Stuttgart 2012 – scientific programme

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MO: Fachverband Molekülphysik

MO 11: Biomolecules

MO 11.7: Talk

Tuesday, March 13, 2012, 15:30–15:45, V38.02

Rotationally resolved electronic spectroscopy of a flexible biomolecule: melatonine — •Michael Schmitt¹, Christian Brand¹, W. Leo Meerts², and David W. Pratt³ — ¹Heinrich-Heine-Universität Düsseldorf — ²Radboud University Nijmegen — ³University of Pittsburgh

Rotationally resolved electronic spectra of two origin bands of melatonin have been analyzed using an evolutionary strategy approach. From a comparison of the ab initio calculated structures of energy selected conformers to the experimental rotational constants, one band could be shown to be due to a gauche structure of the side chain, while the other band is due to an anti structure. Both bands show a splitting from the three-fold internal rotation of the methyl rotor in the N-acetyl group of the molecules. From a torsional analysis we additionally were able to determine the barriers of the methyl torsion in both electronic states. The electronic nature of the lowest excited singlet state could be determined to be L_b (as in the chromophore indole) from comparison to the results of ab initio calculations.