Abstract
The interaction of N′-[(1E)-1-phenylethylidene]isonicotinohydrazide (PHeH) with trivalent Pr, Nd, Gd, Tb, and Ho ions was studied with spectroscopic and potentiometric techniques. Photoluminescence studies of Tb3+ and PHeH in ethanol and in solid Tb3+-PHeH complex reveal that PHeH has no sensitizing effect on Tb3+ luminescence. The absorption spectral bands of PHeH under different conditions and that of Nd3+- PHeH at different molar ratios were investigated. Potentiometric titrations of 1:4 Ln/PHeH molar ratio carried out at different temperature at a constant ionic strength of I=0.1mol·dm−3 KNO3 in aqueous-dioxane medium reveal the moderate thermodynamic stability constants of the complex formation equilibria which follow the order: Pr<Nd<Gd<Tb<Ho. The thermodynamic parameters (ΔG, ΔH, and ΔS) of protonation and complexation reactions are all negative suggesting the spontaneous, exothermic, of unfavorable entropy and enthalpy-driven reactions. Actual synthesis and characterization of Tb3+-PHeH complex, confirmed the veracity of the complex formation equilibria. Finally, the information accrued from the studies is used in the structural elucidation of the complexes.
Published Version
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