Novel Lipophilic Lanthanide Bis-Phthalocyanines Functionalized by Pentadecylphenoxy Groups: Synthesis, Characterization and UV-Photostability

Novel sandwich-type phthalocyanines containing a rare earth metal core (Pr, Nd, Eu-Lu) and macrocycles peripherally substituted by pentadecylphenoxy groups were synthesized using a cardanol-based phthalonitrile precursor and the respective lanthanide acetate. Additionally, the metal free-base analog compound was studied for comparison. The purified reaction products were all found to be thick and viscous substances at room temperature, showing liquid crystalline behavior with a distinct increase in fluidity at ca. 40 °C. The complexes are readily soluble in chloroalkyl solvents and dissolve fairly well in DMF with some tendency to form aggregates. Besides they are strongly hydrophobic and reveal a peculiar affinity for lipophilic media. The compounds have been characterized by UV-Vis (absorption and emission), FTIR, MS and DSC methods. Photochemical activity in the liquid phase (dimethylformamide, dichloromethane, mineral oil) and the degree of photodegradation demonstrated under constant UV-irradiation (λ = 352 nm) have been analyzed and discussed in terms of photostability.     

Kinetics of breakdown of vesicles from didodecyldimethylammonium bromide induced by single chain surfactants and by osmotic stress in aqueous solution

Didodecyldimethylammonium bromide (DDAB) forms vesicles spontaneously by simple solubilization of the solid into water at a concentration of ≈2.5 mM. Vesicles can be observed by the increase in turbidity of the aqueous solution of DDAB and by the increase in absorbance (at λ_max=490 nm) of a lipophilic dye (Sudan III) solubilized into the vesicular bilayer. This vesicle system has been perturbed by addition of single-chain surfactants in order to study the transition from a vesicle-stable region to a mixed-micelle region. Vesicle breakdown involves the initial incorporation of a single-chain surfactant into the vesicular bilayer, followed by subsequent disintegration of the vesicle. The progress of reaction has been observed by monitoring turbidity changes using a stopped-flow spectrophotometer. The rate of breakdown of vesicles depends on the concentration and hydrophobic properties of the added single-chain surfactant. In addition, hypertonic and hypotonic osmotic stresses have been investigated.     

Cardanol as a replacement for cholesterol into the lipid bilayer of POPC liposomes

Large unilamellar liposomes were prepared by hydration of 1-palmitoyl-2-oleylphosphatydilcholine (POPC) films and subsequent extrusion of the obtained liposomal suspension. Inclusion of cholesterol and cardanol brings about a stabilization of the membranes of the liposomes, as determined by their rates of release of entrapped 5(6)-carboxyfluorescein. The liposome breakdown was promoted by a non-ionic surfactant (Triton X-100) and the kinetic measurements were carried out by fluorimetry in water at 25 degrees C. Morphological analyses of giant POPC liposomes in the presence and in the absence of both guests were also performed. The results obtained suggest the use of cardanol (an easy available natural product) as a replacement for cholesterol as a new possibility for stabilizing liposomes in drug targetting.     

Parameterization of a coarse-grained model of cholesterol with point-dipole electrostatics

We present a new coarse-grained (CG) model of cholesterol (CHOL) for the electrostatic-based ELBA force field. A distinguishing feature of our CHOL model is that the electrostatics is modeled by an explicit point dipole which interacts through an ideal vacuum permittivity. The CHOL model parameters were optimized in a systematic fashion, reproducing the electrostatic and nonpolar partitioning free energies of CHOL in lipid/water mixtures predicted by full-detailed atomistic molecular dynamics simulations. The CHOL model has been validated by comparison to structural, dynamic and thermodynamic properties with experimental and atomistic simulation reference data. The simulation of binary DPPC/cholesterol mixtures covering the relevant biological content of CHOL in mammalian membranes is shown to correctly predict the main lipid behavior as observed experimentally.     

