Investigation of solvation effects on short-time photodissociation dynamics of alkyl iodides

Abstract

Resonance and preresonance Raman spectra and A-band absorption spectra of ethyl, isopropyl, and tert-butyl iodides in the gas phase are compared with the corresponding spectra in cyclohexane solution. The C-I stretching Raman bands shift to lower frequencies upon solvation, indicating the dominance of attractive solvent-solute interactions in the ground electronic state. With a few exceptions, the relative intensities of the resonance Raman bands are similar in gas and solution phases, suggesting that solvation has only a minor effect on the early time photodissociation dynamics and excited-state potential energy surfaces in the Franck-Condon region. Solvation does, however, seem to alter the C-I stretching overtone to fundamental intensity ratios, probably as a result of shifts in electronic transition frequencies and/or oscillator strengths upon solvation. The implications for carrying over gas-phase reaction dynamical information into the study of chemical reactions in the solution phase are discussed. © 1992 American Chemical Society.