THE ARGONCYCLOPENTADIENYL THALLIUM WEAKLYBOUND COMPLEX, ROTATIONAL SPECTRUM AND STRUCTURE1

1
THE ARGON-CYCLOPENTADIENYL THALLIUM WEAKLY-BOUND
COMPLEX, ROTATIONAL SPECTRUM AND STRUCTURE1
CHAKREE TANJAROON, ADAM DALY AND STEPHEN G.
KUKOLICH, Department of Chemistry, The University
of Arizona, Tucson, Arizona 85721
1) This material is based on work supported by
the National Science Foundation under Grant No.
CHE-0721505.
2
? Calculations were done to see if a bound
structure could be obtained for this complex

• ? MP2 and DFT calculations using Gaussian 03
• For Tl gt aug-cc-pVTZ-PP
• Other atoms gtDunnings 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
Ar-C5H5Tl

• Prolate symmetric-top rotor with C5V symmetry
• Argon atom is located on the a-axis of C5H5Tl
• 26 transitions measured for 205Tl, 15
  transitions for 203Tl
• Measured intermolecular r(Ar-Cp) 3.56 Å.
  (between argon and the cyclopentadienyl ring)
• DJ 0.12 kHz, DJK 0.45 kHz (relatively rigid
  complex)

4
Example spectrum for the JK ? JK 90 ? 80,
(A) 91 ? 81, (B) and 92 ? 82 (C) transitions.
(700 shots)
5
Molecular Constants
6
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 B03 / DJ ks / ?
• ? ks re2 / 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
Comparison of Ar X (aromatic) complexes
8
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
(No Transcript)
10
(No Transcript)
11
(C5H5 Tl)n chain structure from the x-ray
measurements1. Expt 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
Plot of the binding energy (cm-1) as a function
of r(Ar-Cp) for MP2 and DFT calculations. DFT gt
UNBOUND
13
Acknowledgements

• Department of Chemistry, University of Arizona.

• NF - 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