Comparative 4f-4f Spectral Analysis of Simultaneous Complexation of Pr(III) with L-Tryptophan in Presence and Absence of Ca2+ and Zn2+ Ions in Aqueous Medium: Energy, Intensity and Kinetic Studies

Abstract

The spectral analysis of the complexation of praseodymium (Pr³⁺) with L-tryptophan in various aqueous solvent applying a quantitative probe of 4f-4f transition spectra. The study is carried out by calculating various energy interaction parameters such as the nephelauxetic effect (β), percent covalency (δ), bonding parameter (b^1/2), Slater-Condon (F_k) and intensity parameters like oscillator strength (P) and intensity of Judd-Ofelt parameters T_λ (λ = 2, 4, 6). The paramagnetic behaviour of Pr³⁺ shows ³H₄→¹D₂, ³H₄→³P₀, ³H₄→³P₁, ³H₄→³P₂ types of specific 4f-4f absorption bands and are observed at the visible reason of 427-610 nm. The intensities of 4f-4f transition bands rise on the addition of Ca²⁺ and Zn²⁺ ions toward the complexation of praseodymium (Pr³⁺):Try and extended result in the case of Ca²⁺ ion compared to the Zn²⁺ ion due to increase in the interaction between ligand and 4f orbital of metal ions. These bands on immediate minor’s coordination change around praseodymium (Pr³⁺) found to be highly sensitive due to the formation of heterobimetallic complex between L-tryptophan (Try) with Pr³⁺ in the existence of Zn²⁺ and Ca²⁺ ions. The complexation of Try with Pr³⁺ in the presence of Zn²⁺ and Ca²⁺ ions are monitors simultaneously from the sensitivity of the bands using energy parameters and oscillator strength. The rate of heterobimetallic complexation of both Zn²⁺ and Ca²⁺ ions was calculated from the 4f-4f transition at different temperatures. The thermodynamic parameters and activation energy calculated from the rate constants from different temperatures are more favourable in case of Try form complex with Pr³⁺ in the presence of Ca²⁺ ion as compared to Zn²⁺ ion.