Details

Autor(en) / Beteiligte

• Zheng, Junrong
• Kwak, Kyungwon
• Asbury, John
• Chen, Xin
• Piletic, Ivan R
• Fayer, M. D

Titel

Ultrafast Dynamics of Solute-Solvent Complexation Observed at Thermal Equilibrium in Real Time

Ist Teil von

• Science (American Association for the Advancement of Science), 2005-08, Vol.309 (5739), p.1338-1343

Ort / Verlag

Washington, DC: American Association for the Advancement of Science

Erscheinungsjahr

2005

Quelle

Science Online_科学在线

Beschreibungen/Notizen

• In general, the formation and dissociation of solute-solvent complexes have been too rapid to measure without disturbing the thermal equilibrium. We were able to do so with the use of two-dimensional infrared vibrational echo spectroscopy, an ultrafast vibrational analog of two-dimensional nuclear magnetic resonance spectroscopy. The equilibrium dynamics of phenol complexation to benzene in a benzene-carbon tetrachloride solvent mixture were measured in real time by the appearance of off-diagonal peaks in the two-dimensional vibrational echo spectrum of the phenol hydroxyl stretch. The dissociation time constant [tau][subscript d] for the phenol-benzene complex was 8 picoseconds. Adding two electron-donating methyl groups to the benzene nearly tripled the value of [tau][subscript d] and stabilized the complex, whereas bromobenzene, with an electron-withdrawing bromo group, formed a slightly weaker complex with a slightly lower [tau][subscript d]. The spectroscopic method holds promise for studying a wide variety of other fast chemical exchange processes.