Synthesis of Z-β-siloxyacrylonitriles and study of their dienophilic properties

A general method for the synthesis of Z-β-siloxyacrylonitriles from isoxazoles is reported. Their dienophilic activity is also described.     

Synthesis of β-cyclodextrin-lysozyme conjugates and their physicochemical and biochemical properties

Recently a great interest in the field of protein engineering and the design of innovative drug delivery systems employing specific ligands such as cyclodextrins is observed. The paper reports the solid state, thermal method for protein coupling with β-cyclodextrin and the physicochemical and biological properties of the obtained conjugates. The structure of the obtained conjugates was investigated via liquid chromatography-mass spectrometry, dynamic light scattering and circular dichroism analysis. The presented conjugates were biologically active and covalently bound β-cyclodextrin preserved the ability to form inclusion complexes with the model compound. This report demonstrates the great potential of cyclodextrin as a modifying unit that can be used to modulate the properties of therapeutic proteins, additionally giving such conjugates the possibility to transport many therapeutic substances in the form of inclusion complexes. In addition, the paper presents the potential of protein-cyclodextrin conjugates to construct innovative bioactive molecules for biological and medical applications.     

Effect of aqueous and ethanolic extracts from pinhão coats on the properties of corn and pinhão starches

Journal of Thermal Analysis and Calorimetry - The Araucaria angustifolia seed, named pinhão, has a high content of carbohydrates, and it is considered an unconventional starch source. Its...     

Synthesis and luminescence-spectral properties of benzoheterocyclic β-diketones and their complexes with europium

In order to solve some environmental and biomedical problems, we synthesized fluorinated heterocyclic β-diketones and estimated the luminescence-spectral properties of these compounds complexes with the ions of rare-earth elements as the possible reagents for immunofluorescence analysis.     

Preparation of nanoparticles and hollow spheres of ��-Fe2O3 and their properties

Uniform nanoparticles and hollow microspheres of hematite (??-Fe₂O₃) were obtained via a hydrothermal method by using iron (III) chloride as a precursor. The effects of reactant concentration, reaction time and temperature on the morphology of the samples were studied. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and superconducting quantum interference device magnetometer (SQUID) measurement. ??-Fe₂O₃ nanoparticles show a superparamagnetic behavior and the average size of the spherical particles was around 60 nm. However, hollow microspheres show a normal ferromagnetic behavior at room temperature with remanent magnetization and coercivity of 0.2482 emu/g and 2,516 Oe, respectively, and their average diameter was around 2 ??m. The effects of reactant concentration and reaction temperature on the formation of the products were investigated. The experimental results reveal that the magnetic properties of hematite can be tuned by controlling the morphology.     

Synthesis of conducting polyaniline—polyanion interpolymer complexes and study of their composition and properties

The polymerization of aniline in the presence of poly(4-styrenesulfonic acid) and poly(2-acryla-mido-2-methyl-1-propanesulfonic acid) results in interpolyelectrolyte complexes with a composition and a dispersion stability depending on the aniline-to-polyanion ratio in the initial reaction mixture. As opposed to polymerization mediated by poly(4-styrenesulfonic acid), the template polymerization of aniline conducted in the presence of poly(2-acrylamido-2-methyl-1-propanesulfonic acid) leads to the structural template effect that manifests itself as the formation of polyaniline containing 1,2- and 1,4-substituted benzene rings. It is found that the electron conductivity of the polyaniline-polyanion interpolyelectrolyte complexes depends not only on the content but also on the nature of the used polyacid and proves to be higher in the case of stoichiometric interpolyelectrolyte complexes formed in the presence of poly(4-styrenesulfonic acid).     

Fabrication of ZnO nanorods in ionic liquids and their photoluminescent properties

A novel and simple approach is reported to fabricate uniform single-crystal ZnO nanorods in ionic liq-uids. The as-obtained ZnO nanorods have been characterized by XRD,TEM,HRTEM,SAED,XPS,EDXA,PL and UV-vis absorption spectra. The rod diameters of the nanostructures can be controlled by tuning the amount of sodium hydroxide in the synthesis. Photoluminescence results show that the nanos-tructural ZnO exhibits better optical properties than bulk ZnO does and interestingly,the smaller the rod diameters are,the better optical property 1D nanostructural ZnO exhibits. The possible growth mechanism of ZnO nanorods is also investigated.     

