Characterisation and cryomagnetic study of a hydrothermally synthesised hydrogen bonded L–M–L type co-ordination polymer

A ligand–metal–ligand type co-ordination polymer [Ni (C₆H₁₂N₄)(NCS)₂(H₂O)₂] _n has been synthesised under controlled hydrothermal conditions. Here 1,3,5,7-tetraazatricyclo[3.3.1]decane [or hexamethylenetetramine (hmt)] has been used as a μ-(N,N′) bidentate spacer molecule. The prepared polymeric complex has been characterised by elemental and spectral analyses. The structure has been confirmed by a single crystal X-ray diffraction study. Magneto-structural correlation has been drawn from cryomagnetic susceptibility measurements (2–300 K) which unequivocally reflects very weak magnetic spin interactions among the long distant octahedral Ni(II) metal centres mediated by hmt and weak hydrogen bonding interactions between the adjacent zigzag one-dimensional polymeric chains carrying into a two-dimensional infinite polymeric framework.     

Indirect bromometric microdetermination of nitrate and perchlorate,using nitron as reagent

Summary An indirect bromometric method for the determination of nitrate or perchlorate is described. A known excess of standard nitron acetate solution is added to the sample solution to precipitate the anion to be determined; the excess of reagent is then determined in the supernatant liquid by bromatometric titration. The relative standard deviation of the method is 0.7% for nitrate and 0.5% for perchlorate. Sulphate, phosphate and fluoride do not interfere and chloride does not interfere up to a concentration of 0.1 M. Bromide, iodide, chromate, nitrite and chlorate interfere but can be eliminated.

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Zusammenfassung Ein indirektes bromatometrisches Verfahren zur Bestimmung von Nitrat oder Perchlorat wurde beschrieben. Ein gemessener Überschuß einer Nitronacetatlösung bekannter Konzentration wird zur Fällung des Anions der Probe zugesetzt und im Überstand bromatometrisch zurücktitriert. Die rel. Standardabweichung beträgt 0,7% für Nitrat und 0,5% für Perchlorat. Sulfat, Phosphat und Fluorid stören nicht; Chlorid stört nicht bis zu 0,1-m Konzentration. Bromid, Jodid, Chromat, Nitrit und Chlorat stören zwar, können aber eliminiert werden.

     

Correction: New stiff matter solutions are really not stiff

Four new solutions in general relativity have recently been derived as representing static spherically symmetric stiff matter,=p. It is pointed out that the equation of state is, in fact,+p=0. It is further shown that two of the solutions are physically reasonable, turning out to represent the vacuum, one of them with a term.     

An application of the mannich reaction using hydroxylamine and some of its derivatives. 6-Substituted-2,4-diamino-5,6,7,8-tetrahydropyrimido[4,5-dpyrimidines

Hydroxylamine and some of its O -substituted derivatives ( 2 ) have been used as the amine component in Mannich reactions with 2,4,6-triaminopyrimidine ( 1 ). The resulting 6-substituted tetrahydropyrimido[4,5-d]-pyrimidines ( 3 ) contain an N-0 bond linking the substituent to the ring. These results extend the utility of this modified Mannich reaction to otherwise inaccessible substituents. Reaction conditions, spectral data and certain limitations of the reaction are discussed.     

A Convenient Synthesis and a Nuclear Magnetic Resonance Spectroscopic Study of a β-D Linked Trisaccharide

The building block derivatives of the monosaccharide, O-(3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-β-D-glucopyranosyl) trichloroacetimidate (1), and the disaccharide α, α-trehalose, 2′,3′6′-tri-O-benzoyl-α-D-glucopyranosyl-2,3,4,6-tetra-O-benzoyl-α-D- glucopyranoside (2) were coupled to produce trisaccharide 3. A detailed n.m.r. analysis [ ¹H, ¹³C, ¹³C-¹H correlation, and 2D ¹H-¹H correlation experiment (COSY)] was used for the structural elucidation of the building blocks 1, 2 and the trisaccharide product 3.     

Structural studies and biological evaluation of Co (II), Ni (II) and Cu (II) complexes of carbohydrazone derived from ethyl acetoacetate in addition to crystallographic description of La (III) or Sm (III) catalytic activity abnormal product

