Cation coordination induced modulation of the anion sensing properties of a ferrocene-imidazophenanthroline dyad: multichannel recognition from phosphate-related to chloride anions

A new chemosensor molecule 1 based on a ferrocene-imidazophenanthroline dyad, effectively recognizes aqueous hydrogenpyrophosphate and the organic anions ADP and ATP through three different channels. A cathodic shift of the ferrocene/ferrocenium oxidation wave (Delta E 1/2 ranging from -130 mV for hydrogenpyrophosphate and fluoride to -40 mV for ADP). A progressive red-shift of the absorption bands and/or appearance of a new low energy band at 314-319 nm. These changes in the absorption spectra are accompanied by color changes from pale yellow to orange or pink, which allow the potential for "naked eye" detection. The emission spectrum (lambda exc = 390 nm) undergoes an important chelation-enhanced fluorescence effect (CHEF = 50) in the presence of 2.5 equiv of hydrogenpyrophosphate anion and with a large excess of fluoride anion (CHEF = 114). Interestingly, the emission spectrum obtained at different excitation energy (lambda exc = 340 nm) in the presence of AcOH acid is red-shifted and not only perturbed by the hydrogenpyrophosphate anion (CHEF = 71) but also with the organic anions ATP (CHEF = 25), ADP (CHEF = 15), and the dihydrogenphosphate (CHEF = 25). The stable heterobimetallic ruthenium (II) complex 2 selectively senses the chloride anion over other anions examined through two channels: cathodic redox shift (Delta E 1/2 = -80 mV) of the Fe(II)/Fe(III) redox couple keeping the oxidation wave of the ruthenium (II) center unchanged and a significant red emission enhancement (CHEF = 30). (1)H and (31)P NMR studies as well as DFT calculations have been carried out to get information about which molecular sites are involved in bonding. About the deprotonation/coordination dualism, the combined electrochemical, absorption, emission, and NMR data strongly support that fluoride anion induces only deprotonation, anions dihydrogenphosphate, ATP, and ADP from hydrogen-bonded complexes and formation of hydrogen-bonded complex between receptor 1 and hydrogenpyrophosphate anion and deprotonation proceed simultaneously. In regards to receptor 2, all available data (electrochemical, absorption, emission, and 1H NMR) strongly support the formation of a [2. Cl ( - ) ] hydrogen-bonded complex.     

Study of the reactions π− p→K 0 Λ and π− p→K 0Σ0 at 3.95 GeV/c

The reactions π^? p→K ⁰ Λ,K ⁰Σ⁰ are studied at an incident momentum of 3.95 GeV/c using data from a high statistics bubble chamber experiment corresponding to ～90 events/μb. The differential cross sections and hyperon polarizations are presented and compared with existing data from earlier electronic experiments. The data in the forward hemisphere are used to perform an amplitude analysis of the 0^?1/2⁺→0^?1/2⁺ hypercharge exchange processes.     

Necessary Optimality Conditions for Interval Optimization Problems with Functional and Abstract Constraints

Journal of Optimization Theory and Applications - This work addresses interval optimization problems in which the objective function is interval-valued while the constraints are given in functional...     

Correction of structured molecular background by means of high-resolution continuum source electrothermal atomic absorption spectrometry—Determination of antimony in sediment reference materials using direct solid sampling

A simple, fast and accurate procedure is proposed for the determination of antimony in certified sediment reference materials using direct solid sampling high-resolution continuum source electrothermal atomic absorption spectrometry and iridium as a permanent modifier. The less sensitive resonance line at 231.147 nm has been used in order to allow the introduction of larger sample mass. Six certified reference materials, one river, one estuarine and four marine sediments have been analyzed. The use of iridium as a permanent modifier caused an increase of 30% in sensitivity and stabilized antimony in the sediment to a pyrolysis temperature of 1100 °C. Significant background absorption with pronounced rotational fine structure was observed at the optimum atomization temperature of 2100 °C, which coincided with the analyte atomic absorption in time. This background was found to be due to the electron excitation spectra of mostly the SiO and in part the PO molecules, and could be eliminated by applying a least-squares background correction algorithm. A characteristic mass of 28 pg Sb was obtained, and the limit of detection (3σ, n = 10) was 0.02 μg g⁻¹, calculated for 0.2 mg of sample. The results obtained for six certified reference materials with concentrations between 0.40 and 11.6 ± 2.6 μg g⁻¹ Sb were in agreement with the certified values according to a Student's t-test for a 95% confidence level, using aqueous standards for calibration. The precision, expressed as relative standard deviation, ranged between 7% and 17% (n = 5).     

