|Philipp Behrendt and Norbert Hampp
Physikalische Chemie, Fachbereich Chemie, Philipps-Universität, Hans-Meerwein-Straße, 35043 Marburg, Germany
To be able to control any kind of reaction photo-chemically is desirable and reversibility is even more favorable. Coumarin, with its well known photochemistry, allows for selective dimer formation or dimer cleavage by irradiation with two different wavelengths. Hence it has been used in photoactive compounds for over a century and variations of the substituents make it possible to change its absorption wavelength and to enhance its reactivity. In order to be able to investigate or to compare coumarin based molecules, a laser is used as photo-energy source. High yields within a short reaction time are the outcome. A further differentiation of the photo-controllable linker system can then be achieved via intermolecular crossdimerization of coumarin to a completely diverse substrate. Therefore a target molecule does not have to be connected to a part of the linking system, but can instead be connected straightaway to the photoactive molecule. Fewer synthetic steps, as well as an ideal linker to target molecule ratio are created.