Update on selective oxidation using gold

This critical review aims to update the recent development in the selective oxidation of organic compounds by gold catalysis, highlighting the progress in the last three years. Following the impressive developments in the last decades, several protocols for catalytic oxidation are today available, which are based on the extraordinary properties of gold in terms of catalytic activity, selectivity, reusability and resistance to poisons. Beside many other applications, gold can be recommended for green processes dedicated to fine chemicals, pharmaceuticals and the food industry owing to its recognized bio-compatibility. The collected literature is focused on experiments concerning the oxidation of different chemical groups and could be of interest, in the wide area of organic chemistry, for improving previous processes or for exploring new catalytic pathways (174 references).     

$ \mathcal{Z} $ extremization in chiral-like Chern-Simons theories

Journal of High Energy Physics - We construct 1/4 BPS, threshold F-Dp bound states (with 0 ≤ p ≤ 5) of type II string theories by applying S- and T-dualities to...     

Particle size control in dendrimer-derived supported ruthenium catalysts

A high-resolution transmission electron microscopy (HRTEM) investigation of a family of supported Ru catalysts prepared from Ru hydroxyl-terminated poly(amidoamine) dendrimer-metal nanocomposite (DMN) precursors has been conducted. Ru particle sizes observed following deposition of DMNs on a HRTEM grid can be controlled within a 0.9-1.4 nm range depending on the metal-to-dendrimer molar ratio. The average particle size in this case correlates well with the theoretically predicted particle size from the molar loading of Ru in the dendrimer. Upon impregnation of Ru-DMNs on Al(2)O(3) and subsequent thermal removal of the dendrimer via reduction at 300 degrees C, significant sintering of the Ru particles was observed. Nevertheless, the resulting supported Ru particles maintained a narrow particle size distribution and average particle size below 2.5 nm. These particle sizes no longer correlate with the metal-to-dendrimer molar ratio but do correlate with the metal-to-dendrimer weight ratio, suggesting that the dendrimer may be acting as a "sintering-control" agent on the catalyst surface. This process is not affected by the surface area of the support, since almost identical particle size distributions were obtained on three different commercial supports.     

5-Methoxypropacin, a novel coumarinolignoid from Protium unifoliolatum

The novel coumarinolignoid 5-methoxypropacin was isolated from the ethereal extract of the wood of the Amazonian species Protium unifoliolatum. Its structure was elucidated by spectroscopic methods as IR, 1D and 2D (1)H, (13)C-NMR and mass spectrometry. The regioisomer and the position of coumarin and arylpropanoid coupling were determined by long-distance C-H correlation (HMBC) and NOE experiments. Scopoletin and beta-sitosterol were also isolated and identified by the same physical methods.     

Synthesis and photophysical properties of hyperbranched polyfluorenes containing 2,4,6-tris(thiophen-2-yl)-1,3,5-triazine as the core

A series of new hyperbranched polymers containing a 2,4,6-tris(thiophen-2-yl)-1,3,5-triazine core unit and polyfluorene chain arms have been synthesized via Suzuki coupling, and characterized by NMR, IR and GPC. All the polymers exhibit good thermal stability with a high decomposition temperature. By changing the 2,4,6-tris(thiophen-2-yl)-1,3,5-triazine/fluorene ratio the UV-vis absorption and emission spectra can be partially tuned. It has been found that the polymers containing a low ratio of 2,4,6-tris(thiophen-2-yl)-1,3,5-triazine units (P1-P3) have an absorption maximum around 385 nm, localized in the polyfluorene chain, and a shoulder around 425 nm ascribable to a charge transfer state involving the fluorene and the 2,4,6-tris(thiophen-2-yl)-1,3,5-triazine core. Increasing the molar ratio of the 2,4,6-tris(thiophen-2-yl)-1,3,5-triazine unit enhances the charge transfer band which becomes dominant for P4. The LUMO level of these polymers is relatively low due to the electron affinity of the triazine group. The polymers show dual emission, with a structured band in the blue (410-440 nm), attributed to the polyfluorene, and a broad band in the red (470-500 nm) associated with the charge transfer state. All the polymers exhibit two-photon absorption activity in the range of 660 to 900 nm with the maximum two-photon absorption (TPA) cross-section red-shifted from the corresponding linear absorption. The values of the TPA cross-sections vary from 1000 to 5000 GM, following the 2,4,6-tris(thiophen-2-yl)-1,3,5-triazine/fluorene ratio.