A ruthenium(II)-trithiacyclononane curcuminate complex: Synthesis,characterization, DNA-interaction,and cytotoxic activity

The coordination of ruthenium(II) complexes to anionic oxygen-based donors are very rare. This study describes a simple, one-pot method for obtaining [ruthenium(II)(trithiacyclononane)(curcumin)(S-DMSO)]Cl (1) in 37% yield. The structural characterization of complex 1 by elemental analysis, FT-IR, 1-D and 2-D NMR, ESI⁺-MS as well as UV–vis and fluorescence spectroscopies are presented. The DNA-melting temperature (T_m) assay shows that salmon sperm DNA (smDNA) in the presence of complex 1 has a higher melting temperature, with ΔT_m = 7.4 °C, while in the presence of curcumin the melting temperature remains unaltered. The in vitro cytotoxic activities of curcumin and complex 1 were investigated using the tumor human prostate cell line, PC-3, and the healthy cell line, PNT-2. Complex 1 is innocuous toward normal prostate epithelial cells and, whereas curcumin is toxic, with inhibition rates of ca. 35 and 65% at 50 and 80 μM, respectively. On the tumor cell line PC-3, complex 1 did not cause viability changes, whereas curcumin exhibited dose-dependent inhibition, with ca. 73% inhibition at the highest concentration tested, i.e. 80 μM. This study suggests that coordination with the trithiacyclononane ruthenium(II) scaffold stabilizes the photochemical properties of curcumin and strongly changes its biologic activity.     

Sequential reactions from catalytic hydroformylation toward the synthesis of amino compounds

Different families of new amino compounds were efficiently synthesized, through optimized sequential processes, involving rhodium catalyzed hydroformylation as the key step. The selection of appropriate hydroformylation catalytic systems and reaction conditions allowed obtaining aldehydes derived from several n-alkyl olefins, cholest-4-ene and 3-vinyl-1H-indole, which were subsequently transformed, in one-pot, in to α-amino acids via hydroformylation/Strecker reaction, and in to tertiary amines via hydroaminomethylation, with excellent yields.     

Crystallization behavior and electroactive properties of PVDF,P(VDF-TrFE) and their blend films

PVDF, poly(vinylidene fluoride), as a semi-crystalline polymer, has interesting electroactive properties but usual melt and solution processing techniques result in its thermodynamically favored non-polar α-phase. By comparison, poly(vinylidene fluoride-trifluoroethylene) P(VDF-TrFE), PT for short, directly crystallizes in the polar β-phase under the same conditions as PVDF. In this study, blend thin films comprising PVDF and P(VDF-TrFE) were prepared by solvent casting method. The difference in the crystallization behavior is comprehensively investigated between the polymers: PVDF, P(VDF-TrFE), and the resulting blend films. It is found that replacement of the fluoride atom in TrFE monomer induces a strong steric hindrance that may alter the crystallization process to become more favorable for nucleation of the PVDF β-phase. To figure out the effect of TrFE content on the crystallization behavior and electroactive properties, films with different blend ratios of PVDF and P(VDF-TrFE) were prepared. We found that the PVDF films exhibit higher crystallization activation energy (ΔE) as PT content increases. The atomic force microscopy (AFM) in the piezoresponse force microscopy (PFM) mode illustrated that P5T5 films with equal contents of PVDF and P(VDF-TrFE) induced the highest d₃₃ values.     

Molecular fluorescence analysis of rainwater: Effects of sample preservation

Very different filtration and preservation procedures may be found in the literature on the study of the rainwater dissolved organic fraction. Thus, the influence of sample filtration and preservation procedures on the fluorescence of rainwater dissolved organic matter (DOM) was studied in this work. Rainwater was filtered through different filters (quartz 0.22 μm or PVDF 0.45 μm) and excitation (λ_em = 415 nm) and synchronous (Δλ = 70 nm) fluorescence spectra were obtained at the same day of collection, or after preservation by refrigeration (1-7 days) or by freezing (1-4 weeks). The excitation-emission matrix (EEM) spectra of rainwater showed six types of fluorescent bands: two corresponding to humic-like bands, and four resembling proteins. Then, the excitation and synchronous spectra were chosen in order to monitor changes in the humic-like and protein-like bands, respectively. The filtration procedures adopted in this work did not affect the fluorescence properties of the rainwater samples. However, these properties were differently preserved by refrigeration or freezing: after refrigeration, filtered rainwater maintained the original fluorescent properties for at least 4 days, while after freezing fluorescent properties were not always preserved since it occurred a decrease of protein-like fluorescence intensity.     

Microwave-assisted synthesis of 3-hydroxy-4-pyridinone/naphthalene conjugates. Structural characterization and selection of a fluorescent ion sensor

Two novel 3-hydroxy-4-pyridinone/naphthalene conjugates (L1 and L2) with different distances between the chelating and the fluorescent moieties were synthesized using conventional heating and microwave irradiation achieving a shorter reaction time. The structure of both compounds was confirmed by X-ray crystallography, revealing that these compounds were isolated as hydrochloride salts in dihydroxypyridinium forms. In solution and in the presence of a base, the tautomeric keto forms may be obtained as it was elucidated by NMR analysis. The dihydroxypyridinium form of L1 exhibits fluorescence at 450 nm, both in ACN and DMSO, whereas the corresponding keto form exhibits fluorescence at 365 nm. In contrast, the dihydroxypyridinium form of L2 only fluoresces in DMSO, exhibiting a band at 340 nm, while the keto form is non-fluorescent. These distinct fluorescent behaviors reveal that the tautomeric form in which the ligands are isolated and the distance between the chelating and fluorescent functions strongly influences their fluorescence properties. Ligand L1 exhibits better fluorescence properties and its fluorescence intensity is quenched in the presence of variable concentration of Cu²⁺, Zn²⁺, and Fe³⁺, thus making it suitable to be used as ion sensor.     

