Design and synthesis of novel polycycles based on the 3H‐pyrrolo/6,7‐dihydropyrido[1,2‐a]indole scaffold as templates for pharmaceutical development

In the course of our work aimed at developing novel heterocycles of pharmaceutical interest, we designed and synthesized several polycyclic templates as potential substrates to be used in drug design. We obtained a set of condensed ring systems as versatile structural platforms to generate potential DNA‐interactive agents and/or reversible inhibitors of enzymes such as topoisomerases, poly(ADP‐ribose) polymerase‐1 (PARP‐1), telomerase, and, in particular, cyclin dependent kinases. Herein, we report the design, synthesis, structural investigation, and preliminary DNA‐binding affinity of these heteroaromatic systems. J. Heterocyclic Chem., (2011).     

Two‐photon microfabrication of poly(ethylene glycol) diacrylate and a novel biodegradable photopolymer—comparison of processability for biomedical applications

Two‐photon polymerization (2PP) is a versatile microfabrication tool for biomedical applications as it provides unparalleled resolution for accurate three‐dimensional (3D) replication of biological microstructures. To widen the selection of biomaterials suitable for 2PP, this paper presents the processing of a methacrylated poly(ε‐caprolactone)‐based oligomer (PCL‐o) and a poly(ethylene glycol) diacrylate (PEGda) hydrogel into microstructures. PCL‐o is a novel biodegradable photopolymer that has not been previously processed with 2PP, and the fabrication of both polymers with an Nd:YAG laser is reported here for the first time. The overall 2PP processability and achievable resolution were studied by polymerizing arbitrary microstructures on glass substrates. The samples were characterized with scanning electron microscopy. Additionally, the effect of photoinitiator concentration on the resolution was investigated. Also, a preliminary cell attachment test was performed with UV cured films in order to investigate the impact of the used material–initiator combination on cell viability and migration. As a result, laser‐induced polymerization of both PCL‐o and PEGda was successfully demonstrated, and the Nd:YAG laser was proven adequate for the 2PP processing of the novel biodegradable photoresist. Resolution in the order of 1 µm was achieved with PCL‐o. With the easy processing of both PEGda and PCL‐o, these materials have great potential for different biomedical applications. Copyright © 2011 John Wiley & Sons, Ltd.     

Polymer hydrogels of 2‐hydroxyethyl acrylate and acrylic acid obtained by frontal polymerization

In this work, we report on the synthesis and characterization of homopolymers and copolymers of acrylic acid and 2‐hydroxyethyl acrylate prepared by the use of the frontal polymerization (FP) technique. Tetraethyleneglycoldiacrylate was used as a crosslinker and benzoyl peroxide as an initiator. The maximum temperatures reached by the front were in the range between 214 °C and 296 °C. Besides, front velocities ranged between 3.9 and 10.8 cm/min, the latter being one of the highest values reported so far in the FP literature. Differential scanning calorimetry was used to estimate the conversion degree, which was always comprised between 90% and 96%, and to determine the glass transition temperatures, which were found to be dependent on the composition, with values ranging from 13 °C to 168 °C. Moreover, the obtained materials were allowed to swell in aqueous solutions at various pH. The samples exhibit a moderate increase of the swelling ratio percentage (SR%) at pH ≈ 5–6, and a sudden and larger SR% increase at pH ≈ 12–13 depending on the composition, thus indicating the obtainment of pH‐responsive polymer hydrogels. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Soft x-ray absorption and high-resolution powder x-ray diffraction study of superconducting CaxLa1−xBa1.75−xLa0.25+xCu3Oy system

We have studied the electronic structure of unoccupied states measured by O K-edge and Cu L-edge x-ray absorption spectroscopy (XAS), combined with crystal structure studied by high resolution powder x-ray diffraction (HRPXRD), of charge-compensated layered superconducting Ca_xLa_1−xBa_1.75−xLa_0.25+xCu₃O_y (0≤x≤0.4 and 6.4≤y≤7.3) cuprate. A detailed analysis shows that, apart from hole doping, chemical pressure on the electronically active CuO₂ plane due to the lattice mismatch with the spacer layers greatly influences the superconducting properties of this system. The results suggest chemical pressure to be the most plausible parameter to control the maximum critical temperatures (T_c^max) in different cuprate families at optimum hole density.     

