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.
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 S(1) state and to lesser extent in the D(0) 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 S(1) and D(0) 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.
Fricke
Holger
H
Fachbereich Chemie, TU Kaiserslautern and research center OPTIMAS, Erwin-Schrödinger-Str. 52, 7663 Kaiserslautern, Germany.
Bartl
Kristina
K
Funk
Andreas
A
Gerlach
Andreas
A
Gerhards
Markus
M
D005841:Gentisates / Q000737:chemistry*; D006859:Hydrogen; D011522:Protons; D013055:Spectrophotometry, Infrared; D013056:Spectrophotometry, Ultraviolet; D013057:Spectrum Analysis
D005841:Gentisates; D011522:Protons; D006859:Hydrogen