On the comparison of different tests for identification of a compound from its mass spectrum

It is shown that identification tests of different dimensions or dimensionless should not be evaluated (for their efficiency to identify molecules from their mass spectrum) by comparing the tests for a molecule itself (repeated measurements) with other molecules. This kind of tests must have similar dimensions (units). Another possibility is the comparison of tests on the basis of success of correct prediction for "unknown" molecules from a library of standards.     

Metallocorroles as Nonprecious‐Metal Catalysts for Oxygen Reduction

The future of affordable fuel cells strongly relies on the design of earth‐abundant (non‐platinum) catalysts for the electrochemical oxygen reduction reaction (ORR). However, the bottleneck in the overall process occurs therein. We have examined herein trivalent Mn, Fe, Co, Ni, and Cu complexes of β‐pyrrole‐brominated corrole as ORR catalysts. The adsorption of these complexes on a high‐surface‐area carbon powder (BP2000) created a unique composite material, used for electrochemical measurements in acidic aqueous solutions. These experiments disclosed a clear dependence of the catalytic activity on the metal center of the complexes, in the order of Co>Fe>Ni>Mn>Cu. The best catalytic performance was obtained for the Co^III corrole, whose onset potential was as positive as 0.81 V versus the reversible hydrogen electrode (RHE). Insight into the properties of these systems was gained by spectroscopic and computational characterization of the reduced and oxidized forms of the metallocorroles.     

Optochemical sensing by immobilizing fluorophore-encapsulating liposomes in sol–gel thin films

The chemical stability of optochemical sensors depends largely on the physiochemical properties of the supportive matrix of the sensor and on the method used to immobilize sensing reagents to the supportive matrix of the sensor. Leaking of physically immobilized sensing reagents from the matrix support decreases the stability of the sensor and its overall usefulness. Covalent immobilization eliminates leakage of the sensing reagent from the support but may lead to alteration of spectral properties and loss of analyte response. This paper presents a new method for physical immobilization of polar fluorescence dyes in a sensing support. The method is based on the immobilization of fluorescent dye encapsulating liposomes in a sol–gel film of micrometer thickness. The encapsulation of the dye molecules in the liposomes effectively increases the molecular dimensions of the sensing reagent, thus preventing its leakage from the matrix support. This paper describes the analytical properties of a pH sensor fabricated by immobilizing carboxyfluorescein-encapsulating liposomes in a sol–gel thin film. The sensor shows excellent stability with respect to dye leaking which in turn leads to high reproducibility and sensitivity of about 0.01 pH units. The linear dynamic range of the sensor is between pH 6 and 7.5 and its response time is at the sub-seconds time scale.     

Sulfur stable isotope distribution of polysulfide anions in an (NH4)2Sn aqueous solution

Methylation of polysulfides [(NH4)2Sn)] by reaction with CF3SO3CH3 followed by separation of the produced dimethylpolysulfides by liquid chromatography and subsequent highly accurate stable isotope analysis by a continuous-flow isotope ratio mass spectrometer shows that polysulfide anions in an aqueous solution exchange isotopes with the other sulfur species in the system. It demonstrates for the first time that polysulfide anions are 34S-enriched in equilibrium relative to total sulfur as a function of their sulfur chain length.     

Titanium and zirconium complexes of dianionic and trianionic amine-phenolate-type ligands in catalysis of lactide polymerization

The synthesis of alkoxotitanium(IV) and -zirconium(IV) complexes of seven chelating tetradentate di- or trianionic amine-phenolate ligands belonging to three families and their application in L-lactide polymerization are described. The isopropoxotitanium complexes were synthesized by a direct reaction between the ligand precursors and titanium tetraisopropoxide, whereas the zirconium complexes were synthesized by various routes. For titanium, complexes of all seven ligands could be synthesized. For zirconium, the hexacoordinate complexes derived from all dianionic ligands were synthesized; however, the only pentacoordinate complex that could be produced was the one derived from the bulky trianionic ligand. X-ray structures of zirconium complexes of the three families indicated a substantial pi donation from the alkoxo ligand to the metal. All complexes were found to be active lactide polymerization catalysts, and their activity was found to depend strongly on the metal, the coordination number around the metal, and the phenolate substituents but not on the ligand backbone.     

Mono-detection spatially super resolved microwave imaging for RADAR applications

In this paper we present a novel RF photonic approach to radar scanning and imaging. The operating principle is based upon a system in which several (in our case two) radiating microwave sources generate and project at far field, a moving grating pattern over an object, e.g. by linearly modifying the relative phase between the microwave sources. Capturing a set of such integrated reflections (we work only with a mono detector) coming from the object at different radio frequencies (due to a simultaneously performed spectral scanning) can spatially reconstruct high resolution image of the object despite the fact that the sensing was performed with a small mono receiving antenna.     

Assignment of aluminum corroles absorption bands to electronic transitions by femtosecond polarization resolved VIS-pump IR-probe spectroscopy

We combine femtosecond polarization resolved VIS-pump IR-probe spectroscopy with DFT and TD-DFT calculations to identify and assign absorption bands to electronic transitions for corroles. These macrocycles and their corresponding metal complexes are receiving great attention because of their utility in many fields, while many of their spectroscopic features have not yet been fully described. Analysis of the perturbed free induction decay provides information about the bleaching signal at time zero and allows for determination of overlapping excited state and bleaching signal amplitudes. The S(0) → S(1) and S(0) → S(2) transitions in the Q-band of the hexacoordinated Al(tpfc)(py)(2) and Br(8)Al(tpfc)(py)(2) absorption spectra are explicitly assigned. Angles between these electronic transition dipole moments (tdms) with a single vibrational transition dipole moment of (53 ± 2)° and (34 ± 2)° when excited at 580 and 620 nm for hexacoordinated Al(tpfc)(py)(2) and (51 ± 2)° and (43 ± 2)° when excited at 590 and 640 nm for hexacoordinated Br(8)Al(tpfc)(py)(2) were determined. The relative angles between the two lowest electronic tdms are (90 ± 8)° and (94 ± 3)° for Al(tpfc)(py)(2) and Br(8)Al(tpfc)(py)(2), respectively. Angles are determined before time zero by polarization resolved perturbed free induction decay and after time zero by polarization resolved transients. Comparison of corrole's wave functions with those of porphine show that the reduced symmetry in the corrole molecules results in lifting of Q-band degeneracy and major reorientation of the electronic transition dipole moments within the molecular scaffold. This information is necessary in designing optimal corrole-based electron and energy transfer complexes.