Studies have shown that coordination of ligands in the equatorial plane of actinyl ions strongly influences the vibrational spectra and therefore the electronic structure of the AnO22+ moiety.  These influences are thought to result from: 1) competition between the �yl oxygen atoms and the equatorial ligands for the actinide 6d orbitals and/or 2) a change in electron density at the metal center correlating with the ligand's donor/acceptor properties.  While previous studies have probed this phenomenon, most have focused on uranyl and have not explored the transuranium elements or a broad spectrum of donor/acceptor ligands. Herein, we present our investigation aimed at elucidating and quantifying electronic trends across the actinide series.  Using Raman and FT-IR spectroscopy, we have probed a number of isostructural UO22+ and PuO22+ compounds that are charge balanced by a variety of counter cations.  In addition to gleaning general information about the electronic structure across the actinides, we have  used the vibrational spectra to quantify these changes between UO22+ and PuO22+ through determination of the stretching force constant (k1) and the interactive force constant (k12) for the AnO22+ ions using the measured  symmetric and asymmetric stretches of these compounds. Figure 1.  Overlay of the Raman spectra for [Me4N]2AnO2Cl4 (An = U, blue; Pu, red) as well as the solid state molecular structure of [Me4N]2PuO2Cl4.

Raman and infrared studies of U(VI) and Pu(VI) complexes

246th National Meeting (2013)

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