Photochemical behavior of some substituted benzophenoxazinones

Irradiation of some substituted benzophenoxazinones in methanol solution by visible light yields dimerization and substitution products. A possible radical mechanism is proposed and validated by quantum mechanical computations.     

Compositional Study and Antioxidant Potential of <em>Ipomoea hederacea</em> Jacq. and <em>Lepidium sativum</em> L. Seeds

The present investigation has been carried out to determine the proximate composition, amino acids, metal contents, oil composition as well as the antioxidant capacity of the seeds of Ipomoea hederacea Jacq. and Lepidium sativum L. Proximate composition indicated a great difference in oil (14.09 ± 0.66, 28.03 ± 1.05) and fibre (16.55 ± 0.31, 6.75 ± 1.20) contents for I. hederacea and L. sativum, respectively. Fatty acid profile indicated that oleic acid (19.50 ± 0.37, 30.50 ± 0.16) and linoleic acid (52.09 ± 0.48, 8.60 ± 0.38) are the major fatty acids. γ-Tocopherol and d-tocopherol (28.70 ± 0.14, 111.56 ± 0.37) were the most abundant in the seed oil of I. hederacea and L. sativum, respectively. Results of TEAC, FRAP and TRAP antioxidant assays indicated that L. sativum has much greater antioxidant potential than I. hederacea.     

Open-shell localized Hartree-Fock method based on the generalized adiabatic connection Kohn-Sham formalism for a self-consistent treatment of excited states

An effective exact-exchange Kohn-Sham approach for the treatment of excited electronic states, the generalized adiabatic connection open-shell localized Hartree-Fock (GAC-OSLHF) method is presented. The GAC-OSLHF method is based on the generalized adiabatic connection Kohn-Sham formalism and therefore capable of treating excited electronic states, which are not the energetically lowest of their symmetry. The method is self-interaction free and allows for a fully self-consistent computation of excited valence as well as Rydberg states. Results for atoms and small- and medium-size molecules are presented and compared to restricted open-shell Hartree-Fock (ROHF) and time-dependent density-functional results as well as to experimental data. While GAC-OSLHF and ROHF results are quite close to each other, the GAC-OSLHF method shows a much better convergence behavior. Moreover, the GAC-OSLHF method as a Kohn-Sham method, in contrast to the ROHF approach, represents a framework which allows also for a treatment of correlation besides an exchange by appropriate functionals. In contrast to the common time-dependent density-functional methods, the GAC-OSLHF approach is capable of treating doubly or multiply excited states and can be easily applied to molecules with an open-shell ground state. On the nodal planes of the energetically highest occupied orbital, the local multiplicative GAC-OSLHF exchange potential asymptotically approaches a different, i.e., nonzero, value than in other regions, an asymptotic behavior which is known from exact Kohn-Sham exchange potentials of ground states of molecules.     

Screening for exogenous androgen anabolic steroids in human hair by liquid chromatography/orbitrap-high resolution mass spectrometry

A method for the screening of various anabolic steroids and their esters in human hair, based on liquid-chromatography–high resolution mass spectrometry using an Exactive benchtop Orbitrap mass spectrometer, has been set up and validated. This method involved methanolic incubation of 30 mg of hair and analysis of the relevant extract in HPLC using a C18 column. The mass detector, with nominal resolving power of 100,000, operated in full scan mode in APCI under positive ionization mode. Analytes were identified by exact mass, correspondence of isotopic cluster and retention times.     

FT-IR and FT-FIR studies of vanadium,molybdenum and tungsten oxides supported on different carriers

In the far IR region at low molybdenum loadings, Mo-SiO₂ catalysts present a pseudomolybdate or a polymolybdate species, while bulk-like MoO₃ appears at loadings close to the geometrical monolayer coverage. W-SiO₂ and V-SiO₂ spectra show bands close to those observed on the corresponding bulk oxides.In the case of TiO₂, Al₂O₃, ZrO₂ supported catalysts, a band is observed near 1000 cm^–1 which is assigned to the Mo=O stretching vibration of coordinatively unsaturated Mo ⁿ⁺ ions showing a stronger interaction with the support than one observed on silica.     

Interactions between cyclodextrins and fluorescent T-2 and HT-2 toxin derivatives: a physico-chemical study

T-2 and HT-2 toxins are mycotoxins produced by several Fusarium species that are commonly found in various cereal grains, including oats, barley, wheat and maize. Intake estimates indicate that the presence of these mycotoxins in the diet can be of concern for public health. In this work, the inclusion processes occurring between fluorescent anthracene-derivatives of T-2 and HT-2 toxins and different cyclodextrin (CD) molecules were investigated in aqueous solutions by means of UV–Vis absorption, fluorescence emission and dynamic light scattering. Binding constant values and chemico-physical parameters were calculated. It was found that β-CDs give stronger inclusion reactions with both T-2 and HT-2 derivatives, as stated by important emission intensity increments. Such interactions were found to be fundamentally enthalpy-driven. Among β-CDs, the effect of the methylation at hydroxyl groups was tested: as a result, the di-methyl form of β-CD was found to induce the best fluorescence intensity enhancements.     

