Mass-Analyzed Threshold Ionization Spectroscopy of 2-Phenylethanol: Probing of Conformational Changes Caused by Ionization

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Molecules, spectroscopy, kinetics, environment, & general theory, 2009-11, Vol.113 (44), p.12328-12336
• Main Authors: Georgiev, S, Karaminkov, R, Chervenkov, S, Delchev, V, Neusser, H. J
• Format: Article
• Language: English
• Subjects: A: Molecular Structure, Quantum Chemistry, General Theory; Cations - chemistry; Hydrogen Bonding; Molecular Conformation; Phenylethyl Alcohol - chemistry; Quantum Theory; Spectrometry, Mass, Electrospray Ionization
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/jp908045k

The vibrational structure of the ionic ground state of different conformers of the biologically relevant molecule 2-phenylethanol has been investigated by combination of two-photon two-color mass-analyzed threshold ionization spectroscopy (MATI) and quantum chemical calculations at M05, MP2, and coupled cluster (CC) levels of theory with extended basis sets. MATI spectra recorded via gauche vibronic bands are with poor structure and increasing background, whereas the ones measured via vibronic bands of the anti conformers feature well-resolved vibronic structure in the cation. Ab initio computations predict three stable conformers for the 2-phenylethanol cation out of five initial neutral structures. None of the theoretical structures in the cation features a nonclassical OH···π hydrogen bond in conjunction with the analysis of the MATI spectra. This provides clear evidence that the OH···π hydrogen bond stabilizing the lowest-energy gauche conformer in the neutral breaks upon ionization.