Low-molecular-weight gelators based on Nα-acetyl-Nε-dodecyl-L-lysine and their amphiphilic gelation properties

A simple amphiphilic low-molecular-weight gelator based on L-lysine, N^α-acetyl-N^ε-lauroyl-L-lysine (1), its alkali metal salts [Na (2) and K (3)], and two-component gelators [1 and 2 and 1 and 3] were synthesized. Compound 1 had a good hydrogelation ability that formed a pure water gel at 2 g L^?1 (0.2 wt.%) and a saline gel at 4 g L^?1 (0.4 wt.%). Two-component compounds were able to form hydrogels in aqueous solutions containing alkali metal and alkali earth metal ions in addition to pure water and saline. Although 1 formed organogels in a few organic solvents, two-component compounds also functioned as a good organogelator. The FT-IR study indicated that the driving forces for the formation of supramolecular gels were hydrogen-bonding and hydrophobic interactions. Furthermore, the thermal properties of the hydrogels are discussed.     

Synthesis of α,ω-bis-1,5,3-dithiazepanes and their fungicidal properties

A procedure was developed for preparative synthesis of α,ω-bis-1,5,3-dithiazepanes by heterocyclization of aliphatic α,ω-diamines with N,N,N′,N′-tetramethylmethanediamine and 1,2-ethanedithiol. The fungicidal activity of 1,2-bis(1,5,3-dithiazepan-3-yl)ethane and 3,3′-(3,6-dioxaoctane-1,8-diyl)bis-1,5,3-dithiazepane toward microscopic fungi affecting agricultural plants was studied.     

Synthesis and photophysical properties of aryl-substituted 2-borylbenzaldimines and their extended π-conjugated congeners

Novel N-aryl-substituted 2-borylbenzaldimines 6 and related systems with extended π-framework 7 based on two borylbenzaldimine units linked by a spacer moiety were synthesized by condensation reactions of 2-(dimesitylboryl)benzaldehyde 3 with various amines 4 and diamines 5. All compounds were completely characterized including X-ray diffraction, especially in view of Lewis acid-base B-O and B-N interactions. The electronic as well as the photophysical properties of bisimines 7 were determined using cyclic voltammetry, UV/vis, and fluorescence spectroscopy and quantum chemistry. These compounds feature large Stokes shifts and reversible reduction waves. Interestingly, UV irradiation experiments unfold enhanced photostability for compounds 7 with an extended π-skeleton. By use of 1,8-diaminonaphthalene we observed the formation of a hitherto unknown BN-heterocyclic compound 9 fused with a perimidine skeleton. Structural and energetic aspects were evaluated by high level quantum chemical methods (DFT and SCS-MP2-calculations).     

Novel adamantane-bearing anilines and properties of their supramolecular complexes with β-cyclodextrin

Several novel anilines bearing 1-adamantyl substituents that are useful for drug modification were synthesised from the corresponding 1-adamantyl (nitrophenyl) ketones. The host–guest systems of these prepared ligands with β-cyclodextrin (β-CD) were studied using electrospray ionisation mass spectrometry, NMR spectroscopy, titration calorimetry and semi-empirical calculations. The complexes with 1:1 stoichiometry were found to predominantly exist as pseudorotaxane-like threaded structures with the adamantane cage sitting deep in the cavity of β-CD close to the wider rim. Such geometry was observed for all examined amines and is independent of their structure and/or presence of protic substituents.     

Solvent-dependent structures of lanthanide–TCNQ coordination networks and their magnetic properties

Abstract

Lanthanide complexes were prepared with 2,6-diacetylpyridinebis(benzoylhydrazone) (DAPBH₂) and 7,7,8,8-tetracyano-p-quinodimethanide (TCNQ^??). The complexes adopted one of two structure types depending on the reaction solvent. The complexes were categorized as Type I (i.e. bis{[2,6-diacetylpyridinebis(benzoylhydrazone)] methanollanthanide(III)}bis(µ₂- 7,7,8,8-tetracyanoquinodimethanide(1?))bis(7,7,8,8-tetracyanoquinodimethanide(1?))bis(7,7,8,8-tetracyanoquinodimethanide(1?)) methanol disolvate, [Ln₂(DAPBH₂)₂ (µ₂-TCNQ^??)₂(TCNQ^??)₂(MeOH)₂](TCNQ^??)₂·2MeOH (Ln?=?Gd, Tb, or Dy) or Type-II (i.e. [Ln₂(DAPBH₂)₂(µ₂-TCNQ^??)₂(TCNQ^??)₂(EtOH)₂] (TCNQ^??)₂·solvent (Ln?=?Tb and Dy, solvent =4EtOH for the Tb and 2EtOH·2CH₂Cl₂ for the Dy complexes). These two complexes exhibit dramatically different molecular structures and packings. In all complexes, the strong intra- and intermolecular stacking interactions of the TCNQ^?? radicals lead to the formation of 1D TCNQ chains. Magnetic susceptibility measurements for Type I and Type II complexes reveal that they exhibit paramagnetic behavior and that their magnetic properties originate from the lanthanide ions alone, owing to the diamagnetic nature of the TCNQ^?? stacks.     

