Kinetic and equilibrium adsorption of two post-harvest fungicides onto copper-exchanged montmorillonite: synergic and antagonistic effects of both fungicides' presence.

The simultaneous adsorption of both imazalil (IMZ) and thiabendazole (TBZ) fungicides in a Cu2+-exchanged Mt was studied in this work. Kinetic studies were used to determine the rate law which describes the adsorption of individual fungicides onto the adsorbent. Adsorption isotherm of individual and combined fungicides was done to evaluate synergic or antagonistic effects. The Mt-Cu material considerably improved TBZ and/or IMZ adsorption from aqueous suspensions with respect to raw Mt, leading to removal efficiencies higher than 99% after 10 min of contact time for TBZ and IMZ Ci = 15 and 40 mg/L, respectively, when a solid dosage = 1 g/L was used. The adsorption sites involved were determined by a combination of X-ray diffraction (XRD) determinations and electron paramagnetic resonance (EPR), indicating that fungicides were bonded to Cu2+ cations, while the rate limiting step was the formation of coordination bonds. The adsorption mechanism proposed is that of ligand exchange between water and fungicide molecules in the metal coordination sphere. The single-crystal structure for the IMZ-Cu2+ complex indicated that four molecules were bounded to the copper centers, while two molecules of TBZ are bounded to copper explaining the higher IMZ uptake capacity for the Mt-Cu material. Graphical abstract.

Electron-transfer-mediated synthesis of phenanthridines by intramolecular arylation of anions from N-(ortho-halobenzyl)arylamines: regiochemical and mechanistic analysis.

The synthesis of a series of substituted phenanthridines by photostimulated C-C cyclization of anions from N-(ortho-halobenzyl)arylamines has been found to proceed in very good to excellent yields (79-95%) in liquid ammonia and in DMSO. The N-(ortho-halobenzyl)arylamines are obtained in good to very good isolated yields (44-85%) by nucleophilic substitution of ortho-halobenzylchlorides with different arylamines. The reaction of the anions of a diverse set of N-(ortho-halobenzyl)arylamines was studied, and the methodology was extended to the synthesis of trispheridine, a natural product, in very good yield. In order to explain the regiochemical outcome of these reactions, a theoretical analysis was performed with DFT methods and the B3LYP functional.