(211)At-labeled agents for alpha-immunotherapy: On the in vivo stability of astatine-agent bonds.

The application of (211)At to targeted cancer therapy is currently hindered by the rapid deastatination that occurs in vivo. As the deastatination mechanism is unknown, we tackled this issue from the viewpoint of the intrinsic properties of At-involving chemical bonds. An apparent correlation has been evidenced between in vivo stability of (211)At-labeled compounds and the At-R (R = C, B) bond enthalpies obtained from relativistic quantum mechanical calculations.

Structural, dynamical, and transport properties of the hydrated halides: How do At(-) bulk properties compare with those of the other halides, from F(-) to I(-)?

The properties of halides from the lightest, fluoride (F(-)), to the heaviest, astatide (At(-)), have been studied in water using a polarizable force-field approach based on molecular dynamics (MD) simulations at the 10 ns scale. The selected force-field explicitly treats the cooperativity within the halide-water hydrogen bond networks. The force-field parameters have been adjusted to ab initio data on anion/water clusters computed at the relativistic Möller-Plesset second-order perturbation theory level of theory.

Rationalization of the solvation effects on the AtO+ ground-state change.

(211)At radionuclide is of considerable interest as a radiotherapeutic agent for targeted alpha therapy in nuclear medicine, but major obstacles remain because the basic chemistry of astatine (At) is not well understood. The AtO(+) cationic form might be currently used for (211)At-labeling protocols in aqueous solution and has proved to readily react with inorganic/organic ligands. But AtO(+) reactivity must be hindered at first glance by spin restriction quantum rules: the ground state of the free cation has a dominant triplet character.

How does the solvation unveil AtO+ reactivity?

The AtO(+) molecular ion, a potential precursor for the synthesis of radiotherapeutic agents in nuclear medicine, readily reacts in aqueous solution with organic and inorganic compounds, but at first glance, these reactions must be hindered by spin restriction quantum rules. Using relativistic quantum calculations, coupled to implicit solvation models, on the most stable AtO(+)(H2O)6 clusters, we demonstrate that specific interactions with water molecules of the first solvation shell induce a spin change for the AtO(+) ground state, from a spin state of triplet character in the gas phase to a Kramers-restricted closed-shell configuration in solution. This peculiarity allows rationalization of the AtO(+) reactivity with closed-shell species in aqueous solution and may explain the differences in astatine reactivity observed in (211)At production protocols based on "wet" and "dry" processes.

Investigation of astatine(III) hydrolyzed species: experiments and relativistic calculations.

This work aims to resolve some controversies about astatine(III) hydroxide species present in oxidant aqueous solution. AtO(+) is the dominant species existing under oxidizing and acidic pH conditions. This is consistent with high-performance ion-exchange chromatography data showing the existence of one species holding one positive charge.

Introducing the ELF Topological Analysis in the Field of Quasirelativistic Quantum Calculations.

We present an original formulation of the electron localization function (ELF) in the field of relativistic two-component DFT calculations. Using I2 and At2 species as a test set, we show that the ELF analysis is suitable to evaluate the spin-orbit effects on the electronic structure. Beyond these examples, this approach opens up new opportunities for the bonding analysis of large molecular systems involving heavy and superheavy elements.

Large shift and small broadening of Br2 valence band upon dimer formation with H2O: an ab initio study.

Valence electronic excitation spectra are calculated for the H(2)O···Br(2) complex using highly correlated ab initio potentials for both the ground and the valence electronic excited states and a 2-D approximation for vibrational motion. Due to the strong interaction between the O-Br and the Br-Br stretching motions, inclusion of these vibrations is the minimum necessary for the spectrum calculation. A basis set calculation is performed to determine the vibrational wave functions for the ground electronic state and a wave packet simulation is conducted for the nuclear dynamics on the excited state surfaces.

Versatile coordination of 2-pyridinetetramethyldisilazane at ruthenium: Ru(II) vs Ru(IV) as evidenced by NMR, X-ray, neutron, and DFT studies.

The novel disilazane compound 2-pyridinetetramethyldisilazane (1) has been synthesized. The competition between N-pyridine coordination and Si-H bond activation was studied through its reactivity with two ruthenium complexes. The reaction between 1 and RuH(2)(H(2))(2)(PCy(3))(2) led to the isolation of the new complex RuH(2){(eta(2)-HSiMe(2))N(kappaN-C(5)H(4)N)(SiMe(2)H)}(PCy(3))(2) (2) resulting from the loss of two dihydrogen ligands and coordination of 1 to the ruthenium center via a kappa(2)N,(eta(2)-Si-H) mode.

An ab initio calculation of the valence excitation spectrum of H2O...Cl2: comparison to condensed phase spectra.

Valence electronic excitation spectra are calculated for the H(2)O...

Theoretical study of the potential energy surfaces of the Van Der Waals H2O-X2+ (X = Cl or Br) complexes.

An ab initio study of the interactions between H2O and Cl2+ and H2O and Br2+ has been performed. We present calculations using both the UMP2 level and the UCCSD(T) level of correlation with the aug-cc-pVTZ basis. The aug-cc-pVQZ basis was tested for selected geometries and was found to yield results similar to the smaller basis.

Agostic Si-H bond coordination assists C-H bond activation at ruthenium in bis(phosphinobenzylsilane) complexes.

Reaction of a phosphinobenzylsilane compound with ruthenium complexes leads to C-H and/or Si-H activation. The new complex Ru{eta(2)-H-SiMe2CH(o-C(6)H(4))PPh2}2 (5) was isolated and X-ray, NMR and DFT studies reveal that 5 displays two agostic Si-H interactions and two carbon-metallated bonds.

Synthesis, structure and coordination of the ambiphilic ligand (2-picolyl)BCy2.

The new pyridine-borane compound (2-picolyl)BCy2, readily prepared from 2-picolyllithium and ClBCy2, adopts a head-to-tail dimeric structure in the solid state as indicated by X-ray diffraction analysis and according to NMR and DFT studies, the dimeric form equilibrates in solution with a strained monomeric structure; the ambiphilic behavior of the new compound is illustrated by its bridging coordination to the (p-cymene)RuCl2 unit.