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

• DOI: 10.1126/science.1116213
• Publication Date: 2005-08-05T00:44:05Z
• Authors: Junrong Zheng; Kyungwon Kwak; John Asbury; Xin Chen; Ivan R. Piletic; M. D. Fayer
• Keywords: Bromobenzene; Picosecond

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