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What can quantum chemistry tell us about Pa(v) hydration and hydrolysis?

“…Some authors do not rule out the existence of PaO 2 + in noncomplexing media, 22 but others do not mention PaO 2 + among the possible Pa(V) species. 5,15,23 In this paper, thanks to quantum chemistry, we try to obtain some insight into this puzzling and controversial issue. DFT methods have recently been shown to provide realistic results for the hydration of the uranyl ion when using explicit two hydration layers.…”

“…1,2 Pa(V) has chemical analogies with Nb(V) and Ta(V), d elements of group five. [3][4][5] Nevertheless, theoretical calculations concluded that f-type atomic orbitals participate in Pa(V) bonding. 1 Now 91 Pa is between 90 Th and 92 U, both of which are most stable in their group oxidation state; it is generally believed that thorium behaves as a transition metal (bonding dominated by d-type atomic orbitals), whereas the participation of f-type atomic orbitals for uranium is well established.…”

Protactinium

“…Recently Trubert et al (Le Naour et al, 2003;Trubert et al, 1998Trubert et al, , 2002Trubert et al, , 2003 have obtained the hydrolysis constants for Pa(V) at the tracer level ($10 -12 M using 233 Pa) from the variations of the partition coefficient of Pa(V) in the system: TTA/toluene/Pa(V)/H 2 O/H þ /Na þ /ClO À 4 . These experiments were performed as a function of the concentrations of TTA and H þ at ionic strengths of 0.1 m 3 M and temperatures of 10 C T 60 C. From the hydrolysis constants obtained under these conditions extrapolations to zero ionic strength were performed using the specific ion interaction theory (SIT) (Grenthe and Puigdomenech, 1997).…”

“…Thermodynamic data related to the hydrolysis equilibria were derived from the temperature dependence of the hydrolysis constants at infinite dilution and are given in Table 4.14. Table 4.13 Equilibrium constants for the hydrolysis of Pa(V) at zero ionic strength ( from Trubert et al, 2003). Table 4.14 Standard thermodynamic data at 25 C derived from the experimental hydrolysis equilibria of Pa(V).…”

“…Table 4.14 Standard thermodynamic data at 25 C derived from the experimental hydrolysis equilibria of Pa(V). The thermodynamic values for the hydrolysis reaction forming Pa(OH ) 5 are considered to be estimates ( from Trubert et al, 2003).…”