Trap formation and energy transfer in pheophorbide a-DAB-dendrimers and pyropheophorbide a-fullerene C60 hexaadduct molecular systems

Beate Röder; Eugeny A. Ermilov; Steffen Hackbarth; Matthias Helmreich; Norbert Jux

doi:10.1117/12.661908

20 April 2006 Trap formation and energy transfer in pheophorbide a-DAB-dendrimers and pyropheophorbide a-fullerene C₆₀ hexaadduct molecular systems

Beate Röder, Eugeny A. Ermilov, Steffen Hackbarth, Matthias Helmreich, Norbert Jux

Author Affiliations +

Proceedings Volume 6192, Organic Optoelectronics and Photonics II; 61922O (2006) https://doi.org/10.1117/12.661908
Event: SPIE Photonics Europe, 2006, Strasbourg, France

Abstract

The photophysical properties of DAB-dendrimers from 1^st to 4^th generation as well as Diaminohexane - all substituted with the in maximum achievable quantity of pheophorbide a (Pheo) molecules were studied in comparison with a novel hexapyropheophorbide a - fullerene hexaadduct (FHP6) and a fullerene [6:0]-hexaadduct which carries twelve pyropheophorbide a units (FHP12) using both steady-state and time-resolved spectroscopic methods. It was found that neighboring dye molecules covalently linked to one DAB- or fullerene moiety due to the length and high flexibility of carbon chains could stack with each other. This structural property is the reason for the possibility of formation different types of energy traps, which were resolved experimentally. The dipole-dipole resonance F&diaero;rster energy transfer between the dye molecules coupled to one complex caused a very fast and efficient delivery of the excitation to a trap. As result the fluorescence as well as the singlet oxygen quantum yields of the different complexes were reduced with increasing number of dye molecules per complex. Nevertheless in every case the singlet oxygen generation was less influenced then the fluorescence quantum yield, exposing the complex to a non-negligible amount of excited oxygen in the singlet state. While the fullerene complexes turned out to be stable under these conditions, the DAB-dendrimer-backbones were completely fragmented to small rudiments carrying just one or a small number of dye molecules.

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Beate Röder, Eugeny A. Ermilov, Steffen Hackbarth, Matthias Helmreich, and Norbert Jux "Trap formation and energy transfer in pheophorbide a-DAB-dendrimers and pyropheophorbide a-fullerene C₆₀ hexaadduct molecular systems", Proc. SPIE 6192, Organic Optoelectronics and Photonics II, 61922O (20 April 2006); https://doi.org/10.1117/12.661908

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