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Introduction
Theoretical radiochemistry: gas phase chemistry, spectroscopy, chemistry in solution and chemical bonding.
Physical properties: magnetism.
Wave function theory calculations (CASSCF, CASPT2, NEVPT2, MRCI, SOCI, etc.).
Density functional theory calculations (DFT and 2c-DFT).
Publications
Publications (75)
The Dzyaloshinskii Moriya interaction is expected to be at the origin of interesting magnetic properties, such as multiferroicity, skyrmionic states and exotic spin orders. Despite this, its theoretical determination is far from being established, neither from the point of view of ab initio methodologies, nor from that of the extraction technique t...
As a non-covalent interaction, halogen bonding is now acknowledged to be useful in all fields where the control of intermolecular recognition plays a pivotal role. Halogen-bond basicity scales allow quantification of the halogen bonding of referential donors with organic functional groups from a thermodynamic point of view. Herein we present the pK...
Uranium trioxide, UO3, has a T-shaped structure with bent uranyl, UO22+, coordinated by an equatorial oxo, O2-. The structure of cation UO3+ is similar but with an equatorial oxyl, O•-. Neutral and cationic uranium trioxide coordinated by nitrates were characterized by collision induced dissociation (CID), infrared multiple-photon dissociation (IRM...
Magnetic anisotropy, in the absence of an external magnetic field, relates to the degeneracy lift of energy levels. In the standard case of transition metal complexes, this property is usually modeled by an anisotropic spin Hamiltonian and one speaks of "zero-field splitting" (ZFS) of spin states. While the case of mononuclear complexes has been ex...
This paper is a theoretical “proof of concept” on how the on-site first-order spin–orbit coupling (SOC) can generate giant Dzyaloshinskii–Moriya interactions in binuclear transition metal complexes. This effective interaction plays a key role in strongly correlated materials, skyrmions, multiferroics, and molecular magnets of promising use in quant...
The chemistry of linear uranyl(V/VI) dioxo cations, [Oyl–U–Oyl]+/2+, is dominated by coordination of uranium in the equatorial plane. Effects of this constraint were evaluated by experiment and theory for gas-phase mixed-valence UV/VI coordination dimers in which uranyl moieties are linked by alkyl dicarboxylates, [(UO2⁺)(UO2²⁺)(OOC-(CH2)n-2-COO2–)...
We report a methodology that allows the investigation of the consequences of the spin–orbit coupling by means of the QTAIM and ELF topological analyses performed on top of relativistic and multiconfigurational wave functions. In practice, it relies on the “state‐specific” natural orbitals (NOs; expressed in a Cartesian Gaussian‐type orbital basis)...
The halogen bond is a powerful tool for the molecular design, and pushing the limits of its strength is of major interest. Bearing the most potent halogen‐bond donor atom, astatine monoiodide (AtI) was recently successfully probed [Nature Chemistry 2018, 10, 428−434]. In this work, we continue the exploration of adducts between AtI and Lewis bases...
Scalar and spin-dependent relativistic effects can influence the geometries and wave functions of the ground and excited states of molecular systems in a way that is not always trivial. However, it is still common for researchers, in particular within the quantum chemistry community, to neglect the spin-dependent effects while discussing the bindin...
More than a hundred years after its discovery, the chemistry of the polonium radioelement is still largely unknown. However, it is quite clear that the properties of this heavy element ( Z = 84) may be affected by relativistic effects, in particular scalar relativistic effects and the so-called spin-orbit coupling (SOC). In this Article, we revisit...
A Schiff base ligand resulting from the reaction of ovanillin and 2,2-dimethyl-1,3-diaminopropane allows preparation of hetero-dinuclear [Ni-Ln]3+ or -trinuclear [Ni-Ln-Ni]3+ complexes. Although empirical parameters for rationalizing the strength of the ferromagnetic Ni-Gd interaction have been already discussed in several papers, no systematic stu...
The importance of halogen bonds-highly directional interactions between an electron-deficient σ-hole moiety in a halogenated compound and an acceptor such as a Lewis base-is being increasingly recognized in a wide variety of fields from biomedicinal chemistry to materials science. The heaviest halogens are known to form stronger halogen bonds, impl...
