(E)-1-(3,4-Dimethoxyphenyl)-2-methyl-3-phenylprop-2-en-1-one: A P-Type Acid-Stable Photochromic α-Methylchalcone

The α-methylated chalcone 3 with an electron-donor substituted A-aryl ring and unsubstituted B-phenyl was synthesized by base-catalyzed aldehyde/acetophenone condensation. Compound can be photo-switched from E→Z irradiation long-wavelength light λ > 350 nm, whereas shorter wavelengths leads to photo-stationary states (PSS) lower amounts of the Z-isomer. limiting wavelength for fully equilibrated E⮀Z (PSS = 1) achieved around 240 nm. stability both E- Z-isomers at wavelength-dependent PSS under UV-irradiation between 250 nm is remarkably high as observed UV NMR spectroscopy. fatigue resistant even after more than 10 days continuous also oxygenation-stable singlet oxygen sensitization conditions. In remarkable contrast many other chalcones, no change in E/Z-ratio detected when samples were treated Broensted acids. negative photochromic switch accompanied a conformational E-form its preferred s-trans conformation Z-form distorted s-cis (Es-c→Zs-t).