Z/E, photoisomerization of 5‐arylmethylenehydantoins and 5‐pyridylmethylenehydantoins

Abstract

The Z/E photoisomerization of a series of 5‐arylmethylenehydantoins and a series of 5‐pyridylmethylenehydantoins by direct irradiation in methanol or ethanol solvent was investigated. The isomeric ratios at the photostationary state are dependent on the excitation wavelength and are related to the relative absorption coefficients of the two isomers. Measurements of quantum yields show the absence of quenching effects by oxygen or azulene, suggesting that triplet states either are not involved or are too short‐lived for quenching to be observed. Preparative photoisomerization provides a route to the isomer which is not isolated or obtained only as a minor product by the usual method of synthesis.

Topochemistry and Photomechanical Effects in Crystals of Green Fluorescent Protein-like Chromophores: Effects of Hydrogen Bonding and Crystal Packing

“…From the X-ray diffraction analysis of partially photoreacted crystal, it is concluded that, while dimers of the BDIs are obtained by high-energy excitation (365 nm; see the NMR, IR and MS results described above), in single crystals of 3-HOBDI -C, prolonged exposure to low excitation energies in the visible region (ambient light) cause Z−E isomerization with a τ one-bond flip of the imidazolone ring. Similar dependence on the dimerization versus isomerization on the excitation energy was reported previously for solutions of 5-aryl- and 5-pyridylmethylenehydantoins . Our result represents the first direct evidence of such processes occurring in crystals of pure BDI chromophore.…”

“…Similar dependence on the dimerization versus isomerization on the excitation energy was reported previously for solutions of 5-aryl-and 5-pyridylmethylenehydantoins. 39 Our result represents the first direct evidence of such processes occurring in crystals of pure BDI chromophore. On the basis of this observation, we conclude that conservation of volume is not a sufficient impediment to isomerization via a bond twist.…”

GFP-related chromophores: photoisomerization, thermal reversion, and DNA labelling

“…17 This process was very slow and despite our attempts to advance isomerization with acetic acid, either in DMSO- d 6 or CD 3 CN, no net effect was observed. Moreover, the samples after reaching the PSS were irradiated at 590 nm to induce the photo-reversion reaction as it was previously reported by Tan et al on 5-arylmethylenehydantoin 23 ; but after 50 min of irradiation, no changes in the concentration of either isomers were detected.…”

Hydantoin-Based Molecular Photoswitches

“…In this respect, it has been demonstrated that 5-AHTs function as excellent UV absorbents in the cosmetics industry. On the basis of the structural similarity of 5-AHTs with the GFP-like molecular photoswitches previously reported, the capability of Z / E photoisomerization, − and their superb thermal and photochemical stability, we decided to explore their behavior as molecular photoswitches. Accordingly, we have carried out detailed investigations and herein report the synthesis, photochemistry, and theoretical study of a library of molecular photoswitches based on the 5-arylidenehydantoin structure.…”