A structural and (1)H NMR relaxometric study on novel layered carboxyalkylaminophosphonate nanocrystals with Gd(III) ions located in the framework

Relaxometric properties and biocompatibility of a novel nanostructured fluorinated gadolinium metal-organic framework

A novel Gd-MOF based on tetrafluoro-terephthalic acid has been synthesized and its structure has been solved using X-ray single crystal diffraction data. The compound, with the formula [Gd2(F4BDC)3·H2O]·DMF, is isostructural with other Ln-MOFs based on the same ligand and has been recently reported. Its crystals were also reduced to nanometer size by employing acetic acid or cetyltrimethylammonium bromide (CTAB) as a modulator. The relaxometric properties of the nanoparticles were evaluated in solution by measuring 1H T1 and T2 as a function of the applied magnetic field and temperature. The biocompatibility of Gd-MOFs was evaluated on murine microglial BV-2 and human glioblastoma U251 cell lines. In both cell lines, Gd-MOFs do not modify the cell cycle profile or the activation levels of ERK1/2 and Akt, which are protein-serine/threonine kinases that participate in many signal transduction pathways. These pathways are fundamental in the regulation of a large variety of processes such as cell migration, cell cycle progression, differentiation, cell survival, metabolism, transcription, tumour progression and others. These data indicate that Gd-MOF nanoparticles exhibit high biocompatibility, making them potentially valuable for diagnostic and biomedical applications.

Ferromagnetic 2p-2p and 4f-2p Couplings in a Macrocycle from Two Biradicals and Two Gadolinium(III) Ions

A new ground triplet biradical 2′,4′,6′-triisopropylbiphenyl-3,5-diyl bis(tert-butyl nitroxide) (iPr3BPBN) was prepared and characterized by means of room-temperature ESR spectroscopy displaying a zero-field splitting pattern together with a half-field signal. Complex formation with gadolinium(III) 1,1,1,5,5,5-hexafluoropentane-2,4-dionate (hfac) afforded a macrocycle [{Gd(hfac)3(μ-iPr3BPBN)}2]. As the X-ray crystallographic analysis clarified, the biradical serves as a bridging ligand, giving a 16-membered ring, where each nitroxide radical oxygen atom is directly bonded to a Gd3+ ion. The magnetic study revealed that the iPr3BPBN bridge behaved as a practically triplet biradical and that the Gd3+-radical magnetic coupling was weakly ferromagnetic. The exchange parameters were estimated as 2jrad-rad/kB > 300 K and 2JGd-rad/kB = 1.2 K in the H = −2J S1•S2 convention. The DFT calculation based on the atomic coordinates clarified the ground triplet nature in metal-free iPr3BPBN and the enhanced triplet character upon coordination. The calculation also suggests that ferromagnetic coupling would be favorable when the Gd-O-N-C(sp2) torsion comes around 100°. The present results are compatible with the proposed magneto-structure relationship on the nitroxide-Gd compounds.