Relaxation pathways and fs dynamics in a photoswitchable intramolecular D→A energy transfer system

A photoswitchable energy transfer system (donor–switch–acceptor) is examined in a polymer environment using time-resolved pump and probe spectroscopy. The system consists of a photochromic fulgide derivative acting as switching unit, an anthracene group as energy donor and a coumarin moiety as acceptor. The general value of the concept has already been proven by different spectroscopic methods. To get a deeper insight into the complex energy relaxation process, both the supermolecule and all its subunits are studied separately. The role of the switch is analysed by comparing spectra and transients of both isomeric forms.