The mechanism of water exchange in AmO2(H2O)5(2+) and in the isoelectronic UO2(H2O)5(+) and NpO2(H2O)5(2+) complexes as studied by quantum chemical methods

The water exchange mechanism for AmO2(H2O)52+ and the isoelectronic UO2(H2O)5+ and NpO2(H2O)52+ ions has been investigated using quantum chemical methods and compared to previous findings in the uranyl(VI) system (Vallet, V. et al. J. Am. Chem. Soc. 2001, 123, 11999). There are substantial and predictable changes in the geometry and preferred exchange pathways between uranyl(V) and the different actinyl(VI) complexes. The smaller charge on the uranyl(V) center makes the dissociative pathway more favorable than the associative/interchange pathways in the actinyl(VI) systems.