Volume 76, Issue 9

Chemical investigation of the roots of Trichilia welwitschii yielded a cycloartane type terpenoid 28,29-bis-norcycloart-24-en-3 β ,4 α ,6 α -triol ( 1 ), isolated as pure compound for the first time, three coumarins and three sterols. New cycloartane derivatives ( 1a ) and ( 1b + 1c ) were obtained by hemi-synthetic reaction of compound 1 . The structures of 1a – c were established by spectroscopic methods including 1D and 2D-NMR analysis, HR-EIMS, chemical transformations and by comparison of these data with those of related compounds. Evaluated for their antimycobacterial potential, compound 1 and 1b + 1c were determined to show significant activities against Mycobacterium tuberculosis MIC values of 6.25 μg mL −1 while compound 1a displayed weak activity showing MIC > 100 μg mL −1 . Compounds 2 – 4 displayed moderate activity with MIC values range from 12.5 to 50 μg mL −1 .

2-(1 H -benzo[ d ]imidazol-2-yl)quinoline (BQ) as ligand and three coordination compounds of formula {Zn(BQ)Cl 2 } ( 1 ), {Pb(BQ)Cl 2 } n ( 2 ) and {[Cu(BQ) 2 (OC(O)CH 3 )]OC(O)CH 3 · CH 3 COOH} ( 3 ) have been synthesized and fully characterized. The complexes crystallize in triclinic space group P 1 ‾ $P‾{1}$ . In complexes 1 and 2 , the coordination geometry is a distorted tetrahedral environment around the zinc center and a distorted sixfold coordination geometry around the lead center, respectively. In complex 3 the central Cu(II) center is in a trigonal bipyramidal coordination geometry. The Cu(II) ion is surrounded by two bidentate 2-(2′-quinolyl)benzimidazole (BQ) ligands and one coordinated acetate molecule. One further acetate anion associated by a strong hydrogen bond with a molecule of acetic acid balances the charge of the compound.

An ammonium perchlorate (AP) and copper(II) benzoate pyrotechnic blue-flame composition was gradually “diluted” by adding an experimental perchlorate-free blue-flame composition based on aminoguanidinium nitrate (AGN), malachite, PVC powder and shellac resin. Flame’s luminous intensity and specific luminous intensity were recorded and analyzed. A copper-aminoguanidinium (CuAG) complex was also synthesized and tested as an energetic additive in perchlorate-free blue-flame composition. Green-flame color was observed when testing chlorine-free energetic compositions with CuAG.

Bis(trifluoromethyl)-substituted quinolino[8,7- h ]quinolines and quinolino[7,8- h ]quinolines have been prepared from 3-substituted 1-CF 3 -prop-2-yne 1-iminium triflate salts and 1,5- and 1,8-diaminonaphthalene, respectively, by a twofold pyridoannelation sequence. These transformations do not require any additional reagent and can be performed at remarkable mild thermal conditions.

GdPtMg and YPtMg (both crystallize with the ZrNiAl-type structure) form a complete solid solution Gd 1– x Y x PtMg. Samples in x  = 0.1 steps were synthesized from the elements in sealed tantalum ampoules in an induction furnace and characterized by Guinier powder patterns. The structures of four members of the solid solution were refined from single-crystal X-ray diffractometer data, confirming the mixed occupation of the Gd/Y site; however, without any indication for Gd/Y ordering. Temperature dependent magnetic susceptibility measurements reveal Curie-Weiss behavior for all samples and ferromagnetic ordering in the low-temperature regime. The Curie temperature drops linearly from 97.6 K for GdPtMg to 3.7 K for Gd 0.1 Y 0.9 PtMg. All samples are soft ferromagnets. The Gd/Y substitution is a suitable tool for adjusting magnetic ordering temperatures of gadolinium intermetallics over a broad temperature range.

A method for the synthesis of oligotetramethylene oxides with terminal amino groups is presented. Its use as a hardener for urethane-containing oligomers has been demonstrated. The diamines were synthesized by a two-stage method based on oligotetramethylene oxide diol. The compounds can be used for the production of non-toxic, biocompatible and biodegradable segmented urethane-containing elastomers. The oligotetramethylene oxide diol with an average molecular mass of 1008 was chosen as a typical precursor component. Its dibromide was formed using a quasi-phosphonium reagent in various solvents. The corresponding amine was obtained by high-pressure amination. The compounds have been identified by 1 H and 13 C NMR spectroscopy, IR spectroscopy, and elemental analysis.

Three new hybrid two-dimensional (2D) organic–inorganic semiconductors are presented, which contain lead halides and a mixture of hexanediamine-based isomers in the stoichiometry [2,2,4 (2,4,4)- trimethyl-1,6-hexanediamine]PbX 4 (X = I, Br, Cl). These hexanediamine derivatives, with attached methyl groups at the carbon backbone of both isomers, determine the packing of the organic layers between the inorganic 2D sheets, while the optical absorption and photoluminescence spectra reveal excitonic peaks at T  = 77 K and room temperature. The as-synthesized semiconductors were stored for three years in the dark and under low humidity and were examined again and the results were compared to those of the fresh materials. The chloride analogue, after the three year storage, displays white-like luminescence. The use of non-equivalent isomer and racemic mixtures in the organic component to form hybrid organic–inorganic semiconductors is an efficient method to alter the properties of 2D perovskites by tuning the isomers’ chemical functionalities. Finally, a comparison of the observed excitonic absorption and photoluminescence signals to that of analogous 2D compounds is discussed.

A new carbon paste electrode (Ag-CPE) modified with a nitrogen heterocyclic silver(I) complex, [Ag 2 (BBP) 2 ](pic) 2 ·CH 3 OH (BBP = 1,3-bis(1 H -benzimidazol-2-yl)propane, pic = picrate), was developed as a highly sensitive and simple electrochemical sensor for the determination of hydrogen peroxide. The Ag(I) complex was prepared by an interface reaction and characterized by elemental analysis, IR and UV/Vis spectra and single crystal X-ray diffraction. The Ag(I) complex shows a dinuclear cluster structure, which is formed by two BBP ligands bridging two Ag (I) centers and an Ag–Ag interaction ( d Ag–Ag  = 3.0875 Å). Cyclic voltammetry and chronoamperometry studies showed that the electrochemical sensing performance of Ag-CPE for H 2 O 2 was improved in 0.2  m phosphate buffer solution (PBS, pH = 6). The electrochemical H 2 O 2 sensor Ag-CPE exhibits a wide linear detection range from 0.5 to 4.0 m m and a lower detection limit of 0.39 μ m with a relatively high sensitivity of 6.77 μA m m −1 . Moreover, the sensor also shows good anti-interference properties and stability. The results prove that the Ag(I) complex based on the bis(benzimidazole) ligand may be an efficient component of electrode materials.