Fluorescence/UV-Vis spectroscopy and lifetime determination in condensed phase

In our research group we are interested in spectroscopic investigations of photophysical relevant biomolecules.  ESPT processes (excited state proton transfer) of photoprotective substances like e.g. hydroxycoumarin and hydroxyflavone are investigated in gas and condensed phase. A further attention is in the analysis of photophysical processes of multinuclear metal complexes in solution. The interactions of several metal centers (especially transition metals) and potential cooperative effects are of interest.

For further characterization of the investigated substances UV/Vis and fluorescence spectroscopy in condensed phase are applied and influences of the solvent (solvatochromism) are analyzed. Photoluminescence research is performed with a Fluorolog 3-22 τ, a modular built fluorescence spectrometer.

Furthermore lifetimes of electronically excited states are determined by application of phase modulation fluorometry (Fluorolog 3-22 τ) as well as TCSPC (time correlated single photon counting, apparatus: DeltaFlex). TCSPC is a very suitable method to determine lifetimes of weak fluorophores (appearing e.g. in transition metal complexes). With the help of lifetimes it is possible to characterize electronically excited states.

Figure 1: Fluorescence spectra (dotted) of a Pd3-complex (black) in comparison with the emission of the ligand (orange) as well as the associated UV/Vis spectra (continuous lines) dissolved in DMSO. The lifetimes of the complex are 222 ns under air and 1.4 - 1.7 μs under argon atmosphere.