Intermolecular vibrational mode of the benzoic acid dimer in solution observed by terahertz time-domain spectroscopy

The low-frequency modes of the benzoic acid (BA) dimer and its analogues in carbon tetrachloride (CCl(4)) have been investigated by terahertz time-domain spectroscopy. The solute spectrum is obtained by subtracting the solvent contribution from that of the solution. The difference spectrum of BA in CCl(4) has a broad band with a peak at 68 cm(-1). To assign the observed band, the spectrum is compared with spectra of other aromatic molecules, such as benzene and phenol in addition to p-methyl BA and deuterated BA species (BA-d(OH) and BA-d(5)) in CCl(4). The band at 68 cm(-1) is assigned to the cogwheel mode of the BA dimer. Density functional theory calculations also support this assignment. Finally, spectral lineshape analysis based on the multimode Brownian oscillator model is applied to the THz spectra for all the samples.     

Gas phase synthesis of Au clusters deposited on titanium oxide clusters and their reactivity with CO molecules

Titanium oxide clusters were formed in the gas phase by the laser ablation of a Ti rod in the presence of oxygen in a He gas. Not only stoichiometric but also nonstoichiometric titanium oxide clusters, Ti(n)O(2n+x)(+) (n = 1-22 and x = -1-3), were formed. The content of oxygen atoms depends strongly on a partial pressure of oxygen. Gold clusters, Au(m) (m = 1-4), were generated by the laser ablation, which were then deposited on Ti(n)O(2n+x) clusters. The formation of Au(m)Ti(n)O(2n+x)(+) follows electron transfer from Au(m) to Ti(n)O(2n+x)(+). The reactivity of Au(m)Ti(n)O(2n+x)(+) cluster ions with CO was examined for different m, n, and x by the mass spectrometry. It was found that Au(m) on Ti(n)O(2n-1)(+) are less reactive than those on the other Ti(n)O(2n+x)(+) (x = 0 and 1). In addition, the reactivity is highest when Au(m) (m = 1 and 3) is on the stoichiometric titanium oxide (x = 0), whereas the reactivity is also high when Au(2) is on the oxygen-rich titanium oxide (x = 1). The reactivity was found to relate to geometrical structures of Au(m)Ti(n)O(2n+x)(+), which were studied by density functional calculations.     

Nanoalloy formation of Ta-containing trimetallic small clusters

Trimetallic cluster ions containing Ta and other metal elements were prepared in the gas phase by a triple laser-ablation technique in a controlled manner. We have measured the abundances and their thermal stabilities, using time-of-flight mass spectrometry. Taking advantage of specific abundance distribution of the trimetallic cluster ions (magic stoichiometry), relative to the distinguished stabilities, the coalescence or the segregation of Ta and the other elements in the subnanometer sized clusters was discussed. We found that Nb, W, and Mo, which are categorized as elements with a high heat of vaporization, readily coalesce with Ta, while V, Al, Co, and Pt, which are categorized as elements with a low heat of vaporization, tend to be segregated from Ta. Our experiments, along with the calculation by another research group, suggest that the binding energies of atoms are related to the coalescence or segregation of clusters in the gas phase.     

Synthesis and properties of (E)-1,2-difluoroethylene derivatives: improvement of the ultraviolet light stability

The synthesis and properties of (E)-α,β-difluorostilbene derivatives were studied. In particular, we investigated three suppression methods of (E)–(Z) isomerisation by shortening the molecular conjugation length, which included the introduction of a fluorine atom into the ortho or para position of the benzene ring or the replacement of the benzene ring with a cyclohexane ring. The relationship between the molecular structure of liquid crystals and the level of isomerisation by ultraviolet (UV) light was discussed.     

Phosphorylation of Amine Compounds with Sodium Cyclo-triphosphate

Abstract

Among inorganic linear and cyclic phosphates, cyclo-triphosphate has drawn special attention for its high reactivity with various amine compounds. A ring opening reaction to produce N-alkylamidotriphosphate derivatives proceeds under moderate conditions, e.g., at room temperature in aqueous solution. In spite of its potentiality as a phosphorylating agent for amino groups, a systematic investigation on the reaction mechanism has not fully carried out. This may be due to the lack of analytical methods which allow the quantitative examination of the reactions. In this work, HPLC with an anion-exchanger column developed for phosphate compounds together with ³¹P-NMR were applied to a kinetic study. It has been clarified that; 1) the reactivity of amine compounds is primarily correlated with the basisity of the amino groups, i.e., pKa values of its conjugate acids, though, branching at α carbon of the amino group greatry retards the reaction rate because of steric hindrance, and 2) some bifunctional reagents, such as ethylenediamine, propanediamine, ethanol-amine, and some α-amino acids produce heterocycles which contain P-N bond through an intramolecular reaction following the ring opening of cyclo-triphosphate. Ba or Mg salts of N-alkylamidotriphosphate derivatives have been prepared from mono amines, diamines, aminoalcohols, and aminoacids.     

1,2,3-Triazol-5-ylidene-palladium complex catalyzed Mizoroki-Heck and Sonogashira coupling reactions

The bis-1,4-dimesityl-1,2,3-triazol-5-ylidene-palladium complex (1a) successfully catalyzes the Mizoroki-Heck and Sonogashira coupling reactions with aryl bromides to give the corresponding alkenes and alkynes, respectively, in good to excellent yields. In the Mizoroki-Heck reaction, electron-rich, electron-poor, and functionalized aryl bromides and alkenes are tolerated, while the substrates are limited to electron-poor aryl halides in the Sonogashira coupling reaction. The palladium complex also catalyzes cross-coupling reactions with aryl chlorides to give higher yields of products than does the bis-IMes-Pd complex analogue (2), under specific conditions.     

Biodegradable Nanoparticles Loaded with Levodopa and Curcumin for Treatment of Parkinson’s Disease

Background: Parkinson’s disease (PD) is the second most common age-related neurodegenerative disorder. Levodopa (L-DOPA) remains the gold-standard drug available for treating PD. Curcumin has many pharmacological activities, including antioxidant, anti-inflammatory, antimicrobial, anti-amyloid, and antitumor properties. Copolymers composed of Poly (ethylene oxide) (PEO) and biodegradable polyesters such as Poly (ε-caprolactone) (PCL) can self-assemble into nanoparticles (NPs). This study describes the development of NH₂–PEO–PCL diblock copolymer positively charged and modified by adding glutathione (GSH) on the outer surface, resulting in a synergistic delivery of L-DOPA curcumin that would be able to pass the blood–brain barrier. Methods: The NH₂–PEO–PCL NPs suspensions were prepared by using a nanoprecipitation and solvent displacement method and coated with GSH. NPs were submitted to characterization assays. In order to ensure the bioavailability, Vero and PC12 cells were treated with various concentrations of the loaded and unloaded NPs to observe cytotoxicity. Results: NPs have successfully loaded L-DOPA and curcumin and were stable after freeze-drying, indicating advancing into in vitro toxicity testing. Vero and PC12 cells that were treated up to 72 h with various concentrations of L-DOPA and curcumin-loaded NP maintained high viability percentage, indicating that the NPs are biocompatible. Conclusions: NPs consisting of NH₂–PEO–PCL were characterized as potential formulations for brain delivery of L-DOPA and curcumin. The results also indicate that the developed biodegradable nanomicelles that were blood compatible presented low cytotoxicity.