Zero-field splitting (ZFS) is one of the essential ingredients for the occurrence of magnetic bistability at a molecular level. It is commonly understood as the loss of degeneracy of the spin components of a spin-orbit free electronic state in the absence of an external magnetic field. The loss of degeneracy finds its origin in the combined action...
Hypervalent XF3 (X = Cl, Br, I, At) fluorides exhibit T-shaped C2V equilibrium structures with the heavier of them, AtF3 , also revealing an almost isoenergetic planar D3h structure. Factors explaining this behavior based on simple "chemical intuition" are currently missing. In this work, we combine non-relativistic (ClF3 ), scalar-relativistic and...
At is a most promising radionuclide for targeted alpha therapy. However, its limited availability and poorly known basic chemistry hamper its use. Based on the analogy with iodine, labelling is performed via astatobenzoate conjugates, but in vivo deastatination occurs, particularly when the conjugates are internalized in cells. Actually, the chemic...
Evidencing new chemical species in solution is particularly challenging when one works at ultra-trace concentrations, as is likely to happen with radioelements such as astatine (Z=85). Herein, quantum mechanical calculations were used to predict the narrow experimental domain in which it is possible to detect the presence of an exotic ternary triha...
Evidencing new chemical species in solution is particularly challenging when one works at ultra-trace concentrations, as is likely to happen with radioelements such as astatine (Z=85). Herein, quantum mechanical calculations were used to predict the narrow experimental domain in which it is possible to detect the presence of an exotic ternary triha...
The AtO(+) cation is one of the main chemical forms that appear in the astatine Pourbaix diagram. This form can react with closed-shell species in solution, while in the gas phase, it has a spin-triplet ground spin-orbit-free (SOF) state. Spin-orbit coupling (SOC) mixes its MS = 0 component with the (1)Σ(+) singlet-spin component, while keeping an...
A central goal of chemistry is to achieve ultimate oxidation states, including in gas-phase complexes with no condensed phase perturbations. In the case of the actinide elements, the highest established oxidation states are labile Pu(VII) and somewhat more stable Np(VII). We have synthesized and characterized gas-phase AnO3(NO3)2(-) complexes for A...
This work addresses the question of the identification of the excited states that are mainly responsible for the magnitude and nature of the magnetic anisotropy in high-spin mononuclear transition metal complexes. Only few states are actually responsible for the single ion magnetic anisotropy, and these states can be anticipated from rather simple...
Metal–organic frameworks, which are a special case of coordination polymers, form a class of materials with numerous applications due to their high porosities and large internal surface areas and in some cases also due to paramagnetic metal ions. A family of such materials of general formula M2(dobdc) (where M is a divalent metal ion, and dobdc4– i...
The main-group 6p elements did not receive much attention in the development of recent density functionals. In many cases it is still difficult to choose among the modern ones a relevant functional for various applications. Here, we illustrate the case of astatine species (At, Z = 85) and we report the first, and quite complete, benchmark study on...
The application of 211At 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 211At-labe...
It is generally assumed that astatide (At(-) ) is the predominant astatine species in basic aqueous media. This assumption is questioned in non-complexing and non-reductive aqueous solutions by means of high-pressure anion-exchange chromatography. Contrary to what is usually believed, astatide is found to be a minor species at pH=11. A different sp...
The presence of open metal sites along with a high porosity makes the Fe2(dobdc) metal-organic framework, also called Fe-MOF-74, particularly well suited for separating gaseous mixtures. For instance, since Fe2(dobdc) adsorbs O2 more strongly than N2, it can, in principle, be used to separate O2 from air [ Bloch et al. J. Am. Chem. Soc. 2011, 133,...
The potential energy surfaces of the group 17 XF3 (X = Cl, Br, I, At) fluorides have been investigated for the first time with multiconfigurational wave function
theory approaches. In agreement with experiment, bent T-shaped C
2v structures are computed for ClF3, BrF3, and IF3, while we predict that an average D
3h structure would be experimentally...
Magnetic anisotropy is responsible for the single molecule
magnet behavior of transition metal complexes. This behavior is characterized by a slow relaxation of the magnetization for low enough temperatures, and thus for a possible blocking of the magnetization. This bistable behavior can lead to possible technological applications in the domain of...
