α-Trifluoroacetyl-δ-valerolactone: synthesis, acyl-lactone rearrangement and unexpected easy decarboxylation of the rearranged product

Claisen condensation of δ-valerolactone and ethyl trifluoroacetate leads to α-trifluoroacetyl-δ-valerolactone, existing completely in CDCl₃ solution as an enol. Upon treatment of this cyclic 1,3-ketoester with aqueous HCl, an acyl-lactone rearrangement takes place. The structure of the resulting pyran was confirmed by an X-ray analysis. The ability of the rearrangement product to lose its carboxylic group under unexpected mild conditions was used for the synthesis of the corresponding 3-unsubstituted cyclic hemi-ketal.     

Platinum nanoparticles generated in functionality-enhanced reaction media based on polyoctadecylsiloxane with long-chain functional modifiers

Functionality-enhanced nanostructured matrices generated by intercalating polyoctadecylsiloxane (PODS) with octadecene (ODC) or octadecylamine (ODA) are employed as reaction media in which to grow Pt nanoparticles. Small-angle X-ray scattering (SAXS) signatures confirm that the amphiphilic PODS matrix orders into lamellae with a periodicity (d) of 5.24 nm, which corresponds to the siloxy bilayer and a double layer of alkyl tails. The regular packing of the hydrophobic tails becomes distorted upon introduction of ODC or ODA. Incorporation of K[(C2H4)PtCl3].H2O (a Zeise salt) into the PODS/ODC matrix, followed by reduction of the Pt ions by NaBH4 or H2, results in the localization of Pt compounds and nanoparticles along the siloxy bilayers, which remain dimensionally unchanged. Electron density profiles deduced from PODS/ODA, however, provide evidence for considerable structural reorganization upon metalation with H2PtCl6.6H2O. In this case, the siloxy bilayers broaden due to the presence of PtCl62- ions, and the hydrophobic layers become distorted due to the formation of (PtCl62-)(ODAH+)2 complexes. Subsequent reduction by NaBH4 restores the inherent PODS organization, while H2 reduction partially preserves the distorted matrix, indicating that some Pt nanoparticles form in close proximity to the siloxy bilayer. Transmission electron microscopy reveals that relatively monodisperse Pt nanoparticles measuring approximately 1 nm in diameter are located along the siloxy bilayers, whereas anomalous SAXS further indicates that nanoparticles form aggregates of comparable size to d within the PODS double layers.     

The preparation and characterisation of ruthenium cyanovinylidene complexes

Reactions of half-sandwich ruthenium metal acetylide complexes with 1-cyano-4-dimethylaminopyridinium salts afford complexes containing mono- or di-cyanovinylidene ligands; the procedure can be adapted to permit the simple synthesis of a cyanoacetylide complex, via the in situ deprotonation of a primary cyanovinylidene complex.     

Morphology-controlled synthesis of ZnO nanostructures by a simple round-to-round metal vapor deposition route

One-dimensional ZnO nanostructures with different morphologies have been successfully synthesized through a simple round-to-round metal vapor deposition route at 550 degrees C with a zinc powder covered indium film as the source material. The structures and morphologies of the products were characterized in detail by using X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Studies found that the morphology of the products can be easily tuned from one experimental round to another. Possible growth mechanisms for the formation of one-dimensional ZnO nanostructures with different morphologies are discussed. Photoluminescence studies show that there are sharp UV emission and broad defect-related green emissions for the products obtained in all experimental rounds. Relative intensity of the UV emission to defect-related emissions gradually increased from one experimental round to another.     

Alkanethiols on platinum: multicomponent self-assembled monolayers

We have studied the formation of self-assembled monolayers (SAMs) of n-alkanethiols on platinum thin films using X-ray photoelectron spectroscopy (XPS), reflection-absorption infrared spectroscopy (RAIRS), spectroscopic ellipsometry (SE), and contact angle (CA) measurements. Specifically, SAMs of 1-hexanethiol, 1-dodecanethiol, and 1-octadecanethiol were grown on polycrystalline Pt films, and the effects of Pt surface preparation, deposition conditions, and solvent treatments on the initial quality and stability of the monolayer in air were investigated. The SAMs prepared under ambient conditions on piranha-cleaned and UV/ozone-cleaned substrates were compared to monolayers formed on template-stripped Pt in an inert atmosphere. We found that alkanethiols deposited from 1 mM ethanolic solutions on piranha-cleaned Pt formed densely packed monolayers in which alkyl chains were oriented close to the surface normal. Stored in the laboratory ambient, these monolayers were unchanged over about 1 week but were largely oxidized in about 1 month. No evidence was found of molecules being weakly bound within the monolayer or having undergone C-S bond scission; however, three distinct sulfur states were observed for all samples in the XPS of the S 2p region. The lowest- and highest-binding-energy components are assigned to alkylthiolate and partially oxidized alkylthiolate species, respectively. The remaining S 2p component (approximately one-third of the sulfur layer), intermediate in binding energy between the other two components, is attributed to a chemisorbed species with a S binding configuration distinct from the majority alkylthiolate: for example, S bound to Pt bound to O, S with a different Pt coordination number, or S in an adsorbed disulfide.     