Iron–sulfur clusters and their electronic and magnetic properties

Iron–sulfur clusters of diverse nuclearities constitute the active sites of a large and prominent family of metalloproteins which play essential roles in all living organisms, such as in electron transfer chains, reduction catalysis, photosynthesis, the respiratory chain and nitrogen fixation. This review is devoted to the presentation of the current state of understanding of their electronic and magnetic properties, which is here derived from their Mössbauer, EPR and ENDOR spectroscopic properties. These techniques constitute fine tools for characterization and provide knowledge of the different oxidation states of these proteins, although our interest here will be mainly centered on the [4Fe–4S*]ⁿ⁺ clusters (with n=1–3). A qualitative physical model involving the competing magnetic interactions in these clusters is discussed. Moreover, this article contains new developments on two more specialized subjects:

• 1.some quantitative consequences of an already published theory of the g-tensors of [4Fe–4S*]ⁿ⁺ clusters (n=1,3) will be derived in Section 3;
• 2.a model permitting the rationalization, from very simple ingredients and formulae, of the redox potentials of a whole set of known synthetic redox clusters (with 1, 2, 3, 4 and 6 iron atoms) will be presented in the final Section 6.

     

Conformational study of charged cyclohexyldiamines and their gas phase acid–base properties

Quantum chemical calculations employing the MP2/aug-cc-pVDZ model chemistry have been used to investigate the structure of mono- and diprotonated forms of cyclohexyldiamine (CHDA) isomers. The strength of the intramolecular hydrogen bonds and ion–dipole interactions between the amino groups, which play a key role in the conformational behaviour of the monoprotonated forms, is estimated by isodesmic reactions and electrostatic calculations. The energy variations found for the diprotonated forms are explained by the electrostatic repulsions between the amino groups. From the Gibbs energies and enthalpies calculated for the neutral and protonated CHDAs, the gas-phase basicities and proton affinities of the neutral and monoprotonated forms were determined and discussed.     

Synthesis of π-expanded BODIPYs and their fluorescent properties in the visible-near-infrared region

A series of π-expanded boron-dipyrromethenes (BODIPYs) fused with aromatic rings at β,β-positions, such as benzene, acenaphthylene, and benzofluoranthene were prepared by the reaction of BF₃·OEt₂ with bicyclo[2.2.2]octadiene-fused dipyrromethene and the subsequent retro Diels-Alder reaction. These BODIPYs exhibited the absorptions and the fluorescence emissions over wide range of visible-near-infrared region at 500-800 nm. BODIPYs composed of two fluorantho[8,9-f]isoindoles absorbed and emitted at red-region over 750 nm with absolute fluorescence quantum yield (Φ_f) of ca. 0.3, although they are unstable under air in room light. BODIPY composed fluorantho[8,9-f]isoindole and acenaphtho[1,2-c]pyrrole was stable and showed a bright fluorescence emission at 695 nm with high Φ_f of 0.70.     

Production of chiral matrices with hybrid silver–thiocholesterol nanosystems and study of their properties

A new type of chiral matrix based on silver–thiocholesterol hybrid nanosystems adsorbed on silica gel has been proposed. The molar ratio of stabilized thiocholesterol (L) ligand and silver (Ag) was found to have little effect on the size of the resulting silver nanoparticles (SNPs). The average diameter of SNPs was 2.7 ± 0.4, 2.2 ± 0.4, and 2.1 ± 0.6 nm upon the ratios Ag: L = 1: 5, Ag: L = 1: 2, and Ag: L = 1: 0.5, respectively. The resulting chiral matrices possess enantioselectivity relative to the 1,1’-binaphthyl-2,2’-diamine (BNDA) and trifluoroanthranyl ethanol (TFAE) optical isomers. The TFAE optical isomers were successfully separated using thin layer chromatography (α = 1.56).     

Electrical properties of σ-conjugated polymers with additives and their applications in sensors

The charge carrier transport in poly[methyl(phenyl)silylene] (PMPSi) proceeds predominantly along the σ-delocalized Si backbone with participation of interchain hopping and polaron formation. The charge carrier mobility increases with increasing electron affinity of acceptor dopands having zero dipole moments. On the other band, the hole drift mobility is influenced by the dipole moment of the dopand. The electrostatic charge-dipole interactions cause a broadening of the energy distribution of transport states, which results in a decrease in the charge carrier mobility. An addition of organic salts leads, under the conditions of increased humidity, to an increase in electrical conductivity and capacitance. This is demonstrated on the layers PMPSi/1,5-dimorpholino-1,5-diphenylpentamethinium perchlorate.