Hydrogen Bonding in Methanated Li + (H 2 O) 2-4 Clusters Oscar Rodriguez Jr. and James M. Lisy University of Illinois at Urbana-Champaign

Why Study Methane-Water Clusters? Hydrophilic-Hydrophobic interactions Gas hydrates (Clathrates): Gases trapped in water clusters, or cages. This occurs in oceans or permafrost M + ···(H 2 O) 2-5 completed Miller, D.J. et al. JACS (2008) Miller, D.J. et al. JACS (2008) … now add CH 4 United States Geological Survey

Outline Li + (H 2 O) 2 (CH 4 ) n Li + (H 2 O) 3 (CH 4 ) n Li + (H 2 O) 4 (CH 4 ) n Li + vs Na + Summary Gaussian 03 Calculations: –B3LYP/6-31+G* Calculated spectra and structures

Experimental Apparatus Nd 3+ YAG (1064 nm) 10 Hz, 10 ns pulse Tunable LaserVision OPO/OPA Argon Methane Water

Li + (H 2 O) 2 (CH 4 ) n, n=1-3 n=1 n=2 n=3

Li + (H 2 O) 2 (CH 4 ) 3

Li + (H 2 O) 3 Ar Li + (H 2 O) 3 (CH 4 ) kJ/mol a Miller, D.J. et al. JACS (2008) a

Li + (H 2 O) 3 (CH 4 ) 1 Bent H 2 O-H 2 O Hydrogen Bond H 2 O-CH 4 Hydrogen Bond H 2 O Symmetric Stretch Free OH Stretch Li + (H 2 O) 4 (CH 4 ) n n=1 n=2

Li + (H 2 O) 4 (CH 4 ) kJ/mol AAD or 3° 0 kJ/mol+7 kJ/mol

Na + (H 2 O) 3 (CH 4 ) 1 Na + (H 2 O) 3 (CH 4 ) 2 Li + (H 2 O) 3 (CH 4 ) 1

Na + (H 2 O) 4 (CH 4 ) 1 Na + (H 2 O) 4 (CH 4 ) 2 Li + (H 2 O) 4 (CH 4 ) 2

Conclusions O-H∙ ∙ ∙CH 4 hydrogen bonding in Li + (H 2 O) 2 (CH 4 ) 3 High energy (+19 kJ/mol) H 2 O∙ ∙ ∙H 2 O hydrogen bonded conformer in Li + (H 2 O) 3 (CH 4 ) 1 Various forms of H 2 O∙ ∙ ∙H 2 O hydrogen bonding in the methanated Li + (H 2 O) 4 case H 2 O∙ ∙ ∙H 2 O hydrogen bonding observed to a lesser extend in the methanated Na + (H 2 O) 4 case

Acknowledgements Dr. James M. Lisy Jordan Beck (RI13 IRPD Spectra of Cl - (CH 3 OH) n Ar Cluster Ions) Lorena Rodriguez Nicolas Rodriguez Funding: National Science Foundation