Photochemistry of arylacetylenyl-substituted stilbenes

Suppression of Undesirable Isomerization and Intermolecular Reactions of Double Bonds by a Linked Rotaxane Structure

“…As a result, the irradiation of unins‐PivNH‐ST caused the appearance of the signals corresponding to its Z ‐form in the 1 H NMR spectra (Figure A). The ratio of the Z ‐form was ∼7% in the photostationary state, which was almost the same as that previously reported for an arylacetylenyl‐substituted stilbene . As in the case of unins‐NH 2 ‐AB and ins‐NH 2 ‐AB , any signals arising from the Z ‐form of ins‐PivNH‐ST were not detected in the 1 H NMR spectra (Figure B).…”

“…The ratio of the Z-form was~7% in the photostationary state, which was almost the same as that previously reported for an arylacetylenyl-substituted stilbene. [20] As in the case of unins-NH 2 -AB and ins-NH 2 -AB, any signals arising from the Z-form of ins-PivNH-ST were not detected in the 1 H NMR spectra ( Figure 5B). This indicates that the neighbor linked rotaxane structure prevents the photoisomerization of not only the N=N double bonds, but also the C=C bonds.…”

“…It has been previously reported that the PLQYs of (Z)-stilbene derivatives containing phenylacetylene moieties were lower than those of the corresponding (E)-stilbene derivatives. [20] Therefore, the E/Z isomerization of unins-PivNH-ST and ins-PivNH-ST should affect their PLQYs. With this in mind, we measured the PLQY changes observed for unins-PivNH-ST and ins-PivNH-ST under light irradiation under an inert atmosphere.…”

“…On the other hands, intramolecular reactions including the E/Z isomerization of double bonds also cause a reduction in the luminescence properties. [19,20] Chemical bonds, [21][22][23] steric effects, [24] and aggregation [25,26] have been typically used to suppress E/Z isomerization.…”

“…The insulation of double bonds using rotaxane structures or host–guest complexes can improve tolerance of the dyes by prohibiting these intermolecular reactions. On the other hands, intramolecular reactions including the E/Z isomerization of double bonds also cause a reduction in the luminescence properties . Chemical bonds, steric effects, and aggregation have been typically used to suppress E/Z isomerization.…”