Functionalization using biocompatible carboxylated cyclodextrins of iron-based nanoMIL-100

Here we report the first example of nanoMIL-100 particles modified with monomeric cyclodextrin derivatives of different length by exploiting strong interactions between non-saturated iron trimers at the external surface and carboxylate functionalities located at the end of biocompatible and flexible linkers of cyclodextrins. The main results revealed that, after the functionalization, the cyclodextrins are selectively located at the external surfaces covering the nanoparticles. Z potential measurements show that this functionalization induced changes respect to the bare nanoMIL-100 particles, however, the presence of the cyclodextrins does not modify the size neither porosity of the nanoparticles. The amount of cyclodextrins attached, investigated by thermogravimetry, increases with the length of the linker between CD cavity and nanoparticle surface, reaching up a 9 % wt. Auger spectroscopy suggested a clear predominant sp3 character after the functionalizations (vs. sp2 predominance in the unmodified nanoMIL-100). This study supposes the creation of an alternative family of hybrids based on carboxylated monomeric cyclodextrins

Hybrid organic-inorganic mononuclear lanthanoid single ion magnets

The first family of hybrid mononuclear organic-inorganic lanthanoid complexes is reported, based on [PW11O39]7− and 1,10-phenanthroline ligands. This hybrid approach causes a dramatic improvement of the relaxation time (×1000) with a decrease of the optimal field while maintaining the Ueff of the inorganic analogues

Structural and Electronic Properties of Polyoxovanadoborates Containing the [V12B18O60] Core in Different Mixed Valence States

This review summarizes all published data until April 2015 related to crystalline lattices formed by the [V12B18O60] core, which generates polyanionic clusters with different degrees of protonation and mixed-valence ratios. The negative charge of this cluster is counterbalanced by different cations such as protonated amines, hydronium, and alkaline, and transition metal ions. The cluster is shown to form extended 1D, 2D, or 3D frameworks by forming covalent bonds or presenting hydrogen bond interactions with the present secondary cations. These cations have little influence on the solid state reflectance UV-visible spectra of the polyanionic cluster, but are shown to modify the FT-IR spectra and the magnetic behavior of the different reported species

A Novel Coordination Polymer Based on Decavanadate Units Linked by Copper(II) Ethylenediamine Complexes

International audienceA novel coordination polymer[{Cu(en)2}(V10O28)]n * 2n[Cu(en)2(H2O)] * 2n(H3BO3) * 2n(H2O) was obtained by hydrothermal reaction. The compound crystallizes in the monoclinic crystal system, in the C2/c space group, with a = 26.490 (3) Å; b = 11.6558 (11) Å; c = 19.8426 (19) Å; β = 124.011 (1)°; V = 5078.6(8) Å3. The solid structure is formed by polymeric chains, [Cu(en)2(H2O)]2+ cations, and boric acid and water solvate molecules, stabilized through a multiple hydrogen bond network

Coordination interactions in the crystalline lattice of alkaline ions with the polyoxometalate [V12B18O60H6]10− ligand

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Spin Frustrated Pyrazolato Triangular Cu^II Complex: Structure and Magnetic Properties, an Overview

The synthesis and structural characterization of a new triangular Cu3–μ3OH pyrazolato complex of formula, [Cu3(μ3−OH)(pz)3(Hpz)3][BF4]2 (1−Cu3), Hpz = pyrazole, is presented. The triangular unit forms a quasi-isosceles triangle with Cu–Cu distances of 3.3739(9), 3.3571(9), and 3.370(1) Å. This complex is isostructural to the hexanuclear complex [Cu3(μ3−OH)(pz)3(Hpz)3](ClO4)2]2 (QOPJIP). A comparative structural analysis with other reported triangular Cu3–μ3OH pyrazolato complexes has been carried out, showing that, depending on the pyrazolato derivative, an auxiliary ligand or counter-anion can affect the nuclearity and/or the dimensionality of the system. The magnetic properties of 1−Cu3 are analyzed using experimental data and DFT calculation. A detailed analysis was performed on the magnetic properties, comparing experimental and theoretical data of other molecular triangular Cu3–μ3OH complexes, showing that the displacement of the μ3−OH− from the Cu3 plane, together with the type of organic ligands, influences the nature of the magnetic exchange interaction between the spin-carrier centers, since it affects the overlap of the magnetic orbitals involved in the exchange pathways. Finally, a detailed comparison of the magnetic properties of 1−Cu3 and QOPJIP was carried out, which allowed us to understand the differences in their magnetic properties

Substitution Effect on the Charge Transfer Processes in Organo-Imido Lindqvist-Polyoxomolybdate