Room-Temperature Oxidation of Secondary Alcohols by Bromate–Bromide Coupling in Acidic Water

Abstract

The use of environmentally benign reactions is currently an important topic in the field of synthetic chemistry. Here we report a high-yielding method to oxidize aliphatic or aromatic secondary alcohols into corresponding ketones using nonhazardous and inexpensive BrOH reagent at room temperature in water. BrOH reagent was derived from NaBr and NaBrO₃ in aqueous acid. Based on the presented results, a mechanism was proposed for this oxidation. The reported method offers a facile, efficient procedure to produce various ketones with a low amount of side products.     

Determination of mineral and trace element concentrations in pine needles by ICP-OES: evaluation of different sample pre-treatment methods

In the present study, the determination of mineral and trace elements (Al, B, Ca, Cu, Fe, K, Mg, Mn, Na, P and Zn) from pine needles using three sample pre-treatment methods followed by inductively coupled plasma optical emission spectrometry, was examined. Sample pre-treatment methods tested were microwave digestion, ultrasound-assisted digestion and dry ashing. The new ultrasound-assisted digestion method was optimised by the analysis of the standard reference material (SRM) 1575a (pine needles) sample. The speed of dry ashing method was significantly increased by ultrasound dissolution after ashing. All the ICP-OES measurements were performed in robust plasma conditions which were tested by measuring the Mg II 280.270 nm/Mg I 285.213 nm line intensity ratios. The microwave digestion resulted generally in slightly higher element concentrations than ultrasound-assisted digestion. B, Cu and Na resulted in such low concentrations that they could not be accurately determined by using the microwave digestion method. The t-tests found no significant differences between the certified and the determined element concentrations of the SRM 1575a using the dry ashing method followed with ultrasound dissolution.     

Bootstrap approximation for the exchange-correlation kernel of time-dependent density-functional theory

A new parameter-free approximation for the exchange-correlation kernel f(xc) of time-dependent density-functional theory is proposed. This kernel is expressed as an algorithm in which the exact Dyson equation for the response, as well as an approximate expression for f(xc) in terms of the dielectric function, are solved together self-consistently, leading to a simple parameter-free kernel. We apply this to the calculation of optical spectra for various small band gap (Ge, Si, GaAs, AlN, TiO(2), SiC), large band gap (C, LiF, Ar, Ne), and magnetic (NiO) insulators. The calculated spectra are in very good agreement with the experiment for this diverse set of materials, highlighting the universal applicability of the new kernel.     

Exact conditions in finite-temperature density-functional theory

Density-functional theory (DFT) for electrons at finite temperature is increasingly important in condensed matter and chemistry. The exact conditions that have proven crucial in constraining and constructing accurate approximations for ground-state DFT are generalized to finite temperature, including the adiabatic connection formula. We discuss consequences for functional construction.     

Activation of hafnocene catalyzed polymerization of 1-hexene with MAO and borate

A study of 1-hexene polymerization with ethylene-bis(9-fluorenyl) hafnium dichloride has been carried out using two different cocatalyst systems, methyl-aluminoxane/trimethylaluminum (MAO/TMA) and tris-isobutyl-aluminum/N,N-dimethylanilinium tetrakis(pentafluorophenyl) borate (TIBA/borate). When MAO/TMA was used, 1-hexene polymerized into a low molar mass poly(1-hexene) with low catalytic activity. Activation with TIBA/borate increased polymerization activity drastically as well as the molar mass of the polymers. In order to analyze differences in the activity profiles, UV-Vis spectroscopy was employed to investigate ligand to metal charge transitions (LMCT) of the hafnocene dichloride during the activation process. The low catalytic activity and the fast chain transfer to the cocatalyst with MAO/TMA may originate from strong bonding between the metallocene cation and the MAO/TMA species thus obstructing monomer coordination and insertion.