Water-wire cluxters:vibronicspectra of 7-hydroxyquinoline.(H_2O)_3

摘要

The supersonically cooled 7-hydroxyquinoline.(H_2O)_3 cluster was investigated by mass~- and isomer-selected S_1<- S_o resonant two-photon ionization and S_1-> S_o fluorescence spectroscopy. UV(ultraviolet)/UV- holeburning measurements prove that a single cluster isomer is formed, although different tautomers(7-keto-and 7-hydroxyquinoline), rotamers(cis and trans) and isomers (cyclic and water-wrire) are possible. Ab initio calculations of structures and vibrations of different tautomers and isomers of this cluster presict that the cis-enol-7-hydroxyquinoline.(H_2O_)_3 "water-wire" cluster is the most stable species. The experimental S-o and S_1 inter-and intramolecular vibrational frequencies are in good agreement with the caluculated harmonic frequencies. S_1<-S_o excitation leads to contraction of all four hydrogen bonds along the hydrogen bonded water wire. inducing intense intermolecular streching vibrations of the O-H...O and HO-H...N(quinoline) hydrogen bonds which terminate the water-write. There are no spectroscopic sinns of proton transfer