References of "Desreux, Jean-François"
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See detailNuclear Magnetic Resonance and Nuclear Waste Reprocessing.
Vidick, Geoffrey ULg; Bouslimani, Nouri; Desreux, Jean-François ULg

Poster (2011, November 22)

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See detailNMR investigation of the lanthanide and actinide complexes of bis-triazine extracting agents
Desreux, Jean-François ULg; Vidick, Geoffrey ULg; Bouslimani, Nouri

in Valuenza, Fernando L.; Moyer, Bruce A. (Eds.) 19th International Solvent Extraction Conference (2011, October 07)

Nuclear magnetic resonance spectroscopy (NMR) is applied to unravel the solution structure and the stoichiometry of the complexes formed between bis-triazine extracting agents (BTP and BTBP) and ... [more ▼]

Nuclear magnetic resonance spectroscopy (NMR) is applied to unravel the solution structure and the stoichiometry of the complexes formed between bis-triazine extracting agents (BTP and BTBP) and paramagnetic lanthanide ions. Highly rigid lanthanide perchlorate tris-complexes of threefold symmetry are formed by the pyridine bis-triazine BTP¿s while the bipyridine analogues (BTBP) form bis-complexes with a more open structure that leaves enough space for solvent molecules or anions. The nitrate ion is unable to enter the first coordination sphere of the tris-BTP complexes but the structure and stoichiometry of the bis-BTBP chelates are profoundly modified in presence of this ion. The NMR analysis is extended to actinides in various oxidation states despite technical difficulties. The NpO2+ ion is shown to form a 1:1 BTP complex in which the ligand is located in the plane perpendicular to the dioxo unit. No covalency contribution could be detected in the NMR spectra but such a contribution is clearly visible in the case of Am3+ and Cm3+. The latter induces very large paramagnetic shifts with a large contact contribution. [less ▲]

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See detailStealth macromolecular platforms for the design of MRI blood pool contrast agents
Grogna, Mathurin ULg; Cloots, Rudi ULg; Luxen, André ULg et al

in Polymer Chemistry (2011), 2(10), 2316-2327

Stealth macromolecular platforms bearing alkyne groups and poly(ethylene oxide) brushes were synthesized by reversible addition fragmentation chain transfer (RAFT) polymerization. The anchoring of Gd3 ... [more ▼]

Stealth macromolecular platforms bearing alkyne groups and poly(ethylene oxide) brushes were synthesized by reversible addition fragmentation chain transfer (RAFT) polymerization. The anchoring of Gd3+-chelates bearing an azide group was then carried out by the Huisgen 1,3-dipolar cycloaddition (“click”) reaction in mild conditions, leading to macrocontrast agents for MRI applications. The gadolinium complex is hidden in the PEO shell that renders the macrocontrast agents free of any cytotoxicity and stealth to proteins of the immune system. Relaxometry measurements have evidenced an improved relaxivity of the macrocontrast agent compared to ungrafted gadolinium chelate. Moreover, this relaxivity is further enhanced when the spacer length between the Gd3+-chelate and the polymer backbone is shorter, as the result of its decreased tumbling rate. These novel products are therefore promising candidates for MRI applications. [less ▲]

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See detailConvenient grafting through approach for the preparation of stealth polymeric blood pool magnetic resonance imaging contrast agents
Grogna, Mathurin ULg; Cloots, Rudi ULg; Luxen, André ULg et al

in Journal of Polymer Science. Part A, Polymer Chemistry (2011), 49(17), 3700-3708

New hydrosoluble magnetic resonance imaging (MRI) macrocontrast agents are synthesized by reversible addition fragmentation chain transfer (RAFT) copolymerization of poly(ethylene oxide) methyl ether ... [more ▼]

New hydrosoluble magnetic resonance imaging (MRI) macrocontrast agents are synthesized by reversible addition fragmentation chain transfer (RAFT) copolymerization of poly(ethylene oxide) methyl ether acrylate (PEOMA) with an acrylamide bearing a ligand for gadolinium, followed by the complexation of Gd3+. This convenient and simple grafting through approach leads to macrocontrast agents with a high relaxivity at high frequency that is imparted by the restricted tumbling of the Gd3+ complex caused by its attachment to the polymer backbone. Importantly a very low protein adsorption is also evidenced by the hemolytic CH50 test. It is the result of the poly(ethylene oxide) (PEO) brush that efficiently hides the gadolinium complex and renders it stealth to the proteins of the immune system. Improved contrast and long blood circulating properties are thus expected for these macrocontrast agents. [less ▲]

