Mixed 1D-2D inorganic polymeric zinc ferrocenylphosphonate: crystal structure and electrochemical study

Needs for ferrocene immobilization on robust host structures are considerable since derivative materials may find applications in medical areas, optical devices, or catalysis. Synthesis of phosphonate functionalized ferrocene allowed its subsequent inorganic polymerization with a zinc salt. The crystallographic structure of the compound obtained, Zn(HO(3)PFc)(2).2H(2)O, shows a unique two-dimensional ferrocene arrangement anchored on a one-dimensional Zn-O-P-O-Zn backbone. The ferrocene packing in the title compound is very similar to the packing found in molecular ferrocene. The electroactivity of Zn(HO(3)PFc)(2).2H(2)O is thoroughly studied. It shows a reversible surface oxidation of ferrocene. M?ssbauer spectroscopy for the oxidized compound shows an isomer shift of IS(2b) = 0.432 mm x s(-1) and a quadrupolar splitting of QS(2b) = 0.205 mm x s(-1), which is consistent with a stable S = 1/2 ferrocenium state. The magnetic susceptibility study, M?ssbauer spectroscopy, and galvanostatic titration show that only the ferrocene moieties present at the surface of the crystallites are reversibly oxidized. This observation is reinforced by a complex impedance study showing mainly resistive behavior and conductivity measurements indicating weak, thermally assisted, conductivity. The general properties of this compound demonstrate that phosphonato functionalization may be a useful approach for all fields concerned by immobilization of ferrocene.     

Tracing the reactive melting of glass-forming silicate batches by in situ 23Na NMR

The kinetics of the reaction of batches of powdered quartz and sodium carbonate was studied by in situ (23)Na nuclear magnetic resonance (NMR) spectroscopy using a laser-heated probe. We show for the first time that the technique allows one to study solid-state reactions at high temperatures with good time resolution and without the risk of quenching artifacts. The reaction is controlled by solid-state Na(+) diffusion across the grain interface. Independent of the batch composition, the first reaction product is crystalline sodium metasilicate, Na(2)SiO(3), even if the temperature is high enough for much of the composition space between silica and metasilicate to be above the equilibrium liquidus. Fast Na(+) diffusion allows the reaction front to cross the grain interface and form the solid product before liquid intermediate equilibrium products can be formed. This purely solid-state reaction slows down as the thickness of the interface increases; the reaction is more deceleratory than published models suggest. If excess quartz is present, it reacts in a second step involving a liquid film wetting the excess grains. Once this reaction has started, it pulls the reaction into the thermodynamic regime, which leads to an increase even in the rate of the first step leading to intermediate solid metasilicate.     

New structural motifs, unusual quenching of the emission, and second harmonic generation of copper(I) iodide polymeric or oligomeric adducts with para-substituted pyridines or trans-stilbazoles

The structural, emissive, and nonlinear optical properties of new CuI adducts with para-substituted trans-stilbazolic and pyridinic ligands are reported. Single-crystal X-ray diffraction results indicate that the para-substituent on the organic ligand greatly influences the structural motif by its steric (tert-butyl), electronic/steric (dimethylamino), or bridging-donor (cyano) properties so that two absolutely new structural motifs, polymeric and oligomeric, are found when trans-stilbazole and pyridine carry a dimethylamino group in the para-position. In addition, a surprising photoemission behavior is observed, being the solid-state emission of [CuI(trans-4-stilbazole)]n, [CuI(trans-4'-(dimethylamino)-4-stilbazole)]n, and [CuI(4'-tert-butyl-4-stilbazole)]n totally quenched. In the case of the noncentrosymmetric CuI adduct of trans-4'-(dimethylamino)stilbazole a discrete second harmonic generation (SHG) occurs.     

An investigation on the role of the nature of sulfonate ancillary ligands on the strength and concentration dependence of the second-order NLO responses in CHCl3 of Zn(II) complexes with 4,4'-trans-NC5H4CH=CHC6H4NMe2 and 4,4'-trans,trans-NC5H4CH=CH)2C6H4NMe2

To evidentiate the role of the nature of sulfonate ancillary ligands on the value of the quadratic hyperpolarizability of Zn(II) complexes with stilbazole-like ligands, the second-order nonlinear optical (NLO) properties of [ZnY(2)(4,4'-trans-NC5H4CH=CHC6H4NMe2)2] complexes (Y = CF3SO3, CH3SO3, or p-CH3C6H4SO3) are investigated. By working at relatively high concentrations (>3 x 10(-4) M), the positive effect of the triflate ligand remains unique while, with nonfluorinated sulfonate ligands, the second-order NLO response is comparable to that of the related complexes with acetate or trifluoroacetate as ancillary ligands. However, at dilutions higher than 10(-4) M, all of the sulfonate complexes reach huge quadratic hyperpolarizabilities because of solvolysis with the formation of cationic species such as [ZnY(4,4'-trans-NC5H4CH=CHC6H4NMe2)2]+, characterized by a large second-order NLO response. This view is supported by careful conductivity measurements. The same behavior occurs if 4,4'-trans-NC5H4CH=CHC6H4NMe2 is substituted by 4,4'-trans,trans-NC5H4(CH=CH)2C6H4NMe2.     

