AG Zinth - Projects

LMU München
Fakultät für Physik




(c) 2002 BMO

Ultrafast Intersystem Crossing in Aromatic Carbonyl Compounds
(Femtochemistry - Femtobiology)

Photo-excited aromatic carbonyls like bezophenone and xanthone and their derivatives are well known to undergo ultrafast intersystemcrossing (ISC) to long-lived triplet states. That makes them ideal candidates to investigate the detailed mechanism of the ISC process which is of fundamental interest for many photochemical reactions. Furthermore, xanthone derivatives recieve growing interest as fluorescent chemosensors (Angew. Chem. 2006, 118, 5644) and as part of photo-labile protecting groups which are used in DNA-chip chemistry (Angew. Chem. 2006, 118, 3042). All of these applications depend on the photophysical properties of xanthone and its derivatives. For future development and implication of these compounds a thorough knowledge of the involved excited states and dynamics is imminent.
To pursue this task we use ultrafast transient absorption and fluorescence spectroscopy. We could prove the ultrafast nature of the ISC process in xanthone by performing a triplet quenching experiment on the femtosecond timescale. A subsequent study has been adressed to the unusually strong solvent dependence of the fluorescence of xanthone. Here, we further elucidate details excited states involved in the ISC process in xanthone and propose a delayed fluoresence mechanism to explain our observations.
In a cooperation with the group of Prof. Steiner at the University of Konstanz we currently investigate thioxanthone derivatives which are used as photo-labile protecting groups in oligonucleotid synthesis. The xanthone moiety in these compounds serves as an antennta to collect the photon energy which is then transferred intramolecularly.

Previous coworkers:  Stefan Berner
Peter Gilch
Bjoern Heinz
Stefan Laimgruber

Publications:  "On the Mechanism of Intramolecular Sensitization of Photocleavage of the 2-(2-Nitrophenyl)propoxycarbonyl (NPPOC) Protecting Group"
Dominik Wöll, Stefan Laimgruber, Marina Galetskaya, Julia Smirnova, Wolfgang Pfleiderer, Björn Heinz, Peter Gilch, Ulrich E. Steiner
J. Am. Chem. Soc. 129 (2007) 12148

"Slow Fluorescence and Fast Intersystem Crossing - The Xanthone Anomaly"
B. Heinz, B. Schmidt, C. Root, F. Milota, B. Fierz, T. Kiefhaber, W. Zinth, P. Gilch
Ultrafast Phenomena XV, Springer Series in Chem. Physics, Eds. Andrew M. Weiner and R. J. Dwayne Miller, Springer-Verlag, Berlin (2006)

"On the unusual fluorescence properties of xanthone in water "
B. Heinz, B. Schmidt, C. Root, H. Satzger, F. Milota, B. Fierz, T. Kiefhaber, W. Zinth and P. Gilch
Phys. Chem. Chem. Phys. 8 (2006) 3432-3439

"Ultrafast quenching of the xanthone triplet by energy transfer: New insight into the intersystem crossing kinetics"
H. Satzger, B. Schmidt, C. Root, W. Zinth, B. Fierz, F. Krieger,
J. Phys. Chem. A. 108 (2004) 10072-10079

mailto: webmaster
Letzte Änderung: 2016-08-31 08:07