The nature of chemical bonds in heavy main-group diatomics is discussed from the viewpoint of effective bond orders, which are computed from spin-orbit wave functions resulting from spin-orbit configuration interaction calculations. The reliability of the relativistic correlated wave functions obtained in such two-step spin-orbit coupling framework...
Gas-phase plutonium nitrate anion complexes were produced by electrospray ionization (ESI) of a plutonium nitrate solution. The ESI mass spectrum included species with all four of the common oxidation states of plutonium: Pu(III), Pu(IV), Pu(V), and Pu(VI). Plutonium nitrate complexes were isolated in a quadrupole ion trap and subjected to collisio...
In benzophenone, intersystem crossing occurs efficiently between S1(nπ*) and the T1 state of dominant nπ* character, leading to excited triplet states after photoexcitation. The transition mechanism between S1(nπ*) and T1 is still a matter of debate, despite several experimental studies. Quantum mechanical calculations have been performed in order...
Carbon dioxide adsorption isotherms have been computed for the metal–organic framework (MOF) Fe2(dobdc), where dobdc4– = 2,5-dioxido-1,4-benzenedicarboxylate. A force field derived from quantum mechanical calculations has been used to model adsorption isotherms within a MOF. Restricted open-shell Møller–Plesset second-order perturbation theory (ROM...
The participation of the valence orbitals of actinides in bonding has been debated for decades. Recent experimental and computational investigations demonstrated the involvement of 6p, 6d and/or 5f orbitals in bonding. However, structural and spectroscopic data, as well as theory, indicate a decrease in covalency across the actinide series, and the...
A systematic study has been undertaken to determine how local distortions affect the overall (molecular) magnetic anisotropies in binuclear complexes. For this purpose we have applied a series of distortions to two binuclear Ni(II) model complexes and extracted the magnetic anisotropy parameters of multispin and giant-spin model Hamiltonians. Furth...
A multidentate, ligand platform is introduced that enables the isolation of both homo- and heterobimetallic complexes of divalent first-row transition metal ions such as Mn(II), Fe(II), and Co(II). By using a two-step metallation strategy, five bimetallic coordination complexes were synthesized with the general formula MMCl(py3tren), where py3tren...
The determination of anisotropic magnetic parameters is a task of both experimental and theoretical interest. The added value of theoretical calculations can be crucial for analyzing experimental data by (i) allowing assessment of the validity of the phenomenological spin Hamiltonians, (ii) allowing discussion of the values of parameters extracted...
Laser ionization of AnC4 alloys (An = Th, U) yielded gas-phase molecular thorium and uranium carbide cluster cations of composition AnmCn(+), with m = 1, n = 2-14, and m = 2, n = 3-18, as detected by Fourier transform ion-cyclotron-resonance mass spectrometry. In the case of thorium, ThmCn(+) cluster ions with m = 3-13 and n = 5-30 were also produc...
The metal-organic framework Fe2(dobdc) (dobdc(4-) = 2,5-dioxido-1,4-benzenedicarboxylate), often referred to as Fe-MOF-74, possesses many interesting properties such as a high selectivity in olefin/paraffin separations. This compound contains open-shell Fe(II) ions with open coordination sites which may have large single-ion magnetic anisotropies,...
By many-body quantum-chemical calculations, we investigate the role of two structural effects—local ligand distortions and the anisotropic Cd-ion coordination—on the magnetic state of Cd2Os2O7, a spin S=3/2 pyrochlore. We find that these effects strongly compete, rendering the magnetic interactions and ordering crucially dependent on these geometri...
This paper reports the experimental and theoretical investigations of two trigonal bipyramidal Ni(II) complexes, the [Ni(Me6tren)Cl](ClO4) 1 and [Ni(Me6tren)Br](Br) 2. High Field, High frequency Electron Paramagnetic Resonance spectroscopy performed on a single crystal of the [Ni(Me6tren)Cl](ClO4) 1 shows a giant uniaxial magnetic anisotropy with a...
The nature and magnitude of the magnetic anisotropy of heptacoordinate mononuclear Ni(II) and Co(II) complexes were investigated by a combination of experiment and ab initio calculations. The zero-field splitting (ZFS) parameters D of [Ni(H(2) DAPBH)(H(2) O)(2) ](NO(3) )(2) ⋅2 H(2) O (1) and [Co(H(2) DAPBH)(H(2) O)(NO(3) )](NO(3) ) [2; H(2) DAPBH=2...