Optical manipulation of charged microparticles in polar fluids

In this study, we report a systematic study of the response of a charged microparticle confined in an optical trap and driven by electric fields. The particle is embedded in a polar fluid, hence, the role of ions and counterions forming a double layer around the electrodes and the particle surface itself has been taken into account. We analyze two different cases: (i) electrodes energized by a step‐wise voltage (DC mode) and (ii) electrodes driven by a sinusoidal voltage (AC mode). The experimental outcomes are analyzed in terms of a model that combines the electric response of the electrolytic cell and the motion of the trapped particle. In particular, for the DC mode we analyze the transient particle motion and correlate it with the electric current flowing in the cell. For the AC mode, the stochastic and deterministic motion of the trapped particle is analyzed either in the frequency domain (power spectral density, PSD) or in the time domain (autocorrelation function). Moreover, we will show how these different approaches (DC and AC modes) allow us, assuming predictable the applied electric field (here generated by plane parallel electrodes), to provide accurate estimation (3%) of the net charge carried by the microparticle. Vice versa, we also demonstrate how, once predetermined the charge, the trapped particle acts as a sensitive probe to reveal locally electric fields generated by arbitrary electrode geometries (in this work, wire‐tip geometry).     

Ferrocene-containing carbohydrate dendrimers

Aliphatic amines, incorporating one or three (branched) acylated beta-D-glucopyranosyl residues, were coupled with the acid chloride of ferrocenecarboxylic acid and with the diacid chloride of 1,1'-ferrocenedicarboxylic acid to afford four dendrimer-type, carbohydrate-coated ferrocene derivatives in good yields (54-92%). Deprotection of the peracylated beta-D-glucopyranosyl residues was achieved quantitatively by using Zemplén conditions, affording four water-soluble ferrocene derivatives. When only one of the two cyclopentadienyl rings of the ferrocene unit is substituted, strong complexes are formed with beta-cyclodextrin in H2O, as demonstrated by liquid secondary ion mass spectrometry (LSIMS), 1H NMR spectroscopy, electrochemical measurements, and circular dichroism spectroscopy. Molecular dynamics calculations showed that the unsubstituted cyclopentadienyl ring is inserted through the cavity of the toroidal host in these complexes. The electrochemical behavior of the protected and deprotected ferrocene-containing dendrimers was investigated in acetonitrile and water, respectively. The diffusion coefficient decreases with increasing molecular weight of the compound. The potential for oxidation of the ferrocene core, the rate constant of heterogeneous electron transfer, and the rate constant for the energy-transfer reaction with the luminescent excited state of the [Ru(bpy)3]2+ complex (bpy = 2,2'-bipyridine) are strongly affected by the number (one or two) of substituents and by the number (one or three) of carbohydrate branches present in the substituents. These effects are assigned to shielding of the ferrocene core by the dendritic branches. Electrochemical evidence for the existence of different conformers for one of the dendrimers in aqueous solution was obtained.     

Crystalline phase orientation in biaxially stretched isotactic polypropylene films

The different kinds of crystalline orientations which can occur in industrially relevant isotactic polypropylene (i-PP) films are compared with those generally observed for other semicrystalline polymers. The peculiar bimodality typical of the uniplanar-axial orientation which is present in two-step biaxially stretched i-PP films is rationalized in terms of the two alternative stackings on the (0k0) face of bilayers of macromolecules of the monoclinic unit cell.     

Simultaneous separation of different enantiomeric pairs in capillary electrophoresis by mixing different hemispherodextrins,a very versatile class of receptors

Six different racemates of the profen family were used as analytes in order to test the chiral selector properties of three members of a new class of cyclodextrin derivatives, hemispherodextrins (HMs), in capillary electrophoresis. In addition to experiments carried out to separate each enantiomeric pair one by one, other experiments were carried out on samples containing all six enantiomeric pairs. Electropherograms were obtained either by adding a single HM to the background electrolyte (BGE), or a binary mixture of HMs. The results obtained confirm the excellent chiral selector properties of the HMs, and furthermore show that these compounds can also be used for achiral selection. When mixing different HMs, a complementary effect in chiral selectivity is observed, which, in our opinion, deserves further study.