Varying the metal/metal ratio in related Cu–Ca complexes

We demonstrate with the help of structural determinations and spectroscopic data that the nuclearity of Cu–Ca complexes derived from compartmental Schiff base ligands does not depend on the ionic radius of calcium. The main factors governing these reactions are the different affinities of the calcium ions for the anionic species present in solution: the tetradentate O₂O₂ coordination site of the ligand and the nitrato ions. Because these affinities do vary upon going from calcium to lanthanide ions, it is not possible to use the template effect of the trinuclear Cu–Ca–Cu complexes in order to prepare the corresponding Cu–Ln–Cu complexes.     

Synthesis of polyfunctionally substituted heteroaromatic compounds via benzotriazolyl chalcones with antimicrobial and antifungal activities

The utility of both 3‐(1‐benzotriazolyl) chalcone derivatives 3a‐c and 2‐(1‐benzotriazolyl)‐1,4‐pentadien‐3‐one (18) in the synthesis of some new 2‐(1H)‐pyridone, pyridine, pyrazole and isoxazole derivatives is reported. Antimicrobial and antifungal screening of some selected examples from the synthesized products were carried out. The structure of the newly synthesized compounds was elucidated by elemental analysis, ir, ¹H and ¹³C nmr investigations.     

Microwave-assisted regioselective N-alkylation of cyclic amidines

A simple and efficient methodology for regioselective alkylation of exocyclic nitrogen of cyclic amidines was developed by microwave-assisted heating in the presence of amines. Novel N-alkylated 3,4-dihydropyrazino[2,1-b]quinazolin-6-ones were prepared in good yields. The reaction occurred via a transamination (addition-elimination) process involving a first attack of the amine on the electrophilic carbon of the amidine function.     

Core-Modified Coelenterazine Luciferin Analogues: Synthesis and Chemiluminescence Properties

In this work on the design and studies of luciferins related to the blue-hued coelenterazine, the synthesis of heterocyclic analogues susceptible to produce a photon, possibly at a different wavelength, is undertaken. Here, the synthesis of O-acetylated derivatives of imidazo[1,2-b]pyridazin-3(5 H)-one, imidazo[2,1-f][1,2,4]triazin-7(1 H)-one, imidazo[1,2-a]pyridin-3-ol, imidazo[1,2-a]quinoxalin-1(5 H)-one, benzo[f]imidazo[1,2-a]quinoxalin-3(11 H)-one, imidazo[1′,2′:1,6]pyrazino[2,3-c]quinolin-3(11 H)-one, and 5,11-dihydro-3 H-chromeno[4,3-e]imidazo[1,2-a]pyrazin-3-one is described thanks to extensive use of the Buchwald–Hartwig N-arylation reaction. The acidic hydrolysis of these derivatives then gave solutions of the corresponding luciferin analogues, which were studied. Not too unexpectedly, even if these were “dressed” with substituents found in actual substrates of the nanoKAZ/NanoLuc luciferase, no bioluminescence was observed with these compounds. However, in a phosphate buffer, all produced a light signal, by chemiluminescence, with extensive variations in their respective intensity and this could be increased by adding a quaternary ammonium salt in the buffer. This aspect was actually instrumental to determine the emission spectra of many of these luciferin analogues.     

Effect of surfactant and mineral additive on the efficiency of lead-acid battery positive active material

The effect of Sodium tripolyphosphate (STPP) and mineral additive on the performance of the lead-acid battery positive plate has been investigated. The addition of alumina-silicate to the positive paste and STPP to the electrolyte modifies the shape and size of PbO₂ crystals and improves the utilization of the positive active material (PAM). The electrochemical performance of the positive active material was determined using galvanostatic discharge and electrochemical impedance spectroscopy (EIS). The crystal structure and morphology of the PAM (PbO₂) were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The water content of the PAM was calculated using Thermogravimetric analysis (TGA) technique. The results showed that the addition of surfactant and mineral additive changes the morphology and the crystallite size of the PAM. We observe a remarkable improvement of the discharge capacity of the PAM when the surfactant (STPP) is added in the electrolyte. The discharge capacity increases with the decrease of the crystallite size and the charge transfer resistance R_ct of the PAM. This shows that the addition of mineral additive and the surfactant together improves the electrical performance of lead-acid battery.     

Production of l-menthyl acetate through kinetic resolution by Candida cylindracea lipase: effects of alkaloids as additives

Research on Chemical Intermediates - Enzymatic transesterification of dl-menthol with vinyl acetate in tert-Butyl methyl ether (TBME) catalyzed by Candida cylindracea lipase (CCL) was carried out...