Determination of Stability Constants of 2-Hydroxy-1-Naphthalidene-p-N-Dimethylaminoaniline Complexes with Pr3+, Nd3+, Gd3+ and Dy3+

Department of Chemistry, Ramnarain Ruia College, Bombay-400 019

Manuscript received 21 January 1979, revised 29 January 1980, accepted 19 May 1980

Potentiometric studies have been carried out on metal complexes of Pr³⁺, Nd³⁺, Gd³⁺ and Dy³⁺, with 2-hydroxy-1-naphthalidene-p-N-dimethylaminoaniline. The dissociation constants (pK₁ and pK₂) of the reagent and the formation constants of its metal complexes have been determined by Bjerrum's method at 25 ± 0.1 o and at ionic strength 0.1 M in 75 : 25 per cent (v/v) dioxan-water medium. The order of stability constants of the chelates is found to be Dy³⁺>Pr³⁺>Gd³⁺>Nd³⁺. The validity of Born's relation was examined by studying the plot of z•tr vs log K values of the rare earth complexes of the ligand,