Assessment of an effective quasirelativistic methodology designed to study astatine chemistry in aqueous solution

Abstract

A cost-effective computational methodology designed to study astatine (At) chemistry in aqueous solution has been established. It is based on two-component spin-orbit density functional theory calculations and solvation calculations using the conductor-like polarizable continuum model in conjunction with specific astatine cavities. Theoretical calculations are confronted with experimental data measured for complexation reactions between metallic forms of astatine (At(+) and AtO(+)) and inorganic ligands (Cl(-), Br(-) and SCN(-)). For each reaction, both 1:1 and 1:2 complexes are evidenced. The experimental trends regarding the thermodynamic constants (K) can be reproduced qualitatively and quantitatively. The mean signed error on computed Log K values is -0.4, which corresponds to a mean signed error smaller than 1 kcal mol(-1) on free energies of reaction. Theoretical investigations show that the reactivity of cationic species of astatine is highly sensitive to spin-orbit coupling and solvent effects. At the moment, the presented computational methodology appears to be the only tool to gain an insight into astatine chemistry at a molecular level.

Gold nanoparticle bioconjugates labelled with 211At for targeted alpha therapy

“…Although astatine is generally treated as a halogen, it also shows a signicant metallic character in certain conditions. 5 The strength of aryl carbon-halogen bond for astatine is signi-cantly lower than that for iodine 6 which precludes the use of standard direct radio-iodination methods for labelling monoclonal antibodies (mAbs) with At have been reported. One from the recently developed approaches is based on application of small nanoparticles as vehicles for 211 At.…”

“…The biologically active fragment of Substance P(5-11), named shortly as SP (5)(6)(7)(8)(9)(10)(11), was conjugated to the gold nanoparticles to obtain bioconjugates targeting NK1 receptors on glioma cells. Previously it was found that Substance P in cerebrospinal uid exhibits a stability of 84% aer 24 hours, while the serum residence time is only 1 to 2 minutes due to the rapid degradation.…”

“…3. The transmission electron micrograph of AuNPs-S-PEG-Substance P (5)(6)(7)(8)(9)(10)(11) shows that the particles are uniformly dispersed with signicantly narrow size equal to 5 nm and to 15 nm (Fig. 3).…”

Effective bond orders from two-step spin–orbit coupling approaches: The I2, At2, IO+, and AtO+ case studies

“…16 Furthermore, stable At cationic forms (At + and AtO + ) exist in aqueous solution and their coordination chemistry has been experimentally explored by reporting complexation constants with various inorganic ligands. 17,18 As the longest-lived radionu-…”

Ion and Neutron Beams Discover New Facts from History

“…For therapeutic applications it is essential to ensure a stable bond to the targeting vector to minimise in vivo delabelling. Efforts are ongoing to improve the understanding of astatine chemistry by experiments with trace quantities supported by computational chemistry [Cha11]. Interestingly, the ionisation potential of astatine, one of the fundamental atomic properties of an element, was only experimentally determined by laser spectroscopy with astatine iso- Table 1.6.…”