Metal Complexes and the Environment: Microscale Experiments with Iron-EDTA Chelates

The presence of ligands in natural and artificial environments is increasing. Science majors need exposure to experiments that deal with ligands and complexes in the environment. Two such experiments are presented here: The dissolution of a nonsoluble polluting gas (NO) by complex formation with [Iron(II)EDTA] and the decomposition of [Iron(III)EDTA] by exposure to light. The experiments involve the preparation of Iron-EDTA complexes, which are then used to demonstrate the positive and negative effects of ligands in the environment. These experiments are appropriate for applied inorganic chemistry or environmental chemistry laboratories. The first one takes approximately three hours to complete, and the second takes less than two hours.     

Application of Si and Al magic angle spinning nuclear magnetic resonance to studies of the building materials of historical monuments

We report the application of ²⁹Si and ²⁷Al magic angle spinning nuclear magnetic resonance (MAS NMR) studies on building stones from historical monuments to obtain direct information about the degree of degradation and to observe the changes in the consolidated material after treatment with tetraethoxysilane (TEOS). Using the data obtained from deteriorated materials, a diagnostic laboratory, a suitable treatment and recommendations for building conservation may infer. A case study is presented using stones from Guanajuato City Main Church (Central Mexico). X-ray diffraction patterns to characterize the species present in the stones agree with the solid state NMR results.     

Towards a loop representation for quantum canonical supergravity

We study several aspects of the canonical quantization of supergravity in terms of the Ashtekar variables. We cast the theory in terms of a GSU(2) connection and we introduce a loop representation. The solution space is similar to the loop representation of ordinary gravity, the main difference being the form of the Mandelstam identities. Physical states are in general given by knot invariants that are compatible with the GSU(2) Mandelstam identities. There is an explicit solution to all the quantum constraint equations connected with the Chern-Simons form, which coincides exactly with the Dubrovnik version of the Kauffman polynomial. This provides for the first time the possibility of finding explicit analytic expressions for the coefficients of that knot polynomial.     

Theoretical fluorescence yields and widths of the K shell and the L subshells,for the Ne,Ar, and Kr isoelectronic sequences

In this work, we present fluorescence yield and width values of Ne-, Ar-, and Kr-like ion levels for selected values of Z, using a state-of-the-art multiconfiguration Dirac–Fock approach. The results may be useful for the interpretation of spectra from plasmas, in both laboratory and astrophysics, as well as from ion collision experiments.     

Identification of the tension force in cables with insulators

Meccanica - The present paper explores two approaches which, based on the measurement of the two first natural frequencies, allow the identification of the tension force in cables with insulators....     

Synthesis and Characterization of m‐Terphenyl (1,3‐Diphenylbenzene) Compounds Containing Trifluoromethyl Groups

The bis(silyl)triazene compound 2,6‐(Me₃Si)₂‐4‐Me‐1‐(N?N? NC₄H₈)C₆H₂ ( 4 ) was synthesized by double lithiation/silylation of 2,6‐Br₂‐4‐Me‐1‐(N?N? NC₄H₈)C₆H₂ ( 1 ). Furthermore, 2,6‐bis[3,5‐(CF₃)₂‐C₆H₃]‐4‐Me‐C₆H₂‐1‐(N?N? NC₄H₈)C₆H₂ derivative 6 can be easily synthesized by a C,C‐bond formation reaction of 1 with the corresponding aryl‐Grignard reagent, i.e., 3,5‐bis[(trifluoromethyl)phenyl]magnesium bromide. Reactions of compound 4 with KI and 6 with I₂ afforded in good yields novel phenyl derivatives, 2,6‐(Me₃Si)₂‐4‐MeC₆H₂? I and 2,6‐bis[3,5‐(CF₃)₂? C₆H₃]‐4‐MeC₆H₂? I ( 5 and 7 , resp.). On the other hand, the analogous m‐terphenyl 1,3‐diphenylbenzene compound 2,6‐bis[3,5‐(CF₃)₂? C₆H₃]C₆H₃? I ( 8 ) could be obtained in moderate yield from the reaction of (2,6‐dichlorophenyl)lithium and 2 equiv. of aryl‐Grignard reagent, followed by the reaction with I₂. Different attempts to introduce the ^tBu (Me₃C) or neophyl (PhC(Me)₂CH₂) substituents in the central ring were unsuccessful. All the compounds were fully characterized by elemental analysis, melting point, IR and NMR spectroscopy. The structure of compound 6 was corroborated by single‐crystal X‐ray diffraction measurements.     

BODIPY Dye,the Most Versatile Fluorophore Ever?

BODIPY laser dyes constitute a fascinating topic of research in modern photochemistry due to the large variety of options its chromophore offers, which is ready available for a multitude of synthetic routes. Indeed, in the literature one can find a huge battery of compounds based on the indacene core. The possibility of modulating the spectroscopic properties or inducing new photophysical processes by the substitution pattern of the BODIPY dyes has boosted the number of scientific and technological applications for these fluorophores. Along the following lines, I will overview the main results achieved in our laboratory with BODIPYs oriented to optoelectronic as well to biophotonic applications, stressing the more relevant photophysical issues to be considered in the design of a tailor‐made BODIPY for a certain application and pointing out some of the remaining challenges.

     

Phytochemical Constituents and Ameliorative Effect of the Essential Oil from Annona muricata L. Leaves in a Murine Model of Breast Cancer

Annona muricata leaves are traditionally used as an anticancer plant in the world. The aim of this study was to evaluate the ameliorative effect of the essential oil from Annona muricata leaves (EOAm) in an experimental model of breast cancer and to determine the volatile constituents with gas chromatography-mass spectrometry (GC-MS). Thirty female rats were assigned to five groups: the control group; the DMBA (7,12-dimethylbenz[α]anthracene) group; and three groups received daily EOAm doses of 50, 100, and 200 mg/kg/day, plus DMBA, respectively. After 13 weeks of treatment, tumors were analyzed pathologically and biochemical markers in serum were noted. As a result, in GC-MS analysis, 40 compounds were identified and 4 of them were abundant: Z-caryophyllene (40.22%), followed by α-selinene (9.94%), β-pinene (8.92%), and β-elemene (7.48%). Furthermore, EOAm in a dose-dependent form produced a reduction in tumor frequency and the accumulated tumor volume was reduced by 50% and 71% with doses of 100 and 200 mg/kg, respectively. Serum levels of reduced glutathione (GSH) increased and malondialdehyde (MDA) decreased significantly compared to the DMBA group. Serum levels of vascular endothelial growth factor (VEGF) decreased significantly from 70.75 ± 7.15 pg/mL in the DMBA group to 46.50 ± 9.00 and 34.13 ± 11.50 pg/mL in groups treated with doses of 100 and 200 mg/kg, respectively. This study concludes that the EOAm leaves showed an ameliorative effect in a murine model of breast cancer.