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See detailDesign and synthesis of novel DOTA(Gd3+)–polymer conjugates as potential MRI contrast agents
Grogna, Mathurin ULg; Cloots, Rudi ULg; Luxen, André ULg et al

in Journal of Materials Chemistry (2011), 21(34), 12917-12926

Conventional low molecular weight gadolinium based Magnetic Resonance Imaging (MRI) contrast agents such as Magnevist® are very useful for imaging tissues. However, at the high magnetic fields used in ... [more ▼]

Conventional low molecular weight gadolinium based Magnetic Resonance Imaging (MRI) contrast agents such as Magnevist® are very useful for imaging tissues. However, at the high magnetic fields used in modern MRI equipments, their relaxivity (contrasting efficiency) is rather poor. The grafting of the gadolinium complex onto macromolecules is a way to enhance their relaxivity provided that the rotational motion of the complex is decreased significantly. Here we report the design of novel Gd3+ based MRI contrast agents with improved relaxivity and potential long blood circulation life-time. We investigate the grafting of 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid, 1,4,7-tris(1,1-dimethylethyl) ester (DO3AtBu-NH2; a precursor of Gd3+ ligand) onto well-defined functional copolymers bearing activated esters (succinimidyl esters) and poly(ethylene oxide) (PEO) chains required for stealthiness. The tert-butyl groups of grafted DO3AtBu-NH2 are then deprotected by trifluoroacetic acid followed by complexation of Gd3+. Addition of free DOTA at the end of the reaction is necessary to leave the pure and stable water soluble macrocontrast agent. Importantly it shows a relaxivity at high frequencies that is 300% higher than that of the ungrafted gadolinium complex. These novel functional copolymers are therefore promising candidates as macromolecular contrast agents for MRI applications. [less ▲]

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See detailHighly Efficient Separation of Actinide from Lanthanide by a Phenanthroline-Derived Bis-triazine Ligand
Lewis, Frank W.; Harwood, Laurence M.; Hudson, Michael J. et al

in Journal of the American Chemical Society (2011), 133

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See detailNuclear Magnetic Resonance and Nuclear Waste Reprocessing.
Vidick, Geoffrey ULg; Bouslimani, Nouri; Desreux, Jean-François ULg

Poster (2011, April 29)

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See detailNMR Spectroscopy actinide complexes: In search of covalency effects
Desreux, Jean-François ULg; Vidick, Geoffrey ULg; Bouslimani, Nouri et al

Conference (2011, April 05)

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See detailGadolinium DOTA Chelates Featuring Alkyne Groups Directly Grafted on the Tetraaza Macrocyclic Ring: Synthesis, Relaxation Properties, "Click" Reaction, and High-Relaxivity Micelles
Vanasschen, Christian; Bouslimani, Nouri ULg; Thonon, David ULg et al

in Inorganic Chemistry (2011), 50(18), 8946-8958

This paper reports on the synthesis and relaxivity properties of tetraacetic DOTA-type chelating agents featuring one or two alkyne groups directly grafted on the tetraaza macrocyclic ring and available ... [more ▼]

This paper reports on the synthesis and relaxivity properties of tetraacetic DOTA-type chelating agents featuring one or two alkyne groups directly grafted on the tetraaza macrocyclic ring and available for "click" reactions with azide-bearing substrates. The racemic DOTAma ligand bearing one alkyne group was obtained by a bisaminal template route. The same approach was used to prep. ligand DOTAda substituted by two alkyne groups located on two adjacent carbon atoms. The S,S enantiomer of DOTAda was also prepd. by a "crab-like" condensation. This ligand is the first example of a DOTA deriv. featuring two reactive functions adjacent to each other on the macrocyclic ring. A triacetic monoalkyne ligand (DO3ma) was also synthesized for comparison purposes. NMR studies indicate that the Yb(III) chelates of DOTAma and DOTAda adopt two conformations in solns. in which the tetraaza ring is rigidified. The hydration state of the Eu(III) chelates was detd. by luminescence spectroscopy, and the water exchange time of the Gd(III) complexes was measured by 17O NMR. Ring substitution accelerates the water exchange. These data were used to interpret nuclear magnetic relaxation dispersion curves of the Gd(III) chelates. Two long aliph. chains have been added to DOTAda by a "click" procedure to form the (C18)2DOTAda ligand. The corresponding Gd(III) complex forms micelles of unusually high relaxivity presumably because of the close proximity of the aliph. chains on the macrocyclic ring that ensures a rigid double anchoring into the micelles. [less ▲]

