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Abdou Boucekkine - One of the best experts on this subject based on the ideXlab platform.
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Theoretical Investigation of the Electronic Structure and Magnetic Properties of Oxo-Bridged Uranyl(V) Dinuclear and Trinuclear Complexes
Inorganic Chemistry, 2019Co-Authors: Billel Teyar, Seddik Boucenina, Lotfi Belkhiri, Boris Le Guennic, Abdou Boucekkine, Marinella MazzantiAbstract:The uranyl(V) complexes [UO(dbm)K(18C6)] (dbm = dibenzoylmethanate) and [UO(L)](L = 2-(4-tolyl)-1,3-bis(quinolyl)malondiiminate), exhibiting diamond-shaped UO and triangular-shaped UO cores respectively with 5f-5f and 5f-5f-5f configurations, have been investigated using relativistic density functional theory (DFT). The bond order and QTAIM analyses reveal that the Covalent Contribution to the bonding within the oxo cores is slightly more important for UO than for UO, in line with the shorter U-O distances existing in the trinuclear complex in comparison to those in the binuclear complex. Using the broken symmetry (BS) approach combined with the B3LYP functional for the calculation of the magnetic exchange coupling constants () between the magnetic centers, the antiferromagnetic (AF) character of these complexes was confirmed, the estimated values being respectively equal to -24.1 and -7.2 cm for the dioxo and trioxo species. It was found that the magnetic exchange is more sensitive to small variations of the core geometry of the dioxo species in comparison to the trioxo species. Although the robust AF exchange coupling within the UO cores is generally maintained when small variations of the UOU angle are applied, a weak ferromagnetic character appears in the dioxo species when this angle is higher than 114°, its value for the actual structure being equal to 105.9°. The electronic factors driving the magnetic coupling are discussed.
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lanthanide iii and actinide iii complexes m bh4 2 thf 5 bph4 and m bh4 2 18 crown 6 bph4 m nd ce u synthesis crystal structure and density functional theory investigation of the Covalent Contribution to metal borohydride bonding
Inorganic Chemistry, 2009Co-Authors: Therese Arliguie, Lotfi Belkhiri, Abdou Boucekkine, Salaheddine Bouaoud, Pierre Thuery, Claude Villiers, Michel EphritikhineAbstract:Treatment of [M(BH4)3(THF)3] with NEt3HBPh4 in THF afforded the cationic complexes [M(BH4)2(THF)5][BPh4] [M = U (1), Nd (2), Ce (3)] which were transformed into [M(BH4)2(18-crown-6)][BPh4] [M = U (4), Nd (5), Ce (6)] in the presence of 18-crown-6; [U(BH4)2(18-thiacrown-6)][BPh4] (7) was obtained from 1 and 18-thiacrown-6 in tetrahydro-thiophene. Compounds 1, 3.C4H8S, 4.THF, 5, and 6.THF exhibit a penta- or hexagonal bipyramidal crystal structure with the two terdentate borohydride ligands in apical positions; the BH4 groups in the crystals of 7.C4H8S are in relative cis positions, and the thiacrown-ether presents a saddle shape, with two diametrically opposite sulfur atoms bound to uranium in trans positions. The crystal structures of these complexes, as well as those of previously reported [M(BH4)2(THF)5]+ cations, do not reveal any clear-cut lanthanide(III)/actinide(III) differentiation. The structural data obtained for [M(BH4)2(18-crown-6)]+ (M = U, Ce) by relativistic density functional theory (DFT) calculations are indicative of a small shortening of the U...B with respect to the Ce...B distance, which is accompanied by a lengthening of the U-Hb bonds and an opening of the Hb-B-Hb angle (Hb = bridging hydrogen atom of the eta3-BH4 ligand). The Mulliken population analysis and the natural bond orbital analysis indicate that the BH4 -->M(III) donation is greater for M = U than for M = Ce, as well as the overlap population of the M-Hb bond, thus showing a better interaction between the uranium 5f orbitals and the Hb atoms. The more Covalent character of the B-H-U three-center two-electron bond was confirmed by the molecular orbital (MO) analysis. Three MOs represent the pi bonding interactions between U(III) and the three Hb atoms with significant 6d and 5f orbital Contributions. These MOs in the cerium(III) complex exhibit a much lesser metallic weight with practically no participation of the 4f orbitals.
