Radical–anion coupling through reagent design: hydroxylation of aryl halides

The design and development of an oxime-based hydroxylation reagent, which can chemoselectively convert aryl halides (X = F, Cl, Br, I) into phenols under operationally simple, transition-metal-free conditions is described. Key to the success of this approach was the identification of a reducing oxime anion which can interact and couple with open-shell aryl radicals. Experimental and computational studies support the proposed radical-nucleophilic substitution chain mechanism.

The design and development of an oxime-based hydroxylation reagent, which can chemoselectively convert aryl halides (X = F, Cl, Br, I) into phenols under operationally simple, transition-metal-free conditions is described.     

An Insight into Kiwiberry Leaf Valorization: Phenolic Composition,Bioactivity and Health Benefits

During kiwiberry production, different by-products are generated, including leaves that are removed to increase the fruit’s solar exposure. The aim of this work was to extract bioactive compounds from kiwiberry leaf by employing microwave-assisted extraction (MAE). Compatible food solvents (water and ethanol) were employed. The alcoholic extract contained the highest phenolic and flavonoid contents (629.48 mg of gallic acid equivalents (GAE) per gram of plant material on dry weight (dw) (GAE/g dw) and 136.81 mg of catechin equivalents per gram of plant material on dw (CAE/g dw), respectively). Oppositely, the hydroalcoholic extract achieved the highest antioxidant activity and scavenging activity against reactive oxygen and nitrogen species (IC₅₀ = 29.10 μg/mL for O₂^•−, IC₅₀ = 1.87 μg/mL for HOCl and IC₅₀ = 1.18 μg/mL for ^•NO). The phenolic profile showed the presence of caffeoylquinic acids, proanthocyanidin, and quercetin in all samples. However, caffeoylquinic acids and quercetin were detected in higher amounts in the alcoholic extract, while proanthocyanidins were prevalent in the hydroalcoholic extract. No adverse effects were observed on Caco-2 viability, while the highest concentration (1000 µg/mL) of hydroalcoholic and alcoholic extracts conducted to a decrease of HT29-MTX viability. These results highlight the MAE potentialities to extract bioactive compounds from kiwiberry leaf.     

Near-infrared spectrophotometric determination of compositions of fullerene samples

A novel method has been developed for the sensitive and accurate determination of compositions of fullerene samples. The method is based on the synergistic use of spectrophotometric measurements and partial least square method. The method is not only simple, inexpensive and fast but also is non-destructive. Compositions of various fullerene samples including fullerite which is the precursor to C(60) and C(70), can be directly and non-destructively determined by this method without any time-consuming separation step as in the HPLC method or destruction as in the MS method.     

Synthesis and anion binding properties of 2,5-diamidothiophene polypyrrole Schiff base macrocycles

[reaction: see text] Two easy-to-synthesize polypyrrolic 2,5-diamidothiophene Schiff base macrocycles are reported, along with their anion binding properties as determined via UV-vis spectroscopic titrations carried out in dichloroethane. There is a striking difference between the interactions with anions of the two macrocycles, a finding ascribed to differences in their rigidity. For example, the more flexible dipyrromethane-derived macrocycle displays a 1.2:1 hydrogen sulfate versus nitrate selectivity, while its more rigid bipyrrole-derived congener shows a 7.4:1 selectivity in favor to hydrogen sulfate.     

Influence of thermal fluctuations on interfacial electron transfer in functionalized TiO2 semiconductors

The influence of thermal fluctuations on the dynamics of interfacial electron transfer in sensitized TiO2-anatase semiconductors is investigated by combining ab initio DFT molecular dynamics simulations and quantum dynamics propagation of transient electronic excitations. It is shown that thermal nuclear fluctuations speed up the underlying interfacial electron transfer dynamics by introducing nonadiabatic transitions between electron acceptor states, localized in the vicinity of the photoexcited adsorbate, and delocalized states extended throughout the semiconductor material, creating additional relaxation pathways for carrier diffusion. Furthermore, it is shown that room-temperature thermal fluctuations reduce the anisotropic character of charge diffusion along different directions in the anatase crystal and make similar the rates for electron injection from adsorbate states of different character. The reported results are particularly relevant to the understanding of temperature effects on surface charge separation mechanisms in molecular-based photo-optic devices.     

