Synthesis, crystal structure and phase transitions of novel hybrid perovskite: bis(1,2-diaminopropane) di-µ-chloro-bis[diaquadichloromanganate(II)] dichloride.

Single crystals of bis(1,2-diaminepropane) di-µ-chloro-bis[diaquadichloromanganate(II)] dichloride have been prepared by evaporation from ethanoic solution. The triclinic X-ray crystal structure is built as layers of centrosymmetric dimers of [Mn(Cl)4(H2O)2]2- octahedra and 1,2-diaminopropane. The inorganic part consists of Mn octahedra sharing one edge and distributed in the basal ac plane along the a direction. These doubly negative charged layers are separated along the b axis by a positively charged diamine propane layer. One Cl- anion contributes to the electroneutrality of the crystal interacting with both inorganic - through a hydrogen bond network to the two water molecules coordinated to Mn - and organic layers via the NH3+ ammonium group. Differential scanning calorimetry shows two endothermic main peaks at T = 366 K and T = 375 K related to the release of the water molecules. The resulting dehydrated material is C-centered monoclinic as shown by powder X-ray diffraction.

Synthesis and characterization of a new monometallic layered double hydroxide using manganese.

This article reports for the first time the synthesis of an LDH using only manganese as the divalent and trivalent metallic ion. Analysis of the pH, redox potential, and chemical composition during the oxidation of a manganese basic salt using persulfate indicates the oxidation of 1/3 of the initial MnII ions, in agreement with the paramagnetic structure and XPS analysis. Infrared, Raman spectra and thermogravimetric analysis results were similar to the ones obtained with Fe-LDH also known as green rust. X-Ray diffractograms and Rietveld refinement were used to determine the structure of this solid. Thermodynamic considerations predict that this solid could reduce nitrate into gaseous nitrogen without further reduction to ammonium or ammonia unlike what is observed for Fe-LDH.

Birnessite: A New Oxidant for Green Rust Formation.

Iron and manganese are ubiquitous in the natural environment. FeII-FeIII layered double hydroxide, commonly called green rust (GR), and MnIII-MnIV birnessite (Bir) are also well known to be reactive solid compounds. Therefore, studying the chemical interactions between Fe and Mn species could contribute to understanding the interactions between their respective biogeochemical cycles. Moreover, ferromanganese solid compounds are potentially interesting materials for water treatment. Here, a {Fe(OH)2, FeIIaq} mixture was oxidized by Bir in sulphated aqueous media in the presence or absence of dissolved O2. In oxic conditions for an initial FeII/OH- ratio of 0.6, a single GR phase was obtained in a first step; the oxidation kinetics being faster than without Bir. In a second step, GR was oxidised into various final products, mainly in a spinel structure. A partial substitution of Fe by Mn species was suspected in both GR and the spinel. In anoxic condition, GR was also observed but other by-products were concomitantly formed. All the oxidation products were characterized by XRD, XPS, and Mössbauer spectroscopy. Hence, oxidation of FeII species by Bir can be considered as a new chemical pathway for producing ferromanganese spinels. Furthermore, these results suggest that Bir may participate in the formation of GR minerals.

Enhanced catalytic oxidation ability of ternary layered double hydroxides for organic pollutants degradation.

Co(2+) and Cu(2+) substituted MgAl layered double hydroxides with an M(2+)/M(3+) atomic ratio of 2.0 were synthesized by a co-precipitation method and fully characterized using various techniques including powder X-ray diffraction, ICP-AES analysis, FT-IR, DR UV-Vis spectroscopy, N2 adsorption-desorption and transmission electron microscopy. The materials revealed a good crystallinity with no phase impurity and successful substitution of cobalt and copper ions in the framework of binary LDH with the target ratio of metals in the sheet. The adsorption characteristics (kinetic and isotherm) and the catalytic oxidation of organic pollutants, methylene blue (cationic dye) and orange II (anionic) were carried out to investigate a potential use of LDH materials as catalysts. In particular, Co3Cu1Al2 LDH exhibited an excellent catalytic activity towards catalytic dye degradation, especially for orange II with good stability and reusability over several times. Furthermore, this LDH material showed good catalytic performance for several chlorophenol compounds, suggesting its practical application in wastewater treatment. Therefore, layered double hydroxides substituted with Co(2+) and Cu(2+) could be promising candidates in various applications, such as the abatement of organic pollutants.

Phthalimido-ferrocidiphenol cyclodextrin complexes: Characterization and anticancer activity.

