Proton/Hydrogen‐Transfer Coordinate of 2,5‐Dihydroxybenzoic Acid Investigated in a Supersonic Beam: Combined IR/UV Spectroscopy in the S0, S1, and D0 States |
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Authors: | Holger Fricke Dr Kristina Bartl Andreas Funk Andreas Gerlach Dr Markus Gerhards Prof Dr |
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Institution: | 1. Fachbereich Chemie, TU Kaiserslautern and research center OPTIMAS, Erwin‐Schr?dinger‐Str. 52, 7663 Kaiserslautern (Germany);2. Institut für Physikalische Chemie I, Heinrich‐Heine Universit?t Düsseldorf, Universit?tsstra?e 26.33.O2, 40225 Düsseldorf (Germany), Fax: (+49)?631‐205‐2750 |
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Abstract: | As a model system for intramolecular proton/hydrogen‐transfer coordinates, the structure of 2,5‐dihydroxybenzoic acid is investigated for the ground, first electronically excited and also the ionic state. Combined IR/UV spectroscopy in molecular‐beam experiments is applied and the experimental results are interpreted by the application of DFT and CASPT2 methods. No proton or hydrogen transfer is observed, but evidence is given for a hydrogen dislocation of the intramolecular hydrogen bond in the S1 state and to lesser extent in the D0 state. To obtain direct information on the proton/hydrogen‐transfer coordinate, IR spectra are recorded both in the region of the OH and especially the CO stretching vibrations by also applying two new variants of combined IR/UV spectroscopy for the S1 and D0 states. The CO groups are directly involved in the hydrogen bond and, in contrast to the hydrogen‐bonded OH groups, the CO stretching frequencies can be observed in all electronic states. |
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Keywords: | hydrogen bonds IR spectroscopy molecular beam spectroscopic methods UV/Vis spectroscopy |
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