Exploring the structure of a photosynthetic model by quantum-chemical calculations and time-resolved Q-band electron paramagnetic resonance

Andreas M. Kiefer, Stefan M. Kast, Michael R Wasielewski, Karl Laukenmann, Gerd Kothe

Research output: Contribution to journalArticle

22 Citations (Scopus)

Abstract

The structure of the covalent photosynthetic model system N,N,N',N'- tetraalkyl-p-phenylenediamine-zinc porphyrin-naphthoquinone (TAPD-ZnP-NQ) has been explored by using a combination of theoretical and experimental techniques. Structural information is extracted from high-level quantum- chemical ab initio calculations, which is a nontrivial task for a large molecule like TAPD-ZnP-NQ. We tackle this problem by dividing the model system into smaller molecular fragments, whose geometries can be optimized separately. The fragments are subsequently fitted together, thus providing an approximate structure of the entire model system. To verify this structure, time-resolved Q-band electron paramagnetic resonance (EPR) experiments on the light-induced radical pair TAPD+ NQ- have been carded out. The time evolution of the transverse magnetization of TAPD+ NQ- is monitored at various static magnetic fields. Quantum beat oscillations are observed at early times after the laser pulse. These quantum beats are highly sensitive probes for the geometry of the underlying radical pair. From the good agreement between observed and simulated EPR time profiles we conclude that the ab initio calculations predict the correct geometry within the experimental precision.

Original languageEnglish
Pages (from-to)188-198
Number of pages11
JournalJournal of the American Chemical Society
Volume121
Issue number1
DOIs
Publication statusPublished - Jan 13 1999

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Chemical Models
Electron Spin Resonance Spectroscopy
Paramagnetic resonance
Naphthoquinones
Porphyrins
Geometry
Zinc
Psychological Techniques
Laser pulses
Magnetization
Magnetic Fields
Magnetic fields
Molecules
Lasers
Light
Experiments
4-phenylenediamine
zinc hematoporphyrin

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

Exploring the structure of a photosynthetic model by quantum-chemical calculations and time-resolved Q-band electron paramagnetic resonance. / Kiefer, Andreas M.; Kast, Stefan M.; Wasielewski, Michael R; Laukenmann, Karl; Kothe, Gerd.

In: Journal of the American Chemical Society, Vol. 121, No. 1, 13.01.1999, p. 188-198.

Research output: Contribution to journalArticle

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