Fig. 3. Switching behavior of tweezers 4. (a) Schematic representation of the switching process of 4. Z to E photoisomerization can be triggered by 405 nm light. E to Z photoisomerization can by induced by 470 nm light. The energy barrier associated with thermal E to Z isomerization is greater than 33 kcal mol⁻¹ providing a highly bistable photoswitch. (b) Aromatic section of ¹H-NMR spectra (400 MHz, 20 °C, left: CD₂Cl₂, right: CDCl₃) of 4 recorded after irradiation with light of 365 nm, 405 nm, and 470 nm wavelengths until reaching the PSS. Indicative proton signals used to quantify the isomeric ratio in the respective PSS are highlighted. (c) Molar absorption coefficients of the pure isomers (black: Z isomer, red: E isomer) of 4 in CHCl₃.