Kinetics and its accompanying thermodynamics studies on simultaneous complexation of heterobimetallic neodymium (III) with zinc (II) and l-tryptophan in aquated DMF using 4f–4f absorption spectra

Abstract

The 4f–4f absorption spectra of the simultaneous heterobimetallic complexation of trivalent neodymium ion with l-tryptophan and divalent zinc ion in aquated DMF (50%, v/v) at pH 6.0 was recorded at the time interval of 1h. From the observed absorption spectra, the values of intensity parameters such as oscillator strength (P) and Judd–Ofelt intensity (Tλ) parameters, kinetics and thermodynamics parameters were evaluated. The rate constant increases with an increase in the temperature along with the oscillator strengths and Judd–Ofelt intensity parameters. The positive values of the change in the standard enthalpy (ΔH°) and entropy (ΔS°) indicate that the complexation is endothermic. The negative values of the change in the standard free energy (ΔG°) in the range from 293.15K to 308.15K, indicate that the reaction occurs spontaneously and hence the formation of heterobimetallic complex in the solution is favored kinetically and thermodynamically.