Impact of reaction products on the Grignard reaction with silanes and ketones

Grignard reactions with alkoxysilanes or carbonyl compounds produce alkoxymagnesium halides as by-products. Kinetic measurements for reactions of silanes and of a ketone were performed with Grignard reagents, enriched in alkoxymagnesium halides and taken in a great excess.The alkoxide-type reaction products complex tightly with Grignard reagents and enhance in this way their nucleophilicity, thus accelerating the reaction. However, alkoxides branched at α-C atom exert an unfavorable steric hindrance to reaction resulting in a decrease in the reaction rate.     

Preparation and Crystal Structure of a New Uranyl Sulfate Templated by a Bis-isothiouronium Cation

Crystals of a new uranyl sulfate (C₂N₄H₈S₂)[UO₂(SO₄)₂] · 0.3H₂O ( 1 ) templated by a relatively rare bis-isothiouronium cation, were formed upon evaporation of aqueous solutions containing uranyl acetate, thiourea, and excess sulfuric acid. The new compound is orthorhombic, P2₁2₁2₁, a = 6.928(2) Å, b = 13.398(3) Å, c = 15.225(3) Å, Z = 2. Its crystal structure is comprised of [UO₂(SO₄)₂] moieties linked by hydrogen bonds formed between the template cations and terminal oxygen atoms of the sulfate tetrahedra. The C₂N₄H₈S₂²⁺ template is most likely formed in situ during a redox reaction between uranyl cation and thiourea in a strongly acidic medium, with UO₂²⁺ partially reduced to U⁴⁺.     

Extraction products from <Emphasis Type="Italic">Miscanthus</Emphasis> var. ‘Soranovskii’

The chemical structures of Miscanthus var. ‘Soranovskii’ lignin fractions released via extraction of lignin from the lignocellulosic feedstock using moderately heated acetone under atmospheric pressure, without acidic and alkaline catalysts, were studied. A blend of Miscanthus stems and leaves was pretreated with water under thermobaric conditions. The acetone organosolv process subsequently afforded a substance related to a lignin-like matter-acetone organosolv Miscanthus lignin (AOML). Non-destructive analytical techniques such as FTIR spectroscopy, gas chromatography-mass spectrometry, size-exclusion chromatography, and 2D NMR were used. The IR and NMR spectroscopies revealed the AOML structure to comprise all the three major types of phenylpropane units: guaiacyl (G), syringyl (S), and p-hydroxyphenyl (H). The resultant acetone-organosolv lignin exhibits good solubility in polar solvents, moderate solubility in aromatic chemicals, and is insoluble in non-polar solvents, exhibiting the physicochemical properties of a thermoplastic polymer with a softening point of 67.0°C (onset 33.0°C, endset 81.5°C).     

Synthesis and Evaluation of GdIII‐Based Magnetic Resonance Contrast Agents for Molecular Imaging of Prostate‐Specific Membrane Antigen

Magnetic resonance (MR) imaging is advantageous because it concurrently provides anatomic, functional, and molecular information. MR molecular imaging can combine the high spatial resolution of this established clinical modality with molecular profiling in vivo. However, as a result of the intrinsically low sensitivity of MR imaging, high local concentrations of biological targets are required to generate discernable MR contrast. We hypothesize that the prostate‐specific membrane antigen (PSMA), an attractive target for imaging and therapy of prostate cancer, could serve as a suitable biomarker for MR‐based molecular imaging. We have synthesized three new high‐affinity, low‐molecular‐weight Gd^III‐based PSMA‐targeted contrast agents containing one to three Gd^III chelates per molecule. We evaluated the relaxometric properties of these agents in solution, in prostate cancer cells, and in an in vivo experimental model to demonstrate the feasibility of PSMA‐based MR molecular imaging.