1. OSU – June - 20081 CHAKREE TANJAROON, ADAM DALY AND STEPHEN G. KUKOLICH, Department of Chemistry, The University of Arizona, Tucson, Arizona 85721 THE ARGON-CYCLOPENTADIENYL THALLIUM WEAKLY-BOUND COMPLEX, ROTATIONAL SPECTRUM AND STRUCTURE 1 1) This material is based on work supported by the National Science Foundation under Grant No. CHE-0721505.

2. OSU – June - 20082  Calculations were done to see if a bound structure could be obtained for this complex  MP2 and DFT calculations using Gaussian 03  For Tl > aug-cc-pVTZ-PP  Other atoms >Dunning’s aug-cc-pVTZ  Tested with Tl - halides Binding Energy = -6.4 kJ mol-1 = 535 cm -1 Calculated r(Ar-Cp) = 3.46 Å

3. OSU – June - 20083 Ar-C 5 H 5 Tl  Prolate symmetric-top rotor with C 5V symmetry  Argon atom is located on the a-axis of C 5 H 5 Tl  26 transitions measured for 205 Tl, 15 transitions for 203 Tl  Measured intermolecular r(Ar-Cp) =3.56 Å. (between argon and the cyclopentadienyl ring)  D J = 0.12 kHz, D JK = 0.45 kHz (relatively rigid complex)

4. OSU – June - 20084 Example spectrum for the J’ K’ → J K = 9 0 → 8 0, (A) 9 1 → 8 1, (B) and 9 2 → 8 2 (C) transitions. (700 shots)

5. OSU – June - 20085 Molecular Constants

6. OSU – June - 20086 Intermolecular Potential  Pseudo-diatomic - L-J Model  Consider Ar – X as diatomic  Lennard - Jones 6-12 Potential  VanderWaals stretching freq. = s  (2  s ) 2 = 4 B 0 3 / D J = k s /    = k s r e 2 / 72  Refs: S. J. Harris, S. E. Novick, W. Klemperer, J. Chem. Phys 60, 3208 (1974) M. R. Kennan, E. J. Campbell, T. J. Balle, L. W. Buxton, T. K Minton. P. D. Soper and W. H. Flygare, J. Chem. Phys. 72, 3070 (1980)

7. OSU – June - 20087 Comparison of Ar – X (aromatic) complexes

8. OSU – June - 20088 Potential energy surface profile for Ar-CpTl evaluated at the MP2/aug-cc-pVTZ-PP (Thallium)/aug-cc-pVTZ(Ar, C, H). The binding energy for the lowest energy structure is 4.6 kJ /mol.

9. OSU – June - 20089

10. 10

11. OSU – June - 200811 (C 5 H 5 – Tl) n chain structure from the x-ray measurements 1. Exp’t R(Tl-Tl) = 5.5 Å, Calculated(above) 5.51 Å 1. F. Olbrich, U. Behrens, Zeitschrift fuer Kristallographie - New Crystal Structures (1997), 212(1), 47.

12. OSU – June - 200812 Plot of the binding energy (cm-1) as a function of r(Ar-Cp) for MP2 and DFT calculations. DFT > UNBOUND

13. OSU – June - 200813 Acknowledgements N$F - This material is based upon work supported by the National Science Foundation under Grant No. CHE-0721505. This support from the National Science Foundation is gratefully acknowledged Department of Chemistry, University of Arizona.