Vibrational Predissociation Spectroscopy of Uranium Complexes Allen M. Ricks and Michael A. Duncan Department of Chemistry University of Georgia, Athens, GA 30602 www.arches.uga.edu/~maduncan Laura Gagliardi University of Minnesota, Minneappolis, MN 55455

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

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

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

Tunable IR Spectroscopy LaserVision Tunable Infrared Laser System designed by Dean Guyer Tuning range: ~600-4300 cm-1 Linewidth: ~1.0 cm-1 2000-4700 cm-1 Tunable mid-IR 2.3-5.0 m 600-2200 cm-1 Tunable 4.5-14.3 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.

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

Larger Uranium Carbonyl Clusters

=H2O =O

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

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

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