Synthesis of three new branched octadentate (N8) Schiff Base and competitive Lithium-7 NMR study of the stoichiometry and stability constant of Mn2+, Zn2+ and Cd2+ complexes in acetonitrile - [(BMIM)(PF6)] mixture

Three new branched hexadentate amines, have been synthesized. Condensation with picolinaldehyde in methanol leads to produce three new Schiff base, with two 2-pyridylmethyl pendant arms. Li-7 NMR spectroscopy was used to investigation the stability and stoichiometry information of a Li+ complex with three symmetrical branched Schiff base (Sc.B.(1)), (Sc.B.(2)) and (Sc.B.(3)) in 0-100, 25-75, 50-50 and 75-25 w/w% acetonitrile - [(BMIM)(PE6)] ionic liquid mixture solution. A competitive Li-7 NMR manner was also used to probe the complexation of Schiff bases with Mn2+, Zn2+ and Cd2+ ions in the same solvent systems. The stability constants of the resulting complexes were estimated from computer fitting of the mole ratio information to an equation that relates the observed chemical shifts to the stable constant. There is a reverse relevance of the complex stability and the amount of ionic liquid in the solvent mixture. In of the all experimented solvent mixture, the stability of the resulted 1:1 complexes were found to change in the order M-Sc.B.(1)>M-Sc.B.(2)>M-Sc.B.(3) and Cd2+> Mn2+> Zn2+. (C) 2019 Elsevier B.V. All rights reserved.