High resolution electronic spectra of anisole and anisole-water in the gas phase: Hydrogen bond switching in the S 1 state

Abstract

Rotationally resolved S 1←S 0 electronic spectra of anisole and its hydrogen bonded complex containing one water molecule have been obtained. The results provide evidence for an "in-plane" complex in which the water molecule is attached via two hydrogen bonds to the anisole molecule, a donor O - H - O(CH 3) bond and an acceptor H - O - H(ring) bond. Analysis of the subbands that appear in the spectrum of the complex suggests that hydrogen bond "switching" occurs when the complex absorbs light. The former O - H - O(CH 3) bond is stronger in the ground (S 0) state, whereas the latter H - O - H(ring) bond is stronger in the excited (S 1) state. Dynamical consequences of this phenomenon are discussed. © 2006 American Chemical Society.