Plutonyl cation

Unlike the lanthanides, the actinides U, Np, Pu, and Am have a tendency to form linear actinyl dioxo cations with formula MeO and/or Me02. All these ions are paramagnetic except UO and they all have a non-spherical distribution of their unpaired electronic spins. Hence their electronic relaxation rates are expected to be very fast and their relaxivities, quite low. However, two ions, namely NpO and PuOl", stand out because of their unusual relaxation properties. This chapter will be essentially devoted to these ions that are both 5/. Some comments will be included later about UOi (5/°) and NpOi (5/ ). One should note here that there is some confusion in the literature about the nomenclature of the actinyl cations. The yl ending of plutonyl is often used indiscriminately for PuO and PuOl and the name neptunyl is applied to both NpO and NpOi. For instance, SciFinder Scholar" makes no difference between yl compounds in different oxidation states. Here, the names neptunyl and plutonyl designate two ions of the same 5f electronic structure but of different electric charge and... 

The majority of the chemistry that has been investigated for the actinide elements has been in aqueous solutions. For the light actinides in acidic solutions, four types of cations persist trivalent, tetravalent, pentavalent, and hexavalent. The later two ions are always found to have trans oxo ligands, making up a linear dioxo unit. Actinide ions of this type are typically referred to yls and have the names, uranyl (1, U02+/ +), neptunyl (2, Np02+ +), plutonyl (3, Pu02+ +), (4, Am02+/ ) and so on. 

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