Isotopomeric Conformational Changes in the Anisole-Water Complex: New Insights from HR-UV Spectroscopy and Theoretical Studies

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• 作者：Massimiliano Pasquini ; Nicola Schiccheri ; Giovanni Piani ; Giangaetano Pietraperzia ; Maurizio Becucci ; Malgorzata Biczysko ; Michele Pavone ; Vincenzo Barone
• 刊名：Journal of Physical Chemistry A
• 出版年：2007
• 出版时间：December 13, 2007
• 年：2007
• 卷：111
• 期：49
• 页码：12363 - 12371
• 全文大小：209K
• 年卷期：v.111,no.49(December 13, 2007)
• ISSN：1520-5215

文摘

Resonance enhanced multiphoton ionization and rotationally resolved S₁ S₀ electronic spectra of the anisole-²H₂O complex have been obtained. The experimental results are compared with high level quantum mechanicalcalculations and with data already available in the literature. Quite surprisingly, the equilibrium structure ofthe anisole-²H₂O complex in the S₀ state shows some non-negligible differences from that of the isotopomeranisole-¹H₂O complex. Actually, the structure of the deuterated complex is more similar to the correspondingstructure of the anisole-¹H₂O complex in the S₁ state. In anisole-water, two equivalent H(D) atoms exist asrevealed by line splitting in the rotationally resolved spectra. It is possible to suggest a mechanism for theproton/deuteron exchange ruled by a bifurcated transition state for the exchange reaction, with both waterhydrogen atoms interacting with the anisole oxygen atom. From the analysis of all of the available experimentaldata and of computational results, we can demonstrate that in the S₁ excited state the hydrogen bond in whichthe water molecule acts as an acid is weaker than in the electronic ground state but is still the principalinteraction between water and the anisole molecules.