1. Microwave Spectroscopic Investigations of the Xe-H 2 O and Xe-(H 2 O) 2 van der Waals Complexes Qing Wen and Wolfgang Jäger Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada

2. 2 129 Xe NMR Imaging Applications Laser-polarized 129 Xe ( I = ½) significantly increases NMR signals. In vivo 129 Xe imaging applications. Goodson, J. Magn. Reson. 2002, 155, 157; Mugler et al. Magn. Reson. Med. 1997, 37, 809. 1 H & 129 Xe MRI of human lungs

3. 3 Motivation to Study the Xe-(H 2 O) N (N=1,2) Complexes A prototypical model of hydrophobic interactions. Help to interpret the background signal of in vivo images. A stepping stone to determine the effect of the successive solvation with water molecules.

4. 4 ab initio Calculation of Xe-H 2 O Program: Molpro 2002.6 Package CCSD(T) level of theory Basis sets: Xe: aug-cc-pVQZ-PP O, H: aug-cc-pVTZ Midbond functions (3s, 3p, 2d, 2f, 1g) H 2 O fixed at its equilibrium structure Supermolecule approach Counterpoise correction O H H Xe   R

5. 5 Equilibrium Geometry of Xe-H 2 O O H Xe H  Energy: -191.7 cm -1  Structure: R = 4.0 Å,   = 60 ,   = 0  In-Plane Rotation     is  fixed at 0     changes with rotation Out-of-Plane Rotation     is  fixed at 60     changes with rotation

6. 6 Minimum Energy Paths of H 2 O Internal Rotations )) In-plane rotation (   fixed at 0  ) Energy (cm -1 ) )) O H Xe H Out-of-plane rotation (   fixed at 60  ) O H Xe H O H H O H H

7. 7 Microwave Study of Xe-H 2 O Rotational transitions within two internal rotor states were observed. [1] Rotational spectra within each internal rotor state were analyzed using a pseudodiatomic model. [1] Wen and Jäger, J. Phys. Chem. A 2006, 110, 7560.

8. 8 Spectroscopic Constants and Molecular Parameters of 129 Xe-H 2 O 129 Xe-H 2 OH 2 O-H 2 O [1] B (MHz) 2051.2166(2) D J (MHz) 0.031479(9) R 0 (Å) 3.9493.018 s (cm -1 ) 34.9 k s (Nm -1 ) 1.1410.8 Xe H2OH2O [1] Dyke, et al. J. Chem. Phys. 1977, 66, 498.

9. 9 J = 2-1 Transition of 131 Xe-H 2 O I = 3/2 800 cycles  aa = -0.445(2) MHz F’-F”

10. 10 Effective H 2 O Orientation Effective structure ab initio equilibrium structure  88.5º60º  38.9º0º0º O H H Xe   131 Xe-H 2 O:  aa ( 131 Xe)= -0.445(1) MHz 132 Xe-H 2 17 O:  aa ( 17 O)= -1.37(2) MHz

11. 11 Energy Level Diagram of Xe-(H 2 O) 2 1 01 2 02 3 03 4 04 5 15 0 00 4 14 3 13 2 12 1 11 4 13 3 12 2 11 1 10 3 22 2 21 3 21 2 20

12. 12 Spectroscopic Constants of 129 Xe-(H 2 O) 2 A (MHz) 6267.6349(8) B (MHz) 1401.2013(3) C (MHz) 1141.7199(2) D J (MHz) 0.005384(8) D JK (MHz) 0.0496(1) D K (MHz) -0.00069(13) d 1 (MHz) -0.001098(4) d 2 (MHz) -0.000282(15) H JK (MHz) 0.0000012(7)

13. 13 Structural Analysis of Xe-(H 2 O) 2 3.879 Å 2.992 Å Xe H2OH2O H2OH2O 3.879 Å [1] Dyke, et al. J. Chem. Phys. 1977, 66, 498. Xe-H 2 O dimer: R 0 = 3.948 Å (H 2 O) 2 dimer: R 0 = 3.018 Å [1]

14. 14 Harmonic Force Field Analysis of Xe-(H 2 O) 2 Xe H2OH2O H2OH2O Xe-H 2 O dimer: k s = 1.14 Nm -1 1.485(3) Nm -1 1.58(2) Nm -1 10.82(5) Nm -1 H 2 O-H 2 O dimer [1] : k s = 10.8 Nm -1 [1] Dyke, et al. J. Chem. Phys. 1977, 66, 498.

15. 15 J K a K c = 2 12 -1 01 Transition of 131 Xe-(H 2 O) 2 I = 3/2 2000 cycles  aa = 2.108(2) MHz  bb = -1.300(2) MHz |  ab | = 8.446(29) MHz F’-F”

16. 16 Analysis of Nuclear Quadrupole Coupling Constants Assumptions: Main contribution from H 2 O multipole moments. Additivity of electric field gradient at the Xe nucleus. OO H H Xe H H b a      

17. 17 Comparison of Calculated and Experimental Constants Exp. Calculated 1 (pairwise additivity)  aa (MHz) 2.1082.1572%  bb (MHz) -1.300-0.82437% |  ab | (MHz) 8.4466.40624% Calculated 2 (induced dipoles included) 2.49218% -0.94327% 7.7518%

18. 18 Summary Water undergoes large amplitude in-plane and out-of-plane rotations in the Xe-H 2 O dimer. The Xe-H 2 O interaction is hydrophobic. Inclusion of induced-dipole three-body term reproduces  ab of 131 Xe-(H 2 O) 2 to within 8%.

19. 19 Acknowledgements Jäger and Xu groups Mary Louise Imrie Graduate Student Award