Two new aromatic organo-imido polyoxometalates with an electron donor triazole group ([n-Bu4N]2[Mo6O18NC6H4N3C2H2]) (1) and a highly conjugated fluorene ([n-Bu4N]2[Mo6O18NC13H9]) (2) have been obtained. The electrochemical and spectroscopic properties of several organo-imido systems were studied. These properties were analysed by the theoretical study of the redox potentials and by means of the excitation analysis, in order to understand the effect on the substitution of the organo-imido fragment and the effect of the interaction to a metal centre. Our results show a bathochromic shift related to the charge transfer processes induced by the increase of the conjugated character of the organic fragment. The cathodic shift obtained from the electrochemical studies reflects that the electronic communication and conjugation between the organic and inorganic fragments is the main reason of this phenomenon

Slow Relaxation of the Magnetization on Frustrated Triangular FeIII Units with S= 1/2 Ground State: The Effect of the Highly Ordered Crystal Lattice and the Counteranions

In order to understand how the different arrangements of highly ordered triangular FeIII S = 1/2 systems with various types of diamagnetic and paramagnetic anions affect their static and dynamic magnetic properties, we have obtained by solvothermal synthesis four new μ3-oxido trinuclear FeIII compounds, [Fe3O(Ac)6(AcNH2)3][BF4]·(CH3CONH2)0.5(H2O)0.5 (1-BF4), [Fe3O(Ac)6(AcNH2)3][GaCl4] (1-GaCl4), [Fe3O(Ac)6(AcNH2)3][FeCl4] (1-FeCl4) and [Fe3O(Ac)6(AcNH2)3][FeBr4] (1-FeBr4), where, Ac- = CH3COO- and AcNH2 = CH3CONH2. The organization of the triangular units is very varied, from segregated stacks to eclipsed equilateral triangular [Fe3O]+ units along the c-axis with intercalated [MX4]- units. The ordering of the triangular species together with disposition of the counteranions (intercalated or not) affects the static and dynamic magnetic properties of the [Fe3O]+ systems. Magnetic dc data were satisfactorily fitted with a HDvV spin Hamiltonian also considering the existence of anisotropic phenomena (antisymmetric exchange and intermolecular interactions), in order to model the low temperature region. From the antisymmetric exchange, we were able to obtain Δ (Ueff), which was used to model and rationalize the dynamic magnetic properties of these systems, reflecting that Orbach and Raman processes define the relaxation mechanism of these systems

New structures based on the mixed valence polyoxometalate cluster V12B18O60H6 (n-)

International audienceHydrothermal synthesis was used to obtain four new crystalline lattices derived from the functionalization of the [V12B18O60H6](n-) cluster: Na-8(H3O){[Ni(H2O)(5)][V12B18O60H6]}center dot 12.5H(2)O (1), Na-5 (H3O)(4){[Ni (H2O)(3)(en)][V12B18O60H6]}center dot 9H(2)O (2), and Na-9(H3O){Zn-0.5[V12B18O60H6]}center dot 11H(2)O (3), [Hen][H(2)en]{[Zn(en)(2)](3) [V12B18O60H6]}center dot 3H(2)O (4). All four compounds crystallize in the space group C2/c. Compounds (1) (2) and (4) are 0D species, while for (3) there is some degree of covalent connectivity between the anionic units, due to the presence of Zn-II cations with partial occupation between them. On the basis of structural data and BVS calculations, these functionalized cluster species present mixed-valence ratios of 11V(IV)/1V(V) for (1), (2) and (3) and 9V(IV)/3V(V) for compound (4). Compounds (1), (2) and (3) present sodium and hydronium ions in the crystalline lattice, while protonated ethylenediamine is observed in compound (4). These cations balance the negative charge of the corresponding clusters and stabilize the crystalline lattice by electrostatic interactions. In the studied compounds, Ni-II ions coordinate to the vanadyl oxygen atoms, whereas the Zn-II cations coordinate both to the vanadyl oxygen atoms and to the oxygen atoms bonded to boron centres. The electronic spectra in the low energy range are dominated by the IVCT phenomenon, since the functionalization of the cluster [V12B18O60H6](n-) by different transition metal ions does not affect the observed absorption bands

Crystal lattice effect on the quenching of the intracluster magnetic interaction in [V12B18O60H6] 10- polyoxometalate

In the present work, the synthesis and structural characterization of four new polyoxovanadoborate (BVO) frameworks based on the [V12B 18O60H6]10- polyanion are reported: (NH4)8(1,3-diapH2)[V12B 18O60H6]·5H2O (1), K 8(NH4)2[V12B18O 60H6]·18H2O (2), K10[V 12B18O60H6]·10H2O (3) and K8Cs2[V12B18O 60H6]·10H2O (4). A global antiferromagnetic behaviour is observed for these 10VIV/2V V mixed valence clusters. The magnetic data of 1, 2 and 3, which present different countercation environments, show that 1 is more coupled than 2 and 3. DFT calculations show that the positive charges strongly influence the polarization mechanism of the spin density of the vanadyl groups and the extent of the magnetic orbitals, therefore corroborating the experimental observation of the quenching effect of the magnetic coupling between vanadium centres of 2 and 3. © 2014 the Partner Organisations