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MO: Fachverband Molekülphysik
MO 18: Biomolecules and Electron Transfer
MO 18.1: Talk
Friday, March 10, 2017, 11:00–11:15, N 25
Ultrafast dynamics of the triazene compound Berenil — •Lena Grimmelsmann, Johannes Knorr, Christian Spies, and Patrick Nuernberger — Physikalische Chemie II, Ruhr-Universität Bochum, 44780 Bochum
Berenil is a versatile organic compound with a variety of applications, e.g. as the most widely used drug for treating the sleeping sickness in animals. Berenil efficiently binds to DNA, trypsin, and other biomolecules, but in all these cases it is reported to be a “non-fluorescent dye”. This points towards a very short excited-state lifetime and ultrafast nonradiative deactivation channels on which the molecule’s surrounding have a significant impact. Berenil comprises two amidinophenyl moieties linked by a triazene bridge, therefore it is chemically related to azobenzene but exhibits remarkable differences.
In femtosecond fluorescence upconversion and transient absorption experiments, we disclose the ultrafast dynamics of berenil in various solvents, as well as berenil bound to trypsin, AT-rich DNA, and G-quadruplex DNA. Our results demonstrate that berenil exhibits an ultrafast deactivation of the S1 state after photoexcitation, which we ascribe to associated molecular motion which does not require volume significantly beyond that occupied by the ground-state molecule. Studies in solvents with different viscosities substantiate these findings. As a general trend, one finds that the more restriction the binding introduces, the longer the fluorescence lifetimes. The transient absorption experiments provide additional insight into the nonradiative reaction channels and the possibility of photoisomerization.