Berlin 2014 – scientific programme
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MO: Fachverband Molekülphysik
MO 21: Photochemistry
MO 21.6: Talk
Friday, March 21, 2014, 11:45–12:00, BEBEL HS213
Structural investigations on the jet-cooled neutral and ionic 7-hydroxy-4-methylcoumarin dimer and its hydrates by combined IR/UV spectroscopy — Anke Stamm, •Kirsten Schwing, and Markus Gerhards — Physikalische Chemie, TU Kaiserslautern, Erwin-Schrödinger-Straße 52, 67663 Kaiserslautern
The photochemistry of solvated 7-hydroxy-4-methylcoumarin (7H4MC), e.g. known as one of the first industrially applied optical brighteners, was intensively investigated in the past e.g. comprising absorption spectroscopy, fluorescence measurements leading to quantum yields and life times or phosphorescence and triplet-triplet spectra. In this context the influence of solvents on the photochemical behavior was one of the main interests. From aqueous solution it is additionally known that the coumarin dyes show a tendency for self-aggregation. However, no detailed experimental analysis of the intrinsic structural properties of 7H4MC was performed so far. Thus we applied mass-, (isomer-) and state-selective combined double and triple resonance IR/UV methods for 7-hydroxy-4-methylcoumarin. IR spectra of the neutral and ionic dimer (S0, D0 states) of 7H4MC as well as its mono- and dihydrate could be obtained. A comparison with calculated IR spectra for possible DFT-optimized isomers of a species allowed structural assignments. The presented measurements on 7H4MC are the first gas phase investigations on a neutral and ionic dimer of a coumarin derivative. The tendency of coumarin dyes for self-aggregation observed in aqueous solution is now investigated in detail on isolated species which can be successively hydrated.