Novel Diazocrowns with Pyrrole Residue as Lead(II)Colorimetric Probes

Novel 18- and 23-membered diazomacrocycles were obtained with satisfactory yields by diazocoupling of aromatic diamines with pyrrole in reactions carried under high dilution conditions. X-ray structure of macrocycle bearing five carbon atoms linkage was determined and described. Compounds were characterized as chromogenic heavy metal ions receptors. Selective color and spectral response for lead(II) was found in acetonitrile and its mixture with water. Complexation properties of newly obtained macrocycles with a hydrocarbon chain were compared with the properties of their oligoether analogs. The influence of the introduction of hydrocarbon residue as a part of macrocycle on the lead(II) binding was discussed. Selective and sensitive colorimetric probe for lead(II) in aqueous acetonitrile with detection limit 56.1 mg/L was proposed.

STABILITY OF THIOAMIDE TYPE OF PIPERINE UNDER ACIDIC AND BASIC CONDITIONS

Thioamide type of piperine, “thiopiperine” is a derivate of piperine that having high potency against breast cancer cells. This research was intended to evaluate the stability of thiopiperine under highly acidic and basic conditions for 72 h at 60⁰C. This study was conducted by the SHIMADZU® UFLC system integrated with a PDA detector, while the analysis was performed in an isocratic separation mode using column C-18 (COSMOSIL®), 150 mm x 4.6 mm, column particle size: 5 µm. Chromatography condition was set using a mobile phase consisting of 50% aqueous acetonitrile with a flow rate of 1 mL/min, while the detection wavelength was 340 nm. The result showed that thiopiperine undergoes extensive degradation under acidic and basic environments.

Brønsted Acid Catalysis in the Oxidation of Purine Based Alkaloids by Mn(VII) in Aqueous Acetonitrile and Sodium Fluoride Medium: A Kinetic Approach

Brønsted acid (HClO4, H2SO4) catalyzed Mn(VII) oxidation of purine alkaloids such as caffeine, theophylline and theobromine in aqueous acetonitrile and sodium fluoride medium revealed first order kinetics in both [(Mn(VII)] and [Alkaloid] at constant acidity and temperature. Sodium fluoride was added to the reaction mixture in order to avoid/suppress auto catalytic reaction due to the generation of Mn(III) and Mn(IV) species during the course of Mn(VII) oxidations in acidic solutions. An increase in the Brønsted acids (HClO4, H2SO4) concentration accelerated the rate of oxidation. Rate enhancements observed here in are analyzed by Zucker-Hammett, Bunnett and Bunnett-Olsen criteria of acidity functions. On the basis of observed Bunnett-Olsen criteria of acidity functions, the most plausible mechanism has been proposed with the involvement of water molecule in the slow step (as proton transferring agent).

A highly active and robust iron quinquepyridine complex for photocatalytic CO2 reduction in aqueous acetonitrile solution

[Fe(qnpy)(H2O)2]2+ is a highly efficient and robust catalyst for visible-light-driven reduction of CO2 to CO, with a TON for CO of up to 14 095 and selectivity of 98% using Ru(phen)3Cl2 as photosensitizer and BIH as sacrificial reductant.