15min:
INFRARED SPECTROSCOPY OF M+(CH4)n(H2O)3-4 CLUSTERS (M=Li, Na): INDUCING H2O cdotsH2O AND H2O cdotsCH4 HYDROGEN BONDS IN METHANATED CLUSTERS.

OSCAR RODRIGUEZ JR. AND JAMES M. LISY, Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801.

Experiments on M+(CH4)n(H2O)3-4 (M=Li and Na) have been carried out using tandem mass spectrometry and infrared spectroscopy in the O-H stretching region from 3400 cm-1 to 3800 cm-1. We have found, for example, that a single CH4 can induce hydrogen bonded conformers in the cases of Li+(CH4)1(H2O)3Ar0-1, which are absent in the Li+(H2O)3Ar0-1 spectra,. Furthermore, upon addition of multiple CH4 ligands, hydrogen bonding is not only maintained, but features associated with H2O cdotsCH4 hydrogen bonds are more intense, indicating the affinity of CH4 to bind to available O-H sites. Spectra of Li+(CH4)1-3(H2O)4 and Na+(CH4)1-3(H2O)3-4 clusters will also be discussed, all of which exhibit the curious trait of H2O cdotsH2O and H2O cdotsCH4 hydrogen bonding in the presence of hydrophobic, non-polar CH4. To better understand the nature and onset of H2O cdotsCH4 hydrogen bonding, the Li+(CH4)n(H2O)1-2 spectra will be discussed.