Untersuchung der photophysikalischen Eigenschaften einzelner Farbstoffmoleküle sowie einzelner multichromophorer Systeme

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Beschreibung

In this thesis, the photophysical properties of several perylene bisimide derivatives (PBI-derivatives) and various multichromophoric systems such as supramolecular perylene bisimide squares (PBI squares) and amphiphilic pseudoisocyanine (amphi -PIC) J-aggregates were studied. Perylene bisimides feature a high fluorescence quantum yield near 100% and an extraordinary photophysical and photochemical stability. From a chemist’s point of view the PBI fluorophores have attracted considerable interest for several reasons. The basic chromophore can be modified by introducing different substituents in the bay positions or it can be functionalized at the imide groups with pyridine receptor units. Therefore, the phenoxy substituted PBI represents the basic chromophore of diagonally or laterally bridged macrocyclic perylene bisimides and of the ditopic ligand in self assembled multichromophoric systems. In the presence of cis-Ptk metal centers pyridine substituted PBI-derivatives form nanosized molecular squares. These supramolecules exhibit a simple geometry with four bridging PBI ligands at the edge and four cis-Ptk complexes at each corner of the molecular square. As a model system PBI squares allow the fundamental interactions of cyclic multichromophoric assemblies to be investigated. Owing to the cyclic arrangement of several dye molecules with a very high absorption cross section these PBI squares are a promising candidate for artifical light-harvesting complexes. Another prominent example of multichromophoric systems are J-aggregates consisting of hundreds of non covalently bound monomeric units in various geometries. The electronically excited states are dominated by interesting collective effects leading to a strong red shift of the absorption band and to a drastic increase of the oscillator strength with respect to the monomeric compounds. In this regard both the electronically excited states and the structural arrangement of individual amphi -PIC J-aggregates were investigated at cryogenic temperatures.