Lotfi Belkhiri - One of the best experts on this subject based on the ideXlab platform.
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Theoretical Investigation of the Electronic Structure and Magnetic Properties of Oxo-Bridged Uranyl(V) Dinuclear and Trinuclear Complexes
Inorganic Chemistry, 2019Co-Authors: Billel Teyar, Seddik Boucenina, Lotfi Belkhiri, Boris Le Guennic, Abdou Boucekkine, Marinella MazzantiAbstract:The uranyl(V) complexes [UO(dbm)K(18C6)] (dbm = dibenzoylmethanate) and [UO(L)](L = 2-(4-tolyl)-1,3-bis(quinolyl)malondiiminate), exhibiting diamond-shaped UO and triangular-shaped UO cores respectively with 5f-5f and 5f-5f-5f configurations, have been investigated using relativistic density functional theory (DFT). The bond order and QTAIM analyses reveal that the Covalent Contribution to the bonding within the oxo cores is slightly more important for UO than for UO, in line with the shorter U-O distances existing in the trinuclear complex in comparison to those in the binuclear complex. Using the broken symmetry (BS) approach combined with the B3LYP functional for the calculation of the magnetic exchange coupling constants () between the magnetic centers, the antiferromagnetic (AF) character of these complexes was confirmed, the estimated values being respectively equal to -24.1 and -7.2 cm for the dioxo and trioxo species. It was found that the magnetic exchange is more sensitive to small variations of the core geometry of the dioxo species in comparison to the trioxo species. Although the robust AF exchange coupling within the UO cores is generally maintained when small variations of the UOU angle are applied, a weak ferromagnetic character appears in the dioxo species when this angle is higher than 114°, its value for the actual structure being equal to 105.9°. The electronic factors driving the magnetic coupling are discussed.
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lanthanide iii and actinide iii complexes m bh4 2 thf 5 bph4 and m bh4 2 18 crown 6 bph4 m nd ce u synthesis crystal structure and density functional theory investigation of the Covalent Contribution to metal borohydride bonding
Inorganic Chemistry, 2009Co-Authors: Therese Arliguie, Lotfi Belkhiri, Abdou Boucekkine, Salaheddine Bouaoud, Pierre Thuery, Claude Villiers, Michel EphritikhineAbstract:Treatment of [M(BH4)3(THF)3] with NEt3HBPh4 in THF afforded the cationic complexes [M(BH4)2(THF)5][BPh4] [M = U (1), Nd (2), Ce (3)] which were transformed into [M(BH4)2(18-crown-6)][BPh4] [M = U (4), Nd (5), Ce (6)] in the presence of 18-crown-6; [U(BH4)2(18-thiacrown-6)][BPh4] (7) was obtained from 1 and 18-thiacrown-6 in tetrahydro-thiophene. Compounds 1, 3.C4H8S, 4.THF, 5, and 6.THF exhibit a penta- or hexagonal bipyramidal crystal structure with the two terdentate borohydride ligands in apical positions; the BH4 groups in the crystals of 7.C4H8S are in relative cis positions, and the thiacrown-ether presents a saddle shape, with two diametrically opposite sulfur atoms bound to uranium in trans positions. The crystal structures of these complexes, as well as those of previously reported [M(BH4)2(THF)5]+ cations, do not reveal any clear-cut lanthanide(III)/actinide(III) differentiation. The structural data obtained for [M(BH4)2(18-crown-6)]+ (M = U, Ce) by relativistic density functional theory (DFT) calculations are indicative of a small shortening of the U...B with respect to the Ce...B distance, which is accompanied by a lengthening of the U-Hb bonds and an opening of the Hb-B-Hb angle (Hb = bridging hydrogen atom of the eta3-BH4 ligand). The Mulliken population analysis and the natural bond orbital analysis indicate that the BH4 -->M(III) donation is greater for M = U than for M = Ce, as well as the overlap population of the M-Hb bond, thus showing a better interaction between the uranium 5f orbitals and the Hb atoms. The more Covalent character of the B-H-U three-center two-electron bond was confirmed by the molecular orbital (MO) analysis. Three MOs represent the pi bonding interactions between U(III) and the three Hb atoms with significant 6d and 5f orbital Contributions. These MOs in the cerium(III) complex exhibit a much lesser metallic weight with practically no participation of the 4f orbitals.