Simultaneous determination of Cd and Fe in sewage sludge by high-resolution continuum source electrothermal atomic absorption spectrometry with slurry sampling

This work describes the method development for the simultaneous determination of Cd and Fe using the main resonance line of Cd at 228.802 nm and a secondary Fe line at 228.725 nm, and high-resolution continuum source electrothermal atomic absorption spectrometry (HR-CS ET AAS). Two certified reference materials and two ‘real’ samples of industrial and domestic sewage sludge have been analyzed as slurries prepared in a mixture of HF and HNO₃. The simultaneous determination has been performed using a short temperature program of only 30 s, without a pyrolysis stage and with two atomization stages, at 1300 °C and 2300 °C, taking into consideration the significantly different thermal characteristics of Cd and Fe. Structured background, which is likely due to the presence of one or more diatomic molecules, including SiO, has been detected. However, there has been no spectral overlap between molecular bands and the atomic lines of Cd and Fe, making possible the determination to be carried out using only automatic correction for continuous background. Calibration against aqueous standards lead to good agreement between certified or informed values and the determined values, at a statistical confidence level of 95%; recovery tests were performed for real samples, resulting in recoveries ranging from 90 to 105%. Detection limits of 0.03 and 90 µg g^{− 1} for Cd and Fe, respectively, have been obtained, which are adequate for the purpose.     

Synthesis of 4-azepanones and heteroaromatic-fused azepines

Two syntheses of versatile intermediate azepinones 2 and 3 are described. A 6-step intramolecular Dieckmann cyclization and decarboxylation led to the intermediate 3 while an alternate 4-step synthesis of 2 was developed and used for scale-up. The highlight of the second synthesis is the one-step per-bromination/elimination protocol from readily available azepinone 13a to provide a versatile scaffold in vinyl bromide 5, which enables SAR around the aryl moiety. An example of the elaboration of the intermediate 2 toward a heteroaryl azepinone is also described.     

A water soluble macromolecular nanobox having porphyrinic walls as a large host for giant guests

Cyclic tetra{5,15‐di‐[p(ω‐methoxypolyethyleneoxy)phenyl]‐10,20‐[p‐oxyphenyl] methylen porphyrin}, cy‐[O‐(H₂‐PTPEG₂)‐O‐CH₂‐]₄ , a water soluble macromolecule consisting of four porphyrin units [each with two long ω‐methoxypolyethyleneoxy (PEG) branches bound on its peripheral positions] linked by means of four methylenoxy bridges, was prepared by an interfacial etherification reaction. Structural and spectroscopic characterization of cy‐[O‐(H₂‐PTPEG₂)‐O‐CH₂‐]₄ and of its cobalt‐derivative {cy‐[O‐(Co‐PTPEG₂)‐O‐CH₂‐]₄} was performed by means of MALDI‐TOF mass spectrometry, NMR, UV–vis, and circular dichroism spectroscopy. The data obtained from the cy‐[O‐(Co‐PTPEG₂)‐O‐CH₂‐]₄/Gramicidin‐S mixture showed that some evident spectral changes were compatible with the formation of a supramolecular structure between the porphyrinic nanobox and the Gramicidin S (a polypeptide having a relevant pharmacological importance). These preliminary data highlight how cy‐[O‐(H₂‐PTPEG₂)‐O‐CH₂‐]₄ and/or its metalled derivatives, for their both chemical composition and structural arrangement, have promising properties for applications as a drug carrier in aqueous media. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013