Physikalische und Theoretische Chemie, Technische Universität München, Lichtenbergstrasse 4, 85748 Garching, Germany.
J Phys Chem A. 2009 Nov 5;113(44):12328-36. 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...pi hydrogen bond in conjunction with the analysis of the MATI spectra. This provides clear evidence that the OH...pi hydrogen bond stabilizing the lowest-energy gauche conformer in the neutral breaks upon ionization.
不同构象的生物相关分子 2-苯乙醇的离子基态的振动结构已通过双光子双色质量分析阈电离光谱（MATI）与量子化学计算相结合进行了研究，理论计算在 M05、MP2 和耦合簇（CC）水平上进行，并采用了扩展基组。通过 gauche 振子带记录的 MATI 光谱结构较差且背景增加，而通过反构象的振子带测量的光谱则在阳离子中具有良好分辨的振子结构。从头算计算预测了 2-苯乙醇阳离子中的三种稳定构象，而不是最初的中性结构中的五种。阳离子中的理论结构均没有分析 MATI 光谱时所预测的非经典 OH...pi 氢键。这清楚地表明，在中性状态下稳定最低能量 gauche 构象的 OH...pi 氢键在电离时会断裂。
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