A diarylethene possessing one [4]thiaheterohelicene and one benzothiophene, the latter with a chiral methoxymethoxyethyl group on its C-3 position, was proved to work as a switch of specific optical rotation at a wavelength at which both colored and colorless forms have no absorption in solution. The difference of the specific optical rotation was 1300 degrees between the open form and the photostationary state. The specific optical rotation of one of the isolated optically active major colored forms was -4680 degrees. The conversion to the colored form was 64%, and the diastereomeric excess of photocyclization was 47%.
While the association constant of the colored form of a thermally irreversible photochromic indolylfulgimide with 2, 6-bis (octanoylamino)pyridine in toluene at 21 °C was 156 ± 11 mol−1 dm3 through triplex hydrogen bonding, that of its colorless form, generated by visible-light irradiation, was increased to 885 ± 63 mol−1 dm3. This result was supported by PM3 semiempirical molecular–orbital calculations that the difference of the association constants between the C-form and the E-form was mainly due to differences in the structures and conformations of the imide moiety.
An indolylfulgide derivative possessing an orthoester-type functional group on the acid anhydride moiety with a C2-symmetric (S,S)-1,2-bis(1-hydroxypropyl)benzene was prepared. Irradiation of 313-nm light produced the colored form in 90% diastereomer excess. The [α]D values for the colorless and the colored forms in toluene were +82° and −420°, respectively.
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