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See detailImaging apolipoprotein AI in vivo
Sriram, Renuka; Lagerstedt, Jens; Petrlova, Jitka et al

in NMR in Biomedicine (2011), 24(7), 916-924

Coronary disease risk increases inversely with high-d. lipoprotein (HDL) level. The measurement of the biodistribution and clearance of HDL in vivo, however, has posed a tech. challenge. This study ... [more ▼]

Coronary disease risk increases inversely with high-d. lipoprotein (HDL) level. The measurement of the biodistribution and clearance of HDL in vivo, however, has posed a tech. challenge. This study presents an approach to the development of a lipoprotein MRI agent by linking gadolinium methanethiosulfonate (Gd[MTS-ADO3A]) to a selective cysteine mutation in position 55 of apo AI, the major protein of HDL. The contrast agent targets both liver and kidney, the sites of HDL catabolism, whereas the std. MRI contrast agent, gadolinium-diethylenetriaminepentaacetic acidbismethylamide (GdDTPA-BMA, gadodiamide), enhances only the kidney image. Using a modified apolipoprotein AI to create an HDL contrast agent provides a new approach to investigate HDL biodistribution, metab. and regulation in vivo. [less ▲]

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See detailNMR studies on radioactive actinide complexes. A completely foolish idea?
Vidick, Geoffrey ULg; Bouslimani, Nouri; Desreux, Jean-François ULg

Conference (2010, November 26)

The complete separation of actinides and lanthanides by solvent extraction is an important step in the reprocessing of nuclear wastes. The trivalent ions of these two families of f elements have very ... [more ▼]

The complete separation of actinides and lanthanides by solvent extraction is an important step in the reprocessing of nuclear wastes. The trivalent ions of these two families of f elements have very similar properties and it is only recently that an effective separation method has been developed. It is assumed that this separation can be achieved because of small differences in the covalency of the coordination bonds formed by the f ions but this has not been proved so far. We embarked into the first NMR study of the actinide complexes with the hope of better unravelling their solution structures and of clarifying the role of covalency. Nuclear magnetic resonance has nearly never been used for investigating actinide ions and their complexes not only because of their radioactivity and their toxicity but also because of the lack of dedicated spectrometers. It was also assumed that paramagnetism would cause excessive line broadenings. Many difficulties had thus to be overcome and the first step in our work was to show that well-resolved NMR spectra of actinide complexes (U to Cm) could indeed be obtained. Relatively narrow resonances have been observed for a variety of ions in different oxidation states provided their complexes are stable, symmetric and rigid. We used several advanced NMR techniques in order to fully characterize the actinide ions and their chelates in water or in organic solvents. The dispersion of the longitudinal relaxation time T1 of solvent nuclei with the magnetic field (NMRD) yields information on the magnetic properties and on the dynamic behaviour of paramagnetic species; 17O NMR allows the measurement of the water exchange times and 1H and 13C spectra yield information on the solution structures of the complexes. It will be shown that the paramagnetic shifts induced by the actinide ions originate from both a through space dipolar contribution and a through bonds contact contribution. The latter gives access to delocalized unpaired electron densities that are directly related to the covalency of the metal-ligand bonds. However, electron densities can only be obtained after separation of the two contributions. This could be accomplished thanks to variable temperature studies. In another approach, new ligands with rigid aliphatic substituents have been synthesized and contact contribution were deduced with the assumption that delocalization does not proceed to the 1H nuclei most removed from the metal center. This study has been extended to actinides in the trivalent, tetravalent and hexavalent states and new ligands have been synthesized in order to increase the magnetic anisotropy while keeping the symmetry and the rigidity needed to simplify the NMR analyses. [less ▲]

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See detailPolymer micelles decorated by gadolinium complexes as MRI blood contrast agents: design, synthesis and properties
Grogna, Mathurin ULg; Cloots, Rudi ULg; Luxen, André ULg et al

in Polymer Chemistry (2010), 1

New micellar macrocontrast agents with improved contrast at high frequencies were designed by grafting a gadolinium based contrast agent onto functional stealth micelles formed by poly(ethylene oxide)-b ... [more ▼]

New micellar macrocontrast agents with improved contrast at high frequencies were designed by grafting a gadolinium based contrast agent onto functional stealth micelles formed by poly(ethylene oxide)-b-poly(ε-caprolactone) (PEO-b-PCL) in water. As evidenced by relaxometry measurements and the hemolytic CH50 test, the new contrast agents are of interest as MRI blood pool agents. [less ▲]

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See detailStudies on the Interaction of a Novel 6,6¿¿- bis(1,2,4-triazin-3-yl)-,2¿:6¿,2¿¿-terpyridine Ligand with Lanthanide(III) Ions and Americium(III)
Lewis, Frank W.; Harwood, Laurence M.; Hudson, Michael J. et al