Several ferrocenyl analogues of tamoxifen have already showed strong antiproliferative activity in experimental glioma models. Nevertheless, these compounds are very poorly soluble in water and an adapted formulation is needed. In this work, we have tailored and optimized methylated cyclodextrin soluble complexes of phthalimido-ferrocidiphenol for the first time. The complexes were characterized, and the optimized formulation was tested for in vitro efficacy and cell proliferation assays on U87, human glioblastoma cancer cells. Molecular modeling can provide accurate information about the inclusion process. The inclusion of all the moieties at the same time (i.e., ferrocene, phthalimidylpropyl, 2 phenols) is not possible due to the steric hindrance of the 1:4 system. The 1:3 systems are possible but do not seem very relevant. However, various 1:2 and 1:1 complexes are mostly present in aqueous solutions. Some experiments have confirmed our hypothesis. First, interactions between the phenol, phthalimidylpropyl and ferrocenyl groups have been observed in our NMR experiments. Second, the inclusion of phthalimidylpropyl was detected by UV-vis spectrophotometry with an apparent 1:1 interaction, which was observed through the Benesi-Hildebrand method. The complex is readily soluble in water and keeps its pharmacological activity against U87 tumor cells (IC50=0.028 ± 0.007 µM vs. 0.018 ± 0.003 µM for PhtFerr).

Metallo-solid lipid nanoparticles as colloidal tools for meso-macroporous supported catalysts.

Meso-macroporous silica containing iron oxide nanoparticles (15-20 nm) was synthesized by formulating solid lipid nanoparticles and metallosurfactant as both template and metal source. Because of the high active surface area of the catalyst, the material exhibits an excellent performance in a Fenton-like reaction for methylene blue (MB) degradation, even at low amount of iron oxide (5% TOC after 14 h).

Anharmonicity and isomorphic phase transition: a multi-temperature X-ray single-crystal and powder diffraction study of 1-(2'-aminophenyl)-2-methyl-4-nitroimidazole.

The harmonic model of atomic nuclear motions is usually enough for multipole modelling of high-resolution X-ray diffraction data; however, in some molecular crystals, such as 1-(2'-aminophenyl)-2-methyl-4-nitro-1H-imidazole [Paul, Kubicki, Jelsch et al. (2011 ▶). Acta Cryst. B67, 365-378], it may not be sufficient for a correct description of the charge-density distribution. Multipole refinement using harmonic atom vibrations does not lead to the best electron density model in this case and the so-called 'shashlik-like' pattern of positive and negative residual electron density peaks is observed in the vicinity of some atoms. This slight disorder, which cannot be modelled by split atoms, was solved using third-order anharmonic nuclear motion (ANM) parameters. Multipole refinement of the experimental high-resolution X-ray diffraction data of 1-(2'-aminophenyl)-2-methyl-4-nitro-1H-imidazole at three different temperatures (10, 35 and 70 K) and a series of powder diffraction experiments (20 ≤ T ≤ 300 K) were performed to relate this anharmonicity observed for several light atoms (N atoms of amino and nitro groups, and O atoms of nitro groups) to an isomorphic phase transition reflected by a change in the b cell parameter around 65 K. The observed disorder may result from the coexistence of domains of two phases over a large temperature range, as shown by low-temperature powder diffraction.

Fetuin is the key for nanon self-propagation.

"Nanobacteria", also known as nanons or calciprotein particles (CPP), are nano-sized protein mineral complexes which have been isolated from numerous biological sources. Nanons possess self-replication properties and contain only serum proteins (e.g. Fetuin-A, Albumin). Herein, we develop a simplified in vitro model of nanons propagation composed of only fetuin-A as a protein. Using this model, we demonstrate that fetuin from nanons possesses a different, non-native conformation. Moreover, we show that nanons induce soluble fetuin-A precipitation which could serve as a template for calcification. This phenomenon explains the observed self-propagating properties that mimic infectious behavior. We also demonstrate that renal calculi are capable of inducing a conformational change in fetuin-A, suggesting that the propagation phenomenon of nanons may occur in vivo.

Properties of metastable linkage NO isomers in Na2[Fe(CN)5NO]·2H2O incorporated in mesopores of silica xerogels.

