Absolute Stereochemistry and CD Spectra of Resolved Enantiomers of the Colored Form of a Photochromic Dithienylethene

Abstract

The colored form of photochromic 1,2-bis(5-hydroxymethyl-2-methyl-3-thienyl)hexafluorocyclopentene was resolved into enantiomers by HPLC. The absolute stereochemistry of an enantiomer was determined on its bis(4-chlorobenzoate). The CD spectra and optical rotation of the resolved colored form were measured.

A Unified Strategy for Exceptionally High Diastereoselectivity in the Photochemical Ring Closure of Chiral Diarylethenes

“…This photoinduced change is not limited to the color or absorption spectra, as the change occurs between two different molecules with different physical and chemical properties. When a photochromic compound is chiral and non‐racemic,2 its chiroptical properties such as circular dichroism spectra3, 4 and optical rotation5–7 also change reversibly. These chiral and chiroptical differences can be used to: 1) detect the state of the system without inducing any property change,5–7 2) induce and control the alignment of a chiral nematic liquid crystal in a sensitive manner,8–10 or 3) make a chiral complex11 that may work as a chiral catalyst 12…”

A Unified Strategy for Exceptionally High Diastereoselectivity in the Photochemical Ring Closure of Chiral Diarylethenes

“…This photoinduced change is not limited to the color or absorption spectra, as the change occurs between two different molecules with different physical and chemical properties. When a photochromic compound is chiral and non-racemic, [2] its chiroptical properties such as circular dichroism spectra [3,4] and optical rotation [5][6][7] also change reversibly. These chiral and chiroptical differences can be used to: 1) detect the state of the system without inducing any property change, [5][6][7] 2) induce and control the alignment of a chiral nematic liquid crystal in a sensitive manner, [8][9][10] or 3) make a chiral complex [11] that may work as a chiral catalyst.…”

Enantioselective Photochromism of Diarylethenes in Human Serum Albumin

“…For 2 O, the spectrum showed a negative Cotton effect in the visible region, indicating that the major enantiomer of 2 C has an S,S configuration, as already mentioned. [9] On the other hand, 1 O showed a slight positive Cotton effect in the visible region. Matsuda et al have reported that the sign of rotatory strength for an R,R enantiomer of the C-form available by the photoirradiation of 1,2-bis(5-substituted-2-me-A C H T U N G T R E N N U N G thylthienyl)hexafluorocyclopentenes is positive when the pconjugating substituent is no larger than a vinyl group, whereas it is negative when the conjugating group is larger than a vinyl group, such as in the case of phenyl or formyl groups.…”

“…Fortunately, we had previously determined the absolute stereochemistry of optically resolved enantiomers of 2 C by X-ray crystallographic analysis [9] so that the slower moving major enantiomer of 2 C was identified as the S,S configuration. They exhibited photocyclization in the presence of HSA with 313 nm light.…”

“…For all of the diarylethenes employed, we detected two enantiomers of the C-form by use of an HPLC machine equipped with a chiral column. Fortunately, we had previously determined the absolute stereochemistry of optically resolved enantiomers of 2 C by X-ray crystallographic analysis [9] so that the slower moving major enantiomer of 2 C was identified as the S,S configuration. Absorption spectral changes starting from 2 O in the presence of an equimolar amount of HSA are shown in Figure 1.…”