Apatite-coated Ag/AgBr/Bi2WO6 nanocomposite: synthesis,characterization, and application as an efficient visible-light-driven photocatalyst

Research on Chemical Intermediates - A deposition method was applied to synthesize a multicomponent photocatalyst based on apatite (HaP)-coated Ag/AgBr/Bi2WO6 (denoted as HaP/Ag/AgBr/Bi2WO6)....     

Stereoselective Synthesis and Structure of New Types of Calix[4]resorcinarenes. Complexation of Tetrakis(O,O‐Phosphorus)Bridged‐Calix[4]resorcinarenes with Heavy Metal Atoms

The acid‐catalyzed (with HCl) condensation reactions of resorcinol ( 1 ) with 1‐naphthaldehyde ( 2 ) and isobutyraldehyde ( 3 ) furnished the tetrameric macrocyclic compounds 4 and 6 . Detailed NMR‐investigations of the acetylated tetrameric species 5 surprisingly support a structure not in agreement with the expected all‐cis conformation. The chair conformation (C_2h symmetry) of the acetylated derivative 5 was established through a crystal X‐ray diffraction study. The naphthyl substituents are arranged in trans position above and below the plane made up by the resorcinol units. The reaction of resorcinol 1 with isobutyraldehyde, in accord with expectation, led to the calix[4]resorcinaren ( 6 ). The ¹H NMR spectra of compound 6 and 7 appeared at room temperature as broad signals, indicating a conformation of C_2v symmetry. The reaction of the C‐methyl‐tetrakis‐P‐(chlorodioxaphosphocin)‐calix[4]resorcinarenes ( 8 ) and ( 10 ) with suitable N‐trimethylsilyl organic amines were conducted in tetrahydrofuran suspension, furnishing the P–N‐substituted calix[4]resorcinarenes ( 9 ) and ( 11 ). While in the complexation of C‐methyl‐tetrabromotetrakis‐P‐(dimethylaminodioxaphosphocin)‐calix[4]resorcinarene ( 13 ) with (tht)AuCl (tht = tetrahydrothiophene) the expected, neutral tetra‐substituted complex 15 was formed, the reaction of 13 with moist acetonitrile led to the anionic atomic framework 14 . X‐ray structure determinations of the complexes 14 and 15 show that both possess the cone conformation. In the gold complex 15 , the Au–Cl groups form a loose aggregate, with three Au…Cl contacts of 316–340 pm; one of the groups points towards the centre of the cone. The copper(I) complex 14 displays crystallographic mirror symmetry, with a central Cu₄Cl₅ unit involving tetrahedrally coordinated copper.     

An easy purification of glycoluril clips by affinity chromatography

A convenient method for separation and purification of glycoluril clips was developed on the basis of affinity chromatography using a resorcinol-functionalized Merrifield resin. The modified resin was readily prepared via immobilization of phlroglucinol on Merrifield resin. It was used for successful isolation of the desired clip products from their corresponding reaction mixtures. Also, the resin could be repeatedly recycled and reused without any noticeable decrease in its effectiveness.     

Darstellung intramolekular stabilisierter Diazaphosphorinan-Derivate mit der Trimethylethylendiamin- bzw. der Tetramethylguanidingruppe als Substituent am Phosphor: Studium intramolekularer Me2N → P-Wechselwirkungen

Formation of Intramolecularly Stabilized Diazaphosphorinane Derivatives with the Trimethylethylenediamine and the Tetramethylguanidine Group as Substituents at Phosphorus: Investigation of intramolecular Me₂N → P Interactions In the reaction of trimethylchlorophosphonium chloride 1 with N-trimethylsilyl-N′,N′,N″,N″-tetramethylguanidine 2 the expected guanidine-substituted trimethylphosphonium chloride 3 was formed, presumably via the ammonium chloride 3a which could not be isolated. By contrast, the reaction of the related chloromethyldimethylchlorophosphonium chloride 5 with N-trimethylsilyl-N,N′,N′-trimethylethylenediamine 6 and N-trimethylsilyl-N′,N′-dimethylethylene diamine, 7 , respectively, furnished in an unusual fashion six-membered heterocycles, the ammonium-phosphonium dichlorides 10 and 11 . Their formation involved cleavage of both the P? Cl and the C? Cl bond, followed by intramolecular C←N-acceptor-donor interaction. A similar C←N interaction was not observed in the reaction of 5 with 2 , and the acyclic product 12 was formed. The reaction of chloromethylmethylchlorophosphine 13 with the hydrogen peroxide/urea 1:1-adduct led to chloromethylmethylphosphinic acid 14 . Attempts at the reaction of 14 with 2 or with SOCl₂ were unsuccessful. The reaction products were characterized by ¹H-, ¹³C-, ³¹P- and, in two cases, by ¹⁵N-NMR-spectroscopy.     