Conference (2010, April 01)

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See detailAN NMR INVESTIGATION OF THE ACTINIDE IONS AND THEIR COMPLEXES
Vidick, Geoffrey ULg; Bouslimani, Nouri; Desreux, Jean-François ULg

Poster (2010, January 28)

We currently use several advanced NMR techniques in order to fully characterize actinide ions and their complexes in water or in organic solvents. The dispersion of the longitudinal relaxation time T1 of ... [more ▼]

We currently use several advanced NMR techniques in order to fully characterize actinide ions and their complexes in water or in organic solvents. The dispersion of the longitudinal relaxation time T1 of solvent nuclei with the magnetic field (NMRD) yields information on the magnetic properties and on the dynamic behavior of paramagnetic species. 17O NMR allows the measurement of the water exchange times and 1H and 13C spectra yield information on the solution structures of the complexes and on the covalency of their coordination bonds. The application of NMR in actinide science will be illustrated with studies on the U, Np, Pu and Cm ions in different oxidation states and on their complexes. For instance, Cm3+ ion is the actinide analogue of Gd3+ but is not in a pure 8S state as indicated by much lower relaxation rates and much shortened electronic relaxation rates. In keeping with EPR studies1, Cm3+ does not have a perfectly spherical distribution of its unpaired electronic spins because of a much stronger spin-orbit coupling. Moreover, the Cm3+ relaxivity originates from three different processes: a dipolar coupling between the nuclear and electronic spins, a delocalization of unpaired electronic spins into the solvent orbitals (contact interaction) and a Curie contribution. Each process gives rise to an inflection point in the NMRD curves and the contact interaction reflects the partial covalency of the coordination bonds formed by Cm3+. A contact contribution is also observed in the NMR spectra of Cm3+ complexes. The sensitivity of NMR to the exact nature of the ground state of actinide ions is also illustrated by detailed studies on the U, Np and Pu ions in different oxidation states. For instance, a comparison of the NMRD curves of the 5f2 ions U4+, NpO2+ and PuO22+ indicates that the two dioxo cations have abnormally long electronic relaxation times. However, well-resolved 1H NMR spectra of their complexes can be obtained provided the solution species are sufficiently rigid. It will be shown that NpO2+ and PuO22+ induce dipolar paramagnetic shifts from which the solution structure can be deduced. [less ▲]

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See detailInteraction of 6,6-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-1,2,4-benzotriazin-3-yl)-2,2:6,2-terpyridine (CyMe4-BTTP) with some trivalent ions such as lanthanide(III) ions and americium(III)
Lewis, Frank; Harwood, Laurance; Hudson, Michael J. et al

in Dalton Transactions (2010), 39

The new solvent extraction reagent 6,6’’-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-1,2,4-benzotriazin-3-yl)-2,2’:6’,2’’-terpyridine (CyMe4-BTTP) has been synthesized in 4 steps from 2,2’:6’,2’’ ... [more ▼]

The new solvent extraction reagent 6,6’’-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-1,2,4-benzotriazin-3-yl)-2,2’:6’,2’’-terpyridine (CyMe4-BTTP) has been synthesized in 4 steps from 2,2’:6’,2’’-terpyridine. Detailed NMR and mass spectrometry studies indicate that the ligand forms 1:2 complexes with lanthanide(III) perchlorates where the aliphatic rings are conformationally constrained whereas 1:1 complexes are formed with lanthanide(III) nitrates where the rings are conformationally mobile. An optimized structure of the 1:2 solution complex with Yb(III) was obtained from the relative magnitude of the induced paramagnetic shifts. X-ray crystallographic structures of the ligand and of its 1:1 complex with Y(III) were also obtained. The NMR and mass spectra of [Pd(CyMe4-BTTP)]n2n+ are consistent with a dinuclear double helical structure (n = 2). In the absence of a phase-modifier, CyMe4-BTTP in 1-octanol showed a maximum distribution coefficient of Am(III) of 0.039 (±20%) and a maximum separation factor of Am(III) over Eu(III) of 12.0 from nitric acid. From nitric acid, the metal(III) cations are extracted as the 1:1 complex. The generally low distribution coefficients observed compared with the BTBPs arise because the 1:1 complex of CyMe4-BTTP is considerably less hydrophobic than the 1:2 complexes formed by the BTBPs. In M(BTTP)3+ complexes, there is a competition between the nitrate ions and the ligand for the complexation of the metal. [less ▲]

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