We study the properties of photoinduced metal-nitrosyl linkage isomers in sodium nitroprusside (SNP) as a function of particle size. By embedding the molecular complex at various concentrations into mesopores of silica xerogels the size of the particles can be adjusted. The ground state is characterized by X-ray diffraction, absorption and infrared spectroscopy. The physical properties of the photoswitched molecules were analysed by steady-state low-temperature absorption, infrared spectroscopy and by nanosecond transient absorption spectroscopy. The electronic structure as well as the activation energies of the metastable linkage isomers are independent of the particle size down to single isolated molecules, indicating that the SNP complexes are quasi-free inside the pores of the gel.

Chemistry of cobalt(II) confined in the pores of ordered silica monoliths: from the formation of the monolith to the CoFe Prussian blue analogue nanocomposite.

Recently we conceived of an original strategy that allows the precipitation of Prussian blue analogues (PBAs) in the ordered pores of silica monoliths to lead to photomagnetic CoFe PBA-silica nanocomposites. To determine the critical parameters and fully control the synthesis of the photoactive CoFe PBA in the pores of the silica matrix, X-ray absorption spectroscopy was performed at the cobalt K-edge. This study showed that cobalt cation chemistry is the keystone of the entire process. The local environment and the electronic structure of the cobalt cation undergo several modifications during the formation process: first the incorporation of the cation as an octahedral complex into the ordered block copolymer phase, then the deprotonation by thermohydrolysis to give a fourfold-coordinated deprotonated lowly condensed species and finally the formation of the 3D coordination network of CoFe PBA in acidic conditions through a rapid reprotonation followed by nucleophilic substitution accompanied by the electronic transfer, thus leading to the photomagnetic Co(III)(LS)-Fe(II)(LS) (LS=low spin) pairs.

R-free factor and experimental charge-density analysis of 1-(2'-aminophenyl)-2-methyl-4-nitroimidazole: a crystal structure with Z' = 2.

The experimental charge-density distribution was determined for 1-(2'-aminophenyl)-2-methyl-4-nitro-1H-imidazole crystals. An anharmonic model was applied to the N atoms of both amino groups and to one nitro group in order to account for high residual peaks after harmonic multipole refinement and to obtain a better charge-density model. Free R-factor calculations [Brünger (1992). Nature, 355, 472-475] with restrained models implemented in MoPro were used to determine the degree of similarity of the two symmetry-independent molecules in the unit cell. The results are compared with 1-phenyl-4-nitroimidazole in order to analyze the influence of the amine and methyl functional groups. The asymmetric unit contains two symmetry-independent molecules giving rise to a dimer connected via strong N-H···N hydrogen bonds; these dimers are the building blocks of the crystal. In the crystal structure there are also weaker interactions and many short directional contacts (C-H···O, C-H···N and C-H···π), for which the Koch-Popelier topological criteria were applied. This analysis revealed that the C-H···π interactions lie at the border between weak hydrogen bonds and van der Waals interactions. Special attention was also paid to stabilizing H···H interactions. It turned out that the electron density, Laplacian and density energies at the critical points show an exponential dependence on the contact distance, similar to the relation found for other interactions.

Fully controlled precipitation of photomagnetic CoFe Prussian blue analogue nanoparticles within the ordered mesoporosity of silica monoliths.

The porosity of ordered mesoporous silica monoliths has been successfully used as nanoreactor for the elaboration of CoFe Prussian blue analogue nanoparticles. The nanocomposite exhibits a reversible photomagnetic effect different from that of typical powdered compounds due to particle size reduction.

Close-packed C(70)(3-) phases - synthesis, structure, and electronic properties.

The high symmetry and resulting electronic degeneracy of the C(60)(3)(-) anion is viewed as the key molecular feature in the high superconducting transition temperatures of fulleride and oxidized fullerene systems. The experimental evaluation of this hypothesis requires the synthesis of face-centered cubic (fcc) trivalent fulleride anion salts derived from higher fullerenes such as C(70), which have thus far proved elusive with only stable A(1)C(70), A(4)C(70), and A(6)C(70) phases known. In this paper, we report the synthesis of fcc A(3)C(70) phases stabilized by size-matching the tetrahedral site with the sodium cation. The structures are strongly dependent on the cooling protocol due to the existence of metastable partially or completely orientationally disordered phases. EPR data indicate that the phases are metallic but not superconducting. The densities of states at the Fermi level appear too low to give superconductivity at above 5 K, consistent with recent observations that four electrons per C(70) anion are required for superconductivity. Size-matching on both the octahedral and tetrahedral sites is required for A(3)C(70) stability - K(2)CsC(70) is only stable at elevated temperature and Na(2)C(70) is unstable, the composition corresponding to C(70) and a sodium-rich trigonal phase.