K. Van Hecke

Chemo-denitrification of nitrate-polluted water

Nitrate-nitrogen reduction was studied in the presence of ferrous iron and a copper catalyst. In a batch system, it was found that the reduction was very fast at pH 8.1 and slow at pH 7.5. A temporary accumulation of nitrate and hydroxylamine was noted. It was found that the reduction of nitrite-nitrogen in the presence of ferrous iron partly continued to ammonium. Decreasing the amount of reagents led to a slower reduction rate but a lower accumulation of nitrite and hydroxylamine. A continuous system was described whereby more than 50% of the initial nitrate could be removed.

Constituents of Artemisia tschernieviana and Their Biological Activity

Artemisia tschernieviana Besser (Asteraceae) is a plant of the Kazakhstan flora that is little studied chemically [1]. The antioxidant and antihemolytic activity of the extract of A. tschernieviana from Iran [2] and the composition and antimicrobial activity of essential oil [3–6] were studied before. Ground aerial part (leaves and stems) of the plant collected in western Kazakhstan in July 2013 was extracted by CHCl3–EtOH. The obtained extract was separated by column chromatography over silica gel using gradient elution by hexane, EtOAc, and EtOH. Elution by hexane–EtOAc (3:1) isolated a colorless crystalline compound 1, the structure of which was elucidated using spectral data and an x-ray crystal structure analysis (XSA). PMR and 13C NMR spectra were interpreted using 2D 1H–1H COSY and HSQC. Positions of individual atoms were determined using DEPT and 2D HMBC. Figure 1 shows the molecular structure of 1. The isolated compound 1 was the methyl ester of 3-(5 -hydroxyprenyl)-p-coumaric acid according to spectral data (PMR, 13C NMR, 13C DEPT, 1H–1H COSY, 1H–13C HSQC, HMBC) and an XSA. Compound 1 was isolated earlier from A. marschalliana Spreng. [7] and A. xanthochroa [8] and was also prepared synthetically [9]. Elution of the column by hexane–EtOAc (3:1) isolated compound 2, the structure of which was confirmed by an XSA, according to which 2 was identified as 6-demethoxy-4 -O-methylcapillarisin, which was isolated earlier [10]. Compounds 1 and 2 were isolated from A. tschernieviana for the first time. We investigated the cytotoxic, antimicrobial, antifungal, antimalarial, and antioxidant activity of the extracts, essential oil, and constituents of A. tschernieviana. Antiradical activity was studied using several extracts of A. tschernieviana, i.e., CHCl3 (Atsch-1), EtOAc (Atsch-2), and EtOH (Atsch-3). Essential oil (Atsch-4) was obtained by steam distillation in a Clevenger apparatus. Optical density of the obtained compounds was measured dependent of concentration on a Cary 60 UV-Vis spectrophotometer at 520 nm. Antiradical activity of the samples was compared with that of butylhydroxyanisole (BHA) [11]. Table 1 presents the results for the antiradical activity.

Peralkylated imidazolium carbonate ionic liquids: synthesis using dimethyl carbonate, reactivity and structure

Tri- and tetra-alkylimidazoles are quaternised into their corresponding ionic liquids with dimethyl carbonate. Upon metathesis of the obtained methyl carbonate salts, only gaseous by-products are generated. These methyl carbonate salts can be transformed into hydrogen carbonate salts by reaction with water. The salts containing a carbonate anion are very alkaline, which results in a hydrogen/deuterium exchange on the anion and some of the cation protons, depending on the substitution. Moreover, the crystalline 1-ethyl-3,4,5-trimethylimidazolium hydrogen carbonate formed carboxylate species upon dissolution. In particular, the carboxylate was able to regenerate the carbene and in the presence of chloroform, this led to the formation of the chloride salt.

Crystal structure and fluorescence of a 1D zinc(II) coordination polymer based on a semi-rigid bis(benzimidazole) ligand

A new Zn(II) coordination polymer, {[Zn(npht)(L)0.5(H2O)]•H2O}n (L = 1,4-bis(2-methylbenzimidazol-1-ylmethyl)benzene, H2npht = 3-nitrophthalic acid) has been hydrothermally synthesized and characterized by elemental analysis, IR, XRPD, and single-crystal X-ray diffraction. The zinc(II) coordination compound exhibits a 1D linear chain, which is further assembled into a 2D supramolecular layer via two modes of classial hydrogen bonding interactions. The fluorescence properties and thermal stability of the complex have been investigated in the solid state.

Synthesis, crystal structure, and properties of an azido-bridged 1D nickel hexaazamacrocyclic complex

A new complex of [Ni(C15H32N6)(N3)]ClO4 · H2O was obtained by the reaction of macrocyclic precursor complex [Ni(C15H32N6)]ClO4 with sodium azide in water solution, and characterized by EA, IR, PXRD and single-crystal X-ray diffraction (CIF file CCDC no. 930570). Single X-ray diffraction analysis reveals that the central nickel(II) ion displays six-coordinate octahedral coordination geometry by coordination with four nitrogen atoms of N3− macrocyclic ligand and two nitrogen atoms of ligand. In this complex, each μ1,3-N3− binds two nickel(II) ions, resulting a 1D chain. Magnetic measurements have been performed on the complex, showing strong antiferromagnetic coupling interaction within the metal center.

Crystal Structure of 1,2-Bis(Acetoxymethyl)-O-Carborane

The crystal structure of 1,2-bis(acetoxymethyl)-o-carborane is determined by the X-ray crystallographic analysis.

Crystal and Molecular Structure, and Cytotoxic Activity of diethyl ether of 2-[(phenyl-(phenyl-o-carboranyl)- methyl]malonic acid

The crystal and molecular structure of diethyl ether of 2-[(phenyl-(phenyl-o-carboranyl)-methyl]malonic acid is determined by single crystal X-ray diffraction and NMR spectroscopy for the first time. The cytotoxic activity of the molecule is analyzed.

Crystal structure and absolute configuration of 28-O-acetylbetulin

For the first time the crystal structure and absolute configuration of 28-O-acetylbetulin are determined by the X-ray crystallographic analysis.

Beyond the Diketopiperazine Family with Alternatively Bridged Brevianamide F Analogues.

A method for the preparation of 3,5-bridged piperazin-2-ones from a tryptophan-proline-based diketopiperazine is described using diphosgene to induce the ring closure. Density functional theory calculations were conducted to study the mechanism of this C-C bond formation. Several derivatives of the thus obtained α-chloroamine were synthesized by substitution of the chlorine atom using a range of O-, N-, S-, and C-nucleophiles. This novel class of brevianamide F analogues possess interesting breast cancer resistance protein inhibitory activity.