New carbohydrazone ligand derived from the condensation of carbohydrazide and ethyl acetoacetate, diethyl 3,3′‐(carbonylbis (hydrazin‐2‐yl‐1‐ylidene))(3E,3′E)‐dibutyrate (H₄EBC), and its divalent Co, Ni and Cu chelates have been isolated and characterized utilizing convenient methods. ¹H‐NMR spectrum of H₄EBC revealed the abundance of the enol isomer in solution, which was the opposite to what was shown by the solid IR. This was supported by comparing the theoretical IR of both keto and enol forms. In [Ni(H₄EBC)Cl₂(H₂O)]·2H₂O, H₄EBC acts as a neutral NON tridentate ligand via the (C=O)_carbonyl oxygen atom besides the two (C=N)_azomethine nitrogen atoms, while in [Co(H₄EBC)Cl₂(2H₂O)]·2H₂O, H₄EBC behaves as a neutral NN bidentate ligand through the two azomethine groups. Magnetic measurements inherent to their electronic spectra show that both Ni (II) and Co (II) chelates have octahedron coordination frameworks. On the other hand, the ligand behaves as a binegative tetradentate in [Cu₂(H₄EBC)Cl₂]·H₂O via the deprotonated (C=O)_carbonyl groups of the ethyl acetoacetate framework and the two (C=N)_azomethine groups. In the latter complex, the carbonyl group of the carbohydrazide moiety is converted to hydroxyl group. Cu (II) complex has a tetrahedral geometry according to ESR and electronic spectral data. The reaction of H₄EBC with SmCl₃·6H₂O or LnCl₃·7H₂O gave single crystals of abnormal product (C₁₆H₁₆N₄O₄). The packing diagram of this crystal has a chain structure. The photoluminescence spectra of [Cu ₂ (H ₄ EBC)Cl ₂ ]·H ₂ O , [Co(H ₄ EBC)Cl ₂ (H ₂ O) ₂ ]·2H ₂ O and [Ni(H ₄ EBC)Cl ₂ (H ₂ O)]·2H ₂ O display emission broad‐bands at 342, 321 and 337 nm, respectively. The microbial behavior of the synthesized moieties was investigated against various bacterial and fungal strains. [Cu₂(H₄EBC)Cl₂]·H₂O complex shows the same activity as ampicillin towards Escherichia coli and Staphylococcus aureus with inhibition zones of 26 and 22 mm, respectively. Antioxidant activity is determined using bleomycin‐dependent DNA damage assay besides erythrocyte hemolysis. Finally, in vitro cytotoxic activities against two different cell lines have been examined.     

Synthesis,spectroscopic characterization,thermal behaviour,in vitro antimicrobial and anticancer activities of novel ruthenium tricarbonyl complexes containing monodentate V‐shaped Schiff bases

The interaction of Ru₃(CO)₁₂ with a novel family of monodentate V‐shaped Schiff base ligands (L^1–4; L¹: (E)‐1‐(4‐((4‐bromobenzylidene)amino)phenyl)ethanone, L²: (E)‐1‐(3‐(4‐(dimethylamino)benzylideneamino)phenyl)ethanone, L³: (E)‐1‐(4‐(4‐(dimethylamino)benzylideneamino)phenyl)ethanone, L⁴: (E)‐1‐(3‐(3,4‐dimethoxybenzylideneamino)phenyl)ethanone) in air under atmospheric pressure afforded the novel complexes [Ru(CO)₃(L^1–4)₂]. The parent ligands and their complexes were characterized using elemental analyses and spectroscopic techniques. In addition, the structure of the representative ligand L¹ was determined using single‐crystal X‐ray analysis. The stereochemistry and theoretical optimization of the three‐dimensional geometry of the ligands and their complexes were justified. In vitro antimicrobial screening against bacterial stains Escherichia coli and Staphylococcus aureus and fungus Candida albicans was conducted. Cytotoxicity of the compounds as anti‐tumour agents was evaluated against liver carcinoma (HepG2), breast carcinoma (MCF7) and colon carcinoma (HCT‐116) cell lines relative to cisplatin and doxorubicin. The complexes showed variable in vitro cytotoxic activities against the three studied cell lines, with IC₅₀ values less than those of cis‐platin, and thus appear to be building blocks for promising anti‐tumour agents.     

Biochemical Properties of Tyrosinase from Aspergillus terreus and Penicillium copticola; Undecanoic Acid from Aspergillus flavus,an Endophyte of Moringa oleifera,Is a Novel Potent Tyrosinase Inhibitor

Tyrosinase is a copper-containing monooxygenase catalyzing the O-hydroxylation of tyrosine to 3,4-dihydroxyphenylalanine then to dopaquinone that is profoundly involved in melanin synthesis in eukaryotes. Overactivation of tyrosinase is correlated with hyperpigmentation that is metabolically correlated with severe pathological disorders, so, inhibition of this enzyme is the most effective approach in controlling the overproduction of melanin and its hazardous effects. Thus, searching for a powerful, selective inhibitor of human tyrosinase to limit the hyper-synthesis of melanin is a challenge. Unlike the difficulty of overexpression of human tyrosinase, using fungal tyrosinase as a model enzyme to the human one to evaluate the mechanistics of enzyme inhibition in response to various compounds is the most feasible strategy. Thus, the purification of highly catalytic-efficient fungal tyrosinase, exploring a novel inhibitor, and evaluating the mechanistics of enzyme inhibition are the main objectives of this work. Aspergillus terreus and Penicillium copticola were reported as the most potential tyrosinase producers. The biochemical properties suggest that this enzyme displays a higher structural and catalytic proximity to human tyrosinase. Upon nutritional bioprocessing by Plackett–Burman design, the yield of tyrosinase was increased by about 7.5-folds, compared to the control. The purified tyrosinase was strongly inhibited by kojic acid and A. flavus DCM extracts with IC₅₀ values of 15.1 and 12.6 µg/mL, respectively. From the spectroscopic analysis, the main anti-tyrosinase compounds of A. flavus extract was resolved, and verified as undecanoic acid. Further studies are ongoing to unravel the in vivo effect and cytotoxicity of this compound in fungi and human, that could be a novel drug to various diseases associated with hyperpigmentation by melanin.