1. Vibrational Predissociation Spectroscopy of Uranium Complexes
Allen M. Ricks and Michael A. Duncan
Department of Chemistry
University of Georgia, Athens, GA 30602
Laura Gagliardi
University of Minnesota,
Minneappolis, MN 55455

2. Previous Work From the Duncan Group
Ta Forms 7-coordinate Species
J. Am. Chem. Soc. 131, 9176 (2009).
Ta+(CO)7
Ta+ has d4 e- configuration
Seven carbonyl ligands (2 e- each)
yields 18-electron complex
Capped octahedral structure;
Not pentagonal bipyramid.
More Info RG01
Thurs 1:30

3. Uranium and Uranium Oxide
Uranium commonly exists in U(VI) oxidation state
UF6 used in uranium enrichment
Uranium Carbonyl synthesis once a target of Manhattan Project
f-orbitals accessible in actinide complexes
Follow 22-electron rule - s2p6f14
U has 6 valence electrons, U+ has 5
U(VI) ions have been well studied, almost no studies of U(I) ions

4. Mass selection of cations by time-of-flight.
full mass spectrum
activate mass gate;
select one cluster mass.
excite at turning point.
Production of cold cations and complexes with laser vaporization in a supersonic expansion.
Mass selection of cations by time-of-flight.
Tunable laser photodissociation with IR OPO; measure fragment intensity versus wavelength.
photofragments
parent ion depletion

5. Tunable IR Spectroscopy
LaserVision Tunable Infrared Laser System
designed by Dean Guyer
Tuning range: ~ cm-1 Linewidth: ~1.0 cm-1
cm-1
Tunable mid-IR m
cm-1
Tunable m
OPO
OPA
idler
KTP
oscillator
KTA
diff. gen.
AgGaSe2
diff. gen.
532 nm
signal
(not used)
1 crystal
angle tuned
4 crystals
angle tuned
1 crystal
angle tuned
1064 nm
Pumped by pulsed, unseeded YAG
e.g., Spectra Physics PRO-230.

6. U+ and UO2+ Carbonyl Complexes
UO2+ has formal 5+ charge on uranium
Larger blue shift of CO than in H+CO (2184 cm-1)

7. Larger Uranium Carbonyl Clusters

8. =H2O =O

9. Uranium Superoxo Ion
UO4+ spectra in agreement with theoretical predictions for superoxo complex
η-2 ligand appears to have formal negative charge yielding U(VI) core ion
Additional O2 ligand binds weakly

10. Conclusions
The first U(I) carbonyl complexes have been synthesized and studied in the gas phase
Identified high symmetry eight coordinate 21-electron U(CO)8+ complex
Isolated and studied U(VI) superoxo complexes

11. Acknowledgements AFOSR and DOE for funding Prof. Michael Duncan
Prof. Mike Heaven (Emory)
Prof. Laura Gagliardi (Minnesota)