Metal ion binding by a bicyclic diamide: deep UV Raman spectroscopic characterization

Deep UV resonance Raman spectroscopy was used for characterizing ligand-metal ion complexes. The obtained results demonstrated a strong intrinsic sensitivity and selectivity of a Raman spectroscopic signature of a bicyclic diamide, a novel chelating agent for lanthanides and actinides (Lumetta, G. J.; Rapko, B. M.; Garza, P. A.; Hay, B. P.; Gilbertson, R. D.; Weakley, T. J. R.; Hutchison, J. E. J. Am. Chem. Soc. 2002, 124, 5644). Molecular modeling, which included structure optimization and calculation of Raman frequencies and resonance intensities, allowed for assigning all strong Raman bands of the bicyclic diamide as well as predicting the band shifts observed because of complex formation with metal ions. A comparative analysis of Raman spectra and the results of the molecular modeling could be used for elucidating the structure of complexes in solution.     

Synthesis,characterization and antitumor activity of palladium(II) complexes of imidazolidine-2-thione

Complexes of the type cis-[PdX₂(imzt)(PPh₃)] {imzt = imidazolidine-2-thione; PPh₃ = triphenylphosphine; X = Cl (1), Br (2), I (3), SCN (4)} have been synthesized and characterized by elemental analyses, molar conductance, IR and ¹H NMR spectroscopies. The complex 1·MeOH was obtained from the reaction of [PdCl₂(CH₃CN)₂], imidazolidine-2-thione and triphenylphosphine in CHCl₃/CH₃OH. Complexes 2·MeOH, 3 and 4 were prepared by metathesis of the chlorido ligands in 1 with bromide, iodide and thiocyanate, respectively. Elemental analyses showed good agreement with the expected mononuclear compositions, while the molar conductivities of the complexes in DMF were consistent with their nonelectrolytic nature. NMR spectra confirmed coordination of the imidazolidine-2-thione and triphenylphosphine ligands. Single-crystal X-ray diffraction determination of 1·CH₃OH showed that the coordination geometry around Pd^II is nearly square planar, with the chlorido ligands in a cis configuration. All four complexes have been tested in vitro by XTT assay for their cytotoxicity against human glioblastoma cell line (U87MG). The binding of 1 with guanosine was studied by ¹H NMR spectroscopy, revealing that the coordination takes place via N7.     

Stereoselective Synthesis and X-Ray Structure Determination of Labeled [1, 2, 3-<Superscript>13</Superscript>C<Subscript>3</Subscript>]-1-(Phenylsulfinyl)-3-Benzyloxyacetone

[1,2,3-¹³C₃]-1-(Phenylsulfinyl)-3-benzyloxyacetone, C₁₆H₁₆O₃S, (3) has been synthesized and its crystal structure has been determined by a single-crystal X-ray diffraction analysis. The X-ray diffraction study revealed that compound 3 crystallizes in the monoclinic crystal system in the acentric space group Pc, with cell constants at T = 100 K: a = 16.073(5), b = 5.5079(16), c = 7.949(2) Å, β = 100.221(4)^°, V = 692.6(3) ų, Z = 2, d _calc = 1.383 g/cm³. Compound 3 contains the chiral tetravalent three-coordinated sulfur atom, which has a distorted tetrahedral configuration with a lone electron pair occupying one of the tetrahedron vertices. In the crystal, the molecules are packed in stacks along the b axis; the stacks consist of the molecules of the same chirality. Furthermore, the stacks of the molecules of the opposite chirality alternate along the c axis. The molecules in neighboring stacks are arranged by head-to-tail orientations. There are no short intermolecular contacts in the crystal of 3.