symmetry group. Although the ring-closing quantum yield for free diarylethene in acetonitrile was 0.75, that for the complex was 0.026, due to the long distance of the bond-forming carbon atoms in the rigid (open form)2-Cu(I)2 complex.

► A novel bisthienylethene having a 1,10-phenanthroline unit at each end of the molecule has been synthesized.
► It formed a stable complex with Cu(I) ions in acetonitrile.
► Rational complex structures for both colorless and colored forms were given by MO calculations to be 2:2 cyclic.
► Although the ring-closing quantum yield for free diarylethene in acetonitrile was 0.75, that for the complex was 0.026.
► This is due to the long distance of the bond-forming carbon atoms in the rigid complex.