The possible origin of the spiral spin structure in multiferroic LiCu2O2 is studied by calculating all relevant
isotropic and anisotropic magnetic interactions in the material. The coupling constants are extracted from
accurate ab initio quantum chemical calculations with an effective Hamiltonian theory. First, the anisotropic or Dzyaloshinskii-Mor...
Two novel mononuclear five-coordinate nickel complexes with distorted square-pyramidal geometries are presented. They result from association of a tridentate "half-unit" ligand and 6,6'-dimethyl-2,2'-bipyridine according to a stepwise process that highlights the advantage of coordination chemistry in isolating an unstable tridentate ligand by nicke...
Cupric oxide (CuO) has been described as belonging to the quasi-one-dimensional antiferromagnetic
compounds. It has also been suggested that cupric oxide possesses strong magnetic anisotropy, which is possibly
related to the observed ferroelectricity in this material. In this paper, the magnetic interactions of CuO are
investigated using the embedd...
The synthesis of a new Ni(II)-Y(III) binuclear complex with a marked elongation axis in the first coordination sphere of the Ni(II) ion is presented. Its zero-field splitting (ZFS) is studied by means of magnetic data and state-of-the-art ab initio calculations. A good agreement between the experimental and theoretical ZFS parameter values is encou...
Pentagonal-bipyramidal complexes [Co(DABPH)X(H(2)O)]X [X = NO(3) (1), Br (2), I (3)] were synthesized, and their magnetic behavior was investigated. Simulation of the magnetization versus temperature data revealed the complexes to be highly anisotropic (D ≈ +30 cm(-1)) and the magnitude of the anisotropy to be independent of the nature of the axial...
The zero-field splitting of the copper acetate monohydrate complex is studied using wave function based calculations. The anisotropy parameters extracted from highly correlated methods are in excellent agreement with the most accurate experimental results; in particular, the negative sign of the axial anisotropy parameter D is reproduced. During se...
Magnetic anisotropy is responsible for the slow relaxation of the magnetization in single molecule magnets. The main goal of this work is to understand the factors that govern local and intersite anisotropies in polynuclear compounds. For this purpose, correlated relativistic calculations are performed in mono- and bi-nuclear species. The main degr...
Magnetic anisotropy is responsible for the slow relaxation of the magnetization in single molecule magnets. The main goal of this work is to understand the factors that govern local and intersite anisotropies in polynuclear compounds. For this purpose, correlated relativistic calculations are performed in mono- and bi-nuclear species. The main degr...
The antisymmetric magnetic interaction is studied using correlated wave-functionbased
calculations in oxo-bridged copper bimetallic complexes. All of the anisotropic multispin
Hamiltonian parameters are extracted using spin-orbit state interaction and effective Hamiltonian
theory. It is shown that the methodology is accurate enough to calculate the...
The zero-field splitting (ZFS) of a model monometallic Mn(III) complex is theoretically studied as function of a systematic symmetry lowering. First, we treat the octahedral case for which the standard S.D.S model Hamiltonian cannot be applied due to a zero-field splitting in the absence of anisotropy induced by the spin-orbit coupling between the...
This paper studies the physical basis of the giant-spin Hamiltonian, which is usually used to describe the
anisotropy of single-molecule magnets. A rigorous extraction of the model has been performed in the weakexchange
limit of a binuclear centrosymmetric Ni�II� complex, using correlated ab initio calculations and
effective Hamiltonian theory. It...
The magnetic anisotropy of the [Ni2(en)4Cl2]2+ (en ) ethylenediamine) complex has
been studied using wave function based computational schemes. The spin-orbit state interaction
methodology provides accurate ab initio energies and wave functions that are used to interpret
the anisotropy in bimetallic complexes. The extraction of the anisotropic spin...
Monometallic Ni(II) and Co(II) complexes with large magnetic anisotropy are studied using correlated wave function based ab initio calculations. Based on the effective Hamiltonian theory, we propose a scheme to extract both the parameters of the zero-field splitting (ZFS) tensor and the magnetic anisotropy axes. Contrarily to the usual theoretical...
