Aminopolycarboxylate zinc(II) complexes with 1,10-phenanthroline and 2,2′-bipyridyl: kinetic studies in the surfactants solutions systems

Abstract

Aminopolycarboxylate zinc(II) complexes with 1,10-phenanthroline and 2,2′-bipyridyl {[Zn(IDA)(H2O)2], [Zn(IDA)(bipy)(H2O)]·2H2O and [Zn(IDA)(phen)(H2O)]·2H2O} were synthesized. In order to confirm the composition and purity of the synthesized complex compounds, elemental analysis was used. Next, the kinetics of the substitution reaction of two water molecules in the zinc(II) iminodiacetate complex for 1,10-phenanthroline and 2,2′-bipyridyl in two surfactant solvents: CTAB and Triton X-100 were investigated. The kinetic studies were carried out using the stopped flow method. The kinetic research were carried out at 3 different temperatures: 288.15, 293.15 and 298.15 K and at different molar concentrations of the complex compound [Zn(IDA)(H2O)2]: 1 mM; 0.75 mM, 0.5 mM and 0.25 mM and at a constant molar concentration of ligands: i.e. 1,10-phenanthroline and 2,2′-bipyridyl, were 0.05 mM. Changes in absorbance during the kinetic run of the tested reactions were measured at a wavelength of 260 nm. Thanks to the conducted kinetic studies, the order of the reaction was determined, and the observable rate constants of the reaction rates of the substitution of two aqua molecules into the N-donor ligand were determined by the stopped—flow method using the Glint program. In the next step the thermodynamic parameters of complexes: {[Zn(IDA)(H2O)2], [Zn(IDA)(bipy)(H2O)]·2H2O and [Zn(IDA)(phen)(H2O)]·2H2O} in aqueous solutions by use potentiometric titrations were determined. The Hyperquad2018 program was used for determining of stability constants. In addition, the stoichiometry of complexes of zinc(II) with N-heterocyclic ligands in aqueous solutions was determined using the conductometric titrations.