Molecular structures and ab initio molecular orbital calculations of the optically active derivatives of 1-aminocyclopropane-1-carboxylic acid

The novel optically active derivatives of 2,2′-disubstituted-1-aminocyclopropane-1-carboxylic acid (−)-2 and (+)-3 were synthesised from the spiro-azlactone (+)-1. Oxidation of the diol moiety of (+)-3 gave by ring enlargement the racemic mixture of 2,3-dihydrofuran derivative (±)-6. This conversion is explained by stepwise rearrangement of the initially formed tetrasubstituted cyclopropanecarbaldehyde 4 through zwitterionic's reactive intermediate 5. The formation of (±)-6 is preferred energetically as established by ab initio calculations of the ground states and possible intermediates for that rearrangement. The crystal structure and absolute configuration of the compounds (+)-1, (−)-2, (+)-3 and (−)-7 were determined by single-crystal X-ray diffraction method. All four compounds possess Z-configuration of the cyclopropane ring. The dioxolane ring in the structures (+)-1 and (−)-2 adopts half-chair conformation, while the cyclopropane ring and geminally substituted groups in the structures (−)-2, (+)-3 and (−)-7 possess the anticlinal conformation. The molecules of the compound (+)-1 are connected by very weak intermolecular hydrogen bond of C-H?O type. In the compounds (−)-2, (+)-3 and (−)-7inter- and intramolecular hydrogen bonds of N-H?O type were observed. The spiro-compound (+)-1 exhibited a more pronounced inhibitory activity against the proliferation of murine leukemia and human T-lymphocytes cells than other type of tumor cell lines and normal human fibroblast cells.     

Chemical composition, antioxidant and antibacterial properties of Achillea collina Becker ex Heimerl s.l. and A. pannonica Scheele essential oils

The in vitro antioxidant and antimicrobial activities of two Achillea millefolium (Adanson) Koch s.l species essential oils (A. collina Becker ex Heimerl s.l. and A. pannonica Scheele, Asteraceae) originating from the Golija and Radan mountains (Serbia) were investigated. The chemical profiles of the essential oils were evaluated by GC-MS. Antioxidant activity was assessed as free radical scavenging capacity (RSC) towards 2,2-diphenyl-1-picrylhydrazil (DPPH) radicals, together with effects on lipid peroxidation (LP). Antibacterial activity was examined on 21 bacterial strains. Based on the chemical composition of the essential oil, A. collina s.l. from Mount Golija was classified as a chamazulene chemotype (tetraploid). The high percentage of oxygenated monoterpenes and absence of azulene in the essential oil obtained from A. pannonica from Radan pointing that this population is octaploid. Essential oil of A. pannonica expressed stronger antimicrobial activity on almost all tested bacteria. Furthermore, this essential oil expressed higher scavenging effects on DPPH radical (IC(50) = 0.52 comparing to 0.62 mug/mL). Only in the LP evaluation, essential oil of A. collina s.l. from Golija exhibited stronger antioxidant activity (IC(50) = 0.75 comparing to 2.12 mug/mL).     

Solvent-assisted intramolecular proton transfer in thiopurinol: application of M06-2X functional

All available conformers of tisopurine as an important pharmaceutical molecule are optimized and frequency calculations calculated at M06-2X/6-311++G(2d,2p) level of theory. These conformers are classified in 22 different tautomers, tautomer Z showing the most stable tautomer in the gas phase. Effects of four different solvents on the most stable conformer of each tautomer is calculated. Solvents cause stabilization of all conformers and relative solvent stabilization is as follows: water > DMSO > acetone > toluene. Energy profile for such stabilization is illustrated and mechanism of proton transfer studied at the same level of theory. Solvent-assisted proton transfer performed when water and methanol used as solvents. Results indicate that explicit solvent effect has much more stabilization on tautomerization processes compared to implicit solvent effect.     

Nonlinear Unmixing of Hyperspectral Datasets for the Study of Painted Works of Art

Nonlinear unmixing of hyperspectral reflectance data is one of the key problems in quantitative imaging of painted works of art. The approach presented is to interrogate a hyperspectral image cube by first decomposing it into a set of reflectance curves representing pure basis pigments and second to estimate the scattering and absorption coefficients of each pigment in a given pixel to produce estimates of the component fractions. This two‐step algorithm uses a deep neural network to qualitatively identify the constituent pigments in any unknown spectrum and, based on the pigment(s) present and Kubelka–Munk theory to estimate the pigment concentration on a per‐pixel basis. Using hyperspectral data acquired on a set of mock‐up paintings and a well‐characterized illuminated folio from the 15th century, the performance of the proposed algorithm is demonstrated for pigment recognition and quantitative estimation of concentration.     

Synthesis of 2-aroylfuran and novel 3,5-diaroyl-4-arylisoxazole derivatives by ring contraction of pyrylium salts

Research on Chemical Intermediates - Ring contraction of 2,4,6-triarylpyrylium perchlorates by use of sodium nitrite mediated by ionic liquid has been used as a new, direct, and environmentally...