Ultrafast Photoisomerization Dynamics of Photochromic Molecular Switches Affected by Their Environment and Ultrafast Energy Transfer

The main goal of this Thesis is the investigation of the excited-state dynamics of photochromic molecular switches following photoexcitation in different molecular environments by static and femtosecond time-resolved transient absorption spectroscopy in combination with quantum-chemical calculations. The time-resolved transient absorption spectroscopy on thin polymethylmethacrylate (PMMA) films doped with azobenzene (AB) derivatives called for an improved experimental setup and data collection strategy combined with a background subtraction scheme. The vibrational cooling in the electronic ground state of the ABs is slowed down moderately by a factor of 2 in the polymer film. We observed formation of the isomerisation photoproduct of the dianionic cis-ferulic acid. The ultrafast electronic energy transfer (EET) of a donor–acceptor dyad with a time constant of 3 ps was investigated