Work Group Prof. Dr. F. Temps

Furylfulgides

Fulgides and fulgimides are highly useful molecular switches for applications in, e.g., data storage devices and, in particular, super-resolution microscopy, where they allow us to control the fluorescence state (on or off) of an attached fluorophore by Förster Resonance Energy Transfer (FRET). Their pronounced photochromism rests on the pericyclic ring opening and ring closure reactions between the central 1,3,5-hexatriene (HT) and 1,3-cyclohexadiene (CHD) moieties (see Scheme below). The almost planar closed (C) form shows absorption already in the VIS spectral range, whereas the open (E) isomer is non-planar and typically absorbs only in the near UV. Upon irrradiation at appropriate wavelengths, their mutual interconversion is fully photoreversible in both directions. Furthermore, the molecules stand out for their thermal irreversibility in combination with high photostability. Applications are, however, disfavored by the existence of a third form, the (Z) isomer, which is produced by photoisomerization around the C=C double bond in the HT moiety and by relatively low quantum yields for the desired E - C isomerization. 

C-E-Z Reaction Cycle of Fulgides
 
Photo-induced conversion reactions between the (C), (E), and (Z) isomers of methyl furylfulgide.

 

In an extensive research thrust in collaboration with the Mattay group at the University of Bielefeld, we have studied the complete C - E - Z photoswitching cycles of a series of chemically modified furylfulgides with vastly improved photoswitching dynamics. The E-to-Z reaction could be virtually stopped, while the E-to-C photoisomerization time could be accelerated to ~ 50 fs. The successful synthetic efforts in the Mattay group were rationally guided by the results of our femtosecond spectroscopy experiments. Several interesting applications are awaiting further studies.

Important Papers:

  • F. Renth, R. Siewertsen, F. Temps, "Enhanced Photoswitching and Ultrafast Dynamics in Structurally Modified Photochromic Furylfulgides",  Int. Rev. Phys. Chem. 32, 1 - 38 (2013). DOI: 10.1080/0144235X.2012.729331
  • R. Siewertsen, F. Strübe, J. Mattay, F. Renth, F. Temps, "Tuning of Switching Properties and Excited-State Dynamics of Fulgides by Structural Modifications", Phys. Chem. Chem. Phys. 13, 3800 - 3808 (2011). DOI: 10.1039/C0CP01890B