In situ formation of C-glycosides during electrospray ionization tandem mass spectrometry of a series of synthetic amphiphilic cholesteryl polyethoxy neoglycolipids containing <Emphasis Type="Italic">N</Emphasis>-acetyl-D-glucosamine

In this communication, the structural analysis of six synthetic O-Linked amphiphilic cholesteryl polyethoxy neoglycolipids containing N-acetyl-D-glucosamine was performed by electrospray ionization mass spectrometry in the positive ion mode, with a QqTOF-MS/MS hybrid instrument. The MS/MS analyses provided evidence for the "in situ" formation, in the collision cell of the tandem mass spectrometer, of an unexpected and unique [C-glycoside]+ product ion, resulting from an ion-molecule reaction between the N-acetyl-D-glucosamine oxonium ion and the neutral cholesta-3,5-diene molecule. Quasi MS3 analysis of this ion resulted in the dissociation of the precursor [C-glycoside]+ ion, which produced the expected third generation N-acetyl-D-glucosamine oxonium and the protonated cholesta-3,5-diene product ions.     

Preliminary Study of New Gallium-68 Radiolabeled Peptide Targeting NRP-1 to Detect Brain Metastases by Positron Emission Tomography

Due to their very poor prognosis and a fatal outcome, secondary brain tumors are one of the biggest challenges in oncology today. From the point of view of the early diagnosis of these brain micro- and macro-tumors, the sensitivity and specificity of the diagnostic tools constitute an obstacle. Molecular imaging, such as Positron Emission Tomography (PET), is a promising technique but remains limited in the search for cerebral localizations, given the commercially available radiotracers. Indeed, the [¹⁸F]FDG PET remains constrained by the physiological fixation of the cerebral cortex, which hinders the visualization of cerebral metastases. Tumor angiogenesis is recognized as a crucial phenomenon in the progression of malignant tumors and is correlated with overexpression of the neuropilin-1 (NRP-1) receptor. Here, we describe the synthesis and the photophysical properties of the new gallium-68 radiolabeled peptide to target NRP-1. The KDKPPR peptide was coupled with gallium-68 anchored into a bifunctional NODAGA chelating agent, as well as Cy5 for fluorescence detection. The Cy5 absorbance spectra did not change, whereas the molar extinction coefficient (ε) decreased drastically. An enhancement of the fluorescence quantum yield (φ_F) could be observed due to the better water solubility of Cy5. [⁶⁸Ga]Ga-NODAGA-K(Cy5)DKPPR was radiosynthesized efficiently, presented hydrophilic properties (log D = −1.86), and had high in vitro stability (>120 min). The molecular affinity and the cytotoxicity of this new chelated radiotracer were evaluated in vitro on endothelial cells (HUVEC) and MDA-MB-231 cancer cells (hormone-independent and triple-negative line) and in vivo on a brain model of metastasis in a nude rat using the MDA-MB-231 cell line. No in vitro toxicity has been observed. The in vivo preliminary experiments showed promising results, with a high contrast between the healthy brain and metastatic foci for [⁶⁸Ga]Ga-NODAGA-K(Cy5)DKPPR.     

Organocatalyzed Aldol Reaction between Pyridine‐2‐carbaldehydes and α‐Ketoacids: A Straightforward Route towards Indolizidines and Isotetronic Acids

Enantioselective aldol reactions between substituted pyridine carbaldehydes and α‐ketoacids were shown to provide isotetronic acids or their corresponding pyridinium salts, depending on the nature of the substituents on the pyridine ring. The pyridinium salts were generated through nucleophilic attack of the pyridine nitrogen atom onto the reactive keto functional group. Moderate‐to‐good yields of both compounds were typically obtained and high levels of enantioselectivity were observed by using benzimidazole pyrrolidine I as a catalyst. Hydrogenation of the resulting pyridinium salts led to new indolizidines with high ee values and diastereocontrol. X‐ray diffraction studies allowed the determination of the relative configuration of the products. Finally, DFT calculations were performed to rationalize the divergent pathway as a function of the pyridine substituents.     

Surface science approach to the solid-liquid interface: surface-dependent precipitation of Ni(OH)2 on α-Al2O3 surfaces

Surface-dependent precipitation: The adsorption of Ni(II) complexes in aqueous solution on (0001) and (1102) α-Al(2)O(3) single-crystal surfaces has been studied (see the X-ray absorption spectra obtained for parallel and perpendicular polarization directions). The use of planar model systems emphasizes the crucial role of the Al(2)O(3) orientation for Ni dispersion with practical implications in catalyst preparation procedures.