Marinella Mazzanti - One of the best experts on this subject based on the ideXlab platform.
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Theoretical Investigation of the Electronic Structure and Magnetic Properties of Oxo-Bridged Uranyl(V) Dinuclear and Trinuclear Complexes
Inorganic Chemistry, 2019Co-Authors: Billel Teyar, Seddik Boucenina, Lotfi Belkhiri, Boris Le Guennic, Abdou Boucekkine, Marinella MazzantiAbstract:The uranyl(V) complexes [UO(dbm)K(18C6)] (dbm = dibenzoylmethanate) and [UO(L)](L = 2-(4-tolyl)-1,3-bis(quinolyl)malondiiminate), exhibiting diamond-shaped UO and triangular-shaped UO cores respectively with 5f-5f and 5f-5f-5f configurations, have been investigated using relativistic density functional theory (DFT). The bond order and QTAIM analyses reveal that the Covalent Contribution to the bonding within the oxo cores is slightly more important for UO than for UO, in line with the shorter U-O distances existing in the trinuclear complex in comparison to those in the binuclear complex. Using the broken symmetry (BS) approach combined with the B3LYP functional for the calculation of the magnetic exchange coupling constants () between the magnetic centers, the antiferromagnetic (AF) character of these complexes was confirmed, the estimated values being respectively equal to -24.1 and -7.2 cm for the dioxo and trioxo species. It was found that the magnetic exchange is more sensitive to small variations of the core geometry of the dioxo species in comparison to the trioxo species. Although the robust AF exchange coupling within the UO cores is generally maintained when small variations of the UOU angle are applied, a weak ferromagnetic character appears in the dioxo species when this angle is higher than 114°, its value for the actual structure being equal to 105.9°. The electronic factors driving the magnetic coupling are discussed.
François Nief - One of the best experts on this subject based on the ideXlab platform.
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Theoretical Insights into the Nature of Divalent Lanthanide-Ligand Interactions
Organometallics, 2013Co-Authors: Stéphanie Labouille, Carine Clavaguéra, François NiefAbstract:The nature of the metal-ligand interaction in divalent samarium complexes is investigated by a variety of quantum chemical tools and compared to the analogous strontium-ligand interaction. The complexes under study are the decamethylsamarocene Sm(C5Me5)(2) the octamethyldiphosphasamarocene Sm(C4Me4P)(2), and the decamethylstrontocene Sr(C5Me5)(2). Molecular orbital descriptions, binding energy decompositions and topological analyses based on the electron density reveal the non-negligible role of covalency in the samarium-ligand interaction. The results are supported by an orbital energetic Contribution in the metal-ligand interaction and a number of samarium-carbon bond critical points and electron localization function valence basins. The Covalent Contribution to the samarium-ligand bond contrasts with the highly ionic strontium-ligand interaction.
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Theoretical Insights into the Nature of Divalent Lanthanide–Ligand Interactions
Organometallics, 2012Co-Authors: Stéphanie Labouille, Carine Clavaguéra, François NiefAbstract:The nature of the metal–ligand interaction in divalent samarium complexes is investigated by a variety of quantum chemical tools and compared to the analogous strontium–ligand interaction. The complexes under study are the decamethylsamarocene Sm(C5Me5)2, the octamethyldiphosphasamarocene Sm(C4Me4P)2, and the decamethylstrontocene Sr(C5Me5)2. Molecular orbital descriptions, binding energy decompositions and topological analyses based on the electron density reveal the non-negligible role of covalency in the samarium–ligand interaction. The results are supported by an orbital energetic Contribution in the metal–ligand interaction and a number of samarium–carbon bond critical points and electron localization function valence basins. The Covalent Contribution to the samarium–ligand bond contrasts with the highly ionic strontium–ligand interaction.
