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G. Steinhauser, G. Giester, C. Wagner, P. Weinberger, B. Zachhuber, G. Ramer, M. Villa, B. Lendl:
"Nitrogen-rich Compounds of the Actinoids: Dioxouranium(VI) 5,5′- Azobis[tetrazolide] Pentahydrate and Its Unusually Small Uranyl Angle";
Inorganic Chemistry, 51 (2012), 6739 - 6745.

Uranyl(VI) 5,5′-azobis[tetrazolide] pentahydrate was synthesized and characterized using X-ray crystallography, elemental analysis, UV/vis, MIR, FIR, and Raman spectroscopy. It is the second-most nitrogen rich compound of uranium (26.72 wt % N) and only the second structurally characterized uranium complex with a tetrazole ligand described in the literature. The compound´s structure is characterized by an exceptionally small uranyl angle of 172.4(1)°, which provides information on the coordination properties of tetrazole ligands as they affect the donor´s environment by strong steric and perhaps electrostatic repulsion. The compound showed luminescence under excitation with a near UV laser. The mean lifetime of its excited state was shorter than in the case of UO2(NO3)2·6H2O, indicating quenching by the ligand. Despite its high nitrogen content (and thus potentially explosive character), the title compound proved to be stable even under neutron radiation causing induced fission processes.
http://pubs.acs.org/articlesonrequest/AOR-t2yK9RB6uwWMSSxSpf3p

http://dx.doi.org/10.1021/ic300377j