How light affects 5,10,15-tris(pentafluorophenyl)corrole

5,10,15-Tris(pentafluorophenyl)corrole slowly undergoes oligomerization when left in solution at room temperature, under air and ambient light. This transformation was studied in different solvents (chloroform, dichloromethane, and toluene) and the main resulting products were identified as the 3,3′-corrole dimer 2a and the 3,3′,17′,3′′-corrole trimer 3a.     

Rigid ferrocenophane and its metal complexes with transition and alkaline-earth metal ions

The rigid [6]ferrocenophane, L¹, was synthesised by condensation of 1,1′-ferrocene dicarbaldehyde with trans-1,2-diaminocyclohexane in high dilution at r.t. followed by reduction. When other experimental conditions were employed, the [6,6,6]ferrocenephane (L²) was also obtained. Both compounds were characterised by single crystal X-ray crystallography. The protonation of L¹ and its metal complexation were evaluated by the effect on the electron-transfer process of the ferrocene (fc) unit of L¹ using cyclic voltammetry (CV) and square wave voltammetry (SWV) in anhydrous CH₃CN solution and in 0.1 M ⁿBu₄NPF₆ as the supporting electrolyte. The electrochemical process of L¹ between −300 and 900 mV is complicated by amine oxidation. On the other hand, an anodic shift from the fc/fc⁺ wave of L¹ of 249, 225, 81 and 61 mV was observed by formation of Zn²⁺, Ni²⁺, Pd²⁺ and Cu²⁺ complexes, respectively. Whereas Mg²⁺ and Ca²⁺ only have with L¹ weak interactions and they promote the acid-base equilibrium of L¹. This reveals that L¹ is an interesting molecular redox sensor for detection of Zn²⁺ and Ni²⁺, although the kinetics of the Zn²⁺ complex formation is much faster than that of the Ni²⁺ one. The X-ray crystal structure of [PdL¹Cl₂] was determined and showed a square–planar environment with Pd(II) and Fe(II) centres separated by 3.781(1) Å. The experimental anodic shifts were elucidated by DFT calculations on the [ML¹Cl₂] series and they are related to the nature of the HOMO of these complexes and a four-electron, two-orbital interaction.     

OH-radical induced degradation of hydroxybenzoic- and hydroxycinnamic acids and formation of aromatic products—A gamma radiolysis study

The OH-radical induced degradation of hydroxybenzoic acids (HBA), hydroxycinnamic acids (HCiA) and methoxylated derivatives, as well as of chlorogenic acid and rosmarinic acid was studied by gamma radiolysis in aerated aqueous solutions. Primary aromatic products resulting from an OH-radical attachment to the ring (hydroxylation), to the position occupied by the methoxyl group (replacement –OCH₃ by ?OH) as well as to the propenoic acid side chain of the cinnamic acids (benzaldehyde formations) were analysed by HPLC–UV and LC–ESI–MS. A comparison of the extent of these processes is given for 3,4-dihydroxybenzoic acid, vanillic acid, isovanillic acid, syringic acid, cinnamic acid, 4-hydroxycinnamic acid, caffeic acid, ferulic acid, isoferulic acid, chlorogenic acid, and rosmarinic acid. For all cinnamic acids and derivatives benzaldehydes were significant oxidation products. With the release of caffeic acid from chlorogenic acid the cleavage of a phenolic glycoside could be demonstrated. Reaction mechanisms are discussed.     

Fiber-optic curvature sensor with optimized sensitive zone

A novel fiber-optic sensor that can measure curvature directly has been developed previously. In this paper, the transduction of curvature to light intensity is described analytically by using the geometrical optics analysis. The mathematical model allows a quantitative optimization of the sensor without having to produce many sensors with slightly different combinations of parameters in order to accomplish a similar objective experimentally. The Monte Carlo simulation by ray tracing and an orthogonal matrix are used to optimize the fiber-optic sensor’s configuration. The results show that the depth of the sensitive zone and the number of teeth are two main parameters that affect the sensor’s sensitivity and the optimum number of teeth is 55, which is in agreement with the mathematical model.     

PTCR effect in carbon black/copolymer composites

Some materials show an abrupt increase in resistivity when the temperature changes only over a few degrees. This phenomenon, known as PTCR effect (positive temperature coefficient of resistivity), has been largely studied in the last few years, due to its potential applications in industry. Particularly, it can be used in auto controlled heaters, temperature sensors, protection circuits and in security systems for power electronic circuits.In this work we present the study of the electrical properties of the percolating system carbon black particles filled with ethylene butylacrylate copolymer composite (EBA), in the temperature range from −100 to 100 °C and in frequencies between 10 Hz and 100 kHz. The PTCR effect was observed at temperatures slightly above the room temperature, for concentrations higher than that of the percolation critical concentration.The mechanism responsible for the change in resistivity, at this stage, is predominantly tunnelling, wherein the conductive filler particles are not in physical contact, and the electrons tunnel through the insulating gap between them. At low temperatures, such as below and close to the glass transition temperature, the DC conductivity obeys the Arrhenius law. The calculated activation energy values are independent of carbon black contents inside the copolymer matrix, suggesting that these particles do not interact significantly with the chain segments of the macromolecules in the EBA copolymer.