Boris Le Guennic - One of the best experts on this subject based on the ideXlab platform.
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Theoretical Investigation of the Electronic Structure and Magnetic Properties of Oxo-Bridged Uranyl(V) Dinuclear and Trinuclear Complexes
Inorganic Chemistry, 2019Co-Authors: Billel Teyar, Seddik Boucenina, Lotfi Belkhiri, Boris Le Guennic, Abdou Boucekkine, Marinella MazzantiAbstract:The uranyl(V) complexes [UO(dbm)K(18C6)] (dbm = dibenzoylmethanate) and [UO(L)](L = 2-(4-tolyl)-1,3-bis(quinolyl)malondiiminate), exhibiting diamond-shaped UO and triangular-shaped UO cores respectively with 5f-5f and 5f-5f-5f configurations, have been investigated using relativistic density functional theory (DFT). The bond order and QTAIM analyses reveal that the Covalent Contribution to the bonding within the oxo cores is slightly more important for UO than for UO, in line with the shorter U-O distances existing in the trinuclear complex in comparison to those in the binuclear complex. Using the broken symmetry (BS) approach combined with the B3LYP functional for the calculation of the magnetic exchange coupling constants () between the magnetic centers, the antiferromagnetic (AF) character of these complexes was confirmed, the estimated values being respectively equal to -24.1 and -7.2 cm for the dioxo and trioxo species. It was found that the magnetic exchange is more sensitive to small variations of the core geometry of the dioxo species in comparison to the trioxo species. Although the robust AF exchange coupling within the UO cores is generally maintained when small variations of the UOU angle are applied, a weak ferromagnetic character appears in the dioxo species when this angle is higher than 114°, its value for the actual structure being equal to 105.9°. The electronic factors driving the magnetic coupling are discussed.
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Covalency and magnetic anisotropy in lanthanide single molecule magnets: the DyDOTA archetype
Chemical Science, 2019Co-Authors: Matteo Briganti, Boris Le Guennic, Guglielmo Fernandez Garcia, Julie Jung, Roberta Sessoli, Federico TottiAbstract:Lanthanide ions when complexed by polyamino-polycarboxylate chelators form a class of compounds of paramount importance in several research and technological areas, particularly in the fields of magnetic resonance and molecular magnetism. Indeed, the gadolinium derivative is one of the most employed contrast agents for magnetic resonance imaging while the dysprosium one belongs to a new generation of contrast agents for T2-weighted MRI. In molecular magnetism, Single Molecule Magnets (SMMs) containing lanthanide ions have become readily popular in the chemistry and physics communities since record energy barriers to the reversal of magnetization were reported. The success of lanthanide complexes lies in their large anisotropy due to the Contribution of the unquenched orbital angular momentum. However, only a few efforts have been made so far to understand how the f-orbitals can be influenced by the surrounding ligands. The outcomes have been rationalized using mere electrostatic perturbation models. In the archetype compound [Na{Dy(DOTA) (H2O)}]·4H2O (Na{DyDOTA}·4H2O) an unexpected easy axis of magnetization perpendicular to the pseudo-tetragonal axis of the molecule was found. Interestingly, a dependency of the orientation of the principal magnetization axis on the simple rotation of the coordinating apical water molecule (AWM) – highly relevant for MRI contrast – around the Dy-OAWM bond was predicted by ab initio calculations, too. However, such a behaviour has been contested in a subsequent paper justifying their conclusions on pure electrostatic assumptions. In this paper, we want to shed some light on the nature of the subtle effects induced by the water molecule on the magnetic properties of the DyDOTA archetype complex. Therefore, we have critically reviewed the structural models already published in the literature along with new ones, showing how the easy axis orientation can dangerously depend on the chosen model. The different computed behaviors of the orientation of the easy axis of magnetization have been rationalized as a function of the energy gap between the ground and the first excited doublet. Magneto-structural correlations together with a mapping of the electrostatic potential generated by the ligands around the Dy(III) ion through a multipolar expansion have also been used to evidence and quantify the Covalent Contribution of the AWM orbitals.
