hydrogen bonding in methanated li + (h 2 o) 2-4 clusters oscar rodriguez jr. and james m. lisy...
TRANSCRIPT
Hydrogen Bonding in Methanated Li+(H2O)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+···(H2O)2-5 completed
Miller, D.J. et al. JACS 130 46 (2008) 15381.
Miller, D.J. et al. JACS 130 46 (2008) 15393.
• … now add CH4
United States Geological Survey
Outline
• Li+(H2O)2(CH4)n
• Li+(H2O)3(CH4)n
• Li+(H2O)4(CH4)n
• Li+ vs Na+ Summary
• Gaussian 03 Calculations:– B3LYP/6-31+G*
Calculated spectra and structures
0
1
2
3
4
5
6
3300 3350 3400 3450 3500 3550 3600 3650 3700 3750 3800
Frequency, (cm-1)
Inte
nsi
ty
Experimental Apparatus
Nd3+ YAG (1064 nm)
10 Hz, 10 ns pulse Tunable LaserVision OPO/OPA
Argon
Methane
Water
Li+(H2O)2(CH4)n, n=1-3
n=1
n=2
n=3
0
2
4
6
8
3450 3550 3650 3750 3850
Frequency, (cm-1)
IRP
D C
ross
Sec
tio
ns,
(x
10-1
9 cm
2 )
Li+(H2O)2(CH4)3
0
1
2
3
4
5
6
7
8
3400 3500 3600 3700 3800 3900
Frequency, (cm-1)
IRP
D C
ross
Sec
tio
n (
x 10
-19 c
m2 )
Li+(H2O)3Ar
Li+(H2O)3(CH4)1
+19 kJ/mol
0
2
4
6
8
10
12
14
3200 3300 3400 3500 3600 3700 3800 3900
Frequency, (cm-1)
IRP
D C
ross
Sec
tio
ns,
(x
10-1
9 cm
2 )
aMiller, D.J. et al. JACS 130 46 (2008) 15381.
a
Li+(H2O)3(CH4)1
Bent H2O-H2O Hydrogen Bond
H2O-CH4 Hydrogen Bond
H2O Symmetric Stretch
Free OH Stretch
0
2
4
6
8
10
12
14
16
18
20
22
3100 3300 3500 3700
Frequency, (cm-1)
IRP
D C
ross
Sec
tio
ns,
(x
10-1
9 cm
2 )
Li+(H2O)4(CH4)n
n=1
n=2
Li+(H2O)4(CH4)2
0
4
8
12
16
20
3100 3200 3300 3400 3500 3600 3700 3800
Frequency, (cm-1)
IRP
D C
ross
Sec
tio
n (
x 10
-19 c
m2 )
+29 kJ/mol
AAD or 3°
0 kJ/mol +7 kJ/mol
Na+(H2O)3(CH4)1
Na+(H2O)3(CH4)2
0
2
4
6
8
10
12
14
16
18
3200 3300 3400 3500 3600 3700 3800 3900
Frequency, (cm-1)
IRP
D C
ross
Sec
tio
ns,
(x
10-1
9 cm
2 )
Li+(H2O)3(CH4)1
Na+(H2O)4(CH4)1
Na+(H2O)4(CH4)2
0
4
8
12
16
20
24
28
32
3100 3200 3300 3400 3500 3600 3700 3800
Frequency, (cm-1)
IRP
D C
ross
Sec
tio
ns,
(x
10-1
9 cm
2 )
Li+(H2O)4(CH4)2
Conclusions
• O-H∙ ∙ ∙CH4 hydrogen bonding in Li+ (H2O)2(CH4)3
• High energy (+19 kJ/mol)
H2O∙ ∙ ∙H2O hydrogen bonded conformer in Li+(H2O)3(CH4)1
• Various forms of H2O∙ ∙ ∙H2O hydrogen bonding in the methanated Li+(H2O)4 case
• H2O∙ ∙ ∙H2O hydrogen bonding observed to a lesser extend in the methanated Na+(H2O)4 case
Acknowledgements
Dr. James M. Lisy
Jordan Beck (RI13 IRPD Spectra of Cl-(CH3OH)nAr Cluster Ions)
Lorena Rodriguez
Nicolas Rodriguez
Funding:
National Science Foundation